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Re: [PATCH/RFC] auxv entries
- From: Thiago Jung Bauermann <bauerman at br dot ibm dot com>
- To: Mark Kettenis <mark dot kettenis at xs4all dot nl>
- Cc: gdb-patches at sourceware dot org
- Date: Sun, 14 Sep 2008 21:27:04 -0300
- Subject: Re: [PATCH/RFC] auxv entries
- References: <200809142127.m8ELR9eX025288@brahms.sibelius.xs4all.nl>
El dom, 14-09-2008 a las 23:27 +0200, Mark Kettenis escribiÃ:
> 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