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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
22 lines
1.1 KiB
LLVM
22 lines
1.1 KiB
LLVM
; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
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; CHECK: "patchable-function-entry" takes an unsigned integer:
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; CHECK: "patchable-function-entry" takes an unsigned integer: a
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; CHECK: "patchable-function-entry" takes an unsigned integer: -1
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; CHECK: "patchable-function-entry" takes an unsigned integer: 3,
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define void @f() "patchable-function-entry" { ret void }
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define void @fa() "patchable-function-entry"="a" { ret void }
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define void @f_1() "patchable-function-entry"="-1" { ret void }
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define void @f3comma() "patchable-function-entry"="3," { ret void }
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; CHECK: "patchable-function-prefix" takes an unsigned integer:
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; CHECK: "patchable-function-prefix" takes an unsigned integer: a
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; CHECK: "patchable-function-prefix" takes an unsigned integer: -1
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; CHECK: "patchable-function-prefix" takes an unsigned integer: 3,
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define void @g() "patchable-function-prefix" { ret void }
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define void @ga() "patchable-function-prefix"="a" { ret void }
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define void @g_1() "patchable-function-prefix"="-1" { ret void }
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define void @g3comma() "patchable-function-prefix"="3," { ret void }
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