Disable CFI for weakly linked syscalls

Currently, when enabling CFI via -Zsanitizer=cfi and executing e.g.
std::sys::random::getrandom, we can observe a CFI violation. This is
the case for all consumers of the std::sys::pal::weak::weak macro,
as it is defining weak functions which don't show up in LLVM IR
metadata. CFI fails for all these functions.

Similar to other such cases in
https://github.com/rust-lang/rust/issues/115199, this change stops
emitting the CFI typecheck for consumers of the macro via the
\#[no_sanitize(cfi)] attribute.

5 files changed, 15 insertions, 0 deletions

diff --git a/library/std/src/sys/pal/unix/fd.rs b/library/std/src/sys/pal/unix/fd.rs
index 2fc33bdfefb..6da329288f7 100644
--- a/library/std/src/sys/pal/unix/fd.rs
+++ b/library/std/src/sys/pal/unix/fd.rs
@@ -251,6 +251,7 @@ impl FileDesc {
     }
 
     #[cfg(all(target_os = "android", target_pointer_width = "32"))]
+    #[no_sanitize(cfi)]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
         super::weak::weak!(fn preadv64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
 
diff --git a/library/std/src/sys/pal/unix/process/process_unix.rs b/library/std/src/sys/pal/unix/process/process_unix.rs
index 25d9e935332..6d3680d231e 100644
--- a/library/std/src/sys/pal/unix/process/process_unix.rs
+++ b/library/std/src/sys/pal/unix/process/process_unix.rs
@@ -434,6 +434,7 @@ impl Command {
         target_os = "nto",
         target_vendor = "apple",
     ))]
+    #[cfg_attr(target_os = "linux", no_sanitize(cfi))]
     fn posix_spawn(
         &mut self,
         stdio: &ChildPipes,
diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
index 11f6998cac1..33db8e6939a 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/pal/unix/thread.rs
@@ -188,6 +188,7 @@ impl Thread {
     }
 
     #[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
+    #[no_sanitize(cfi)]
     pub fn set_name(name: &CStr) {
         weak! {
             fn pthread_setname_np(
diff --git a/library/std/src/sys/pal/unix/time.rs b/library/std/src/sys/pal/unix/time.rs
index 0271626380c..fc60c307f34 100644
--- a/library/std/src/sys/pal/unix/time.rs
+++ b/library/std/src/sys/pal/unix/time.rs
@@ -96,6 +96,15 @@ impl Timespec {
         }
     }
 
+    #[cfg_attr(
+        all(
+            target_os = "linux",
+            target_env = "gnu",
+            target_pointer_width = "32",
+            not(target_arch = "riscv32")
+        ),
+        no_sanitize(cfi)
+    )]
     pub fn now(clock: libc::clockid_t) -> Timespec {
         use crate::mem::MaybeUninit;
         use crate::sys::cvt;
diff --git a/library/std/src/sys/pal/unix/weak.rs b/library/std/src/sys/pal/unix/weak.rs
index 7ec4787f1ea..9a718b71f46 100644
--- a/library/std/src/sys/pal/unix/weak.rs
+++ b/library/std/src/sys/pal/unix/weak.rs
@@ -144,6 +144,9 @@ unsafe fn fetch(name: &str) -> *mut libc::c_void {
 #[cfg(not(any(target_os = "linux", target_os = "android")))]
 pub(crate) macro syscall {
     (fn $name:ident($($arg_name:ident: $t:ty),*) -> $ret:ty) => (
+        // FIXME: Rust currently omits weak function definitions
+        // and its metadata from LLVM IR.
+        #[no_sanitize(cfi)]
         unsafe fn $name($($arg_name: $t),*) -> $ret {
             weak! { fn $name($($t),*) -> $ret }