b7926ce6d7
It's currently ambiguous in IR whether the source language explicitly did not want a stack a stack protector (in C, via function attribute no_stack_protector) or doesn't care for any given function. 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 Typically, when inlining a callee into a caller, the caller will be upgraded in its level of stack protection (see adjustCallerSSPLevel()). By adding an explicit attribute in the IR when the function attribute is used in the source language, we can now identify such cases and prevent inlining. Block inlining when the callee and caller differ in the case that one contains `nossp` when the other has `ssp`, `sspstrong`, or `sspreq`. Fixes pr/47479. Reviewed By: void Differential Revision: https://reviews.llvm.org/D87956
86 lines
2.5 KiB
LLVM
86 lines
2.5 KiB
LLVM
; RUN: opt < %s -S -partial-inliner -skip-partial-inlining-cost-analysis=true | FileCheck %s
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define i32 @callee_most(i32 %v) unnamed_addr #0 #1 {
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entry:
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%cmp = icmp sgt i32 %v, 2000
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br i1 %cmp, label %if.then, label %if.end
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if.then:
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br label %if.then2
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if.then2:
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%sub = sub i32 %v, 10
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br label %if.end
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if.end:
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%v2 = phi i32 [ %v, %entry ], [ %sub, %if.then2 ]
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%add = add nsw i32 %v2, 200
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ret i32 %add
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}
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define i32 @callee_noinline(i32 %v) optnone noinline {
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entry:
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%cmp = icmp sgt i32 %v, 2000
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br i1 %cmp, label %if.then, label %if.end
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if.then:
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br label %if.then2
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if.then2:
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%sub = sub i32 %v, 10
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br label %if.end
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if.end:
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%v2 = phi i32 [ %v, %entry ], [ %sub, %if.then2 ]
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%add = add nsw i32 %v2, 200
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ret i32 %add
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}
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define i32 @callee_writeonly(i32 %v) writeonly {
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entry:
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%cmp = icmp sgt i32 %v, 2000
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br i1 %cmp, label %if.then, label %if.end
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if.then:
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br label %if.then2
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if.then2:
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%sub = sub i32 %v, 10
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br label %if.end
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if.end:
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%v2 = phi i32 [ %v, %entry ], [ %sub, %if.then2 ]
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%add = add nsw i32 %v2, 200
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ret i32 %add
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}
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; CHECK-LABEL: @caller
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; CHECK: call void @callee_most.2.if.then(i32 %v
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; CHECK: call i32 @callee_noinline(i32 %v)
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; CHECK: call void @callee_writeonly.1.if.then(i32 %v
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define i32 @caller(i32 %v) {
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entry:
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%c1 = call i32 @callee_most(i32 %v)
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%c2 = call i32 @callee_noinline(i32 %v)
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%c3 = call i32 @callee_writeonly(i32 %v)
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ret i32 %c3
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}
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; CHECK: define internal void @callee_writeonly.1.if.then(i32 %v, i32* %sub.out) {
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; CHECK: define internal void @callee_most.2.if.then(i32 %v, i32* %sub.out) [[FN_ATTRS:#[0-9]+]]
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; attributes to preserve
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attributes #0 = {
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inlinehint minsize noduplicate noimplicitfloat norecurse noredzone nounwind
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nonlazybind optsize safestack sanitize_address sanitize_hwaddress sanitize_memory
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sanitize_thread sspstrong strictfp uwtable "foo"="bar"
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"patchable-function"="prologue-short-redirect" "probe-stack"="_foo_guard" "stack-probe-size"="4096" }
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; CHECK: attributes [[FN_ATTRS]] = { inlinehint minsize noduplicate noimplicitfloat norecurse noredzone nounwind nonlazybind optsize safestack sanitize_address sanitize_hwaddress sanitize_memory sanitize_thread sspstrong strictfp uwtable "foo"="bar" "patchable-function"="prologue-short-redirect" "probe-stack"="_foo_guard" "stack-probe-size"="4096" }
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; attributes to drop
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attributes #1 = {
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alignstack=16 convergent inaccessiblememonly inaccessiblemem_or_argmemonly naked
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noreturn readonly argmemonly returns_twice speculatable "thunk"
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}
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