[llvm] r299697 - [asan] Fix dead stripping of globals on Linux.
Evgeniy Stepanov via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 6 12:55:18 PDT 2017
Author: eugenis
Date: Thu Apr 6 14:55:17 2017
New Revision: 299697
URL: http://llvm.org/viewvc/llvm-project?rev=299697&view=rev
Log:
[asan] Fix dead stripping of globals on Linux.
Use a combination of !associated, comdat, @llvm.compiler.used and
custom sections to allow dead stripping of globals and their asan
metadata. Sometimes.
Currently this works on LLD, which supports SHF_LINK_ORDER with
sh_link pointing to the associated section.
This also works on BFD, which seems to treat comdats as
all-or-nothing with respect to linker GC. There is a weird quirk
where the "first" global in each link is never GC-ed because of the
section symbols.
At this moment it does not work on Gold (as in the globals are never
stripped).
This is a re-land of r298158 rebased on D31358. This time,
asan.module_ctor is put in a comdat as well to avoid quadratic
behavior in Gold.
Modified:
llvm/trunk/include/llvm/Transforms/Utils/ModuleUtils.h
llvm/trunk/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
llvm/trunk/lib/Transforms/Utils/ModuleUtils.cpp
llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll
llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll
llvm/trunk/test/Instrumentation/AddressSanitizer/instrument_global.ll
Modified: llvm/trunk/include/llvm/Transforms/Utils/ModuleUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/ModuleUtils.h?rev=299697&r1=299696&r2=299697&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/ModuleUtils.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/ModuleUtils.h Thu Apr 6 14:55:17 2017
@@ -84,6 +84,17 @@ void appendToCompilerUsed(Module &M, Arr
void filterDeadComdatFunctions(
Module &M, SmallVectorImpl<Function *> &DeadComdatFunctions);
+/// \brief Produce a unique identifier for this module by taking the MD5 sum of
+/// the names of the module's strong external symbols.
+///
+/// This identifier is normally guaranteed to be unique, or the program would
+/// fail to link due to multiply defined symbols.
+///
+/// If the module has no strong external symbols (such a module may still have a
+/// semantic effect if it performs global initialization), we cannot produce a
+/// unique identifier for this module, so we return the empty string.
+std::string getUniqueModuleId(Module *M);
+
} // End llvm namespace
#endif // LLVM_TRANSFORMS_UTILS_MODULEUTILS_H
Modified: llvm/trunk/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp?rev=299697&r1=299696&r2=299697&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp Thu Apr 6 14:55:17 2017
@@ -30,42 +30,11 @@
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/FunctionAttrs.h"
#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
namespace {
-// Produce a unique identifier for this module by taking the MD5 sum of the
-// names of the module's strong external symbols. This identifier is
-// normally guaranteed to be unique, or the program would fail to link due to
-// multiply defined symbols.
-//
-// If the module has no strong external symbols (such a module may still have a
-// semantic effect if it performs global initialization), we cannot produce a
-// unique identifier for this module, so we return the empty string, which
-// causes the entire module to be written as a regular LTO module.
-std::string getModuleId(Module *M) {
- MD5 Md5;
- bool ExportsSymbols = false;
- for (auto &GV : M->global_values()) {
- if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
- !GV.hasExternalLinkage())
- continue;
- ExportsSymbols = true;
- Md5.update(GV.getName());
- Md5.update(ArrayRef<uint8_t>{0});
- }
-
- if (!ExportsSymbols)
- return "";
-
- MD5::MD5Result R;
- Md5.final(R);
-
- SmallString<32> Str;
- MD5::stringifyResult(R, Str);
- return ("$" + Str).str();
-}
-
// Promote each local-linkage entity defined by ExportM and used by ImportM by
// changing visibility and appending the given ModuleId.
void promoteInternals(Module &ExportM, Module &ImportM, StringRef ModuleId) {
@@ -237,7 +206,7 @@ void forEachVirtualFunction(Constant *C,
void splitAndWriteThinLTOBitcode(
raw_ostream &OS, raw_ostream *ThinLinkOS,
function_ref<AAResults &(Function &)> AARGetter, Module &M) {
- std::string ModuleId = getModuleId(&M);
+ std::string ModuleId = getUniqueModuleId(&M);
if (ModuleId.empty()) {
// We couldn't generate a module ID for this module, just write it out as a
// regular LTO module.
Modified: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp?rev=299697&r1=299696&r2=299697&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp Thu Apr 6 14:55:17 2017
@@ -101,6 +101,10 @@ static const char *const kAsanRegisterIm
"__asan_register_image_globals";
static const char *const kAsanUnregisterImageGlobalsName =
"__asan_unregister_image_globals";
+static const char *const kAsanRegisterElfGlobalsName =
+ "__asan_register_elf_globals";
+static const char *const kAsanUnregisterElfGlobalsName =
+ "__asan_unregister_elf_globals";
static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
static const char *const kAsanInitName = "__asan_init";
@@ -120,8 +124,11 @@ static const char *const kAsanPoisonStac
"__asan_poison_stack_memory";
static const char *const kAsanUnpoisonStackMemoryName =
"__asan_unpoison_stack_memory";
+
+// ASan version script has __asan_* wildcard. Triple underscore prevents a
+// linker (gold) warning about attempting to export a local symbol.
static const char *const kAsanGlobalsRegisteredFlagName =
- "__asan_globals_registered";
+ "___asan_globals_registered";
static const char *const kAsanOptionDetectUseAfterReturn =
"__asan_option_detect_stack_use_after_return";
@@ -610,6 +617,10 @@ private:
void InstrumentGlobalsCOFF(IRBuilder<> &IRB, Module &M,
ArrayRef<GlobalVariable *> ExtendedGlobals,
ArrayRef<Constant *> MetadataInitializers);
+ void InstrumentGlobalsELF(IRBuilder<> &IRB, Module &M,
+ ArrayRef<GlobalVariable *> ExtendedGlobals,
+ ArrayRef<Constant *> MetadataInitializers,
+ const std::string &UniqueModuleId);
void InstrumentGlobalsMachO(IRBuilder<> &IRB, Module &M,
ArrayRef<GlobalVariable *> ExtendedGlobals,
ArrayRef<Constant *> MetadataInitializers);
@@ -620,7 +631,8 @@ private:
GlobalVariable *CreateMetadataGlobal(Module &M, Constant *Initializer,
StringRef OriginalName);
- void SetComdatForGlobalMetadata(GlobalVariable *G, GlobalVariable *Metadata);
+ void SetComdatForGlobalMetadata(GlobalVariable *G, GlobalVariable *Metadata,
+ StringRef InternalSuffix);
IRBuilder<> CreateAsanModuleDtor(Module &M);
bool ShouldInstrumentGlobal(GlobalVariable *G);
@@ -645,6 +657,8 @@ private:
Function *AsanUnregisterGlobals;
Function *AsanRegisterImageGlobals;
Function *AsanUnregisterImageGlobals;
+ Function *AsanRegisterElfGlobals;
+ Function *AsanUnregisterElfGlobals;
Function *AsanCtorFunction = nullptr;
Function *AsanDtorFunction = nullptr;
@@ -1602,12 +1616,22 @@ void AddressSanitizerModule::initializeC
checkSanitizerInterfaceFunction(M.getOrInsertFunction(
kAsanUnregisterImageGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
AsanUnregisterImageGlobals->setLinkage(Function::ExternalLinkage);
+
+ AsanRegisterElfGlobals = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kAsanRegisterElfGlobalsName, IRB.getVoidTy(),
+ IntptrTy, IntptrTy, IntptrTy, nullptr));
+ AsanRegisterElfGlobals->setLinkage(Function::ExternalLinkage);
+
+ AsanUnregisterElfGlobals = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kAsanUnregisterElfGlobalsName, IRB.getVoidTy(),
+ IntptrTy, IntptrTy, IntptrTy, nullptr));
+ AsanUnregisterElfGlobals->setLinkage(Function::ExternalLinkage);
}
// Put the metadata and the instrumented global in the same group. This ensures
// that the metadata is discarded if the instrumented global is discarded.
void AddressSanitizerModule::SetComdatForGlobalMetadata(
- GlobalVariable *G, GlobalVariable *Metadata) {
+ GlobalVariable *G, GlobalVariable *Metadata, StringRef InternalSuffix) {
Module &M = *G->getParent();
Comdat *C = G->getComdat();
if (!C) {
@@ -1617,7 +1641,15 @@ void AddressSanitizerModule::SetComdatFo
assert(G->hasLocalLinkage());
G->setName(Twine(kAsanGenPrefix) + "_anon_global");
}
- C = M.getOrInsertComdat(G->getName());
+
+ if (!InternalSuffix.empty() && G->hasLocalLinkage()) {
+ std::string Name = G->getName();
+ Name += InternalSuffix;
+ C = M.getOrInsertComdat(Name);
+ } else {
+ C = M.getOrInsertComdat(G->getName());
+ }
+
// Make this IMAGE_COMDAT_SELECT_NODUPLICATES on COFF.
if (TargetTriple.isOSBinFormatCOFF())
C->setSelectionKind(Comdat::NoDuplicates);
@@ -1671,10 +1703,69 @@ void AddressSanitizerModule::InstrumentG
"global metadata will not be padded appropriately");
Metadata->setAlignment(SizeOfGlobalStruct);
- SetComdatForGlobalMetadata(G, Metadata);
+ SetComdatForGlobalMetadata(G, Metadata, "");
}
}
+void AddressSanitizerModule::InstrumentGlobalsELF(
+ IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
+ ArrayRef<Constant *> MetadataInitializers,
+ const std::string &UniqueModuleId) {
+ assert(ExtendedGlobals.size() == MetadataInitializers.size());
+
+ SmallVector<GlobalValue *, 16> MetadataGlobals(ExtendedGlobals.size());
+ for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
+ GlobalVariable *G = ExtendedGlobals[i];
+ GlobalVariable *Metadata =
+ CreateMetadataGlobal(M, MetadataInitializers[i], G->getName());
+ MDNode *MD = MDNode::get(M.getContext(), ValueAsMetadata::get(G));
+ Metadata->setMetadata(LLVMContext::MD_associated, MD);
+ MetadataGlobals[i] = Metadata;
+
+ SetComdatForGlobalMetadata(G, Metadata, UniqueModuleId);
+ }
+
+ // Update llvm.compiler.used, adding the new metadata globals. This is
+ // needed so that during LTO these variables stay alive.
+ if (!MetadataGlobals.empty())
+ appendToCompilerUsed(M, MetadataGlobals);
+
+ // RegisteredFlag serves two purposes. First, we can pass it to dladdr()
+ // to look up the loaded image that contains it. Second, we can store in it
+ // whether registration has already occurred, to prevent duplicate
+ // registration.
+ //
+ // Common linkage ensures that there is only one global per shared library.
+ GlobalVariable *RegisteredFlag = new GlobalVariable(
+ M, IntptrTy, false, GlobalVariable::CommonLinkage,
+ ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
+ RegisteredFlag->setVisibility(GlobalVariable::HiddenVisibility);
+
+ // Create start and stop symbols.
+ GlobalVariable *StartELFMetadata = new GlobalVariable(
+ M, IntptrTy, false, GlobalVariable::ExternalWeakLinkage, nullptr,
+ "__start_" + getGlobalMetadataSection());
+ StartELFMetadata->setVisibility(GlobalVariable::HiddenVisibility);
+ GlobalVariable *StopELFMetadata = new GlobalVariable(
+ M, IntptrTy, false, GlobalVariable::ExternalWeakLinkage, nullptr,
+ "__stop_" + getGlobalMetadataSection());
+ StopELFMetadata->setVisibility(GlobalVariable::HiddenVisibility);
+
+ // Create a call to register the globals with the runtime.
+ IRB.CreateCall(AsanRegisterElfGlobals,
+ {IRB.CreatePointerCast(RegisteredFlag, IntptrTy),
+ IRB.CreatePointerCast(StartELFMetadata, IntptrTy),
+ IRB.CreatePointerCast(StopELFMetadata, IntptrTy)});
+
+ // We also need to unregister globals at the end, e.g., when a shared library
+ // gets closed.
+ IRBuilder<> IRB_Dtor = CreateAsanModuleDtor(M);
+ IRB_Dtor.CreateCall(AsanUnregisterElfGlobals,
+ {IRB.CreatePointerCast(RegisteredFlag, IntptrTy),
+ IRB.CreatePointerCast(StartELFMetadata, IntptrTy),
+ IRB.CreatePointerCast(StopELFMetadata, IntptrTy)});
+}
+
void AddressSanitizerModule::InstrumentGlobalsMachO(
IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
ArrayRef<Constant *> MetadataInitializers) {
@@ -1923,7 +2014,13 @@ bool AddressSanitizerModule::InstrumentG
Initializers[i] = Initializer;
}
- if (TargetTriple.isOSBinFormatCOFF()) {
+ std::string ELFUniqueModuleId =
+ TargetTriple.isOSBinFormatELF() ? getUniqueModuleId(&M) : "";
+
+ if (!ELFUniqueModuleId.empty()) {
+ InstrumentGlobalsELF(IRB, M, NewGlobals, Initializers, ELFUniqueModuleId);
+ *CtorComdat = true;
+ } else if (TargetTriple.isOSBinFormatCOFF()) {
InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
} else if (ShouldUseMachOGlobalsSection()) {
InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
Modified: llvm/trunk/lib/Transforms/Utils/ModuleUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/ModuleUtils.cpp?rev=299697&r1=299696&r2=299697&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/ModuleUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/ModuleUtils.cpp Thu Apr 6 14:55:17 2017
@@ -237,3 +237,35 @@ void llvm::filterDeadComdatFunctions(
ComdatEntriesCovered.end();
});
}
+
+std::string llvm::getUniqueModuleId(Module *M) {
+ MD5 Md5;
+ bool ExportsSymbols = false;
+ auto AddGlobal = [&](GlobalValue &GV) {
+ if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
+ !GV.hasExternalLinkage())
+ return;
+ ExportsSymbols = true;
+ Md5.update(GV.getName());
+ Md5.update(ArrayRef<uint8_t>{0});
+ };
+
+ for (auto &F : *M)
+ AddGlobal(F);
+ for (auto &GV : M->globals())
+ AddGlobal(GV);
+ for (auto &GA : M->aliases())
+ AddGlobal(GA);
+ for (auto &IF : M->ifuncs())
+ AddGlobal(IF);
+
+ if (!ExportsSymbols)
+ return "";
+
+ MD5::MD5Result R;
+ Md5.final(R);
+
+ SmallString<32> Str;
+ MD5::stringifyResult(R, Str);
+ return ("$" + Str).str();
+}
Modified: llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll?rev=299697&r1=299696&r2=299697&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll (original)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll Thu Apr 6 14:55:17 2017
@@ -12,17 +12,23 @@ target triple = "x86_64-unknown-linux-gn
@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_asan_globals.cpp, i8* null }]
; Check that globals were instrumented:
-; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, align 32
-; CHECK: @.str = internal unnamed_addr constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, align 32
+
+; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, comdat, align 32
+; CHECK: @.str = internal unnamed_addr constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, comdat($".str${{[01-9a-f]+}}"), align 32
; Check emitted location descriptions:
; CHECK: [[VARNAME:@__asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
; CHECK: [[FILENAME:@__asan_gen_.[0-9]+]] = private unnamed_addr constant [22 x i8] c"/tmp/asan-globals.cpp\00", align 1
; CHECK: [[LOCDESCR:@__asan_gen_.[0-9]+]] = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* [[FILENAME]], i32 5, i32 5 }
+; CHECK: @__asan_global_global = {{.*}}i64 ptrtoint ({ i32, [60 x i8] }* @global to i64){{.*}} section "asan_globals"{{.*}}, !associated
+; CHECK: @__asan_global_.str = {{.*}}i64 ptrtoint ({ [14 x i8], [50 x i8] }* @.str to i64){{.*}} section "asan_globals"{{.*}}, !associated
+
+; The metadata has to be inserted to llvm.compiler.used to avoid being stripped
+; during LTO.
+; CHECK: @llvm.compiler.used {{.*}} @__asan_global_global {{.*}} section "llvm.metadata"
; Check that location descriptors and global names were passed into __asan_register_globals:
-; CHECK: i64 ptrtoint ([7 x i8]* [[VARNAME]] to i64)
-; CHECK: i64 ptrtoint ({ [22 x i8]*, i32, i32 }* [[LOCDESCR]] to i64)
+; CHECK: call void @__asan_register_elf_globals(i64 ptrtoint (i64* @___asan_globals_registered to i64), i64 ptrtoint (i64* @__start_asan_globals to i64), i64 ptrtoint (i64* @__stop_asan_globals to i64))
; Function Attrs: nounwind sanitize_address
define internal void @__cxx_global_var_init() #0 section ".text.startup" {
Modified: llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll?rev=299697&r1=299696&r2=299697&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll (original)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll Thu Apr 6 14:55:17 2017
@@ -26,16 +26,16 @@ target triple = "x86_64-apple-macosx10.1
; CHECK: @llvm.compiler.used {{.*}} @__asan_binder_global {{.*}} section "llvm.metadata"
; Test that there is the flag global variable:
-; CHECK: @__asan_globals_registered = common hidden global i64 0
+; CHECK: @___asan_globals_registered = common hidden global i64 0
; Test that __asan_register_image_globals is invoked from the constructor:
; CHECK-LABEL: define internal void @asan.module_ctor
; CHECK-NOT: ret
-; CHECK: call void @__asan_register_image_globals(i64 ptrtoint (i64* @__asan_globals_registered to i64))
+; CHECK: call void @__asan_register_image_globals(i64 ptrtoint (i64* @___asan_globals_registered to i64))
; CHECK: ret
; Test that __asan_unregister_image_globals is invoked from the destructor:
; CHECK-LABEL: define internal void @asan.module_dtor
; CHECK-NOT: ret
-; CHECK: call void @__asan_unregister_image_globals(i64 ptrtoint (i64* @__asan_globals_registered to i64))
+; CHECK: call void @__asan_unregister_image_globals(i64 ptrtoint (i64* @___asan_globals_registered to i64))
; CHECK: ret
Modified: llvm/trunk/test/Instrumentation/AddressSanitizer/instrument_global.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/instrument_global.ll?rev=299697&r1=299696&r2=299697&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/instrument_global.ll (original)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/instrument_global.ll Thu Apr 6 14:55:17 2017
@@ -73,10 +73,10 @@ entry:
; CHECK-LABEL: define internal void @asan.module_ctor
; CHECK-NOT: ret
-; CHECK: call void @__asan_register_globals
+; CHECK: call void @__asan_register_elf_globals
; CHECK: ret
; CHECK-LABEL: define internal void @asan.module_dtor
; CHECK-NOT: ret
-; CHECK: call void @__asan_unregister_globals
+; CHECK: call void @__asan_unregister_elf_globals
; CHECK: ret
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