[compiler-rt] cc4f989 - Normalize ptrauth handling in sanitizer runtime (#100483)

[via llvm-commits]

Author: Anton Korobeynikov
Date: 2024-07-25T11:57:46-07:00
New Revision: cc4f98979b079b517edd8a71f56a8975f436e63d

URL: https://github.com/llvm/llvm-project/commit/cc4f98979b079b517edd8a71f56a8975f436e63d
DIFF: https://github.com/llvm/llvm-project/commit/cc4f98979b079b517edd8a71f56a8975f436e63d.diff

LOG: Normalize ptrauth handling in sanitizer runtime (#100483)

1. Include `ptrauth.h` if `ptrauth_intrinsics` language feature is specified (per ptrauth spec, this is what enables `ptrauh.h` usage and functions like `ptrauth_strip`)
 2. For PAC-RET fallback implement two changes:
    1. Switch to macro, so we can ignore key argument
    2. Ensure the unsigned value is erased from LR, so the possibility of gadget reuse is reduced.

Fixes #100467

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_ptrauth.h

Removed: 
    


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diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_ptrauth.h b/compiler-rt/lib/sanitizer_common/sanitizer_ptrauth.h
index 5200354694851..b5215c0d49c06 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_ptrauth.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_ptrauth.h
@@ -9,31 +9,33 @@
 #ifndef SANITIZER_PTRAUTH_H
 #define SANITIZER_PTRAUTH_H
 
-#if __has_feature(ptrauth_calls)
-#include <ptrauth.h>
+#if __has_feature(ptrauth_intrinsics)
+#  include <ptrauth.h>
 #elif defined(__ARM_FEATURE_PAC_DEFAULT) && !defined(__APPLE__)
-inline unsigned long ptrauth_strip(void* __value, unsigned int __key) {
-  // On the stack the link register is protected with Pointer
-  // Authentication Code when compiled with -mbranch-protection.
-  // Let's stripping the PAC unconditionally because xpaclri is in
-  // the NOP space so will do nothing when it is not enabled or not available.
-  unsigned long ret;
-  asm volatile(
-      "mov x30, %1\n\t"
-      "hint #7\n\t"  // xpaclri
-      "mov %0, x30\n\t"
-      : "=r"(ret)
-      : "r"(__value)
-      : "x30");
-  return ret;
-}
-#define ptrauth_auth_data(__value, __old_key, __old_data) __value
-#define ptrauth_string_discriminator(__string) ((int)0)
+// On the stack the link register is protected with Pointer
+// Authentication Code when compiled with -mbranch-protection.
+// Let's stripping the PAC unconditionally because xpaclri is in
+// the NOP space so will do nothing when it is not enabled or not available.
+#  define ptrauth_strip(__value, __key) \
+    ({                                  \
+      unsigned long ret;                \
+      asm volatile(                     \
+          "mov x30, %1\n\t"             \
+          "hint #7\n\t"                 \
+          "mov %0, x30\n\t"             \
+          "mov x30, xzr\n\t"            \
+          : "=r"(ret)                   \
+          : "r"(__value)                \
+          : "x30");                     \
+      ret;                              \
+    })
+#  define ptrauth_auth_data(__value, __old_key, __old_data) __value
+#  define ptrauth_string_discriminator(__string) ((int)0)
 #else
 // Copied from <ptrauth.h>
-#define ptrauth_strip(__value, __key) __value
-#define ptrauth_auth_data(__value, __old_key, __old_data) __value
-#define ptrauth_string_discriminator(__string) ((int)0)
+#  define ptrauth_strip(__value, __key) __value
+#  define ptrauth_auth_data(__value, __old_key, __old_data) __value
+#  define ptrauth_string_discriminator(__string) ((int)0)
 #endif
 
 #define STRIP_PAC_PC(pc) ((uptr)ptrauth_strip(pc, 0))