Re: [PATCH] x86-64: Implement strcat family IFUNC selectors in C

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Jun 15, 2017 at 8:32 AM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
> On 12/06/2017 13:10, H.J. Lu wrote:
>> Implement strcat family IFUNC selectors in C.
>>
>> All internal calls within libc.so can use IFUNC on x86-64 since unlike
>> x86, x86-64 supports PC-relative addressing to access the GOT entry so
>> that it can call via PLT without using an extra register.  For libc.a,
>> we can't use IFUNC for functions which are called before IFUNC has been
>> initialized.  Use IFUNC internally reduces the icache footprint since
>> libc.so and other codes in the process use the same implementations.
>> This patch uses IFUNC for strcat family functions within libc.
>>
>> Any comments?
>>
>> H.J.
>>       * sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
>>       strcat-sse2.
>>       * sysdeps/x86_64/multiarch/strcat-sse2.S: New file.
>>       * sysdeps/x86_64/multiarch/strcat.c: Likewise.
>>       * sysdeps/x86_64/multiarch/strncat.c: Likewise.
>>       * sysdeps/x86_64/multiarch/strcat.S: Removed.
>>       * sysdeps/x86_64/multiarch/strncat.S: Likewise.
>
> LGTM, but since the idea is to use IFUNC for internal symbol call, do we
> still need the assembly implementation for x86_64? Default algorithm should
> be good enough with both vectorized strlen and strcpy (same for strncat)

That will be a separate patch.  We will look into these for 2.27.

Thanks.

-- 
H.J.