[sanitizer_common][tsan][Darwin] Improve message for unsupported vm config on Apple platforms

[ndrewh]

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

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[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Andrew Haberlandt (ndrewh)

Changes

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

---

Full diff: https://github.com/llvm/llvm-project/pull/158665.diff

3 Files Affected:

• (modified) compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp (+23)
• (modified) compiler-rt/lib/sanitizer_common/sanitizer_mac.h (+2)
• (modified) compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp (+13-3)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
index d4811ff4ed217..bf861063ca1f5 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
@@ -1298,6 +1298,29 @@ 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..84dfe999045f9 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()) {
+    Printf(
+        "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.
+  else if (IsAddressInMappedRegion(HiAppMemEnd() - 1)) {
+    Printf(
+        "ThreadSanitizer: Unsupported virtual memory layout: Address %p is "
+        "already mapped.\n");
     Die();
   }
 #endif

[DanBlackwell]

Let me know what your thoughts are with respect to printf vs report for the fatal paths. Happy to merge this for you afterwards; this is a useful contribution!

[DanBlackwell]

@ndrewh let me know if you want this merging and I'll hit the button for you.

[ndrewh]

good with me to merge @DanBlackwell

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