Re: [PATCH/RFC] auxv entries

[Thiago Jung Bauermann <bauerman@br.ibm.com>]

El dom, 14-09-2008 a las 23:27 +0200, Mark Kettenis escribió:
> Many, if not all, processor-specific ELF ABI documents have the
> following definition of auxv entries:
> 
> typedef struct
> {
>        int   a_type;
>        union {
>               long a_val;
>               void *a_ptr;
>               void (*a_fcn)();
>        } a_un;
> } auxv_t;

This is what I see in <elf.h> on ppc64-linux:


> 
> This is not the layout that default_auxv_parse() uses though, which is
> wrong for big-endian 64-bit systems.  The attached diff fixes this,
> making the assumption that a_val is "naturally" aligned.
> 
> I have some slight worries though about how this ever worked on
> big-endian 64-bit Linux systems, hence the RFC.
> 
> 
> Index: ChangeLog
> from  Mark Kettenis  <kettenis@gnu.org>
> 
> 	* auxv.c (default_auxv_parse): Change code to reflect standard
> 	auxv_t layout.
> 
> Index: auxv.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/auxv.c,v
> retrieving revision 1.14
> diff -u -p -r1.14 auxv.c
> --- auxv.c 11 Sep 2008 14:29:21 -0000 1.14
> +++ auxv.c 14 Sep 2008 21:20:03 -0000
> @@ -82,20 +82,22 @@ int
>  default_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
>  		   gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
>  {
> -  const int sizeof_auxv_field = gdbarch_ptr_bit (target_gdbarch)
> -				/ TARGET_CHAR_BIT;
> +  struct type *builtin_int = builtin_type (target_gdbarch)->builtin_int;
> +  struct type *builtin_long = builtin_type (target_gdbarch)->builtin_long;
> +  const int sizeof_auxv_type = TYPE_LENGTH(builtin_int);
> +  const int sizeof_auxv_val = TYPE_LENGTH(builtin_long);
>    gdb_byte *ptr = *readptr;
>  
>    if (endptr == ptr)
>      return 0;
>  
> -  if (endptr - ptr < sizeof_auxv_field * 2)
> +  if (endptr - ptr < sizeof_auxv_val * 2)
>      return -1;
>  
> -  *typep = extract_unsigned_integer (ptr, sizeof_auxv_field);
> -  ptr += sizeof_auxv_field;
> -  *valp = extract_unsigned_integer (ptr, sizeof_auxv_field);
> -  ptr += sizeof_auxv_field;
> +  *typep = extract_unsigned_integer (ptr, sizeof_auxv_type);
> +  ptr += sizeof_auxv_val;	/* Alignment.  */
> +  *valp = extract_unsigned_integer (ptr, sizeof_auxv_val);
> +  ptr += sizeof_auxv_val;
>  
>    *readptr = ptr;
>    return 1;
> 
-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center