95 lines
2.7 KiB
Rust
95 lines
2.7 KiB
Rust
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//! Parses ELF auxiliary vectors.
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#![cfg_attr(any(target_arch = "arm", target_arch = "powerpc64"), allow(dead_code))]
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/// Key to access the CPU Hardware capabilities bitfield.
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pub(crate) const AT_HWCAP: usize = 25;
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/// Key to access the CPU Hardware capabilities 2 bitfield.
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pub(crate) const AT_HWCAP2: usize = 26;
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/// Cache HWCAP bitfields of the ELF Auxiliary Vector.
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///
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/// If an entry cannot be read all the bits in the bitfield are set to zero.
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/// This should be interpreted as all the features being disabled.
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#[derive(Debug, Copy, Clone)]
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pub(crate) struct AuxVec {
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pub hwcap: usize,
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pub hwcap2: usize,
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}
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/// ELF Auxiliary Vector
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///
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/// The auxiliary vector is a memory region in a running ELF program's stack
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/// composed of (key: usize, value: usize) pairs.
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///
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/// The keys used in the aux vector are platform dependent. For FreeBSD, they are
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/// defined in [sys/elf_common.h][elf_common_h]. The hardware capabilities of a given
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/// CPU can be queried with the `AT_HWCAP` and `AT_HWCAP2` keys.
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///
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/// Note that run-time feature detection is not invoked for features that can
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/// be detected at compile-time.
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///
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/// [elf_common.h]: https://svnweb.freebsd.org/base/release/12.0.0/sys/sys/elf_common.h?revision=341707
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pub(crate) fn auxv() -> Result<AuxVec, ()> {
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if let Ok(hwcap) = archauxv(AT_HWCAP) {
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if let Ok(hwcap2) = archauxv(AT_HWCAP2) {
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if hwcap != 0 && hwcap2 != 0 {
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return Ok(AuxVec { hwcap, hwcap2 });
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}
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}
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}
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Err(())
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}
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/// Tries to read the `key` from the auxiliary vector.
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fn archauxv(key: usize) -> Result<usize, ()> {
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use crate::mem;
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#[derive(Copy, Clone)]
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#[repr(C)]
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pub struct Elf_Auxinfo {
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pub a_type: usize,
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pub a_un: unnamed,
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}
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#[derive(Copy, Clone)]
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#[repr(C)]
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pub union unnamed {
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pub a_val: libc::c_long,
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pub a_ptr: *mut libc::c_void,
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pub a_fcn: Option<unsafe extern "C" fn() -> ()>,
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}
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let mut auxv: [Elf_Auxinfo; 27] = [Elf_Auxinfo {
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a_type: 0,
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a_un: unnamed { a_val: 0 },
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}; 27];
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let mut len: libc::c_uint = mem::size_of_val(&auxv) as libc::c_uint;
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unsafe {
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let mut mib = [
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libc::CTL_KERN,
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libc::KERN_PROC,
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libc::KERN_PROC_AUXV,
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libc::getpid(),
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];
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let ret = libc::sysctl(
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mib.as_mut_ptr(),
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mib.len() as u32,
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&mut auxv as *mut _ as *mut _,
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&mut len as *mut _ as *mut _,
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0 as *mut libc::c_void,
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0,
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);
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if ret != -1 {
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for i in 0..auxv.len() {
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if auxv[i].a_type == key {
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return Ok(auxv[i].a_un.a_val as usize);
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}
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}
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}
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}
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return Ok(0);
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}
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