sysdeps/s390/s390-32/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 2000, 2001, 2003, 2004, 2005 Free Software Foundation, Inc.
   3    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the 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    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <bits/libc-lock.h>
  22 #include <dlfcn.h>
  23 #include <execinfo.h>
  24 #include <stddef.h>
  25 #include <stdlib.h>
  26 #include <unwind.h>
  27
  28 /* This is a global variable set at program start time.  It marks the
  29    highest used stack address.  */
  30 extern void *__libc_stack_end;
  31
  32
  33 /* This is the stack layout we see for every non-leaf function.
  34            size                    offset
  35     %r15 ->    +------------------+
  36              4 | back chain       |  0
  37              4 | end of stack     |  4
  38              8 | glue             |  8
  39              8 | scratch          | 16
  40             40 | save area r6-r15 | 24
  41             16 | save area f4,f6  | 64
  42             16 | empty            | 80
  43                +------------------+
  44    r14 in the save area holds the return address.
  45 */
  46
  47 struct layout
  48 {
  49   int back_chain;
  50   int end_of_stack;
  51   int glue[2];
  52   int scratch[2];
  53   int save_grps[10];
  54   int save_fp[4];
  55   int empty[2];
  56 };
  57
  58 struct trace_arg
  59 {
  60   void **array;
  61   int cnt, size;
  62 };
  63
  64 #ifdef SHARED
  65 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
  66 static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
  67
  68 static void
  69 init (void)
  70 {
  71   void *handle = __libc_dlopen ("libgcc_s.so.1");
  72
  73   if (handle == NULL)
  74     return;
  75
  76   unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
  77   unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");
  78   if (unwind_getip == NULL)
  79     unwind_backtrace = NULL;
  80 }
  81 #else
  82 # define unwind_backtrace _Unwind_Backtrace
  83 # define unwind_getip _Unwind_GetIP
  84 #endif
  85
  86 static int
  87 __backchain_backtrace (void **array, int size)
  88 {
  89   /* We assume that all the code is generated with frame pointers set.  */
  90   struct layout *stack;
  91   int cnt = 0;
  92
  93   asm ("LR  %0,%%r15" : "=d" (stack) );
  94   /* We skip the call to this function, it makes no sense to record it.  */
  95   stack = (struct layout *) stack->back_chain;
  96   while (cnt < size)
  97     {
  98       if (stack == NULL || (void *) stack > __libc_stack_end)
  99         /* This means the address is out of range.  Note that for the
 100            toplevel we see a frame pointer with value NULL which clearly is
 101            out of range.  */
 102         break;
 103
 104       array[cnt++] = (void *) (stack->save_grps[8] & 0x7fffffff);
 105
 106       stack = (struct layout *) stack->back_chain;
 107     }
 108
 109   return cnt;
 110 }
 111
 112 static _Unwind_Reason_Code
 113 backtrace_helper (struct _Unwind_Context *ctx, void *a)
 114 {
 115   struct trace_arg *arg = a;
 116
 117   /* We are first called with address in the __backtrace function.
 118      Skip it.  */
 119   if (arg->cnt != -1)
 120     arg->array[arg->cnt] = (void *) unwind_getip (ctx);
 121   if (++arg->cnt == arg->size)
 122     return _URC_END_OF_STACK;
 123   return _URC_NO_REASON;
 124 }
 125
 126 int
 127 __backtrace (void **array, int size)
 128 {
 129   struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
 130 #ifdef SHARED
 131   __libc_once_define (static, once);
 132
 133   __libc_once (once, init);
 134 #endif
 135   if (unwind_backtrace == NULL)
 136     return __backchain_backtrace (array, size);
 137
 138   if (size >= 1)
 139     unwind_backtrace (backtrace_helper, &arg);
 140
 141   return arg.cnt != -1 ? arg.cnt : 0;
 142 }
 143
 144 weak_alias (__backtrace, backtrace)
 145 libc_hidden_def (__backtrace)