[llvm][StackProtector] Add noreturn to __stack_chk_fail call #143976
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@llvm/pr-subscribers-llvm-transforms Author: None (PiJoules) ChangesIt's possible for __stack_chk_fail to be an alias when using CrossDSOCFI since it will make a jump table entry for this function and replace it with an alias. StackProtector can crash since it always expects this to be a regular function. I think it should be safe to continue treating this as an alias since we only call into it, and we can apply the noreturn attr to the underlying function if it is an alias. Full diff: https://github.com/llvm/llvm-project/pull/143976.diff 2 Files Affected:
diff --git a/llvm/lib/CodeGen/StackProtector.cpp b/llvm/lib/CodeGen/StackProtector.cpp
index 5f866eea7d4e7..0e5c421d2fa5e 100644
--- a/llvm/lib/CodeGen/StackProtector.cpp
+++ b/llvm/lib/CodeGen/StackProtector.cpp
@@ -725,7 +725,9 @@ BasicBlock *CreateFailBB(Function *F, const Triple &Trip) {
StackChkFail =
M->getOrInsertFunction("__stack_chk_fail", Type::getVoidTy(Context));
}
- cast<Function>(StackChkFail.getCallee())->addFnAttr(Attribute::NoReturn);
+ cast<Function>(
+ cast<GlobalValue>(StackChkFail.getCallee())->getAliaseeObject())
+ ->addFnAttr(Attribute::NoReturn);
B.CreateCall(StackChkFail, Args);
B.CreateUnreachable();
return FailBB;
diff --git a/llvm/test/Transforms/StackProtector/stack-chk-fail-alias.ll b/llvm/test/Transforms/StackProtector/stack-chk-fail-alias.ll
new file mode 100644
index 0000000000000..9314800cf0441
--- /dev/null
+++ b/llvm/test/Transforms/StackProtector/stack-chk-fail-alias.ll
@@ -0,0 +1,17 @@
+;; __stack_chk_fail should have the noreturn attr even if it is an alias
+; RUN: opt -triple=x86_64-pc-linux-gnu %s -passes=stack-protector -S | FileCheck %s
+
+define hidden void @__stack_chk_fail_impl() {
+ unreachable
+}
+
+@__stack_chk_fail = hidden alias void (), ptr @__stack_chk_fail_impl
+
+; CHECK-LABEL: @store_captures(
+define void @store_captures() sspstrong {
+entry:
+ %a = alloca i32, align 4
+ %j = alloca ptr, align 8
+ store ptr %a, ptr %j, align 8
+ ret void
+}
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Shouldn’t we have a test for crossdsocfi if that’s the bug you’re fixing gets exercised? Certainly the simple test you’ve added is good, but I’d think we want to test the actual failure case as well. |
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Done |
It's possible for __stack_chk_fail to be an alias when using CrossDSOCFI since it will make a jump table entry for this function and replace it with an alias. StackProtector can crash since it always expects this to be a regular function. I think it should be safe to continue treating this as an alias since we only call into it, and we can apply the noreturn attr to the underlying function if it is an alias.
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ilovepi
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Jun 16, 2025
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/21563 Here is the relevant piece of the build log for the reference |
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…#144452) Reverts #143976 Reverting since this broke a builder: https://lab.llvm.org/buildbot/#/builders/190/builds/21563
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…_fail call" (#144452) Reverts llvm/llvm-project#143976 Reverting since this broke a builder: https://lab.llvm.org/buildbot/#/builders/190/builds/21563
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It's possible for __stack_chk_fail to be an alias when using CrossDSOCFI since it will make a jump table entry for this function and replace it with an alias. StackProtector can crash since it always expects this to be a regular function. Instead add the noreturn attribute to the call.