Implement linux_execfn, exposing AT_EXECFN.

examples/process.rs

@@ -80,5 +80,7 @@ fn main() -> io::Result<()> {
         target_os = "openbsd",
     )))]
     println!("Rttime Limit: {:?}", getrlimit(Resource::Rttime));
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    println!("Execfn: {:?}", linux_execfn());
     Ok(())
 }

src/imp/libc/process/auxv.rs

@@ -1,3 +1,8 @@
+#[cfg(any(target_os = "android", target_os = "linux"))]
+use libc::c_char;
+#[cfg(any(target_os = "android", target_os = "linux"))]
+use std::ffi::CStr;
+
 #[inline]
 pub(crate) fn page_size() -> usize {
     unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize }
@@ -12,3 +17,9 @@ pub(crate) fn linux_hwcap() -> (usize, usize) {
         (hwcap, hwcap2)
     }
 }
+
+#[cfg(any(target_os = "android", target_os = "linux"))]
+#[inline]
+pub(crate) fn linux_execfn() -> &'static CStr {
+    unsafe { CStr::from_ptr(libc::getauxval(libc::AT_EXECFN) as *const c_char) }
+}

src/imp/libc/process/mod.rs

@@ -1,9 +1,9 @@
 mod auxv;
 mod types;
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
-pub(crate) use auxv::linux_hwcap;
 pub(crate) use auxv::page_size;
+#[cfg(any(target_os = "android", target_os = "linux"))]
+pub(crate) use auxv::{linux_execfn, linux_hwcap};
 #[cfg(not(any(target_os = "fuchsia", target_os = "redox", target_os = "wasi")))]
 pub use types::Resource;
 #[cfg(any(target_os = "android", target_os = "linux"))]

src/imp/linux_raw/process/auxv.rs

@@ -6,13 +6,14 @@
 #![allow(unsafe_code)]
 
 use super::super::elf::Elf_Phdr;
-use linux_raw_sys::general::{AT_HWCAP, AT_NULL, AT_PAGESZ, AT_PHDR, AT_PHENT, AT_PHNUM};
+use linux_raw_sys::general::{AT_HWCAP, AT_NULL, AT_PAGESZ, AT_PHDR, AT_PHENT, AT_PHNUM, AT_EXECFN};
 use linux_raw_sys::v5_4::general::{AT_HWCAP2, AT_SYSINFO_EHDR};
 use std::mem::size_of;
 use std::os::raw::c_char;
 #[cfg(target_env = "gnu")]
 use std::os::raw::c_int;
 use std::slice;
+use std::ffi::CStr;
 
 #[inline]
 pub(crate) fn page_size() -> usize {
@@ -25,6 +26,11 @@ pub(crate) fn linux_hwcap() -> (usize, usize) {
     (auxv.hwcap, auxv.hwcap2)
 }
 
+#[inline]
+pub(crate) fn linux_execfn() -> &'static CStr {
+    unsafe { CStr::from_ptr(auxv().execfn as *const c_char) }
+}
+
 #[inline]
 pub(in super::super) fn exe_phdrs() -> &'static [Elf_Phdr] {
     unsafe { slice::from_raw_parts(AUXV.phdr as *const Elf_Phdr, AUXV.phnum) }
@@ -50,6 +56,7 @@ struct Auxv {
     sysinfo_ehdr: usize,
     phdr: usize,
     phnum: usize,
+    execfn: usize,
 }
 
 /// Data obtained from the kernel-provided auxv array. This is initialized at
@@ -61,6 +68,7 @@ static mut AUXV: Auxv = Auxv {
     sysinfo_ehdr: 0,
     phdr: 0,
     phnum: 0,
+    execfn: 0,
 };
 
 /// GLIBC passes argc, argv, and envp to functions in .init_array, as a
@@ -121,6 +129,7 @@ unsafe fn init_from_auxp(mut auxp: *const Elf_auxv_t) {
             AT_PHDR => AUXV.phdr = a_val,
             AT_PHNUM => AUXV.phnum = a_val,
             AT_PHENT => assert_eq!(a_val, size_of::<Elf_Phdr>()),
+            AT_EXECFN => AUXV.execfn = a_val,
             AT_NULL => break,
             _ => (),
         }

src/imp/linux_raw/process/mod.rs

@@ -2,7 +2,7 @@ mod auxv;
 mod types;
 
 pub(super) use auxv::{exe_phdrs, sysinfo_ehdr};
-pub(crate) use auxv::{linux_hwcap, page_size};
+pub(crate) use auxv::{linux_hwcap, page_size, linux_execfn};
 pub use types::{
     MembarrierCommand, RawCpuid, RawGid, RawPid, RawUid, RawUname, Resource, EXIT_FAILURE,
     EXIT_SIGNALED_SIGABRT, EXIT_SUCCESS,

src/process/auxv.rs

@@ -1,4 +1,6 @@
 use crate::imp;
+#[cfg(any(linux_raw, all(libc, any(target_os = "android", target_os = "linux"))))]
+use std::ffi::CStr;
 
 /// `getpagesize()`—Returns the process' page size.
 #[inline]
@@ -22,3 +24,18 @@ pub fn page_size() -> usize {
 pub fn linux_hwcap() -> (usize, usize) {
     imp::process::linux_hwcap()
 }
+
+/// `getauxval(AT_EXECFN)`—Returns the Linux "execfn" string.
+///
+/// Return the string that Linux has recorded as the filesystem path to the
+/// executable.
+///
+/// # References
+///  - [Linux]
+///
+/// [Linux]: https://man7.org/linux/man-pages/man3/getauxval.3.html
+#[cfg(any(linux_raw, all(libc, any(target_os = "android", target_os = "linux"))))]
+#[inline]
+pub fn linux_execfn() -> &'static CStr {
+    imp::process::linux_execfn()
+}

src/process/mod.rs

@@ -19,7 +19,7 @@ mod sched;
 mod uname;
 
 #[cfg(any(linux_raw, all(libc, any(target_os = "android", target_os = "linux"))))]
-pub use auxv::linux_hwcap;
+pub use auxv::{linux_hwcap, linux_execfn};
 pub use auxv::page_size;
 #[cfg(not(target_os = "wasi"))]
 pub use chdir::chdir;