Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

3 files changed, 3059 insertions, 0 deletions

diff --git a/vendor/object/src/write/elf/mod.rs b/vendor/object/src/write/elf/mod.rs
new file mode 100644
index 0000000..3a4f371
--- /dev/null
+++ b/vendor/object/src/write/elf/mod.rs
@@ -0,0 +1,9 @@
+//! Support for writing ELF files.
+//!
+//! Provides [`Writer`] for low level writing of ELF files.
+//! This is also used to provide ELF support for [`write::Object`](crate::write::Object).
+
+mod object;
+
+mod writer;
+pub use writer::*;
diff --git a/vendor/object/src/write/elf/object.rs b/vendor/object/src/write/elf/object.rs
new file mode 100644
index 0000000..5d7a93e
--- /dev/null
+++ b/vendor/object/src/write/elf/object.rs
@@ -0,0 +1,907 @@
+use alloc::vec::Vec;
+
+use crate::write::elf::writer::*;
+use crate::write::string::StringId;
+use crate::write::*;
+use crate::AddressSize;
+use crate::{elf, pod};
+
+#[derive(Clone, Copy)]
+struct ComdatOffsets {
+    offset: usize,
+    str_id: StringId,
+}
+
+#[derive(Clone, Copy)]
+struct SectionOffsets {
+    index: SectionIndex,
+    offset: usize,
+    str_id: StringId,
+    reloc_offset: usize,
+    reloc_str_id: Option<StringId>,
+}
+
+#[derive(Default, Clone, Copy)]
+struct SymbolOffsets {
+    index: SymbolIndex,
+    str_id: Option<StringId>,
+}
+
+// Public methods.
+impl<'a> Object<'a> {
+    /// Add a property with a u32 value to the ELF ".note.gnu.property" section.
+    ///
+    /// Requires `feature = "elf"`.
+    pub fn add_elf_gnu_property_u32(&mut self, property: u32, value: u32) {
+        if self.format != BinaryFormat::Elf {
+            return;
+        }
+
+        let align = if self.elf_is_64() { 8 } else { 4 };
+        let mut data = Vec::with_capacity(32);
+        let n_name = b"GNU\0";
+        data.extend_from_slice(pod::bytes_of(&elf::NoteHeader32 {
+            n_namesz: U32::new(self.endian, n_name.len() as u32),
+            n_descsz: U32::new(self.endian, util::align(3 * 4, align) as u32),
+            n_type: U32::new(self.endian, elf::NT_GNU_PROPERTY_TYPE_0),
+        }));
+        data.extend_from_slice(n_name);
+        // This happens to already be aligned correctly.
+        debug_assert_eq!(util::align(data.len(), align), data.len());
+        data.extend_from_slice(pod::bytes_of(&U32::new(self.endian, property)));
+        // Value size
+        data.extend_from_slice(pod::bytes_of(&U32::new(self.endian, 4)));
+        data.extend_from_slice(pod::bytes_of(&U32::new(self.endian, value)));
+        util::write_align(&mut data, align);
+
+        let section = self.section_id(StandardSection::GnuProperty);
+        self.append_section_data(section, &data, align as u64);
+    }
+}
+
+// Private methods.
+impl<'a> Object<'a> {
+    pub(crate) fn elf_section_info(
+        &self,
+        section: StandardSection,
+    ) -> (&'static [u8], &'static [u8], SectionKind, SectionFlags) {
+        match section {
+            StandardSection::Text => (&[], &b".text"[..], SectionKind::Text, SectionFlags::None),
+            StandardSection::Data => (&[], &b".data"[..], SectionKind::Data, SectionFlags::None),
+            StandardSection::ReadOnlyData | StandardSection::ReadOnlyString => (
+                &[],
+                &b".rodata"[..],
+                SectionKind::ReadOnlyData,
+                SectionFlags::None,
+            ),
+            StandardSection::ReadOnlyDataWithRel => (
+                &[],
+                b".data.rel.ro",
+                SectionKind::ReadOnlyDataWithRel,
+                SectionFlags::None,
+            ),
+            StandardSection::UninitializedData => (
+                &[],
+                &b".bss"[..],
+                SectionKind::UninitializedData,
+                SectionFlags::None,
+            ),
+            StandardSection::Tls => (&[], &b".tdata"[..], SectionKind::Tls, SectionFlags::None),
+            StandardSection::UninitializedTls => (
+                &[],
+                &b".tbss"[..],
+                SectionKind::UninitializedTls,
+                SectionFlags::None,
+            ),
+            StandardSection::TlsVariables => {
+                // Unsupported section.
+                (&[], &[], SectionKind::TlsVariables, SectionFlags::None)
+            }
+            StandardSection::Common => {
+                // Unsupported section.
+                (&[], &[], SectionKind::Common, SectionFlags::None)
+            }
+            StandardSection::GnuProperty => (
+                &[],
+                &b".note.gnu.property"[..],
+                SectionKind::Note,
+                SectionFlags::Elf {
+                    sh_flags: u64::from(elf::SHF_ALLOC),
+                },
+            ),
+        }
+    }
+
+    pub(crate) fn elf_subsection_name(&self, section: &[u8], value: &[u8]) -> Vec<u8> {
+        let mut name = section.to_vec();
+        name.push(b'.');
+        name.extend_from_slice(value);
+        name
+    }
+
+    fn elf_has_relocation_addend(&self) -> Result<bool> {
+        Ok(match self.architecture {
+            Architecture::Aarch64 => true,
+            Architecture::Aarch64_Ilp32 => true,
+            Architecture::Arm => false,
+            Architecture::Avr => true,
+            Architecture::Bpf => false,
+            Architecture::Csky => true,
+            Architecture::I386 => false,
+            Architecture::X86_64 => true,
+            Architecture::X86_64_X32 => true,
+            Architecture::Hexagon => true,
+            Architecture::LoongArch64 => true,
+            Architecture::Mips => false,
+            Architecture::Mips64 => true,
+            Architecture::Msp430 => true,
+            Architecture::PowerPc => true,
+            Architecture::PowerPc64 => true,
+            Architecture::Riscv64 => true,
+            Architecture::Riscv32 => true,
+            Architecture::S390x => true,
+            Architecture::Sbf => false,
+            Architecture::Sharc => true,
+            Architecture::Sparc64 => true,
+            Architecture::Xtensa => true,
+            _ => {
+                return Err(Error(format!(
+                    "unimplemented architecture {:?}",
+                    self.architecture
+                )));
+            }
+        })
+    }
+
+    pub(crate) fn elf_fixup_relocation(&mut self, relocation: &mut Relocation) -> Result<i64> {
+        // Determine whether the addend is stored in the relocation or the data.
+        if self.elf_has_relocation_addend()? {
+            Ok(0)
+        } else {
+            let constant = relocation.addend;
+            relocation.addend = 0;
+            Ok(constant)
+        }
+    }
+
+    pub(crate) fn elf_is_64(&self) -> bool {
+        match self.architecture.address_size().unwrap() {
+            AddressSize::U8 | AddressSize::U16 | AddressSize::U32 => false,
+            AddressSize::U64 => true,
+        }
+    }
+
+    pub(crate) fn elf_write(&self, buffer: &mut dyn WritableBuffer) -> Result<()> {
+        // Create reloc section header names so we can reference them.
+        let is_rela = self.elf_has_relocation_addend()?;
+        let reloc_names: Vec<_> = self
+            .sections
+            .iter()
+            .map(|section| {
+                let mut reloc_name = Vec::with_capacity(
+                    if is_rela { ".rela".len() } else { ".rel".len() } + section.name.len(),
+                );
+                if !section.relocations.is_empty() {
+                    reloc_name.extend_from_slice(if is_rela {
+                        &b".rela"[..]
+                    } else {
+                        &b".rel"[..]
+                    });
+                    reloc_name.extend_from_slice(&section.name);
+                }
+                reloc_name
+            })
+            .collect();
+
+        // Start calculating offsets of everything.
+        let mut writer = Writer::new(self.endian, self.elf_is_64(), buffer);
+        writer.reserve_file_header();
+
+        // Calculate size of section data.
+        let mut comdat_offsets = Vec::with_capacity(self.comdats.len());
+        for comdat in &self.comdats {
+            if comdat.kind != ComdatKind::Any {
+                return Err(Error(format!(
+                    "unsupported COMDAT symbol `{}` kind {:?}",
+                    self.symbols[comdat.symbol.0].name().unwrap_or(""),
+                    comdat.kind
+                )));
+            }
+
+            writer.reserve_section_index();
+            let offset = writer.reserve_comdat(comdat.sections.len());
+            let str_id = writer.add_section_name(b".group");
+            comdat_offsets.push(ComdatOffsets { offset, str_id });
+        }
+        let mut section_offsets = Vec::with_capacity(self.sections.len());
+        for (section, reloc_name) in self.sections.iter().zip(reloc_names.iter()) {
+            let index = writer.reserve_section_index();
+            let offset = writer.reserve(section.data.len(), section.align as usize);
+            let str_id = writer.add_section_name(&section.name);
+            let mut reloc_str_id = None;
+            if !section.relocations.is_empty() {
+                writer.reserve_section_index();
+                reloc_str_id = Some(writer.add_section_name(reloc_name));
+            }
+            section_offsets.push(SectionOffsets {
+                index,
+                offset,
+                str_id,
+                // Relocation data is reserved later.
+                reloc_offset: 0,
+                reloc_str_id,
+            });
+        }
+
+        // Calculate index of symbols and add symbol strings to strtab.
+        let mut symbol_offsets = vec![SymbolOffsets::default(); self.symbols.len()];
+        writer.reserve_null_symbol_index();
+        // Local symbols must come before global.
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if symbol.is_local() {
+                let section_index = symbol.section.id().map(|s| section_offsets[s.0].index);
+                symbol_offsets[index].index = writer.reserve_symbol_index(section_index);
+            }
+        }
+        let symtab_num_local = writer.symbol_count();
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if !symbol.is_local() {
+                let section_index = symbol.section.id().map(|s| section_offsets[s.0].index);
+                symbol_offsets[index].index = writer.reserve_symbol_index(section_index);
+            }
+        }
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if symbol.kind != SymbolKind::Section && !symbol.name.is_empty() {
+                symbol_offsets[index].str_id = Some(writer.add_string(&symbol.name));
+            }
+        }
+
+        // Calculate size of symbols.
+        writer.reserve_symtab_section_index();
+        writer.reserve_symtab();
+        if writer.symtab_shndx_needed() {
+            writer.reserve_symtab_shndx_section_index();
+        }
+        writer.reserve_symtab_shndx();
+        writer.reserve_strtab_section_index();
+        writer.reserve_strtab();
+
+        // Calculate size of relocations.
+        for (index, section) in self.sections.iter().enumerate() {
+            let count = section.relocations.len();
+            if count != 0 {
+                section_offsets[index].reloc_offset = writer.reserve_relocations(count, is_rela);
+            }
+        }
+
+        // Calculate size of section headers.
+        writer.reserve_shstrtab_section_index();
+        writer.reserve_shstrtab();
+        writer.reserve_section_headers();
+
+        // Start writing.
+        let e_type = elf::ET_REL;
+        let e_machine = match (self.architecture, self.sub_architecture) {
+            (Architecture::Aarch64, None) => elf::EM_AARCH64,
+            (Architecture::Aarch64_Ilp32, None) => elf::EM_AARCH64,
+            (Architecture::Arm, None) => elf::EM_ARM,
+            (Architecture::Avr, None) => elf::EM_AVR,
+            (Architecture::Bpf, None) => elf::EM_BPF,
+            (Architecture::Csky, None) => elf::EM_CSKY,
+            (Architecture::I386, None) => elf::EM_386,
+            (Architecture::X86_64, None) => elf::EM_X86_64,
+            (Architecture::X86_64_X32, None) => elf::EM_X86_64,
+            (Architecture::Hexagon, None) => elf::EM_HEXAGON,
+            (Architecture::LoongArch64, None) => elf::EM_LOONGARCH,
+            (Architecture::Mips, None) => elf::EM_MIPS,
+            (Architecture::Mips64, None) => elf::EM_MIPS,
+            (Architecture::Msp430, None) => elf::EM_MSP430,
+            (Architecture::PowerPc, None) => elf::EM_PPC,
+            (Architecture::PowerPc64, None) => elf::EM_PPC64,
+            (Architecture::Riscv32, None) => elf::EM_RISCV,
+            (Architecture::Riscv64, None) => elf::EM_RISCV,
+            (Architecture::S390x, None) => elf::EM_S390,
+            (Architecture::Sbf, None) => elf::EM_SBF,
+            (Architecture::Sharc, None) => elf::EM_SHARC,
+            (Architecture::Sparc64, None) => elf::EM_SPARCV9,
+            (Architecture::Xtensa, None) => elf::EM_XTENSA,
+            _ => {
+                return Err(Error(format!(
+                    "unimplemented architecture {:?} with sub-architecture {:?}",
+                    self.architecture, self.sub_architecture
+                )));
+            }
+        };
+        let (os_abi, abi_version, e_flags) = if let FileFlags::Elf {
+            os_abi,
+            abi_version,
+            e_flags,
+        } = self.flags
+        {
+            (os_abi, abi_version, e_flags)
+        } else {
+            (elf::ELFOSABI_NONE, 0, 0)
+        };
+        writer.write_file_header(&FileHeader {
+            os_abi,
+            abi_version,
+            e_type,
+            e_machine,
+            e_entry: 0,
+            e_flags,
+        })?;
+
+        // Write section data.
+        for comdat in &self.comdats {
+            writer.write_comdat_header();
+            for section in &comdat.sections {
+                writer.write_comdat_entry(section_offsets[section.0].index);
+            }
+        }
+        for (index, section) in self.sections.iter().enumerate() {
+            writer.write_align(section.align as usize);
+            debug_assert_eq!(section_offsets[index].offset, writer.len());
+            writer.write(&section.data);
+        }
+
+        // Write symbols.
+        writer.write_null_symbol();
+        let mut write_symbol = |index: usize, symbol: &Symbol| -> Result<()> {
+            let st_info = if let SymbolFlags::Elf { st_info, .. } = symbol.flags {
+                st_info
+            } else {
+                let st_type = match symbol.kind {
+                    SymbolKind::Null => elf::STT_NOTYPE,
+                    SymbolKind::Text => {
+                        if symbol.is_undefined() {
+                            elf::STT_NOTYPE
+                        } else {
+                            elf::STT_FUNC
+                        }
+                    }
+                    SymbolKind::Data => {
+                        if symbol.is_undefined() {
+                            elf::STT_NOTYPE
+                        } else if symbol.is_common() {
+                            elf::STT_COMMON
+                        } else {
+                            elf::STT_OBJECT
+                        }
+                    }
+                    SymbolKind::Section => elf::STT_SECTION,
+                    SymbolKind::File => elf::STT_FILE,
+                    SymbolKind::Tls => elf::STT_TLS,
+                    SymbolKind::Label => elf::STT_NOTYPE,
+                    SymbolKind::Unknown => {
+                        if symbol.is_undefined() {
+                            elf::STT_NOTYPE
+                        } else {
+                            return Err(Error(format!(
+                                "unimplemented symbol `{}` kind {:?}",
+                                symbol.name().unwrap_or(""),
+                                symbol.kind
+                            )));
+                        }
+                    }
+                };
+                let st_bind = if symbol.weak {
+                    elf::STB_WEAK
+                } else if symbol.is_undefined() {
+                    elf::STB_GLOBAL
+                } else if symbol.is_local() {
+                    elf::STB_LOCAL
+                } else {
+                    elf::STB_GLOBAL
+                };
+                (st_bind << 4) + st_type
+            };
+            let st_other = if let SymbolFlags::Elf { st_other, .. } = symbol.flags {
+                st_other
+            } else if symbol.scope == SymbolScope::Linkage {
+                elf::STV_HIDDEN
+            } else {
+                elf::STV_DEFAULT
+            };
+            let (st_shndx, section) = match symbol.section {
+                SymbolSection::None => {
+                    debug_assert_eq!(symbol.kind, SymbolKind::File);
+                    (elf::SHN_ABS, None)
+                }
+                SymbolSection::Undefined => (elf::SHN_UNDEF, None),
+                SymbolSection::Absolute => (elf::SHN_ABS, None),
+                SymbolSection::Common => (elf::SHN_COMMON, None),
+                SymbolSection::Section(id) => (0, Some(section_offsets[id.0].index)),
+            };
+            writer.write_symbol(&Sym {
+                name: symbol_offsets[index].str_id,
+                section,
+                st_info,
+                st_other,
+                st_shndx,
+                st_value: symbol.value,
+                st_size: symbol.size,
+            });
+            Ok(())
+        };
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if symbol.is_local() {
+                write_symbol(index, symbol)?;
+            }
+        }
+        for (index, symbol) in self.symbols.iter().enumerate() {
+            if !symbol.is_local() {
+                write_symbol(index, symbol)?;
+            }
+        }
+        writer.write_symtab_shndx();
+        writer.write_strtab();
+
+        // Write relocations.
+        for (index, section) in self.sections.iter().enumerate() {
+            if !section.relocations.is_empty() {
+                writer.write_align_relocation();
+                debug_assert_eq!(section_offsets[index].reloc_offset, writer.len());
+                for reloc in &section.relocations {
+                    let r_type = match self.architecture {
+                        Architecture::Aarch64 => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 64) => {
+                                elf::R_AARCH64_ABS64
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 32) => {
+                                elf::R_AARCH64_ABS32
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 16) => {
+                                elf::R_AARCH64_ABS16
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 64) => {
+                                elf::R_AARCH64_PREL64
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 32) => {
+                                elf::R_AARCH64_PREL32
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 16) => {
+                                elf::R_AARCH64_PREL16
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::AArch64Call, 26)
+                            | (RelocationKind::PltRelative, RelocationEncoding::AArch64Call, 26) => {
+                                elf::R_AARCH64_CALL26
+                            }
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Aarch64_Ilp32 => {
+                            match (reloc.kind, reloc.encoding, reloc.size) {
+                                (RelocationKind::Absolute, RelocationEncoding::Generic, 32) => {
+                                    elf::R_AARCH64_P32_ABS32
+                                }
+                                (RelocationKind::Elf(x), _, _) => x,
+                                _ => {
+                                    return Err(Error(format!(
+                                        "unimplemented relocation {:?}",
+                                        reloc
+                                    )));
+                                }
+                            }
+                        }
+                        Architecture::Arm => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_ARM_ABS32,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Avr => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_AVR_32,
+                            (RelocationKind::Absolute, _, 16) => elf::R_AVR_16,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Bpf => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 64) => elf::R_BPF_64_64,
+                            (RelocationKind::Absolute, _, 32) => elf::R_BPF_64_32,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Csky => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_CKCORE_ADDR32,
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 32) => {
+                                elf::R_CKCORE_PCREL32
+                            }
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::I386 => match (reloc.kind, reloc.size) {
+                            (RelocationKind::Absolute, 32) => elf::R_386_32,
+                            (RelocationKind::Relative, 32) => elf::R_386_PC32,
+                            (RelocationKind::Got, 32) => elf::R_386_GOT32,
+                            (RelocationKind::PltRelative, 32) => elf::R_386_PLT32,
+                            (RelocationKind::GotBaseOffset, 32) => elf::R_386_GOTOFF,
+                            (RelocationKind::GotBaseRelative, 32) => elf::R_386_GOTPC,
+                            (RelocationKind::Absolute, 16) => elf::R_386_16,
+                            (RelocationKind::Relative, 16) => elf::R_386_PC16,
+                            (RelocationKind::Absolute, 8) => elf::R_386_8,
+                            (RelocationKind::Relative, 8) => elf::R_386_PC8,
+                            (RelocationKind::Elf(x), _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::X86_64 | Architecture::X86_64_X32 => {
+                            match (reloc.kind, reloc.encoding, reloc.size) {
+                                (RelocationKind::Absolute, RelocationEncoding::Generic, 64) => {
+                                    elf::R_X86_64_64
+                                }
+                                (RelocationKind::Relative, RelocationEncoding::X86Branch, 32) => {
+                                    elf::R_X86_64_PLT32
+                                }
+                                (RelocationKind::Relative, _, 32) => elf::R_X86_64_PC32,
+                                (RelocationKind::Got, _, 32) => elf::R_X86_64_GOT32,
+                                (RelocationKind::PltRelative, _, 32) => elf::R_X86_64_PLT32,
+                                (RelocationKind::GotRelative, _, 32) => elf::R_X86_64_GOTPCREL,
+                                (RelocationKind::Absolute, RelocationEncoding::Generic, 32) => {
+                                    elf::R_X86_64_32
+                                }
+                                (RelocationKind::Absolute, RelocationEncoding::X86Signed, 32) => {
+                                    elf::R_X86_64_32S
+                                }
+                                (RelocationKind::Absolute, _, 16) => elf::R_X86_64_16,
+                                (RelocationKind::Relative, _, 16) => elf::R_X86_64_PC16,
+                                (RelocationKind::Absolute, _, 8) => elf::R_X86_64_8,
+                                (RelocationKind::Relative, _, 8) => elf::R_X86_64_PC8,
+                                (RelocationKind::Elf(x), _, _) => x,
+                                _ => {
+                                    return Err(Error(format!(
+                                        "unimplemented relocation {:?}",
+                                        reloc
+                                    )));
+                                }
+                            }
+                        }
+                        Architecture::Hexagon => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_HEX_32,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::LoongArch64 => match (reloc.kind, reloc.encoding, reloc.size)
+                        {
+                            (RelocationKind::Absolute, _, 32) => elf::R_LARCH_32,
+                            (RelocationKind::Absolute, _, 64) => elf::R_LARCH_64,
+                            (RelocationKind::Relative, _, 32) => elf::R_LARCH_32_PCREL,
+                            (RelocationKind::Relative, _, 64) => elf::R_LARCH_64_PCREL,
+                            (RelocationKind::Relative, RelocationEncoding::LoongArchBranch, 16)
+                            | (
+                                RelocationKind::PltRelative,
+                                RelocationEncoding::LoongArchBranch,
+                                16,
+                            ) => elf::R_LARCH_B16,
+                            (RelocationKind::Relative, RelocationEncoding::LoongArchBranch, 21)
+                            | (
+                                RelocationKind::PltRelative,
+                                RelocationEncoding::LoongArchBranch,
+                                21,
+                            ) => elf::R_LARCH_B21,
+                            (RelocationKind::Relative, RelocationEncoding::LoongArchBranch, 26)
+                            | (
+                                RelocationKind::PltRelative,
+                                RelocationEncoding::LoongArchBranch,
+                                26,
+                            ) => elf::R_LARCH_B26,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Mips | Architecture::Mips64 => {
+                            match (reloc.kind, reloc.encoding, reloc.size) {
+                                (RelocationKind::Absolute, _, 16) => elf::R_MIPS_16,
+                                (RelocationKind::Absolute, _, 32) => elf::R_MIPS_32,
+                                (RelocationKind::Absolute, _, 64) => elf::R_MIPS_64,
+                                (RelocationKind::Elf(x), _, _) => x,
+                                _ => {
+                                    return Err(Error(format!(
+                                        "unimplemented relocation {:?}",
+                                        reloc
+                                    )));
+                                }
+                            }
+                        }
+                        Architecture::Msp430 => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_MSP430_32,
+                            (RelocationKind::Absolute, _, 16) => elf::R_MSP430_16_BYTE,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::PowerPc => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_PPC_ADDR32,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::PowerPc64 => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_PPC64_ADDR32,
+                            (RelocationKind::Absolute, _, 64) => elf::R_PPC64_ADDR64,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Riscv32 | Architecture::Riscv64 => {
+                            match (reloc.kind, reloc.encoding, reloc.size) {
+                                (RelocationKind::Absolute, _, 32) => elf::R_RISCV_32,
+                                (RelocationKind::Absolute, _, 64) => elf::R_RISCV_64,
+                                (RelocationKind::Relative, RelocationEncoding::Generic, 32) => {
+                                    elf::R_RISCV_32_PCREL
+                                }
+                                (RelocationKind::Elf(x), _, _) => x,
+                                _ => {
+                                    return Err(Error(format!(
+                                        "unimplemented relocation {:?}",
+                                        reloc
+                                    )));
+                                }
+                            }
+                        }
+                        Architecture::S390x => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 8) => {
+                                elf::R_390_8
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 16) => {
+                                elf::R_390_16
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 32) => {
+                                elf::R_390_32
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 64) => {
+                                elf::R_390_64
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 16) => {
+                                elf::R_390_PC16
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 32) => {
+                                elf::R_390_PC32
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 64) => {
+                                elf::R_390_PC64
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::S390xDbl, 16) => {
+                                elf::R_390_PC16DBL
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::S390xDbl, 32) => {
+                                elf::R_390_PC32DBL
+                            }
+                            (RelocationKind::PltRelative, RelocationEncoding::S390xDbl, 16) => {
+                                elf::R_390_PLT16DBL
+                            }
+                            (RelocationKind::PltRelative, RelocationEncoding::S390xDbl, 32) => {
+                                elf::R_390_PLT32DBL
+                            }
+                            (RelocationKind::Got, RelocationEncoding::Generic, 16) => {
+                                elf::R_390_GOT16
+                            }
+                            (RelocationKind::Got, RelocationEncoding::Generic, 32) => {
+                                elf::R_390_GOT32
+                            }
+                            (RelocationKind::Got, RelocationEncoding::Generic, 64) => {
+                                elf::R_390_GOT64
+                            }
+                            (RelocationKind::GotRelative, RelocationEncoding::S390xDbl, 32) => {
+                                elf::R_390_GOTENT
+                            }
+                            (RelocationKind::GotBaseOffset, RelocationEncoding::Generic, 16) => {
+                                elf::R_390_GOTOFF16
+                            }
+                            (RelocationKind::GotBaseOffset, RelocationEncoding::Generic, 32) => {
+                                elf::R_390_GOTOFF32
+                            }
+                            (RelocationKind::GotBaseOffset, RelocationEncoding::Generic, 64) => {
+                                elf::R_390_GOTOFF64
+                            }
+                            (RelocationKind::GotBaseRelative, RelocationEncoding::Generic, 64) => {
+                                elf::R_390_GOTPC
+                            }
+                            (RelocationKind::GotBaseRelative, RelocationEncoding::S390xDbl, 32) => {
+                                elf::R_390_GOTPCDBL
+                            }
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Sbf => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 64) => elf::R_SBF_64_64,
+                            (RelocationKind::Absolute, _, 32) => elf::R_SBF_64_32,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Sharc => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, RelocationEncoding::SharcTypeA, 32) => {
+                                elf::R_SHARC_ADDR32_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 32) => {
+                                elf::R_SHARC_ADDR_VAR_V3
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::SharcTypeA, 24) => {
+                                elf::R_SHARC_PCRLONG_V3
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::SharcTypeA, 6) => {
+                                elf::R_SHARC_PCRSHORT_V3
+                            }
+                            (RelocationKind::Relative, RelocationEncoding::SharcTypeB, 6) => {
+                                elf::R_SHARC_PCRSHORT_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::Generic, 16) => {
+                                elf::R_SHARC_ADDR_VAR16_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::SharcTypeA, 16) => {
+                                elf::R_SHARC_DATA16_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::SharcTypeB, 16) => {
+                                elf::R_SHARC_DATA16_VISA_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::SharcTypeA, 24) => {
+                                elf::R_SHARC_ADDR24_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::SharcTypeA, 6) => {
+                                elf::R_SHARC_DATA6_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::SharcTypeB, 6) => {
+                                elf::R_SHARC_DATA6_VISA_V3
+                            }
+                            (RelocationKind::Absolute, RelocationEncoding::SharcTypeB, 7) => {
+                                elf::R_SHARC_DATA7_VISA_V3
+                            }
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Sparc64 => match (reloc.kind, reloc.encoding, reloc.size) {
+                            // TODO: use R_SPARC_32/R_SPARC_64 if aligned.
+                            (RelocationKind::Absolute, _, 32) => elf::R_SPARC_UA32,
+                            (RelocationKind::Absolute, _, 64) => elf::R_SPARC_UA64,
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        Architecture::Xtensa => match (reloc.kind, reloc.encoding, reloc.size) {
+                            (RelocationKind::Absolute, _, 32) => elf::R_XTENSA_32,
+                            (RelocationKind::Relative, RelocationEncoding::Generic, 32) => {
+                                elf::R_XTENSA_32_PCREL
+                            }
+                            (RelocationKind::Elf(x), _, _) => x,
+                            _ => {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        },
+                        _ => {
+                            if let RelocationKind::Elf(x) = reloc.kind {
+                                x
+                            } else {
+                                return Err(Error(format!("unimplemented relocation {:?}", reloc)));
+                            }
+                        }
+                    };
+                    let r_sym = symbol_offsets[reloc.symbol.0].index.0;
+                    writer.write_relocation(
+                        is_rela,
+                        &Rel {
+                            r_offset: reloc.offset,
+                            r_sym,
+                            r_type,
+                            r_addend: reloc.addend,
+                        },
+                    );
+                }
+            }
+        }
+
+        writer.write_shstrtab();
+
+        // Write section headers.
+        writer.write_null_section_header();
+
+        let symtab_index = writer.symtab_index();
+        for (comdat, comdat_offset) in self.comdats.iter().zip(comdat_offsets.iter()) {
+            writer.write_comdat_section_header(
+                comdat_offset.str_id,
+                symtab_index,
+                symbol_offsets[comdat.symbol.0].index,
+                comdat_offset.offset,
+                comdat.sections.len(),
+            );
+        }
+        for (index, section) in self.sections.iter().enumerate() {
+            let sh_type = match section.kind {
+                SectionKind::UninitializedData | SectionKind::UninitializedTls => elf::SHT_NOBITS,
+                SectionKind::Note => elf::SHT_NOTE,
+                SectionKind::Elf(sh_type) => sh_type,
+                _ => elf::SHT_PROGBITS,
+            };
+            let sh_flags = if let SectionFlags::Elf { sh_flags } = section.flags {
+                sh_flags
+            } else {
+                match section.kind {
+                    SectionKind::Text => elf::SHF_ALLOC | elf::SHF_EXECINSTR,
+                    SectionKind::Data | SectionKind::ReadOnlyDataWithRel => {
+                        elf::SHF_ALLOC | elf::SHF_WRITE
+                    }
+                    SectionKind::Tls => elf::SHF_ALLOC | elf::SHF_WRITE | elf::SHF_TLS,
+                    SectionKind::UninitializedData => elf::SHF_ALLOC | elf::SHF_WRITE,
+                    SectionKind::UninitializedTls => elf::SHF_ALLOC | elf::SHF_WRITE | elf::SHF_TLS,
+                    SectionKind::ReadOnlyData => elf::SHF_ALLOC,
+                    SectionKind::ReadOnlyString => {
+                        elf::SHF_ALLOC | elf::SHF_STRINGS | elf::SHF_MERGE
+                    }
+                    SectionKind::OtherString => elf::SHF_STRINGS | elf::SHF_MERGE,
+                    SectionKind::Other
+                    | SectionKind::Debug
+                    | SectionKind::Metadata
+                    | SectionKind::Linker
+                    | SectionKind::Note
+                    | SectionKind::Elf(_) => 0,
+                    SectionKind::Unknown | SectionKind::Common | SectionKind::TlsVariables => {
+                        return Err(Error(format!(
+                            "unimplemented section `{}` kind {:?}",
+                            section.name().unwrap_or(""),
+                            section.kind
+                        )));
+                    }
+                }
+                .into()
+            };
+            // TODO: not sure if this is correct, maybe user should determine this
+            let sh_entsize = match section.kind {
+                SectionKind::ReadOnlyString | SectionKind::OtherString => 1,
+                _ => 0,
+            };
+            writer.write_section_header(&SectionHeader {
+                name: Some(section_offsets[index].str_id),
+                sh_type,
+                sh_flags,
+                sh_addr: 0,
+                sh_offset: section_offsets[index].offset as u64,
+                sh_size: section.size,
+                sh_link: 0,
+                sh_info: 0,
+                sh_addralign: section.align,
+                sh_entsize,
+            });
+
+            if !section.relocations.is_empty() {
+                writer.write_relocation_section_header(
+                    section_offsets[index].reloc_str_id.unwrap(),
+                    section_offsets[index].index,
+                    symtab_index,
+                    section_offsets[index].reloc_offset,
+                    section.relocations.len(),
+                    is_rela,
+                );
+            }
+        }
+
+        writer.write_symtab_section_header(symtab_num_local);
+        writer.write_symtab_shndx_section_header();
+        writer.write_strtab_section_header();
+        writer.write_shstrtab_section_header();
+
+        debug_assert_eq!(writer.reserved_len(), writer.len());
+
+        Ok(())
+    }
+}
diff --git a/vendor/object/src/write/elf/writer.rs b/vendor/object/src/write/elf/writer.rs
new file mode 100644
index 0000000..9750924
--- /dev/null
+++ b/vendor/object/src/write/elf/writer.rs
@@ -0,0 +1,2143 @@
+//! Helper for writing ELF files.
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::mem;
+
+use crate::elf;
+use crate::endian::*;
+use crate::pod;
+use crate::write::string::{StringId, StringTable};
+use crate::write::util;
+use crate::write::{Error, Result, WritableBuffer};
+
+/// The index of an ELF section.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct SectionIndex(pub u32);
+
+/// The index of an ELF symbol.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct SymbolIndex(pub u32);
+
+/// A helper for writing ELF files.
+///
+/// Writing uses a two phase approach. The first phase builds up all of the information
+/// that may need to be known ahead of time:
+/// - build string tables
+/// - reserve section indices
+/// - reserve symbol indices
+/// - reserve file ranges for headers and sections
+///
+/// Some of the information has ordering requirements. For example, strings must be added
+/// to string tables before reserving the file range for the string table. Symbol indices
+/// must be reserved after reserving the section indices they reference. There are debug
+/// asserts to check some of these requirements.
+///
+/// The second phase writes everything out in order. Thus the caller must ensure writing
+/// is in the same order that file ranges were reserved. There are debug asserts to assist
+/// with checking this.
+#[allow(missing_debug_implementations)]
+pub struct Writer<'a> {
+    endian: Endianness,
+    is_64: bool,
+    is_mips64el: bool,
+    elf_align: usize,
+
+    buffer: &'a mut dyn WritableBuffer,
+    len: usize,
+
+    segment_offset: usize,
+    segment_num: u32,
+
+    section_offset: usize,
+    section_num: u32,
+
+    shstrtab: StringTable<'a>,
+    shstrtab_str_id: Option<StringId>,
+    shstrtab_index: SectionIndex,
+    shstrtab_offset: usize,
+    shstrtab_data: Vec<u8>,
+
+    need_strtab: bool,
+    strtab: StringTable<'a>,
+    strtab_str_id: Option<StringId>,
+    strtab_index: SectionIndex,
+    strtab_offset: usize,
+    strtab_data: Vec<u8>,
+
+    symtab_str_id: Option<StringId>,
+    symtab_index: SectionIndex,
+    symtab_offset: usize,
+    symtab_num: u32,
+
+    need_symtab_shndx: bool,
+    symtab_shndx_str_id: Option<StringId>,
+    symtab_shndx_offset: usize,
+    symtab_shndx_data: Vec<u8>,
+
+    need_dynstr: bool,
+    dynstr: StringTable<'a>,
+    dynstr_str_id: Option<StringId>,
+    dynstr_index: SectionIndex,
+    dynstr_offset: usize,
+    dynstr_data: Vec<u8>,
+
+    dynsym_str_id: Option<StringId>,
+    dynsym_index: SectionIndex,
+    dynsym_offset: usize,
+    dynsym_num: u32,
+
+    dynamic_str_id: Option<StringId>,
+    dynamic_offset: usize,
+    dynamic_num: usize,
+
+    hash_str_id: Option<StringId>,
+    hash_offset: usize,
+    hash_size: usize,
+
+    gnu_hash_str_id: Option<StringId>,
+    gnu_hash_offset: usize,
+    gnu_hash_size: usize,
+
+    gnu_versym_str_id: Option<StringId>,
+    gnu_versym_offset: usize,
+
+    gnu_verdef_str_id: Option<StringId>,
+    gnu_verdef_offset: usize,
+    gnu_verdef_size: usize,
+    gnu_verdef_count: u16,
+    gnu_verdef_remaining: u16,
+    gnu_verdaux_remaining: u16,
+
+    gnu_verneed_str_id: Option<StringId>,
+    gnu_verneed_offset: usize,
+    gnu_verneed_size: usize,
+    gnu_verneed_count: u16,
+    gnu_verneed_remaining: u16,
+    gnu_vernaux_remaining: u16,
+
+    gnu_attributes_str_id: Option<StringId>,
+    gnu_attributes_offset: usize,
+    gnu_attributes_size: usize,
+}
+
+impl<'a> Writer<'a> {
+    /// Create a new `Writer` for the given endianness and ELF class.
+    pub fn new(endian: Endianness, is_64: bool, buffer: &'a mut dyn WritableBuffer) -> Self {
+        let elf_align = if is_64 { 8 } else { 4 };
+        Writer {
+            endian,
+            is_64,
+            // Determined later.
+            is_mips64el: false,
+            elf_align,
+
+            buffer,
+            len: 0,
+
+            segment_offset: 0,
+            segment_num: 0,
+
+            section_offset: 0,
+            section_num: 0,
+
+            shstrtab: StringTable::default(),
+            shstrtab_str_id: None,
+            shstrtab_index: SectionIndex(0),
+            shstrtab_offset: 0,
+            shstrtab_data: Vec::new(),
+
+            need_strtab: false,
+            strtab: StringTable::default(),
+            strtab_str_id: None,
+            strtab_index: SectionIndex(0),
+            strtab_offset: 0,
+            strtab_data: Vec::new(),
+
+            symtab_str_id: None,
+            symtab_index: SectionIndex(0),
+            symtab_offset: 0,
+            symtab_num: 0,
+
+            need_symtab_shndx: false,
+            symtab_shndx_str_id: None,
+            symtab_shndx_offset: 0,
+            symtab_shndx_data: Vec::new(),
+
+            need_dynstr: false,
+            dynstr: StringTable::default(),
+            dynstr_str_id: None,
+            dynstr_index: SectionIndex(0),
+            dynstr_offset: 0,
+            dynstr_data: Vec::new(),
+
+            dynsym_str_id: None,
+            dynsym_index: SectionIndex(0),
+            dynsym_offset: 0,
+            dynsym_num: 0,
+
+            dynamic_str_id: None,
+            dynamic_offset: 0,
+            dynamic_num: 0,
+
+            hash_str_id: None,
+            hash_offset: 0,
+            hash_size: 0,
+
+            gnu_hash_str_id: None,
+            gnu_hash_offset: 0,
+            gnu_hash_size: 0,
+
+            gnu_versym_str_id: None,
+            gnu_versym_offset: 0,
+
+            gnu_verdef_str_id: None,
+            gnu_verdef_offset: 0,
+            gnu_verdef_size: 0,
+            gnu_verdef_count: 0,
+            gnu_verdef_remaining: 0,
+            gnu_verdaux_remaining: 0,
+
+            gnu_verneed_str_id: None,
+            gnu_verneed_offset: 0,
+            gnu_verneed_size: 0,
+            gnu_verneed_count: 0,
+            gnu_verneed_remaining: 0,
+            gnu_vernaux_remaining: 0,
+
+            gnu_attributes_str_id: None,
+            gnu_attributes_offset: 0,
+            gnu_attributes_size: 0,
+        }
+    }
+
+    /// Return the current file length that has been reserved.
+    pub fn reserved_len(&self) -> usize {
+        self.len
+    }
+
+    /// Return the current file length that has been written.
+    #[allow(clippy::len_without_is_empty)]
+    pub fn len(&self) -> usize {
+        self.buffer.len()
+    }
+
+    /// Reserve a file range with the given size and starting alignment.
+    ///
+    /// Returns the aligned offset of the start of the range.
+    pub fn reserve(&mut self, len: usize, align_start: usize) -> usize {
+        if align_start > 1 {
+            self.len = util::align(self.len, align_start);
+        }
+        let offset = self.len;
+        self.len += len;
+        offset
+    }
+
+    /// Write alignment padding bytes.
+    pub fn write_align(&mut self, align_start: usize) {
+        if align_start > 1 {
+            util::write_align(self.buffer, align_start);
+        }
+    }
+
+    /// Write data.
+    ///
+    /// This is typically used to write section data.
+    pub fn write(&mut self, data: &[u8]) {
+        self.buffer.write_bytes(data);
+    }
+
+    /// Reserve the file range up to the given file offset.
+    pub fn reserve_until(&mut self, offset: usize) {
+        debug_assert!(self.len <= offset);
+        self.len = offset;
+    }
+
+    /// Write padding up to the given file offset.
+    pub fn pad_until(&mut self, offset: usize) {
+        debug_assert!(self.buffer.len() <= offset);
+        self.buffer.resize(offset);
+    }
+
+    fn file_header_size(&self) -> usize {
+        if self.is_64 {
+            mem::size_of::<elf::FileHeader64<Endianness>>()
+        } else {
+            mem::size_of::<elf::FileHeader32<Endianness>>()
+        }
+    }
+
+    /// Reserve the range for the file header.
+    ///
+    /// This must be at the start of the file.
+    pub fn reserve_file_header(&mut self) {
+        debug_assert_eq!(self.len, 0);
+        self.reserve(self.file_header_size(), 1);
+    }
+
+    /// Write the file header.
+    ///
+    /// This must be at the start of the file.
+    ///
+    /// Fields that can be derived from known information are automatically set by this function.
+    pub fn write_file_header(&mut self, header: &FileHeader) -> Result<()> {
+        debug_assert_eq!(self.buffer.len(), 0);
+
+        self.is_mips64el =
+            self.is_64 && self.endian.is_little_endian() && header.e_machine == elf::EM_MIPS;
+
+        // Start writing.
+        self.buffer
+            .reserve(self.len)
+            .map_err(|_| Error(String::from("Cannot allocate buffer")))?;
+
+        // Write file header.
+        let e_ident = elf::Ident {
+            magic: elf::ELFMAG,
+            class: if self.is_64 {
+                elf::ELFCLASS64
+            } else {
+                elf::ELFCLASS32
+            },
+            data: if self.endian.is_little_endian() {
+                elf::ELFDATA2LSB
+            } else {
+                elf::ELFDATA2MSB
+            },
+            version: elf::EV_CURRENT,
+            os_abi: header.os_abi,
+            abi_version: header.abi_version,
+            padding: [0; 7],
+        };
+
+        let e_ehsize = self.file_header_size() as u16;
+
+        let e_phoff = self.segment_offset as u64;
+        let e_phentsize = if self.segment_num == 0 {
+            0
+        } else {
+            self.program_header_size() as u16
+        };
+        // TODO: overflow
+        let e_phnum = self.segment_num as u16;
+
+        let e_shoff = self.section_offset as u64;
+        let e_shentsize = if self.section_num == 0 {
+            0
+        } else {
+            self.section_header_size() as u16
+        };
+        let e_shnum = if self.section_num >= elf::SHN_LORESERVE.into() {
+            0
+        } else {
+            self.section_num as u16
+        };
+        let e_shstrndx = if self.shstrtab_index.0 >= elf::SHN_LORESERVE.into() {
+            elf::SHN_XINDEX
+        } else {
+            self.shstrtab_index.0 as u16
+        };
+
+        let endian = self.endian;
+        if self.is_64 {
+            let file = elf::FileHeader64 {
+                e_ident,
+                e_type: U16::new(endian, header.e_type),
+                e_machine: U16::new(endian, header.e_machine),
+                e_version: U32::new(endian, elf::EV_CURRENT.into()),
+                e_entry: U64::new(endian, header.e_entry),
+                e_phoff: U64::new(endian, e_phoff),
+                e_shoff: U64::new(endian, e_shoff),
+                e_flags: U32::new(endian, header.e_flags),
+                e_ehsize: U16::new(endian, e_ehsize),
+                e_phentsize: U16::new(endian, e_phentsize),
+                e_phnum: U16::new(endian, e_phnum),
+                e_shentsize: U16::new(endian, e_shentsize),
+                e_shnum: U16::new(endian, e_shnum),
+                e_shstrndx: U16::new(endian, e_shstrndx),
+            };
+            self.buffer.write(&file)
+        } else {
+            let file = elf::FileHeader32 {
+                e_ident,
+                e_type: U16::new(endian, header.e_type),
+                e_machine: U16::new(endian, header.e_machine),
+                e_version: U32::new(endian, elf::EV_CURRENT.into()),
+                e_entry: U32::new(endian, header.e_entry as u32),
+                e_phoff: U32::new(endian, e_phoff as u32),
+                e_shoff: U32::new(endian, e_shoff as u32),
+                e_flags: U32::new(endian, header.e_flags),
+                e_ehsize: U16::new(endian, e_ehsize),
+                e_phentsize: U16::new(endian, e_phentsize),
+                e_phnum: U16::new(endian, e_phnum),
+                e_shentsize: U16::new(endian, e_shentsize),
+                e_shnum: U16::new(endian, e_shnum),
+                e_shstrndx: U16::new(endian, e_shstrndx),
+            };
+            self.buffer.write(&file);
+        }
+
+        Ok(())
+    }
+
+    fn program_header_size(&self) -> usize {
+        if self.is_64 {
+            mem::size_of::<elf::ProgramHeader64<Endianness>>()
+        } else {
+            mem::size_of::<elf::ProgramHeader32<Endianness>>()
+        }
+    }
+
+    /// Reserve the range for the program headers.
+    pub fn reserve_program_headers(&mut self, num: u32) {
+        debug_assert_eq!(self.segment_offset, 0);
+        if num == 0 {
+            return;
+        }
+        self.segment_num = num;
+        self.segment_offset =
+            self.reserve(num as usize * self.program_header_size(), self.elf_align);
+    }
+
+    /// Write alignment padding bytes prior to the program headers.
+    pub fn write_align_program_headers(&mut self) {
+        if self.segment_offset == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.segment_offset, self.buffer.len());
+    }
+
+    /// Write a program header.
+    pub fn write_program_header(&mut self, header: &ProgramHeader) {
+        let endian = self.endian;
+        if self.is_64 {
+            let header = elf::ProgramHeader64 {
+                p_type: U32::new(endian, header.p_type),
+                p_flags: U32::new(endian, header.p_flags),
+                p_offset: U64::new(endian, header.p_offset),
+                p_vaddr: U64::new(endian, header.p_vaddr),
+                p_paddr: U64::new(endian, header.p_paddr),
+                p_filesz: U64::new(endian, header.p_filesz),
+                p_memsz: U64::new(endian, header.p_memsz),
+                p_align: U64::new(endian, header.p_align),
+            };
+            self.buffer.write(&header);
+        } else {
+            let header = elf::ProgramHeader32 {
+                p_type: U32::new(endian, header.p_type),
+                p_offset: U32::new(endian, header.p_offset as u32),
+                p_vaddr: U32::new(endian, header.p_vaddr as u32),
+                p_paddr: U32::new(endian, header.p_paddr as u32),
+                p_filesz: U32::new(endian, header.p_filesz as u32),
+                p_memsz: U32::new(endian, header.p_memsz as u32),
+                p_flags: U32::new(endian, header.p_flags),
+                p_align: U32::new(endian, header.p_align as u32),
+            };
+            self.buffer.write(&header);
+        }
+    }
+
+    /// Reserve the section index for the null section header.
+    ///
+    /// The null section header is usually automatically reserved,
+    /// but this can be used to force an empty section table.
+    ///
+    /// This must be called before [`Self::reserve_section_headers`].
+    pub fn reserve_null_section_index(&mut self) -> SectionIndex {
+        debug_assert_eq!(self.section_num, 0);
+        if self.section_num == 0 {
+            self.section_num = 1;
+        }
+        SectionIndex(0)
+    }
+
+    /// Reserve a section table index.
+    ///
+    /// Automatically also reserves the null section header if required.
+    ///
+    /// This must be called before [`Self::reserve_section_headers`].
+    pub fn reserve_section_index(&mut self) -> SectionIndex {
+        debug_assert_eq!(self.section_offset, 0);
+        if self.section_num == 0 {
+            self.section_num = 1;
+        }
+        let index = self.section_num;
+        self.section_num += 1;
+        SectionIndex(index)
+    }
+
+    fn section_header_size(&self) -> usize {
+        if self.is_64 {
+            mem::size_of::<elf::SectionHeader64<Endianness>>()
+        } else {
+            mem::size_of::<elf::SectionHeader32<Endianness>>()
+        }
+    }
+
+    /// Reserve the range for the section headers.
+    ///
+    /// This function does nothing if no sections were reserved.
+    /// This must be called after [`Self::reserve_section_index`]
+    /// and other functions that reserve section indices.
+    pub fn reserve_section_headers(&mut self) {
+        debug_assert_eq!(self.section_offset, 0);
+        if self.section_num == 0 {
+            return;
+        }
+        self.section_offset = self.reserve(
+            self.section_num as usize * self.section_header_size(),
+            self.elf_align,
+        );
+    }
+
+    /// Write the null section header.
+    ///
+    /// This must be the first section header that is written.
+    /// This function does nothing if no sections were reserved.
+    pub fn write_null_section_header(&mut self) {
+        if self.section_num == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.section_offset, self.buffer.len());
+        self.write_section_header(&SectionHeader {
+            name: None,
+            sh_type: 0,
+            sh_flags: 0,
+            sh_addr: 0,
+            sh_offset: 0,
+            sh_size: if self.section_num >= elf::SHN_LORESERVE.into() {
+                self.section_num.into()
+            } else {
+                0
+            },
+            sh_link: if self.shstrtab_index.0 >= elf::SHN_LORESERVE.into() {
+                self.shstrtab_index.0
+            } else {
+                0
+            },
+            // TODO: e_phnum overflow
+            sh_info: 0,
+            sh_addralign: 0,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Write a section header.
+    pub fn write_section_header(&mut self, section: &SectionHeader) {
+        let sh_name = if let Some(name) = section.name {
+            self.shstrtab.get_offset(name) as u32
+        } else {
+            0
+        };
+        let endian = self.endian;
+        if self.is_64 {
+            let section = elf::SectionHeader64 {
+                sh_name: U32::new(endian, sh_name),
+                sh_type: U32::new(endian, section.sh_type),
+                sh_flags: U64::new(endian, section.sh_flags),
+                sh_addr: U64::new(endian, section.sh_addr),
+                sh_offset: U64::new(endian, section.sh_offset),
+                sh_size: U64::new(endian, section.sh_size),
+                sh_link: U32::new(endian, section.sh_link),
+                sh_info: U32::new(endian, section.sh_info),
+                sh_addralign: U64::new(endian, section.sh_addralign),
+                sh_entsize: U64::new(endian, section.sh_entsize),
+            };
+            self.buffer.write(&section);
+        } else {
+            let section = elf::SectionHeader32 {
+                sh_name: U32::new(endian, sh_name),
+                sh_type: U32::new(endian, section.sh_type),
+                sh_flags: U32::new(endian, section.sh_flags as u32),
+                sh_addr: U32::new(endian, section.sh_addr as u32),
+                sh_offset: U32::new(endian, section.sh_offset as u32),
+                sh_size: U32::new(endian, section.sh_size as u32),
+                sh_link: U32::new(endian, section.sh_link),
+                sh_info: U32::new(endian, section.sh_info),
+                sh_addralign: U32::new(endian, section.sh_addralign as u32),
+                sh_entsize: U32::new(endian, section.sh_entsize as u32),
+            };
+            self.buffer.write(&section);
+        }
+    }
+
+    /// Add a section name to the section header string table.
+    ///
+    /// This will be stored in the `.shstrtab` section.
+    ///
+    /// This must be called before [`Self::reserve_shstrtab`].
+    pub fn add_section_name(&mut self, name: &'a [u8]) -> StringId {
+        debug_assert_eq!(self.shstrtab_offset, 0);
+        self.shstrtab.add(name)
+    }
+
+    /// Reserve the range for the section header string table.
+    ///
+    /// This range is used for a section named `.shstrtab`.
+    ///
+    /// This function does nothing if no sections were reserved.
+    /// This must be called after [`Self::add_section_name`].
+    /// and other functions that reserve section names and indices.
+    pub fn reserve_shstrtab(&mut self) {
+        debug_assert_eq!(self.shstrtab_offset, 0);
+        if self.section_num == 0 {
+            return;
+        }
+        // Start with null section name.
+        self.shstrtab_data = vec![0];
+        self.shstrtab.write(1, &mut self.shstrtab_data);
+        self.shstrtab_offset = self.reserve(self.shstrtab_data.len(), 1);
+    }
+
+    /// Write the section header string table.
+    ///
+    /// This function does nothing if the section was not reserved.
+    pub fn write_shstrtab(&mut self) {
+        if self.shstrtab_offset == 0 {
+            return;
+        }
+        debug_assert_eq!(self.shstrtab_offset, self.buffer.len());
+        self.buffer.write_bytes(&self.shstrtab_data);
+    }
+
+    /// Reserve the section index for the section header string table.
+    ///
+    /// This must be called before [`Self::reserve_shstrtab`]
+    /// and [`Self::reserve_section_headers`].
+    pub fn reserve_shstrtab_section_index(&mut self) -> SectionIndex {
+        debug_assert_eq!(self.shstrtab_index, SectionIndex(0));
+        self.shstrtab_str_id = Some(self.add_section_name(&b".shstrtab"[..]));
+        self.shstrtab_index = self.reserve_section_index();
+        self.shstrtab_index
+    }
+
+    /// Write the section header for the section header string table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_shstrtab_section_header(&mut self) {
+        if self.shstrtab_index == SectionIndex(0) {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.shstrtab_str_id,
+            sh_type: elf::SHT_STRTAB,
+            sh_flags: 0,
+            sh_addr: 0,
+            sh_offset: self.shstrtab_offset as u64,
+            sh_size: self.shstrtab_data.len() as u64,
+            sh_link: 0,
+            sh_info: 0,
+            sh_addralign: 1,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Add a string to the string table.
+    ///
+    /// This will be stored in the `.strtab` section.
+    ///
+    /// This must be called before [`Self::reserve_strtab`].
+    pub fn add_string(&mut self, name: &'a [u8]) -> StringId {
+        debug_assert_eq!(self.strtab_offset, 0);
+        self.need_strtab = true;
+        self.strtab.add(name)
+    }
+
+    /// Return true if `.strtab` is needed.
+    pub fn strtab_needed(&self) -> bool {
+        self.need_strtab
+    }
+
+    /// Reserve the range for the string table.
+    ///
+    /// This range is used for a section named `.strtab`.
+    ///
+    /// This function does nothing if no strings or symbols were defined.
+    /// This must be called after [`Self::add_string`].
+    pub fn reserve_strtab(&mut self) {
+        debug_assert_eq!(self.strtab_offset, 0);
+        if !self.need_strtab {
+            return;
+        }
+        // Start with null string.
+        self.strtab_data = vec![0];
+        self.strtab.write(1, &mut self.strtab_data);
+        self.strtab_offset = self.reserve(self.strtab_data.len(), 1);
+    }
+
+    /// Write the string table.
+    ///
+    /// This function does nothing if the section was not reserved.
+    pub fn write_strtab(&mut self) {
+        if self.strtab_offset == 0 {
+            return;
+        }
+        debug_assert_eq!(self.strtab_offset, self.buffer.len());
+        self.buffer.write_bytes(&self.strtab_data);
+    }
+
+    /// Reserve the section index for the string table.
+    ///
+    /// This must be called before [`Self::reserve_section_headers`].
+    pub fn reserve_strtab_section_index(&mut self) -> SectionIndex {
+        debug_assert_eq!(self.strtab_index, SectionIndex(0));
+        self.strtab_str_id = Some(self.add_section_name(&b".strtab"[..]));
+        self.strtab_index = self.reserve_section_index();
+        self.strtab_index
+    }
+
+    /// Write the section header for the string table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_strtab_section_header(&mut self) {
+        if self.strtab_index == SectionIndex(0) {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.strtab_str_id,
+            sh_type: elf::SHT_STRTAB,
+            sh_flags: 0,
+            sh_addr: 0,
+            sh_offset: self.strtab_offset as u64,
+            sh_size: self.strtab_data.len() as u64,
+            sh_link: 0,
+            sh_info: 0,
+            sh_addralign: 1,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Reserve the null symbol table entry.
+    ///
+    /// This will be stored in the `.symtab` section.
+    ///
+    /// The null symbol table entry is usually automatically reserved,
+    /// but this can be used to force an empty symbol table.
+    ///
+    /// This must be called before [`Self::reserve_symtab`].
+    pub fn reserve_null_symbol_index(&mut self) -> SymbolIndex {
+        debug_assert_eq!(self.symtab_offset, 0);
+        debug_assert_eq!(self.symtab_num, 0);
+        self.symtab_num = 1;
+        // The symtab must link to a strtab.
+        self.need_strtab = true;
+        SymbolIndex(0)
+    }
+
+    /// Reserve a symbol table entry.
+    ///
+    /// This will be stored in the `.symtab` section.
+    ///
+    /// `section_index` is used to determine whether `.symtab_shndx` is required.
+    ///
+    /// Automatically also reserves the null symbol if required.
+    /// Callers may assume that the returned indices will be sequential
+    /// starting at 1.
+    ///
+    /// This must be called before [`Self::reserve_symtab`] and
+    /// [`Self::reserve_symtab_shndx`].
+    pub fn reserve_symbol_index(&mut self, section_index: Option<SectionIndex>) -> SymbolIndex {
+        debug_assert_eq!(self.symtab_offset, 0);
+        debug_assert_eq!(self.symtab_shndx_offset, 0);
+        if self.symtab_num == 0 {
+            self.symtab_num = 1;
+            // The symtab must link to a strtab.
+            self.need_strtab = true;
+        }
+        let index = self.symtab_num;
+        self.symtab_num += 1;
+        if let Some(section_index) = section_index {
+            if section_index.0 >= elf::SHN_LORESERVE.into() {
+                self.need_symtab_shndx = true;
+            }
+        }
+        SymbolIndex(index)
+    }
+
+    /// Return the number of reserved symbol table entries.
+    ///
+    /// Includes the null symbol.
+    pub fn symbol_count(&self) -> u32 {
+        self.symtab_num
+    }
+
+    fn symbol_size(&self) -> usize {
+        if self.is_64 {
+            mem::size_of::<elf::Sym64<Endianness>>()
+        } else {
+            mem::size_of::<elf::Sym32<Endianness>>()
+        }
+    }
+
+    /// Reserve the range for the symbol table.
+    ///
+    /// This range is used for a section named `.symtab`.
+    /// This function does nothing if no symbols were reserved.
+    /// This must be called after [`Self::reserve_symbol_index`].
+    pub fn reserve_symtab(&mut self) {
+        debug_assert_eq!(self.symtab_offset, 0);
+        if self.symtab_num == 0 {
+            return;
+        }
+        self.symtab_offset = self.reserve(
+            self.symtab_num as usize * self.symbol_size(),
+            self.elf_align,
+        );
+    }
+
+    /// Write the null symbol.
+    ///
+    /// This must be the first symbol that is written.
+    /// This function does nothing if no symbols were reserved.
+    pub fn write_null_symbol(&mut self) {
+        if self.symtab_num == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.symtab_offset, self.buffer.len());
+        if self.is_64 {
+            self.buffer.write(&elf::Sym64::<Endianness>::default());
+        } else {
+            self.buffer.write(&elf::Sym32::<Endianness>::default());
+        }
+
+        if self.need_symtab_shndx {
+            self.symtab_shndx_data.write_pod(&U32::new(self.endian, 0));
+        }
+    }
+
+    /// Write a symbol.
+    pub fn write_symbol(&mut self, sym: &Sym) {
+        let st_name = if let Some(name) = sym.name {
+            self.strtab.get_offset(name) as u32
+        } else {
+            0
+        };
+        let st_shndx = if let Some(section) = sym.section {
+            if section.0 >= elf::SHN_LORESERVE as u32 {
+                elf::SHN_XINDEX
+            } else {
+                section.0 as u16
+            }
+        } else {
+            sym.st_shndx
+        };
+
+        let endian = self.endian;
+        if self.is_64 {
+            let sym = elf::Sym64 {
+                st_name: U32::new(endian, st_name),
+                st_info: sym.st_info,
+                st_other: sym.st_other,
+                st_shndx: U16::new(endian, st_shndx),
+                st_value: U64::new(endian, sym.st_value),
+                st_size: U64::new(endian, sym.st_size),
+            };
+            self.buffer.write(&sym);
+        } else {
+            let sym = elf::Sym32 {
+                st_name: U32::new(endian, st_name),
+                st_info: sym.st_info,
+                st_other: sym.st_other,
+                st_shndx: U16::new(endian, st_shndx),
+                st_value: U32::new(endian, sym.st_value as u32),
+                st_size: U32::new(endian, sym.st_size as u32),
+            };
+            self.buffer.write(&sym);
+        }
+
+        if self.need_symtab_shndx {
+            let section_index = sym.section.unwrap_or(SectionIndex(0));
+            self.symtab_shndx_data
+                .write_pod(&U32::new(self.endian, section_index.0));
+        }
+    }
+
+    /// Reserve the section index for the symbol table.
+    ///
+    /// This must be called before [`Self::reserve_section_headers`].
+    pub fn reserve_symtab_section_index(&mut self) -> SectionIndex {
+        debug_assert_eq!(self.symtab_index, SectionIndex(0));
+        self.symtab_str_id = Some(self.add_section_name(&b".symtab"[..]));
+        self.symtab_index = self.reserve_section_index();
+        self.symtab_index
+    }
+
+    /// Return the section index of the symbol table.
+    pub fn symtab_index(&mut self) -> SectionIndex {
+        self.symtab_index
+    }
+
+    /// Write the section header for the symbol table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_symtab_section_header(&mut self, num_local: u32) {
+        if self.symtab_index == SectionIndex(0) {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.symtab_str_id,
+            sh_type: elf::SHT_SYMTAB,
+            sh_flags: 0,
+            sh_addr: 0,
+            sh_offset: self.symtab_offset as u64,
+            sh_size: self.symtab_num as u64 * self.symbol_size() as u64,
+            sh_link: self.strtab_index.0,
+            sh_info: num_local,
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: self.symbol_size() as u64,
+        });
+    }
+
+    /// Return true if `.symtab_shndx` is needed.
+    pub fn symtab_shndx_needed(&self) -> bool {
+        self.need_symtab_shndx
+    }
+
+    /// Reserve the range for the extended section indices for the symbol table.
+    ///
+    /// This range is used for a section named `.symtab_shndx`.
+    /// This also reserves a section index.
+    ///
+    /// This function does nothing if extended section indices are not needed.
+    /// This must be called after [`Self::reserve_symbol_index`].
+    pub fn reserve_symtab_shndx(&mut self) {
+        debug_assert_eq!(self.symtab_shndx_offset, 0);
+        if !self.need_symtab_shndx {
+            return;
+        }
+        self.symtab_shndx_offset = self.reserve(self.symtab_num as usize * 4, 4);
+        self.symtab_shndx_data.reserve(self.symtab_num as usize * 4);
+    }
+
+    /// Write the extended section indices for the symbol table.
+    ///
+    /// This function does nothing if the section was not reserved.
+    pub fn write_symtab_shndx(&mut self) {
+        if self.symtab_shndx_offset == 0 {
+            return;
+        }
+        debug_assert_eq!(self.symtab_shndx_offset, self.buffer.len());
+        debug_assert_eq!(self.symtab_num as usize * 4, self.symtab_shndx_data.len());
+        self.buffer.write_bytes(&self.symtab_shndx_data);
+    }
+
+    /// Reserve the section index for the extended section indices symbol table.
+    ///
+    /// You should check [`Self::symtab_shndx_needed`] before calling this
+    /// unless you have other means of knowing if this section is needed.
+    ///
+    /// This must be called before [`Self::reserve_section_headers`].
+    pub fn reserve_symtab_shndx_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.symtab_shndx_str_id.is_none());
+        self.symtab_shndx_str_id = Some(self.add_section_name(&b".symtab_shndx"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Write the section header for the extended section indices for the symbol table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_symtab_shndx_section_header(&mut self) {
+        if self.symtab_shndx_str_id.is_none() {
+            return;
+        }
+        let sh_size = if self.symtab_shndx_offset == 0 {
+            0
+        } else {
+            (self.symtab_num * 4) as u64
+        };
+        self.write_section_header(&SectionHeader {
+            name: self.symtab_shndx_str_id,
+            sh_type: elf::SHT_SYMTAB_SHNDX,
+            sh_flags: 0,
+            sh_addr: 0,
+            sh_offset: self.symtab_shndx_offset as u64,
+            sh_size,
+            sh_link: self.symtab_index.0,
+            sh_info: 0,
+            sh_addralign: 4,
+            sh_entsize: 4,
+        });
+    }
+
+    /// Add a string to the dynamic string table.
+    ///
+    /// This will be stored in the `.dynstr` section.
+    ///
+    /// This must be called before [`Self::reserve_dynstr`].
+    pub fn add_dynamic_string(&mut self, name: &'a [u8]) -> StringId {
+        debug_assert_eq!(self.dynstr_offset, 0);
+        self.need_dynstr = true;
+        self.dynstr.add(name)
+    }
+
+    /// Get a string that was previously added to the dynamic string table.
+    ///
+    /// Panics if the string was not added.
+    pub fn get_dynamic_string(&self, name: &'a [u8]) -> StringId {
+        self.dynstr.get_id(name)
+    }
+
+    /// Return true if `.dynstr` is needed.
+    pub fn dynstr_needed(&self) -> bool {
+        self.need_dynstr
+    }
+
+    /// Reserve the range for the dynamic string table.
+    ///
+    /// This range is used for a section named `.dynstr`.
+    ///
+    /// This function does nothing if no dynamic strings or symbols were defined.
+    /// This must be called after [`Self::add_dynamic_string`].
+    pub fn reserve_dynstr(&mut self) {
+        debug_assert_eq!(self.dynstr_offset, 0);
+        if !self.need_dynstr {
+            return;
+        }
+        // Start with null string.
+        self.dynstr_data = vec![0];
+        self.dynstr.write(1, &mut self.dynstr_data);
+        self.dynstr_offset = self.reserve(self.dynstr_data.len(), 1);
+    }
+
+    /// Write the dynamic string table.
+    ///
+    /// This function does nothing if the section was not reserved.
+    pub fn write_dynstr(&mut self) {
+        if self.dynstr_offset == 0 {
+            return;
+        }
+        debug_assert_eq!(self.dynstr_offset, self.buffer.len());
+        self.buffer.write_bytes(&self.dynstr_data);
+    }
+
+    /// Reserve the section index for the dynamic string table.
+    ///
+    /// This must be called before [`Self::reserve_section_headers`].
+    pub fn reserve_dynstr_section_index(&mut self) -> SectionIndex {
+        debug_assert_eq!(self.dynstr_index, SectionIndex(0));
+        self.dynstr_str_id = Some(self.add_section_name(&b".dynstr"[..]));
+        self.dynstr_index = self.reserve_section_index();
+        self.dynstr_index
+    }
+
+    /// Return the section index of the dynamic string table.
+    pub fn dynstr_index(&mut self) -> SectionIndex {
+        self.dynstr_index
+    }
+
+    /// Write the section header for the dynamic string table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_dynstr_section_header(&mut self, sh_addr: u64) {
+        if self.dynstr_index == SectionIndex(0) {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.dynstr_str_id,
+            sh_type: elf::SHT_STRTAB,
+            sh_flags: elf::SHF_ALLOC.into(),
+            sh_addr,
+            sh_offset: self.dynstr_offset as u64,
+            sh_size: self.dynstr_data.len() as u64,
+            sh_link: 0,
+            sh_info: 0,
+            sh_addralign: 1,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Reserve the null dynamic symbol table entry.
+    ///
+    /// This will be stored in the `.dynsym` section.
+    ///
+    /// The null dynamic symbol table entry is usually automatically reserved,
+    /// but this can be used to force an empty dynamic symbol table.
+    ///
+    /// This must be called before [`Self::reserve_dynsym`].
+    pub fn reserve_null_dynamic_symbol_index(&mut self) -> SymbolIndex {
+        debug_assert_eq!(self.dynsym_offset, 0);
+        debug_assert_eq!(self.dynsym_num, 0);
+        self.dynsym_num = 1;
+        // The symtab must link to a strtab.
+        self.need_dynstr = true;
+        SymbolIndex(0)
+    }
+
+    /// Reserve a dynamic symbol table entry.
+    ///
+    /// This will be stored in the `.dynsym` section.
+    ///
+    /// Automatically also reserves the null symbol if required.
+    /// Callers may assume that the returned indices will be sequential
+    /// starting at 1.
+    ///
+    /// This must be called before [`Self::reserve_dynsym`].
+    pub fn reserve_dynamic_symbol_index(&mut self) -> SymbolIndex {
+        debug_assert_eq!(self.dynsym_offset, 0);
+        if self.dynsym_num == 0 {
+            self.dynsym_num = 1;
+            // The symtab must link to a strtab.
+            self.need_dynstr = true;
+        }
+        let index = self.dynsym_num;
+        self.dynsym_num += 1;
+        SymbolIndex(index)
+    }
+
+    /// Return the number of reserved dynamic symbols.
+    ///
+    /// Includes the null symbol.
+    pub fn dynamic_symbol_count(&mut self) -> u32 {
+        self.dynsym_num
+    }
+
+    /// Reserve the range for the dynamic symbol table.
+    ///
+    /// This range is used for a section named `.dynsym`.
+    ///
+    /// This function does nothing if no dynamic symbols were reserved.
+    /// This must be called after [`Self::reserve_dynamic_symbol_index`].
+    pub fn reserve_dynsym(&mut self) {
+        debug_assert_eq!(self.dynsym_offset, 0);
+        if self.dynsym_num == 0 {
+            return;
+        }
+        self.dynsym_offset = self.reserve(
+            self.dynsym_num as usize * self.symbol_size(),
+            self.elf_align,
+        );
+    }
+
+    /// Write the null dynamic symbol.
+    ///
+    /// This must be the first dynamic symbol that is written.
+    /// This function does nothing if no dynamic symbols were reserved.
+    pub fn write_null_dynamic_symbol(&mut self) {
+        if self.dynsym_num == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.dynsym_offset, self.buffer.len());
+        if self.is_64 {
+            self.buffer.write(&elf::Sym64::<Endianness>::default());
+        } else {
+            self.buffer.write(&elf::Sym32::<Endianness>::default());
+        }
+    }
+
+    /// Write a dynamic symbol.
+    pub fn write_dynamic_symbol(&mut self, sym: &Sym) {
+        let st_name = if let Some(name) = sym.name {
+            self.dynstr.get_offset(name) as u32
+        } else {
+            0
+        };
+
+        let st_shndx = if let Some(section) = sym.section {
+            if section.0 >= elf::SHN_LORESERVE as u32 {
+                // TODO: we don't actually write out .dynsym_shndx yet.
+                // This is unlikely to be needed though.
+                elf::SHN_XINDEX
+            } else {
+                section.0 as u16
+            }
+        } else {
+            sym.st_shndx
+        };
+
+        let endian = self.endian;
+        if self.is_64 {
+            let sym = elf::Sym64 {
+                st_name: U32::new(endian, st_name),
+                st_info: sym.st_info,
+                st_other: sym.st_other,
+                st_shndx: U16::new(endian, st_shndx),
+                st_value: U64::new(endian, sym.st_value),
+                st_size: U64::new(endian, sym.st_size),
+            };
+            self.buffer.write(&sym);
+        } else {
+            let sym = elf::Sym32 {
+                st_name: U32::new(endian, st_name),
+                st_info: sym.st_info,
+                st_other: sym.st_other,
+                st_shndx: U16::new(endian, st_shndx),
+                st_value: U32::new(endian, sym.st_value as u32),
+                st_size: U32::new(endian, sym.st_size as u32),
+            };
+            self.buffer.write(&sym);
+        }
+    }
+
+    /// Reserve the section index for the dynamic symbol table.
+    ///
+    /// This must be called before [`Self::reserve_section_headers`].
+    pub fn reserve_dynsym_section_index(&mut self) -> SectionIndex {
+        debug_assert_eq!(self.dynsym_index, SectionIndex(0));
+        self.dynsym_str_id = Some(self.add_section_name(&b".dynsym"[..]));
+        self.dynsym_index = self.reserve_section_index();
+        self.dynsym_index
+    }
+
+    /// Return the section index of the dynamic symbol table.
+    pub fn dynsym_index(&mut self) -> SectionIndex {
+        self.dynsym_index
+    }
+
+    /// Write the section header for the dynamic symbol table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_dynsym_section_header(&mut self, sh_addr: u64, num_local: u32) {
+        if self.dynsym_index == SectionIndex(0) {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.dynsym_str_id,
+            sh_type: elf::SHT_DYNSYM,
+            sh_flags: elf::SHF_ALLOC.into(),
+            sh_addr,
+            sh_offset: self.dynsym_offset as u64,
+            sh_size: self.dynsym_num as u64 * self.symbol_size() as u64,
+            sh_link: self.dynstr_index.0,
+            sh_info: num_local,
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: self.symbol_size() as u64,
+        });
+    }
+
+    fn dyn_size(&self) -> usize {
+        if self.is_64 {
+            mem::size_of::<elf::Dyn64<Endianness>>()
+        } else {
+            mem::size_of::<elf::Dyn32<Endianness>>()
+        }
+    }
+
+    /// Reserve the range for the `.dynamic` section.
+    ///
+    /// This function does nothing if `dynamic_num` is zero.
+    pub fn reserve_dynamic(&mut self, dynamic_num: usize) {
+        debug_assert_eq!(self.dynamic_offset, 0);
+        if dynamic_num == 0 {
+            return;
+        }
+        self.dynamic_num = dynamic_num;
+        self.dynamic_offset = self.reserve(dynamic_num * self.dyn_size(), self.elf_align);
+    }
+
+    /// Write alignment padding bytes prior to the `.dynamic` section.
+    ///
+    /// This function does nothing if the section was not reserved.
+    pub fn write_align_dynamic(&mut self) {
+        if self.dynamic_offset == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.dynamic_offset, self.buffer.len());
+    }
+
+    /// Write a dynamic string entry.
+    pub fn write_dynamic_string(&mut self, tag: u32, id: StringId) {
+        self.write_dynamic(tag, self.dynstr.get_offset(id) as u64);
+    }
+
+    /// Write a dynamic value entry.
+    pub fn write_dynamic(&mut self, d_tag: u32, d_val: u64) {
+        debug_assert!(self.dynamic_offset <= self.buffer.len());
+        let endian = self.endian;
+        if self.is_64 {
+            let d = elf::Dyn64 {
+                d_tag: U64::new(endian, d_tag.into()),
+                d_val: U64::new(endian, d_val),
+            };
+            self.buffer.write(&d);
+        } else {
+            let d = elf::Dyn32 {
+                d_tag: U32::new(endian, d_tag),
+                d_val: U32::new(endian, d_val as u32),
+            };
+            self.buffer.write(&d);
+        }
+        debug_assert!(
+            self.dynamic_offset + self.dynamic_num * self.dyn_size() >= self.buffer.len()
+        );
+    }
+
+    /// Reserve the section index for the dynamic table.
+    pub fn reserve_dynamic_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.dynamic_str_id.is_none());
+        self.dynamic_str_id = Some(self.add_section_name(&b".dynamic"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Write the section header for the dynamic table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_dynamic_section_header(&mut self, sh_addr: u64) {
+        if self.dynamic_str_id.is_none() {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.dynamic_str_id,
+            sh_type: elf::SHT_DYNAMIC,
+            sh_flags: (elf::SHF_WRITE | elf::SHF_ALLOC).into(),
+            sh_addr,
+            sh_offset: self.dynamic_offset as u64,
+            sh_size: (self.dynamic_num * self.dyn_size()) as u64,
+            sh_link: self.dynstr_index.0,
+            sh_info: 0,
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: self.dyn_size() as u64,
+        });
+    }
+
+    fn rel_size(&self, is_rela: bool) -> usize {
+        if self.is_64 {
+            if is_rela {
+                mem::size_of::<elf::Rela64<Endianness>>()
+            } else {
+                mem::size_of::<elf::Rel64<Endianness>>()
+            }
+        } else {
+            if is_rela {
+                mem::size_of::<elf::Rela32<Endianness>>()
+            } else {
+                mem::size_of::<elf::Rel32<Endianness>>()
+            }
+        }
+    }
+
+    /// Reserve a file range for a SysV hash section.
+    ///
+    /// `symbol_count` is the number of symbols in the hash,
+    /// not the total number of symbols.
+    pub fn reserve_hash(&mut self, bucket_count: u32, chain_count: u32) {
+        self.hash_size = mem::size_of::<elf::HashHeader<Endianness>>()
+            + bucket_count as usize * 4
+            + chain_count as usize * 4;
+        self.hash_offset = self.reserve(self.hash_size, self.elf_align);
+    }
+
+    /// Write a SysV hash section.
+    ///
+    /// `chain_count` is the number of symbols in the hash.
+    /// The argument to `hash` will be in the range `0..chain_count`.
+    pub fn write_hash<F>(&mut self, bucket_count: u32, chain_count: u32, hash: F)
+    where
+        F: Fn(u32) -> Option<u32>,
+    {
+        let mut buckets = vec![U32::new(self.endian, 0); bucket_count as usize];
+        let mut chains = vec![U32::new(self.endian, 0); chain_count as usize];
+        for i in 0..chain_count {
+            if let Some(hash) = hash(i) {
+                let bucket = hash % bucket_count;
+                chains[i as usize] = buckets[bucket as usize];
+                buckets[bucket as usize] = U32::new(self.endian, i);
+            }
+        }
+
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.hash_offset, self.buffer.len());
+        self.buffer.write(&elf::HashHeader {
+            bucket_count: U32::new(self.endian, bucket_count),
+            chain_count: U32::new(self.endian, chain_count),
+        });
+        self.buffer.write_slice(&buckets);
+        self.buffer.write_slice(&chains);
+    }
+
+    /// Reserve the section index for the SysV hash table.
+    pub fn reserve_hash_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.hash_str_id.is_none());
+        self.hash_str_id = Some(self.add_section_name(&b".hash"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Write the section header for the SysV hash table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_hash_section_header(&mut self, sh_addr: u64) {
+        if self.hash_str_id.is_none() {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.hash_str_id,
+            sh_type: elf::SHT_HASH,
+            sh_flags: elf::SHF_ALLOC.into(),
+            sh_addr,
+            sh_offset: self.hash_offset as u64,
+            sh_size: self.hash_size as u64,
+            sh_link: self.dynsym_index.0,
+            sh_info: 0,
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: 4,
+        });
+    }
+
+    /// Reserve a file range for a GNU hash section.
+    ///
+    /// `symbol_count` is the number of symbols in the hash,
+    /// not the total number of symbols.
+    pub fn reserve_gnu_hash(&mut self, bloom_count: u32, bucket_count: u32, symbol_count: u32) {
+        self.gnu_hash_size = mem::size_of::<elf::GnuHashHeader<Endianness>>()
+            + bloom_count as usize * self.elf_align
+            + bucket_count as usize * 4
+            + symbol_count as usize * 4;
+        self.gnu_hash_offset = self.reserve(self.gnu_hash_size, self.elf_align);
+    }
+
+    /// Write a GNU hash section.
+    ///
+    /// `symbol_count` is the number of symbols in the hash.
+    /// The argument to `hash` will be in the range `0..symbol_count`.
+    ///
+    /// This requires that symbols are already sorted by bucket.
+    pub fn write_gnu_hash<F>(
+        &mut self,
+        symbol_base: u32,
+        bloom_shift: u32,
+        bloom_count: u32,
+        bucket_count: u32,
+        symbol_count: u32,
+        hash: F,
+    ) where
+        F: Fn(u32) -> u32,
+    {
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.gnu_hash_offset, self.buffer.len());
+        self.buffer.write(&elf::GnuHashHeader {
+            bucket_count: U32::new(self.endian, bucket_count),
+            symbol_base: U32::new(self.endian, symbol_base),
+            bloom_count: U32::new(self.endian, bloom_count),
+            bloom_shift: U32::new(self.endian, bloom_shift),
+        });
+
+        // Calculate and write bloom filter.
+        if self.is_64 {
+            let mut bloom_filters = vec![0; bloom_count as usize];
+            for i in 0..symbol_count {
+                let h = hash(i);
+                bloom_filters[((h / 64) & (bloom_count - 1)) as usize] |=
+                    1 << (h % 64) | 1 << ((h >> bloom_shift) % 64);
+            }
+            for bloom_filter in bloom_filters {
+                self.buffer.write(&U64::new(self.endian, bloom_filter));
+            }
+        } else {
+            let mut bloom_filters = vec![0; bloom_count as usize];
+            for i in 0..symbol_count {
+                let h = hash(i);
+                bloom_filters[((h / 32) & (bloom_count - 1)) as usize] |=
+                    1 << (h % 32) | 1 << ((h >> bloom_shift) % 32);
+            }
+            for bloom_filter in bloom_filters {
+                self.buffer.write(&U32::new(self.endian, bloom_filter));
+            }
+        }
+
+        // Write buckets.
+        //
+        // This requires that symbols are already sorted by bucket.
+        let mut bucket = 0;
+        for i in 0..symbol_count {
+            let symbol_bucket = hash(i) % bucket_count;
+            while bucket < symbol_bucket {
+                self.buffer.write(&U32::new(self.endian, 0));
+                bucket += 1;
+            }
+            if bucket == symbol_bucket {
+                self.buffer.write(&U32::new(self.endian, symbol_base + i));
+                bucket += 1;
+            }
+        }
+        while bucket < bucket_count {
+            self.buffer.write(&U32::new(self.endian, 0));
+            bucket += 1;
+        }
+
+        // Write hash values.
+        for i in 0..symbol_count {
+            let mut h = hash(i);
+            if i == symbol_count - 1 || h % bucket_count != hash(i + 1) % bucket_count {
+                h |= 1;
+            } else {
+                h &= !1;
+            }
+            self.buffer.write(&U32::new(self.endian, h));
+        }
+    }
+
+    /// Reserve the section index for the GNU hash table.
+    pub fn reserve_gnu_hash_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.gnu_hash_str_id.is_none());
+        self.gnu_hash_str_id = Some(self.add_section_name(&b".gnu.hash"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Write the section header for the GNU hash table.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_gnu_hash_section_header(&mut self, sh_addr: u64) {
+        if self.gnu_hash_str_id.is_none() {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.gnu_hash_str_id,
+            sh_type: elf::SHT_GNU_HASH,
+            sh_flags: elf::SHF_ALLOC.into(),
+            sh_addr,
+            sh_offset: self.gnu_hash_offset as u64,
+            sh_size: self.gnu_hash_size as u64,
+            sh_link: self.dynsym_index.0,
+            sh_info: 0,
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Reserve the range for the `.gnu.version` section.
+    ///
+    /// This function does nothing if no dynamic symbols were reserved.
+    pub fn reserve_gnu_versym(&mut self) {
+        debug_assert_eq!(self.gnu_versym_offset, 0);
+        if self.dynsym_num == 0 {
+            return;
+        }
+        self.gnu_versym_offset = self.reserve(self.dynsym_num as usize * 2, 2);
+    }
+
+    /// Write the null symbol version entry.
+    ///
+    /// This must be the first symbol version that is written.
+    /// This function does nothing if no dynamic symbols were reserved.
+    pub fn write_null_gnu_versym(&mut self) {
+        if self.dynsym_num == 0 {
+            return;
+        }
+        util::write_align(self.buffer, 2);
+        debug_assert_eq!(self.gnu_versym_offset, self.buffer.len());
+        self.write_gnu_versym(0);
+    }
+
+    /// Write a symbol version entry.
+    pub fn write_gnu_versym(&mut self, versym: u16) {
+        self.buffer.write(&U16::new(self.endian, versym));
+    }
+
+    /// Reserve the section index for the `.gnu.version` section.
+    pub fn reserve_gnu_versym_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.gnu_versym_str_id.is_none());
+        self.gnu_versym_str_id = Some(self.add_section_name(&b".gnu.version"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Write the section header for the `.gnu.version` section.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_gnu_versym_section_header(&mut self, sh_addr: u64) {
+        if self.gnu_versym_str_id.is_none() {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.gnu_versym_str_id,
+            sh_type: elf::SHT_GNU_VERSYM,
+            sh_flags: elf::SHF_ALLOC.into(),
+            sh_addr,
+            sh_offset: self.gnu_versym_offset as u64,
+            sh_size: self.dynsym_num as u64 * 2,
+            sh_link: self.dynsym_index.0,
+            sh_info: 0,
+            sh_addralign: 2,
+            sh_entsize: 2,
+        });
+    }
+
+    /// Reserve the range for the `.gnu.version_d` section.
+    pub fn reserve_gnu_verdef(&mut self, verdef_count: usize, verdaux_count: usize) {
+        debug_assert_eq!(self.gnu_verdef_offset, 0);
+        if verdef_count == 0 {
+            return;
+        }
+        self.gnu_verdef_size = verdef_count * mem::size_of::<elf::Verdef<Endianness>>()
+            + verdaux_count * mem::size_of::<elf::Verdaux<Endianness>>();
+        self.gnu_verdef_offset = self.reserve(self.gnu_verdef_size, self.elf_align);
+        self.gnu_verdef_count = verdef_count as u16;
+        self.gnu_verdef_remaining = self.gnu_verdef_count;
+    }
+
+    /// Write alignment padding bytes prior to a `.gnu.version_d` section.
+    pub fn write_align_gnu_verdef(&mut self) {
+        if self.gnu_verdef_offset == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.gnu_verdef_offset, self.buffer.len());
+    }
+
+    /// Write a version definition entry.
+    pub fn write_gnu_verdef(&mut self, verdef: &Verdef) {
+        debug_assert_ne!(self.gnu_verdef_remaining, 0);
+        self.gnu_verdef_remaining -= 1;
+        let vd_next = if self.gnu_verdef_remaining == 0 {
+            0
+        } else {
+            mem::size_of::<elf::Verdef<Endianness>>() as u32
+                + verdef.aux_count as u32 * mem::size_of::<elf::Verdaux<Endianness>>() as u32
+        };
+
+        self.gnu_verdaux_remaining = verdef.aux_count;
+        let vd_aux = if verdef.aux_count == 0 {
+            0
+        } else {
+            mem::size_of::<elf::Verdef<Endianness>>() as u32
+        };
+
+        self.buffer.write(&elf::Verdef {
+            vd_version: U16::new(self.endian, verdef.version),
+            vd_flags: U16::new(self.endian, verdef.flags),
+            vd_ndx: U16::new(self.endian, verdef.index),
+            vd_cnt: U16::new(self.endian, verdef.aux_count),
+            vd_hash: U32::new(self.endian, elf::hash(self.dynstr.get_string(verdef.name))),
+            vd_aux: U32::new(self.endian, vd_aux),
+            vd_next: U32::new(self.endian, vd_next),
+        });
+        self.write_gnu_verdaux(verdef.name);
+    }
+
+    /// Write a version definition auxiliary entry.
+    pub fn write_gnu_verdaux(&mut self, name: StringId) {
+        debug_assert_ne!(self.gnu_verdaux_remaining, 0);
+        self.gnu_verdaux_remaining -= 1;
+        let vda_next = if self.gnu_verdaux_remaining == 0 {
+            0
+        } else {
+            mem::size_of::<elf::Verdaux<Endianness>>() as u32
+        };
+        self.buffer.write(&elf::Verdaux {
+            vda_name: U32::new(self.endian, self.dynstr.get_offset(name) as u32),
+            vda_next: U32::new(self.endian, vda_next),
+        });
+    }
+
+    /// Reserve the section index for the `.gnu.version_d` section.
+    pub fn reserve_gnu_verdef_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.gnu_verdef_str_id.is_none());
+        self.gnu_verdef_str_id = Some(self.add_section_name(&b".gnu.version_d"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Write the section header for the `.gnu.version_d` section.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_gnu_verdef_section_header(&mut self, sh_addr: u64) {
+        if self.gnu_verdef_str_id.is_none() {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.gnu_verdef_str_id,
+            sh_type: elf::SHT_GNU_VERDEF,
+            sh_flags: elf::SHF_ALLOC.into(),
+            sh_addr,
+            sh_offset: self.gnu_verdef_offset as u64,
+            sh_size: self.gnu_verdef_size as u64,
+            sh_link: self.dynstr_index.0,
+            sh_info: self.gnu_verdef_count.into(),
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Reserve the range for the `.gnu.version_r` section.
+    pub fn reserve_gnu_verneed(&mut self, verneed_count: usize, vernaux_count: usize) {
+        debug_assert_eq!(self.gnu_verneed_offset, 0);
+        if verneed_count == 0 {
+            return;
+        }
+        self.gnu_verneed_size = verneed_count * mem::size_of::<elf::Verneed<Endianness>>()
+            + vernaux_count * mem::size_of::<elf::Vernaux<Endianness>>();
+        self.gnu_verneed_offset = self.reserve(self.gnu_verneed_size, self.elf_align);
+        self.gnu_verneed_count = verneed_count as u16;
+        self.gnu_verneed_remaining = self.gnu_verneed_count;
+    }
+
+    /// Write alignment padding bytes prior to a `.gnu.version_r` section.
+    pub fn write_align_gnu_verneed(&mut self) {
+        if self.gnu_verneed_offset == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.gnu_verneed_offset, self.buffer.len());
+    }
+
+    /// Write a version need entry.
+    pub fn write_gnu_verneed(&mut self, verneed: &Verneed) {
+        debug_assert_ne!(self.gnu_verneed_remaining, 0);
+        self.gnu_verneed_remaining -= 1;
+        let vn_next = if self.gnu_verneed_remaining == 0 {
+            0
+        } else {
+            mem::size_of::<elf::Verneed<Endianness>>() as u32
+                + verneed.aux_count as u32 * mem::size_of::<elf::Vernaux<Endianness>>() as u32
+        };
+
+        self.gnu_vernaux_remaining = verneed.aux_count;
+        let vn_aux = if verneed.aux_count == 0 {
+            0
+        } else {
+            mem::size_of::<elf::Verneed<Endianness>>() as u32
+        };
+
+        self.buffer.write(&elf::Verneed {
+            vn_version: U16::new(self.endian, verneed.version),
+            vn_cnt: U16::new(self.endian, verneed.aux_count),
+            vn_file: U32::new(self.endian, self.dynstr.get_offset(verneed.file) as u32),
+            vn_aux: U32::new(self.endian, vn_aux),
+            vn_next: U32::new(self.endian, vn_next),
+        });
+    }
+
+    /// Write a version need auxiliary entry.
+    pub fn write_gnu_vernaux(&mut self, vernaux: &Vernaux) {
+        debug_assert_ne!(self.gnu_vernaux_remaining, 0);
+        self.gnu_vernaux_remaining -= 1;
+        let vna_next = if self.gnu_vernaux_remaining == 0 {
+            0
+        } else {
+            mem::size_of::<elf::Vernaux<Endianness>>() as u32
+        };
+        self.buffer.write(&elf::Vernaux {
+            vna_hash: U32::new(self.endian, elf::hash(self.dynstr.get_string(vernaux.name))),
+            vna_flags: U16::new(self.endian, vernaux.flags),
+            vna_other: U16::new(self.endian, vernaux.index),
+            vna_name: U32::new(self.endian, self.dynstr.get_offset(vernaux.name) as u32),
+            vna_next: U32::new(self.endian, vna_next),
+        });
+    }
+
+    /// Reserve the section index for the `.gnu.version_r` section.
+    pub fn reserve_gnu_verneed_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.gnu_verneed_str_id.is_none());
+        self.gnu_verneed_str_id = Some(self.add_section_name(&b".gnu.version_r"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Write the section header for the `.gnu.version_r` section.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_gnu_verneed_section_header(&mut self, sh_addr: u64) {
+        if self.gnu_verneed_str_id.is_none() {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.gnu_verneed_str_id,
+            sh_type: elf::SHT_GNU_VERNEED,
+            sh_flags: elf::SHF_ALLOC.into(),
+            sh_addr,
+            sh_offset: self.gnu_verneed_offset as u64,
+            sh_size: self.gnu_verneed_size as u64,
+            sh_link: self.dynstr_index.0,
+            sh_info: self.gnu_verneed_count.into(),
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Reserve the section index for the `.gnu.attributes` section.
+    pub fn reserve_gnu_attributes_section_index(&mut self) -> SectionIndex {
+        debug_assert!(self.gnu_attributes_str_id.is_none());
+        self.gnu_attributes_str_id = Some(self.add_section_name(&b".gnu.attributes"[..]));
+        self.reserve_section_index()
+    }
+
+    /// Reserve the range for the `.gnu.attributes` section.
+    pub fn reserve_gnu_attributes(&mut self, gnu_attributes_size: usize) {
+        debug_assert_eq!(self.gnu_attributes_offset, 0);
+        if gnu_attributes_size == 0 {
+            return;
+        }
+        self.gnu_attributes_size = gnu_attributes_size;
+        self.gnu_attributes_offset = self.reserve(self.gnu_attributes_size, self.elf_align);
+    }
+
+    /// Write the section header for the `.gnu.attributes` section.
+    ///
+    /// This function does nothing if the section index was not reserved.
+    pub fn write_gnu_attributes_section_header(&mut self) {
+        if self.gnu_attributes_str_id.is_none() {
+            return;
+        }
+        self.write_section_header(&SectionHeader {
+            name: self.gnu_attributes_str_id,
+            sh_type: elf::SHT_GNU_ATTRIBUTES,
+            sh_flags: 0,
+            sh_addr: 0,
+            sh_offset: self.gnu_attributes_offset as u64,
+            sh_size: self.gnu_attributes_size as u64,
+            sh_link: self.dynstr_index.0,
+            sh_info: 0, // TODO
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: 0,
+        });
+    }
+
+    /// Write the data for the `.gnu.attributes` section.
+    pub fn write_gnu_attributes(&mut self, data: &[u8]) {
+        if self.gnu_attributes_offset == 0 {
+            return;
+        }
+        util::write_align(self.buffer, self.elf_align);
+        debug_assert_eq!(self.gnu_attributes_offset, self.buffer.len());
+        self.buffer.write_bytes(data);
+    }
+
+    /// Reserve a file range for the given number of relocations.
+    ///
+    /// Returns the offset of the range.
+    pub fn reserve_relocations(&mut self, count: usize, is_rela: bool) -> usize {
+        self.reserve(count * self.rel_size(is_rela), self.elf_align)
+    }
+
+    /// Write alignment padding bytes prior to a relocation section.
+    pub fn write_align_relocation(&mut self) {
+        util::write_align(self.buffer, self.elf_align);
+    }
+
+    /// Write a relocation.
+    pub fn write_relocation(&mut self, is_rela: bool, rel: &Rel) {
+        let endian = self.endian;
+        if self.is_64 {
+            if is_rela {
+                let rel = elf::Rela64 {
+                    r_offset: U64::new(endian, rel.r_offset),
+                    r_info: elf::Rela64::r_info(endian, self.is_mips64el, rel.r_sym, rel.r_type),
+                    r_addend: I64::new(endian, rel.r_addend),
+                };
+                self.buffer.write(&rel);
+            } else {
+                let rel = elf::Rel64 {
+                    r_offset: U64::new(endian, rel.r_offset),
+                    r_info: elf::Rel64::r_info(endian, rel.r_sym, rel.r_type),
+                };
+                self.buffer.write(&rel);
+            }
+        } else {
+            if is_rela {
+                let rel = elf::Rela32 {
+                    r_offset: U32::new(endian, rel.r_offset as u32),
+                    r_info: elf::Rel32::r_info(endian, rel.r_sym, rel.r_type as u8),
+                    r_addend: I32::new(endian, rel.r_addend as i32),
+                };
+                self.buffer.write(&rel);
+            } else {
+                let rel = elf::Rel32 {
+                    r_offset: U32::new(endian, rel.r_offset as u32),
+                    r_info: elf::Rel32::r_info(endian, rel.r_sym, rel.r_type as u8),
+                };
+                self.buffer.write(&rel);
+            }
+        }
+    }
+
+    /// Write the section header for a relocation section.
+    ///
+    /// `section` is the index of the section the relocations apply to,
+    /// or 0 if none.
+    ///
+    /// `symtab` is the index of the symbol table the relocations refer to,
+    /// or 0 if none.
+    ///
+    /// `offset` is the file offset of the relocations.
+    pub fn write_relocation_section_header(
+        &mut self,
+        name: StringId,
+        section: SectionIndex,
+        symtab: SectionIndex,
+        offset: usize,
+        count: usize,
+        is_rela: bool,
+    ) {
+        self.write_section_header(&SectionHeader {
+            name: Some(name),
+            sh_type: if is_rela { elf::SHT_RELA } else { elf::SHT_REL },
+            sh_flags: elf::SHF_INFO_LINK.into(),
+            sh_addr: 0,
+            sh_offset: offset as u64,
+            sh_size: (count * self.rel_size(is_rela)) as u64,
+            sh_link: symtab.0,
+            sh_info: section.0,
+            sh_addralign: self.elf_align as u64,
+            sh_entsize: self.rel_size(is_rela) as u64,
+        });
+    }
+
+    /// Reserve a file range for a COMDAT section.
+    ///
+    /// `count` is the number of sections in the COMDAT group.
+    ///
+    /// Returns the offset of the range.
+    pub fn reserve_comdat(&mut self, count: usize) -> usize {
+        self.reserve((count + 1) * 4, 4)
+    }
+
+    /// Write `GRP_COMDAT` at the start of the COMDAT section.
+    pub fn write_comdat_header(&mut self) {
+        util::write_align(self.buffer, 4);
+        self.buffer.write(&U32::new(self.endian, elf::GRP_COMDAT));
+    }
+
+    /// Write an entry in a COMDAT section.
+    pub fn write_comdat_entry(&mut self, entry: SectionIndex) {
+        self.buffer.write(&U32::new(self.endian, entry.0));
+    }
+
+    /// Write the section header for a COMDAT section.
+    pub fn write_comdat_section_header(
+        &mut self,
+        name: StringId,
+        symtab: SectionIndex,
+        symbol: SymbolIndex,
+        offset: usize,
+        count: usize,
+    ) {
+        self.write_section_header(&SectionHeader {
+            name: Some(name),
+            sh_type: elf::SHT_GROUP,
+            sh_flags: 0,
+            sh_addr: 0,
+            sh_offset: offset as u64,
+            sh_size: ((count + 1) * 4) as u64,
+            sh_link: symtab.0,
+            sh_info: symbol.0,
+            sh_addralign: 4,
+            sh_entsize: 4,
+        });
+    }
+
+    /// Return a helper for writing an attributes section.
+    pub fn attributes_writer(&self) -> AttributesWriter {
+        AttributesWriter::new(self.endian)
+    }
+}
+
+/// A helper for writing an attributes section.
+///
+/// Attributes have a variable length encoding, so it is awkward to write them in a
+/// single pass. Instead, we build the entire attributes section data in memory, using
+/// placeholders for unknown lengths that are filled in later.
+#[allow(missing_debug_implementations)]
+pub struct AttributesWriter {
+    endian: Endianness,
+    data: Vec<u8>,
+    subsection_offset: usize,
+    subsubsection_offset: usize,
+}
+
+impl AttributesWriter {
+    /// Create a new `AttributesWriter` for the given endianness.
+    pub fn new(endian: Endianness) -> Self {
+        AttributesWriter {
+            endian,
+            data: vec![0x41],
+            subsection_offset: 0,
+            subsubsection_offset: 0,
+        }
+    }
+
+    /// Start a new subsection with the given vendor name.
+    pub fn start_subsection(&mut self, vendor: &[u8]) {
+        debug_assert_eq!(self.subsection_offset, 0);
+        debug_assert_eq!(self.subsubsection_offset, 0);
+        self.subsection_offset = self.data.len();
+        self.data.extend_from_slice(&[0; 4]);
+        self.data.extend_from_slice(vendor);
+        self.data.push(0);
+    }
+
+    /// End the subsection.
+    ///
+    /// The subsection length is automatically calculated and written.
+    pub fn end_subsection(&mut self) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_eq!(self.subsubsection_offset, 0);
+        let length = self.data.len() - self.subsection_offset;
+        self.data[self.subsection_offset..][..4]
+            .copy_from_slice(pod::bytes_of(&U32::new(self.endian, length as u32)));
+        self.subsection_offset = 0;
+    }
+
+    /// Start a new sub-subsection with the given tag.
+    pub fn start_subsubsection(&mut self, tag: u8) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_eq!(self.subsubsection_offset, 0);
+        self.subsubsection_offset = self.data.len();
+        self.data.push(tag);
+        self.data.extend_from_slice(&[0; 4]);
+    }
+
+    /// Write a section or symbol index to the sub-subsection.
+    ///
+    /// The user must also call this function to write the terminating 0 index.
+    pub fn write_subsubsection_index(&mut self, index: u32) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_ne!(self.subsubsection_offset, 0);
+        util::write_uleb128(&mut self.data, u64::from(index));
+    }
+
+    /// Write raw index data to the sub-subsection.
+    ///
+    /// The terminating 0 index is automatically written.
+    pub fn write_subsubsection_indices(&mut self, indices: &[u8]) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_ne!(self.subsubsection_offset, 0);
+        self.data.extend_from_slice(indices);
+        self.data.push(0);
+    }
+
+    /// Write an attribute tag to the sub-subsection.
+    pub fn write_attribute_tag(&mut self, tag: u64) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_ne!(self.subsubsection_offset, 0);
+        util::write_uleb128(&mut self.data, tag);
+    }
+
+    /// Write an attribute integer value to the sub-subsection.
+    pub fn write_attribute_integer(&mut self, value: u64) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_ne!(self.subsubsection_offset, 0);
+        util::write_uleb128(&mut self.data, value);
+    }
+
+    /// Write an attribute string value to the sub-subsection.
+    ///
+    /// The value must not include the null terminator.
+    pub fn write_attribute_string(&mut self, value: &[u8]) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_ne!(self.subsubsection_offset, 0);
+        self.data.extend_from_slice(value);
+        self.data.push(0);
+    }
+
+    /// Write raw attribute data to the sub-subsection.
+    pub fn write_subsubsection_attributes(&mut self, attributes: &[u8]) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_ne!(self.subsubsection_offset, 0);
+        self.data.extend_from_slice(attributes);
+    }
+
+    /// End the sub-subsection.
+    ///
+    /// The sub-subsection length is automatically calculated and written.
+    pub fn end_subsubsection(&mut self) {
+        debug_assert_ne!(self.subsection_offset, 0);
+        debug_assert_ne!(self.subsubsection_offset, 0);
+        let length = self.data.len() - self.subsubsection_offset;
+        self.data[self.subsubsection_offset + 1..][..4]
+            .copy_from_slice(pod::bytes_of(&U32::new(self.endian, length as u32)));
+        self.subsubsection_offset = 0;
+    }
+
+    /// Return the completed section data.
+    pub fn data(self) -> Vec<u8> {
+        debug_assert_eq!(self.subsection_offset, 0);
+        debug_assert_eq!(self.subsubsection_offset, 0);
+        self.data
+    }
+}
+
+/// Native endian version of [`elf::FileHeader64`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct FileHeader {
+    pub os_abi: u8,
+    pub abi_version: u8,
+    pub e_type: u16,
+    pub e_machine: u16,
+    pub e_entry: u64,
+    pub e_flags: u32,
+}
+
+/// Native endian version of [`elf::ProgramHeader64`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct ProgramHeader {
+    pub p_type: u32,
+    pub p_flags: u32,
+    pub p_offset: u64,
+    pub p_vaddr: u64,
+    pub p_paddr: u64,
+    pub p_filesz: u64,
+    pub p_memsz: u64,
+    pub p_align: u64,
+}
+
+/// Native endian version of [`elf::SectionHeader64`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct SectionHeader {
+    pub name: Option<StringId>,
+    pub sh_type: u32,
+    pub sh_flags: u64,
+    pub sh_addr: u64,
+    pub sh_offset: u64,
+    pub sh_size: u64,
+    pub sh_link: u32,
+    pub sh_info: u32,
+    pub sh_addralign: u64,
+    pub sh_entsize: u64,
+}
+
+/// Native endian version of [`elf::Sym64`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct Sym {
+    pub name: Option<StringId>,
+    pub section: Option<SectionIndex>,
+    pub st_info: u8,
+    pub st_other: u8,
+    pub st_shndx: u16,
+    pub st_value: u64,
+    pub st_size: u64,
+}
+
+/// Unified native endian version of [`elf::Rel64`] and [`elf::Rela64`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct Rel {
+    pub r_offset: u64,
+    pub r_sym: u32,
+    pub r_type: u32,
+    pub r_addend: i64,
+}
+
+/// Information required for writing [`elf::Verdef`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct Verdef {
+    pub version: u16,
+    pub flags: u16,
+    pub index: u16,
+    pub aux_count: u16,
+    /// The name for the first [`elf::Verdaux`] entry.
+    pub name: StringId,
+}
+
+/// Information required for writing [`elf::Verneed`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct Verneed {
+    pub version: u16,
+    pub aux_count: u16,
+    pub file: StringId,
+}
+
+/// Information required for writing [`elf::Vernaux`].
+#[allow(missing_docs)]
+#[derive(Debug, Clone)]
+pub struct Vernaux {
+    pub flags: u16,
+    pub index: u16,
+    pub name: StringId,
+}