sysdeps/arm/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 2008-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Kazu Hirata <kazu@codesourcery.com>, 2008.
   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 <libc-lock.h>
  21 #include <dlfcn.h>
  22 #include <execinfo.h>
  23 #include <stdlib.h>
  24 #include <unwind.h>
  25
  26 struct trace_arg
  27 {
  28   void **array;
  29   int cnt, size;
  30 };
  31
  32 #ifdef SHARED
  33 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
  34 static _Unwind_VRS_Result (*unwind_vrs_get) (_Unwind_Context *,
  35                                              _Unwind_VRS_RegClass,
  36                                              _uw,
  37                                              _Unwind_VRS_DataRepresentation,
  38                                              void *);
  39
  40 static void *libgcc_handle;
  41
  42 static void
  43 init (void)
  44 {
  45   libgcc_handle = __libc_dlopen ("libgcc_s.so.1");
  46
  47   if (libgcc_handle == NULL)
  48     return;
  49
  50   unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
  51   unwind_vrs_get = __libc_dlsym (libgcc_handle, "_Unwind_VRS_Get");
  52   if (unwind_vrs_get == NULL)
  53     unwind_backtrace = NULL;
  54 }
  55
  56 /* This function is identical to "_Unwind_GetGR", except that it uses
  57    "unwind_vrs_get" instead of "_Unwind_VRS_Get".  */
  58 static inline _Unwind_Word
  59 unwind_getgr (_Unwind_Context *context, int regno)
  60 {
  61   _uw val;
  62   unwind_vrs_get (context, _UVRSC_CORE, regno, _UVRSD_UINT32, &val);
  63   return val;
  64 }
  65
  66 /* This macro is identical to the _Unwind_GetIP macro, except that it
  67    uses "unwind_getgr" instead of "_Unwind_GetGR".  */
  68 # define unwind_getip(context) \
  69   (unwind_getgr (context, 15) & ~(_Unwind_Word)1)
  70 #else
  71 # define unwind_backtrace _Unwind_Backtrace
  72 # define unwind_getip _Unwind_GetIP
  73 #endif
  74
  75 static _Unwind_Reason_Code
  76 backtrace_helper (struct _Unwind_Context *ctx, void *a)
  77 {
  78   struct trace_arg *arg = a;
  79
  80   /* We are first called with address in the __backtrace function.
  81      Skip it.  */
  82   if (arg->cnt != -1)
  83     arg->array[arg->cnt] = (void *) unwind_getip (ctx);
  84   if (++arg->cnt == arg->size)
  85     return _URC_END_OF_STACK;
  86   return _URC_NO_REASON;
  87 }
  88
  89 int
  90 __backtrace (void **array, int size)
  91 {
  92   struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
  93
  94   if (size <= 0)
  95     return 0;
  96
  97 #ifdef SHARED
  98   __libc_once_define (static, once);
  99
 100   __libc_once (once, init);
 101   if (unwind_backtrace == NULL)
 102     return 0;
 103 #endif
 104
 105   unwind_backtrace (backtrace_helper, &arg);
 106
 107   if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
 108     --arg.cnt;
 109   return arg.cnt != -1 ? arg.cnt : 0;
 110 }
 111 weak_alias (__backtrace, backtrace)
 112 libc_hidden_def (__backtrace)
 113
 114
 115 #ifdef SHARED
 116 /* Free all resources if necessary.  */
 117 libc_freeres_fn (free_mem)
 118 {
 119   unwind_backtrace = NULL;
 120   if (libgcc_handle != NULL)
 121     {
 122       __libc_dlclose (libgcc_handle);
 123       libgcc_handle = NULL;
 124     }
 125 }
 126 #endif