Make MTE tests pass with all values of MEMTAG_OPTIONS.

Do not assume that tests start with Sync MTE; check the initial setting
and change test logic as appropriate.

Bug: 192480262
Test: bionic-unit-tests with MEMTAG_OPTIONS=(off|sync|async)
Merged-In: Id80301e6426af16f89bd80a7a7ab127b6fd60425
Change-Id: Id80301e6426af16f89bd80a7a7ab127b6fd60425
(cherry picked from commit 53df1f3772ad4843461e78540111b21e9061c051)

3 files changed, 20 insertions, 10 deletions

diff --git a/tests/heap_tagging_level_test.cpp b/tests/heap_tagging_level_test.cpp
index b3c8f22a9..5f5904f9a 100644
--- a/tests/heap_tagging_level_test.cpp
+++ b/tests/heap_tagging_level_test.cpp
@@ -86,16 +86,15 @@ void ExitWithSiCode(int, siginfo_t* info, void*) {
 
 TEST(heap_tagging_level, sync_async_bad_accesses_die) {
 #if defined(__BIONIC__) && defined(__aarch64__)
-  if (!(getauxval(AT_HWCAP2) & HWCAP2_MTE)) {
-    GTEST_SKIP() << "requires MTE support";
+  if (!mte_supported() || !running_with_mte()) {
+    GTEST_SKIP() << "requires MTE to be enabled";
   }
 
   std::unique_ptr<int[]> p = std::make_unique<int[]>(4);
 
-  // First, check that memory tagging is enabled and the default tag checking level is sync.
-  // cc_test targets get sync MTE by default.
   // We assume that scudo is used on all MTE enabled hardware; scudo inserts a header with a
   // mismatching tag before each allocation.
+  EXPECT_TRUE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_SYNC));
   EXPECT_EXIT(
       {
         ScopedSignalHandler ssh(SIGSEGV, ExitWithSiCode, SA_SIGINFO);
@@ -136,7 +135,7 @@ TEST(heap_tagging_level, tagging_level_transitions) {
 
   EXPECT_FALSE(SetHeapTaggingLevel(static_cast<HeapTaggingLevel>(12345)));
 
-  if (mte_supported()) {
+  if (mte_supported() && running_with_mte()) {
     // ASYNC -> ...
     EXPECT_FALSE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_TBI));
     EXPECT_TRUE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_ASYNC));
@@ -146,14 +145,14 @@ TEST(heap_tagging_level, tagging_level_transitions) {
     EXPECT_FALSE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_TBI));
     EXPECT_TRUE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_SYNC));
     EXPECT_TRUE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_ASYNC));
-  } else {
+  } else if (!mte_supported()) {
     // TBI -> ...
     EXPECT_TRUE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_TBI));
     EXPECT_FALSE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_ASYNC));
     EXPECT_FALSE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_SYNC));
   }
 
-  // TBI -> NONE on non-MTE, ASYNC -> NONE on MTE.
+  // TBI -> NONE on non-MTE, ASYNC|SYNC|NONE -> NONE on MTE.
   EXPECT_TRUE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_NONE));
 
   // NONE -> ...
@@ -170,8 +169,8 @@ TEST(heap_tagging_level, tagging_level_transition_sync_none) {
 #if defined(__BIONIC__) && defined(__aarch64__)
   // We can't test SYNC -> NONE in tagging_level_transitions because we can only make one transition
   // to NONE (which we use to test ASYNC -> NONE), so we test it here separately.
-  if (!mte_supported()) {
-    GTEST_SKIP() << "requires MTE support";
+  if (!mte_supported() || !running_with_mte()) {
+    GTEST_SKIP() << "requires MTE to be enabled";
   }
 
   EXPECT_TRUE(SetHeapTaggingLevel(M_HEAP_TAGGING_LEVEL_SYNC));
diff --git a/tests/mte_test.cpp b/tests/mte_test.cpp
index f329d8d70..ade95326c 100644
--- a/tests/mte_test.cpp
+++ b/tests/mte_test.cpp
@@ -38,7 +38,7 @@ static void test_tag_mismatch() {
 #endif
   }
 #if defined(__aarch64__)
-  if (mte_supported()) {
+  if (mte_supported() && running_with_mte()) {
     EXPECT_DEATH(
         {
           volatile int load ATTRIBUTE_UNUSED = *mistagged_p;
diff --git a/tests/utils.h b/tests/utils.h
index 145ba1ac2..592ac0e56 100644
--- a/tests/utils.h
+++ b/tests/utils.h
@@ -21,6 +21,7 @@
 #include <fcntl.h>
 #include <inttypes.h>
 #include <sys/mman.h>
+#include <sys/prctl.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -304,3 +305,13 @@ template <class Tp>
 static inline void DoNotOptimize(Tp& value) {
   asm volatile("" : "+r,m"(value) : : "memory");
 }
+
+static inline bool running_with_mte() {
+#ifdef __aarch64__
+  int level = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+  return level >= 0 && (level & PR_TAGGED_ADDR_ENABLE) &&
+         (level & PR_MTE_TCF_MASK) != PR_MTE_TCF_NONE;
+#else
+  return false;
+#endif
+}