bc044a88ee
It's common for code that manipulates the stack via inline assembly or that has to set up its own stack canary (such as the Linux kernel) would like to avoid stack protectors in certain functions. In this case, we've been bitten by numerous bugs where a callee with a stack protector is inlined into an attribute((no_stack_protector)) caller, which generally breaks the caller's assumptions about not having a stack protector. LTO exacerbates the issue. While developers can avoid this by putting all no_stack_protector functions in one translation unit together and compiling those with -fno-stack-protector, it's generally not very ergonomic or as ergonomic as a function attribute, and still doesn't work for LTO. See also: https://lore.kernel.org/linux-pm/20200915172658.1432732-1-rkir@google.com/ https://lore.kernel.org/lkml/20200918201436.2932360-30-samitolvanen@google.com/T/#u SSP attributes can be ordered by strength. Weakest to strongest, they are: ssp, sspstrong, sspreq. Callees with differing SSP attributes may be inlined into each other, and the strongest attribute will be applied to the caller. (No change) After this change: * A callee with no SSP attributes will no longer be inlined into a caller with SSP attributes. * The reverse is also true: a callee with an SSP attribute will not be inlined into a caller with no SSP attributes. * The alwaysinline attribute overrides these rules. Functions that get synthesized by the compiler may not get inlined as a result if they are not created with the same stack protector function attribute as their callers. Alternative approach to https://reviews.llvm.org/D87956. Fixes pr/47479. Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed By: rnk, MaskRay Differential Revision: https://reviews.llvm.org/D91816
98 lines
3.5 KiB
LLVM
98 lines
3.5 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -inline -o - -S %s | FileCheck %s
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; RUN: opt -passes='cgscc(inline)' %s -S | FileCheck %s
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; RUN: opt -always-inline -o - -S %s | FileCheck %s
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; RUN: opt -passes=always-inline -o - -S %s | FileCheck %s
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declare dso_local void @foo(i8*)
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; Not interesting to test.
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define dso_local void @ssp(i64 %0) #0 {
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%2 = alloca i64, align 8
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store i64 %0, i64* %2, align 8
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%3 = load i64, i64* %2, align 8
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%4 = alloca i8, i64 %3, align 16
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call void @foo(i8* %4)
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ret void
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}
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; Not interesting to test.
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define dso_local void @ssp_alwaysinline(i64 %0) #1 {
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%2 = alloca i64, align 8
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store i64 %0, i64* %2, align 8
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%3 = load i64, i64* %2, align 8
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%4 = alloca i8, i64 %3, align 16
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call void @foo(i8* %4)
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ret void
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}
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; @ssp should not be inlined due to mismatch stack protector.
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; @ssp_alwaysinline should be inlined due to alwaysinline.
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define dso_local void @nossp() {
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; CHECK-LABEL: @nossp(
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; CHECK-NEXT: [[TMP1:%.*]] = alloca i64, align 8
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; CHECK-NEXT: call void @ssp(i64 1024)
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; CHECK-NEXT: [[SAVEDSTACK:%.*]] = call i8* @llvm.stacksave()
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; CHECK-NEXT: [[TMP2:%.*]] = bitcast i64* [[TMP1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 8, i8* [[TMP2]])
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; CHECK-NEXT: store i64 1024, i64* [[TMP1]], align 8
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; CHECK-NEXT: [[TMP3:%.*]] = load i64, i64* [[TMP1]], align 8
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; CHECK-NEXT: [[TMP4:%.*]] = alloca i8, i64 [[TMP3]], align 16
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; CHECK-NEXT: call void @foo(i8* [[TMP4]])
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; CHECK-NEXT: [[TMP5:%.*]] = bitcast i64* [[TMP1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 8, i8* [[TMP5]])
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; CHECK-NEXT: call void @llvm.stackrestore(i8* [[SAVEDSTACK]])
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; CHECK-NEXT: ret void
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;
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call void @ssp(i64 1024)
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call void @ssp_alwaysinline(i64 1024)
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ret void
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}
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; This is the same case as @nossp above. That the caller has alwaysinline is
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; irrelevant. Not interesting to test.
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define dso_local void @nossp_alwaysinline() #2 {
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call void @ssp(i64 1024)
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call void @ssp_alwaysinline(i64 1024)
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ret void
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}
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; @nossp_alwaysinline should be inlined due to alwaysinline.
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; @ssp should not be inlined due to mismatch stack protector.
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; @ssp_alwaysinline should be inlined due to alwaysinline.
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define dso_local void @nossp_caller() {
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; CHECK-LABEL: @nossp_caller(
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; CHECK-NEXT: [[TMP1:%.*]] = alloca i64, align 8
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; CHECK-NEXT: [[SAVEDSTACK:%.*]] = call i8* @llvm.stacksave()
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; CHECK-NEXT: call void @ssp(i64 1024)
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; CHECK-NEXT: [[SAVEDSTACK_I:%.*]] = call i8* @llvm.stacksave()
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; CHECK-NEXT: [[TMP2:%.*]] = bitcast i64* [[TMP1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 8, i8* [[TMP2]])
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; CHECK-NEXT: store i64 1024, i64* [[TMP1]], align 8
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; CHECK-NEXT: [[TMP3:%.*]] = load i64, i64* [[TMP1]], align 8
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; CHECK-NEXT: [[TMP4:%.*]] = alloca i8, i64 [[TMP3]], align 16
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; CHECK-NEXT: call void @foo(i8* [[TMP4]])
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; CHECK-NEXT: [[TMP5:%.*]] = bitcast i64* [[TMP1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 8, i8* [[TMP5]])
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; CHECK-NEXT: call void @llvm.stackrestore(i8* [[SAVEDSTACK_I]])
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; CHECK-NEXT: call void @llvm.stackrestore(i8* [[SAVEDSTACK]])
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; CHECK-NEXT: ret void
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;
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call void @nossp_alwaysinline()
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ret void
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}
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; @nossp should not be inlined due to mismatch stack protector.
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define dso_local void @ssp2() #0 {
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; CHECK-LABEL: @ssp2(
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; CHECK-NEXT: call void @nossp()
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; CHECK-NEXT: ret void
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;
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call void @nossp()
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ret void
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}
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attributes #0 = { sspstrong }
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attributes #1 = { sspstrong alwaysinline }
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attributes #2 = { alwaysinline}
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