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SubjectRe: [PATCH 04/24] x86/entry: Expose the address of .Lgs_change to traps.c
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On 2021/9/2 17:14, Peter Zijlstra wrote:
> On Wed, Sep 01, 2021 at 01:50:05AM +0800, Lai Jiangshan wrote:
>
>> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
>> index e38a4cf795d9..9164e85b36b8 100644
>> --- a/arch/x86/entry/entry_64.S
>> +++ b/arch/x86/entry/entry_64.S
>> @@ -729,6 +729,7 @@ _ASM_NOKPROBE(common_interrupt_return)
>> SYM_FUNC_START(asm_load_gs_index)
>> FRAME_BEGIN
>> swapgs
>> +SYM_INNER_LABEL(asm_load_gs_index_gs_change, SYM_L_GLOBAL)
>> .Lgs_change:
>
> After all the patches, there's only a single .Lgs_change reference left.
> Can't we convert the _ASM_EXTABLE() entry to use the new label and
> totally remove it?

The label .Lgs_change is still needed in ASM code for extable.

I tried the way as you suggested, and the result is:

warning: objtool: __ex_table+0x0: don't know how to handle non-section reloc symbol asm_load_gs_index_gs_change

But never mind, I have already converted load_gs_index into C code.
I will send it later.

>
>> movl %edi, %gs
>> 2: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE
>> @@ -1011,7 +1012,7 @@ SYM_CODE_START_LOCAL(error_entry)
>> movl %ecx, %eax /* zero extend */
>> cmpq %rax, RIP+8(%rsp)
>> je .Lbstep_iret
>> - cmpq $.Lgs_change, RIP+8(%rsp)
>> + cmpq $asm_load_gs_index_gs_change, RIP+8(%rsp)
>> jne .Lerror_entry_done_lfence

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