22467e2595
Similar to the function attribute `prefix` (prefix data), "patchable-function-prefix" inserts data (M NOPs) before the function entry label. -fpatchable-function-entry=2,1 (1 NOP before entry, 1 NOP after entry) will look like: ``` .type foo,@function .Ltmp0: # @foo nop foo: .Lfunc_begin0: # optional `bti c` (AArch64 Branch Target Identification) or # `endbr64` (Intel Indirect Branch Tracking) nop .section __patchable_function_entries,"awo",@progbits,get,unique,0 .p2align 3 .quad .Ltmp0 ``` -fpatchable-function-entry=N,0 + -mbranch-protection=bti/-fcf-protection=branch has two reasonable placements (https://gcc.gnu.org/ml/gcc-patches/2020-01/msg01185.html): ``` (a) (b) func: func: .Ltmp0: bti c bti c .Ltmp0: nop nop ``` (a) needs no additional code. If the consensus is to go for (b), we will need more code in AArch64BranchTargets.cpp / X86IndirectBranchTracking.cpp . Differential Revision: https://reviews.llvm.org/D73070
106 lines
3.6 KiB
LLVM
106 lines
3.6 KiB
LLVM
; RUN: llc -mtriple=aarch64 %s -o - | FileCheck --check-prefixes=CHECK,NOFSECT %s
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; RUN: llc -mtriple=aarch64 -function-sections %s -o - | FileCheck --check-prefixes=CHECK,FSECT %s
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; RUN: llc -mtriple=aarch64 -no-integrated-as %s -o - | FileCheck --check-prefix=NOLINK %s
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; NOLINK-NOT: "awo"
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; NOLINK-NOT: ,unique,0
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define i32 @f0() "patchable-function-entry"="0" {
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; CHECK-LABEL: f0:
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; CHECK-NEXT: .Lfunc_begin0:
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; CHECK-NOT: nop
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; CHECK: mov w0, wzr
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; CHECK-NOT: .section __patchable_function_entries
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ret i32 0
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}
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define i32 @f1() "patchable-function-entry"="1" {
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; CHECK-LABEL: f1:
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; CHECK-NEXT: .Lfunc_begin1:
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; CHECK: nop
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; CHECK-NEXT: mov w0, wzr
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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_begin1
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ret i32 0
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}
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;; Without -function-sections, f2 is in the same text section as f1.
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;; They share the __patchable_function_entries section.
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;; With -function-sections, f1 and f2 are in different text sections.
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;; Use separate __patchable_function_entries.
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define void @f2() "patchable-function-entry"="2" {
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; CHECK-LABEL: f2:
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; CHECK-NEXT: .Lfunc_begin2:
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; CHECK-COUNT-2: nop
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; CHECK-NEXT: ret
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; NOFSECT: .section __patchable_function_entries,"awo",@progbits,f1,unique,0
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; FSECT: .section __patchable_function_entries,"awo",@progbits,f2,unique,1
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Lfunc_begin2
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ret void
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}
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$f3 = comdat any
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define void @f3() "patchable-function-entry"="3" comdat {
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; CHECK-LABEL: f3:
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; CHECK-NEXT: .Lfunc_begin3:
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; CHECK-COUNT-3: nop
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; CHECK-NEXT: ret
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; NOFSECT: .section __patchable_function_entries,"aGwo",@progbits,f3,comdat,f3,unique,1
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; FSECT: .section __patchable_function_entries,"aGwo",@progbits,f3,comdat,f3,unique,2
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Lfunc_begin3
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ret void
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}
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$f5 = comdat any
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define void @f5() "patchable-function-entry"="5" comdat {
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; CHECK-LABEL: f5:
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; CHECK-NEXT: .Lfunc_begin4:
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; CHECK-COUNT-5: nop
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; CHECK-NEXT: sub sp, sp, #16
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; NOFSECT .section __patchable_function_entries,"aGwo",@progbits,f5,comdat,f5,unique,2
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; FSECT: .section __patchable_function_entries,"aGwo",@progbits,f5,comdat,f5,unique,3
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; CHECK: .p2align 3
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; CHECK-NEXT: .xword .Lfunc_begin4
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%frame = alloca i8, i32 16
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ret void
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}
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;; -fpatchable-function-entry=3,2
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;; "patchable-function-prefix" emits data before the function entry label.
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define void @f3_2() "patchable-function-entry"="1" "patchable-function-prefix"="2" {
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; CHECK-LABEL: .type f3_2,@function
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; CHECK-NEXT: .Ltmp1: // @f3_2
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; CHECK-NEXT: nop
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; CHECK-NEXT: nop
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; CHECK-NEXT: f3_2:
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; CHECK: // %bb.0:
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; CHECK-NEXT: nop
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; CHECK-NEXT: ret
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;; .size does not include the prefix.
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; CHECK: .Lfunc_end5:
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; CHECK-NEXT: .size f3_2, .Lfunc_end5-f3_2
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; NOFSECT .section __patchable_function_entries,"awo",@progbits,f1,unique,0
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; FSECT: .section __patchable_function_entries,"awo",@progbits,f3_2,unique,4
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; CHECK: .p2align 3
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; CHECK-NEXT: .xword .Ltmp1
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ret void
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}
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;; When prefix data is used, arbitrarily place NOPs after prefix data.
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define void @prefix() "patchable-function-entry"="0" "patchable-function-prefix"="1" prefix i32 1 {
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; CHECK-LABEL: .type prefix,@function
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; CHECK-NEXT: .word 1 // @prefix
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; CHECK: .Ltmp2:
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; CHECK: nop
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; CHECK-NEXT: prefix:
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;; Emit a __patchable_function_entries entry even if "patchable-function-entry" is 0.
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; NOFSECT .section __patchable_function_entries,"awo",@progbits,prefix,unique,0
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; FSECT: .section __patchable_function_entries,"awo",@progbits,prefix,unique,5
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; CHECK: .p2align 3
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; CHECK-NEXT: .xword .Ltmp2
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ret void
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}
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