chromium/chromium-115-revert-ifunc.patch

commit b2c4ff8d5d8cdbf2487363a5b8d68b6485706069
Author: Richard Townsend <Richard.Townsend@arm.com>
Date:   Thu May 18 22:51:36 2023 +0000

    Reland "Reland "mte: refactor the tagging functions to use ifuncs""
    
    This is a reland of commit 2321ea383c006149c3b496a515f54fb3aebdc34c
    and a revert of commit adfb1c2c6ceb3daf210cef1e5688541ebc561e20. It
    was reverted because of a problem with android-arm64 orderfile
    generation, which is now resolved.
    
    Original change's description:
    > Reland "mte: refactor the tagging functions to use ifuncs"
    >
    > This was reverted due to a toolchain problem affecting ThinLTO,
    > resolved in [1]
    >
    > [1] https://reviews.llvm.org/D144982
    >
    > This reverts commit 6c22e41fc3ffd305359f17b2423c37c2c976acf3.
    >
    > Bug: 1137393
    > Change-Id: I991e12618f98cdf8b89ec83cad06e30ad60d332e
    > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4473870
    > Reviewed-by: Keishi Hattori <keishi@chromium.org>
    > Commit-Queue: Richard Townsend <richard.townsend@arm.com>
    > Cr-Commit-Position: refs/heads/main@{#1135862}
    
    Bug: 1137393, 1440531
    Change-Id: I4cd1911a36cf55ee1c06e6ffda971866c93fa741
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4517702
    Commit-Queue: Richard Townsend <richard.townsend@arm.com>
    Reviewed-by: Keishi Hattori <keishi@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#1146244}

diff --git a/base/allocator/partition_allocator/partition_root.cc b/base/allocator/partition_allocator/partition_root.cc
index 486594e81f823..8ab37f6dec750 100644
--- a/base/allocator/partition_allocator/partition_root.cc
+++ b/base/allocator/partition_allocator/partition_root.cc
@@ -869,10 +869,6 @@ void PartitionRoot<thread_safe>::Init(PartitionOptions opts) {
       return;
     }
 
-    // Swaps out the active no-op tagging intrinsics with MTE-capable ones, if
-    // running on the right hardware.
-    ::partition_alloc::internal::InitializeMTESupportIfNeeded();
-
 #if BUILDFLAG(HAS_64_BIT_POINTERS)
     // Reserve address space for partition alloc.
     internal::PartitionAddressSpace::Init();
diff --git a/base/allocator/partition_allocator/tagging.cc b/base/allocator/partition_allocator/tagging.cc
index a8a74155de4e1..ea7ac2af82c88 100644
--- a/base/allocator/partition_allocator/tagging.cc
+++ b/base/allocator/partition_allocator/tagging.cc
@@ -12,7 +12,9 @@
 
 #if PA_CONFIG(HAS_MEMORY_TAGGING)
 #include <arm_acle.h>
+#include <asm/hwcap.h>
 #include <sys/auxv.h>
+#include <sys/ifunc.h>
 #include <sys/prctl.h>
 #define PR_SET_TAGGED_ADDR_CTRL 55
 #define PR_GET_TAGGED_ADDR_CTRL 56
@@ -119,12 +121,6 @@ namespace {
   return ret;
 }
 
-#if PA_CONFIG(HAS_MEMORY_TAGGING)
-static bool HasCPUMemoryTaggingExtension() {
-  return base::CPU::GetInstanceNoAllocation().has_mte();
-}
-#endif  // PA_CONFIG(HAS_MEMORY_TAGGING)
-
 #if PA_CONFIG(HAS_MEMORY_TAGGING)
 void* TagRegionRandomlyForMTE(void* ptr, size_t sz, uint64_t mask) {
   // Randomly tag a region (MTE-enabled systems only). The first 16-byte
@@ -166,7 +162,6 @@ void* RemaskVoidPtrForMTE(void* ptr) {
   }
   return nullptr;
 }
-#endif
 
 void* TagRegionIncrementNoOp(void* ptr, size_t sz) {
   // Region parameters are checked even on non-MTE systems to check the
@@ -183,24 +178,49 @@ void* TagRegionRandomlyNoOp(void* ptr, size_t sz, uint64_t mask) {
 void* RemaskVoidPtrNoOp(void* ptr) {
   return ptr;
 }
+#endif
 
 }  // namespace
 
-void InitializeMTESupportIfNeeded() {
 #if PA_CONFIG(HAS_MEMORY_TAGGING)
-  if (HasCPUMemoryTaggingExtension()) {
-    global_remask_void_ptr_fn = RemaskVoidPtrForMTE;
-    global_tag_memory_range_increment_fn = TagRegionIncrementForMTE;
-    global_tag_memory_range_randomly_fn = TagRegionRandomlyForMTE;
+using RemaskPtrInternalFn = void*(void* ptr);
+using TagMemoryRangeIncrementInternalFn = void*(void* ptr, size_t size);
+
+using TagMemoryRangeRandomlyInternalFn = void*(void* ptr,
+                                               size_t size,
+                                               uint64_t mask);
+
+extern "C" TagMemoryRangeIncrementInternalFn(
+    *ResolveTagMemoryRangeIncrement(uint64_t hwcap, struct __ifunc_arg_t* hw)) {
+  if ((hwcap & _IFUNC_ARG_HWCAP) && (hw->_hwcap2 & HWCAP2_MTE)) {
+    return TagRegionIncrementForMTE;
   }
-#endif
+  return TagRegionIncrementNoOp;
+}
+
+extern "C" TagMemoryRangeRandomlyInternalFn(
+    *ResolveTagMemoryRandomly(uint64_t hwcap, struct __ifunc_arg_t* hw)) {
+  if ((hwcap & _IFUNC_ARG_HWCAP) && (hw->_hwcap2 & HWCAP2_MTE)) {
+    return TagRegionRandomlyForMTE;
+  }
+  return TagRegionRandomlyNoOp;
+}
+
+extern "C" RemaskPtrInternalFn(
+    *ResolveRemaskPointer(uint64_t hwcap, struct __ifunc_arg_t* hw)) {
+  if ((hwcap & _IFUNC_ARG_HWCAP) && (hw->_hwcap2 & HWCAP2_MTE)) {
+    return RemaskVoidPtrForMTE;
+  }
+  return RemaskVoidPtrNoOp;
 }
 
-RemaskPtrInternalFn* global_remask_void_ptr_fn = RemaskVoidPtrNoOp;
-TagMemoryRangeIncrementInternalFn* global_tag_memory_range_increment_fn =
-    TagRegionIncrementNoOp;
-TagMemoryRangeRandomlyInternalFn* global_tag_memory_range_randomly_fn =
-    TagRegionRandomlyNoOp;
+void* TagMemoryRangeIncrementInternal(void* ptr, size_t size)
+    __attribute__((ifunc("ResolveTagMemoryRangeIncrement")));
+void* TagMemoryRangeRandomlyInternal(void* ptr, size_t size, uint64_t mask)
+    __attribute__((ifunc("ResolveTagMemoryRandomly")));
+void* RemaskPointerInternal(void* ptr)
+    __attribute__((ifunc("ResolveRemaskPointer")));
+#endif // PA_CONFIG(HAS_MEMORY_TAGGING)
 
 TagViolationReportingMode GetMemoryTaggingModeForCurrentThread() {
 #if PA_CONFIG(HAS_MEMORY_TAGGING)
diff --git a/base/allocator/partition_allocator/tagging.h b/base/allocator/partition_allocator/tagging.h
index af914452b1162..d49e062ce6319 100644
--- a/base/allocator/partition_allocator/tagging.h
+++ b/base/allocator/partition_allocator/tagging.h
@@ -55,32 +55,16 @@ void ChangeMemoryTaggingModeForAllThreadsPerProcess(TagViolationReportingMode);
 PA_COMPONENT_EXPORT(PARTITION_ALLOC)
 TagViolationReportingMode GetMemoryTaggingModeForCurrentThread();
 
-// Called by the partition allocator after initial startup, this detects MTE
-// support in the current CPU and replaces the active tagging intrinsics with
-// MTE versions if needed.
-PA_COMPONENT_EXPORT(PARTITION_ALLOC) void InitializeMTESupportIfNeeded();
-
-// These global function pointers hold the implementations of the tagging
-// intrinsics (TagMemoryRangeRandomly, TagMemoryRangeIncrement, RemaskPtr).
-// They are designed to be callable without taking a branch. They are initially
-// set to no-op functions in tagging.cc, but can be replaced with MTE-capable
-// ones through InitializeMTEIfNeeded(). This is conceptually similar to an
-// IFUNC, even though less secure. These function pointers were introduced to
-// support older Android releases. With the removal of support for Android M,
-// it became possible to use IFUNC instead.
-// TODO(bartekn): void* -> uintptr_t
-using RemaskPtrInternalFn = void*(void* ptr);
-using TagMemoryRangeIncrementInternalFn = void*(void* ptr, size_t size);
-
-using TagMemoryRangeRandomlyInternalFn = void*(void* ptr,
-                                               size_t size,
-                                               uint64_t mask);
-extern PA_COMPONENT_EXPORT(PARTITION_ALLOC)
-    TagMemoryRangeRandomlyInternalFn* global_tag_memory_range_randomly_fn;
-extern PA_COMPONENT_EXPORT(PARTITION_ALLOC)
-    TagMemoryRangeIncrementInternalFn* global_tag_memory_range_increment_fn;
-extern PA_COMPONENT_EXPORT(PARTITION_ALLOC)
-    RemaskPtrInternalFn* global_remask_void_ptr_fn;
+// These forward-defined functions do not really exist in tagging.cc, they're resolved
+// by the dynamic linker to MTE-capable versions on the right hardware.
+#if PA_CONFIG(HAS_MEMORY_TAGGING)
+PA_COMPONENT_EXPORT(PARTITION_ALLOC)
+void* TagMemoryRangeIncrementInternal(void* ptr, size_t size);
+PA_COMPONENT_EXPORT(PARTITION_ALLOC)
+void* TagMemoryRangeRandomlyInternal(void* ptr, size_t size, uint64_t mask);
+PA_COMPONENT_EXPORT(PARTITION_ALLOC)
+void* RemaskPointerInternal(void* ptr);
+#endif
 
 // Increments the tag of the memory range ptr. Useful for provable revocations
 // (e.g. free). Returns the pointer with the new tag. Ensures that the entire
@@ -90,7 +74,7 @@ extern PA_COMPONENT_EXPORT(PARTITION_ALLOC)
 template <typename T>
 PA_ALWAYS_INLINE T* TagMemoryRangeIncrement(T* ptr, size_t size) {
 #if PA_CONFIG(HAS_MEMORY_TAGGING)
-  return reinterpret_cast<T*>(global_tag_memory_range_increment_fn(ptr, size));
+  return reinterpret_cast<T*>(TagMemoryRangeIncrementInternal(ptr, size));
 #else
   return ptr;
 #endif
@@ -108,8 +92,7 @@ PA_ALWAYS_INLINE T* TagMemoryRangeRandomly(T* ptr,
                                            size_t size,
                                            uint64_t mask = 0u) {
 #if PA_CONFIG(HAS_MEMORY_TAGGING)
-  return reinterpret_cast<T*>(
-      global_tag_memory_range_randomly_fn(ptr, size, mask));
+  return reinterpret_cast<T*>(TagMemoryRangeRandomlyInternal(ptr, size, mask));
 #else
   return ptr;
 #endif
@@ -124,7 +107,7 @@ PA_ALWAYS_INLINE void* TagMemoryRangeRandomly(uintptr_t ptr,
 template <typename T>
 PA_ALWAYS_INLINE T* TagPtr(T* ptr) {
 #if PA_CONFIG(HAS_MEMORY_TAGGING)
-  return reinterpret_cast<T*>(global_remask_void_ptr_fn(ptr));
+  return reinterpret_cast<T*>(RemaskPointerInternal(ptr));
 #else
   return ptr;
 #endif
diff --git a/base/allocator/partition_allocator/tagging_unittest.cc b/base/allocator/partition_allocator/tagging_unittest.cc
index f3b8532a8f1f4..47f62ac000b43 100644
--- a/base/allocator/partition_allocator/tagging_unittest.cc
+++ b/base/allocator/partition_allocator/tagging_unittest.cc
@@ -16,7 +16,6 @@ namespace partition_alloc::internal {
 
 // Check whether we can call the tagging intrinsics safely on all architectures.
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeRandomlySafe) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),
                  PageAccessibilityConfiguration(
@@ -32,7 +31,6 @@ TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeRandomlySafe) {
 }
 
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeIncrementSafe) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   base::CPU cpu;
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),
@@ -54,7 +52,6 @@ TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeIncrementSafe) {
 #if defined(ARCH_CPU_64_BITS)
 // Size / alignment constraints are only enforced on 64-bit architectures.
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeBadSz) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   base::CPU cpu;
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),
@@ -71,7 +68,6 @@ TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeBadSz) {
 }
 
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeRandomlyNoSz) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   base::CPU cpu;
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),
@@ -87,7 +83,6 @@ TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeRandomlyNoSz) {
 }
 
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeRandomlyBadAlign) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   base::CPU cpu;
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),
@@ -104,7 +99,6 @@ TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeRandomlyBadAlign) {
 }
 
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeIncrementBadSz) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   base::CPU cpu;
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),
@@ -120,7 +114,6 @@ TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeIncrementBadSz) {
 }
 
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeIncrementNoSz) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   base::CPU cpu;
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),
@@ -136,7 +129,6 @@ TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeIncrementNoSz) {
 }
 
 TEST(PartitionAllocMemoryTaggingTest, TagMemoryRangeIncrementBadAlign) {
-  ::partition_alloc::internal::InitializeMTESupportIfNeeded();
   base::CPU cpu;
   uintptr_t buffer =
       AllocPages(PageAllocationGranularity(), PageAllocationGranularity(),