Re: [PATCH] ppc vdso, A working gettimeofday

[Steve Munroe <sjmunroe at us dot ibm dot com>]

Ulrich Drepper <drepper@redhat.com> wrote on 04/29/2005 05:29:19 PM:

> Steve Munroe wrote:
> 
> > +    _dl_vdso_sym; _dl_vdso_vsym;
> 
> There is no reason to add these symbols anywhere but ppc/linux.  Despite
> what you might want to believe, ppc/linux is not the only platform that
> matters.
> 
Resolving symbols in a VDSO seems like a common GLIBC/Linux problem. So I 
was trying to provide a common GLIBC/Linux solution.

> 
> > diff -urN libc24-cvstip-20050427/elf/dl-vdso.c libc24/elf/dl-vdso.c
> > --- libc24-cvstip-20050427/elf/dl-vdso.c   Wed Dec 31 18:00:00 1969
> > +++ libc24/elf/dl-vdso.c   Thu Apr 28 17:26:43 2005
> > @@ -0,0 +1,85 @@
> 
> Likewise for this file.  Move in specific directory.
> 
Oops that should have gone to sysdeps/unix/sysv/linux as VDSO is Linux 
specific but not necessarily powerpc specific.

> 
> Haven't you paid any attention to the coding standard in all this time?
>  Fix the indentation.
> 
Done.

> 
> > diff -urN libc24-cvstip-20050427/elf/rtld.c libc24/elf/rtld.c
> > --- libc24-cvstip-20050427/elf/rtld.c   2005-04-07 15:56:48.000000000 
-0500
> > +++ libc24/elf/rtld.c   2005-04-27 15:52:25.000000000 -0500
> > @@ -1274,6 +1274,13 @@
> >       elf_get_dynamic_info (l, dyn_temp);
> >       _dl_setup_hash (l);
> >       l->l_relocated = 1;
> > +     /* Initialize l_local_scope to contain just this map. This 
allows 
> > +        the use of dl_lookup_symbol_x to resolve symbols within the 
vdso.
> > +        So we create a single entry list pointing to l_real as its 
only
> > +        element */
> > + 
> > +     l->l_local_scope[0]->r_nlist = 1;
> > +     l->l_local_scope[0]->r_list = &l->l_real;
> 
> They is this needed?
> 
Yes. Otherwise do_lookup_x segfaults at statement:

45            map = list[i]->l_real;

> 
> > diff -urN libc24-cvstip-20050427/sysdeps/powerpc/elf/libc-start.c 
> libc24/sysdeps/powerpc/elf/libc-start.c
> > --- libc24-cvstip-20050427/sysdeps/powerpc/elf/libc-start.c 
> 2004-04-03 19:06:07.000000000 -0600
> > +++ libc24/sysdeps/powerpc/elf/libc-start.c   2005-04-29 15:48:44.
> 000000000 -0500
> > @@ -18,6 +18,7 @@
> >  [...]
> > +#ifdef SHARED
> > +#undef __gettimeofday
> > +#include <bits/libc-vdso.h>
> > +
> > +__typeof (__gettimeofday) *__vdso_gettimeofday attribute_hidden;
> > +
> > +#if __WORDSIZE == 64
> > +typedef struct
> > +   {
> > +      void   *func;
> > +      void   *toc_ptr;
> > +      void   *extra;
> > +   } _ppc_func_desciptor;
> > + 
> > +static struct
> > +   {
> > +      _ppc_func_desciptor   fd_gettimeofday;
> > +   } __vdso_descriptor;
> > +#endif
> 
> That's ppc/linux specific and doesn't have any business being in this 
file.
> 
Yes but sysdeps/powerpc/elf/libc-start.c is a powerpc specific file. :)

> > --- libc24-cvstip-20050427/sysdeps/unix/sysv/linux/Makefile 
> 2004-10-04 18:29:06.000000000 -0500
> > +++ libc24/sysdeps/unix/sysv/linux/Makefile   2005-04-28 16:32:00.
> 000000000 -0500
> > @@ -142,6 +142,7 @@
> > 
> >  ifeq ($(subdir),elf)
> >  sysdep-rtld-routines += dl-brk dl-sbrk
> > +routines += dl-vdso
> 
> Once again, wrong file.
> 
Unless we can agree that resolving symbols in VDSO is a common GLIBC/Linux 
issue and should have a common GLIBC/Linux solution.

Steven J. Munroe
Linux on Power Toolchain Architect
IBM Corporation, Linux Technology Center