Re: [PATCH 3/4] x86: open-code register save/restore in trace_hardirqs thunks

[Denys Vlasenko]

On Sat, Jan 10, 2015 at 11:07 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Sat, Jan 10, 2015 at 2:00 PM, Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
>> +       pushq_cfi %rdi
>> +       CFI_REL_OFFSET rdi, 0
>> +       pushq_cfi %rsi
>> +       CFI_REL_OFFSET rsi, 0
>> +       pushq_cfi %rdx
>> +       CFI_REL_OFFSET rdx, 0
> ..
> Ugh.
>
> This is too ugly, it needs to die.
>
> Why doesn't pushq_cfi do that CFI_REL_OFFSET thing?

I don't know either... it seems to be used after push_cfi
*sometimes*, not always:

.macro op_safe_regs op
ENTRY(\op\()_safe_regs)
        CFI_STARTPROC
        pushl_cfi %ebx
        pushl_cfi %ebp
        pushl_cfi %esi
        pushl_cfi %edi

but

ENTRY(csum_partial)
        CFI_STARTPROC
        pushl_cfi %esi
        CFI_REL_OFFSET esi, 0
        pushl_cfi %ebx
        CFI_REL_OFFSET ebx, 0

We need an expert to enlighten us.
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