Use-after-return sanitizer binary metadata

Currently per-function metadata consists of:
(start-pc, size, features)

This adds a new UAR feature and if it's set an additional element:
(start-pc, size, features, stack-args-size)

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D136078

clang/include/clang/Basic/CodeGenOptions.def

@@ -288,6 +288,8 @@ CODEGENOPT(SanitizeCoverageTraceLoads, 1, 0) ///< Enable tracing of loads.
 CODEGENOPT(SanitizeCoverageTraceStores, 1, 0) ///< Enable tracing of stores.
 CODEGENOPT(SanitizeBinaryMetadataCovered, 1, 0) ///< Emit PCs for covered functions.
 CODEGENOPT(SanitizeBinaryMetadataAtomics, 1, 0) ///< Emit PCs for atomic operations.
+CODEGENOPT(SanitizeBinaryMetadataUAR, 1, 0) ///< Emit PCs for start of functions
+                                            ///< that are subject for use-after-return checking.
 CODEGENOPT(SanitizeStats     , 1, 0) ///< Collect statistics for sanitizers.
 CODEGENOPT(SimplifyLibCalls  , 1, 1) ///< Set when -fbuiltin is enabled.
 CODEGENOPT(SoftFloat         , 1, 0) ///< -soft-float.

clang/include/clang/Basic/CodeGenOptions.h

@@ -497,7 +497,8 @@ public:
 
   // Check if any one of SanitizeBinaryMetadata* is enabled.
   bool hasSanitizeBinaryMetadata() const {
-    return SanitizeBinaryMetadataCovered || SanitizeBinaryMetadataAtomics;
+    return SanitizeBinaryMetadataCovered || SanitizeBinaryMetadataAtomics ||
+           SanitizeBinaryMetadataUAR;
   }
 };
 

clang/include/clang/Driver/Options.td

@@ -5575,6 +5575,10 @@ def fexperimental_sanitize_metadata_EQ_atomics
     : Flag<["-"], "fexperimental-sanitize-metadata=atomics">,
       HelpText<"Emit PCs for atomic operations used by binary analysis sanitizers">,
       MarshallingInfoFlag<CodeGenOpts<"SanitizeBinaryMetadataAtomics">>;
+def fexperimental_sanitize_metadata_EQ_uar
+    : Flag<["-"], "fexperimental-sanitize-metadata=uar">,
+      HelpText<"Emit PCs for start of functions that are subject for use-after-return checking.">,
+      MarshallingInfoFlag<CodeGenOpts<"SanitizeBinaryMetadataUAR">>;
 def fpatchable_function_entry_offset_EQ
     : Joined<["-"], "fpatchable-function-entry-offset=">, MetaVarName<"<M>">,
       HelpText<"Generate M NOPs before function entry">,

clang/lib/CodeGen/BackendUtil.cpp

@@ -234,6 +234,7 @@ getSanitizerBinaryMetadataOptions(const CodeGenOptions &CGOpts) {
   SanitizerBinaryMetadataOptions Opts;
   Opts.Covered = CGOpts.SanitizeBinaryMetadataCovered;
   Opts.Atomics = CGOpts.SanitizeBinaryMetadataAtomics;
+  Opts.UAR = CGOpts.SanitizeBinaryMetadataUAR;
   return Opts;
 }
 

clang/lib/Driver/SanitizerArgs.cpp

@@ -104,6 +104,7 @@ enum CoverageFeature {
 enum BinaryMetadataFeature {
   BinaryMetadataCovered = 1 << 0,
   BinaryMetadataAtomics = 1 << 1,
+  BinaryMetadataUAR = 1 << 2,
 };
 
 /// Parse a -fsanitize= or -fno-sanitize= argument's values, diagnosing any
@@ -1133,7 +1134,8 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
   // flags. Does not depend on any other sanitizers.
   const std::pair<int, std::string> BinaryMetadataFlags[] = {
       std::make_pair(BinaryMetadataCovered, "covered"),
-      std::make_pair(BinaryMetadataAtomics, "atomics")};
+      std::make_pair(BinaryMetadataAtomics, "atomics"),
+      std::make_pair(BinaryMetadataUAR, "uar")};
   for (const auto &F : BinaryMetadataFlags) {
     if (BinaryMetadataFeatures & F.first)
       CmdArgs.push_back(
@@ -1399,6 +1401,7 @@ int parseBinaryMetadataFeatures(const Driver &D, const llvm::opt::Arg *A,
     int F = llvm::StringSwitch<int>(Value)
                 .Case("covered", BinaryMetadataCovered)
                 .Case("atomics", BinaryMetadataAtomics)
+                .Case("uar", BinaryMetadataUAR)
                 .Case("all", ~0)
                 .Default(0);
     if (F == 0 && DiagnoseErrors)

llvm/include/llvm/CodeGen/CodeGenPassBuilder.h

@@ -926,6 +926,7 @@ Error CodeGenPassBuilder<Derived>::addMachinePasses(
 
   addPass(StackMapLivenessPass());
   addPass(LiveDebugValuesPass());
+  addPass(MachineSanitizerBinaryMetadata());
 
   if (TM.Options.EnableMachineOutliner && getOptLevel() != CodeGenOpt::None &&
       Opt.EnableMachineOutliner != RunOutliner::NeverOutline) {

llvm/include/llvm/CodeGen/MachinePassRegistry.def

@@ -202,4 +202,5 @@ DUMMY_MACHINE_FUNCTION_PASS("instruction-select", InstructionSelectPass, ())
 DUMMY_MACHINE_FUNCTION_PASS("reset-machine-function", ResetMachineFunctionPass, ())
 DUMMY_MACHINE_FUNCTION_PASS("machineverifier", MachineVerifierPass, ())
 DUMMY_MACHINE_FUNCTION_PASS("print-machine-cycles", MachineCycleInfoPrinterPass, ())
+DUMMY_MACHINE_FUNCTION_PASS("machine-sanmd", MachineSanitizerBinaryMetadata, ())
 #undef DUMMY_MACHINE_FUNCTION_PASS

llvm/include/llvm/CodeGen/Passes.h

@@ -409,6 +409,10 @@ namespace llvm {
   /// the intrinsic for later emission to the StackMap.
   extern char &StackMapLivenessID;
 
+  // MachineSanitizerBinaryMetadata - appends/finalizes sanitizer binary
+  // metadata after llvm SanitizerBinaryMetadata pass.
+  extern char &MachineSanitizerBinaryMetadataID;
+
   /// RemoveRedundantDebugValues pass.
   extern char &RemoveRedundantDebugValuesID;
 

llvm/include/llvm/InitializePasses.h

@@ -285,6 +285,7 @@ void initializeMachineOutlinerPass(PassRegistry&);
 void initializeMachinePipelinerPass(PassRegistry&);
 void initializeMachinePostDominatorTreePass(PassRegistry&);
 void initializeMachineRegionInfoPassPass(PassRegistry&);
+void initializeMachineSanitizerBinaryMetadataPass(PassRegistry &);
 void initializeMachineSchedulerPass(PassRegistry&);
 void initializeMachineSinkingPass(PassRegistry&);
 void initializeMachineTraceMetricsPass(PassRegistry&);

llvm/include/llvm/Transforms/Instrumentation.h

@@ -150,13 +150,6 @@ struct SanitizerCoverageOptions {
   SanitizerCoverageOptions() = default;
 };
 
-/// Options for SanitizerBinaryMetadata.
-struct SanitizerBinaryMetadataOptions {
-  bool Covered = false;
-  bool Atomics = false;
-  SanitizerBinaryMetadataOptions() = default;
-};
-
 /// Calculate what to divide by to scale counts.
 ///
 /// Given the maximum count, calculate a divisor that will scale all the

llvm/include/llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h

@@ -19,6 +19,27 @@
 
 namespace llvm {
 
+struct SanitizerBinaryMetadataOptions {
+  bool Covered = false;
+  bool Atomics = false;
+  bool UAR = false;
+  SanitizerBinaryMetadataOptions() = default;
+};
+
+inline constexpr int kSanitizerBinaryMetadataAtomicsBit = 0;
+inline constexpr int kSanitizerBinaryMetadataUARBit = 1;
+
+inline constexpr uint32_t kSanitizerBinaryMetadataNone = 0;
+inline constexpr uint32_t kSanitizerBinaryMetadataAtomics =
+    1 << kSanitizerBinaryMetadataAtomicsBit;
+inline constexpr uint32_t kSanitizerBinaryMetadataUAR =
+    1 << kSanitizerBinaryMetadataUARBit;
+
+inline constexpr char kSanitizerBinaryMetadataCoveredSection[] =
+    "sanmd_covered";
+inline constexpr char kSanitizerBinaryMetadataAtomicsSection[] =
+    "sanmd_atomics";
+
 /// Public interface to the SanitizerBinaryMetadata module pass for emitting
 /// metadata for binary analysis sanitizers.
 //

llvm/lib/CodeGen/CMakeLists.txt

@@ -196,6 +196,7 @@ add_llvm_component_library(LLVMCodeGen
   RegisterBankInfo.cpp
   SafeStack.cpp
   SafeStackLayout.cpp
+  SanitizerBinaryMetadata.cpp
   ScheduleDAG.cpp
   ScheduleDAGInstrs.cpp
   ScheduleDAGPrinter.cpp

llvm/lib/CodeGen/CodeGen.cpp

@@ -83,6 +83,7 @@ void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeMachineOptimizationRemarkEmitterPassPass(Registry);
   initializeMachineOutlinerPass(Registry);
   initializeMachinePipelinerPass(Registry);
+  initializeMachineSanitizerBinaryMetadataPass(Registry);
   initializeModuloScheduleTestPass(Registry);
   initializeMachinePostDominatorTreePass(Registry);
   initializeMachineRegionInfoPassPass(Registry);

llvm/lib/CodeGen/SanitizerBinaryMetadata.cpp

@@ -0,0 +1,78 @@
+//===- SanitizerBinaryMetadata.cpp
+//----------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of SanitizerBinaryMetadata.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include <algorithm>
+
+using namespace llvm;
+
+class MachineSanitizerBinaryMetadata : public MachineFunctionPass {
+public:
+  static char ID;
+
+  MachineSanitizerBinaryMetadata();
+  bool runOnMachineFunction(MachineFunction &F) override;
+};
+
+INITIALIZE_PASS(MachineSanitizerBinaryMetadata, "machine-sanmd",
+                "Machine Sanitizer Binary Metadata", false, false)
+
+char MachineSanitizerBinaryMetadata::ID = 0;
+char &llvm::MachineSanitizerBinaryMetadataID =
+    MachineSanitizerBinaryMetadata::ID;
+
+MachineSanitizerBinaryMetadata::MachineSanitizerBinaryMetadata()
+    : MachineFunctionPass(ID) {
+  initializeMachineSanitizerBinaryMetadataPass(
+      *PassRegistry::getPassRegistry());
+}
+
+bool MachineSanitizerBinaryMetadata::runOnMachineFunction(MachineFunction &MF) {
+  MDNode *MD = MF.getFunction().getMetadata(LLVMContext::MD_pcsections);
+  if (!MD)
+    return false;
+  const auto &Section = *cast<MDString>(MD->getOperand(0));
+  if (!Section.getString().equals(kSanitizerBinaryMetadataCoveredSection))
+    return false;
+  auto &AuxMDs = *cast<MDTuple>(MD->getOperand(1));
+  // Assume it currently only has features.
+  assert(AuxMDs.size() == 1);
+  auto *Features = cast<ConstantAsMetadata>(AuxMDs.getOperand(0))->getValue();
+  if (!Features->getUniqueInteger()[kSanitizerBinaryMetadataUARBit])
+    return false;
+  // Calculate size of stack args for the function.
+  int64_t Size = 0;
+  uint64_t Align = 0;
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  for (int i = -1; i >= (int)-MFI.getNumFixedObjects(); --i) {
+    Size = std::max(Size, MFI.getObjectOffset(i) + MFI.getObjectSize(i));
+    Align = std::max(Align, MFI.getObjectAlign(i).value());
+  }
+  Size = (Size + Align - 1) & ~(Align - 1);
+  auto &F = MF.getFunction();
+  IRBuilder<> IRB(F.getContext());
+  MDBuilder MDB(F.getContext());
+  // Keep the features and append size of stack args to the metadata.
+  const auto *NewMD = MDB.createPCSections(
+      {{Section.getString(), {Features, IRB.getInt32(Size)}}});
+  MD->replaceOperandWith(1, NewMD->getOperand(1));
+  return false;
+}

llvm/lib/CodeGen/TargetPassConfig.cpp

@@ -1269,6 +1269,7 @@ void TargetPassConfig::addMachinePasses() {
 
   addPass(&StackMapLivenessID);
   addPass(&LiveDebugValuesID);
+  addPass(&MachineSanitizerBinaryMetadataID);
 
   if (TM->Options.EnableMachineOutliner && getOptLevel() != CodeGenOpt::None &&
       EnableMachineOutliner != RunOutliner::NeverOutline) {

llvm/lib/Transforms/Instrumentation/SanitizerBinaryMetadata.cpp

@@ -67,14 +67,16 @@ public:
 private:
   // Forbid construction elsewhere.
   explicit constexpr MetadataInfo(StringRef FunctionPrefix,
-                                  StringRef SectionSuffix, int Feature)
+                                  StringRef SectionSuffix, uint32_t Feature)
       : FunctionPrefix(FunctionPrefix), SectionSuffix(SectionSuffix),
-        FeatureMask(Feature != -1 ? (1u << Feature) : 0) {}
+        FeatureMask(Feature) {}
 };
 const MetadataInfo MetadataInfo::Covered{"__sanitizer_metadata_covered",
-                                         "sanmd_covered", -1};
+                                         kSanitizerBinaryMetadataCoveredSection,
+                                         kSanitizerBinaryMetadataNone};
 const MetadataInfo MetadataInfo::Atomics{"__sanitizer_metadata_atomics",
-                                         "sanmd_atomics", 0};
+                                         kSanitizerBinaryMetadataAtomicsSection,
+                                         kSanitizerBinaryMetadataAtomics};
 
 // The only instances of MetadataInfo are the constants above, so a set of
 // them may simply store pointers to them. To deterministically generate code,
@@ -89,11 +91,16 @@ cl::opt<bool> ClEmitCovered("sanitizer-metadata-covered",
 cl::opt<bool> ClEmitAtomics("sanitizer-metadata-atomics",
                             cl::desc("Emit PCs for atomic operations."),
                             cl::Hidden, cl::init(false));
+cl::opt<bool> ClEmitUAR("sanitizer-metadata-uar",
+                        cl::desc("Emit PCs for start of functions that are "
+                                 "subject for use-after-return checking"),
+                        cl::Hidden, cl::init(false));
 
 //===--- Statistics -------------------------------------------------------===//
 
 STATISTIC(NumMetadataCovered, "Metadata attached to covered functions");
 STATISTIC(NumMetadataAtomics, "Metadata attached to atomics");
+STATISTIC(NumMetadataUAR, "Metadata attached to UAR functions");
 
 //===----------------------------------------------------------------------===//
 
@@ -102,6 +109,7 @@ SanitizerBinaryMetadataOptions &&
 transformOptionsFromCl(SanitizerBinaryMetadataOptions &&Opts) {
   Opts.Covered |= ClEmitCovered;
   Opts.Atomics |= ClEmitAtomics;
+  Opts.UAR |= ClEmitUAR;
   return std::move(Opts);
 }
 
@@ -142,7 +150,8 @@ private:
   // function with memory operations (atomic or not) requires covered metadata
   // to determine if a memory operation is atomic or not in modules compiled
   // with SanitizerBinaryMetadata.
-  bool runOn(Instruction &I, MetadataInfoSet &MIS, MDBuilder &MDB);
+  bool runOn(Instruction &I, MetadataInfoSet &MIS, MDBuilder &MDB,
+             uint32_t &FeatureMask);
 
   // Get start/end section marker pointer.
   GlobalVariable *getSectionMarker(const Twine &MarkerName, Type *Ty);
@@ -232,36 +241,58 @@ void SanitizerBinaryMetadata::runOn(Function &F, MetadataInfoSet &MIS) {
 
   // The metadata features enabled for this function, stored along covered
   // metadata (if enabled).
-  uint32_t PerInstrFeatureMask = getEnabledPerInstructionFeature();
+  uint32_t FeatureMask = getEnabledPerInstructionFeature();
   // Don't emit unnecessary covered metadata for all functions to save space.
   bool RequiresCovered = false;
-  if (PerInstrFeatureMask) {
+  // We can only understand if we need to set UAR feature after looking
+  // at the instructions. So we need to check instructions even if FeatureMask
+  // is empty.
+  if (FeatureMask || Options.UAR) {
     for (BasicBlock &BB : F)
       for (Instruction &I : BB)
-        RequiresCovered |= runOn(I, MIS, MDB);
+        RequiresCovered |= runOn(I, MIS, MDB, FeatureMask);
   }
 
+  if (F.isVarArg())
+    FeatureMask &= ~kSanitizerBinaryMetadataUAR;
+  if (FeatureMask & kSanitizerBinaryMetadataUAR)
+    NumMetadataUAR++;
+
   // Covered metadata is always emitted if explicitly requested, otherwise only
   // if some other metadata requires it to unambiguously interpret it for
   // modules compiled with SanitizerBinaryMetadata.
-  if (Options.Covered || RequiresCovered) {
+  if (Options.Covered || (FeatureMask && RequiresCovered)) {
     NumMetadataCovered++;
     const auto *MI = &MetadataInfo::Covered;
     MIS.insert(MI);
     const StringRef Section = getSectionName(MI->SectionSuffix);
     // The feature mask will be placed after the size (32 bit) of the function,
     // so in total one covered entry will use `sizeof(void*) + 4 + 4`.
-    Constant *CFM = IRB.getInt32(PerInstrFeatureMask);
+    Constant *CFM = IRB.getInt32(FeatureMask);
     F.setMetadata(LLVMContext::MD_pcsections,
                   MDB.createPCSections({{Section, {CFM}}}));
   }
 }
 
 bool SanitizerBinaryMetadata::runOn(Instruction &I, MetadataInfoSet &MIS,
-                                    MDBuilder &MDB) {
+                                    MDBuilder &MDB, uint32_t &FeatureMask) {
   SmallVector<const MetadataInfo *, 1> InstMetadata;
   bool RequiresCovered = false;
 
+  if (Options.UAR) {
+    for (unsigned i = 0; i < I.getNumOperands(); ++i) {
+      const Value *V = I.getOperand(i);
+      // TODO(dvyukov): check if V is an address of alloca/function arg.
+      // See isSafeAndProfitableToSinkLoad for addr-taken allocas
+      // and DeadArgumentEliminationPass::removeDeadStuffFromFunction
+      // for iteration over function args.
+      if (V) {
+        RequiresCovered = true;
+        FeatureMask |= kSanitizerBinaryMetadataUAR;
+      }
+    }
+  }
+
   if (Options.Atomics && I.mayReadOrWriteMemory()) {
     auto SSID = getAtomicSyncScopeID(&I);
     if (SSID.has_value() && SSID.value() != SyncScope::SingleThread) {

llvm/test/Instrumentation/SanitizerBinaryMetadata/common.h

@@ -0,0 +1,72 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <assert.h>
+
+int main() {
+  printf("main\n");
+}
+
+typedef unsigned long uptr;
+
+#define FN(X) if (pc == reinterpret_cast<uptr>(X)) return #X
+
+const char* symbolize(uptr pc) {
+  FUNCTIONS;
+  return nullptr;
+}
+
+template<typename T>
+T consume(const char*& pos, const char* end) {
+  T v = *reinterpret_cast<const T*>(pos);
+  pos += sizeof(T);
+  assert(pos <= end);
+  return v;
+}
+
+uint32_t meta_version;
+const char* meta_start;
+const char* meta_end;
+
+extern "C" {
+void __sanitizer_metadata_covered_add(uint32_t version, const char* start, const char* end) {
+  printf("metadata add version %u\n", version);
+  for (const char* pos = start; pos < end;) {
+    const uptr base = reinterpret_cast<uptr>(pos);
+    const long offset = (version & (1 << 16)) ?
+        consume<long>(pos, end) : consume<int>(pos, end);
+    const uint32_t size = consume<uint32_t>(pos, end);
+    const uint32_t features = consume<uint32_t>(pos, end);
+    uint32_t stack_args = 0;
+    if (features & (1 << 1))
+      stack_args = consume<uint32_t>(pos, end);
+    if (const char* name = symbolize(base + offset))
+      printf("%s: features=%x stack_args=%u\n", name, features, stack_args);
+  }
+  meta_version = version;
+  meta_start = start;
+  meta_end = end;
+}
+
+void __sanitizer_metadata_covered_del(uint32_t version, const char* start, const char* end) {
+  assert(version == meta_version);
+  assert(start == meta_start);
+  assert(end == meta_end);
+}
+
+const char* atomics_start;
+const char* atomics_end;
+
+void __sanitizer_metadata_atomics_add(uint32_t version, const char* start, const char* end) {
+  assert(version == meta_version);
+  assert(start);
+  assert(end >= end);
+  atomics_start = start;
+  atomics_end = end;
+}
+
+void __sanitizer_metadata_atomics_del(uint32_t version, const char* start, const char* end) {
+  assert(version == meta_version);
+  assert(atomics_start == start);
+  assert(atomics_end == end);
+}
+}

llvm/test/Instrumentation/SanitizerBinaryMetadata/covered.cpp

@@ -0,0 +1,79 @@
+// REQUIRES: native && target-x86_64
+// RUN: clang++ %s -o %t && %t | FileCheck %s
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=covered && %t | FileCheck -check-prefix=CHECK-C %s
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=atomics && %t | FileCheck -check-prefix=CHECK-A %s
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=uar && %t | FileCheck -check-prefix=CHECK-U %s
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=covered,atomics && %t | FileCheck -check-prefix=CHECK-CA %s
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=covered,uar && %t | FileCheck -check-prefix=CHECK-CU %s
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=atomics,uar && %t | FileCheck -check-prefix=CHECK-AU %s
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=covered,atomics,uar && %t | FileCheck -check-prefix=CHECK-CAU %s
+
+// CHECK-NOT: metadata add
+// CHECK: main
+// CHECK-NOT: metadata del
+
+// CHECK-C:      empty: features=0
+// CHECK-A-NOT:  empty:
+// CHECK-U-NOT:  empty:
+// CHECK-CA:     empty: features=1
+// CHECK-CU:     empty: features=0
+// CHECK-AU-NOT: empty:
+// CHECK-CAU:    empty: features=1
+void empty() {
+}
+
+// CHECK-C:  normal: features=0
+// CHECK-A:  normal: features=1
+// CHECK-U:  normal: features=2
+// CHECK-CA: normal: features=1
+// CHECK-CU: normal: features=2
+// CHECK-AU: normal: features=3
+// CHECK-CAU:normal: features=3
+void normal() {
+  volatile int x;
+  x = 0;
+}
+
+// CHECK-C:   with_atomic: features=0
+// CHECK-A:   with_atomic: features=1
+// CHECK-U:   with_atomic: features=2
+// CHECK-CA:  with_atomic: features=1
+// CHECK-CU:  with_atomic: features=2
+// CHECK-AU:  with_atomic: features=3
+// CHECK-CAU: with_atomic: features=3
+int with_atomic(int* p) {
+  return __atomic_load_n(p, __ATOMIC_RELAXED);
+}
+
+// CHECK-C:     ellipsis: features=0
+// CHECK-A:     ellipsis: features=1
+// CHECK-U-NOT: ellipsis:
+// CHECK-CA:    ellipsis: features=1
+// CHECK-CU:    ellipsis: features=0
+// CHECK-AU:    ellipsis: features=1
+// CHECK-CAU:   ellipsis: features=1
+void ellipsis(int* p, ...) {
+  volatile int x;
+  x = 0;
+}
+
+// CHECK-C:     ellipsis_with_atomic: features=0
+// CHECK-A:     ellipsis_with_atomic: features=1
+// CHECK-U-NOT: ellipsis_with_atomic:
+// CHECK-CA:    ellipsis_with_atomic: features=1
+// CHECK-CU:    ellipsis_with_atomic: features=0
+// CHECK-AU:    ellipsis_with_atomic: features=1
+// CHECK-CAU:   ellipsis_with_atomic: features=1
+int ellipsis_with_atomic(int* p, ...) {
+  return __atomic_load_n(p, __ATOMIC_RELAXED);
+}
+
+#define FUNCTIONS \
+  FN(empty); \
+  FN(normal); \
+  FN(with_atomic); \
+  FN(ellipsis); \
+  FN(ellipsis_with_atomic); \
+/**/
+
+#include "common.h"

llvm/test/Instrumentation/SanitizerBinaryMetadata/lit.local.cfg

@@ -0,0 +1 @@
+config.suffixes = ['.ll', '.cpp']

llvm/test/Instrumentation/SanitizerBinaryMetadata/uar.cpp

@@ -0,0 +1,59 @@
+// We run the compiled binary + sizes of stack arguments depend on the arch.
+// REQUIRES: native && target-x86_64
+// RUN: clang++ %s -o %t -fexperimental-sanitize-metadata=covered,uar && %t | tee /dev/stderr | FileCheck %s
+
+// CHECK: metadata add version 1
+
+// CHECK: empty: features=0 stack_args=0
+void empty() {
+}
+
+// CHECK: ellipsis: features=0 stack_args=0
+void ellipsis(const char* fmt, ...) {
+  volatile int x;
+  x = 1;
+}
+
+// CHECK: non_empty_function: features=2 stack_args=0
+void non_empty_function() {
+  // Completely empty functions don't get uar metadata.
+  volatile int x;
+  x = 1;
+}
+
+// CHECK: no_stack_args: features=2 stack_args=0
+void no_stack_args(long a0, long a1, long a2, long a3, long a4, long a5) {
+  volatile int x;
+  x = 1;
+}
+
+// CHECK: stack_args: features=2 stack_args=16
+void stack_args(long a0, long a1, long a2, long a3, long a4, long a5, long a6) {
+  volatile int x;
+  x = 1;
+}
+
+// CHECK: more_stack_args: features=2 stack_args=32
+void more_stack_args(long a0, long a1, long a2, long a3, long a4, long a5, long a6, long a7, long a8) {
+  volatile int x;
+  x = 1;
+}
+
+// CHECK: struct_stack_args: features=2 stack_args=144
+struct large { char x[131]; };
+void struct_stack_args(large a) {
+  volatile int x;
+  x = 1;
+}
+
+#define FUNCTIONS \
+  FN(empty); \
+  FN(ellipsis); \
+  FN(non_empty_function); \
+  FN(no_stack_args); \
+  FN(stack_args); \
+  FN(more_stack_args); \
+  FN(struct_stack_args); \
+/**/
+
+#include "common.h"