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[mte] support more complicated lifetimes (e.g. for exceptions). 

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D118848
This commit is contained in:
Florian Mayer 2022-02-02 13:53:34 -08:00
parent 7756b34ef2
commit f7a6c341cb
5 changed files with 59 additions and 10 deletions
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2
llvm/include/llvm/Transforms/Utils/MemoryTaggingSupport.h
View File

@ -67,7 +67,7 @@ bool forAllReachableExits(const DominatorTree &DT, const PostDominatorTree &PDT,
bool isStandardLifetime(const SmallVectorImpl<IntrinsicInst *> &LifetimeStart,
const SmallVectorImpl<IntrinsicInst *> &LifetimeEnd,
const DominatorTree &DT, size_t MaxLifetimes);
const DominatorTree *DT, size_t MaxLifetimes);
} // namespace llvm
#endif

21
llvm/lib/Target/AArch64/AArch64StackTagging.cpp
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@ -78,6 +78,12 @@ static cl::opt<unsigned>
ClMergeInitSizeLimit("stack-tagging-merge-init-size-limit", cl::init(272),
cl::Hidden);
static cl::opt<size_t> ClMaxLifetimes(
"stack-tagging-max-lifetimes-for-alloca", cl::Hidden, cl::init(3),
cl::ReallyHidden,
cl::desc("How many lifetime ends to handle for a single alloca."),
cl::Optional);
static const Align kTagGranuleSize = Align(16);
namespace {
@ -645,14 +651,17 @@ bool AArch64StackTagging::runOnFunction(Function &Fn) {
Info.AI->replaceAllUsesWith(TagPCall);
TagPCall->setOperand(0, Info.AI);
bool StandardLifetime =
UnrecognizedLifetimes.empty() &&
isStandardLifetime(Info.LifetimeStart, Info.LifetimeEnd, DT,
ClMaxLifetimes);
// Calls to functions that may return twice (e.g. setjmp) confuse the
// postdominator analysis, and will leave us to keep memory tagged after
// function return. Work around this by always untagging at every return
// statement if return_twice functions are called.
if (UnrecognizedLifetimes.empty() && Info.LifetimeStart.size() == 1 &&
Info.LifetimeEnd.size() == 1 && !CallsReturnTwice) {
if (UnrecognizedLifetimes.empty() && StandardLifetime &&
!CallsReturnTwice) {
IntrinsicInst *Start = Info.LifetimeStart[0];
IntrinsicInst *End = Info.LifetimeEnd[0];
uint64_t Size =
cast<ConstantInt>(Start->getArgOperand(0))->getZExtValue();
Size = alignTo(Size, kTagGranuleSize);
@ -661,8 +670,10 @@ bool AArch64StackTagging::runOnFunction(Function &Fn) {
auto TagEnd = [&](Instruction *Node) { untagAlloca(AI, Node, Size); };
if (!DT || !PDT ||
!forAllReachableExits(*DT, *PDT, Start, Info.LifetimeEnd, RetVec,
TagEnd))
End->eraseFromParent();
TagEnd)) {
for (auto *End : Info.LifetimeEnd)
End->eraseFromParent();
}
} else {
uint64_t Size = Info.AI->getAllocationSizeInBits(*DL).getValue() / 8;
Value *Ptr = IRB.CreatePointerCast(TagPCall, IRB.getInt8PtrTy());

2
llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
View File

@ -1382,7 +1382,7 @@ bool HWAddressSanitizer::instrumentStack(
};
bool StandardLifetime =
UnrecognizedLifetimes.empty() &&
isStandardLifetime(Info.LifetimeStart, Info.LifetimeEnd, GetDT(),
isStandardLifetime(Info.LifetimeStart, Info.LifetimeEnd, &GetDT(),
ClMaxLifetimes);
if (ShouldDetectUseAfterScope && StandardLifetime) {
IntrinsicInst *Start = Info.LifetimeStart[0];

6
llvm/lib/Transforms/Utils/MemoryTaggingSupport.cpp
View File

@ -15,7 +15,7 @@
namespace llvm {
namespace {
bool maybeReachableFromEachOther(const SmallVectorImpl<IntrinsicInst *> &Insts,
const DominatorTree &DT, size_t MaxLifetimes) {
const DominatorTree *DT, size_t MaxLifetimes) {
// If we have too many lifetime ends, give up, as the algorithm below is N^2.
if (Insts.size() > MaxLifetimes)
return true;
@ -23,7 +23,7 @@ bool maybeReachableFromEachOther(const SmallVectorImpl<IntrinsicInst *> &Insts,
for (size_t J = 0; J < Insts.size(); ++J) {
if (I == J)
continue;
if (isPotentiallyReachable(Insts[I], Insts[J], nullptr, &DT))
if (isPotentiallyReachable(Insts[I], Insts[J], nullptr, DT))
return true;
}
}
@ -33,7 +33,7 @@ bool maybeReachableFromEachOther(const SmallVectorImpl<IntrinsicInst *> &Insts,
bool isStandardLifetime(const SmallVectorImpl<IntrinsicInst *> &LifetimeStart,
const SmallVectorImpl<IntrinsicInst *> &LifetimeEnd,
const DominatorTree &DT, size_t MaxLifetimes) {
const DominatorTree *DT, size_t MaxLifetimes) {
// An alloca that has exactly one start and end in every possible execution.
// If it has multiple ends, they have to be unreachable from each other, so
// at most one of them is actually used for each execution of the function.

38
llvm/test/CodeGen/AArch64/stack-tagging-split-lifetime.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: opt -S -aarch64-stack-tagging -stack-tagging-use-stack-safety=0 %s -o - | FileCheck %s
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-arm-unknown-eabi"
define void @f(i1 %cond) local_unnamed_addr sanitize_memtag {
start:
; CHECK-LABEL: start:
%a = alloca i8, i32 48, align 8
call void @llvm.lifetime.start.p0i8(i64 48, i8* nonnull %a)
; CHECK: call void @llvm.aarch64.settag(i8* %a.tag, i64 48)
br i1 %cond, label %next0, label %next1
next0:
; CHECK-LABEL: next0:
; CHECK: call void @llvm.aarch64.settag
call void @llvm.lifetime.end.p0i8(i64 40, i8* nonnull %a)
br label %exit0
exit0:
; CHECK-LABEL: exit0:
; CHECK-NOT: call void @llvm.aarch64.settag
ret void
next1:
; CHECK-LABEL: next1:
; CHECK: call void @llvm.aarch64.settag
call void @llvm.lifetime.end.p0i8(i64 40, i8* nonnull %a)
br label %exit1
exit1:
; CHECK-LABEL: exit1:
; CHECK-NOT: call void @llvm.aarch64.settag
ret void
}
declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)