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[asan] produce fewer stores when poisoning stack shadow

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llvm-svn: 197904
This commit is contained in:
Kostya Serebryany 2013-12-23 09:24:36 +00:00
parent 3ae1e13884
commit 911683de1d
1 changed files with 19 additions and 20 deletions
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39
lib/Transforms/Instrumentation/AddressSanitizer.cpp
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@ -1351,27 +1351,26 @@ FunctionStackPoisoner::poisonRedZones(const ArrayRef<uint8_t> ShadowBytes,
IRBuilder<> &IRB, Value *ShadowBase,
bool DoPoison) {
size_t n = ShadowBytes.size();
size_t LargeStoreSize = ASan.LongSize / 8;
size_t i;
for (i = 0; i + LargeStoreSize - 1 < n; i += LargeStoreSize) {
uint64_t Val = 0;
for (size_t j = 0; j < LargeStoreSize; j++) {
if (ASan.TD->isLittleEndian())
Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
else
Val = (Val << 8) | ShadowBytes[i + j];
size_t i = 0;
// We need to (un)poison n bytes of stack shadow. Poison as many as we can
// using 64-bit stores (if we are on 64-bit arch), then poison the rest
// with 32-bit stores, then with 16-byte stores, then with 8-byte stores.
for (size_t LargeStoreSizeInBytes = ASan.LongSize / 8;
LargeStoreSizeInBytes != 0; LargeStoreSizeInBytes /= 2) {
for (; i + LargeStoreSizeInBytes - 1 < n; i += LargeStoreSizeInBytes) {
uint64_t Val = 0;
for (size_t j = 0; j < LargeStoreSizeInBytes; j++) {
if (ASan.TD->isLittleEndian())
Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
else
Val = (Val << 8) | ShadowBytes[i + j];
}
if (!Val) continue;
Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
Type *StoreTy = Type::getIntNTy(*C, LargeStoreSizeInBytes * 8);
Value *Poison = ConstantInt::get(StoreTy, DoPoison ? Val : 0);
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, StoreTy->getPointerTo()));
}
if (!Val) continue;
Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
Value *Poison = ConstantInt::get(IntptrTy, DoPoison ? Val : 0);
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, IntptrPtrTy));
}
for (; i < n; i++) {
uint8_t Val = ShadowBytes[i];
if (!Val) continue;
Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
Value *Poison = ConstantInt::get(IRB.getInt8Ty(), DoPoison ? Val : 0);
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, IRB.getInt8PtrTy()));
}
}