[MSAN] Instrument libatomic load/store calls

These calls are neither intercepted by compiler-rt nor is libatomic.a
naturally instrumented.

This patch uses the existing libcall mechanism to detect a call
to atomic_load or atomic_store, and instruments them much like
the preexisting instrumentation for atomics.

Calls to _load are modified to have at least Acquire ordering, and
calls to _store at least Release ordering. Because this needs to be
converted at runtime, msan injects a LUT (implemented as a vector
with extractelement).

Differential Revision: https://reviews.llvm.org/D83337

compiler-rt/test/msan/libatomic.c

@@ -0,0 +1,37 @@
+// RUN: %clangxx_msan -fsanitize-memory-track-origins=2 -latomic -DTEST_STORE -O0 %s -o %t && %run %t 2>&1
+// RUN: %clangxx_msan -fsanitize-memory-track-origins=0 -latomic -DTEST_LOAD -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK
+// RUN: %clangxx_msan -fsanitize-memory-track-origins=2 -latomic -DTEST_LOAD -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-SHADOW
+
+#include <sanitizer/msan_interface.h>
+#include <stdatomic.h>
+
+typedef struct __attribute((packed)) {
+  uint8_t val[3];
+} i24;
+
+void copy(i24 *dst, i24 *src);
+
+int main() {
+  i24 uninit;
+  i24 init = {0};
+
+  __msan_check_mem_is_initialized(&init, 3);
+  copy(&init, &uninit);
+  __msan_check_mem_is_initialized(&init, 3);
+}
+
+void copy(i24 *dst, i24 *src) {
+#ifdef TEST_LOAD
+  __atomic_load(src, dst, __ATOMIC_RELAXED);
+
+  // CHECK: MemorySanitizer: use-of-uninitialized-value
+  // CHECK: #0 {{0x[a-f0-9]+}} in main{{.*}}libatomic.c:[[@LINE-8]]
+
+  // CHECK-SHADOW: Uninitialized value was stored to memory at
+  // CHECK-SHADOW: #0 {{0x[a-f0-9]+}} in copy{{.*}}libatomic.c:[[@LINE-6]]
+#endif
+#ifdef TEST_STORE
+  // Store always writes a clean shadow
+  __atomic_store(src, dst, __ATOMIC_RELAXED);
+#endif
+}

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

@@ -572,6 +572,9 @@ class MemorySanitizer {
   /// uninitialized value and returns an updated origin id encoding this info.
   FunctionCallee MsanChainOriginFn;
 
+  /// Run-time helper that paints an origin over a region.
+  FunctionCallee MsanSetOriginFn;
+
   /// MSan runtime replacements for memmove, memcpy and memset.
   FunctionCallee MemmoveFn, MemcpyFn, MemsetFn;
 
@@ -850,6 +853,9 @@ void MemorySanitizer::initializeCallbacks(Module &M) {
   // instrumentation.
   MsanChainOriginFn = M.getOrInsertFunction(
     "__msan_chain_origin", IRB.getInt32Ty(), IRB.getInt32Ty());
+  MsanSetOriginFn =
+      M.getOrInsertFunction("__msan_set_origin", IRB.getVoidTy(),
+                            IRB.getInt8PtrTy(), IntptrTy, IRB.getInt32Ty());
   MemmoveFn = M.getOrInsertFunction(
     "__msan_memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
     IRB.getInt8PtrTy(), IntptrTy);
@@ -1769,6 +1775,24 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     llvm_unreachable("Unknown ordering");
   }
 
+  Value *makeAddReleaseOrderingTable(IRBuilder<> &IRB) {
+    constexpr int NumOrderings = (int)AtomicOrderingCABI::seq_cst + 1;
+    uint32_t OrderingTable[NumOrderings] = {};
+
+    OrderingTable[(int)AtomicOrderingCABI::relaxed] =
+        OrderingTable[(int)AtomicOrderingCABI::release] =
+            (int)AtomicOrderingCABI::release;
+    OrderingTable[(int)AtomicOrderingCABI::consume] =
+        OrderingTable[(int)AtomicOrderingCABI::acquire] =
+            OrderingTable[(int)AtomicOrderingCABI::acq_rel] =
+                (int)AtomicOrderingCABI::acq_rel;
+    OrderingTable[(int)AtomicOrderingCABI::seq_cst] =
+        (int)AtomicOrderingCABI::seq_cst;
+
+    return ConstantDataVector::get(IRB.getContext(),
+                                   makeArrayRef(OrderingTable, NumOrderings));
+  }
+
   AtomicOrdering addAcquireOrdering(AtomicOrdering a) {
     switch (a) {
       case AtomicOrdering::NotAtomic:
@@ -1786,6 +1810,24 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     llvm_unreachable("Unknown ordering");
   }
 
+  Value *makeAddAcquireOrderingTable(IRBuilder<> &IRB) {
+    constexpr int NumOrderings = (int)AtomicOrderingCABI::seq_cst + 1;
+    uint32_t OrderingTable[NumOrderings] = {};
+
+    OrderingTable[(int)AtomicOrderingCABI::relaxed] =
+        OrderingTable[(int)AtomicOrderingCABI::acquire] =
+            OrderingTable[(int)AtomicOrderingCABI::consume] =
+                (int)AtomicOrderingCABI::acquire;
+    OrderingTable[(int)AtomicOrderingCABI::release] =
+        OrderingTable[(int)AtomicOrderingCABI::acq_rel] =
+            (int)AtomicOrderingCABI::acq_rel;
+    OrderingTable[(int)AtomicOrderingCABI::seq_cst] =
+        (int)AtomicOrderingCABI::seq_cst;
+
+    return ConstantDataVector::get(IRB.getContext(),
+                                   makeArrayRef(OrderingTable, NumOrderings));
+  }
+
   // ------------------- Visitors.
   using InstVisitor<MemorySanitizerVisitor>::visit;
   void visit(Instruction &I) {
@@ -3404,6 +3446,60 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     }
   }
 
+  void visitLibAtomicLoad(CallBase &CB) {
+    IRBuilder<> IRB(&CB);
+    Value *Size = CB.getArgOperand(0);
+    Value *SrcPtr = CB.getArgOperand(1);
+    Value *DstPtr = CB.getArgOperand(2);
+    Value *Ordering = CB.getArgOperand(3);
+    // Convert the call to have at least Acquire ordering to make sure
+    // the shadow operations aren't reordered before it.
+    Value *NewOrdering =
+        IRB.CreateExtractElement(makeAddAcquireOrderingTable(IRB), Ordering);
+    CB.setArgOperand(3, NewOrdering);
+
+    IRBuilder<> NextIRB(CB.getNextNode());
+    NextIRB.SetCurrentDebugLocation(CB.getDebugLoc());
+
+    Value *SrcShadowPtr, *SrcOriginPtr;
+    std::tie(SrcShadowPtr, SrcOriginPtr) =
+        getShadowOriginPtr(SrcPtr, NextIRB, NextIRB.getInt8Ty(), Align(1),
+                           /*isStore*/ false);
+    Value *DstShadowPtr =
+        getShadowOriginPtr(DstPtr, NextIRB, NextIRB.getInt8Ty(), Align(1),
+                           /*isStore*/ true)
+            .first;
+
+    NextIRB.CreateMemCpy(DstShadowPtr, Align(1), SrcShadowPtr, Align(1), Size);
+    if (MS.TrackOrigins) {
+      Value *SrcOrigin = NextIRB.CreateAlignedLoad(MS.OriginTy, SrcOriginPtr,
+                                                   kMinOriginAlignment);
+      Value *NewOrigin = updateOrigin(SrcOrigin, NextIRB);
+      NextIRB.CreateCall(MS.MsanSetOriginFn, {DstPtr, Size, NewOrigin});
+    }
+  }
+
+  void visitLibAtomicStore(CallBase &CB) {
+    IRBuilder<> IRB(&CB);
+    Value *Size = CB.getArgOperand(0);
+    Value *DstPtr = CB.getArgOperand(2);
+    Value *Ordering = CB.getArgOperand(3);
+    // Convert the call to have at least Release ordering to make sure
+    // the shadow operations aren't reordered after it.
+    Value *NewOrdering =
+        IRB.CreateExtractElement(makeAddReleaseOrderingTable(IRB), Ordering);
+    CB.setArgOperand(3, NewOrdering);
+
+    Value *DstShadowPtr =
+        getShadowOriginPtr(DstPtr, IRB, IRB.getInt8Ty(), Align(1),
+                           /*isStore*/ true)
+            .first;
+
+    // Atomic store always paints clean shadow/origin. See file header.
+    IRB.CreateMemSet(DstShadowPtr, getCleanShadow(IRB.getInt8Ty()), Size,
+                     Align(1));
+  }
+
   void visitCallBase(CallBase &CB) {
     assert(!CB.getMetadata("nosanitize"));
     if (CB.isInlineAsm()) {
@@ -3417,6 +3513,23 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
         visitInstruction(CB);
       return;
     }
+    LibFunc LF;
+    if (TLI->getLibFunc(CB, LF)) {
+      // libatomic.a functions need to have special handling because there isn't
+      // a good way to intercept them or compile the library with
+      // instrumentation.
+      switch (LF) {
+      case LibFunc_atomic_load:
+        visitLibAtomicLoad(CB);
+        return;
+      case LibFunc_atomic_store:
+        visitLibAtomicStore(CB);
+        return;
+      default:
+        break;
+      }
+    }
+
     if (auto *Call = dyn_cast<CallInst>(&CB)) {
       assert(!isa<IntrinsicInst>(Call) && "intrinsics are handled elsewhere");
 

llvm/test/Instrumentation/MemorySanitizer/libatomic.ll

@@ -0,0 +1,69 @@
+; RUN: opt < %s -msan-check-access-address=0 -S -passes=msan 2>&1 | FileCheck %s
+; RUN: opt < %s -msan-check-access-address=0 -msan-track-origins=2 -S -passes=msan 2>&1 | FileCheck %s -check-prefixes=CHECK,CHECK-ORIGIN
+; RUN: opt < %s -msan -msan-check-access-address=0 -S | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @__atomic_load(i64, i8*, i8*, i32)
+declare void @__atomic_store(i64, i8*, i8*, i32)
+
+define i24 @odd_sized_load(i24* %ptr) sanitize_memory {
+; CHECK: @odd_sized_load(i24* {{.*}}[[PTR:%.+]])
+; CHECK: [[VAL_PTR:%.*]] = alloca i24, align 1
+; CHECK-ORIGIN: @__msan_set_alloca_origin
+; CHECK: [[VAL_PTR_I8:%.*]] = bitcast i24* [[VAL_PTR]] to i8*
+; CHECK: [[PTR_I8:%.*]] = bitcast i24* [[PTR]] to i8*
+; CHECK: call void @__atomic_load(i64 3, i8* [[PTR_I8]], i8* [[VAL_PTR_I8]], i32 2)
+
+; CHECK: ptrtoint i8* [[PTR_I8]]
+; CHECK: xor
+; CHECK: [[SPTR_I8:%.*]] = inttoptr
+; CHECK-ORIGIN: add
+; CHECK-ORIGIN: and
+; CHECK-ORIGIN: [[OPTR:%.*]] = inttoptr
+
+; CHECK: ptrtoint i8* [[VAL_PTR_I8]]
+; CHECK: xor
+; CHECK: [[VAL_SPTR_I8:%.*]] = inttoptr
+; CHECK-ORIGIN: add
+; CHECK-ORIGIN: and
+; CHECK-ORIGIN: [[VAL_OPTR:%.*]] = inttoptr
+
+; CHECK: call void @llvm.memcpy{{.*}}(i8* align 1 [[VAL_SPTR_I8]], i8* align 1 [[SPTR_I8]], i64 3
+
+; CHECK-ORIGIN: [[ARG_ORIGIN:%.*]] = load i32, i32* [[OPTR]]
+; CHECK-ORIGIN: [[VAL_ORIGIN:%.*]] = call i32 @__msan_chain_origin(i32 [[ARG_ORIGIN]])
+; CHECK-ORIGIN: call void @__msan_set_origin(i8* [[VAL_PTR_I8]], i64 3, i32 [[VAL_ORIGIN]])
+
+; CHECK: [[VAL:%.*]] = load i24, i24* [[VAL_PTR]]
+; CHECK: ret i24 [[VAL]]
+  %val_ptr = alloca i24, align 1
+  %val_ptr_i8 = bitcast i24* %val_ptr to i8*
+  %ptr_i8 = bitcast i24* %ptr to i8*
+  call void @__atomic_load(i64 3, i8* %ptr_i8, i8* %val_ptr_i8, i32 0)
+  %val = load i24, i24* %val_ptr
+  ret i24 %val
+}
+
+define void @odd_sized_store(i24* %ptr, i24 %val) sanitize_memory {
+; CHECK: @odd_sized_store(i24* {{.*}}[[PTR:%.+]], i24 {{.*}}[[VAL:%.+]])
+; CHECK: [[VAL_PTR:%.*]] = alloca i24, align 1
+; CHECK: store i24 [[VAL]], i24* [[VAL_PTR]]
+; CHECK: [[VAL_PTR_I8:%.*]] = bitcast i24* [[VAL_PTR]] to i8*
+; CHECK: [[PTR_I8:%.*]] = bitcast i24* [[PTR]] to i8*
+
+; CHECK: ptrtoint i8* [[PTR_I8]]
+; CHECK: xor
+; CHECK: [[SPTR_I8:%.*]] = inttoptr
+; CHECK: call void @llvm.memset{{.*}}(i8* align 1 [[SPTR_I8]], i8 0, i64 3
+
+; CHECK: call void @__atomic_store(i64 3, i8* [[VAL_PTR_I8]], i8* [[PTR_I8]], i32 3)
+; CHECK: ret void
+  %val_ptr = alloca i24, align 1
+  store i24 %val, i24* %val_ptr
+  %val_ptr_i8 = bitcast i24* %val_ptr to i8*
+  %ptr_i8 = bitcast i24* %ptr to i8*
+  call void @__atomic_store(i64 3, i8* %val_ptr_i8, i8* %ptr_i8, i32 0)
+  ret void
+}
+