[ASan][compiler-rt] Implemented Dormant Mode in ASan

[gbMattN]

Added the ability to skip runtime checks with ASan, while maintaining shadow memory coherency. You can then dynamically re-enable the checks.
There is a discussion on discourse: https://discourse.llvm.org/t/rfc-adding-a-dormant-mode-to-addresssanitizer/80278

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[llvmbot]

@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: None (gbMattN)

Changes

Added the ability to skip runtime checks with ASan, while maintaining shadow memory coherency. You can then dynamically re-enable the checks.
There is a discussion on discourse: https://discourse.llvm.org/t/rfc-adding-a-dormant-mode-to-addresssanitizer/80278

---

Full diff: https://github.com/llvm/llvm-project/pull/99857.diff

5 Files Affected:

• (modified) compiler-rt/include/sanitizer/asan_interface.h (+7)
• (modified) compiler-rt/lib/asan/asan_interface.inc (+1)
• (modified) compiler-rt/lib/asan/asan_interface_internal.h (+6)
• (modified) compiler-rt/lib/asan/asan_rtl.cpp (+3)
• (modified) llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp (+43-5)

diff --git a/compiler-rt/include/sanitizer/asan_interface.h b/compiler-rt/include/sanitizer/asan_interface.h
index 37b6d08f4db19..f6ca4acb03e9d 100644
--- a/compiler-rt/include/sanitizer/asan_interface.h
+++ b/compiler-rt/include/sanitizer/asan_interface.h
@@ -269,6 +269,13 @@ void SANITIZER_CDECL __asan_set_death_callback(void (*callback)(void));
 void SANITIZER_CDECL
 __asan_set_error_report_callback(void (*callback)(const char *));
 
+/// Sets whether ASan should be dormant or not. If 0 is passed, ASan resumes
+/// checking memory accesses for errors. If a non-0 value is passed, these
+/// checks will be skipped.
+///
+/// \param dormancy A boolean to control if ASan is dormant or not.
+void SANITIZER_CDECL __asan_set_dormant(int dormancy);
+
 /// User-provided callback on ASan errors.
 ///
 /// You can provide a function that would be called immediately when ASan
diff --git a/compiler-rt/lib/asan/asan_interface.inc b/compiler-rt/lib/asan/asan_interface.inc
index bfc44b4619623..499014fcc4a49 100644
--- a/compiler-rt/lib/asan/asan_interface.inc
+++ b/compiler-rt/lib/asan/asan_interface.inc
@@ -107,6 +107,7 @@ INTERFACE_FUNCTION(__asan_report_store16_noabort)
 INTERFACE_FUNCTION(__asan_report_store_n_noabort)
 INTERFACE_FUNCTION(__asan_set_death_callback)
 INTERFACE_FUNCTION(__asan_set_error_report_callback)
+INTERFACE_FUNCTION(__asan_set_dormant)
 INTERFACE_FUNCTION(__asan_set_shadow_00)
 INTERFACE_FUNCTION(__asan_set_shadow_01)
 INTERFACE_FUNCTION(__asan_set_shadow_02)
diff --git a/compiler-rt/lib/asan/asan_interface_internal.h b/compiler-rt/lib/asan/asan_interface_internal.h
index a998263780221..9b2752ce7e05b 100644
--- a/compiler-rt/lib/asan/asan_interface_internal.h
+++ b/compiler-rt/lib/asan/asan_interface_internal.h
@@ -184,6 +184,9 @@ extern "C" {
   SANITIZER_INTERFACE_ATTRIBUTE
   void __asan_set_error_report_callback(void (*callback)(const char*));
 
+  SANITIZER_INTERFACE_ATTRIBUTE
+  void __asan_set_dormant(int dormancy);
+
   SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
   void __asan_on_error();
 
@@ -202,6 +205,9 @@ extern "C" {
   SANITIZER_INTERFACE_ATTRIBUTE
   extern uptr *__asan_test_only_reported_buggy_pointer;
 
+  SANITIZER_INTERFACE_ATTRIBUTE
+  extern bool __asan_is_dormant;
+
   SANITIZER_INTERFACE_ATTRIBUTE void __asan_load1(uptr p);
   SANITIZER_INTERFACE_ATTRIBUTE void __asan_load2(uptr p);
   SANITIZER_INTERFACE_ATTRIBUTE void __asan_load4(uptr p);
diff --git a/compiler-rt/lib/asan/asan_rtl.cpp b/compiler-rt/lib/asan/asan_rtl.cpp
index c484e086a5ef7..56da1180cfc28 100644
--- a/compiler-rt/lib/asan/asan_rtl.cpp
+++ b/compiler-rt/lib/asan/asan_rtl.cpp
@@ -36,6 +36,9 @@
 uptr __asan_shadow_memory_dynamic_address;  // Global interface symbol.
 int __asan_option_detect_stack_use_after_return;  // Global interface symbol.
 uptr *__asan_test_only_reported_buggy_pointer;  // Used only for testing asan.
+bool __asan_is_dormant = true;
+
+void __asan_set_dormant(int dormancy) { __asan_is_dormant = dormancy; }
 
 namespace __asan {
 
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index adf77f20cb1c7..774820ae68924 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -178,6 +178,8 @@ const char kAMDGPUAddressPrivateName[] = "llvm.amdgcn.is.private";
 const char kAMDGPUBallotName[] = "llvm.amdgcn.ballot.i64";
 const char kAMDGPUUnreachableName[] = "llvm.amdgcn.unreachable";
 
+const char kAsanDormancyVarName[] = "__asan_is_dormant";
+
 // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
 static const size_t kNumberOfAccessSizes = 5;
 
@@ -452,6 +454,10 @@ static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
 static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug max inst"),
                                cl::Hidden, cl::init(-1));
 
+static cl::opt<bool> CLAsanDormant("asan-dormant",
+                                   cl::desc("Makes asan dormant"), cl::Hidden,
+                                   cl::init(false));
+
 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
 STATISTIC(NumOptimizedAccessesToGlobalVar,
@@ -852,6 +858,7 @@ struct AddressSanitizer {
 
   FunctionCallee AsanMemmove, AsanMemcpy, AsanMemset;
   Value *LocalDynamicShadow = nullptr;
+  Constant *DormantAsanFlag;
   const StackSafetyGlobalInfo *SSGI;
   DenseMap<const AllocaInst *, bool> ProcessedAllocas;
 
@@ -1579,6 +1586,12 @@ bool AddressSanitizer::GlobalIsLinkerInitialized(GlobalVariable *G) {
 void AddressSanitizer::instrumentPointerComparisonOrSubtraction(
     Instruction *I, RuntimeCallInserter &RTCI) {
   IRBuilder<> IRB(I);
+
+  if (CLAsanDormant)
+    IRB.SetInsertPoint(SplitBlockAndInsertIfThen(
+        IRB.CreateNot(IRB.CreateLoad(IRB.getInt1Ty(), DormantAsanFlag)), I,
+        false));
+
   FunctionCallee F = isa<ICmpInst>(I) ? AsanPtrCmpFunction : AsanPtrSubFunction;
   Value *Param[2] = {I->getOperand(0), I->getOperand(1)};
   for (Value *&i : Param) {
@@ -1593,9 +1606,19 @@ static void doInstrumentAddress(AddressSanitizer *Pass, Instruction *I,
                                 MaybeAlign Alignment, unsigned Granularity,
                                 TypeSize TypeStoreSize, bool IsWrite,
                                 Value *SizeArgument, bool UseCalls,
-                                uint32_t Exp, RuntimeCallInserter &RTCI) {
+                                uint32_t Exp, RuntimeCallInserter &RTCI,
+                                Value *DormantAsanFlag) {
   // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
   // if the data is properly aligned.
+
+  Instruction *InsertPoint = InsertBefore;
+  if (CLAsanDormant) {
+    InstrumentationIRBuilder IRB(InsertPoint);
+    InsertPoint = SplitBlockAndInsertIfThen(
+        IRB.CreateNot(IRB.CreateLoad(IRB.getInt1Ty(), DormantAsanFlag)),
+        InsertBefore, false);
+  }
+
   if (!TypeStoreSize.isScalable()) {
     const auto FixedSize = TypeStoreSize.getFixedValue();
     switch (FixedSize) {
@@ -1606,12 +1629,12 @@ static void doInstrumentAddress(AddressSanitizer *Pass, Instruction *I,
     case 128:
       if (!Alignment || *Alignment >= Granularity ||
           *Alignment >= FixedSize / 8)
-        return Pass->instrumentAddress(I, InsertBefore, Addr, Alignment,
+        return Pass->instrumentAddress(I, InsertPoint, Addr, Alignment,
                                        FixedSize, IsWrite, nullptr, UseCalls,
                                        Exp, RTCI);
     }
   }
-  Pass->instrumentUnusualSizeOrAlignment(I, InsertBefore, Addr, TypeStoreSize,
+  Pass->instrumentUnusualSizeOrAlignment(I, InsertPoint, Addr, TypeStoreSize,
                                          IsWrite, nullptr, UseCalls, Exp, RTCI);
 }
 
@@ -1627,6 +1650,14 @@ void AddressSanitizer::instrumentMaskedLoadOrStore(
 
   IRBuilder IB(I);
   Instruction *LoopInsertBefore = I;
+
+  if (CLAsanDormant) {
+    LoopInsertBefore = SplitBlockAndInsertIfThen(
+        IB.CreateNot(IB.CreateLoad(IB.getInt1Ty(), DormantAsanFlag)),
+        LoopInsertBefore, false);
+    IB.SetInsertPoint(LoopInsertBefore);
+  }
+
   if (EVL) {
     // The end argument of SplitBlockAndInsertForLane is assumed bigger
     // than zero, so we should check whether EVL is zero here.
@@ -1677,7 +1708,7 @@ void AddressSanitizer::instrumentMaskedLoadOrStore(
     }
     doInstrumentAddress(Pass, I, &*IRB.GetInsertPoint(), InstrumentedAddress,
                         Alignment, Granularity, ElemTypeSize, IsWrite,
-                        SizeArgument, UseCalls, Exp, RTCI);
+                        SizeArgument, UseCalls, Exp, RTCI, DormantAsanFlag);
   });
 }
 
@@ -1734,7 +1765,7 @@ void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
   } else {
     doInstrumentAddress(this, O.getInsn(), O.getInsn(), Addr, O.Alignment,
                         Granularity, O.TypeStoreSize, O.IsWrite, nullptr,
-                        UseCalls, Exp, RTCI);
+                        UseCalls, Exp, RTCI, DormantAsanFlag);
   }
 }
 
@@ -1846,6 +1877,11 @@ void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
   }
 
   InstrumentationIRBuilder IRB(InsertBefore);
+  if (CLAsanDormant)
+    IRB.SetInsertPoint(SplitBlockAndInsertIfThen(
+        IRB.CreateNot(IRB.CreateLoad(IRB.getInt1Ty(), DormantAsanFlag)),
+        InsertBefore, false));
+
   size_t AccessSizeIndex = TypeStoreSizeToSizeIndex(TypeStoreSize);
   const ASanAccessInfo AccessInfo(IsWrite, CompileKernel, AccessSizeIndex);
 
@@ -2856,6 +2892,8 @@ void AddressSanitizer::initializeCallbacks(Module &M, const TargetLibraryInfo *T
       M.getOrInsertFunction(kAMDGPUAddressSharedName, IRB.getInt1Ty(), PtrTy);
   AMDGPUAddressPrivate =
       M.getOrInsertFunction(kAMDGPUAddressPrivateName, IRB.getInt1Ty(), PtrTy);
+
+  DormantAsanFlag = M.getOrInsertGlobal(kAsanDormancyVarName, IRB.getInt1Ty());
 }
 
 bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {

[gbMattN]

@kcc ((manually add reviewers))

[vitalybuka]

Technically you didn't request review, but it's not on my dashboard.
To hide it, I'll pretend requesting changing.

Please "re-request" review when needed.

[gbMattN]

@vitalybuka ready for review! I've put performance stats on the discourse page. There was an lldb test failing (functionalities/single-thread-step/TestSingleThreadStepTimeout.py timed out) but I didn't touch any lldb code. I've sent a blank commit to rerun the tests in case it was being flakey.

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff 8107810cad24d41fe43c6777370c7b81ca83ad84 86205e3e453dd4d54b3bd7852e12aa9189d9c888 --extensions inc,h,cpp -- compiler-rt/test/asan/TestCases/dormant.cpp compiler-rt/include/sanitizer/asan_interface.h compiler-rt/lib/asan/asan_interface.inc compiler-rt/lib/asan/asan_interface_internal.h compiler-rt/lib/asan/asan_rtl.cpp llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

View the diff from clang-format here.

diff --git a/compiler-rt/test/asan/TestCases/dormant.cpp b/compiler-rt/test/asan/TestCases/dormant.cpp
index 5efa2f9836..04c0c140b2 100644
--- a/compiler-rt/test/asan/TestCases/dormant.cpp
+++ b/compiler-rt/test/asan/TestCases/dormant.cpp
@@ -3,14 +3,14 @@
 // REQUIRES: stable-runtime
 
 #include <sanitizer/asan_interface.h>
-int readHeapAfterFree(){
-  int * volatile x = new int[10];
+int readHeapAfterFree() {
+  int *volatile x = new int[10];
   delete[] x;
   return x[5];
 }
 
-static int * volatile y;
-int writeHeapAfterFree(){
+static int *volatile y;
+int writeHeapAfterFree() {
   y = new int[10];
   delete[] y;
   return y[5] = 413;
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 3665930f9c..a34ec2e82d 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -1742,9 +1742,9 @@ void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
     NumInstrumentedWrites++;
   else
     NumInstrumentedReads++;
-  
-  Instruction* InsertPoint = O.getInsn();
-  if(CLAsanDormant){
+
+  Instruction *InsertPoint = O.getInsn();
+  if (CLAsanDormant) {
     InstrumentationIRBuilder IRB(InsertPoint);
     InsertPoint = SplitBlockAndInsertIfThen(
         IRB.CreateNot(IRB.CreateLoad(IRB.getInt1Ty(), DormantAsanFlag)),

[vitalybuka]

We don't have consensus on https://discourse.llvm.org/t/rfc-adding-a-dormant-mode-to-addresssanitizer/80278 about usefulness of the feature.