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SubjectRe: [PATCH v8 04/28] x86/asm/entry: annotate THUNKs
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On 15. 08. 19, 14:43, Borislav Petkov wrote:
> On Thu, Aug 08, 2019 at 12:38:30PM +0200, Jiri Slaby wrote:
>> Place SYM_*_START_NOALIGN and SYM_*_END around the THUNK macro body.
>> Preserve @function by FUNC (64bit) and CODE (32bit). Given it was not
>> marked as aligned, use NOALIGN.
>>
>> The common tail .L_restore is put inside SYM_CODE_START_LOCAL_NOALIGN
>> and SYM_CODE_END too.
>
> What is that needed for? It is a local label...
>
>> The result:
>> Value Size Type Bind Vis Ndx Name
>> 0000 28 FUNC GLOBAL DEFAULT 1 trace_hardirqs_on_thunk
>> 001c 28 FUNC GLOBAL DEFAULT 1 trace_hardirqs_off_thunk
>> 0038 24 FUNC GLOBAL DEFAULT 1 lockdep_sys_exit_thunk
>> 0050 24 FUNC GLOBAL DEFAULT 1 ___preempt_schedule
>> 0068 24 FUNC GLOBAL DEFAULT 1 ___preempt_schedule_notra
>
> No difference except alignment:

Yeah, alignment is one and visual effect the other. One can immediately
see where it starts and where it ends -- readability. There is no other
functional meaning, so I don't mind not annotating it. It's your call. So?

before:

#if defined(CONFIG_TRACE_IRQFLAGS) \
|| defined(CONFIG_DEBUG_LOCK_ALLOC) \
|| defined(CONFIG_PREEMPTION)
.L_restore:
popq %r11
popq %r10
popq %r9
popq %r8
popq %rax
popq %rcx
popq %rdx
popq %rsi
popq %rdi
popq %rbp
ret
_ASM_NOKPROBE(.L_restore)
#endif

after:
#if defined(CONFIG_TRACE_IRQFLAGS) \
|| defined(CONFIG_DEBUG_LOCK_ALLOC) \
|| defined(CONFIG_PREEMPTION)
SYM_CODE_START_LOCAL_NOALIGN(.L_restore)
popq %r11
popq %r10
popq %r9
popq %r8
popq %rax
popq %rcx
popq %rdx
popq %rsi
popq %rdi
popq %rbp
ret
_ASM_NOKPROBE(.L_restore)
SYM_CODE_END(.L_restore)
#endif


thanks,
--
js
suse labs

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