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.

1 files changed, 9 insertions, 0 deletions

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;