Expose __hwasan_tag_mismatch_stub

Summary:
GCC would like to emit a function call to report a tag mismatch
rather than hard-code the `brk` instruction directly.

__hwasan_tag_mismatch_stub contains most of the functionality to do
this already, but requires exposure in the dynamic library.

This patch moves __hwasan_tag_mismatch_stub outside of the anonymous
namespace that it was defined in and declares it in
hwasan_interface_internal.h.

We also add the ability to pass sizes larger than 16 bytes to this
reporting function by providing a fourth parameter that is only looked
at when the size provided is not in the original accepted range.

This does not change the behaviour where it is already being called,
since the previous definition only accepted sizes up to 16 bytes and
hence the change in behaviour is not seen by existing users.
The change in declaration does not matter, since the only existing use
is in the __hwasan_tag_mismatch function written in assembly.

Tested with gcc and clang on an AArch64 vm.

Reviewers: eugenis, kcc, pcc, #sanitizers

Reviewed By: eugenis, #sanitizers

Subscribers: kristof.beyls, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D69113

compiler-rt/lib/hwasan/hwasan_interface_internal.h

@@ -111,6 +111,10 @@ uptr __hwasan_tag_pointer(uptr p, u8 tag);
 SANITIZER_INTERFACE_ATTRIBUTE
 void __hwasan_tag_mismatch(uptr addr, u8 ts);
 
+SANITIZER_INTERFACE_ATTRIBUTE
+void __hwasan_tag_mismatch4(uptr addr, uptr access_info, uptr *registers_frame,
+                            size_t outsize);
+
 SANITIZER_INTERFACE_ATTRIBUTE
 u8 __hwasan_generate_tag();
 

compiler-rt/lib/hwasan/hwasan_linux.cpp

@@ -460,21 +460,6 @@ static bool HwasanOnSIGTRAP(int signo, siginfo_t *info, ucontext_t *uc) {
   return true;
 }
 
-// Entry point stub for interoperability between __hwasan_tag_mismatch (ASM) and
-// the rest of the mismatch handling code (C++).
-extern "C" void __hwasan_tag_mismatch_stub(uptr addr, uptr access_info,
-                                           uptr *registers_frame) {
-  AccessInfo ai;
-  ai.is_store = access_info & 0x10;
-  ai.recover = false;
-  ai.addr = addr;
-  ai.size = 1 << (access_info & 0xf);
-
-  HandleTagMismatch(ai, (uptr)__builtin_return_address(0),
-                    (uptr)__builtin_frame_address(0), nullptr, registers_frame);
-  __builtin_unreachable();
-}
-
 static void OnStackUnwind(const SignalContext &sig, const void *,
                           BufferedStackTrace *stack) {
   stack->Unwind(StackTrace::GetNextInstructionPc(sig.pc), sig.bp, sig.context,
@@ -493,4 +478,24 @@ void HwasanOnDeadlySignal(int signo, void *info, void *context) {
 
 } // namespace __hwasan
 
+// Entry point for interoperability between __hwasan_tag_mismatch (ASM) and the
+// rest of the mismatch handling code (C++).
+void __hwasan_tag_mismatch4(uptr addr, uptr access_info, uptr *registers_frame,
+                            size_t outsize) {
+  __hwasan::AccessInfo ai;
+  ai.is_store = access_info & 0x10;
+  ai.is_load = !ai.is_store;
+  ai.recover = access_info & 0x20;
+  ai.addr = addr;
+  if ((access_info & 0xf) == 0xf)
+    ai.size = outsize;
+  else
+    ai.size = 1 << (access_info & 0xf);
+
+  __hwasan::HandleTagMismatch(ai, (uptr)__builtin_return_address(0),
+                              (uptr)__builtin_frame_address(0), nullptr,
+                              registers_frame);
+  __builtin_unreachable();
+}
+
 #endif // SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_NETBSD

compiler-rt/lib/hwasan/hwasan_tag_mismatch_aarch64.S

@@ -135,12 +135,12 @@ __hwasan_tag_mismatch_v2:
   stp     x4,  x5,  [sp, #32]
   stp     x2,  x3,  [sp, #16]
 
-  // Pass the address of the frame to __hwasan_tag_mismatch_stub, so that it can
+  // Pass the address of the frame to __hwasan_tag_mismatch4, so that it can
   // extract the saved registers from this frame without having to worry about
   // finding this frame.
   mov x2, sp
 
-  bl __hwasan_tag_mismatch_stub
+  bl __hwasan_tag_mismatch4
   CFI_ENDPROC
 
 .Lfunc_end0: