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[stackprotector] Added support for emitting the llvm intrinsic stack protector check.

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rdar://13935163

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188766 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Gottesman 2013-08-20 08:36:53 +00:00
parent 9d6852cf98
commit 3480d1b84e
1 changed files with 151 additions and 50 deletions
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201
lib/CodeGen/StackProtector.cpp
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@ -15,11 +15,13 @@
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "stack-protector"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
@ -28,6 +30,7 @@
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
@ -40,6 +43,10 @@ STATISTIC(NumFunProtected, "Number of functions protected");
STATISTIC(NumAddrTaken, "Number of local variables that have their address"
" taken.");
static cl::opt<bool>
EnableSelectionDAGSP("enable-selectiondag-sp", cl::init(true),
cl::Hidden);
namespace {
class StackProtector : public FunctionPass {
const TargetMachine *TM;
@ -265,6 +272,62 @@ bool StackProtector::RequiresStackProtector() {
return false;
}
static bool InstructionWillNotHaveChain(const Instruction *I) {
return !I->mayHaveSideEffects() && !I->mayReadFromMemory() &&
isSafeToSpeculativelyExecute(I);
}
/// Identify if RI has a previous instruction in the "Tail Position" and return
/// it. Otherwise return 0.
///
/// This is based off of the code in llvm::isInTailCallPosition
static CallInst *FindPotentialTailCall(BasicBlock *BB, ReturnInst *RI,
const TargetLoweringBase *TLI) {
// Establish a reasonable upper bound on the maximum amount of instructions we
// will look through to find a tail call.
unsigned SearchCounter = 0;
const unsigned MaxSearch = 4;
bool NoInterposingChain = true;
for (BasicBlock::reverse_iterator I = llvm::next(BB->rbegin()), E = BB->rend();
I != E && SearchCounter < MaxSearch; ++I) {
Instruction *Inst = &*I;
// Skip over debug intrinsics and do not allow them to affect our MaxSearch
// counter.
if (isa<DbgInfoIntrinsic>(Inst))
continue;
// If we find a call and the following conditions are satisifed, then we
// have found a tail call that satisfies at least the target independent
// requirements of a tail call:
//
// 1. The call site has the tail marker.
//
// 2. The call site either will not cause the creation of a chain or if a
// chain is necessary there are no instructions in between the callsite and
// the call which would create an interposing chain.
//
// 3. The return type of the function does not impede tail call
// optimization.
if (CallInst *CI = dyn_cast<CallInst>(Inst)) {
if (CI->isTailCall() &&
(InstructionWillNotHaveChain(CI) || NoInterposingChain) &&
returnTypeIsEligibleForTailCall(BB->getParent(), CI, RI, *TLI))
return CI;
}
// If we did not find a call see if we have an instruction that may create
// an interposing chain.
NoInterposingChain = NoInterposingChain && InstructionWillNotHaveChain(Inst);
// Increment max search.
SearchCounter++;
}
return 0;
}
/// Insert code into the entry block that stores the __stack_chk_guard
/// variable onto the stack:
///
@ -273,9 +336,12 @@ bool StackProtector::RequiresStackProtector() {
/// StackGuard = load __stack_chk_guard
/// call void @llvm.stackprotect.create(StackGuard, StackGuardSlot)
///
static void CreatePrologue(Function *F, Module *M, ReturnInst *RI,
/// Returns true if the platform/triple supports the stackprotectorcreate pseudo
/// node.
static bool CreatePrologue(Function *F, Module *M, ReturnInst *RI,
const TargetLoweringBase *TLI, const Triple &Trip,
AllocaInst *&AI, Value *&StackGuardVar) {
bool SupportsSelectionDAGSP = false;
PointerType *PtrTy = Type::getInt8PtrTy(RI->getContext());
unsigned AddressSpace, Offset;
if (TLI->getStackCookieLocation(AddressSpace, Offset)) {
@ -290,7 +356,8 @@ static void CreatePrologue(Function *F, Module *M, ReturnInst *RI,
cast<GlobalValue>(StackGuardVar)
->setVisibility(GlobalValue::HiddenVisibility);
} else {
StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", PtrTy);
SupportsSelectionDAGSP = true;
StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", PtrTy);
}
BasicBlock &Entry = F->getEntryBlock();
@ -303,6 +370,8 @@ static void CreatePrologue(Function *F, Module *M, ReturnInst *RI,
CallInst::
Create(Intrinsic::getDeclaration(M, Intrinsic::stackprotector),
Args, "", InsPt);
return SupportsSelectionDAGSP;
}
/// InsertStackProtectors - Insert code into the prologue and epilogue of the
@ -313,6 +382,7 @@ static void CreatePrologue(Function *F, Module *M, ReturnInst *RI,
/// value. It calls __stack_chk_fail if they differ.
bool StackProtector::InsertStackProtectors() {
bool HasPrologue = false;
bool SupportsSelectionDAGSP = false;
AllocaInst *AI = 0; // Place on stack that stores the stack guard.
Value *StackGuardVar = 0; // The stack guard variable.
@ -323,55 +393,86 @@ bool StackProtector::InsertStackProtectors() {
if (!HasPrologue) {
HasPrologue = true;
CreatePrologue(F, M, RI, TLI, Trip, AI, StackGuardVar);
SupportsSelectionDAGSP = CreatePrologue(F, M, RI, TLI, Trip, AI,
StackGuardVar);
}
// TODO: Put in check here if platform supports the stack protector check
// intrinsic.
if (EnableSelectionDAGSP && !TM->Options.EnableFastISel &&
SupportsSelectionDAGSP) {
// Since we have a potential tail call, insert the special stack check
// intrinsic.
Instruction *InsertionPt = 0;
if (CallInst *CI = FindPotentialTailCall(BB, RI, TLI)) {
InsertionPt = CI;
} else {
InsertionPt = RI;
// At this point we know that BB has a return statement so it *DOES*
// have a terminator.
assert(InsertionPt != 0 && "BB must have a terminator instruction at "
"this point.");
}
Function *Intrinsic =
Intrinsic::getDeclaration(M, Intrinsic::stackprotectorcheck);
Value *Args[] = { StackGuardVar };
CallInst::Create(Intrinsic, Args, "", InsertionPt);
} else {
// If we do not have a potential tail call or our platform does not
// support lowering the stack protector check pseudo node, perform the IR
// level stack check.
// 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
// Create the FailBB. We duplicate the BB every time since the MI tail
// merge pass will merge together all of the various BB into one including
// fail BB generated by the stack protector pseudo instruction.
BasicBlock *FailBB = CreateFailBB();
// Split the basic block before the return instruction.
BasicBlock *NewBB = BB->splitBasicBlock(RI, "SP_return");
// Update the dominator tree if we need to.
if (DT && DT->isReachableFromEntry(BB)) {
DT->addNewBlock(NewBB, BB);
DT->addNewBlock(FailBB, BB);
}
// Remove default branch instruction to the new BB.
BB->getTerminator()->eraseFromParent();
// 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(*BB, CmpInst::ICMP_EQ, LI1, LI2, "");
BranchInst::Create(NewBB, FailBB, Cmp, BB);
}
// 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
// Create the fail basic block.
BasicBlock *FailBB = CreateFailBB();
// Split the basic block before the return instruction.
BasicBlock *NewBB = BB->splitBasicBlock(RI, "SP_return");
// Update the dominator tree if we need to.
if (DT && DT->isReachableFromEntry(BB)) {
DT->addNewBlock(NewBB, BB);
DT->addNewBlock(FailBB, BB);
}
// Remove default branch instruction to the new BB.
BB->getTerminator()->eraseFromParent();
// 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(*BB, CmpInst::ICMP_EQ, LI1, LI2, "");
BranchInst::Create(NewBB, FailBB, Cmp, BB);
}
// Return if we didn't modify any basic blocks. I.e., there are no return