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Re: IFUNCs used by libc.so.6 internally on x86-64
On Tue, Jun 6, 2017 at 10:50 PM, Florian Weimer <fweimer@redhat.com> wrote:
> On 06/07/2017 04:11 AM, H.J. Lu wrote:
>> 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.
>
> I see IFUNC relocations on i386 as well:
>
> Relocation section [10] '.rel.plt' for section [33] '.got.plt' at offset
> 0x17678 contains 3 entries:
> Offset Type Value Name
> 0x001d7014 386_IRELATIVE 0000000000
> 0x001d7010 386_IRELATIVE 0000000000
> 0x001d700c 386_IRELATIVE 0000000000
>
> Unfortunately, it's really hard to figure out what they are.
>
Please try -z print-local-ifuncs:
https://sourceware.org/ml/binutils/2017-06/msg00066.html
--
H.J.