[compiler-rt] 7e946d0 - [compiler-rt][Darwin] Disable EXC_GUARD exceptions

[Julian Lettner via llvm-commits]

Author: Julian Lettner
Date: 2020-07-29T11:21:25-07:00
New Revision: 7e946d0c8289ff8cafcae88595b805ec511db6b4

URL: https://github.com/llvm/llvm-project/commit/7e946d0c8289ff8cafcae88595b805ec511db6b4
DIFF: https://github.com/llvm/llvm-project/commit/7e946d0c8289ff8cafcae88595b805ec511db6b4.diff

LOG: [compiler-rt][Darwin] Disable EXC_GUARD exceptions

ASan/TSan use mmap in a way that creates “deallocation gaps” which
triggers EXC_GUARD exceptions on macOS 10.15+ (XNU 19.0+).  Let's
suppress those.

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

Removed: 
    


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diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
index f96f18713197..5b06fee62c13 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
@@ -831,6 +831,19 @@ void SignalContext::InitPcSpBp() {
   GetPcSpBp(context, &pc, &sp, &bp);
 }
 
+// ASan/TSan use mmap in a way that creates “deallocation gaps” which triggers
+// EXC_GUARD exceptions on macOS 10.15+ (XNU 19.0+).
+static void DisableMmapExcGuardExceptions() {
+  using task_exc_guard_behavior_t = uint32_t;
+  using task_set_exc_guard_behavior_t =
+      kern_return_t(task_t task, task_exc_guard_behavior_t behavior);
+  auto *set_behavior = (task_set_exc_guard_behavior_t *)dlsym(
+      RTLD_DEFAULT, "task_set_exc_guard_behavior");
+  if (set_behavior == nullptr) return;
+  const task_exc_guard_behavior_t task_exc_guard_none = 0;
+  set_behavior(mach_task_self(), task_exc_guard_none);
+}
+
 void InitializePlatformEarly() {
   // Only use xnu_fast_mmap when on x86_64 and the kernel supports it.
   use_xnu_fast_mmap =
@@ -839,6 +852,8 @@ void InitializePlatformEarly() {
 #else
       false;
 #endif
+  if (GetDarwinKernelVersion() >= DarwinKernelVersion(19, 0))
+    DisableMmapExcGuardExceptions();
 }
 
 #if !SANITIZER_GO