[clang] 61e36e8 - [safestack] Support safestack in stack size diagnostics
Paul Kirth via cfe-commits
cfe-commits at lists.llvm.org
Wed Apr 20 11:29:48 PDT 2022
Author: Paul Kirth
Date: 2022-04-20T18:29:40Z
New Revision: 61e36e87df1a4ad11f752d66c90e124101fe4023
URL: https://github.com/llvm/llvm-project/commit/61e36e87df1a4ad11f752d66c90e124101fe4023
DIFF: https://github.com/llvm/llvm-project/commit/61e36e87df1a4ad11f752d66c90e124101fe4023.diff
LOG: [safestack] Support safestack in stack size diagnostics
Current stack size diagnostics ignore the size of the unsafe stack.
This patch attaches the size of the static portion of the unsafe stack
to the function as metadata, which can be used by the backend to emit
diagnostics regarding stack usage.
Reviewed By: phosek, mcgrathr
Differential Revision: https://reviews.llvm.org/D119996
Added:
clang/test/Frontend/stack-usage-safestack.c
Modified:
llvm/include/llvm/CodeGen/MachineFrameInfo.h
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
llvm/lib/CodeGen/MachineFunction.cpp
llvm/lib/CodeGen/PrologEpilogInserter.cpp
llvm/lib/CodeGen/SafeStack.cpp
llvm/test/CodeGen/X86/warn-stack.ll
llvm/test/Transforms/SafeStack/ARM/debug.ll
Removed:
################################################################################
diff --git a/clang/test/Frontend/stack-usage-safestack.c b/clang/test/Frontend/stack-usage-safestack.c
new file mode 100644
index 0000000000000..888d40cf31866
--- /dev/null
+++ b/clang/test/Frontend/stack-usage-safestack.c
@@ -0,0 +1,20 @@
+/// Check that stack frame size warnings behave the same when safe stack is enabled
+
+// RUN: %clang_cc1 %s -fwarn-stack-size=48 -S -o - -triple=i386-apple-darwin 2>&1 | FileCheck --check-prefix=REGULAR %s
+// RUN: %clang_cc1 %s -fwarn-stack-size=1060 -S -o - -triple=i386-apple-darwin 2>&1 | FileCheck --check-prefix=IGNORE %s
+
+// RUN: %clang_cc1 %s -fsanitize=safe-stack -fwarn-stack-size=48 -S -o - -triple=i386-apple-darwin 2>&1 | FileCheck --check-prefix=SAFESTACK %s
+// RUN: %clang_cc1 %s -fsanitize=safe-stack -fwarn-stack-size=1060 -S -o - -triple=i386-apple-darwin 2>&1 | FileCheck --check-prefix=IGNORE %s
+
+extern void init(char *buf, int size);
+extern int use_buf(char *buf, int size);
+
+// REGULAR: warning: stack frame size ([[#]]) exceeds limit ([[#]]) in 'stackSizeWarning'
+// SAFESTACK: warning: stack frame size ([[#]]) exceeds limit ([[#]]) in 'stackSizeWarning'
+// IGNORE-NOT: stack frame size ([[#]]) exceeds limit ([[#]]) in 'stackSizeWarning'
+void stackSizeWarning() {
+ char buf[1024];
+ init(buf, sizeof(buf));
+ if (buf[0] < 42)
+ use_buf(buf, sizeof(buf));
+}
diff --git a/llvm/include/llvm/CodeGen/MachineFrameInfo.h b/llvm/include/llvm/CodeGen/MachineFrameInfo.h
index 2d018aa73fec1..dfedf14ec118b 100644
--- a/llvm/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/llvm/include/llvm/CodeGen/MachineFrameInfo.h
@@ -334,6 +334,9 @@ class MachineFrameInfo {
/// Not null, if shrink-wrapping found a better place for the epilogue.
MachineBasicBlock *Restore = nullptr;
+ /// Size of the UnsafeStack Frame
+ uint64_t UnsafeStackSize = 0;
+
public:
explicit MachineFrameInfo(unsigned StackAlignment, bool StackRealignable,
bool ForcedRealign)
@@ -787,6 +790,9 @@ class MachineFrameInfo {
MachineBasicBlock *getRestorePoint() const { return Restore; }
void setRestorePoint(MachineBasicBlock *NewRestore) { Restore = NewRestore; }
+ uint64_t getUnsafeStackSize() const { return UnsafeStackSize; }
+ void setUnsafeStackSize(uint64_t Size) { UnsafeStackSize = Size; }
+
/// Return a set of physical registers that are pristine.
///
/// Pristine registers hold a value that is useless to the current function,
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 01f6334021c28..ea8a86b2e3757 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1354,7 +1354,8 @@ void AsmPrinter::emitStackSizeSection(const MachineFunction &MF) {
OutStreamer->SwitchSection(StackSizeSection);
const MCSymbol *FunctionSymbol = getFunctionBegin();
- uint64_t StackSize = FrameInfo.getStackSize();
+ uint64_t StackSize =
+ FrameInfo.getStackSize() + FrameInfo.getUnsafeStackSize();
OutStreamer->emitSymbolValue(FunctionSymbol, TM.getProgramPointerSize());
OutStreamer->emitULEB128IntValue(StackSize);
@@ -1369,7 +1370,8 @@ void AsmPrinter::emitStackUsage(const MachineFunction &MF) {
return;
const MachineFrameInfo &FrameInfo = MF.getFrameInfo();
- uint64_t StackSize = FrameInfo.getStackSize();
+ uint64_t StackSize =
+ FrameInfo.getStackSize() + FrameInfo.getUnsafeStackSize();
if (StackUsageStream == nullptr) {
std::error_code EC;
diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index db9108872ed44..06830e852a286 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -107,6 +107,27 @@ static const char *getPropertyName(MachineFunctionProperties::Property Prop) {
llvm_unreachable("Invalid machine function property");
}
+void setUnsafeStackSize(const Function &F, MachineFrameInfo &FrameInfo) {
+ if (!F.hasFnAttribute(Attribute::SafeStack))
+ return;
+
+ auto *Existing =
+ dyn_cast_or_null<MDTuple>(F.getMetadata(LLVMContext::MD_annotation));
+
+ if (!Existing || Existing->getNumOperands() != 2)
+ return;
+
+ auto *MetadataName = "unsafe-stack-size";
+ if (auto &N = Existing->getOperand(0)) {
+ if (cast<MDString>(N.get())->getString() == MetadataName) {
+ if (auto &Op = Existing->getOperand(1)) {
+ auto Val = mdconst::extract<ConstantInt>(Op)->getZExtValue();
+ FrameInfo.setUnsafeStackSize(Val);
+ }
+ }
+ }
+}
+
// Pin the vtable to this file.
void MachineFunction::Delegate::anchor() {}
@@ -175,6 +196,8 @@ void MachineFunction::init() {
/*ForcedRealign=*/CanRealignSP &&
F.hasFnAttribute(Attribute::StackAlignment));
+ setUnsafeStackSize(F, *FrameInfo);
+
if (F.hasFnAttribute(Attribute::StackAlignment))
FrameInfo->ensureMaxAlignment(*F.getFnStackAlign());
diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index ee22cbd5af14b..bc4545029788f 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -283,6 +283,9 @@ bool PEI::runOnMachineFunction(MachineFunction &MF) {
assert(!Failed && "Invalid warn-stack-size fn attr value");
(void)Failed;
}
+ if (MF.getFunction().hasFnAttribute(Attribute::SafeStack)) {
+ StackSize += MFI.getUnsafeStackSize();
+ }
if (StackSize > Threshold) {
DiagnosticInfoStackSize DiagStackSize(F, StackSize, Threshold, DS_Warning);
F.getContext().diagnose(DiagStackSize);
diff --git a/llvm/lib/CodeGen/SafeStack.cpp b/llvm/lib/CodeGen/SafeStack.cpp
index 1f7eac4a9b479..2c16c1912cb82 100644
--- a/llvm/lib/CodeGen/SafeStack.cpp
+++ b/llvm/lib/CodeGen/SafeStack.cpp
@@ -48,6 +48,7 @@
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
@@ -633,6 +634,13 @@ Value *SafeStack::moveStaticAllocasToUnsafeStack(
// FIXME: no need to update BasePointer in leaf functions.
unsigned FrameSize = alignTo(SSL.getFrameSize(), StackAlignment);
+ MDBuilder MDB(F.getContext());
+ SmallVector<Metadata *, 2> Data;
+ Data.push_back(MDB.createString("unsafe-stack-size"));
+ Data.push_back(MDB.createConstant(ConstantInt::get(Int32Ty, FrameSize)));
+ MDNode *MD = MDTuple::get(F.getContext(), Data);
+ F.setMetadata(LLVMContext::MD_annotation, MD);
+
// Update shadow stack pointer in the function epilogue.
IRB.SetInsertPoint(BasePointer->getNextNode());
diff --git a/llvm/test/CodeGen/X86/warn-stack.ll b/llvm/test/CodeGen/X86/warn-stack.ll
index fc59c6edbee70..2e985f315e28c 100644
--- a/llvm/test/CodeGen/X86/warn-stack.ll
+++ b/llvm/test/CodeGen/X86/warn-stack.ll
@@ -21,4 +21,17 @@ entry:
ret void
}
+; Ensure that warn-stack-size also considers the size of the unsafe stack.
+; With safestack enabled the machine stack size is well below 80, but the
+; combined stack size of the machine stack and unsafe stack will exceed the
+; warning threshold
+
+; CHECK: warning: stack frame size (120) exceeds limit (80) in function 'warn_safestack'
+define void @warn_safestack() nounwind ssp safestack "warn-stack-size"="80" {
+entry:
+ %buffer = alloca [80 x i8], align 1
+ %arraydecay = getelementptr inbounds [80 x i8], [80 x i8]* %buffer, i64 0, i64 0
+ call void @doit(i8* %arraydecay) nounwind
+ ret void
+}
declare void @doit(i8*)
diff --git a/llvm/test/Transforms/SafeStack/ARM/debug.ll b/llvm/test/Transforms/SafeStack/ARM/debug.ll
index af132ae1f8ffa..2bcfeb8b01e3a 100644
--- a/llvm/test/Transforms/SafeStack/ARM/debug.ll
+++ b/llvm/test/Transforms/SafeStack/ARM/debug.ll
@@ -10,8 +10,8 @@ target triple = "armv7-pc-linux-android"
; void Capture(char*x);
; void f() { char c[16]; Capture(c); }
-; CHECK: !35 = !DILocation(line: 3, column: 11, scope: !17, inlinedAt: !36)
-; CHECK: !36 = distinct !DILocation(line: 6, scope: !27)
+; CHECK: !36 = !DILocation(line: 3, column: 11, scope: !17, inlinedAt: !37)
+; CHECK: !37 = distinct !DILocation(line: 6, scope: !27)
@addr = common local_unnamed_addr global i8*** null, align 4, !dbg !0
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