hwasan: Read shadow address from ifunc if we don't need a frame record.
This saves a cbz+cold call in the interceptor ABI, as well as a realign
in both ABIs, trading off a dcache entry against some branch predictor
entries and some code size.
Unfortunately the functionality is hidden behind a flag because ifunc is
known to be broken on static binaries on Android.
Differential Revision: https://reviews.llvm.org/D57084
llvm-svn: 351989
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index a00070e..6170b79 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -160,6 +160,10 @@
cl::desc("inline all checks"),
cl::Hidden, cl::init(false));
+static cl::opt<bool> ClAllowIfunc("hwasan-allow-ifunc",
+ cl::desc("allow the use of ifunc"),
+ cl::Hidden, cl::init(false));
+
namespace {
/// An instrumentation pass implementing detection of addressability bugs
@@ -183,6 +187,7 @@
void initializeCallbacks(Module &M);
+ Value *getDynamicShadowIfunc(IRBuilder<> &IRB);
Value *getDynamicShadowNonTls(IRBuilder<> &IRB);
void untagPointerOperand(Instruction *I, Value *Addr);
@@ -384,9 +389,8 @@
HwasanGenerateTagFunc = checkSanitizerInterfaceFunction(
M.getOrInsertFunction("__hwasan_generate_tag", Int8Ty));
- if (Mapping.InGlobal)
- ShadowGlobal = M.getOrInsertGlobal("__hwasan_shadow",
- ArrayType::get(IRB.getInt8Ty(), 0));
+ ShadowGlobal = M.getOrInsertGlobal("__hwasan_shadow",
+ ArrayType::get(IRB.getInt8Ty(), 0));
const std::string MemIntrinCallbackPrefix =
CompileKernel ? std::string("") : ClMemoryAccessCallbackPrefix;
@@ -404,19 +408,23 @@
M.getOrInsertFunction("__hwasan_thread_enter", IRB.getVoidTy()));
}
+Value *HWAddressSanitizer::getDynamicShadowIfunc(IRBuilder<> &IRB) {
+ // An empty inline asm with input reg == output reg.
+ // An opaque no-op cast, basically.
+ InlineAsm *Asm = InlineAsm::get(
+ FunctionType::get(Int8PtrTy, {ShadowGlobal->getType()}, false),
+ StringRef(""), StringRef("=r,0"),
+ /*hasSideEffects=*/false);
+ return IRB.CreateCall(Asm, {ShadowGlobal}, ".hwasan.shadow");
+}
+
Value *HWAddressSanitizer::getDynamicShadowNonTls(IRBuilder<> &IRB) {
// Generate code only when dynamic addressing is needed.
if (Mapping.Offset != kDynamicShadowSentinel)
return nullptr;
if (Mapping.InGlobal) {
- // An empty inline asm with input reg == output reg.
- // An opaque no-op cast, basically.
- InlineAsm *Asm = InlineAsm::get(
- FunctionType::get(Int8PtrTy, {ShadowGlobal->getType()}, false),
- StringRef(""), StringRef("=r,0"),
- /*hasSideEffects=*/false);
- return IRB.CreateCall(Asm, {ShadowGlobal}, ".hwasan.shadow");
+ return getDynamicShadowIfunc(IRB);
} else {
Value *GlobalDynamicAddress =
IRB.GetInsertBlock()->getParent()->getParent()->getOrInsertGlobal(
@@ -828,6 +836,9 @@
if (!Mapping.InTls)
return getDynamicShadowNonTls(IRB);
+ if (ClAllowIfunc && !WithFrameRecord && TargetTriple.isAndroid())
+ return getDynamicShadowIfunc(IRB);
+
Value *SlotPtr = getHwasanThreadSlotPtr(IRB, IntptrTy);
assert(SlotPtr);