Re: [PATCH 6/6] x86: Fix -Os build (BZ #29576)

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 05/10/22 14:21, H.J. Lu wrote:
> On Wed, Oct 5, 2022 at 7:10 AM Carlos O'Donell <carlos@redhat.com> wrote:
>>
>> On Wed, Sep 21, 2022 at 10:51:08AM -0300, Adhemerval Zanella via Libc-alpha wrote:
>>> The compiler might transform __stpcpy calls (which are routed to
>>> __builtin_stpcpy as an optimization) to strcpy and x86_64 strcpy
>>> multiarch implementation does not build any working symbol due
>>> ISA_SHOULD_BUILD not being evaluated for IS_IN(rtld).
>>
>> Ohhhhhh... that is interesting. This changes the strcpy used in rtld for
>> all x86_64 build options, and I'm going to ACK this, but we may need to
>> revisit this if it shows up in a profile.
> 
> Will this lead to both strcpy and stpcpy in ld.so? Currently there is only
> stpcpy in ld.so.

I think that is expected behavior if compiler creates a reference for a
supported string function in the loader (rtld build pulls the
implementation).

> 
>> CC'ing HJ here in case he wants to comment as a machine maintainer.
>>
>> LGTM.
>>
>> No regressions on x86_64.
>>
>> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
>> Tested-by: Carlos O'Donell <carlos@redhat.com>
>>
>>> Checked on x86_64-linux-gnu.
>>> ---
>>>  sysdeps/x86_64/multiarch/rtld-strcpy.S | 18 ++++++++++++++++++
>>>  1 file changed, 18 insertions(+)
>>>  create mode 100644 sysdeps/x86_64/multiarch/rtld-strcpy.S
>>>
>>> diff --git a/sysdeps/x86_64/multiarch/rtld-strcpy.S b/sysdeps/x86_64/multiarch/rtld-strcpy.S
>>> new file mode 100644
>>> index 0000000000..19439c553d
>>> --- /dev/null
>>> +++ b/sysdeps/x86_64/multiarch/rtld-strcpy.S
>>> @@ -0,0 +1,18 @@
>>> +/* Copyright (C) 2022 Free Software Foundation, Inc.
>>> +   This file is part of the GNU C Library.
>>> +
>>> +   The GNU C Library is free software; you can redistribute it and/or
>>> +   modify it under the terms of the GNU Lesser General Public
>>> +   License as published by the Free Software Foundation; either
>>> +   version 2.1 of the License, or (at your option) any later version.
>>> +
>>> +   The GNU C Library is distributed in the hope that it will be useful,
>>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>> +   Lesser General Public License for more details.
>>> +
>>> +   You should have received a copy of the GNU Lesser General Public
>>> +   License along with the GNU C Library; if not, see
>>> +   <https://www.gnu.org/licenses/>.  */
>>> +
>>> +#include "../strcpy.S"
>>
>> OK. Uses Makeconfig:sysd-rules-patterns to capture rtld-*.
>>
>>> --
>>> 2.34.1
>>>
>>
> 
>