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[asan] Set alignment of __asan_global_* globals to sizeof(GlobalStruct)

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When using profiling and ASan together (-fprofile-instr-generate -fcoverage-mapping -fsanitize=address), at least on Darwin, the section of globals that ASan emits (__asan_globals) is misaligned and starts at an odd offset. This really doesn't have anything to do with profiling, but it triggers the issue because profiling emits a string section, which can have arbitrary size.  This patch changes the alignment to sizeof(GlobalStruct).

Differential Revision: https://reviews.llvm.org/D28573

llvm-svn: 291715
This commit is contained in:
Kuba Mracek 2017-01-11 22:26:10 +00:00
parent 635a70fbaf
commit 9d8ba8e855
2 changed files with 4 additions and 7 deletions
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9
lib/Transforms/Instrumentation/AddressSanitizer.cpp
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@ -1598,8 +1598,7 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
IntptrTy, IntptrTy, IntptrTy, nullptr);
unsigned SizeOfGlobalStruct = DL.getTypeAllocSize(GlobalStructTy);
assert((isPowerOf2_32(SizeOfGlobalStruct) ||
!TargetTriple.isOSBinFormatCOFF()) &&
assert(isPowerOf2_32(SizeOfGlobalStruct) &&
"global metadata will not be padded appropriately");
SmallVector<Constant *, 16> Initializers(UseMetadataArray ? n : 0);
@ -1766,13 +1765,11 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
GlobalValue::getRealLinkageName(G->getName()));
Metadata->setSection(getGlobalMetadataSection());
// We don't want any padding, but we also need a reasonable alignment.
// The MSVC linker always inserts padding when linking incrementally. We
// cope with that by aligning each struct to its size, which must be a power
// of two.
if (TargetTriple.isOSBinFormatCOFF())
Metadata->setAlignment(SizeOfGlobalStruct);
else
Metadata->setAlignment(1); // Don't leave padding in between.
Metadata->setAlignment(SizeOfGlobalStruct);
// On platforms that support comdats, put the metadata and the
// instrumented global in the same group. This ensures that the metadata

2
test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll
View File

@ -16,7 +16,7 @@ target triple = "x86_64-apple-macosx10.11.0"
; Find the metadata for @global:
; CHECK: [[METADATA:@.+]] = internal global {{.*}} @global {{.*}} section "__DATA,__asan_globals,regular", align 1
; CHECK: [[METADATA:@.+]] = internal global {{.*}} @global {{.*}} section "__DATA,__asan_globals,regular", align 64
; Find the liveness binder for @global and its metadata:
; CHECK: @__asan_binder_global = internal global {{.*}} @global {{.*}} [[METADATA]] {{.*}} section "__DATA,__asan_liveness,regular,live_support"