06b8e32d4f
Summary:
For -fpatchable-function-entry=N,0 -mbranch-protection=bti, after
9a24488cb6, we place the NOP sled after
the initial BTI.
```
.Lfunc_begin0:
bti c
nop
nop
.section __patchable_function_entries,"awo",@progbits,f,unique,0
.p2align 3
.xword .Lfunc_begin0
```
This patch adds a label after the initial BTI and changes the __patchable_function_entries entry to reference the label:
```
.Lfunc_begin0:
bti c
.Lpatch0:
nop
nop
.section __patchable_function_entries,"awo",@progbits,f,unique,0
.p2align 3
.xword .Lpatch0
```
This placement is compatible with the resolution in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92424 .
A local linkage function whose address is not taken does not need a BTI.
Placing the patch label after BTI has the advantage that code does not
need to differentiate whether the function has an initial BTI.
Reviewers: mrutland, nickdesaulniers, nsz, ostannard
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73680
85 lines
2.4 KiB
LLVM
85 lines
2.4 KiB
LLVM
; RUN: llc -mtriple=aarch64 %s -o - | FileCheck --check-prefixes=CHECK %s
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define void @f0() "patchable-function-entry"="0" "branch-target-enforcement" {
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; CHECK-LABEL: f0:
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; CHECK-NEXT: .Lfunc_begin0:
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; CHECK: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: ret
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; CHECK-NOT: .section __patchable_function_entries
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ret void
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}
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;; -fpatchable-function-entry=1 -mbranch-protection=bti
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;; For M=0, place the label .Lpatch0 after the initial BTI.
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define void @f1() "patchable-function-entry"="1" "branch-target-enforcement" {
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; CHECK-LABEL: f1:
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; CHECK-NEXT: .Lfunc_begin1:
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; CHECK: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: .Lpatch0:
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; CHECK-NEXT: nop
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; CHECK-NEXT: ret
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; CHECK: .section __patchable_function_entries,"awo",@progbits,f1,unique,0
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Lpatch0
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ret void
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}
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;; -fpatchable-function-entry=2,1 -mbranch-protection=bti
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define void @f2_1() "patchable-function-entry"="1" "patchable-function-prefix"="1" "branch-target-enforcement" {
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; CHECK-LABEL: .type f2_1,@function
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; CHECK-NEXT: .Ltmp0:
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; CHECK-NEXT: nop
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; CHECK-NEXT: f2_1:
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; CHECK-NEXT: .Lfunc_begin2:
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; CHECK: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: nop
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; CHECK-NEXT: ret
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; CHECK: .Lfunc_end2:
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; CHECK-NEXT: .size f2_1, .Lfunc_end2-f2_1
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; CHECK: .section __patchable_function_entries,"awo",@progbits,f1,unique,0
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Ltmp0
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ret void
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}
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;; -fpatchable-function-entry=1 -mbranch-protection=bti
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;; For M=0, don't create .Lpatch0 if the initial instruction is not BTI,
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;; even if other basic blocks may have BTI.
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define internal void @f1i(i64 %v) "patchable-function-entry"="1" "branch-target-enforcement" {
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; CHECK-LABEL: f1i:
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; CHECK-NEXT: .Lfunc_begin3:
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; CHECK: // %bb.0:
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; CHECK-NEXT: nop
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;; Other basic blocks have BTI, but they don't affect our decision to not create .Lpatch0
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; CHECK: .LBB{{.+}} // %sw.bb1
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; CHECK-NEXT: hint #36
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; CHECK: .section __patchable_function_entries,"awo",@progbits,f1,unique,0
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Lfunc_begin3
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entry:
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switch i64 %v, label %sw.bb0 [
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i64 1, label %sw.bb1
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i64 2, label %sw.bb2
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i64 3, label %sw.bb3
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i64 4, label %sw.bb4
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]
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sw.bb0:
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call void asm sideeffect "", ""()
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ret void
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sw.bb1:
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call void asm sideeffect "", ""()
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ret void
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sw.bb2:
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call void asm sideeffect "", ""()
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ret void
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sw.bb3:
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call void asm sideeffect "", ""()
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ret void
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sw.bb4:
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call void asm sideeffect "", ""()
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ret void
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}
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