[llvm] r209508 - [asan] properly instrument memory accesses that have small alignment (smaller than min(8, size)) by making two checks instead of one. This may slowdown some cases, e.g. long long on 32-bit or wide loads produced after loop unrolling. The benefit is higher sencitivity.
Kostya Serebryany
kcc at google.com
Fri May 23 04:52:07 PDT 2014
Author: kcc
Date: Fri May 23 06:52:07 2014
New Revision: 209508
URL: http://llvm.org/viewvc/llvm-project?rev=209508&view=rev
Log:
[asan] properly instrument memory accesses that have small alignment (smaller than min(8,size)) by making two checks instead of one. This may slowdown some cases, e.g. long long on 32-bit or wide loads produced after loop unrolling. The benefit is higher sencitivity.
Modified:
llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
llvm/trunk/test/Instrumentation/AddressSanitizer/basic.ll
llvm/trunk/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll
llvm/trunk/test/Instrumentation/AddressSanitizer/test64.ll
Modified: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp?rev=209508&r1=209507&r2=209508&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp Fri May 23 06:52:07 2014
@@ -623,26 +623,31 @@ void AddressSanitizer::instrumentMemIntr
}
// If I is an interesting memory access, return the PointerOperand
-// and set IsWrite. Otherwise return NULL.
-static Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite) {
+// and set IsWrite/Alignment. Otherwise return NULL.
+static Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
+ unsigned *Alignment) {
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!ClInstrumentReads) return nullptr;
*IsWrite = false;
+ *Alignment = LI->getAlignment();
return LI->getPointerOperand();
}
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (!ClInstrumentWrites) return nullptr;
*IsWrite = true;
+ *Alignment = SI->getAlignment();
return SI->getPointerOperand();
}
if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
+ *Alignment = 0;
return RMW->getPointerOperand();
}
if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
+ *Alignment = 0;
return XCHG->getPointerOperand();
}
return nullptr;
@@ -692,7 +697,8 @@ AddressSanitizer::instrumentPointerCompa
void AddressSanitizer::instrumentMop(Instruction *I, bool UseCalls) {
bool IsWrite = false;
- Value *Addr = isInterestingMemoryAccess(I, &IsWrite);
+ unsigned Alignment = 0;
+ Value *Addr = isInterestingMemoryAccess(I, &IsWrite, &Alignment);
assert(Addr);
if (ClOpt && ClOptGlobals) {
if (GlobalVariable *G = dyn_cast<GlobalVariable>(Addr)) {
@@ -727,11 +733,14 @@ void AddressSanitizer::instrumentMop(Ins
else
NumInstrumentedReads++;
- // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check.
- if (TypeSize == 8 || TypeSize == 16 ||
- TypeSize == 32 || TypeSize == 64 || TypeSize == 128)
+ unsigned Granularity = 1 << Mapping.Scale;
+ // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
+ // if the data is properly aligned.
+ if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 ||
+ TypeSize == 128) &&
+ (Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8))
return instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr, UseCalls);
- // Instrument unusual size (but still multiple of 8).
+ // Instrument unusual size or unusual alignment.
// We can not do it with a single check, so we do 1-byte check for the first
// and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
// to report the actual access size.
@@ -1328,6 +1337,7 @@ bool AddressSanitizer::runOnFunction(Fun
SmallVector<Instruction*, 16> PointerComparisonsOrSubtracts;
int NumAllocas = 0;
bool IsWrite;
+ unsigned Alignment;
// Fill the set of memory operations to instrument.
for (Function::iterator FI = F.begin(), FE = F.end();
@@ -1338,7 +1348,7 @@ bool AddressSanitizer::runOnFunction(Fun
for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
BI != BE; ++BI) {
if (LooksLikeCodeInBug11395(BI)) return false;
- if (Value *Addr = isInterestingMemoryAccess(BI, &IsWrite)) {
+ if (Value *Addr = isInterestingMemoryAccess(BI, &IsWrite, &Alignment)) {
if (ClOpt && ClOptSameTemp) {
if (!TempsToInstrument.insert(Addr))
continue; // We've seen this temp in the current BB.
@@ -1390,7 +1400,7 @@ bool AddressSanitizer::runOnFunction(Fun
Instruction *Inst = ToInstrument[i];
if (ClDebugMin < 0 || ClDebugMax < 0 ||
(NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
- if (isInterestingMemoryAccess(Inst, &IsWrite))
+ if (isInterestingMemoryAccess(Inst, &IsWrite, &Alignment))
instrumentMop(Inst, UseCalls);
else
instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
Modified: llvm/trunk/test/Instrumentation/AddressSanitizer/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/basic.ll?rev=209508&r1=209507&r2=209508&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/basic.ll (original)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/basic.ll Fri May 23 06:52:07 2014
@@ -34,7 +34,7 @@ define i32 @test_load(i32* %a) sanitize_
entry:
- %tmp1 = load i32* %a
+ %tmp1 = load i32* %a, align 4
ret i32 %tmp1
}
@@ -66,7 +66,7 @@ define void @test_store(i32* %a) sanitiz
;
entry:
- store i32 42, i32* %a
+ store i32 42, i32* %a, align 4
ret void
}
@@ -115,6 +115,18 @@ define void @i40test(i40* %a, i40* %b) n
; CHECK: __asan_report_store_n{{.*}}, i64 5)
; CHECK: ret void
+define void @i64test_align1(i64* %b) nounwind uwtable sanitize_address {
+ entry:
+ store i64 0, i64* %b, align 1
+ ret void
+}
+
+; CHECK-LABEL: i64test_align1
+; CHECK: __asan_report_store_n{{.*}}, i64 8)
+; CHECK: __asan_report_store_n{{.*}}, i64 8)
+; CHECK: ret void
+
+
define void @i80test(i80* %a, i80* %b) nounwind uwtable sanitize_address {
entry:
%t = load i80* %a
Modified: llvm/trunk/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll?rev=209508&r1=209507&r2=209508&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll (original)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll Fri May 23 06:52:07 2014
@@ -20,10 +20,10 @@ entry:
; CHECK-CUSTOM-PREFIX: call void @__foo_load8
; CHECK-CUSTOM-PREFIX: call void @__foo_loadN
; CHECK-INLINE-NOT: call void @__asan_load
- %tmp1 = load i32* %a
- %tmp2 = load i64* %b
- %tmp3 = load i512* %c
- %tmp4 = load i80* %d
+ %tmp1 = load i32* %a, align 4
+ %tmp2 = load i64* %b, align 8
+ %tmp3 = load i512* %c, align 32
+ %tmp4 = load i80* %d, align 8
ret void
}
Modified: llvm/trunk/test/Instrumentation/AddressSanitizer/test64.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/test64.ll?rev=209508&r1=209507&r2=209508&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/test64.ll (original)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/test64.ll Fri May 23 06:52:07 2014
@@ -6,7 +6,7 @@ entry:
%tmp1 = load i32* %a, align 4
ret i32 %tmp1
}
-; CHECK: @read_4_bytes
+; CHECK-LABEL: @read_4_bytes
; CHECK-NOT: ret
; CHECK: lshr {{.*}} 3
; Check for ASAN's Offset for 64-bit (7fff8000)
@@ -19,8 +19,10 @@ entry:
ret void
}
-; CHECK: @example_atomicrmw
+; CHECK-LABEL: @example_atomicrmw
; CHECK: lshr {{.*}} 3
+; CHECK: __asan_report_store8
+; CHECK-NOT: __asan_report
; CHECK: atomicrmw
; CHECK: ret
@@ -30,7 +32,9 @@ entry:
ret void
}
-; CHECK: @example_cmpxchg
+; CHECK-LABEL: @example_cmpxchg
; CHECK: lshr {{.*}} 3
+; CHECK: __asan_report_store8
+; CHECK-NOT: __asan_report
; CHECK: cmpxchg
; CHECK: ret
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