diff --git a/compiler-rt/lib/scudo/standalone/memtag.h b/compiler-rt/lib/scudo/standalone/memtag.h
--- a/compiler-rt/lib/scudo/standalone/memtag.h
+++ b/compiler-rt/lib/scudo/standalone/memtag.h
@@ -172,6 +172,7 @@
 
 inline uptr addFixedTag(uptr Ptr, uptr Tag) {
   DCHECK_LT(Tag, 16);
+  DCHECK_EQ(untagPointer(Ptr), Ptr);
   return Ptr | (Tag << 56);
 }
 
diff --git a/compiler-rt/lib/scudo/standalone/tests/CMakeLists.txt b/compiler-rt/lib/scudo/standalone/tests/CMakeLists.txt
--- a/compiler-rt/lib/scudo/standalone/tests/CMakeLists.txt
+++ b/compiler-rt/lib/scudo/standalone/tests/CMakeLists.txt
@@ -88,6 +88,7 @@
   flags_test.cpp
   list_test.cpp
   map_test.cpp
+  memtag_test.cpp
   mutex_test.cpp
   primary_test.cpp
   quarantine_test.cpp
diff --git a/compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp b/compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/lib/scudo/standalone/tests/memtag_test.cpp
@@ -0,0 +1,186 @@
+//===-- memtag_test.cpp -----------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "common.h"
+#include "memtag.h"
+#include "platform.h"
+#include "tests/scudo_unit_test.h"
+
+#if SCUDO_LINUX
+namespace scudo {
+
+TEST(MemtagBasicTest, Unsupported) {
+  if (archSupportsMemoryTagging())
+    GTEST_SKIP();
+
+  EXPECT_DEATH(archMemoryTagGranuleSize(), "not supported");
+  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");
+
+  EXPECT_DEATH(selectRandomTag((uptr)0, 0), "not supported");
+  EXPECT_DEATH(addFixedTag((uptr)0, 1), "not supported");
+  EXPECT_DEATH(storeTags((uptr)0, (uptr)0 + sizeof(0)), "not supported");
+  EXPECT_DEATH(storeTag((uptr)0), "not supported");
+  EXPECT_DEATH(loadTag((uptr)0), "not supported");
+
+  EXPECT_DEATH(setRandomTag(nullptr, 64, 0, nullptr, nullptr), "not supported");
+  EXPECT_DEATH(untagPointer(nullptr), "not supported");
+  EXPECT_DEATH(loadTag(nullptr), "not supported");
+  EXPECT_DEATH(addFixedTag(nullptr, 0), "not supported");
+}
+
+class MemtagTest : public ::testing::Test {
+protected:
+  void SetUp() override {
+    if (!archSupportsMemoryTagging() || !systemDetectsMemoryTagFaultsTestOnly())
+      GTEST_SKIP() << "Memory tagging is not supported";
+
+    BufferSize = getPageSizeCached();
+    Buffer = reinterpret_cast<u8 *>(
+        map(nullptr, BufferSize, "MemtagTest", MAP_MEMTAG, &Data));
+    Addr = reinterpret_cast<uptr>(Buffer);
+    EXPECT_TRUE(isAligned(Addr, archMemoryTagGranuleSize()));
+    EXPECT_EQ(Addr, untagPointer(Addr));
+  }
+
+  void TearDown() override {
+    if (Buffer)
+      unmap(Buffer, BufferSize, 0, &Data);
+  }
+
+  uptr BufferSize = 0;
+  MapPlatformData Data = {};
+  u8 *Buffer = nullptr;
+  uptr Addr = 0;
+};
+
+TEST_F(MemtagTest, ArchMemoryTagGranuleSize) {
+  EXPECT_GT(archMemoryTagGranuleSize(), 1u);
+  EXPECT_TRUE(isPowerOfTwo(archMemoryTagGranuleSize()));
+}
+
+TEST_F(MemtagTest, ExtractTag) {
+  uptr Tags = 0;
+  // Try all value for the top byte and check the tags values are in the
+  // expected range.
+  for (u64 Top = 0; Top < 0x100; ++Top)
+    Tags = Tags | (1u << extractTag(Addr | (Top << 56)));
+  EXPECT_EQ(0xffff, Tags);
+}
+
+TEST_F(MemtagTest, AddFixedTag) {
+  for (uptr Tag = 0; Tag < 0x10; ++Tag)
+    EXPECT_EQ(Tag, extractTag(addFixedTag(Addr, Tag)));
+  if (SCUDO_DEBUG) {
+    EXPECT_DEBUG_DEATH(addFixedTag(Addr, 16), "");
+    EXPECT_DEBUG_DEATH(addFixedTag(~Addr, 0), "");
+  }
+}
+
+TEST_F(MemtagTest, UntagPointer) {
+  uptr UnTagMask = untagPointer(~uptr(0));
+  for (u64 Top = 0; Top < 0x100; ++Top) {
+    uptr Ptr = (Addr | (Top << 56)) & UnTagMask;
+    EXPECT_EQ(addFixedTag(Ptr, 0), untagPointer(Ptr));
+  }
+}
+
+TEST_F(MemtagTest, ScopedDisableMemoryTagChecks) {
+  u8 *P = reinterpret_cast<u8 *>(addFixedTag(Addr, 1));
+  EXPECT_NE(P, Buffer);
+
+  EXPECT_DEATH(*P = 20, "");
+  ScopedDisableMemoryTagChecks Disable;
+  *P = 10;
+}
+
+TEST_F(MemtagTest, SelectRandomTag) {
+  for (uptr SrcTag = 0; SrcTag < 0x10; ++SrcTag) {
+    uptr Ptr = addFixedTag(Addr, SrcTag);
+    uptr Tags = 0;
+    for (uptr I = 0; I < 100000; ++I)
+      Tags = Tags | (1u << extractTag(selectRandomTag(Ptr, 0)));
+    EXPECT_EQ(0xfffe, Tags);
+  }
+}
+
+TEST_F(MemtagTest, SelectRandomTagWithMask) {
+  for (uptr j = 0; j < 32; ++j) {
+    for (uptr i = 0; i < 1000; ++i)
+      EXPECT_NE(j, extractTag(selectRandomTag(Addr, 1ull << j)));
+  }
+}
+
+TEST_F(MemtagTest, SKIP_NO_DEBUG(LoadStoreTagUnaligned)) {
+  for (uptr P = Addr; P < Addr + 4 * archMemoryTagGranuleSize(); ++P) {
+    if (P % archMemoryTagGranuleSize() == 0)
+      continue;
+    EXPECT_DEBUG_DEATH(loadTag(P), "");
+    EXPECT_DEBUG_DEATH(storeTag(P), "");
+  }
+}
+
+TEST_F(MemtagTest, LoadStoreTag) {
+  uptr Base = Addr + 0x100;
+  uptr Tagged = addFixedTag(Base, 7);
+  storeTag(Tagged);
+
+  EXPECT_EQ(Base - archMemoryTagGranuleSize(),
+            loadTag(Base - archMemoryTagGranuleSize()));
+  EXPECT_EQ(Tagged, loadTag(Base));
+  EXPECT_EQ(Base + archMemoryTagGranuleSize(),
+            loadTag(Base + archMemoryTagGranuleSize()));
+}
+
+TEST_F(MemtagTest, SKIP_NO_DEBUG(StoreTagsUnaligned)) {
+  for (uptr P = Addr; P < Addr + 4 * archMemoryTagGranuleSize(); ++P) {
+    uptr Tagged = addFixedTag(P, 5);
+    if (Tagged % archMemoryTagGranuleSize() == 0)
+      continue;
+    EXPECT_DEBUG_DEATH(storeTags(Tagged, Tagged), "");
+  }
+}
+
+TEST_F(MemtagTest, StoreTags) {
+  const uptr MaxTaggedSize = 4 * archMemoryTagGranuleSize();
+  for (uptr Size = 0; Size <= MaxTaggedSize; ++Size) {
+    uptr NoTagBegin = Addr + archMemoryTagGranuleSize();
+    uptr NoTagEnd = NoTagBegin + Size;
+
+    u8 Tag = 5;
+
+    uptr TaggedBegin = addFixedTag(NoTagBegin, Tag);
+    uptr TaggedEnd = addFixedTag(NoTagEnd, Tag);
+
+    EXPECT_EQ(roundUpTo(TaggedEnd, archMemoryTagGranuleSize()),
+              storeTags(TaggedBegin, TaggedEnd));
+
+    uptr LoadPtr = Addr;
+    // Untagged left granule.
+    EXPECT_EQ(LoadPtr, loadTag(LoadPtr));
+
+    for (LoadPtr += archMemoryTagGranuleSize(); LoadPtr < NoTagEnd;
+         LoadPtr += archMemoryTagGranuleSize()) {
+      EXPECT_EQ(addFixedTag(LoadPtr, 5), loadTag(LoadPtr));
+    }
+
+    // Untagged right granule.
+    EXPECT_EQ(LoadPtr, loadTag(LoadPtr));
+
+    // Reset tags without using StoreTags.
+    releasePagesToOS(Addr, 0, BufferSize, &Data);
+  }
+}
+
+} // namespace scudo
+
+#endif
diff --git a/compiler-rt/lib/scudo/standalone/tests/scudo_unit_test.h b/compiler-rt/lib/scudo/standalone/tests/scudo_unit_test.h
--- a/compiler-rt/lib/scudo/standalone/tests/scudo_unit_test.h
+++ b/compiler-rt/lib/scudo/standalone/tests/scudo_unit_test.h
@@ -39,4 +39,10 @@
 #define SKIP_ON_FUCHSIA(T) T
 #endif
 
+#if SCUDO_DEBUG
+#define SKIP_NO_DEBUG(T) T
+#else
+#define SKIP_NO_DEBUG(T) DISABLED_##T
+#endif
+
 extern bool UseQuarantine;