[compiler-rt] 51a840e - [sanitizer_common][tsan][Darwin] Improve message for unsupported vm config on Apple platforms (#158665)

[via llvm-commits]

Author: Andrew Haberlandt
Date: 2025-09-17T16:04:15+01:00
New Revision: 51a840e762f506c2473f9f0cbc01b6336f99e6d1

URL: https://github.com/llvm/llvm-project/commit/51a840e762f506c2473f9f0cbc01b6336f99e6d1
DIFF: https://github.com/llvm/llvm-project/commit/51a840e762f506c2473f9f0cbc01b6336f99e6d1.diff

LOG: [sanitizer_common][tsan][Darwin] Improve message for unsupported vm config on Apple platforms (#158665)

An existing log message is triggered in InitializePlatformEarly if the
address space max is not as sufficient for TSAN.

Some Apple platforms expand the address space limit, but reserve much of
the space TSAN needs. Therefore, we now check that the kernel has not
mapped over the address space that we intend to use.

IsAddressInMappedRegion is added to sanitizer_common. This introduces a
new dependency on mach_vm_region_recurse during TSAN startup, so this
intentionally fails softly (to avoid breaking current users who may be
in a sandbox that doesn't allow this).

rdar://135265279

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
    compiler-rt/lib/sanitizer_common/sanitizer_mac.h
    compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
index c4a6bf5bcbbee..a2e0d56760f4b 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
@@ -1360,6 +1360,29 @@ uptr FindAvailableMemoryRange(uptr size, uptr alignment, uptr left_padding,
   return 0;
 }
 
+// Returns true if the address is definitely mapped, and false if it is not
+// mapped or could not be determined.
+bool IsAddressInMappedRegion(uptr addr) {
+  mach_vm_size_t vmsize = 0;
+  natural_t depth = 0;
+  vm_region_submap_short_info_data_64_t vminfo;
+  mach_msg_type_number_t count = VM_REGION_SUBMAP_SHORT_INFO_COUNT_64;
+  mach_vm_address_t address = addr;
+
+  kern_return_t kr =
+      mach_vm_region_recurse(mach_task_self(), &address, &vmsize, &depth,
+                             (vm_region_info_t)&vminfo, &count);
+
+  if (kr == KERN_DENIED) {
+    Report(
+        "WARN: mach_vm_region_recurse returned KERN_DENIED when checking "
+        "whether an address is mapped.\n");
+    Report("HINT: Is mach_vm_region_recurse allowed by sandbox?\n");
+  }
+
+  return (kr == KERN_SUCCESS && addr >= address && addr < address + vmsize);
+}
+
 // FIXME implement on this platform.
 void GetMemoryProfile(fill_profile_f cb, uptr *stats) {}
 

diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.h b/compiler-rt/lib/sanitizer_common/sanitizer_mac.h
index b0e4ac7f40745..789dd8e4d8e9c 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.h
@@ -76,6 +76,8 @@ struct ThreadEventCallbacks {
 
 void InstallPthreadIntrospectionHook(const ThreadEventCallbacks &callbacks);
 
+bool IsAddressInMappedRegion(uptr addr);
+
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_APPLE

diff  --git a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
index eb344df168ab9..5cc81bab5b911 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
@@ -226,9 +226,19 @@ static void ThreadTerminateCallback(uptr thread) {
 void InitializePlatformEarly() {
 #  if !SANITIZER_GO && SANITIZER_IOS
   uptr max_vm = GetMaxUserVirtualAddress() + 1;
-  if (max_vm != HiAppMemEnd()) {
-    Printf("ThreadSanitizer: unsupported vm address limit %p, expected %p.\n",
-           (void *)max_vm, (void *)HiAppMemEnd());
+  if (max_vm < HiAppMemEnd()) {
+    Report(
+        "ThreadSanitizer: Unsupported virtual memory layout:\n\tVM address "
+        "limit = %p\n\tExpected %p.\n",
+        (void*)max_vm, (void*)HiAppMemEnd());
+    Die();
+  }
+  // In some configurations, the max_vm is expanded, but much of this space is
+  // already mapped. TSAN will not work in this configuration.
+  if (IsAddressInMappedRegion(HiAppMemEnd() - 1)) {
+    Report(
+        "ThreadSanitizer: Unsupported virtual memory layout: Address %p is "
+        "already mapped.\n");
     Die();
   }
 #endif