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llvm-6502/lib/Transforms/Instrumentation/AddressSanitizer.cpp
Alexey Samsonov 05e5839d4f [ASan] Change fake stack and local variables handling. 
This commit changes the way we get fake stack from ASan runtime
(to find use-after-return errors) and the way we represent local
variables:
  - __asan_stack_malloc function now returns pointer to newly allocated
    fake stack frame, or NULL if frame cannot be allocated. It doesn't
    take pointer to real stack as an input argument, it is calculated
    inside the runtime.
  - __asan_stack_free function doesn't take pointer to real stack as
    an input argument. Now this function is never called if fake stack
    frame wasn't allocated.
  - __asan_init version is bumped to reflect changes in the ABI.
  - new flag "-asan-stack-dynamic-alloca" allows to store all the
    function local variables in a dynamic alloca, instead of the static
    one. It reduces the stack space usage in use-after-return mode
    (dynamic alloca will not be called if the local variables are stored
    in a fake stack), and improves the debug info quality for local
    variables (they will not be described relatively to %rbp/%rsp, which
    are assumed to be clobbered by function calls). This flag is turned
    off by default for now, but I plan to turn it on after more
    testing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224062 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 21:53:03 +00:00

2018 lines
80 KiB
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//===-- AddressSanitizer.cpp - memory error detector ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of AddressSanitizer, an address sanity checker.
// Details of the algorithm:
// http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/SwapByteOrder.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include <algorithm>
#include <string>
#include <system_error>
using namespace llvm;
#define DEBUG_TYPE "asan"
static const uint64_t kDefaultShadowScale = 3;
static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000; // < 2G.
static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa0000;
static const uint64_t kMIPS64_ShadowOffset64 = 1ULL << 36;
static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30;
static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46;
static const size_t kMinStackMallocSize = 1 << 6; // 64B
static const size_t kMaxStackMallocSize = 1 << 16; // 64K
static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;
static const char *const kAsanModuleCtorName = "asan.module_ctor";
static const char *const kAsanModuleDtorName = "asan.module_dtor";
static const uint64_t kAsanCtorAndDtorPriority = 1;
static const char *const kAsanReportErrorTemplate = "__asan_report_";
static const char *const kAsanReportLoadN = "__asan_report_load_n";
static const char *const kAsanReportStoreN = "__asan_report_store_n";
static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
static const char *const kAsanUnregisterGlobalsName =
"__asan_unregister_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_v5";
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";
static const int kMaxAsanStackMallocSizeClass = 10;
static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_";
static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_";
static const char *const kAsanGenPrefix = "__asan_gen_";
static const char *const kSanCovGenPrefix = "__sancov_gen_";
static const char *const kAsanPoisonStackMemoryName =
"__asan_poison_stack_memory";
static const char *const kAsanUnpoisonStackMemoryName =
"__asan_unpoison_stack_memory";
static const char *const kAsanOptionDetectUAR =
"__asan_option_detect_stack_use_after_return";
#ifndef NDEBUG
static const int kAsanStackAfterReturnMagic = 0xf5;
#endif
// Accesses sizes are powers of two: 1, 2, 4, 8, 16.
static const size_t kNumberOfAccessSizes = 5;
static const unsigned kAllocaRzSize = 32;
static const unsigned kAsanAllocaLeftMagic = 0xcacacacaU;
static const unsigned kAsanAllocaRightMagic = 0xcbcbcbcbU;
static const unsigned kAsanAllocaPartialVal1 = 0xcbcbcb00U;
static const unsigned kAsanAllocaPartialVal2 = 0x000000cbU;
// Command-line flags.
// This flag may need to be replaced with -f[no-]asan-reads.
static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
cl::desc("instrument read instructions"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClInstrumentWrites("asan-instrument-writes",
cl::desc("instrument write instructions"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClInstrumentAtomics("asan-instrument-atomics",
cl::desc("instrument atomic instructions (rmw, cmpxchg)"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClAlwaysSlowPath("asan-always-slow-path",
cl::desc("use instrumentation with slow path for all accesses"),
cl::Hidden, cl::init(false));
// This flag limits the number of instructions to be instrumented
// in any given BB. Normally, this should be set to unlimited (INT_MAX),
// but due to http://llvm.org/bugs/show_bug.cgi?id=12652 we temporary
// set it to 10000.
static cl::opt<int> ClMaxInsnsToInstrumentPerBB("asan-max-ins-per-bb",
cl::init(10000),
cl::desc("maximal number of instructions to instrument in any given BB"),
cl::Hidden);
// This flag may need to be replaced with -f[no]asan-stack.
static cl::opt<bool> ClStack("asan-stack",
cl::desc("Handle stack memory"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
cl::desc("Check return-after-free"), cl::Hidden, cl::init(true));
// This flag may need to be replaced with -f[no]asan-globals.
static cl::opt<bool> ClGlobals("asan-globals",
cl::desc("Handle global objects"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClInitializers("asan-initialization-order",
cl::desc("Handle C++ initializer order"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClInvalidPointerPairs("asan-detect-invalid-pointer-pair",
cl::desc("Instrument <, <=, >, >=, - with pointer operands"),
cl::Hidden, cl::init(false));
static cl::opt<unsigned> ClRealignStack("asan-realign-stack",
cl::desc("Realign stack to the value of this flag (power of two)"),
cl::Hidden, cl::init(32));
static cl::opt<int> ClInstrumentationWithCallsThreshold(
"asan-instrumentation-with-call-threshold",
cl::desc("If the function being instrumented contains more than "
"this number of memory accesses, use callbacks instead of "
"inline checks (-1 means never use callbacks)."),
cl::Hidden, cl::init(7000));
static cl::opt<std::string> ClMemoryAccessCallbackPrefix(
"asan-memory-access-callback-prefix",
cl::desc("Prefix for memory access callbacks"), cl::Hidden,
cl::init("__asan_"));
static cl::opt<bool> ClInstrumentAllocas("asan-instrument-allocas",
cl::desc("instrument dynamic allocas"), cl::Hidden, cl::init(false));
// These flags allow to change the shadow mapping.
// The shadow mapping looks like
// Shadow = (Mem >> scale) + (1 << offset_log)
static cl::opt<int> ClMappingScale("asan-mapping-scale",
cl::desc("scale of asan shadow mapping"), cl::Hidden, cl::init(0));
// Optimization flags. Not user visible, used mostly for testing
// and benchmarking the tool.
static cl::opt<bool> ClOpt("asan-opt",
cl::desc("Optimize instrumentation"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClOptSameTemp("asan-opt-same-temp",
cl::desc("Instrument the same temp just once"), cl::Hidden,
cl::init(true));
static cl::opt<bool> ClOptGlobals("asan-opt-globals",
cl::desc("Don't instrument scalar globals"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClCheckLifetime("asan-check-lifetime",
cl::desc("Use llvm.lifetime intrinsics to insert extra checks"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClDynamicAllocaStack(
"asan-stack-dynamic-alloca",
cl::desc("Use dynamic alloca to represent stack variables"), cl::Hidden,
cl::init(false));
// Debug flags.
static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden,
cl::init(0));
static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"),
cl::Hidden, cl::init(0));
static cl::opt<std::string> ClDebugFunc("asan-debug-func",
cl::Hidden, cl::desc("Debug func"));
static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
cl::Hidden, cl::init(-1));
static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug man inst"),
cl::Hidden, cl::init(-1));
STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
STATISTIC(NumInstrumentedDynamicAllocas,
"Number of instrumented dynamic allocas");
STATISTIC(NumOptimizedAccessesToGlobalArray,
"Number of optimized accesses to global arrays");
STATISTIC(NumOptimizedAccessesToGlobalVar,
"Number of optimized accesses to global vars");
namespace {
/// Frontend-provided metadata for source location.
struct LocationMetadata {
StringRef Filename;
int LineNo;
int ColumnNo;
LocationMetadata() : Filename(), LineNo(0), ColumnNo(0) {}
bool empty() const { return Filename.empty(); }
void parse(MDNode *MDN) {
assert(MDN->getNumOperands() == 3);
MDString *MDFilename = cast<MDString>(MDN->getOperand(0));
Filename = MDFilename->getString();
LineNo =
mdconst::extract<ConstantInt>(MDN->getOperand(1))->getLimitedValue();
ColumnNo =
mdconst::extract<ConstantInt>(MDN->getOperand(2))->getLimitedValue();
}
};
/// Frontend-provided metadata for global variables.
class GlobalsMetadata {
public:
struct Entry {
Entry()
: SourceLoc(), Name(), IsDynInit(false),
IsBlacklisted(false) {}
LocationMetadata SourceLoc;
StringRef Name;
bool IsDynInit;
bool IsBlacklisted;
};
GlobalsMetadata() : inited_(false) {}
void init(Module& M) {
assert(!inited_);
inited_ = true;
NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals");
if (!Globals)
return;
for (auto MDN : Globals->operands()) {
// Metadata node contains the global and the fields of "Entry".
assert(MDN->getNumOperands() == 5);
auto *GV = mdconst::extract_or_null<GlobalVariable>(MDN->getOperand(0));
// The optimizer may optimize away a global entirely.
if (!GV)
continue;
// We can already have an entry for GV if it was merged with another
// global.
Entry &E = Entries[GV];
if (auto *Loc = cast_or_null<MDNode>(MDN->getOperand(1)))
E.SourceLoc.parse(Loc);
if (auto *Name = cast_or_null<MDString>(MDN->getOperand(2)))
E.Name = Name->getString();
ConstantInt *IsDynInit =
mdconst::extract<ConstantInt>(MDN->getOperand(3));
E.IsDynInit |= IsDynInit->isOne();
ConstantInt *IsBlacklisted =
mdconst::extract<ConstantInt>(MDN->getOperand(4));
E.IsBlacklisted |= IsBlacklisted->isOne();
}
}
/// Returns metadata entry for a given global.
Entry get(GlobalVariable *G) const {
auto Pos = Entries.find(G);
return (Pos != Entries.end()) ? Pos->second : Entry();
}
private:
bool inited_;
DenseMap<GlobalVariable*, Entry> Entries;
};
/// This struct defines the shadow mapping using the rule:
/// shadow = (mem >> Scale) ADD-or-OR Offset.
struct ShadowMapping {
int Scale;
uint64_t Offset;
bool OrShadowOffset;
};
static ShadowMapping getShadowMapping(Triple &TargetTriple, int LongSize) {
bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android;
bool IsIOS = TargetTriple.isiOS();
bool IsFreeBSD = TargetTriple.isOSFreeBSD();
bool IsLinux = TargetTriple.isOSLinux();
bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64 ||
TargetTriple.getArch() == llvm::Triple::ppc64le;
bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
bool IsMIPS32 = TargetTriple.getArch() == llvm::Triple::mips ||
TargetTriple.getArch() == llvm::Triple::mipsel;
bool IsMIPS64 = TargetTriple.getArch() == llvm::Triple::mips64 ||
TargetTriple.getArch() == llvm::Triple::mips64el;
ShadowMapping Mapping;
if (LongSize == 32) {
if (IsAndroid)
Mapping.Offset = 0;
else if (IsMIPS32)
Mapping.Offset = kMIPS32_ShadowOffset32;
else if (IsFreeBSD)
Mapping.Offset = kFreeBSD_ShadowOffset32;
else if (IsIOS)
Mapping.Offset = kIOSShadowOffset32;
else
Mapping.Offset = kDefaultShadowOffset32;
} else { // LongSize == 64
if (IsPPC64)
Mapping.Offset = kPPC64_ShadowOffset64;
else if (IsFreeBSD)
Mapping.Offset = kFreeBSD_ShadowOffset64;
else if (IsLinux && IsX86_64)
Mapping.Offset = kSmallX86_64ShadowOffset;
else if (IsMIPS64)
Mapping.Offset = kMIPS64_ShadowOffset64;
else
Mapping.Offset = kDefaultShadowOffset64;
}
Mapping.Scale = kDefaultShadowScale;
if (ClMappingScale) {
Mapping.Scale = ClMappingScale;
}
// OR-ing shadow offset if more efficient (at least on x86) if the offset
// is a power of two, but on ppc64 we have to use add since the shadow
// offset is not necessary 1/8-th of the address space.
Mapping.OrShadowOffset = !IsPPC64 && !(Mapping.Offset & (Mapping.Offset - 1));
return Mapping;
}
static size_t RedzoneSizeForScale(int MappingScale) {
// Redzone used for stack and globals is at least 32 bytes.
// For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
return std::max(32U, 1U << MappingScale);
}
/// AddressSanitizer: instrument the code in module to find memory bugs.
struct AddressSanitizer : public FunctionPass {
AddressSanitizer() : FunctionPass(ID) {
initializeAddressSanitizerPass(*PassRegistry::getPassRegistry());
}
const char *getPassName() const override {
return "AddressSanitizerFunctionPass";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<DominatorTreeWrapperPass>();
}
void instrumentMop(Instruction *I, bool UseCalls);
void instrumentPointerComparisonOrSubtraction(Instruction *I);
void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore,
Value *Addr, uint32_t TypeSize, bool IsWrite,
Value *SizeArgument, bool UseCalls);
Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
Value *ShadowValue, uint32_t TypeSize);
Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
bool IsWrite, size_t AccessSizeIndex,
Value *SizeArgument);
void instrumentMemIntrinsic(MemIntrinsic *MI);
Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
bool runOnFunction(Function &F) override;
bool maybeInsertAsanInitAtFunctionEntry(Function &F);
bool doInitialization(Module &M) override;
static char ID; // Pass identification, replacement for typeid
DominatorTree &getDominatorTree() const { return *DT; }
private:
void initializeCallbacks(Module &M);
bool LooksLikeCodeInBug11395(Instruction *I);
bool GlobalIsLinkerInitialized(GlobalVariable *G);
LLVMContext *C;
const DataLayout *DL;
Triple TargetTriple;
int LongSize;
Type *IntptrTy;
ShadowMapping Mapping;
DominatorTree *DT;
Function *AsanCtorFunction;
Function *AsanInitFunction;
Function *AsanHandleNoReturnFunc;
Function *AsanPtrCmpFunction, *AsanPtrSubFunction;
// This array is indexed by AccessIsWrite and log2(AccessSize).
Function *AsanErrorCallback[2][kNumberOfAccessSizes];
Function *AsanMemoryAccessCallback[2][kNumberOfAccessSizes];
// This array is indexed by AccessIsWrite.
Function *AsanErrorCallbackSized[2],
*AsanMemoryAccessCallbackSized[2];
Function *AsanMemmove, *AsanMemcpy, *AsanMemset;
InlineAsm *EmptyAsm;
GlobalsMetadata GlobalsMD;
friend struct FunctionStackPoisoner;
};
class AddressSanitizerModule : public ModulePass {
public:
AddressSanitizerModule() : ModulePass(ID) {}
bool runOnModule(Module &M) override;
static char ID; // Pass identification, replacement for typeid
const char *getPassName() const override {
return "AddressSanitizerModule";
}
private:
void initializeCallbacks(Module &M);
bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
bool ShouldInstrumentGlobal(GlobalVariable *G);
void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
size_t MinRedzoneSizeForGlobal() const {
return RedzoneSizeForScale(Mapping.Scale);
}
GlobalsMetadata GlobalsMD;
Type *IntptrTy;
LLVMContext *C;
const DataLayout *DL;
Triple TargetTriple;
ShadowMapping Mapping;
Function *AsanPoisonGlobals;
Function *AsanUnpoisonGlobals;
Function *AsanRegisterGlobals;
Function *AsanUnregisterGlobals;
};
// Stack poisoning does not play well with exception handling.
// When an exception is thrown, we essentially bypass the code
// that unpoisones the stack. This is why the run-time library has
// to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
// stack in the interceptor. This however does not work inside the
// actual function which catches the exception. Most likely because the
// compiler hoists the load of the shadow value somewhere too high.
// This causes asan to report a non-existing bug on 453.povray.
// It sounds like an LLVM bug.
struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
Function &F;
AddressSanitizer &ASan;
DIBuilder DIB;
LLVMContext *C;
Type *IntptrTy;
Type *IntptrPtrTy;
ShadowMapping Mapping;
SmallVector<AllocaInst*, 16> AllocaVec;
SmallVector<Instruction*, 8> RetVec;
unsigned StackAlignment;
Function *AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1],
*AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1];
Function *AsanPoisonStackMemoryFunc, *AsanUnpoisonStackMemoryFunc;
// Stores a place and arguments of poisoning/unpoisoning call for alloca.
struct AllocaPoisonCall {
IntrinsicInst *InsBefore;
AllocaInst *AI;
uint64_t Size;
bool DoPoison;
};
SmallVector<AllocaPoisonCall, 8> AllocaPoisonCallVec;
// Stores left and right redzone shadow addresses for dynamic alloca
// and pointer to alloca instruction itself.
// LeftRzAddr is a shadow address for alloca left redzone.
// RightRzAddr is a shadow address for alloca right redzone.
struct DynamicAllocaCall {
AllocaInst *AI;
Value *LeftRzAddr;
Value *RightRzAddr;
bool Poison;
explicit DynamicAllocaCall(AllocaInst *AI,
Value *LeftRzAddr = nullptr,
Value *RightRzAddr = nullptr)
: AI(AI), LeftRzAddr(LeftRzAddr), RightRzAddr(RightRzAddr), Poison(true)
{}
};
SmallVector<DynamicAllocaCall, 1> DynamicAllocaVec;
// Maps Value to an AllocaInst from which the Value is originated.
typedef DenseMap<Value*, AllocaInst*> AllocaForValueMapTy;
AllocaForValueMapTy AllocaForValue;
bool HasNonEmptyInlineAsm;
std::unique_ptr<CallInst> EmptyInlineAsm;
FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
: F(F), ASan(ASan), DIB(*F.getParent(), /*AllowUnresolved*/ false),
C(ASan.C), IntptrTy(ASan.IntptrTy),
IntptrPtrTy(PointerType::get(IntptrTy, 0)), Mapping(ASan.Mapping),
StackAlignment(1 << Mapping.Scale), HasNonEmptyInlineAsm(false),
EmptyInlineAsm(CallInst::Create(ASan.EmptyAsm)) {}
bool runOnFunction() {
if (!ClStack) return false;
// Collect alloca, ret, lifetime instructions etc.
for (BasicBlock *BB : depth_first(&F.getEntryBlock()))
visit(*BB);
if (AllocaVec.empty() && DynamicAllocaVec.empty()) return false;
initializeCallbacks(*F.getParent());
poisonStack();
if (ClDebugStack) {
DEBUG(dbgs() << F);
}
return true;
}
// Finds all Alloca instructions and puts
// poisoned red zones around all of them.
// Then unpoison everything back before the function returns.
void poisonStack();
// ----------------------- Visitors.
/// \brief Collect all Ret instructions.
void visitReturnInst(ReturnInst &RI) {
RetVec.push_back(&RI);
}
// Unpoison dynamic allocas redzones.
void unpoisonDynamicAlloca(DynamicAllocaCall &AllocaCall) {
if (!AllocaCall.Poison)
return;
for (auto Ret : RetVec) {
IRBuilder<> IRBRet(Ret);
PointerType *Int32PtrTy = PointerType::getUnqual(IRBRet.getInt32Ty());
Value *Zero = Constant::getNullValue(IRBRet.getInt32Ty());
Value *PartialRzAddr = IRBRet.CreateSub(AllocaCall.RightRzAddr,
ConstantInt::get(IntptrTy, 4));
IRBRet.CreateStore(Zero, IRBRet.CreateIntToPtr(AllocaCall.LeftRzAddr,
Int32PtrTy));
IRBRet.CreateStore(Zero, IRBRet.CreateIntToPtr(PartialRzAddr,
Int32PtrTy));
IRBRet.CreateStore(Zero, IRBRet.CreateIntToPtr(AllocaCall.RightRzAddr,
Int32PtrTy));
}
}
// Right shift for BigEndian and left shift for LittleEndian.
Value *shiftAllocaMagic(Value *Val, IRBuilder<> &IRB, Value *Shift) {
return ASan.DL->isLittleEndian() ? IRB.CreateShl(Val, Shift)
: IRB.CreateLShr(Val, Shift);
}
// Compute PartialRzMagic for dynamic alloca call. Since we don't know the
// size of requested memory until runtime, we should compute it dynamically.
// If PartialSize is 0, PartialRzMagic would contain kAsanAllocaRightMagic,
// otherwise it would contain the value that we will use to poison the
// partial redzone for alloca call.
Value *computePartialRzMagic(Value *PartialSize, IRBuilder<> &IRB);
// Deploy and poison redzones around dynamic alloca call. To do this, we
// should replace this call with another one with changed parameters and
// replace all its uses with new address, so
// addr = alloca type, old_size, align
// is replaced by
// new_size = (old_size + additional_size) * sizeof(type)
// tmp = alloca i8, new_size, max(align, 32)
// addr = tmp + 32 (first 32 bytes are for the left redzone).
// Additional_size is added to make new memory allocation contain not only
// requested memory, but also left, partial and right redzones.
// After that, we should poison redzones:
// (1) Left redzone with kAsanAllocaLeftMagic.
// (2) Partial redzone with the value, computed in runtime by
// computePartialRzMagic function.
// (3) Right redzone with kAsanAllocaRightMagic.
void handleDynamicAllocaCall(DynamicAllocaCall &AllocaCall);
/// \brief Collect Alloca instructions we want (and can) handle.
void visitAllocaInst(AllocaInst &AI) {
if (!isInterestingAlloca(AI)) return;
StackAlignment = std::max(StackAlignment, AI.getAlignment());
if (isDynamicAlloca(AI))
DynamicAllocaVec.push_back(DynamicAllocaCall(&AI));
else
AllocaVec.push_back(&AI);
}
/// \brief Collect lifetime intrinsic calls to check for use-after-scope
/// errors.
void visitIntrinsicInst(IntrinsicInst &II) {
if (!ClCheckLifetime) return;
Intrinsic::ID ID = II.getIntrinsicID();
if (ID != Intrinsic::lifetime_start &&
ID != Intrinsic::lifetime_end)
return;
// Found lifetime intrinsic, add ASan instrumentation if necessary.
ConstantInt *Size = dyn_cast<ConstantInt>(II.getArgOperand(0));
// If size argument is undefined, don't do anything.
if (Size->isMinusOne()) return;
// Check that size doesn't saturate uint64_t and can
// be stored in IntptrTy.
const uint64_t SizeValue = Size->getValue().getLimitedValue();
if (SizeValue == ~0ULL ||
!ConstantInt::isValueValidForType(IntptrTy, SizeValue))
return;
// Find alloca instruction that corresponds to llvm.lifetime argument.
AllocaInst *AI = findAllocaForValue(II.getArgOperand(1));
if (!AI) return;
bool DoPoison = (ID == Intrinsic::lifetime_end);
AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison};
AllocaPoisonCallVec.push_back(APC);
}
void visitCallInst(CallInst &CI) {
HasNonEmptyInlineAsm |=
CI.isInlineAsm() && !CI.isIdenticalTo(EmptyInlineAsm.get());
}
// ---------------------- Helpers.
void initializeCallbacks(Module &M);
bool doesDominateAllExits(const Instruction *I) const {
for (auto Ret : RetVec) {
if (!ASan.getDominatorTree().dominates(I, Ret))
return false;
}
return true;
}
bool isDynamicAlloca(AllocaInst &AI) const {
return AI.isArrayAllocation() || !AI.isStaticAlloca();
}
// Check if we want (and can) handle this alloca.
bool isInterestingAlloca(AllocaInst &AI) const {
return (AI.getAllocatedType()->isSized() &&
// alloca() may be called with 0 size, ignore it.
getAllocaSizeInBytes(&AI) > 0);
}
uint64_t getAllocaSizeInBytes(AllocaInst *AI) const {
Type *Ty = AI->getAllocatedType();
uint64_t SizeInBytes = ASan.DL->getTypeAllocSize(Ty);
return SizeInBytes;
}
/// Finds alloca where the value comes from.
AllocaInst *findAllocaForValue(Value *V);
void poisonRedZones(ArrayRef<uint8_t> ShadowBytes, IRBuilder<> &IRB,
Value *ShadowBase, bool DoPoison);
void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> &IRB, bool DoPoison);
void SetShadowToStackAfterReturnInlined(IRBuilder<> &IRB, Value *ShadowBase,
int Size);
Value *createAllocaForLayout(IRBuilder<> &IRB, const ASanStackFrameLayout &L,
bool Dynamic);
PHINode *createPHI(IRBuilder<> &IRB, Value *Cond, Value *ValueIfTrue,
Instruction *ThenTerm, Value *ValueIfFalse);
};
} // namespace
char AddressSanitizer::ID = 0;
INITIALIZE_PASS_BEGIN(AddressSanitizer, "asan",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs.",
false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(AddressSanitizer, "asan",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs.",
false, false)
FunctionPass *llvm::createAddressSanitizerFunctionPass() {
return new AddressSanitizer();
}
char AddressSanitizerModule::ID = 0;
INITIALIZE_PASS(AddressSanitizerModule, "asan-module",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs."
"ModulePass", false, false)
ModulePass *llvm::createAddressSanitizerModulePass() {
return new AddressSanitizerModule();
}
static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
size_t Res = countTrailingZeros(TypeSize / 8);
assert(Res < kNumberOfAccessSizes);
return Res;
}
// \brief Create a constant for Str so that we can pass it to the run-time lib.
static GlobalVariable *createPrivateGlobalForString(
Module &M, StringRef Str, bool AllowMerging) {
Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
// We use private linkage for module-local strings. If they can be merged
// with another one, we set the unnamed_addr attribute.
GlobalVariable *GV =
new GlobalVariable(M, StrConst->getType(), true,
GlobalValue::PrivateLinkage, StrConst, kAsanGenPrefix);
if (AllowMerging)
GV->setUnnamedAddr(true);
GV->setAlignment(1); // Strings may not be merged w/o setting align 1.
return GV;
}
/// \brief Create a global describing a source location.
static GlobalVariable *createPrivateGlobalForSourceLoc(Module &M,
LocationMetadata MD) {
Constant *LocData[] = {
createPrivateGlobalForString(M, MD.Filename, true),
ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.LineNo),
ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.ColumnNo),
};
auto LocStruct = ConstantStruct::getAnon(LocData);
auto GV = new GlobalVariable(M, LocStruct->getType(), true,
GlobalValue::PrivateLinkage, LocStruct,
kAsanGenPrefix);
GV->setUnnamedAddr(true);
return GV;
}
static bool GlobalWasGeneratedByAsan(GlobalVariable *G) {
return G->getName().find(kAsanGenPrefix) == 0 ||
G->getName().find(kSanCovGenPrefix) == 0;
}
Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
// Shadow >> scale
Shadow = IRB.CreateLShr(Shadow, Mapping.Scale);
if (Mapping.Offset == 0)
return Shadow;
// (Shadow >> scale) | offset
if (Mapping.OrShadowOffset)
return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
else
return IRB.CreateAdd(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
}
// Instrument memset/memmove/memcpy
void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
IRBuilder<> IRB(MI);
if (isa<MemTransferInst>(MI)) {
IRB.CreateCall3(
isa<MemMoveInst>(MI) ? AsanMemmove : AsanMemcpy,
IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
IRB.CreatePointerCast(MI->getOperand(1), IRB.getInt8PtrTy()),
IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false));
} else if (isa<MemSetInst>(MI)) {
IRB.CreateCall3(
AsanMemset,
IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false),
IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false));
}
MI->eraseFromParent();
}
// If I is an interesting memory access, return the PointerOperand
// and set IsWrite/Alignment. Otherwise return nullptr.
static Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
unsigned *Alignment) {
// Skip memory accesses inserted by another instrumentation.
if (I->getMetadata("nosanitize"))
return nullptr;
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!ClInstrumentReads) return nullptr;
*IsWrite = false;
*Alignment = LI->getAlignment();
return LI->getPointerOperand();
}
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (!ClInstrumentWrites) return nullptr;
*IsWrite = true;
*Alignment = SI->getAlignment();
return SI->getPointerOperand();
}
if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
*Alignment = 0;
return RMW->getPointerOperand();
}
if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
*Alignment = 0;
return XCHG->getPointerOperand();
}
return nullptr;
}
static bool isPointerOperand(Value *V) {
return V->getType()->isPointerTy() || isa<PtrToIntInst>(V);
}
// This is a rough heuristic; it may cause both false positives and
// false negatives. The proper implementation requires cooperation with
// the frontend.
static bool isInterestingPointerComparisonOrSubtraction(Instruction *I) {
if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) {
if (!Cmp->isRelational())
return false;
} else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
if (BO->getOpcode() != Instruction::Sub)
return false;
} else {
return false;
}
if (!isPointerOperand(I->getOperand(0)) ||
!isPointerOperand(I->getOperand(1)))
return false;
return true;
}
bool AddressSanitizer::GlobalIsLinkerInitialized(GlobalVariable *G) {
// If a global variable does not have dynamic initialization we don't
// have to instrument it. However, if a global does not have initializer
// at all, we assume it has dynamic initializer (in other TU).
return G->hasInitializer() && !GlobalsMD.get(G).IsDynInit;
}
void
AddressSanitizer::instrumentPointerComparisonOrSubtraction(Instruction *I) {
IRBuilder<> IRB(I);
Function *F = isa<ICmpInst>(I) ? AsanPtrCmpFunction : AsanPtrSubFunction;
Value *Param[2] = {I->getOperand(0), I->getOperand(1)};
for (int i = 0; i < 2; i++) {
if (Param[i]->getType()->isPointerTy())
Param[i] = IRB.CreatePointerCast(Param[i], IntptrTy);
}
IRB.CreateCall2(F, Param[0], Param[1]);
}
void AddressSanitizer::instrumentMop(Instruction *I, bool UseCalls) {
bool IsWrite = false;
unsigned Alignment = 0;
Value *Addr = isInterestingMemoryAccess(I, &IsWrite, &Alignment);
assert(Addr);
if (ClOpt && ClOptGlobals) {
if (GlobalVariable *G = dyn_cast<GlobalVariable>(Addr)) {
// If initialization order checking is disabled, a simple access to a
// dynamically initialized global is always valid.
if (!ClInitializers || GlobalIsLinkerInitialized(G)) {
NumOptimizedAccessesToGlobalVar++;
return;
}
}
ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr);
if (CE && CE->isGEPWithNoNotionalOverIndexing()) {
if (GlobalVariable *G = dyn_cast<GlobalVariable>(CE->getOperand(0))) {
if (CE->getOperand(1)->isNullValue() && GlobalIsLinkerInitialized(G)) {
NumOptimizedAccessesToGlobalArray++;
return;
}
}
}
}
Type *OrigPtrTy = Addr->getType();
Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
assert(OrigTy->isSized());
uint32_t TypeSize = DL->getTypeStoreSizeInBits(OrigTy);
assert((TypeSize % 8) == 0);
if (IsWrite)
NumInstrumentedWrites++;
else
NumInstrumentedReads++;
unsigned Granularity = 1 << Mapping.Scale;
// Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
// if the data is properly aligned.
if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 ||
TypeSize == 128) &&
(Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8))
return instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr, UseCalls);
// Instrument unusual size or unusual alignment.
// We can not do it with a single check, so we do 1-byte check for the first
// and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
// to report the actual access size.
IRBuilder<> IRB(I);
Value *Size = ConstantInt::get(IntptrTy, TypeSize / 8);
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
if (UseCalls) {
IRB.CreateCall2(AsanMemoryAccessCallbackSized[IsWrite], AddrLong, Size);
} else {
Value *LastByte = IRB.CreateIntToPtr(
IRB.CreateAdd(AddrLong, ConstantInt::get(IntptrTy, TypeSize / 8 - 1)),
OrigPtrTy);
instrumentAddress(I, I, Addr, 8, IsWrite, Size, false);
instrumentAddress(I, I, LastByte, 8, IsWrite, Size, false);
}
}
// Validate the result of Module::getOrInsertFunction called for an interface
// function of AddressSanitizer. If the instrumented module defines a function
// with the same name, their prototypes must match, otherwise
// getOrInsertFunction returns a bitcast.
static Function *checkInterfaceFunction(Constant *FuncOrBitcast) {
if (isa<Function>(FuncOrBitcast)) return cast<Function>(FuncOrBitcast);
FuncOrBitcast->dump();
report_fatal_error("trying to redefine an AddressSanitizer "
"interface function");
}
Instruction *AddressSanitizer::generateCrashCode(
Instruction *InsertBefore, Value *Addr,
bool IsWrite, size_t AccessSizeIndex, Value *SizeArgument) {
IRBuilder<> IRB(InsertBefore);
CallInst *Call = SizeArgument
? IRB.CreateCall2(AsanErrorCallbackSized[IsWrite], Addr, SizeArgument)
: IRB.CreateCall(AsanErrorCallback[IsWrite][AccessSizeIndex], Addr);
// We don't do Call->setDoesNotReturn() because the BB already has
// UnreachableInst at the end.
// This EmptyAsm is required to avoid callback merge.
IRB.CreateCall(EmptyAsm);
return Call;
}
Value *AddressSanitizer::createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
Value *ShadowValue,
uint32_t TypeSize) {
size_t Granularity = 1 << Mapping.Scale;
// Addr & (Granularity - 1)
Value *LastAccessedByte = IRB.CreateAnd(
AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
// (Addr & (Granularity - 1)) + size - 1
if (TypeSize / 8 > 1)
LastAccessedByte = IRB.CreateAdd(
LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
// (uint8_t) ((Addr & (Granularity-1)) + size - 1)
LastAccessedByte = IRB.CreateIntCast(
LastAccessedByte, ShadowValue->getType(), false);
// ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
}
void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
Instruction *InsertBefore, Value *Addr,
uint32_t TypeSize, bool IsWrite,
Value *SizeArgument, bool UseCalls) {
IRBuilder<> IRB(InsertBefore);
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
if (UseCalls) {
IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][AccessSizeIndex],
AddrLong);
return;
}
Type *ShadowTy = IntegerType::get(
*C, std::max(8U, TypeSize >> Mapping.Scale));
Type *ShadowPtrTy = PointerType::get(ShadowTy, 0);
Value *ShadowPtr = memToShadow(AddrLong, IRB);
Value *CmpVal = Constant::getNullValue(ShadowTy);
Value *ShadowValue = IRB.CreateLoad(
IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));
Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
size_t Granularity = 1 << Mapping.Scale;
TerminatorInst *CrashTerm = nullptr;
if (ClAlwaysSlowPath || (TypeSize < 8 * Granularity)) {
// We use branch weights for the slow path check, to indicate that the slow
// path is rarely taken. This seems to be the case for SPEC benchmarks.
TerminatorInst *CheckTerm =
SplitBlockAndInsertIfThen(Cmp, InsertBefore, false,
MDBuilder(*C).createBranchWeights(1, 100000));
assert(dyn_cast<BranchInst>(CheckTerm)->isUnconditional());
BasicBlock *NextBB = CheckTerm->getSuccessor(0);
IRB.SetInsertPoint(CheckTerm);
Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
BasicBlock *CrashBlock =
BasicBlock::Create(*C, "", NextBB->getParent(), NextBB);
CrashTerm = new UnreachableInst(*C, CrashBlock);
BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
ReplaceInstWithInst(CheckTerm, NewTerm);
} else {
CrashTerm = SplitBlockAndInsertIfThen(Cmp, InsertBefore, true);
}
Instruction *Crash = generateCrashCode(
CrashTerm, AddrLong, IsWrite, AccessSizeIndex, SizeArgument);
Crash->setDebugLoc(OrigIns->getDebugLoc());
}
void AddressSanitizerModule::poisonOneInitializer(Function &GlobalInit,
GlobalValue *ModuleName) {
// Set up the arguments to our poison/unpoison functions.
IRBuilder<> IRB(GlobalInit.begin()->getFirstInsertionPt());
// Add a call to poison all external globals before the given function starts.
Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
// Add calls to unpoison all globals before each return instruction.
for (auto &BB : GlobalInit.getBasicBlockList())
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
CallInst::Create(AsanUnpoisonGlobals, "", RI);
}
void AddressSanitizerModule::createInitializerPoisonCalls(
Module &M, GlobalValue *ModuleName) {
GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
for (Use &OP : CA->operands()) {
if (isa<ConstantAggregateZero>(OP))
continue;
ConstantStruct *CS = cast<ConstantStruct>(OP);
// Must have a function or null ptr.
if (Function* F = dyn_cast<Function>(CS->getOperand(1))) {
if (F->getName() == kAsanModuleCtorName) continue;
ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
// Don't instrument CTORs that will run before asan.module_ctor.
if (Priority->getLimitedValue() <= kAsanCtorAndDtorPriority) continue;
poisonOneInitializer(*F, ModuleName);
}
}
}
bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
Type *Ty = cast<PointerType>(G->getType())->getElementType();
DEBUG(dbgs() << "GLOBAL: " << *G << "\n");
if (GlobalsMD.get(G).IsBlacklisted) return false;
if (!Ty->isSized()) return false;
if (!G->hasInitializer()) return false;
if (GlobalWasGeneratedByAsan(G)) return false; // Our own global.
// Touch only those globals that will not be defined in other modules.
// Don't handle ODR linkage types and COMDATs since other modules may be built
// without ASan.
if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
G->getLinkage() != GlobalVariable::PrivateLinkage &&
G->getLinkage() != GlobalVariable::InternalLinkage)
return false;
if (G->hasComdat())
return false;
// Two problems with thread-locals:
// - The address of the main thread's copy can't be computed at link-time.
// - Need to poison all copies, not just the main thread's one.
if (G->isThreadLocal())
return false;
// For now, just ignore this Global if the alignment is large.
if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
if (G->hasSection()) {
StringRef Section(G->getSection());
if (TargetTriple.isOSBinFormatMachO()) {
StringRef ParsedSegment, ParsedSection;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(Section, ParsedSegment,
ParsedSection, TAA, TAAParsed,
StubSize);
if (!ErrorCode.empty()) {
report_fatal_error("Invalid section specifier '" + ParsedSection +
"': " + ErrorCode + ".");
}
// Ignore the globals from the __OBJC section. The ObjC runtime assumes
// those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
// them.
if (ParsedSegment == "__OBJC" ||
(ParsedSegment == "__DATA" && ParsedSection.startswith("__objc_"))) {
DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G << "\n");
return false;
}
// See http://code.google.com/p/address-sanitizer/issues/detail?id=32
// Constant CFString instances are compiled in the following way:
// -- the string buffer is emitted into
// __TEXT,__cstring,cstring_literals
// -- the constant NSConstantString structure referencing that buffer
// is placed into __DATA,__cfstring
// Therefore there's no point in placing redzones into __DATA,__cfstring.
// Moreover, it causes the linker to crash on OS X 10.7
if (ParsedSegment == "__DATA" && ParsedSection == "__cfstring") {
DEBUG(dbgs() << "Ignoring CFString: " << *G << "\n");
return false;
}
// The linker merges the contents of cstring_literals and removes the
// trailing zeroes.
if (ParsedSegment == "__TEXT" && (TAA & MachO::S_CSTRING_LITERALS)) {
DEBUG(dbgs() << "Ignoring a cstring literal: " << *G << "\n");
return false;
}
}
// Callbacks put into the CRT initializer/terminator sections
// should not be instrumented.
// See https://code.google.com/p/address-sanitizer/issues/detail?id=305
// and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx
if (Section.startswith(".CRT")) {
DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n");
return false;
}
// Globals from llvm.metadata aren't emitted, do not instrument them.
if (Section == "llvm.metadata") return false;
}
return true;
}
void AddressSanitizerModule::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
// Declare our poisoning and unpoisoning functions.
AsanPoisonGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
AsanPoisonGlobals->setLinkage(Function::ExternalLinkage);
AsanUnpoisonGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanUnpoisonGlobalsName, IRB.getVoidTy(), nullptr));
AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage);
// Declare functions that register/unregister globals.
AsanRegisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanRegisterGlobalsName, IRB.getVoidTy(),
IntptrTy, IntptrTy, nullptr));
AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
AsanUnregisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanUnregisterGlobalsName,
IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
}
// This function replaces all global variables with new variables that have
// trailing redzones. It also creates a function that poisons
// redzones and inserts this function into llvm.global_ctors.
bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
GlobalsMD.init(M);
SmallVector<GlobalVariable *, 16> GlobalsToChange;
for (auto &G : M.globals()) {
if (ShouldInstrumentGlobal(&G))
GlobalsToChange.push_back(&G);
}
size_t n = GlobalsToChange.size();
if (n == 0) return false;
// A global is described by a structure
// size_t beg;
// size_t size;
// size_t size_with_redzone;
// const char *name;
// const char *module_name;
// size_t has_dynamic_init;
// void *source_location;
// We initialize an array of such structures and pass it to a run-time call.
StructType *GlobalStructTy =
StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
IntptrTy, IntptrTy, nullptr);
SmallVector<Constant *, 16> Initializers(n);
bool HasDynamicallyInitializedGlobals = false;
// 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);
for (size_t i = 0; i < n; i++) {
static const uint64_t kMaxGlobalRedzone = 1 << 18;
GlobalVariable *G = GlobalsToChange[i];
auto MD = GlobalsMD.get(G);
// Create string holding the global name (use global name from metadata
// if it's available, otherwise just write the name of global variable).
GlobalVariable *Name = createPrivateGlobalForString(
M, MD.Name.empty() ? G->getName() : MD.Name,
/*AllowMerging*/ true);
PointerType *PtrTy = cast<PointerType>(G->getType());
Type *Ty = PtrTy->getElementType();
uint64_t SizeInBytes = DL->getTypeAllocSize(Ty);
uint64_t MinRZ = MinRedzoneSizeForGlobal();
// MinRZ <= RZ <= kMaxGlobalRedzone
// and trying to make RZ to be ~ 1/4 of SizeInBytes.
uint64_t RZ = std::max(MinRZ,
std::min(kMaxGlobalRedzone,
(SizeInBytes / MinRZ / 4) * MinRZ));
uint64_t RightRedzoneSize = RZ;
// Round up to MinRZ
if (SizeInBytes % MinRZ)
RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ);
assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0);
Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
StructType *NewTy = StructType::get(Ty, RightRedZoneTy, nullptr);
Constant *NewInitializer = ConstantStruct::get(
NewTy, G->getInitializer(),
Constant::getNullValue(RightRedZoneTy), nullptr);
// Create a new global variable with enough space for a redzone.
GlobalValue::LinkageTypes Linkage = G->getLinkage();
if (G->isConstant() && Linkage == GlobalValue::PrivateLinkage)
Linkage = GlobalValue::InternalLinkage;
GlobalVariable *NewGlobal = new GlobalVariable(
M, NewTy, G->isConstant(), Linkage,
NewInitializer, "", G, G->getThreadLocalMode());
NewGlobal->copyAttributesFrom(G);
NewGlobal->setAlignment(MinRZ);
Value *Indices2[2];
Indices2[0] = IRB.getInt32(0);
Indices2[1] = IRB.getInt32(0);
G->replaceAllUsesWith(
ConstantExpr::getGetElementPtr(NewGlobal, Indices2, true));
NewGlobal->takeName(G);
G->eraseFromParent();
Constant *SourceLoc;
if (!MD.SourceLoc.empty()) {
auto SourceLocGlobal = createPrivateGlobalForSourceLoc(M, MD.SourceLoc);
SourceLoc = ConstantExpr::getPointerCast(SourceLocGlobal, IntptrTy);
} else {
SourceLoc = ConstantInt::get(IntptrTy, 0);
}
Initializers[i] = ConstantStruct::get(
GlobalStructTy, ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
ConstantInt::get(IntptrTy, SizeInBytes),
ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
ConstantExpr::getPointerCast(Name, IntptrTy),
ConstantExpr::getPointerCast(ModuleName, IntptrTy),
ConstantInt::get(IntptrTy, MD.IsDynInit), SourceLoc, nullptr);
if (ClInitializers && MD.IsDynInit)
HasDynamicallyInitializedGlobals = true;
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), "");
// Create calls for poisoning before initializers run and unpoisoning after.
if (HasDynamicallyInitializedGlobals)
createInitializerPoisonCalls(M, ModuleName);
IRB.CreateCall2(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.CreateCall2(AsanUnregisterGlobals,
IRB.CreatePointerCast(AllGlobals, IntptrTy),
ConstantInt::get(IntptrTy, n));
appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
DEBUG(dbgs() << M);
return true;
}
bool AddressSanitizerModule::runOnModule(Module &M) {
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
if (!DLP)
return false;
DL = &DLP->getDataLayout();
C = &(M.getContext());
int LongSize = DL->getPointerSizeInBits();
IntptrTy = Type::getIntNTy(*C, LongSize);
TargetTriple = Triple(M.getTargetTriple());
Mapping = getShadowMapping(TargetTriple, LongSize);
initializeCallbacks(M);
bool Changed = false;
Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
assert(CtorFunc);
IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
if (ClGlobals)
Changed |= InstrumentGlobals(IRB, M);
return Changed;
}
void AddressSanitizer::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
// Create __asan_report* callbacks.
for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
AccessSizeIndex++) {
// IsWrite and TypeSize are encoded in the function name.
std::string Suffix =
(AccessIsWrite ? "store" : "load") + itostr(1 << AccessSizeIndex);
AsanErrorCallback[AccessIsWrite][AccessSizeIndex] =
checkInterfaceFunction(
M.getOrInsertFunction(kAsanReportErrorTemplate + Suffix,
IRB.getVoidTy(), IntptrTy, nullptr));
AsanMemoryAccessCallback[AccessIsWrite][AccessSizeIndex] =
checkInterfaceFunction(
M.getOrInsertFunction(ClMemoryAccessCallbackPrefix + Suffix,
IRB.getVoidTy(), IntptrTy, nullptr));
}
}
AsanErrorCallbackSized[0] = checkInterfaceFunction(M.getOrInsertFunction(
kAsanReportLoadN, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
AsanErrorCallbackSized[1] = checkInterfaceFunction(M.getOrInsertFunction(
kAsanReportStoreN, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
AsanMemoryAccessCallbackSized[0] = checkInterfaceFunction(
M.getOrInsertFunction(ClMemoryAccessCallbackPrefix + "loadN",
IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
AsanMemoryAccessCallbackSized[1] = checkInterfaceFunction(
M.getOrInsertFunction(ClMemoryAccessCallbackPrefix + "storeN",
IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
AsanMemmove = checkInterfaceFunction(M.getOrInsertFunction(
ClMemoryAccessCallbackPrefix + "memmove", IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
AsanMemcpy = checkInterfaceFunction(M.getOrInsertFunction(
ClMemoryAccessCallbackPrefix + "memcpy", IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
AsanMemset = checkInterfaceFunction(M.getOrInsertFunction(
ClMemoryAccessCallbackPrefix + "memset", IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IRB.getInt32Ty(), IntptrTy, nullptr));
AsanHandleNoReturnFunc = checkInterfaceFunction(
M.getOrInsertFunction(kAsanHandleNoReturnName, IRB.getVoidTy(), nullptr));
AsanPtrCmpFunction = checkInterfaceFunction(M.getOrInsertFunction(
kAsanPtrCmp, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
AsanPtrSubFunction = checkInterfaceFunction(M.getOrInsertFunction(
kAsanPtrSub, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
// We insert an empty inline asm after __asan_report* to avoid callback merge.
EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
StringRef(""), StringRef(""),
/*hasSideEffects=*/true);
}
// virtual
bool AddressSanitizer::doInitialization(Module &M) {
// Initialize the private fields. No one has accessed them before.
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
if (!DLP)
report_fatal_error("data layout missing");
DL = &DLP->getDataLayout();
GlobalsMD.init(M);
C = &(M.getContext());
LongSize = DL->getPointerSizeInBits();
IntptrTy = Type::getIntNTy(*C, LongSize);
TargetTriple = Triple(M.getTargetTriple());
AsanCtorFunction = Function::Create(
FunctionType::get(Type::getVoidTy(*C), false),
GlobalValue::InternalLinkage, kAsanModuleCtorName, &M);
BasicBlock *AsanCtorBB = BasicBlock::Create(*C, "", AsanCtorFunction);
// call __asan_init in the module ctor.
IRBuilder<> IRB(ReturnInst::Create(*C, AsanCtorBB));
AsanInitFunction = checkInterfaceFunction(
M.getOrInsertFunction(kAsanInitName, IRB.getVoidTy(), nullptr));
AsanInitFunction->setLinkage(Function::ExternalLinkage);
IRB.CreateCall(AsanInitFunction);
Mapping = getShadowMapping(TargetTriple, LongSize);
appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority);
return true;
}
bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
// For each NSObject descendant having a +load method, this method is invoked
// by the ObjC runtime before any of the static constructors is called.
// Therefore we need to instrument such methods with a call to __asan_init
// at the beginning in order to initialize our runtime before any access to
// the shadow memory.
// We cannot just ignore these methods, because they may call other
// instrumented functions.
if (F.getName().find(" load]") != std::string::npos) {
IRBuilder<> IRB(F.begin()->begin());
IRB.CreateCall(AsanInitFunction);
return true;
}
return false;
}
bool AddressSanitizer::runOnFunction(Function &F) {
if (&F == AsanCtorFunction) return false;
if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
initializeCallbacks(*F.getParent());
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
// If needed, insert __asan_init before checking for SanitizeAddress attr.
maybeInsertAsanInitAtFunctionEntry(F);
if (!F.hasFnAttribute(Attribute::SanitizeAddress))
return false;
if (!ClDebugFunc.empty() && ClDebugFunc != F.getName())
return false;
// We want to instrument every address only once per basic block (unless there
// are calls between uses).
SmallSet<Value*, 16> TempsToInstrument;
SmallVector<Instruction*, 16> ToInstrument;
SmallVector<Instruction*, 8> NoReturnCalls;
SmallVector<BasicBlock*, 16> AllBlocks;
SmallVector<Instruction*, 16> PointerComparisonsOrSubtracts;
int NumAllocas = 0;
bool IsWrite;
unsigned Alignment;
// Fill the set of memory operations to instrument.
for (auto &BB : F) {
AllBlocks.push_back(&BB);
TempsToInstrument.clear();
int NumInsnsPerBB = 0;
for (auto &Inst : BB) {
if (LooksLikeCodeInBug11395(&Inst)) return false;
if (Value *Addr =
isInterestingMemoryAccess(&Inst, &IsWrite, &Alignment)) {
if (ClOpt && ClOptSameTemp) {
if (!TempsToInstrument.insert(Addr).second)
continue; // We've seen this temp in the current BB.
}
} else if (ClInvalidPointerPairs &&
isInterestingPointerComparisonOrSubtraction(&Inst)) {
PointerComparisonsOrSubtracts.push_back(&Inst);
continue;
} else if (isa<MemIntrinsic>(Inst)) {
// ok, take it.
} else {
if (isa<AllocaInst>(Inst))
NumAllocas++;
CallSite CS(&Inst);
if (CS) {
// A call inside BB.
TempsToInstrument.clear();
if (CS.doesNotReturn())
NoReturnCalls.push_back(CS.getInstruction());
}
continue;
}
ToInstrument.push_back(&Inst);
NumInsnsPerBB++;
if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB)
break;
}
}
bool UseCalls = false;
if (ClInstrumentationWithCallsThreshold >= 0 &&
ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold)
UseCalls = true;
// Instrument.
int NumInstrumented = 0;
for (auto Inst : ToInstrument) {
if (ClDebugMin < 0 || ClDebugMax < 0 ||
(NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
if (isInterestingMemoryAccess(Inst, &IsWrite, &Alignment))
instrumentMop(Inst, UseCalls);
else
instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
}
NumInstrumented++;
}
FunctionStackPoisoner FSP(F, *this);
bool ChangedStack = FSP.runOnFunction();
// We must unpoison the stack before every NoReturn call (throw, _exit, etc).
// See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37
for (auto CI : NoReturnCalls) {
IRBuilder<> IRB(CI);
IRB.CreateCall(AsanHandleNoReturnFunc);
}
for (auto Inst : PointerComparisonsOrSubtracts) {
instrumentPointerComparisonOrSubtraction(Inst);
NumInstrumented++;
}
bool res = NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
DEBUG(dbgs() << "ASAN done instrumenting: " << res << " " << F << "\n");
return res;
}
// Workaround for bug 11395: we don't want to instrument stack in functions
// with large assembly blobs (32-bit only), otherwise reg alloc may crash.
// FIXME: remove once the bug 11395 is fixed.
bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) {
if (LongSize != 32) return false;
CallInst *CI = dyn_cast<CallInst>(I);
if (!CI || !CI->isInlineAsm()) return false;
if (CI->getNumArgOperands() <= 5) return false;
// We have inline assembly with quite a few arguments.
return true;
}
void FunctionStackPoisoner::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
for (int i = 0; i <= kMaxAsanStackMallocSizeClass; i++) {
std::string Suffix = itostr(i);
AsanStackMallocFunc[i] = checkInterfaceFunction(M.getOrInsertFunction(
kAsanStackMallocNameTemplate + Suffix, IntptrTy, IntptrTy, nullptr));
AsanStackFreeFunc[i] = checkInterfaceFunction(
M.getOrInsertFunction(kAsanStackFreeNameTemplate + Suffix,
IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
}
AsanPoisonStackMemoryFunc = checkInterfaceFunction(
M.getOrInsertFunction(kAsanPoisonStackMemoryName, IRB.getVoidTy(),
IntptrTy, IntptrTy, nullptr));
AsanUnpoisonStackMemoryFunc = checkInterfaceFunction(
M.getOrInsertFunction(kAsanUnpoisonStackMemoryName, IRB.getVoidTy(),
IntptrTy, IntptrTy, nullptr));
}
void
FunctionStackPoisoner::poisonRedZones(ArrayRef<uint8_t> ShadowBytes,
IRBuilder<> &IRB, Value *ShadowBase,
bool DoPoison) {
size_t n = ShadowBytes.size();
size_t i = 0;
// We need to (un)poison n bytes of stack shadow. Poison as many as we can
// using 64-bit stores (if we are on 64-bit arch), then poison the rest
// with 32-bit stores, then with 16-byte stores, then with 8-byte stores.
for (size_t LargeStoreSizeInBytes = ASan.LongSize / 8;
LargeStoreSizeInBytes != 0; LargeStoreSizeInBytes /= 2) {
for (; i + LargeStoreSizeInBytes - 1 < n; i += LargeStoreSizeInBytes) {
uint64_t Val = 0;
for (size_t j = 0; j < LargeStoreSizeInBytes; j++) {
if (ASan.DL->isLittleEndian())
Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
else
Val = (Val << 8) | ShadowBytes[i + j];
}
if (!Val) continue;
Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
Type *StoreTy = Type::getIntNTy(*C, LargeStoreSizeInBytes * 8);
Value *Poison = ConstantInt::get(StoreTy, DoPoison ? Val : 0);
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, StoreTy->getPointerTo()));
}
}
}
// Fake stack allocator (asan_fake_stack.h) has 11 size classes
// for every power of 2 from kMinStackMallocSize to kMaxAsanStackMallocSizeClass
static int StackMallocSizeClass(uint64_t LocalStackSize) {
assert(LocalStackSize <= kMaxStackMallocSize);
uint64_t MaxSize = kMinStackMallocSize;
for (int i = 0; ; i++, MaxSize *= 2)
if (LocalStackSize <= MaxSize)
return i;
llvm_unreachable("impossible LocalStackSize");
}
// Set Size bytes starting from ShadowBase to kAsanStackAfterReturnMagic.
// We can not use MemSet intrinsic because it may end up calling the actual
// memset. Size is a multiple of 8.
// Currently this generates 8-byte stores on x86_64; it may be better to
// generate wider stores.
void FunctionStackPoisoner::SetShadowToStackAfterReturnInlined(
IRBuilder<> &IRB, Value *ShadowBase, int Size) {
assert(!(Size % 8));
assert(kAsanStackAfterReturnMagic == 0xf5);
for (int i = 0; i < Size; i += 8) {
Value *p = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
IRB.CreateStore(ConstantInt::get(IRB.getInt64Ty(), 0xf5f5f5f5f5f5f5f5ULL),
IRB.CreateIntToPtr(p, IRB.getInt64Ty()->getPointerTo()));
}
}
static DebugLoc getFunctionEntryDebugLocation(Function &F) {
for (const auto &Inst : F.getEntryBlock())
if (!isa<AllocaInst>(Inst))
return Inst.getDebugLoc();
return DebugLoc();
}
PHINode *FunctionStackPoisoner::createPHI(IRBuilder<> &IRB, Value *Cond,
Value *ValueIfTrue,
Instruction *ThenTerm,
Value *ValueIfFalse) {
PHINode *PHI = IRB.CreatePHI(IntptrTy, 2);
BasicBlock *CondBlock = cast<Instruction>(Cond)->getParent();
PHI->addIncoming(ValueIfFalse, CondBlock);
BasicBlock *ThenBlock = ThenTerm->getParent();
PHI->addIncoming(ValueIfTrue, ThenBlock);
return PHI;
}
Value *FunctionStackPoisoner::createAllocaForLayout(
IRBuilder<> &IRB, const ASanStackFrameLayout &L, bool Dynamic) {
AllocaInst *Alloca;
if (Dynamic) {
Alloca = IRB.CreateAlloca(IRB.getInt8Ty(),
ConstantInt::get(IRB.getInt64Ty(), L.FrameSize),
"MyAlloca");
} else {
Alloca = IRB.CreateAlloca(ArrayType::get(IRB.getInt8Ty(), L.FrameSize),
nullptr, "MyAlloca");
assert(Alloca->isStaticAlloca());
}
assert((ClRealignStack & (ClRealignStack - 1)) == 0);
size_t FrameAlignment = std::max(L.FrameAlignment, (size_t)ClRealignStack);
Alloca->setAlignment(FrameAlignment);
return IRB.CreatePointerCast(Alloca, IntptrTy);
}
void FunctionStackPoisoner::poisonStack() {
assert(AllocaVec.size() > 0 || DynamicAllocaVec.size() > 0);
if (ClInstrumentAllocas)
// Handle dynamic allocas.
for (auto &AllocaCall : DynamicAllocaVec)
handleDynamicAllocaCall(AllocaCall);
if (AllocaVec.size() == 0) return;
int StackMallocIdx = -1;
DebugLoc EntryDebugLocation = getFunctionEntryDebugLocation(F);
Instruction *InsBefore = AllocaVec[0];
IRBuilder<> IRB(InsBefore);
IRB.SetCurrentDebugLocation(EntryDebugLocation);
SmallVector<ASanStackVariableDescription, 16> SVD;
SVD.reserve(AllocaVec.size());
for (AllocaInst *AI : AllocaVec) {
ASanStackVariableDescription D = { AI->getName().data(),
getAllocaSizeInBytes(AI),
AI->getAlignment(), AI, 0};
SVD.push_back(D);
}
// Minimal header size (left redzone) is 4 pointers,
// i.e. 32 bytes on 64-bit platforms and 16 bytes in 32-bit platforms.
size_t MinHeaderSize = ASan.LongSize / 2;
ASanStackFrameLayout L;
ComputeASanStackFrameLayout(SVD, 1UL << Mapping.Scale, MinHeaderSize, &L);
DEBUG(dbgs() << L.DescriptionString << " --- " << L.FrameSize << "\n");
uint64_t LocalStackSize = L.FrameSize;
bool DoStackMalloc =
ClUseAfterReturn && LocalStackSize <= kMaxStackMallocSize;
// Don't do dynamic alloca in presence of inline asm: too often it
// makes assumptions on which registers are available.
bool DoDynamicAlloca = ClDynamicAllocaStack && !HasNonEmptyInlineAsm;
Value *StaticAlloca =
DoDynamicAlloca ? nullptr : createAllocaForLayout(IRB, L, false);
Value *FakeStack;
Value *LocalStackBase;
if (DoStackMalloc) {
// void *FakeStack = __asan_option_detect_stack_use_after_return
// ? __asan_stack_malloc_N(LocalStackSize)
// : nullptr;
// void *LocalStackBase = (FakeStack) ? FakeStack : alloca(LocalStackSize);
Constant *OptionDetectUAR = F.getParent()->getOrInsertGlobal(
kAsanOptionDetectUAR, IRB.getInt32Ty());
Value *UARIsEnabled =
IRB.CreateICmpNE(IRB.CreateLoad(OptionDetectUAR),
Constant::getNullValue(IRB.getInt32Ty()));
Instruction *Term =
SplitBlockAndInsertIfThen(UARIsEnabled, InsBefore, false);
IRBuilder<> IRBIf(Term);
IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
StackMallocIdx = StackMallocSizeClass(LocalStackSize);
assert(StackMallocIdx <= kMaxAsanStackMallocSizeClass);
Value *FakeStackValue =
IRBIf.CreateCall(AsanStackMallocFunc[StackMallocIdx],
ConstantInt::get(IntptrTy, LocalStackSize));
IRB.SetInsertPoint(InsBefore);
IRB.SetCurrentDebugLocation(EntryDebugLocation);
FakeStack = createPHI(IRB, UARIsEnabled, FakeStackValue, Term,
ConstantInt::get(IntptrTy, 0));
Value *NoFakeStack =
IRB.CreateICmpEQ(FakeStack, Constant::getNullValue(IntptrTy));
Term = SplitBlockAndInsertIfThen(NoFakeStack, InsBefore, false);
IRBIf.SetInsertPoint(Term);
IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
Value *AllocaValue =
DoDynamicAlloca ? createAllocaForLayout(IRBIf, L, true) : StaticAlloca;
IRB.SetInsertPoint(InsBefore);
IRB.SetCurrentDebugLocation(EntryDebugLocation);
LocalStackBase = createPHI(IRB, NoFakeStack, AllocaValue, Term, FakeStack);
} else {
// void *FakeStack = nullptr;
// void *LocalStackBase = alloca(LocalStackSize);
FakeStack = ConstantInt::get(IntptrTy, 0);
LocalStackBase =
DoDynamicAlloca ? createAllocaForLayout(IRB, L, true) : StaticAlloca;
}
// Insert poison calls for lifetime intrinsics for alloca.
bool HavePoisonedAllocas = false;
for (const auto &APC : AllocaPoisonCallVec) {
assert(APC.InsBefore);
assert(APC.AI);
IRBuilder<> IRB(APC.InsBefore);
poisonAlloca(APC.AI, APC.Size, IRB, APC.DoPoison);
HavePoisonedAllocas |= APC.DoPoison;
}
// Replace Alloca instructions with base+offset.
for (const auto &Desc : SVD) {
AllocaInst *AI = Desc.AI;
Value *NewAllocaPtr = IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Desc.Offset)),
AI->getType());
replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB);
AI->replaceAllUsesWith(NewAllocaPtr);
}
// The left-most redzone has enough space for at least 4 pointers.
// Write the Magic value to redzone[0].
Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
BasePlus0);
// Write the frame description constant to redzone[1].
Value *BasePlus1 = IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, ASan.LongSize/8)),
IntptrPtrTy);
GlobalVariable *StackDescriptionGlobal =
createPrivateGlobalForString(*F.getParent(), L.DescriptionString,
/*AllowMerging*/true);
Value *Description = IRB.CreatePointerCast(StackDescriptionGlobal,
IntptrTy);
IRB.CreateStore(Description, BasePlus1);
// Write the PC to redzone[2].
Value *BasePlus2 = IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy,
2 * ASan.LongSize/8)),
IntptrPtrTy);
IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2);
// Poison the stack redzones at the entry.
Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
poisonRedZones(L.ShadowBytes, IRB, ShadowBase, true);
// (Un)poison the stack before all ret instructions.
for (auto Ret : RetVec) {
IRBuilder<> IRBRet(Ret);
// Mark the current frame as retired.
IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
BasePlus0);
if (DoStackMalloc) {
assert(StackMallocIdx >= 0);
// if FakeStack != 0 // LocalStackBase == FakeStack
// // In use-after-return mode, poison the whole stack frame.
// if StackMallocIdx <= 4
// // For small sizes inline the whole thing:
// memset(ShadowBase, kAsanStackAfterReturnMagic, ShadowSize);
// **SavedFlagPtr(FakeStack) = 0
// else
// __asan_stack_free_N(FakeStack, LocalStackSize)
// else
// <This is not a fake stack; unpoison the redzones>
Value *Cmp =
IRBRet.CreateICmpNE(FakeStack, Constant::getNullValue(IntptrTy));
TerminatorInst *ThenTerm, *ElseTerm;
SplitBlockAndInsertIfThenElse(Cmp, Ret, &ThenTerm, &ElseTerm);
IRBuilder<> IRBPoison(ThenTerm);
if (StackMallocIdx <= 4) {
int ClassSize = kMinStackMallocSize << StackMallocIdx;
SetShadowToStackAfterReturnInlined(IRBPoison, ShadowBase,
ClassSize >> Mapping.Scale);
Value *SavedFlagPtrPtr = IRBPoison.CreateAdd(
FakeStack,
ConstantInt::get(IntptrTy, ClassSize - ASan.LongSize / 8));
Value *SavedFlagPtr = IRBPoison.CreateLoad(
IRBPoison.CreateIntToPtr(SavedFlagPtrPtr, IntptrPtrTy));
IRBPoison.CreateStore(
Constant::getNullValue(IRBPoison.getInt8Ty()),
IRBPoison.CreateIntToPtr(SavedFlagPtr, IRBPoison.getInt8PtrTy()));
} else {
// For larger frames call __asan_stack_free_*.
IRBPoison.CreateCall2(AsanStackFreeFunc[StackMallocIdx], FakeStack,
ConstantInt::get(IntptrTy, LocalStackSize));
}
IRBuilder<> IRBElse(ElseTerm);
poisonRedZones(L.ShadowBytes, IRBElse, ShadowBase, false);
} else if (HavePoisonedAllocas) {
// If we poisoned some allocas in llvm.lifetime analysis,
// unpoison whole stack frame now.
poisonAlloca(LocalStackBase, LocalStackSize, IRBRet, false);
} else {
poisonRedZones(L.ShadowBytes, IRBRet, ShadowBase, false);
}
}
if (ClInstrumentAllocas)
// Unpoison dynamic allocas.
for (auto &AllocaCall : DynamicAllocaVec)
unpoisonDynamicAlloca(AllocaCall);
// We are done. Remove the old unused alloca instructions.
for (auto AI : AllocaVec)
AI->eraseFromParent();
}
void FunctionStackPoisoner::poisonAlloca(Value *V, uint64_t Size,
IRBuilder<> &IRB, bool DoPoison) {
// For now just insert the call to ASan runtime.
Value *AddrArg = IRB.CreatePointerCast(V, IntptrTy);
Value *SizeArg = ConstantInt::get(IntptrTy, Size);
IRB.CreateCall2(DoPoison ? AsanPoisonStackMemoryFunc
: AsanUnpoisonStackMemoryFunc,
AddrArg, SizeArg);
}
// Handling llvm.lifetime intrinsics for a given %alloca:
// (1) collect all llvm.lifetime.xxx(%size, %value) describing the alloca.
// (2) if %size is constant, poison memory for llvm.lifetime.end (to detect
// invalid accesses) and unpoison it for llvm.lifetime.start (the memory
// could be poisoned by previous llvm.lifetime.end instruction, as the
// variable may go in and out of scope several times, e.g. in loops).
// (3) if we poisoned at least one %alloca in a function,
// unpoison the whole stack frame at function exit.
AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) {
if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
// We're intested only in allocas we can handle.
return isInterestingAlloca(*AI) ? AI : nullptr;
// See if we've already calculated (or started to calculate) alloca for a
// given value.
AllocaForValueMapTy::iterator I = AllocaForValue.find(V);
if (I != AllocaForValue.end())
return I->second;
// Store 0 while we're calculating alloca for value V to avoid
// infinite recursion if the value references itself.
AllocaForValue[V] = nullptr;
AllocaInst *Res = nullptr;
if (CastInst *CI = dyn_cast<CastInst>(V))
Res = findAllocaForValue(CI->getOperand(0));
else if (PHINode *PN = dyn_cast<PHINode>(V)) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *IncValue = PN->getIncomingValue(i);
// Allow self-referencing phi-nodes.
if (IncValue == PN) continue;
AllocaInst *IncValueAI = findAllocaForValue(IncValue);
// AI for incoming values should exist and should all be equal.
if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res))
return nullptr;
Res = IncValueAI;
}
}
if (Res)
AllocaForValue[V] = Res;
return Res;
}
// Compute PartialRzMagic for dynamic alloca call. PartialRzMagic is
// constructed from two separate 32-bit numbers: PartialRzMagic = Val1 | Val2.
// (1) Val1 is resposible for forming base value for PartialRzMagic, containing
// only 00 for fully addressable and 0xcb for fully poisoned bytes for each
// 8-byte chunk of user memory respectively.
// (2) Val2 forms the value for marking first poisoned byte in shadow memory
// with appropriate value (0x01 - 0x07 or 0xcb if Padding % 8 == 0).
// Shift = Padding & ~7; // the number of bits we need to shift to access first
// chunk in shadow memory, containing nonzero bytes.
// Example:
// Padding = 21 Padding = 16
// Shadow: |00|00|05|cb| Shadow: |00|00|cb|cb|
// ^ ^
// | |
// Shift = 21 & ~7 = 16 Shift = 16 & ~7 = 16
//
// Val1 = 0xcbcbcbcb << Shift;
// PartialBits = Padding ? Padding & 7 : 0xcb;
// Val2 = PartialBits << Shift;
// Result = Val1 | Val2;
Value *FunctionStackPoisoner::computePartialRzMagic(Value *PartialSize,
IRBuilder<> &IRB) {
PartialSize = IRB.CreateIntCast(PartialSize, IRB.getInt32Ty(), false);
Value *Shift = IRB.CreateAnd(PartialSize, IRB.getInt32(~7));
unsigned Val1Int = kAsanAllocaPartialVal1;
unsigned Val2Int = kAsanAllocaPartialVal2;
if (!ASan.DL->isLittleEndian()) {
Val1Int = sys::getSwappedBytes(Val1Int);
Val2Int = sys::getSwappedBytes(Val2Int);
}
Value *Val1 = shiftAllocaMagic(IRB.getInt32(Val1Int), IRB, Shift);
Value *PartialBits = IRB.CreateAnd(PartialSize, IRB.getInt32(7));
// For BigEndian get 0x000000YZ -> 0xYZ000000.
if (ASan.DL->isBigEndian())
PartialBits = IRB.CreateShl(PartialBits, IRB.getInt32(24));
Value *Val2 = IRB.getInt32(Val2Int);
Value *Cond =
IRB.CreateICmpNE(PartialBits, Constant::getNullValue(IRB.getInt32Ty()));
Val2 = IRB.CreateSelect(Cond, shiftAllocaMagic(PartialBits, IRB, Shift),
shiftAllocaMagic(Val2, IRB, Shift));
return IRB.CreateOr(Val1, Val2);
}
void FunctionStackPoisoner::handleDynamicAllocaCall(
DynamicAllocaCall &AllocaCall) {
AllocaInst *AI = AllocaCall.AI;
if (!doesDominateAllExits(AI)) {
// We do not yet handle complex allocas
AllocaCall.Poison = false;
return;
}
IRBuilder<> IRB(AI);
PointerType *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
const unsigned Align = std::max(kAllocaRzSize, AI->getAlignment());
const uint64_t AllocaRedzoneMask = kAllocaRzSize - 1;
Value *Zero = Constant::getNullValue(IntptrTy);
Value *AllocaRzSize = ConstantInt::get(IntptrTy, kAllocaRzSize);
Value *AllocaRzMask = ConstantInt::get(IntptrTy, AllocaRedzoneMask);
Value *NotAllocaRzMask = ConstantInt::get(IntptrTy, ~AllocaRedzoneMask);
// Since we need to extend alloca with additional memory to locate
// redzones, and OldSize is number of allocated blocks with
// ElementSize size, get allocated memory size in bytes by
// OldSize * ElementSize.
unsigned ElementSize = ASan.DL->getTypeAllocSize(AI->getAllocatedType());
Value *OldSize = IRB.CreateMul(AI->getArraySize(),
ConstantInt::get(IntptrTy, ElementSize));
// PartialSize = OldSize % 32
Value *PartialSize = IRB.CreateAnd(OldSize, AllocaRzMask);
// Misalign = kAllocaRzSize - PartialSize;
Value *Misalign = IRB.CreateSub(AllocaRzSize, PartialSize);
// PartialPadding = Misalign != kAllocaRzSize ? Misalign : 0;
Value *Cond = IRB.CreateICmpNE(Misalign, AllocaRzSize);
Value *PartialPadding = IRB.CreateSelect(Cond, Misalign, Zero);
// AdditionalChunkSize = Align + PartialPadding + kAllocaRzSize
// Align is added to locate left redzone, PartialPadding for possible
// partial redzone and kAllocaRzSize for right redzone respectively.
Value *AdditionalChunkSize = IRB.CreateAdd(
ConstantInt::get(IntptrTy, Align + kAllocaRzSize), PartialPadding);
Value *NewSize = IRB.CreateAdd(OldSize, AdditionalChunkSize);
// Insert new alloca with new NewSize and Align params.
AllocaInst *NewAlloca = IRB.CreateAlloca(IRB.getInt8Ty(), NewSize);
NewAlloca->setAlignment(Align);
// NewAddress = Address + Align
Value *NewAddress = IRB.CreateAdd(IRB.CreatePtrToInt(NewAlloca, IntptrTy),
ConstantInt::get(IntptrTy, Align));
Value *NewAddressPtr = IRB.CreateIntToPtr(NewAddress, AI->getType());
// LeftRzAddress = NewAddress - kAllocaRzSize
Value *LeftRzAddress = IRB.CreateSub(NewAddress, AllocaRzSize);
// Poisoning left redzone.
AllocaCall.LeftRzAddr = ASan.memToShadow(LeftRzAddress, IRB);
IRB.CreateStore(ConstantInt::get(IRB.getInt32Ty(), kAsanAllocaLeftMagic),
IRB.CreateIntToPtr(AllocaCall.LeftRzAddr, Int32PtrTy));
// PartialRzAligned = PartialRzAddr & ~AllocaRzMask
Value *PartialRzAddr = IRB.CreateAdd(NewAddress, OldSize);
Value *PartialRzAligned = IRB.CreateAnd(PartialRzAddr, NotAllocaRzMask);
// Poisoning partial redzone.
Value *PartialRzMagic = computePartialRzMagic(PartialSize, IRB);
Value *PartialRzShadowAddr = ASan.memToShadow(PartialRzAligned, IRB);
IRB.CreateStore(PartialRzMagic,
IRB.CreateIntToPtr(PartialRzShadowAddr, Int32PtrTy));
// RightRzAddress
// = (PartialRzAddr + AllocaRzMask) & ~AllocaRzMask
Value *RightRzAddress = IRB.CreateAnd(
IRB.CreateAdd(PartialRzAddr, AllocaRzMask), NotAllocaRzMask);
// Poisoning right redzone.
AllocaCall.RightRzAddr = ASan.memToShadow(RightRzAddress, IRB);
IRB.CreateStore(ConstantInt::get(IRB.getInt32Ty(), kAsanAllocaRightMagic),
IRB.CreateIntToPtr(AllocaCall.RightRzAddr, Int32PtrTy));
// Replace all uses of AddessReturnedByAlloca with NewAddress.
AI->replaceAllUsesWith(NewAddressPtr);
// We are done. Erase old alloca and store left, partial and right redzones
// shadow addresses for future unpoisoning.
AI->eraseFromParent();
NumInstrumentedDynamicAllocas++;
}
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