sysdeps/s390/s390-32/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 2000-2014 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <bits/libc-lock.h>
  21 #include <dlfcn.h>
  22 #include <execinfo.h>
  23 #include <stddef.h>
  24 #include <stdlib.h>
  25 #include <unwind.h>
  26
  27 /* This is a global variable set at program start time.  It marks the
  28    highest used stack address.  */
  29 extern void *__libc_stack_end;
  30
  31
  32 /* This is the stack layout we see for every non-leaf function.
  33            size                    offset
  34     %r15 ->    +------------------+
  35              4 | back chain       |  0
  36              4 | end of stack     |  4
  37              8 | glue             |  8
  38              8 | scratch          | 16
  39             40 | save area r6-r15 | 24
  40             16 | save area f4,f6  | 64
  41             16 | empty            | 80
  42                +------------------+
  43    r14 in the save area holds the return address.
  44 */
  45
  46 struct layout
  47 {
  48   int back_chain;
  49   int end_of_stack;
  50   int glue[2];
  51   int scratch[2];
  52   int save_grps[10];
  53   int save_fp[4];
  54   int empty[2];
  55 };
  56
  57 struct trace_arg
  58 {
  59   void **array;
  60   int cnt, size;
  61 };
  62
  63 #ifdef SHARED
  64 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
  65 static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
  66
  67 static void
  68 init (void)
  69 {
  70   void *handle = __libc_dlopen ("libgcc_s.so.1");
  71
  72   if (handle == NULL)
  73     return;
  74
  75   unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
  76   unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");
  77   if (unwind_getip == NULL)
  78     unwind_backtrace = NULL;
  79 }
  80
  81 static int
  82 __backchain_backtrace (void **array, int size)
  83 {
  84   /* We assume that all the code is generated with frame pointers set.  */
  85   struct layout *stack;
  86   int cnt = 0;
  87
  88   asm ("LR  %0,%%r15" : "=d" (stack) );
  89   /* We skip the call to this function, it makes no sense to record it.  */
  90   stack = (struct layout *) stack->back_chain;
  91   while (cnt < size)
  92     {
  93       if (stack == NULL || (void *) stack > __libc_stack_end)
  94         /* This means the address is out of range.  Note that for the
  95            toplevel we see a frame pointer with value NULL which clearly is
  96            out of range.  */
  97         break;
  98
  99       array[cnt++] = (void *) (stack->save_grps[8] & 0x7fffffff);
 100
 101       stack = (struct layout *) stack->back_chain;
 102     }
 103
 104   return cnt;
 105 }
 106 #else
 107 # define unwind_backtrace _Unwind_Backtrace
 108 # define unwind_getip _Unwind_GetIP
 109 #endif
 110
 111 static _Unwind_Reason_Code
 112 backtrace_helper (struct _Unwind_Context *ctx, void *a)
 113 {
 114   struct trace_arg *arg = a;
 115
 116   /* We are first called with address in the __backtrace function.
 117      Skip it.  */
 118   if (arg->cnt != -1)
 119     arg->array[arg->cnt] = (void *) unwind_getip (ctx);
 120   if (++arg->cnt == arg->size)
 121     return _URC_END_OF_STACK;
 122   return _URC_NO_REASON;
 123 }
 124
 125 int
 126 __backtrace (void **array, int size)
 127 {
 128   struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
 129 #ifdef SHARED
 130   __libc_once_define (static, once);
 131
 132   __libc_once (once, init);
 133
 134   if (unwind_backtrace == NULL)
 135     return __backchain_backtrace (array, size);
 136 #endif
 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)