[llvm] r264645 - [asan] Support dead code stripping on Mach-O platforms
Ryan Govostes via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 28 13:28:57 PDT 2016
Author: rgov
Date: Mon Mar 28 15:28:57 2016
New Revision: 264645
URL: http://llvm.org/viewvc/llvm-project?rev=264645&view=rev
Log:
[asan] Support dead code stripping on Mach-O platforms
On OS X El Capitan and iOS 9, the linker supports a new section
attribute, live_support, which allows dead stripping to remove dead
globals along with the ASAN metadata about them.
With this change __asan_global structures are emitted in a new
__DATA,__asan_globals section on Darwin.
Additionally, there is a __DATA,__asan_liveness section with the
live_support attribute. Each entry in this section is simply a tuple
that binds together the liveness of a global variable and its ASAN
metadata structure. Thus the metadata structure will be alive if and
only if the global it references is also alive.
Review: http://reviews.llvm.org/D16737
Added:
llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll
Modified:
llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll
Modified: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp?rev=264645&r1=264644&r2=264645&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp Mon Mar 28 15:28:57 2016
@@ -92,11 +92,15 @@ static const char *const kAsanReportErro
static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
static const char *const kAsanUnregisterGlobalsName =
"__asan_unregister_globals";
+static const char *const kAsanRegisterImageGlobalsName =
+ "__asan_register_image_globals";
+static const char *const kAsanUnregisterImageGlobalsName =
+ "__asan_unregister_image_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";
static const char *const kAsanVersionCheckName =
- "__asan_version_mismatch_check_v7";
+ "__asan_version_mismatch_check_v8";
static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp";
static const char *const kAsanPtrSub = "__sanitizer_ptr_sub";
static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
@@ -110,6 +114,8 @@ static const char *const kAsanPoisonStac
"__asan_poison_stack_memory";
static const char *const kAsanUnpoisonStackMemoryName =
"__asan_unpoison_stack_memory";
+static const char *const kAsanGlobalsRegisteredFlagName =
+ "__asan_globals_registered";
static const char *const kAsanOptionDetectUAR =
"__asan_option_detect_stack_use_after_return";
@@ -534,6 +540,7 @@ class AddressSanitizerModule : public Mo
bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
bool ShouldInstrumentGlobal(GlobalVariable *G);
+ bool ShouldUseMachOGlobalsSection() const;
void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
size_t MinRedzoneSizeForGlobal() const {
@@ -551,6 +558,8 @@ class AddressSanitizerModule : public Mo
Function *AsanUnpoisonGlobals;
Function *AsanRegisterGlobals;
Function *AsanUnregisterGlobals;
+ Function *AsanRegisterImageGlobals;
+ Function *AsanUnregisterImageGlobals;
};
// Stack poisoning does not play well with exception handling.
@@ -1287,8 +1296,26 @@ bool AddressSanitizerModule::ShouldInstr
return true;
}
+// On Mach-O platforms, we emit global metadata in a separate section of the
+// binary in order to allow the linker to properly dead strip. This is only
+// supported on recent versions of ld64.
+bool AddressSanitizerModule::ShouldUseMachOGlobalsSection() const {
+ if (!TargetTriple.isOSBinFormatMachO())
+ return false;
+
+ if (TargetTriple.isMacOSX() && !TargetTriple.isMacOSXVersionLT(10, 11))
+ return true;
+ if (TargetTriple.isiOS() /* or tvOS */ && !TargetTriple.isOSVersionLT(9))
+ return true;
+ if (TargetTriple.isWatchOS() && !TargetTriple.isOSVersionLT(2))
+ return true;
+
+ return false;
+}
+
void AddressSanitizerModule::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
+
// Declare our poisoning and unpoisoning functions.
AsanPoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
@@ -1296,6 +1323,7 @@ void AddressSanitizerModule::initializeC
AsanUnpoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
kAsanUnpoisonGlobalsName, IRB.getVoidTy(), nullptr));
AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage);
+
// Declare functions that register/unregister globals.
AsanRegisterGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
@@ -1304,6 +1332,18 @@ void AddressSanitizerModule::initializeC
M.getOrInsertFunction(kAsanUnregisterGlobalsName, IRB.getVoidTy(),
IntptrTy, IntptrTy, nullptr));
AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
+
+ // Declare the functions that find globals in a shared object and then invoke
+ // the (un)register function on them.
+ AsanRegisterImageGlobals = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kAsanRegisterImageGlobalsName,
+ IRB.getVoidTy(), IntptrTy, nullptr));
+ AsanRegisterImageGlobals->setLinkage(Function::ExternalLinkage);
+
+ AsanUnregisterImageGlobals = checkSanitizerInterfaceFunction(
+ M.getOrInsertFunction(kAsanUnregisterImageGlobalsName,
+ IRB.getVoidTy(), IntptrTy, nullptr));
+ AsanUnregisterImageGlobals->setLinkage(Function::ExternalLinkage);
}
// This function replaces all global variables with new variables that have
@@ -1442,28 +1482,84 @@ bool AddressSanitizerModule::InstrumentG
DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
}
- ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
- GlobalVariable *AllGlobals = new GlobalVariable(
- M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
- ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
+
+ GlobalVariable *AllGlobals = nullptr;
+ GlobalVariable *RegisteredFlag = nullptr;
+
+ // On recent Mach-O platforms, we emit the global metadata in a way that
+ // allows the linker to properly strip dead globals.
+ if (ShouldUseMachOGlobalsSection()) {
+ // 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 allows us to coalesce needles defined in each object
+ // file so that there's only one per shared library.
+ RegisteredFlag = new GlobalVariable(
+ M, IntptrTy, false, GlobalVariable::CommonLinkage,
+ ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
+
+ // We also emit a structure which binds the liveness of the global
+ // variable to the metadata struct.
+ StructType *LivenessTy = StructType::get(IntptrTy, IntptrTy, nullptr);
+
+ for (size_t i = 0; i < n; i++) {
+ GlobalVariable *Metadata = new GlobalVariable(
+ M, GlobalStructTy, false, GlobalVariable::InternalLinkage,
+ Initializers[i], "");
+ Metadata->setSection("__DATA,__asan_globals,regular");
+ Metadata->setAlignment(1); // don't leave padding in between
+
+ auto LivenessBinder = ConstantStruct::get(LivenessTy,
+ Initializers[i]->getAggregateElement(0u),
+ ConstantExpr::getPointerCast(Metadata, IntptrTy),
+ nullptr);
+ GlobalVariable *Liveness = new GlobalVariable(
+ M, LivenessTy, false, GlobalVariable::InternalLinkage,
+ LivenessBinder, "");
+ Liveness->setSection("__DATA,__asan_liveness,regular,live_support");
+ }
+ } else {
+ // On all other platfoms, we just emit an array of global metadata
+ // structures.
+ ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
+ AllGlobals = new GlobalVariable(
+ M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
+ ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
+ }
// Create calls for poisoning before initializers run and unpoisoning after.
if (HasDynamicallyInitializedGlobals)
createInitializerPoisonCalls(M, ModuleName);
- IRB.CreateCall(AsanRegisterGlobals,
- {IRB.CreatePointerCast(AllGlobals, IntptrTy),
- ConstantInt::get(IntptrTy, n)});
- // We also need to unregister globals at the end, e.g. when a shared library
+ // Create a call to register the globals with the runtime.
+ if (ShouldUseMachOGlobalsSection()) {
+ IRB.CreateCall(AsanRegisterImageGlobals,
+ {IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
+ } else {
+ IRB.CreateCall(AsanRegisterGlobals,
+ {IRB.CreatePointerCast(AllGlobals, IntptrTy),
+ ConstantInt::get(IntptrTy, n)});
+ }
+
+ // We also need to unregister globals at the end, e.g., when a shared library
// gets closed.
Function *AsanDtorFunction =
Function::Create(FunctionType::get(Type::getVoidTy(*C), false),
GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
- IRB_Dtor.CreateCall(AsanUnregisterGlobals,
- {IRB.CreatePointerCast(AllGlobals, IntptrTy),
- ConstantInt::get(IntptrTy, n)});
+
+ if (ShouldUseMachOGlobalsSection()) {
+ IRB_Dtor.CreateCall(AsanUnregisterImageGlobals,
+ {IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
+ } else {
+ IRB_Dtor.CreateCall(AsanUnregisterGlobals,
+ {IRB.CreatePointerCast(AllGlobals, IntptrTy),
+ ConstantInt::get(IntptrTy, n)});
+ }
+
appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
DEBUG(dbgs() << M);
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=264645&r1=264644&r2=264645&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll (original)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata.ll Mon Mar 28 15:28:57 2016
@@ -20,7 +20,7 @@ target triple = "x86_64-unknown-linux-gn
; 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 that location decriptors and global names were passed into __asan_register_globals:
+; 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)
Added: 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=264645&view=auto
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll (added)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/global_metadata_darwin.ll Mon Mar 28 15:28:57 2016
@@ -0,0 +1,37 @@
+; Test that global metadata is placed in a separate section on Mach-O platforms,
+; allowing dead stripping to be performed, and that the appropriate runtime
+; routines are invoked.
+
+; RUN: opt < %s -asan -asan-module -S | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+ at global = global [1 x i32] zeroinitializer, align 4
+
+!llvm.asan.globals = !{!0}
+
+!0 = !{[1 x i32]* @global, !1, !"global", i1 false, i1 false}
+!1 = !{!"test-globals.c", i32 1, i32 5}
+
+
+; Test that there is a Needle global variable:
+; CHECK: @__asan_needle = internal global i64 0
+
+; Find the metadata for @global:
+; CHECK: [[METADATA:@[0-9]+]] = internal global {{.*}} @global {{.*}} section "__DATA,__asan_globals,regular", align 1
+
+; Find the liveness binder for @global and its metadata:
+; CHECK: @{{[0-9]+}} = internal global {{.*}} @global {{.*}} [[METADATA]] {{.*}} section "__DATA,__asan_liveness,regular,live_support"
+
+; Test that __asan_apply_to_globals is invoked from the constructor:
+; CHECK-LABEL: define internal void @asan.module_ctor
+; CHECK-NOT: ret
+; CHECK: call void @__asan_apply_to_globals(i64 ptrtoint (void (i64, i64)* @__asan_register_globals to i64), i64 ptrtoint (i64* @__asan_needle to i64))
+; CHECK: ret
+
+; Test that __asan_apply_to_globals is invoked from the destructor:
+; CHECK-LABEL: define internal void @asan.module_dtor
+; CHECK-NOT: ret
+; CHECK: call void @__asan_apply_to_globals(i64 ptrtoint (void (i64, i64)* @__asan_unregister_globals to i64), i64 ptrtoint (i64* @__asan_needle to i64))
+; CHECK: ret
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