Re: [PATCH,HURD] Fix value of __libc_stack_end

[Aurelien Jarno]

On Thu, Aug 25, 2011 at 12:22:44AM +0200, Samuel Thibault wrote:
> When using some libthread, we need to update the value of __libc_stack_end
> to what the libthread allocated. This requires making __libc_stack_end
> non-relro to be able to modify it.
> 
> Samuel
> 
> 2011-08-24  Samuel Thibault  <samuel.thibault@ens-lyon.org>
> 
> * sysdeps/generic/ldsodefs.h [LIBC_STACK_END_NOT_RELRO] (__libc_stack_end): Do
> not use attribute_relro.
> * sysdeps/mach/hurd/dl-sysdep.h (LIBC_STACK_END_NOT_RELRO): Define.
> * sysdeps/mach/hurd/i386/init-first.c (init): Update __libc_stack_end to
> libthread-provided value.
> * sysdeps/mach/hurd/dl-sysdep.c (__libc_stack_end): Do not use 
> attribute_relro.
> 
> ---
>  generic/ldsodefs.h          |    6 +++++-
>  mach/hurd/dl-sysdep.c       |    2 +-
>  mach/hurd/dl-sysdep.h       |    3 ++-
>  mach/hurd/i386/init-first.c |    2 ++
>  4 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
> index d040590..cb24ca7 100644
> --- a/sysdeps/generic/ldsodefs.h
> +++ b/sysdeps/generic/ldsodefs.h
> @@ -723,7 +723,11 @@ rtld_hidden_proto (_dl_make_stack_executable)
>     might use the variable which results in copy relocations on some
>     platforms.  But this does not matter, ld.so can always use the local
>     copy.  */
> -extern void *__libc_stack_end attribute_relro;
> +extern void *__libc_stack_end
> +#ifndef LIBC_STACK_END_NOT_RELRO
> +     attribute_relro
> +#endif
> +     ;
>  rtld_hidden_proto (__libc_stack_end)
>  
>  /* Parameters passed to the dynamic linker.  */
> diff --git a/sysdeps/mach/hurd/dl-sysdep.h b/sysdeps/mach/hurd/dl-sysdep.h
> index 4b21b77..8f1c728 100644
> --- a/sysdeps/mach/hurd/dl-sysdep.h
> +++ b/sysdeps/mach/hurd/dl-sysdep.h
> @@ -25,7 +25,8 @@
>  #define RTLD_PRIVATE_ERRNO 0
>  
>  #ifdef SHARED
> -/* _dl_argv cannot be attribute_relro, because the stack-switching
> +/* _dl_argv and __libc_stack_end cannot be attribute_relro, because the 
> stack-switching
>     libc initializer for using cthreads might write into it.  */
>  # define DL_ARGV_NOT_RELRO 1
> +# define LIBC_STACK_END_NOT_RELRO 1
>  #endif
> diff --git a/sysdeps/mach/hurd/i386/init-first.c 
> b/sysdeps/mach/hurd/i386/init-first.c
> index e79af1d..7b2ea12 100644
> --- a/sysdeps/mach/hurd/i386/init-first.c
> +++ b/sysdeps/mach/hurd/i386/init-first.c
> @@ -227,6 +224,8 @@ init (int *_data)
>  
>        void switch_stacks (void);
>  
> +      __libc_stack_end = newsp;
> +
>        /* Copy per-thread variables from that temporary
>        area onto the new cthread stack.  */
>        memcpy (__hurd_threadvar_location_from_sp (0, newsp),
> diff --git a/sysdeps/mach/hurd/dl-sysdep.c b/sysdeps/mach/hurd/dl-sysdep.c
> index a63151f..a5df5c1 100644
> --- a/sysdeps/mach/hurd/dl-sysdep.c
> +++ b/sysdeps/mach/hurd/dl-sysdep.c
> @@ -55,7 +55,7 @@ INTVARDEF(__libc_enable_secure)
>  int __libc_multiple_libcs = 0;       /* Defining this here avoids the 
> inclusion
>                                  of init-first.  */
>  /* This variable containts the lowest stack address ever used.  */
> -void *__libc_stack_end attribute_relro = NULL;
> +void *__libc_stack_end = NULL;
>  rtld_hidden_data_def(__libc_stack_end)
>  void *_dl_random attribute_relro = NULL; /* TODO */
>  

This last hunk doesn't apply. The current git code has:

| /* This variable containts the lowest stack address ever used.  */
| void *__libc_stack_end;

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net