hwasan: Compatibility fixes for short granules.

We can't use short granules with stack instrumentation when targeting older
API levels because the rest of the system won't understand the short granule
tags stored in shadow memory.

Moreover, we need to be able to let old binaries (which won't understand
short granule tags) run on a new system that supports short granule
tags. Such binaries will call the __hwasan_tag_mismatch function when their
outlined checks fail. We can compensate for the binary's lack of support
for short granules by implementing the short granule part of the check in
the __hwasan_tag_mismatch function. Unfortunately we can't do anything about
inline checks, but I don't believe that we can generate these by default on
aarch64, nor did we do so when the ABI was fixed.

A new function, __hwasan_tag_mismatch_v2, is introduced that lets code
targeting the new runtime avoid redoing the short granule check. Because tag
mismatches are rare this isn't important from a performance perspective; the
main benefit is that it introduces a symbol dependency that prevents binaries
targeting the new runtime from running on older (i.e. incompatible) runtimes.

Differential Revision: https://reviews.llvm.org/D68059

llvm-svn: 373035

1 files changed, 18 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index df7606dfa24..2bc127bc982 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -166,6 +166,11 @@ static cl::opt<bool>
                             cl::desc("instrument landing pads"), cl::Hidden,
                             cl::init(false), cl::ZeroOrMore);
 
+static cl::opt<bool> ClUseShortGranules(
+    "hwasan-use-short-granules",
+    cl::desc("use short granules in allocas and outlined checks"), cl::Hidden,
+    cl::init(false), cl::ZeroOrMore);
+
 static cl::opt<bool> ClInstrumentPersonalityFunctions(
     "hwasan-instrument-personality-functions",
     cl::desc("instrument personality functions"), cl::Hidden, cl::init(false),
@@ -269,6 +274,7 @@ private:
 
   bool CompileKernel;
   bool Recover;
+  bool UseShortGranules;
   bool InstrumentLandingPads;
 
   Function *HwasanCtorFunction;
@@ -372,11 +378,14 @@ void HWAddressSanitizer::initializeModule() {
   HwasanCtorFunction = nullptr;
 
   // Older versions of Android do not have the required runtime support for
-  // global or personality function instrumentation. On other platforms we
-  // currently require using the latest version of the runtime.
+  // short granules, global or personality function instrumentation. On other
+  // platforms we currently require using the latest version of the runtime.
   bool NewRuntime =
       !TargetTriple.isAndroid() || !TargetTriple.isAndroidVersionLT(30);
 
+  UseShortGranules =
+      ClUseShortGranules.getNumOccurrences() ? ClUseShortGranules : NewRuntime;
+
   // If we don't have personality function support, fall back to landing pads.
   InstrumentLandingPads = ClInstrumentLandingPads.getNumOccurrences()
                               ? ClInstrumentLandingPads
@@ -608,9 +617,11 @@ void HWAddressSanitizer::instrumentMemAccessInline(Value *Ptr, bool IsWrite,
       TargetTriple.isOSBinFormatELF() && !Recover) {
     Module *M = IRB.GetInsertBlock()->getParent()->getParent();
     Ptr = IRB.CreateBitCast(Ptr, Int8PtrTy);
-    IRB.CreateCall(
-        Intrinsic::getDeclaration(M, Intrinsic::hwasan_check_memaccess),
-        {shadowBase(), Ptr, ConstantInt::get(Int32Ty, AccessInfo)});
+    IRB.CreateCall(Intrinsic::getDeclaration(
+                       M, UseShortGranules
+                              ? Intrinsic::hwasan_check_memaccess_shortgranules
+                              : Intrinsic::hwasan_check_memaccess),
+                   {shadowBase(), Ptr, ConstantInt::get(Int32Ty, AccessInfo)});
     return;
   }
 
@@ -763,6 +774,8 @@ static uint64_t getAllocaSizeInBytes(const AllocaInst &AI) {
 bool HWAddressSanitizer::tagAlloca(IRBuilder<> &IRB, AllocaInst *AI,
                                    Value *Tag, size_t Size) {
   size_t AlignedSize = alignTo(Size, Mapping.getObjectAlignment());
+  if (!UseShortGranules)
+    Size = AlignedSize;
 
   Value *JustTag = IRB.CreateTrunc(Tag, IRB.getInt8Ty());
   if (ClInstrumentWithCalls) {