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Re: IFUNCs used by libc.so.6 internally on x86-64
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Andreas Schwab <schwab at suse dot de>
- Cc: Florian Weimer <fweimer at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 6 Jun 2017 19:11:03 -0700
- Subject: Re: IFUNCs used by libc.so.6 internally on x86-64
- Authentication-results: sourceware.org; auth=none
- References: <35ad727a-a910-b5a3-0829-905e3bf0abcf@redhat.com> <mvm8tldujwf.fsf@suse.de>
On Wed, May 31, 2017 at 8:26 AM, Andreas Schwab <schwab@suse.de> wrote:
> On Feb 06 2017, Florian Weimer <fweimer@redhat.com> wrote:
>
>> The selection of string functions is rather curious. Were these choices
>> deliberate?
>
> They probably just happen, because check-localplt doesn't fail.
>
I believe all internal calls within libc.so can use IFUNC on x86-64 since
unlike x86, x86-64 doesn't need to reserve a register to make a PLT call.
For libc,a, we can't use IFUNC for functions which are called before IFUNC
has been initialized.
--
H.J.