From: "H.J. Lu" <hjl.tools@gmail.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH] Don't use PLT nor GOT in libc.a [BZ #20750]
Date: Mon, 07 Nov 2016 17:14:00 -0000 [thread overview]
Message-ID: <CAMe9rOqWq--vo3T8NhEpFGuyA7Z8hHVN_DK6g8rauVaxYKZ+ig@mail.gmail.com> (raw)
In-Reply-To: <1129b1b2-5f7a-26c3-76a7-727a14fdadfb@redhat.com>
On Mon, Nov 7, 2016 at 8:03 AM, Florian Weimer <fweimer@redhat.com> wrote:
> On 11/04/2016 08:25 PM, H.J. Lu wrote:
>>
>> On Fri, Nov 4, 2016 at 12:03 PM, Florian Weimer <fweimer@redhat.com>
>> wrote:
>>>
>>> On 11/04/2016 06:47 PM, H.J. Lu wrote:
>>>>
>>>>
>>>> There is no need to use PLT nor GOT in libc.a to branch to a function,
>>>> regardless whether libc.a is compiled with PIC or not.
>>>>
>>>> Tested on x86-64. OK for master?
>>>
>>>
>>>
>>> Isn't this header file used outside of libc as well?
>>
>>
>> It is used for other .a files. If they aren't used to create static
>> binaries,
>> PLT/GOT may be used. The resulting executable will work correctly.
>
>
> You mean because “name” is automatically mapped to “name@plt”?
No. There is no "@plt". Linker will create a PLT entry if the function
is defined in a shared object.
> I find this comment not very illuminating:
>
> +/* For libc.a, we want to branch to target directly. */
> # define JUMPTARGET(name) name
>
> And cheating the static linker in this way seems like a future maintenance
> hazard.
>
It is ok as long as those static archives aren't used to create shared
objects.
--
H.J.
next prev parent reply other threads:[~2016-11-07 17:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-04 17:47 H.J. Lu
2016-11-04 19:03 ` Florian Weimer
2016-11-04 19:25 ` H.J. Lu
2016-11-07 16:03 ` Florian Weimer
2016-11-07 17:14 ` H.J. Lu [this message]
2016-11-24 11:58 ` Allan McRae
2016-11-25 8:43 ` Florian Weimer
2016-11-28 17:46 ` H.J. Lu
2016-11-28 18:27 ` Joseph Myers
2016-11-28 21:32 ` H.J. Lu
2016-11-28 17:54 ` Szabolcs Nagy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAMe9rOqWq--vo3T8NhEpFGuyA7Z8hHVN_DK6g8rauVaxYKZ+ig@mail.gmail.com \
--to=hjl.tools@gmail.com \
--cc=fweimer@redhat.com \
--cc=libc-alpha@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).