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From 7db340bcc57fb7f4fabbae34b30065fbd77b0174 Mon Sep 17 00:00:00 2001
From: Leonard Grey <lgrey@chromium.org>
Date: Mon, 8 Apr 2024 16:05:52 -0400
Subject: [PATCH] -fsanitize=function: fix .subsections_via_symbols (#87527)
-fsanitize=function emits a signature and function hash before a
function. Similar to 7f6e2c9, these can be sheared off when
`.subsections_via_symbols` is used.
This change uses the same technique 7f6e2c9 introduced for prefixes:
emitting a symbol for the metadata, then marking the actual function
entry as an .alt_entry symbol.
---
llvm/include/llvm/CodeGen/AsmPrinter.h | 3 ++
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp | 43 ++++++++++++---------
llvm/test/CodeGen/AArch64/func-sanitizer.ll | 9 +++++
llvm/test/CodeGen/X86/func-sanitizer.ll | 10 +++++
4 files changed, 46 insertions(+), 19 deletions(-)
diff --git a/llvm/include/llvm/CodeGen/AsmPrinter.h b/llvm/include/llvm/CodeGen/AsmPrinter.h
index 0ac497c5f8ef..96e302859f44 100644
--- a/llvm/include/llvm/CodeGen/AsmPrinter.h
+++ b/llvm/include/llvm/CodeGen/AsmPrinter.h
@@ -840,6 +840,9 @@ private:
/// This method emits a comment next to header for the current function.
virtual void emitFunctionHeaderComment();
+ /// This method emits prefix-like data before the current function.
+ void emitFunctionPrefix(ArrayRef<const Constant *> Prefix);
+
/// Emit a blob of inline asm to the output streamer.
void
emitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 5381dfdd184c..a1d4c72d2899 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -896,6 +896,27 @@ void AsmPrinter::emitDebugValue(const MCExpr *Value, unsigned Size) const {
void AsmPrinter::emitFunctionHeaderComment() {}
+void AsmPrinter::emitFunctionPrefix(ArrayRef<const Constant *> Prefix) {
+ const Function &F = MF->getFunction();
+ if (!MAI->hasSubsectionsViaSymbols()) {
+ for (auto &C : Prefix)
+ emitGlobalConstant(F.getParent()->getDataLayout(), C);
+ return;
+ }
+ // Preserving prefix-like data on platforms which use subsections-via-symbols
+ // is a bit tricky. Here we introduce a symbol for the prefix-like data
+ // and use the .alt_entry attribute to mark the function's real entry point
+ // as an alternative entry point to the symbol that precedes the function..
+ OutStreamer->emitLabel(OutContext.createLinkerPrivateTempSymbol());
+
+ for (auto &C : Prefix) {
+ emitGlobalConstant(F.getParent()->getDataLayout(), C);
+ }
+
+ // Emit an .alt_entry directive for the actual function symbol.
+ OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_AltEntry);
+}
+
/// EmitFunctionHeader - This method emits the header for the current
/// function.
void AsmPrinter::emitFunctionHeader() {
@@ -935,23 +956,8 @@ void AsmPrinter::emitFunctionHeader() {
OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_Cold);
// Emit the prefix data.
- if (F.hasPrefixData()) {
- if (MAI->hasSubsectionsViaSymbols()) {
- // Preserving prefix data on platforms which use subsections-via-symbols
- // is a bit tricky. Here we introduce a symbol for the prefix data
- // and use the .alt_entry attribute to mark the function's real entry point
- // as an alternative entry point to the prefix-data symbol.
- MCSymbol *PrefixSym = OutContext.createLinkerPrivateTempSymbol();
- OutStreamer->emitLabel(PrefixSym);
-
- emitGlobalConstant(F.getParent()->getDataLayout(), F.getPrefixData());
-
- // Emit an .alt_entry directive for the actual function symbol.
- OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_AltEntry);
- } else {
- emitGlobalConstant(F.getParent()->getDataLayout(), F.getPrefixData());
- }
- }
+ if (F.hasPrefixData())
+ emitFunctionPrefix({F.getPrefixData()});
// Emit KCFI type information before patchable-function-prefix nops.
emitKCFITypeId(*MF);
@@ -983,8 +989,7 @@ void AsmPrinter::emitFunctionHeader() {
auto *PrologueSig = mdconst::extract<Constant>(MD->getOperand(0));
auto *TypeHash = mdconst::extract<Constant>(MD->getOperand(1));
- emitGlobalConstant(F.getParent()->getDataLayout(), PrologueSig);
- emitGlobalConstant(F.getParent()->getDataLayout(), TypeHash);
+ emitFunctionPrefix({PrologueSig, TypeHash});
}
if (isVerbose()) {
diff --git a/llvm/test/CodeGen/AArch64/func-sanitizer.ll b/llvm/test/CodeGen/AArch64/func-sanitizer.ll
index 89f23e7ed80e..de83d70a5784 100644
--- a/llvm/test/CodeGen/AArch64/func-sanitizer.ll
+++ b/llvm/test/CodeGen/AArch64/func-sanitizer.ll
@@ -1,4 +1,5 @@
; RUN: llc -mtriple=aarch64-unknown-linux-gnu < %s | FileCheck %s
+; RUN: llc -mtriple=arm64-apple-darwin < %s | FileCheck %s --check-prefix=MACHO
; CHECK-LABEL: .type _Z3funv,@function
; CHECK-NEXT: .word 3238382334 // 0xc105cafe
@@ -7,6 +8,14 @@
; CHECK-NEXT: // %bb.0:
; CHECK-NEXT: ret
+; MACHO: ltmp0:
+; MACHO-NEXT: .long 3238382334 ; 0xc105cafe
+; MACHO-NEXT: .long 42 ; 0x2a
+; MACHO-NEXT: .alt_entry __Z3funv
+; MACHO-NEXT: __Z3funv:
+; MACHO-NEXT: ; %bb.0:
+; MACHO-NEXT: ret
+
define dso_local void @_Z3funv() nounwind !func_sanitize !0 {
ret void
}
diff --git a/llvm/test/CodeGen/X86/func-sanitizer.ll b/llvm/test/CodeGen/X86/func-sanitizer.ll
index b421cb53ddfe..71f062ae2f8c 100644
--- a/llvm/test/CodeGen/X86/func-sanitizer.ll
+++ b/llvm/test/CodeGen/X86/func-sanitizer.ll
@@ -1,4 +1,5 @@
; RUN: llc -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-apple-darwin < %s | FileCheck %s --check-prefix=MACHO
; CHECK: .type _Z3funv,@function
; CHECK-NEXT: .long 3238382334 # 0xc105cafe
@@ -8,6 +9,15 @@
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: retq
+; MACHO: ltmp0:
+; MACHO-NEXT: .long 3238382334 ## 0xc105cafe
+; MACHO-NEXT: .long 42 ## 0x2a
+; MACHO-NEXT: .alt_entry __Z3funv
+; MACHO-NEXT: __Z3funv:
+; MACHO-NEXT: .cfi_startproc
+; MACHO-NEXT: # %bb.0:
+; MACHO-NEXT: retq
+
define dso_local void @_Z3funv() !func_sanitize !0 {
ret void
}
--
2.44.0.1.g9765aa7075
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