Re: [hurd,commited] hurd: Avoid more libc.so local PLTs

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Apr 3, 2018 at 3:18 PM, Samuel Thibault
<samuel.thibault@ens-lyon.org> wrote:
> H.J. Lu, on mar. 03 avril 2018 15:14:16 -0700, wrote:
>> On Tue, Apr 3, 2018 at 2:55 PM, Samuel Thibault
>> <samuel.thibault@ens-lyon.org> wrote:
>> > H.J. Lu, on mar. 03 avril 2018 14:41:27 -0700, wrote:
>> >> On Tue, Apr 3, 2018 at 2:24 PM, Samuel Thibault
>> >> <samuel.thibault@ens-lyon.org> wrote:
>> >> > H.J. Lu, on mar. 03 avril 2018 14:16:50 -0700, wrote:
>> >> >> On Tue, Apr 3, 2018 at 2:07 PM, Samuel Thibault
>> >> >> <samuel.thibault@ens-lyon.org> wrote:
>> >> >> > Hello,
>> >> >> >
>> >> >> > H.J. Lu, on mar. 03 avril 2018 12:26:33 -0700, wrote:
>> >> >> >> __libc_longjmp and __libc_siglongjmp are private external functions provided for
>> >> >> >> libpthread.  They should never be called inside libc.
>> >> >> >
>> >> >> > I'm sorry for asking, but are these conventions documented somewhere?
>> >> >> > These look like magic to me otherwise:
>> >> >>
>> >> >> I don't believe they are well documented.
>> >> >
>> >> > Ok, then I need an answer to my question:
>> >> >
>> >> >> > why shouldn't they ever be called from libc?
>> >> >
>> >> > The existing hurd code does use them for catching signals, so I need to
>> >> > know how to fix it.
>> >>
>> >> Use something similar to
>> >>
>> >> libc_hidden_proto (_setjmp)
>> >> libc_hidden_proto (__sigsetjmp)
>> >
>> > So I'd just add hidden protos & defs to longjmp and siglongjmp?
>> >
>>
>> setjmp/longjmp.c has
>>
>> weak_alias (__libc_siglongjmp, _longjmp)
>> weak_alias (__libc_siglongjmp, longjmp)
>>
>> Will
>>
>> libc_hidden_proto (_longjmp)
>>
>> work for you?
>
> Well, _longjmp is the BSD version of longjmp with the semantic of
> siglongjmp (actually it's _setjmp which makes the semantic different,
> recorded in the jmp_buf). Here we do use longjmp, not _longjmp. Of
> course, the end pointer is the same since it's _setjmp which makes
> the semantic different, but I'd really rather not make the code more
> confusing by using _longjmp while it is actually a longjmp which is
> meant.

Aren't  the internal symbols of _longjmp, longjmp and siglongjmp
pointing to the same __libc_siglongjmp function?

-- 
H.J.