[compiler-rt] [sanitizer] Fix prctl interceptor causing PAC authentication failure (PR #153081)

[Fei Peng via llvm-commits]

https://github.com/airpfei updated https://github.com/llvm/llvm-project/pull/153081

>From 77b2232ffb70fc41e31a04a3f42127b86d76e9c1 Mon Sep 17 00:00:00 2001
From: Fei Peng <pengfei.02 at bytedance.com>
Date: Mon, 11 Aug 2025 10:13:40 -0700
Subject: [PATCH] [sanitizer] Fix prctl interceptor causing PAC authentication
 failure after PAC key reset

---
 .../sanitizer_common_interceptors.inc         | 29 ++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
index 2d6cf7fc3282f..d02064595385a 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -1285,7 +1285,34 @@ INTERCEPTOR(int, puts, char *s) {
 #endif
 
 #if SANITIZER_INTERCEPT_PRCTL
-INTERCEPTOR(int, prctl, int option, unsigned long arg2, unsigned long arg3,
+
+#if defined(__aarch64__)
+// https://llvm.org/docs/PointerAuth.html
+// AArch64 is currently the only architecture with full PAC support.
+// Avoid adding PAC instructions to prevent crashes caused by
+// prctl(PR_PAC_RESET_KEYS, ...). Since PR_PAC_RESET_KEYS resets the
+// authentication key, returning with the old key still in use
+// can lead to a crash.
+
+#if defined(__ARM_FEATURE_BTI_DEFAULT)
+# define BRANCH_PROTECTION_ATTRIBUTE \
+    __attribute__((target("branch-protection=bti")))
+#else
+# define BRANCH_PROTECTION_ATTRIBUTE \
+    __attribute__((target("branch-protection=none")))
+#endif
+
+#define PRCTL_INTERCEPTOR(ret_type, func, ...)                  \
+  DEFINE_REAL(ret_type, func, __VA_ARGS__)                      \
+  DECLARE_WRAPPER(ret_type, func, __VA_ARGS__)                  \
+  extern "C" INTERCEPTOR_ATTRIBUTE BRANCH_PROTECTION_ATTRIBUTE  \
+      ret_type WRAP(func)(__VA_ARGS__)
+
+#else
+#define PRCTL_INTERCEPTOR INTERCEPTOR
+#endif
+
+PRCTL_INTERCEPTOR(int, prctl, int option, unsigned long arg2, unsigned long arg3,
             unsigned long arg4, unsigned long arg5) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, prctl, option, arg2, arg3, arg4, arg5);