Re: __executable_start

[Emilio Pozuelo Monfort]

Hi,

On 26/05/13 16:38, Thomas Schwinge wrote:
> Hi!
>
> Re-submitting an oldie of Samuel's:
>
> On Sun, 24 Jun 2007 17:45:35 +0200, Samuel Thibault 
> <samuel.thibault@ens-lyon.org> wrote:
> > - _start points on the first instruction, not on the elf header.
> >    __executable_start does point on the elf header.
>
> > --- sysdeps/mach/hurd/i386/init-first.c.orig    2007-06-23 19:27:14.000000000 
> > +0000
> > +++ sysdeps/mach/hurd/i386/init-first.c 2007-06-23 21:41:40.000000000 +0000
> > @@ -116,14 +116,14 @@
> >         /* We may need to see our own phdrs, e.g. for TLS setup.
> >            Try the usual kludge to find the headers without help from
> >          the exec server.  */
> > -      extern const void _start;
> > -      const ElfW(Ehdr) *const ehdr = &_start;
> > +      extern const void __executable_start;
> > +      const ElfW(Ehdr) *const ehdr = &__executable_start;
> >         _dl_phdr = (ElfW(Phdr) *) ((const void *) ehdr + ehdr->e_phoff);
> >         _dl_phnum = ehdr->e_phnum;
> >         assert (ehdr->e_phentsize == sizeof (ElfW(Phdr)));
>
> This is, as far as I can tell, the only such usage of _start in glibc.
>
> OK to commit?
>
>         * sysdeps/mach/hurd/i386/init-first.c (init1): Use
>         __executable_start symbol intsead instead of _start.

Typo there, s/intsead//. Won't comment on the patch itself as I'm no ELF expert.

Cheers,
Emilio

> diff --git sysdeps/mach/hurd/i386/init-first.c 
> sysdeps/mach/hurd/i386/init-first.c
> index fc3330c..7031ed4 100644
> --- sysdeps/mach/hurd/i386/init-first.c
> +++ sysdeps/mach/hurd/i386/init-first.c
> @@ -125,8 +125,8 @@ init1 (int argc, char *arg0, ...)
>             /* We may need to see our own phdrs, e.g. for TLS setup.
>                Try the usual kludge to find the headers without help from
>                the exec server.  */
> -          extern const void _start;
> -          const ElfW(Ehdr) *const ehdr = &_start;
> +          extern const void __executable_start;
> +          const ElfW(Ehdr) *const ehdr = &__executable_start;
>             _dl_phdr = (const void *) ehdr + ehdr->e_phoff;
>             _dl_phnum = ehdr->e_phnum;
>             assert (ehdr->e_phentsize == sizeof (ElfW(Phdr)));
>
>
> Grüße,
>   Thomas