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[safestack] Use non-thread-local unsafe stack pointer for Contiki OS

Patch by Michael LeMay

Differential revision: http://reviews.llvm.org/D19852

llvm-svn: 284254
This commit is contained in:
David L Kreitzer 2016-10-14 17:56:00 +00:00
parent 259a7b3aba
commit d68b19752a
5 changed files with 44 additions and 54 deletions

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@ -1114,8 +1114,12 @@ public:
/// Should be used only when getIRStackGuard returns nullptr.
virtual Value *getSSPStackGuardCheck(const Module &M) const;
/// If the target has a standard location for the unsafe stack pointer,
/// returns the address of that location. Otherwise, returns nullptr.
protected:
Value *getDefaultSafeStackPointerLocation(IRBuilder<> &IRB,
bool UseTLS) const;
public:
/// Returns the target-specific address of the unsafe stack pointer.
virtual Value *getSafeStackPointerLocation(IRBuilder<> &IRB) const;
/// Returns true if a cast between SrcAS and DestAS is a noop.

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@ -52,16 +52,6 @@ using namespace llvm::safestack;
#define DEBUG_TYPE "safestack"
enum UnsafeStackPtrStorageVal { ThreadLocalUSP, SingleThreadUSP };
static cl::opt<UnsafeStackPtrStorageVal> USPStorage("safe-stack-usp-storage",
cl::Hidden, cl::init(ThreadLocalUSP),
cl::desc("Type of storage for the unsafe stack pointer"),
cl::values(clEnumValN(ThreadLocalUSP, "thread-local",
"Thread-local storage"),
clEnumValN(SingleThreadUSP, "single-thread",
"Non-thread-local storage")));
namespace llvm {
STATISTIC(NumFunctions, "Total number of functions");
@ -123,9 +113,6 @@ class SafeStack : public FunctionPass {
/// might expect to appear on the stack on most common targets.
enum { StackAlignment = 16 };
/// \brief Build a value representing a pointer to the unsafe stack pointer.
Value *getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F);
/// \brief Return the value of the stack canary.
Value *getStackGuard(IRBuilder<> &IRB, Function &F);
@ -355,41 +342,6 @@ bool SafeStack::IsSafeStackAlloca(const Value *AllocaPtr, uint64_t AllocaSize) {
return true;
}
Value *SafeStack::getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F) {
// Check if there is a target-specific location for the unsafe stack pointer.
if (Value *V = TL->getSafeStackPointerLocation(IRB))
return V;
// Otherwise, assume the target links with compiler-rt, which provides a
// thread-local variable with a magic name.
Module &M = *F.getParent();
const char *UnsafeStackPtrVar = "__safestack_unsafe_stack_ptr";
auto UnsafeStackPtr =
dyn_cast_or_null<GlobalVariable>(M.getNamedValue(UnsafeStackPtrVar));
bool UseTLS = USPStorage == ThreadLocalUSP;
if (!UnsafeStackPtr) {
auto TLSModel = UseTLS ?
GlobalValue::InitialExecTLSModel :
GlobalValue::NotThreadLocal;
// The global variable is not defined yet, define it ourselves.
// We use the initial-exec TLS model because we do not support the
// variable living anywhere other than in the main executable.
UnsafeStackPtr = new GlobalVariable(
M, StackPtrTy, false, GlobalValue::ExternalLinkage, nullptr,
UnsafeStackPtrVar, nullptr, TLSModel);
} else {
// The variable exists, check its type and attributes.
if (UnsafeStackPtr->getValueType() != StackPtrTy)
report_fatal_error(Twine(UnsafeStackPtrVar) + " must have void* type");
if (UseTLS != UnsafeStackPtr->isThreadLocal())
report_fatal_error(Twine(UnsafeStackPtrVar) + " must " +
(UseTLS ? "" : "not ") + "be thread-local");
}
return UnsafeStackPtr;
}
Value *SafeStack::getStackGuard(IRBuilder<> &IRB, Function &F) {
Value *StackGuardVar = TL->getIRStackGuard(IRB);
if (!StackGuardVar)
@ -784,7 +736,7 @@ bool SafeStack::runOnFunction(Function &F) {
++NumUnsafeStackRestorePointsFunctions;
IRBuilder<> IRB(&F.front(), F.begin()->getFirstInsertionPt());
UnsafeStackPtr = getOrCreateUnsafeStackPtr(IRB, F);
UnsafeStackPtr = TL->getSafeStackPointerLocation(IRB);
// Load the current stack pointer (we'll also use it as a base pointer).
// FIXME: use a dedicated register for it ?

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@ -1767,9 +1767,41 @@ TargetLoweringBase::getTypeLegalizationCost(const DataLayout &DL,
}
}
Value *TargetLoweringBase::getDefaultSafeStackPointerLocation(IRBuilder<> &IRB,
bool UseTLS) const {
// compiler-rt provides a variable with a magic name. Targets that do not
// link with compiler-rt may also provide such a variable.
Module *M = IRB.GetInsertBlock()->getParent()->getParent();
const char *UnsafeStackPtrVar = "__safestack_unsafe_stack_ptr";
auto UnsafeStackPtr =
dyn_cast_or_null<GlobalVariable>(M->getNamedValue(UnsafeStackPtrVar));
Type *StackPtrTy = Type::getInt8PtrTy(M->getContext());
if (!UnsafeStackPtr) {
auto TLSModel = UseTLS ?
GlobalValue::InitialExecTLSModel :
GlobalValue::NotThreadLocal;
// The global variable is not defined yet, define it ourselves.
// We use the initial-exec TLS model because we do not support the
// variable living anywhere other than in the main executable.
UnsafeStackPtr = new GlobalVariable(
*M, StackPtrTy, false, GlobalValue::ExternalLinkage, nullptr,
UnsafeStackPtrVar, nullptr, TLSModel);
} else {
// The variable exists, check its type and attributes.
if (UnsafeStackPtr->getValueType() != StackPtrTy)
report_fatal_error(Twine(UnsafeStackPtrVar) + " must have void* type");
if (UseTLS != UnsafeStackPtr->isThreadLocal())
report_fatal_error(Twine(UnsafeStackPtrVar) + " must " +
(UseTLS ? "" : "not ") + "be thread-local");
}
return UnsafeStackPtr;
}
Value *TargetLoweringBase::getSafeStackPointerLocation(IRBuilder<> &IRB) const {
if (!TM.getTargetTriple().isAndroid())
return nullptr;
return getDefaultSafeStackPointerLocation(IRB, true);
// Android provides a libc function to retrieve the address of the current
// thread's unsafe stack pointer.

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@ -2045,6 +2045,9 @@ Value *X86TargetLowering::getSSPStackGuardCheck(const Module &M) const {
}
Value *X86TargetLowering::getSafeStackPointerLocation(IRBuilder<> &IRB) const {
if (Subtarget.getTargetTriple().isOSContiki())
return getDefaultSafeStackPointerLocation(IRB, false);
if (!Subtarget.isTargetAndroid())
return TargetLowering::getSafeStackPointerLocation(IRB);

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@ -1,7 +1,6 @@
; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck %s
; RUN: opt -safe-stack -safe-stack-usp-storage=single-thread -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck -check-prefix=SINGLE-THREAD %s
; RUN: opt -safe-stack -S -mtriple=i386-pc-contiki-unknown < %s -o - | FileCheck -check-prefix=SINGLE-THREAD %s
; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck %s
; RUN: opt -safe-stack -safe-stack-usp-storage=single-thread -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck -check-prefix=SINGLE-THREAD %s
; array [4 x i8]
; Requires protector.