From 22c91ae0bb3a9b213e2bbb342f3e4ade85d702ec Mon Sep 17 00:00:00 2001
From: Christopher Ferris <cferris1000@users.noreply.github.com>
Date: Mon, 10 Nov 2025 16:22:27 -0800
Subject: [PATCH] Revert "[scudo] Small cleanup of memory tagging code.
 (#166860)"

This reverts commit 046ae855360614c5980d0ced0c55b5de507bd9ad.
---
 compiler-rt/lib/scudo/standalone/combined.h                | 3 ++-
 compiler-rt/lib/scudo/standalone/memtag.h                  | 7 ++++---
 compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp     | 1 +
 compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp  | 4 +++-
 .../lib/scudo/standalone/tests/wrappers_cpp_test.cpp       | 3 ++-
 5 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index 2d0f4f53d2ac5..ffe9554203241 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -171,7 +171,8 @@ class Allocator {
       Primary.Options.set(OptionBit::DeallocTypeMismatch);
     if (getFlags()->delete_size_mismatch)
       Primary.Options.set(OptionBit::DeleteSizeMismatch);
-    if (systemSupportsMemoryTagging())
+    if (allocatorSupportsMemoryTagging<AllocatorConfig>() &&
+        systemSupportsMemoryTagging())
       Primary.Options.set(OptionBit::UseMemoryTagging);
 
     QuarantineMaxChunkSize =
diff --git a/compiler-rt/lib/scudo/standalone/memtag.h b/compiler-rt/lib/scudo/standalone/memtag.h
index 52897b3dca6ae..83ebe676433eb 100644
--- a/compiler-rt/lib/scudo/standalone/memtag.h
+++ b/compiler-rt/lib/scudo/standalone/memtag.h
@@ -66,8 +66,7 @@ inline bool systemSupportsMemoryTagging() {
 #ifndef HWCAP2_MTE
 #define HWCAP2_MTE (1 << 18)
 #endif
-  static bool SupportsMemoryTagging = getauxval(AT_HWCAP2) & HWCAP2_MTE;
-  return SupportsMemoryTagging;
+  return getauxval(AT_HWCAP2) & HWCAP2_MTE;
 }
 
 inline bool systemDetectsMemoryTagFaultsTestOnly() {
@@ -262,7 +261,9 @@ inline uptr loadTag(uptr Ptr) {
 
 #else
 
-inline bool systemSupportsMemoryTagging() { return false; }
+inline NORETURN bool systemSupportsMemoryTagging() {
+  UNREACHABLE("memory tagging not supported");
+}
 
 inline NORETURN bool systemDetectsMemoryTagFaultsTestOnly() {
   UNREACHABLE("memory tagging not supported");
diff --git a/compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp b/compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp
index d0d93316f212e..09093e11452dd 100644
--- a/compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp
@@ -28,6 +28,7 @@ TEST(MemtagBasicDeathTest, Unsupported) {
   EXPECT_DEATH(untagPointer((uptr)0), "not supported");
   EXPECT_DEATH(extractTag((uptr)0), "not supported");
 
+  EXPECT_DEATH(systemSupportsMemoryTagging(), "not supported");
   EXPECT_DEATH(systemDetectsMemoryTagFaultsTestOnly(), "not supported");
   EXPECT_DEATH(enableSystemMemoryTaggingTestOnly(), "not supported");
 
diff --git a/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp b/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp
index 8741c8299b57c..855a3e6e6109f 100644
--- a/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp
@@ -27,7 +27,9 @@
 const scudo::uptr PageSize = scudo::getPageSizeCached();
 
 template <typename Config> static scudo::Options getOptionsForConfig() {
-  if (!scudo::systemSupportsMemoryTagging())
+  if (!Config::getMaySupportMemoryTagging() ||
+      !scudo::archSupportsMemoryTagging() ||
+      !scudo::systemSupportsMemoryTagging())
     return {};
   scudo::AtomicOptions AO;
   AO.set(scudo::OptionBit::UseMemoryTagging);
diff --git a/compiler-rt/lib/scudo/standalone/tests/wrappers_cpp_test.cpp b/compiler-rt/lib/scudo/standalone/tests/wrappers_cpp_test.cpp
index 84359251a02aa..c802ed22fbad0 100644
--- a/compiler-rt/lib/scudo/standalone/tests/wrappers_cpp_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/wrappers_cpp_test.cpp
@@ -187,7 +187,8 @@ TEST_F(ScudoWrappersCppTest, ThreadedNew) {
   // TODO: Investigate why libc sometimes crashes with tag missmatch in
   // __pthread_clockjoin_ex.
   std::unique_ptr<scudo::ScopedDisableMemoryTagChecks> NoTags;
-  if (!SCUDO_ANDROID && scudo::systemSupportsMemoryTagging())
+  if (!SCUDO_ANDROID && scudo::archSupportsMemoryTagging() &&
+      scudo::systemSupportsMemoryTagging())
     NoTags = std::make_unique<scudo::ScopedDisableMemoryTagChecks>();
 
   Ready = false;