sysdeps/sparc/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 2013-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by David S. Miller <davem@davemloft.net>
   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
  18    not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <execinfo.h>
  21 #include <stddef.h>
  22 #include <sysdep.h>
  23 #include <sys/trap.h>
  24 #include <dlfcn.h>
  25 #include <unwind.h>
  26 #include <backtrace.h>
  27
  28 struct layout
  29 {
  30   unsigned long locals[8];
  31   unsigned long ins[6];
  32   unsigned long next;
  33   void *return_address;
  34 };
  35
  36 struct trace_arg
  37 {
  38   void **array;
  39   _Unwind_Word cfa;
  40   int cnt;
  41   int size;
  42 };
  43
  44 #ifdef SHARED
  45 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
  46 static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
  47 static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *);
  48 static void *libgcc_handle;
  49
  50 /* Dummy version in case libgcc_s does not contain the real code.  */
  51 static _Unwind_Word
  52 dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused)))
  53 {
  54   return 0;
  55 }
  56
  57 static void
  58 init (void)
  59 {
  60   libgcc_handle = __libc_dlopen ("libgcc_s.so.1");
  61
  62   if (libgcc_handle == NULL)
  63     return;
  64
  65   unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
  66   unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
  67   if (unwind_getip == NULL)
  68     unwind_backtrace = NULL;
  69   unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")
  70                   ?: dummy_getcfa);
  71 }
  72 #else
  73 # define unwind_backtrace _Unwind_Backtrace
  74 # define unwind_getip _Unwind_GetIP
  75 # define unwind_getcfa _Unwind_GetCFA
  76 #endif
  77
  78 static _Unwind_Reason_Code
  79 backtrace_helper (struct _Unwind_Context *ctx, void *a)
  80 {
  81   struct trace_arg *arg = a;
  82   _Unwind_Ptr ip;
  83
  84   /* We are first called with address in the __backtrace function.
  85      Skip it.  */
  86   if (arg->cnt != -1)
  87     {
  88       ip = unwind_getip (ctx);
  89       arg->array[arg->cnt] = (void *) ip;
  90
  91       /* Check whether we make any progress.  */
  92       _Unwind_Word cfa = unwind_getcfa (ctx);
  93
  94       if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
  95          && cfa == arg->cfa)
  96        return _URC_END_OF_STACK;
  97       arg->cfa = cfa;
  98     }
  99   if (++arg->cnt == arg->size)
 100     return _URC_END_OF_STACK;
 101   return _URC_NO_REASON;
 102 }
 103
 104 int
 105 __backtrace (void **array, int size)
 106 {
 107   struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 };
 108   bool use_unwinder;
 109   int count;
 110
 111   if (!size)
 112     return 0;
 113
 114   use_unwinder = true;
 115 #ifdef SHARED
 116   __libc_once_define (static, once);
 117
 118   __libc_once (once, init);
 119   if (unwind_backtrace == NULL)
 120     use_unwinder = false;
 121 #endif
 122
 123   if (use_unwinder == false)
 124     {
 125       struct layout *current;
 126       unsigned long fp, i7;
 127
 128       asm volatile ("mov %%fp, %0" : "=r"(fp));
 129       asm volatile ("mov %%i7, %0" : "=r"(i7));
 130       current = (struct layout *) (fp + BACKTRACE_STACK_BIAS);
 131
 132       array[0] = (void *) i7;
 133
 134       if (size == 1)
 135         return 1;
 136
 137       backtrace_flush_register_windows();
 138       for (count = 1; count < size; count++)
 139         {
 140           array[count] = current->return_address;
 141           if (!current->next)
 142             break;
 143           current = (struct layout *) (current->next + BACKTRACE_STACK_BIAS);
 144         }
 145     }
 146   else
 147     {
 148       unwind_backtrace (backtrace_helper, &arg);
 149
 150       /* _Unwind_Backtrace seems to put NULL address above
 151          _start.  Fix it up here.  */
 152       if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
 153         --arg.cnt;
 154       count = arg.cnt != -1 ? arg.cnt : 0;
 155     }
 156   return count;
 157 }
 158 weak_alias (__backtrace, backtrace)
 159 libc_hidden_def (__backtrace)