[safestack] Make sure the unsafe stack pointer is popped in all cases
The unsafe stack pointer is only popped in moveStaticAllocasToUnsafeStack so it won't happen if there are no static allocas.
Fixes https://llvm.org/bugs/show_bug.cgi?id=26122
Differential Revision: http://reviews.llvm.org/D16339
llvm-svn: 259447
diff --git a/llvm/lib/CodeGen/SafeStack.cpp b/llvm/lib/CodeGen/SafeStack.cpp
index 7adcdea..c1c6ab6 100644
--- a/llvm/lib/CodeGen/SafeStack.cpp
+++ b/llvm/lib/CodeGen/SafeStack.cpp
@@ -144,7 +144,8 @@
Value *moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
ArrayRef<AllocaInst *> StaticAllocas,
ArrayRef<Argument *> ByValArguments,
- ArrayRef<ReturnInst *> Returns);
+ ArrayRef<ReturnInst *> Returns,
+ Instruction *BasePointer);
/// \brief Generate code to restore the stack after all stack restore points
/// in \p StackRestorePoints.
@@ -431,6 +432,8 @@
SafeStack::createStackRestorePoints(IRBuilder<> &IRB, Function &F,
ArrayRef<Instruction *> StackRestorePoints,
Value *StaticTop, bool NeedDynamicTop) {
+ assert(StaticTop && "The stack top isn't set.");
+
if (StackRestorePoints.empty())
return nullptr;
@@ -441,19 +444,13 @@
// runtime itself.
AllocaInst *DynamicTop = nullptr;
- if (NeedDynamicTop)
+ if (NeedDynamicTop) {
// If we also have dynamic alloca's, the stack pointer value changes
// throughout the function. For now we store it in an alloca.
DynamicTop = IRB.CreateAlloca(StackPtrTy, /*ArraySize=*/nullptr,
"unsafe_stack_dynamic_ptr");
-
- if (!StaticTop)
- // We need the original unsafe stack pointer value, even if there are
- // no unsafe static allocas.
- StaticTop = IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr");
-
- if (NeedDynamicTop)
IRB.CreateStore(StaticTop, DynamicTop);
+ }
// Restore current stack pointer after longjmp/exception catch.
for (Instruction *I : StackRestorePoints) {
@@ -467,29 +464,18 @@
return DynamicTop;
}
+/// We explicitly compute and set the unsafe stack layout for all unsafe
+/// static alloca instructions. We save the unsafe "base pointer" in the
+/// prologue into a local variable and restore it in the epilogue.
Value *SafeStack::moveStaticAllocasToUnsafeStack(
IRBuilder<> &IRB, Function &F, ArrayRef<AllocaInst *> StaticAllocas,
- ArrayRef<Argument *> ByValArguments, ArrayRef<ReturnInst *> Returns) {
+ ArrayRef<Argument *> ByValArguments, ArrayRef<ReturnInst *> Returns,
+ Instruction *BasePointer) {
if (StaticAllocas.empty() && ByValArguments.empty())
- return nullptr;
+ return BasePointer;
DIBuilder DIB(*F.getParent());
- // We explicitly compute and set the unsafe stack layout for all unsafe
- // static alloca instructions. We save the unsafe "base pointer" in the
- // prologue into a local variable and restore it in the epilogue.
-
- // Load the current stack pointer (we'll also use it as a base pointer).
- // FIXME: use a dedicated register for it ?
- Instruction *BasePointer =
- IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr");
- assert(BasePointer->getType() == StackPtrTy);
-
- for (ReturnInst *RI : Returns) {
- IRB.SetInsertPoint(RI);
- IRB.CreateStore(BasePointer, UnsafeStackPtr);
- }
-
// Compute maximum alignment among static objects on the unsafe stack.
unsigned MaxAlignment = 0;
for (Argument *Arg : ByValArguments) {
@@ -726,9 +712,16 @@
IRBuilder<> IRB(&F.front(), F.begin()->getFirstInsertionPt());
UnsafeStackPtr = getOrCreateUnsafeStackPtr(IRB, F);
+ // Load the current stack pointer (we'll also use it as a base pointer).
+ // FIXME: use a dedicated register for it ?
+ Instruction *BasePointer =
+ IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr");
+ assert(BasePointer->getType() == StackPtrTy);
+
// The top of the unsafe stack after all unsafe static allocas are allocated.
Value *StaticTop = moveStaticAllocasToUnsafeStack(IRB, F, StaticAllocas,
- ByValArguments, Returns);
+ ByValArguments, Returns,
+ BasePointer);
// Safe stack object that stores the current unsafe stack top. It is updated
// as unsafe dynamic (non-constant-sized) allocas are allocated and freed.
@@ -743,6 +736,12 @@
moveDynamicAllocasToUnsafeStack(F, UnsafeStackPtr, DynamicTop,
DynamicAllocas);
+ // Restore the unsafe stack pointer before each return.
+ for (ReturnInst *RI : Returns) {
+ IRB.SetInsertPoint(RI);
+ IRB.CreateStore(BasePointer, UnsafeStackPtr);
+ }
+
DEBUG(dbgs() << "[SafeStack] safestack applied\n");
return true;
}