sysdeps/generic/backtrace.c

   1 /* Return backtrace of current program state.  Generic version.
   2    Copyright (C) 1998 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <execinfo.h>
  22
  23
  24 /* This is a global variable set at program start time.  It marks the
  25    highest used stack address.  */
  26 extern void *__libc_stack_end;
  27
  28
  29 /* This implementation assumes a stack layout that matches the defaults
  30    used by gcc's `__builtin_frame_address' and `__builtin_return_address'
  31    (FP is the frame pointer register):
  32
  33           +-----------------+     +-----------------+
  34     FP -> | previous FP --------> | previous FP ------>...
  35           |                 |     |                 |
  36           | return address  |     | return address  |
  37           +-----------------+     +-----------------+
  38
  39   */
  40
  41 /* Get some notion of the current stack.  Need not be exactly the top
  42    of the stack, just something somewhere in the current frame.  */
  43 #ifndef CURRENT_STACK_FRAME
  44 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
  45 #endif
  46
  47 /* By default we assume that the stack grows downward.  */
  48 #ifndef INNER_THAN
  49 # define INNER_THAN <
  50 #endif
  51
  52 struct layout
  53 {
  54   struct layout *next;
  55   void *return_address;
  56 };
  57
  58 int
  59 __backtrace (array, size)
  60      void **array;
  61      int size;
  62 {
  63   struct layout *current;
  64   void *top_frame;
  65   void *top_stack;
  66   int cnt = 0;
  67
  68   top_frame = __builtin_frame_address (0);
  69   top_stack = CURRENT_STACK_FRAME;
  70
  71   /* We skip the call to this function, it makes no sense to record it.  */
  72   current = (struct layout *) top_frame;
  73   while (cnt < size)
  74     {
  75       if ((void *) current INNER_THAN top_stack
  76           || !((void *) current INNER_THAN __libc_stack_end))
  77        /* This means the address is out of range.  Note that for the
  78           toplevel we see a frame pointer with value NULL which clearly is
  79           out of range.  */
  80         break;
  81
  82       array[cnt++] = current->return_address;
  83
  84       current = current->next;
  85     }
  86
  87   return cnt;
  88 }
  89 weak_alias (__backtrace, backtrace)