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-rw-r--r--vendor/rustix/src/backend/linux_raw/param/auxv.rs507
1 files changed, 507 insertions, 0 deletions
diff --git a/vendor/rustix/src/backend/linux_raw/param/auxv.rs b/vendor/rustix/src/backend/linux_raw/param/auxv.rs
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+//! Linux auxv support.
+//!
+//! # Safety
+//!
+//! This uses raw pointers to locate and read the kernel-provided auxv array.
+#![allow(unsafe_code)]
+
+use crate::backend::c;
+use crate::fd::OwnedFd;
+#[cfg(feature = "param")]
+use crate::ffi::CStr;
+use crate::fs::{Mode, OFlags};
+use crate::utils::{as_ptr, check_raw_pointer};
+#[cfg(feature = "alloc")]
+use alloc::vec::Vec;
+use core::mem::size_of;
+use core::ptr::{null_mut, read_unaligned, NonNull};
+#[cfg(feature = "runtime")]
+use core::sync::atomic::AtomicU8;
+use core::sync::atomic::Ordering::Relaxed;
+use core::sync::atomic::{AtomicPtr, AtomicUsize};
+use linux_raw_sys::elf::*;
+use linux_raw_sys::general::{
+ AT_BASE, AT_CLKTCK, AT_EXECFN, AT_HWCAP, AT_HWCAP2, AT_NULL, AT_PAGESZ, AT_SYSINFO_EHDR,
+};
+#[cfg(feature = "runtime")]
+use linux_raw_sys::general::{
+ AT_EGID, AT_ENTRY, AT_EUID, AT_GID, AT_PHDR, AT_PHENT, AT_PHNUM, AT_RANDOM, AT_SECURE, AT_UID,
+};
+
+#[cfg(feature = "param")]
+#[inline]
+pub(crate) fn page_size() -> usize {
+ let mut page_size = PAGE_SIZE.load(Relaxed);
+
+ if page_size == 0 {
+ init_auxv();
+ page_size = PAGE_SIZE.load(Relaxed);
+ }
+
+ page_size
+}
+
+#[cfg(feature = "param")]
+#[inline]
+pub(crate) fn clock_ticks_per_second() -> u64 {
+ let mut ticks = CLOCK_TICKS_PER_SECOND.load(Relaxed);
+
+ if ticks == 0 {
+ init_auxv();
+ ticks = CLOCK_TICKS_PER_SECOND.load(Relaxed);
+ }
+
+ ticks as u64
+}
+
+#[cfg(feature = "param")]
+#[inline]
+pub(crate) fn linux_hwcap() -> (usize, usize) {
+ let mut hwcap = HWCAP.load(Relaxed);
+ let mut hwcap2 = HWCAP2.load(Relaxed);
+
+ if hwcap == 0 || hwcap2 == 0 {
+ init_auxv();
+ hwcap = HWCAP.load(Relaxed);
+ hwcap2 = HWCAP2.load(Relaxed);
+ }
+
+ (hwcap, hwcap2)
+}
+
+#[cfg(feature = "param")]
+#[inline]
+pub(crate) fn linux_execfn() -> &'static CStr {
+ let mut execfn = EXECFN.load(Relaxed);
+
+ if execfn.is_null() {
+ init_auxv();
+ execfn = EXECFN.load(Relaxed);
+ }
+
+ // SAFETY: We assume the `AT_EXECFN` value provided by the kernel is a
+ // valid pointer to a valid NUL-terminated array of bytes.
+ unsafe { CStr::from_ptr(execfn.cast()) }
+}
+
+#[cfg(feature = "runtime")]
+#[inline]
+pub(crate) fn linux_secure() -> bool {
+ let mut secure = SECURE.load(Relaxed);
+
+ // 0 means not initialized yet.
+ if secure == 0 {
+ init_auxv();
+ secure = SECURE.load(Relaxed);
+ }
+
+ // 0 means not present. Libc `getauxval(AT_SECURE)` would return 0.
+ // 1 means not in secure mode.
+ // 2 means in secure mode.
+ secure > 1
+}
+
+#[cfg(feature = "runtime")]
+#[inline]
+pub(crate) fn exe_phdrs() -> (*const c::c_void, usize, usize) {
+ let mut phdr = PHDR.load(Relaxed);
+ let mut phent = PHENT.load(Relaxed);
+ let mut phnum = PHNUM.load(Relaxed);
+
+ if phdr.is_null() || phnum == 0 {
+ init_auxv();
+ phdr = PHDR.load(Relaxed);
+ phent = PHENT.load(Relaxed);
+ phnum = PHNUM.load(Relaxed);
+ }
+
+ (phdr.cast(), phent, phnum)
+}
+
+/// `AT_SYSINFO_EHDR` isn't present on all platforms in all configurations, so
+/// if we don't see it, this function returns a null pointer.
+#[inline]
+pub(in super::super) fn sysinfo_ehdr() -> *const Elf_Ehdr {
+ let mut ehdr = SYSINFO_EHDR.load(Relaxed);
+
+ if ehdr.is_null() {
+ init_auxv();
+ ehdr = SYSINFO_EHDR.load(Relaxed);
+ }
+
+ ehdr
+}
+
+#[cfg(feature = "runtime")]
+#[inline]
+pub(crate) fn entry() -> usize {
+ let mut entry = ENTRY.load(Relaxed);
+
+ if entry == 0 {
+ init_auxv();
+ entry = ENTRY.load(Relaxed);
+ }
+
+ entry
+}
+
+#[cfg(feature = "runtime")]
+#[inline]
+pub(crate) fn random() -> *const [u8; 16] {
+ let mut random = RANDOM.load(Relaxed);
+
+ if random.is_null() {
+ init_auxv();
+ random = RANDOM.load(Relaxed);
+ }
+
+ random
+}
+
+static PAGE_SIZE: AtomicUsize = AtomicUsize::new(0);
+static CLOCK_TICKS_PER_SECOND: AtomicUsize = AtomicUsize::new(0);
+static HWCAP: AtomicUsize = AtomicUsize::new(0);
+static HWCAP2: AtomicUsize = AtomicUsize::new(0);
+static EXECFN: AtomicPtr<c::c_char> = AtomicPtr::new(null_mut());
+static SYSINFO_EHDR: AtomicPtr<Elf_Ehdr> = AtomicPtr::new(null_mut());
+#[cfg(feature = "runtime")]
+static SECURE: AtomicU8 = AtomicU8::new(0);
+#[cfg(feature = "runtime")]
+static PHDR: AtomicPtr<Elf_Phdr> = AtomicPtr::new(null_mut());
+#[cfg(feature = "runtime")]
+static PHENT: AtomicUsize = AtomicUsize::new(0);
+#[cfg(feature = "runtime")]
+static PHNUM: AtomicUsize = AtomicUsize::new(0);
+#[cfg(feature = "runtime")]
+static ENTRY: AtomicUsize = AtomicUsize::new(0);
+#[cfg(feature = "runtime")]
+static RANDOM: AtomicPtr<[u8; 16]> = AtomicPtr::new(null_mut());
+
+#[cfg(feature = "alloc")]
+fn pr_get_auxv() -> crate::io::Result<Vec<u8>> {
+ use super::super::conv::{c_int, pass_usize, ret_usize};
+ const PR_GET_AUXV: c::c_int = 0x4155_5856;
+ let mut buffer = alloc::vec![0u8; 512];
+ let len = unsafe {
+ ret_usize(syscall_always_asm!(
+ __NR_prctl,
+ c_int(PR_GET_AUXV),
+ buffer.as_ptr(),
+ pass_usize(buffer.len()),
+ pass_usize(0),
+ pass_usize(0)
+ ))?
+ };
+ if len <= buffer.len() {
+ buffer.truncate(len);
+ return Ok(buffer);
+ }
+ buffer.resize(len, 0);
+ let len = unsafe {
+ ret_usize(syscall_always_asm!(
+ __NR_prctl,
+ c_int(PR_GET_AUXV),
+ buffer.as_ptr(),
+ pass_usize(buffer.len()),
+ pass_usize(0),
+ pass_usize(0)
+ ))?
+ };
+ assert_eq!(len, buffer.len());
+ return Ok(buffer);
+}
+
+/// If we don't have "use-explicitly-provided-auxv" or "use-libc-auxv", we
+/// read the aux vector via the `prctl` `PR_GET_AUXV`, with a fallback to
+/// /proc/self/auxv for kernels that don't support `PR_GET_AUXV`.
+#[cold]
+fn init_auxv() {
+ #[cfg(feature = "alloc")]
+ {
+ match pr_get_auxv() {
+ Ok(buffer) => {
+ // SAFETY: We assume the kernel returns a valid auxv.
+ unsafe {
+ init_from_aux_iter(AuxPointer(buffer.as_ptr().cast())).unwrap();
+ }
+ return;
+ }
+ Err(_) => {
+ // Fall back to /proc/self/auxv on error.
+ }
+ }
+ }
+
+ // Open "/proc/self/auxv", either because we trust "/proc", or because
+ // we're running inside QEMU and `proc_self_auxv`'s extra checking foils
+ // QEMU's emulation so we need to do a plain open to get the right
+ // auxv records.
+ let file = crate::fs::open("/proc/self/auxv", OFlags::RDONLY, Mode::empty()).unwrap();
+
+ #[cfg(feature = "alloc")]
+ init_from_auxv_file(file).unwrap();
+
+ #[cfg(not(feature = "alloc"))]
+ unsafe {
+ init_from_aux_iter(AuxFile(file)).unwrap();
+ }
+}
+
+/// Process auxv entries from the open file `auxv`.
+#[cfg(feature = "alloc")]
+#[cold]
+#[must_use]
+fn init_from_auxv_file(auxv: OwnedFd) -> Option<()> {
+ let mut buffer = Vec::<u8>::with_capacity(512);
+ loop {
+ let cur = buffer.len();
+
+ // Request one extra byte; `Vec` will often allocate more.
+ buffer.reserve(1);
+
+ // Use all the space it allocated.
+ buffer.resize(buffer.capacity(), 0);
+
+ // Read up to that many bytes.
+ let n = match crate::io::read(&auxv, &mut buffer[cur..]) {
+ Err(crate::io::Errno::INTR) => 0,
+ Err(_err) => panic!(),
+ Ok(0) => break,
+ Ok(n) => n,
+ };
+
+ // Account for the number of bytes actually read.
+ buffer.resize(cur + n, 0_u8);
+ }
+
+ // SAFETY: We loaded from an auxv file into the buffer.
+ unsafe { init_from_aux_iter(AuxPointer(buffer.as_ptr().cast())) }
+}
+
+/// Process auxv entries from the auxv array pointed to by `auxp`.
+///
+/// # Safety
+///
+/// This must be passed a pointer to an auxv array.
+///
+/// The buffer contains `Elf_aux_t` elements, though it need not be aligned;
+/// function uses `read_unaligned` to read from it.
+#[cold]
+#[must_use]
+unsafe fn init_from_aux_iter(aux_iter: impl Iterator<Item = Elf_auxv_t>) -> Option<()> {
+ let mut pagesz = 0;
+ let mut clktck = 0;
+ let mut hwcap = 0;
+ let mut hwcap2 = 0;
+ let mut execfn = null_mut();
+ let mut sysinfo_ehdr = null_mut();
+ #[cfg(feature = "runtime")]
+ let mut secure = 0;
+ #[cfg(feature = "runtime")]
+ let mut phdr = null_mut();
+ #[cfg(feature = "runtime")]
+ let mut phnum = 0;
+ #[cfg(feature = "runtime")]
+ let mut phent = 0;
+ #[cfg(feature = "runtime")]
+ let mut entry = 0;
+ #[cfg(feature = "runtime")]
+ let mut uid = None;
+ #[cfg(feature = "runtime")]
+ let mut euid = None;
+ #[cfg(feature = "runtime")]
+ let mut gid = None;
+ #[cfg(feature = "runtime")]
+ let mut egid = None;
+ #[cfg(feature = "runtime")]
+ let mut random = null_mut();
+
+ for Elf_auxv_t { a_type, a_val } in aux_iter {
+ match a_type as _ {
+ AT_PAGESZ => pagesz = a_val as usize,
+ AT_CLKTCK => clktck = a_val as usize,
+ AT_HWCAP => hwcap = a_val as usize,
+ AT_HWCAP2 => hwcap2 = a_val as usize,
+ AT_EXECFN => execfn = check_raw_pointer::<c::c_char>(a_val as *mut _)?.as_ptr(),
+ AT_SYSINFO_EHDR => sysinfo_ehdr = check_elf_base(a_val as *mut _)?.as_ptr(),
+
+ AT_BASE => {
+ // The `AT_BASE` value can be NULL in a static executable that
+ // doesn't use a dynamic linker. If so, ignore it.
+ if !a_val.is_null() {
+ let _ = check_elf_base(a_val.cast())?;
+ }
+ }
+
+ #[cfg(feature = "runtime")]
+ AT_SECURE => secure = (a_val as usize != 0) as u8 + 1,
+ #[cfg(feature = "runtime")]
+ AT_UID => uid = Some(a_val),
+ #[cfg(feature = "runtime")]
+ AT_EUID => euid = Some(a_val),
+ #[cfg(feature = "runtime")]
+ AT_GID => gid = Some(a_val),
+ #[cfg(feature = "runtime")]
+ AT_EGID => egid = Some(a_val),
+ #[cfg(feature = "runtime")]
+ AT_PHDR => phdr = check_raw_pointer::<Elf_Phdr>(a_val as *mut _)?.as_ptr(),
+ #[cfg(feature = "runtime")]
+ AT_PHNUM => phnum = a_val as usize,
+ #[cfg(feature = "runtime")]
+ AT_PHENT => phent = a_val as usize,
+ #[cfg(feature = "runtime")]
+ AT_ENTRY => entry = a_val as usize,
+ #[cfg(feature = "runtime")]
+ AT_RANDOM => random = check_raw_pointer::<[u8; 16]>(a_val as *mut _)?.as_ptr(),
+
+ AT_NULL => break,
+ _ => (),
+ }
+ }
+
+ #[cfg(feature = "runtime")]
+ assert_eq!(phent, size_of::<Elf_Phdr>());
+
+ // If we're running set-uid or set-gid, enable “secure execution” mode,
+ // which doesn't do much, but users may be depending on the things that
+ // it does do.
+ #[cfg(feature = "runtime")]
+ if uid != euid || gid != egid {
+ secure = 2;
+ }
+
+ // The base and sysinfo_ehdr (if present) matches our platform. Accept the
+ // aux values.
+ PAGE_SIZE.store(pagesz, Relaxed);
+ CLOCK_TICKS_PER_SECOND.store(clktck, Relaxed);
+ HWCAP.store(hwcap, Relaxed);
+ HWCAP2.store(hwcap2, Relaxed);
+ EXECFN.store(execfn, Relaxed);
+ SYSINFO_EHDR.store(sysinfo_ehdr, Relaxed);
+ #[cfg(feature = "runtime")]
+ SECURE.store(secure, Relaxed);
+ #[cfg(feature = "runtime")]
+ PHDR.store(phdr, Relaxed);
+ #[cfg(feature = "runtime")]
+ PHNUM.store(phnum, Relaxed);
+ #[cfg(feature = "runtime")]
+ ENTRY.store(entry, Relaxed);
+ #[cfg(feature = "runtime")]
+ RANDOM.store(random, Relaxed);
+
+ Some(())
+}
+
+/// Check that `base` is a valid pointer to the kernel-provided vDSO.
+///
+/// `base` is some value we got from a `AT_SYSINFO_EHDR` aux record somewhere,
+/// which hopefully holds the value of the kernel-provided vDSO in memory. Do a
+/// series of checks to be as sure as we can that it's safe to use.
+#[cold]
+#[must_use]
+unsafe fn check_elf_base(base: *const Elf_Ehdr) -> Option<NonNull<Elf_Ehdr>> {
+ // If we're reading a 64-bit auxv on a 32-bit platform, we'll see a zero
+ // `a_val` because `AT_*` values are never greater than `u32::MAX`. Zero is
+ // used by libc's `getauxval` to indicate errors, so it should never be a
+ // valid value.
+ if base.is_null() {
+ return None;
+ }
+
+ let hdr = match check_raw_pointer::<Elf_Ehdr>(base as *mut _) {
+ Some(hdr) => hdr,
+ None => return None,
+ };
+
+ let hdr = hdr.as_ref();
+ if hdr.e_ident[..SELFMAG] != ELFMAG {
+ return None; // Wrong ELF magic
+ }
+ if !matches!(hdr.e_ident[EI_OSABI], ELFOSABI_SYSV | ELFOSABI_LINUX) {
+ return None; // Unrecognized ELF OS ABI
+ }
+ if hdr.e_ident[EI_ABIVERSION] != ELFABIVERSION {
+ return None; // Unrecognized ELF ABI version
+ }
+ if hdr.e_type != ET_DYN {
+ return None; // Wrong ELF type
+ }
+
+ // If ELF is extended, we'll need to adjust.
+ if hdr.e_ident[EI_VERSION] != EV_CURRENT
+ || hdr.e_ehsize as usize != size_of::<Elf_Ehdr>()
+ || hdr.e_phentsize as usize != size_of::<Elf_Phdr>()
+ {
+ return None;
+ }
+ // We don't currently support extra-large numbers of segments.
+ if hdr.e_phnum == PN_XNUM {
+ return None;
+ }
+
+ // If `e_phoff` is zero, it's more likely that we're looking at memory that
+ // has been zeroed than that the kernel has somehow aliased the `Ehdr` and
+ // the `Phdr`.
+ if hdr.e_phoff < size_of::<Elf_Ehdr>() {
+ return None;
+ }
+
+ // Verify that the `EI_CLASS`/`EI_DATA`/`e_machine` fields match the
+ // architecture we're running as. This helps catch cases where we're
+ // running under QEMU.
+ if hdr.e_ident[EI_CLASS] != ELFCLASS {
+ return None; // Wrong ELF class
+ }
+ if hdr.e_ident[EI_DATA] != ELFDATA {
+ return None; // Wrong ELF data
+ }
+ if hdr.e_machine != EM_CURRENT {
+ return None; // Wrong machine type
+ }
+
+ Some(NonNull::new_unchecked(as_ptr(hdr) as *mut _))
+}
+
+// Aux reading utilities
+
+// Read auxv records from an array in memory.
+struct AuxPointer(*const Elf_auxv_t);
+
+impl Iterator for AuxPointer {
+ type Item = Elf_auxv_t;
+
+ #[cold]
+ fn next(&mut self) -> Option<Self::Item> {
+ unsafe {
+ let value = read_unaligned(self.0);
+ self.0 = self.0.add(1);
+ Some(value)
+ }
+ }
+}
+
+// Read auxv records from a file.
+#[cfg(not(feature = "alloc"))]
+struct AuxFile(OwnedFd);
+
+#[cfg(not(feature = "alloc"))]
+impl Iterator for AuxFile {
+ type Item = Elf_auxv_t;
+
+ // This implementation does lots of `read`s and it isn't amazing, but
+ // hopefully we won't use it often.
+ #[cold]
+ fn next(&mut self) -> Option<Self::Item> {
+ let mut buf = [0_u8; size_of::<Self::Item>()];
+ let mut slice = &mut buf[..];
+ while !slice.is_empty() {
+ match crate::io::read(&self.0, slice) {
+ Ok(0) => panic!("unexpected end of auxv file"),
+ Ok(n) => slice = &mut slice[n..],
+ Err(crate::io::Errno::INTR) => continue,
+ Err(err) => panic!("{:?}", err),
+ }
+ }
+ Some(unsafe { read_unaligned(buf.as_ptr().cast()) })
+ }
+}
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