[asan] Ensure __asan_register_elf_globals is called in COMDAT asan.module_ctor (#67745)
On ELF platforms, when there is no global variable and the unique module ID is
non-empty, COMDAT asan.module_ctor is created with no
`__asan_register_elf_globals` calls. If this COMDAT is the prevailing copy
selected by the linker, the linkage unit will have no
`__asan_register_elf_globals` call: the redzone will not be poisoned and ODR
violation checker will not work (#67677).
This behavior is benign for -fno-sanitize-address-globals-dead-stripping because
asan.module_ctor functions that call `__asan_register_globals`
(`InstrumentGlobalsWithMetadataArray`) do not use COMDAT.
To fix #67677:
* Use COMDAT for -fsanitize-address-globals-dead-stripping on ELF platforms.
* Call `__asan_register_elf_globals` even if there is no global variable.
* If the unique module ID is empty, don't call SetComdatForGlobalMetadata:
placing `@.str` in a COMDAT would incorrectly discard internal COMDAT `@.str`
in other compile units.
Alternatively, when there is no global variable, asan.module_ctor is not COMDAT
and does not call `__asan_register_elf_globals`. However, the asan.module_ctor
function cannot be eliminated by the linker.
Tested the following script. Only ELF -fsanitize-address-globals-dead-stripping has changed behaviors.
```
echo > a.cc # no global variable, empty uniqueModuleId
echo 'void f() {}' > b.cc # with global variable, with uniqueModuleId
echo 'int g;' > c.cc # with global variable
for t in x86_64-linux-gnu arm64-apple-macosx x86_64-windows-msvc; do
for gc in -f{,no-}sanitize-address-globals-dead-stripping; do
for f in a.cc b.cc c.cc; do
echo /tmp/Rel/bin/clang -S --target=$t -fsanitize=address $gc $f -o -
/tmp/Rel/bin/clang -S --target=$t -fsanitize=address $gc $f -o - | sed -n '/asan.module_ctor/,/ret/p'
done
done
done
```
---
Identical to commit 16eed8c906875e748c3cb610f3dc4b875f3882aa.
6420d3301cd4f0793adcf11f59e8398db73737d8 is an incorrect revert for genuine
purely internal issues.
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index bde5fba..f4bf6db 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -819,11 +819,11 @@
private:
void initializeCallbacks(Module &M);
- bool InstrumentGlobals(IRBuilder<> &IRB, Module &M, bool *CtorComdat);
+ void instrumentGlobals(IRBuilder<> &IRB, Module &M, bool *CtorComdat);
void InstrumentGlobalsCOFF(IRBuilder<> &IRB, Module &M,
ArrayRef<GlobalVariable *> ExtendedGlobals,
ArrayRef<Constant *> MetadataInitializers);
- void InstrumentGlobalsELF(IRBuilder<> &IRB, Module &M,
+ void instrumentGlobalsELF(IRBuilder<> &IRB, Module &M,
ArrayRef<GlobalVariable *> ExtendedGlobals,
ArrayRef<Constant *> MetadataInitializers,
const std::string &UniqueModuleId);
@@ -2177,7 +2177,7 @@
appendToCompilerUsed(M, MetadataGlobals);
}
-void ModuleAddressSanitizer::InstrumentGlobalsELF(
+void ModuleAddressSanitizer::instrumentGlobalsELF(
IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
ArrayRef<Constant *> MetadataInitializers,
const std::string &UniqueModuleId) {
@@ -2187,7 +2187,7 @@
// false negative odr violations at link time. If odr indicators are used, we
// keep the comdat sections, as link time odr violations will be dectected on
// the odr indicator symbols.
- bool UseComdatForGlobalsGC = UseOdrIndicator;
+ bool UseComdatForGlobalsGC = UseOdrIndicator && !UniqueModuleId.empty();
SmallVector<GlobalValue *, 16> MetadataGlobals(ExtendedGlobals.size());
for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
@@ -2237,7 +2237,7 @@
// We also need to unregister globals at the end, e.g., when a shared library
// gets closed.
- if (DestructorKind != AsanDtorKind::None) {
+ if (DestructorKind != AsanDtorKind::None && !MetadataGlobals.empty()) {
IRBuilder<> IrbDtor(CreateAsanModuleDtor(M));
IrbDtor.CreateCall(AsanUnregisterElfGlobals,
{IRB.CreatePointerCast(RegisteredFlag, IntptrTy),
@@ -2343,10 +2343,8 @@
// redzones and inserts this function into llvm.global_ctors.
// Sets *CtorComdat to true if the global registration code emitted into the
// asan constructor is comdat-compatible.
-bool ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
+void ModuleAddressSanitizer::instrumentGlobals(IRBuilder<> &IRB, Module &M,
bool *CtorComdat) {
- *CtorComdat = false;
-
// Build set of globals that are aliased by some GA, where
// getExcludedAliasedGlobal(GA) returns the relevant GlobalVariable.
SmallPtrSet<const GlobalVariable *, 16> AliasedGlobalExclusions;
@@ -2364,11 +2362,6 @@
}
size_t n = GlobalsToChange.size();
- if (n == 0) {
- *CtorComdat = true;
- return false;
- }
-
auto &DL = M.getDataLayout();
// A global is described by a structure
@@ -2391,8 +2384,11 @@
// We shouldn't merge same module names, as this string serves as unique
// module ID in runtime.
- GlobalVariable *ModuleName = createPrivateGlobalForString(
- M, M.getModuleIdentifier(), /*AllowMerging*/ false, kAsanGenPrefix);
+ GlobalVariable *ModuleName =
+ n != 0
+ ? createPrivateGlobalForString(M, M.getModuleIdentifier(),
+ /*AllowMerging*/ false, kAsanGenPrefix)
+ : nullptr;
for (size_t i = 0; i < n; i++) {
GlobalVariable *G = GlobalsToChange[i];
@@ -2517,19 +2513,27 @@
}
appendToCompilerUsed(M, ArrayRef<GlobalValue *>(GlobalsToAddToUsedList));
- std::string ELFUniqueModuleId =
- (UseGlobalsGC && TargetTriple.isOSBinFormatELF()) ? getUniqueModuleId(&M)
- : "";
-
- if (!ELFUniqueModuleId.empty()) {
- InstrumentGlobalsELF(IRB, M, NewGlobals, Initializers, ELFUniqueModuleId);
+ if (UseGlobalsGC && TargetTriple.isOSBinFormatELF()) {
+ // Use COMDAT and register globals even if n == 0 to ensure that (a) the
+ // linkage unit will only have one module constructor, and (b) the register
+ // function will be called. The module destructor is not created when n ==
+ // 0.
*CtorComdat = true;
- } else if (UseGlobalsGC && TargetTriple.isOSBinFormatCOFF()) {
- InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
- } else if (UseGlobalsGC && ShouldUseMachOGlobalsSection()) {
- InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
+ instrumentGlobalsELF(IRB, M, NewGlobals, Initializers,
+ getUniqueModuleId(&M));
+ } else if (n == 0) {
+ // When UseGlobalsGC is false, COMDAT can still be used if n == 0, because
+ // all compile units will have identical module constructor/destructor.
+ *CtorComdat = TargetTriple.isOSBinFormatELF();
} else {
- InstrumentGlobalsWithMetadataArray(IRB, M, NewGlobals, Initializers);
+ *CtorComdat = false;
+ if (UseGlobalsGC && TargetTriple.isOSBinFormatCOFF()) {
+ InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
+ } else if (UseGlobalsGC && ShouldUseMachOGlobalsSection()) {
+ InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
+ } else {
+ InstrumentGlobalsWithMetadataArray(IRB, M, NewGlobals, Initializers);
+ }
}
// Create calls for poisoning before initializers run and unpoisoning after.
@@ -2537,7 +2541,6 @@
createInitializerPoisonCalls(M, ModuleName);
LLVM_DEBUG(dbgs() << M);
- return true;
}
uint64_t
@@ -2601,10 +2604,10 @@
assert(AsanCtorFunction || ConstructorKind == AsanCtorKind::None);
if (AsanCtorFunction) {
IRBuilder<> IRB(AsanCtorFunction->getEntryBlock().getTerminator());
- InstrumentGlobals(IRB, M, &CtorComdat);
+ instrumentGlobals(IRB, M, &CtorComdat);
} else {
IRBuilder<> IRB(*C);
- InstrumentGlobals(IRB, M, &CtorComdat);
+ instrumentGlobals(IRB, M, &CtorComdat);
}
}
diff --git a/llvm/test/Instrumentation/AddressSanitizer/basic.ll b/llvm/test/Instrumentation/AddressSanitizer/basic.ll
index 068d6d1..2064db5 100644
--- a/llvm/test/Instrumentation/AddressSanitizer/basic.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/basic.ll
@@ -210,8 +210,10 @@
;; ctor/dtor have the nounwind attribute. See uwtable.ll, they additionally have
;; the uwtable attribute with the module flag "uwtable".
-; CHECK: define internal void @asan.module_ctor() #[[#ATTR:]] {{(comdat )?}}{
+; CHECK: define internal void @asan.module_ctor() #[[#ATTR:]] comdat {
; CHECK: call void @__asan_init()
+;; __asan_register_elf_globals is called even if this module does not contain instrumented global variables.
+; CHECK: call void @__asan_register_elf_globals(i64 ptrtoint (ptr @___asan_globals_registered to i64), i64 ptrtoint (ptr @__start_asan_globals to i64), i64 ptrtoint (ptr @__stop_asan_globals to i64))
; CHECK: attributes #[[#ATTR]] = { nounwind }
diff --git a/llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll b/llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll
index 0e4d1f1..1617bf9 100644
--- a/llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll
@@ -1,8 +1,12 @@
-; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefix=CHECK %s
-; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-apple-macosx10.11.0 -S | FileCheck --check-prefix=CHECK %s
-; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-pc-windows-msvc19.0.24215 -S | FileCheck --check-prefix=CHECK %s
-; RUN: opt < %s -passes=asan -asan-globals-live-support=0 -asan-mapping-scale=5 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefixes=CHECK,CHECK-S5 %s
+; RUN: rm -rf %t && split-file %s %t && cd %t
+; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefix=CHECK %s
+; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-apple-macosx10.11.0 -S | FileCheck --check-prefix=CHECK %s
+; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-pc-windows-msvc19.0.24215 -S | FileCheck --check-prefix=CHECK %s
+; RUN: opt < a.ll -passes=asan -asan-globals-live-support=0 -asan-mapping-scale=5 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefixes=CHECK,CHECK-S5 %s
+; RUN: opt < empty.ll -passes=asan -asan-globals-live-support=0 -mtriple=x86_64-unknown-linux-gnu -S | FileCheck --check-prefix=ELF-NOGC %s
+
+;--- a.ll
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
; Globals:
@@ -59,3 +63,10 @@
!7 = !{!"/tmp/asan-globals.cpp", i32 7, i32 5}
!8 = !{!"/tmp/asan-globals.cpp", i32 12, i32 14}
!9 = !{!"/tmp/asan-globals.cpp", i32 14, i32 25}
+
+;; In the presence of instrumented global variables, asan.module_ctor do not use comdat.
+; CHECK: define internal void @asan.module_ctor() #[[#ATTR:]] {
+
+; ELF-NOGC: define internal void @asan.module_ctor() #[[#ATTR:]] comdat {
+
+;--- empty.ll
diff --git a/llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll b/llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll
index 47bb1f1..699b828 100644
--- a/llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll
@@ -4,10 +4,14 @@
; We keep using comdats for garbage collection if odr indicators are
; enabled as indicator symbols will cause link time odr violations.
; This is to fix PR 47925.
-;
-; RUN: opt < %s -passes=asan -asan-globals-live-support=1 -asan-use-odr-indicator=0 -S | FileCheck %s --check-prefixes=CHECK,NOCOMDAT
+; RUN: rm -rf %t && split-file %s %t && cd %t
+; RUN: opt < a.ll -passes=asan -asan-globals-live-support=1 -asan-use-odr-indicator=0 -S | FileCheck %s --check-prefixes=CHECK,NOCOMDAT
; Check that enabling odr indicators enables comdat for globals.
-; RUN: opt < %s -passes=asan -asan-globals-live-support=1 -S | FileCheck %s --check-prefixes=CHECK,COMDAT
+; RUN: opt < a.ll -passes=asan -asan-globals-live-support=1 -S | FileCheck %s --check-prefixes=CHECK,COMDAT
+
+; RUN: opt < no_module_id.ll -passes=asan -S | FileCheck %s --check-prefix=NOMODULEID
+
+;--- a.ll
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@@ -87,3 +91,43 @@
!7 = !{!"/tmp/asan-globals.cpp", i32 7, i32 5}
!8 = !{!"/tmp/asan-globals.cpp", i32 12, i32 14}
!9 = !{!"/tmp/asan-globals.cpp", i32 14, i32 25}
+
+;--- no_module_id.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; NOMODULEID: $asan.module_ctor = comdat any
+; NOMODULEID: $asan.module_dtor = comdat any
+
+;; Don't place the instrumented globals in a comdat when the unique module ID is empty.
+; NOMODULEID: @.str = internal constant { [4 x i8], [28 x i8] } { [4 x i8] c"str\00", [28 x i8] zeroinitializer }, align 32
+; NOMODULEID: @_ZL3buf = internal global { [4 x i8], [28 x i8] } zeroinitializer, align 32
+; NOMODULEID: @__asan_global_.str = private global {{.*}}, section "asan_globals", !associated !0
+; NOMODULEID: @__asan_global__ZL3buf = private global {{.*}}, section "asan_globals", !associated !1
+; NOMODULEID: @llvm.compiler.used = appending global [4 x ptr] [ptr @.str, ptr @_ZL3buf, ptr @__asan_global_.str, ptr @__asan_global__ZL3buf]
+
+; NOMODULEID: define internal void @asan.module_ctor() #[[#]] comdat {
+; NOMODULEID-NEXT: call void @__asan_init()
+; NOMODULEID-NEXT: call void @__asan_version_mismatch_check_v8()
+; NOMODULEID-NEXT: call void @__asan_register_elf_globals(i64 ptrtoint (ptr @___asan_globals_registered to i64), i64 ptrtoint (ptr @__start_asan_globals to i64), i64 ptrtoint (ptr @__stop_asan_globals to i64))
+; NOMODULEID-NEXT: ret void
+; NOMODULEID-NEXT: }
+
+; NOMODULEID: !0 = !{ptr @.str}
+; NOMODULEID: !1 = !{ptr @_ZL3buf}
+
+@.str = private unnamed_addr constant [4 x i8] c"str\00", align 1
+@_ZL3buf = internal unnamed_addr global [4 x i8] zeroinitializer, align 1
+@llvm.global_ctors = appending global [1 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 65535, ptr @_GLOBAL__sub_I_a.cc, ptr null }]
+
+declare void @ext(ptr noundef)
+
+; Function Attrs: uwtable
+define internal void @_GLOBAL__sub_I_a.cc() #2 section ".text.startup" {
+entry:
+ %0 = load i8, ptr @_ZL3buf, align 1
+ %inc = add i8 %0, 1
+ store i8 %inc, ptr @_ZL3buf, align 1
+ tail call void @ext(ptr noundef nonnull @.str)
+ ret void
+}
