std_detect: Use elf_aux_info on FreeBSD

crates/std_detect/src/detect/os/freebsd/auxvec.rs

@@ -9,11 +9,6 @@
  allow(dead_code)
 )]
 
-/// Key to access the CPU Hardware capabilities bitfield.
-pub(crate) const AT_HWCAP: usize = 25;
-/// Key to access the CPU Hardware capabilities 2 bitfield.
-pub(crate) const AT_HWCAP2: usize = 26;
-
 /// Cache HWCAP bitfields of the ELF Auxiliary Vector.
 ///
 /// If an entry cannot be read all the bits in the bitfield are set to zero.
@@ -38,65 +33,34 @@ pub(crate) struct AuxVec {
 ///
 /// [elf_common.h]: https://svnweb.freebsd.org/base/release/12.0.0/sys/sys/elf_common.h?revision=341707
 pub(crate) fn auxv() -> Result<AuxVec, ()> {
- if let Ok(hwcap) = archauxv(AT_HWCAP) {
- if let Ok(hwcap2) = archauxv(AT_HWCAP2) {
- if hwcap != 0 && hwcap2 != 0 {
- return Ok(AuxVec { hwcap, hwcap2 });
- }
- }
+ let hwcap = archauxv(libc::AT_HWCAP);
+ let hwcap2 = archauxv(libc::AT_HWCAP2);
+ // Zero could indicate that no features were detected, but it's also used to
+ // indicate an error. In particular, on many platforms AT_HWCAP2 will be
+ // legitimately zero, since it contains the most recent feature flags.
+ if hwcap != 0 || hwcap2 != 0 {
+ return Ok(AuxVec { hwcap, hwcap2 });
  }
  Err(())
 }
 
 /// Tries to read the `key` from the auxiliary vector.
-fn archauxv(key: usize) -> Result<usize, ()> {
- use core::mem;
-
- #[derive(Copy, Clone)]
- #[repr(C)]
- pub struct Elf_Auxinfo {
- pub a_type: usize,
- pub a_un: unnamed,
- }
- #[derive(Copy, Clone)]
- #[repr(C)]
- pub union unnamed {
- pub a_val: libc::c_long,
- pub a_ptr: *mut libc::c_void,
- pub a_fcn: Option<unsafe extern "C" fn() -> ()>,
- }
-
- let mut auxv: [Elf_Auxinfo; 27] = [Elf_Auxinfo {
- a_type: 0,
- a_un: unnamed { a_val: 0 },
- }; 27];
-
- let mut len: libc::c_uint = mem::size_of_val(&auxv) as libc::c_uint;
-
+fn archauxv(key: libc::c_int) -> usize {
+ const OUT_LEN: libc::c_int = core::mem::size_of::<libc::c_ulong>() as libc::c_int;
+ let mut out: libc::c_ulong = 0;
  unsafe {
- let mut mib = [
- libc::CTL_KERN,
- libc::KERN_PROC,
- libc::KERN_PROC_AUXV,
- libc::getpid(),
- ];
-
- let ret = libc::sysctl(
- mib.as_mut_ptr(),
- mib.len() as u32,
- &mut auxv as *mut _ as *mut _,
- &mut len as *mut _ as *mut _,
- 0 as *mut libc::c_void,
- 0,
+ // elf_aux_info is available on FreeBSD 12.0+ and 11.4+:
+ // https://github.com/freebsd/freebsd-src/commit/0b08ae2120cdd08c20a2b806e2fcef4d0a36c470
+ // https://github.com/freebsd/freebsd-src/blob/release/11.4.0/sys/sys/auxv.h
+ // FreeBSD 11 support in std has been removed in Rust 1.75 (https://github.com/rust-lang/rust/pull/114521),
+ // so we can safely use this function.
+ let res = libc::elf_aux_info(
+ key,
+ &mut out as *mut libc::c_ulong as *mut libc::c_void,
+ OUT_LEN,
  );
-
- if ret != -1 {
- for i in 0..auxv.len() {
- if auxv[i].a_type == key {
- return Ok(auxv[i].a_un.a_val as usize);
- }
- }
- }
+ // If elf_aux_info fails, `out` will be left at zero (which is the proper default value).
+ debug_assert!(res == 0 || out == 0);
  }
- return Ok(0);
+ out as usize
 }

crates/std_detect/tests/cpu-detection.rs

@@ -228,8 +228,11 @@ fn powerpc_linux() {
 }
 
 #[test]
-#[cfg(all(target_arch = "powerpc64", target_os = "linux"))]
-fn powerpc64_linux() {
+#[cfg(all(
+ target_arch = "powerpc64",
+ any(target_os = "linux", target_os = "freebsd"),
+))]
+fn powerpc64_linux_or_freebsd() {
  println!("altivec: {}", is_powerpc64_feature_detected!("altivec"));
  println!("vsx: {}", is_powerpc64_feature_detected!("vsx"));
  println!("power8: {}", is_powerpc64_feature_detected!("power8"));