mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-23 19:23:23 +01:00
222 lines
7.6 KiB
C++
222 lines
7.6 KiB
C++
//===-- StackProtector.cpp - Stack Protector Insertion --------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This pass inserts stack protectors into functions which need them. A variable
|
|
// with a random value in it is stored onto the stack before the local variables
|
|
// are allocated. Upon exiting the block, the stored value is checked. If it's
|
|
// changed, then there was some sort of violation and the program aborts.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "stack-protector"
|
|
#include "llvm/CodeGen/Passes.h"
|
|
#include "llvm/Attributes.h"
|
|
#include "llvm/Constants.h"
|
|
#include "llvm/DerivedTypes.h"
|
|
#include "llvm/Function.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/Intrinsics.h"
|
|
#include "llvm/Module.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Support/CommandLine.h"
|
|
#include "llvm/Target/TargetData.h"
|
|
#include "llvm/Target/TargetLowering.h"
|
|
using namespace llvm;
|
|
|
|
// SSPBufferSize - The lower bound for a buffer to be considered for stack
|
|
// smashing protection.
|
|
static cl::opt<unsigned>
|
|
SSPBufferSize("stack-protector-buffer-size", cl::init(8),
|
|
cl::desc("Lower bound for a buffer to be considered for "
|
|
"stack protection"));
|
|
|
|
namespace {
|
|
class VISIBILITY_HIDDEN StackProtector : public FunctionPass {
|
|
/// TLI - Keep a pointer of a TargetLowering to consult for determining
|
|
/// target type sizes.
|
|
const TargetLowering *TLI;
|
|
|
|
Function *F;
|
|
Module *M;
|
|
|
|
/// InsertStackProtectors - Insert code into the prologue and epilogue of
|
|
/// the function.
|
|
///
|
|
/// - The prologue code loads and stores the stack guard onto the stack.
|
|
/// - The epilogue checks the value stored in the prologue against the
|
|
/// original value. It calls __stack_chk_fail if they differ.
|
|
bool InsertStackProtectors();
|
|
|
|
/// CreateFailBB - Create a basic block to jump to when the stack protector
|
|
/// check fails.
|
|
BasicBlock *CreateFailBB();
|
|
|
|
/// RequiresStackProtector - Check whether or not this function needs a
|
|
/// stack protector based upon the stack protector level.
|
|
bool RequiresStackProtector() const;
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid.
|
|
StackProtector() : FunctionPass(&ID), TLI(0) {}
|
|
StackProtector(const TargetLowering *tli)
|
|
: FunctionPass(&ID), TLI(tli) {}
|
|
|
|
virtual bool runOnFunction(Function &Fn);
|
|
};
|
|
} // end anonymous namespace
|
|
|
|
char StackProtector::ID = 0;
|
|
static RegisterPass<StackProtector>
|
|
X("stack-protector", "Insert stack protectors");
|
|
|
|
FunctionPass *llvm::createStackProtectorPass(const TargetLowering *tli) {
|
|
return new StackProtector(tli);
|
|
}
|
|
|
|
bool StackProtector::runOnFunction(Function &Fn) {
|
|
F = &Fn;
|
|
M = F->getParent();
|
|
|
|
if (!RequiresStackProtector()) return false;
|
|
|
|
return InsertStackProtectors();
|
|
}
|
|
|
|
/// RequiresStackProtector - Check whether or not this function needs a stack
|
|
/// protector based upon the stack protector level. The heuristic we use is to
|
|
/// add a guard variable to functions that call alloca, and functions with
|
|
/// buffers larger than SSPBufferSize bytes.
|
|
bool StackProtector::RequiresStackProtector() const {
|
|
if (F->hasFnAttr(Attribute::StackProtectReq))
|
|
return true;
|
|
|
|
if (!F->hasFnAttr(Attribute::StackProtect))
|
|
return false;
|
|
|
|
const TargetData *TD = TLI->getTargetData();
|
|
|
|
for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
|
|
BasicBlock *BB = I;
|
|
|
|
for (BasicBlock::iterator
|
|
II = BB->begin(), IE = BB->end(); II != IE; ++II)
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
|
|
if (AI->isArrayAllocation())
|
|
// This is a call to alloca with a variable size. Emit stack
|
|
// protectors.
|
|
return true;
|
|
|
|
if (const ArrayType *AT = dyn_cast<ArrayType>(AI->getAllocatedType()))
|
|
// If an array has more than SSPBufferSize bytes of allocated space,
|
|
// then we emit stack protectors.
|
|
if (SSPBufferSize <= TD->getABITypeSize(AT))
|
|
return true;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// InsertStackProtectors - Insert code into the prologue and epilogue of the
|
|
/// function.
|
|
///
|
|
/// - The prologue code loads and stores the stack guard onto the stack.
|
|
/// - The epilogue checks the value stored in the prologue against the original
|
|
/// value. It calls __stack_chk_fail if they differ.
|
|
bool StackProtector::InsertStackProtectors() {
|
|
BasicBlock *FailBB = 0; // The basic block to jump to if check fails.
|
|
AllocaInst *AI = 0; // Place on stack that stores the stack guard.
|
|
Constant *StackGuardVar = 0; // The stack guard variable.
|
|
|
|
for (Function::iterator I = F->begin(), E = F->end(); I != E; ) {
|
|
BasicBlock *BB = I++;
|
|
|
|
ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
|
|
if (!RI) continue;
|
|
|
|
if (!FailBB) {
|
|
// Insert code into the entry block that stores the __stack_chk_guard
|
|
// variable onto the stack:
|
|
//
|
|
// entry:
|
|
// StackGuardSlot = alloca i8*
|
|
// StackGuard = load __stack_chk_guard
|
|
// call void @llvm.stackprotect.create(StackGuard, StackGuardSlot)
|
|
//
|
|
PointerType *PtrTy = PointerType::getUnqual(Type::Int8Ty);
|
|
StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", PtrTy);
|
|
|
|
BasicBlock &Entry = F->getEntryBlock();
|
|
Instruction *InsPt = &Entry.front();
|
|
|
|
AI = new AllocaInst(PtrTy, "StackGuardSlot", InsPt);
|
|
LoadInst *LI = new LoadInst(StackGuardVar, "StackGuard", false, InsPt);
|
|
|
|
Value *Args[] = { LI, AI };
|
|
CallInst::
|
|
Create(Intrinsic::getDeclaration(M, Intrinsic::stackprotector),
|
|
&Args[0], array_endof(Args), "", InsPt);
|
|
|
|
// Create the basic block to jump to when the guard check fails.
|
|
FailBB = CreateFailBB();
|
|
}
|
|
|
|
// For each block with a return instruction, convert this:
|
|
//
|
|
// return:
|
|
// ...
|
|
// ret ...
|
|
//
|
|
// into this:
|
|
//
|
|
// return:
|
|
// ...
|
|
// %1 = load __stack_chk_guard
|
|
// %2 = load StackGuardSlot
|
|
// %3 = cmp i1 %1, %2
|
|
// br i1 %3, label %SP_return, label %CallStackCheckFailBlk
|
|
//
|
|
// SP_return:
|
|
// ret ...
|
|
//
|
|
// CallStackCheckFailBlk:
|
|
// call void @__stack_chk_fail()
|
|
// unreachable
|
|
|
|
// Split the basic block before the return instruction.
|
|
BasicBlock *NewBB = BB->splitBasicBlock(RI, "SP_return");
|
|
|
|
// Move the newly created basic block to the point right after the old basic
|
|
// block so that it's in the "fall through" position.
|
|
NewBB->moveAfter(BB);
|
|
|
|
// Generate the stack protector instructions in the old basic block.
|
|
LoadInst *LI1 = new LoadInst(StackGuardVar, "", false, BB);
|
|
LoadInst *LI2 = new LoadInst(AI, "", true, BB);
|
|
ICmpInst *Cmp = new ICmpInst(CmpInst::ICMP_EQ, LI1, LI2, "", BB);
|
|
BranchInst::Create(NewBB, FailBB, Cmp, BB);
|
|
}
|
|
|
|
// Return if we didn't modify any basic blocks. I.e., there are no return
|
|
// statements in the function.
|
|
if (!FailBB) return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/// CreateFailBB - Create a basic block to jump to when the stack protector
|
|
/// check fails.
|
|
BasicBlock *StackProtector::CreateFailBB() {
|
|
BasicBlock *FailBB = BasicBlock::Create("CallStackCheckFailBlk", F);
|
|
Constant *StackChkFail =
|
|
M->getOrInsertFunction("__stack_chk_fail", Type::VoidTy, NULL);
|
|
CallInst::Create(StackChkFail, "", FailBB);
|
|
new UnreachableInst(FailBB);
|
|
return FailBB;
|
|
}
|