sysdeps/powerpc/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 1998 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <execinfo.h>
  21
  22 /* This is the stack layout we see with every stack frame.
  23    Note that every routine is required by the ABI to lay out the stack
  24    like this.
  25
  26             +----------------+        +-----------------+
  27     %r1  -> | %r1 last frame--------> | %r1 last frame--->...  --> NULL
  28             |                |        |                 |
  29             | (unused)       |        | return address  |
  30             +----------------+        +-----------------+
  31 */
  32 struct layout
  33 {
  34   struct layout *next;
  35   void *return_address;
  36 };
  37
  38 int
  39 __backtrace (void **array, int size)
  40 {
  41   struct layout *current;
  42   int count;
  43
  44   /* Force gcc to spill LR.  */
  45   asm volatile ("" : "=l"(current));
  46
  47   /* Get the address on top-of-stack.  */
  48   asm volatile ("lwz %0,0(1)" : "=r"(current));
  49
  50   for (                         count = 0;
  51        current != NULL &&       count < size;
  52        current = current->next, count++)
  53     array[count] = current->return_address;
  54
  55   /* It's possible the second-last stack frame can't return
  56      (that is, it's __libc_start_main), in which case
  57      the CRT startup code will have set its LR to 'NULL'.  */
  58   if (count > 0 && array[count-1] == NULL)
  59     count--;
  60
  61   return count;
  62 }
  63 weak_alias (__backtrace, backtrace)