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[SafeStack] Use proper API to get stack guard 

Using the proper API automatically sets `__stack_chk_guard` to `dso_local` if
`Reloc::Static`. This wasn't strictly necessary until recently when dso_local was
no longer implied by `TargetMachine::shouldAssumeDSOLocal` for
`__stack_chk_guard`. By using the proper API, we can avoid generating unnecessary
GOT relocations.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D102646
This commit is contained in:
Pengxuan Zheng 2021-05-17 12:16:07 -07:00
parent 71cca4f728
commit 056733d019
3 changed files with 9 additions and 5 deletions
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10
llvm/lib/CodeGen/SafeStack.cpp
View File

@ -373,9 +373,13 @@ bool SafeStack::IsSafeStackAlloca(const Value *AllocaPtr, uint64_t AllocaSize) {
Value *SafeStack::getStackGuard(IRBuilder<> &IRB, Function &F) {
Value *StackGuardVar = TL.getIRStackGuard(IRB);
if (!StackGuardVar)
StackGuardVar =
F.getParent()->getOrInsertGlobal("__stack_chk_guard", StackPtrTy);
Module *M = F.getParent();
if (!StackGuardVar) {
TL.insertSSPDeclarations(*M);
return IRB.CreateCall(Intrinsic::getDeclaration(M, Intrinsic::stackguard));
}
return IRB.CreateLoad(StackPtrTy, StackGuardVar, "StackGuard");
}

2
llvm/test/Transforms/SafeStack/X86/abi_ssp.ll
View File

@ -13,7 +13,7 @@ entry:
; TLS32: %[[StackGuard:.*]] = load i8*, i8* addrspace(256)* inttoptr (i32 20 to i8* addrspace(256)*)
; TLS64: %[[StackGuard:.*]] = load i8*, i8* addrspace(257)* inttoptr (i32 40 to i8* addrspace(257)*)
; FUCHSIA64: %[[StackGuard:.*]] = load i8*, i8* addrspace(257)* inttoptr (i32 16 to i8* addrspace(257)*)
; GLOBAL32: %[[StackGuard:.*]] = load i8*, i8** @__stack_chk_guard
; GLOBAL32: %[[StackGuard:.*]] = call i8* @llvm.stackguard()
; COMMON: store i8* %[[StackGuard]], i8** %[[StackGuardSlot:.*]]
%a = alloca i8, align 1
call void @Capture(i8* %a)

2
llvm/test/Transforms/SafeStack/X86/ssp.ll
View File

@ -8,7 +8,7 @@ entry:
; CHECK: %[[A:.*]] = getelementptr i8, i8* %[[USP]], i32 -8
; CHECK: %[[StackGuardSlot:.*]] = bitcast i8* %[[A]] to i8**
; CHECK: %[[StackGuard:.*]] = load i8*, i8** @__stack_chk_guard
; CHECK: %[[StackGuard:.*]] = call i8* @llvm.stackguard()
; CHECK: store i8* %[[StackGuard]], i8** %[[StackGuardSlot]]
%a = alloca i8, align 1