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

[Adhemerval Zanella]

On 15/06/2017 12:51, H.J. Lu wrote:
> 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.
> 

Fair enough then.