sysdeps/s390/s390-64/backtrace.c

   1 /* Return backtrace of current program state.  64 bit S/390 version.
   2    Copyright (C) 2001-2015 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
  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              8 | back chain       |   0
  37              8 | end of stack     |   8
  38             32 | scratch          |  16
  39             80 | save area r6-r15 |  48
  40             16 | save area f4,f6  | 128
  41             16 | empty            | 144
  42                +------------------+
  43    r14 in the save area holds the return address.
  44 */
  45
  46 struct layout
  47 {
  48   long back_chain;
  49   long end_of_stack;
  50   long scratch[4];
  51   long save_grps[10];
  52   long save_fp[2];
  53   long empty[2];
  54 };
  55
  56 struct trace_arg
  57 {
  58   void **array;
  59   int cnt, size;
  60 };
  61
  62 #ifdef SHARED
  63 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
  64 static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
  65
  66 static void
  67 init (void)
  68 {
  69   void *handle = __libc_dlopen ("libgcc_s.so.1");
  70
  71   if (handle == NULL)
  72     return;
  73
  74   unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
  75   unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");
  76   if (unwind_getip == NULL)
  77     unwind_backtrace = NULL;
  78 }
  79
  80 static int
  81 __backchain_backtrace (void **array, int size)
  82 {
  83   /* We assume that all the code is generated with frame pointers set.  */
  84   struct layout *stack;
  85   int cnt = 0;
  86
  87   asm ("LGR  %0,%%r15" : "=d" (stack) );
  88   /* We skip the call to this function, it makes no sense to record it.  */
  89   stack = (struct layout *) stack->back_chain;
  90   while (cnt < size)
  91     {
  92       if (stack == NULL || (void *) stack > __libc_stack_end)
  93         /* This means the address is out of range.  Note that for the
  94            toplevel we see a frame pointer with value NULL which clearly is
  95            out of range.  */
  96         break;
  97
  98       array[cnt++] = (void *) stack->save_grps[8];
  99
 100       stack = (struct layout *) stack->back_chain;
 101     }
 102
 103   return cnt;
 104 }
 105 #else
 106 # define unwind_backtrace _Unwind_Backtrace
 107 # define unwind_getip _Unwind_GetIP
 108 #endif
 109
 110 static _Unwind_Reason_Code
 111 backtrace_helper (struct _Unwind_Context *ctx, void *a)
 112 {
 113   struct trace_arg *arg = a;
 114
 115   /* We are first called with address in the __backtrace function.
 116      Skip it.  */
 117   if (arg->cnt != -1)
 118     arg->array[arg->cnt] = (void *) unwind_getip (ctx);
 119   if (++arg->cnt == arg->size)
 120     return _URC_END_OF_STACK;
 121   return _URC_NO_REASON;
 122 }
 123
 124 int
 125 __backtrace (void **array, int size)
 126 {
 127   struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
 128 #ifdef SHARED
 129   __libc_once_define (static, once);
 130
 131   __libc_once (once, init);
 132
 133   if (unwind_backtrace == NULL)
 134     return __backchain_backtrace (array, size);
 135 #endif
 136
 137   if (size >= 1)
 138     unwind_backtrace (backtrace_helper, &arg);
 139
 140   return arg.cnt != -1 ? arg.cnt : 0;
 141 }
 142
 143 weak_alias (__backtrace, backtrace)
 144 libc_hidden_def (__backtrace)