Skip to content

[MTE] do not tag zero sized globals #136020

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
fmayer merged 4 commits into from
Apr 17, 2025
Merged

[MTE] do not tag zero sized globals #136020

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
dfc8659
[𝘀𝗽𝗿] changes to main this commit is based on
fmayer Apr 16, 2025
4315e7e
[𝘀𝗽𝗿] initial version
fmayer Apr 16, 2025
dbc4f44
[𝘀𝗽𝗿] changes introduced through rebase
fmayer Apr 17, 2025
d21a360
rebase
fmayer Apr 17, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 6 additions & 0 deletions clang/test/CodeGen/memtag-globals-asm.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-P
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-Q
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-R
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-S

// RUN: %clang_cc1 -O3 -S -x c++ -std=c++11 -triple aarch64-linux-android31 \
// RUN: -fsanitize=memtag-globals -o %t.out %s
Expand All @@ -43,6 +44,7 @@
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-P
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-Q
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-R
// RUN: FileCheck %s --input-file=%t.out --check-prefix=CHECK-S

/// Ensure that emulated TLS also doesn't get sanitized.
// RUN: %clang_cc1 -S -x c++ -std=c++11 -triple aarch64-linux-android31 \
Expand Down Expand Up @@ -99,6 +101,10 @@ static char* global_buffer_local_end = &global_buffer[16];
// CHECK-H: .size global_buffer_global_end, 16
char* global_buffer_global_end = &global_buffer[16];

// CHECK-S-NOT: .memtag zero_sized
struct empty {};
char zero_sized[0];

class MyClass {
public:
virtual ~MyClass() {}
Expand Down
13 changes: 9 additions & 4 deletions llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2398,6 +2398,12 @@ void AsmPrinter::emitRemarksSection(remarks::RemarkStreamer &RS) {
OutStreamer->emitBinaryData(Buf);
}

static uint64_t globalSize(const llvm::GlobalVariable &G) {
const Constant *Initializer = G.getInitializer();
return G.getParent()->getDataLayout().getTypeAllocSize(
Initializer->getType());
}

static bool shouldTagGlobal(const llvm::GlobalVariable &G) {
// We used to do this in clang, but there are optimization passes that turn
// non-constant globals into constants. So now, clang only tells us whether
Expand Down Expand Up @@ -2430,19 +2436,18 @@ static bool shouldTagGlobal(const llvm::GlobalVariable &G) {
if (G.hasSection())
return false;

return true;
return globalSize(G) > 0;
}

static void tagGlobalDefinition(Module &M, GlobalVariable *G) {
Constant *Initializer = G->getInitializer();
uint64_t SizeInBytes =
M.getDataLayout().getTypeAllocSize(Initializer->getType());
uint64_t SizeInBytes = globalSize(*G);

uint64_t NewSize = alignTo(SizeInBytes, 16);
if (SizeInBytes != NewSize) {
// Pad the initializer out to the next multiple of 16 bytes.
llvm::SmallVector<uint8_t> Init(NewSize - SizeInBytes, 0);
Constant *Padding = ConstantDataArray::get(M.getContext(), Init);
Constant *Initializer = G->getInitializer();
Initializer = ConstantStruct::getAnon({Initializer, Padding});
auto *NewGV = new GlobalVariable(
M, Initializer->getType(), G->isConstant(), G->getLinkage(),
Expand Down
Loading