[PATCH/RFC] auxv entries

[Mark Kettenis <mark dot kettenis at xs4all dot nl>]

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 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;