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Diffstat (limited to 'vendor/object/src/write/elf/writer.rs')
| -rw-r--r-- | vendor/object/src/write/elf/writer.rs | 2143 |
1 files changed, 2143 insertions, 0 deletions
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(§ion); + } 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(§ion); + } + } + + /// 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, +} |