libbacktrace/fileline.c

   1 /* fileline.c -- Get file and line number information in a backtrace.
   2    Copyright (C) 2012 Free Software Foundation, Inc.
   3    Written by Ian Lance Taylor, Google.
   4
   5 Redistribution and use in source and binary forms, with or without
   6 modification, are permitted provided that the following conditions are
   7 met:
   8
   9     (1) Redistributions of source code must retain the above copyright
  10     notice, this list of conditions and the following disclaimer.
  11
  12     (2) Redistributions in binary form must reproduce the above copyright
  13     notice, this list of conditions and the following disclaimer in
  14     the documentation and/or other materials provided with the
  15     distribution.
  16
  17     (3) The name of the author may not be used to
  18     endorse or promote products derived from this software without
  19     specific prior written permission.
  20
  21 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  22 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  23 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  24 DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  25 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  26 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  27 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  29 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  30 IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31 POSSIBILITY OF SUCH DAMAGE.  */
  32
  33 #include "config.h"
  34
  35 #include <sys/types.h>
  36 #include <sys/stat.h>
  37 #include <fcntl.h>
  38 #include <stdlib.h>
  39
  40 #include "backtrace.h"
  41 #include "internal.h"
  42
  43 /* Initialize the fileline information from the executable.  Returns 1
  44    on success, 0 on failure.  */
  45
  46 static int
  47 fileline_initialize (struct backtrace_state *state,
  48                      backtrace_error_callback error_callback, void *data)
  49 {
  50   int failed;
  51   fileline fileline_fn;
  52   int descriptor;
  53
  54   failed = state->fileline_initialization_failed;
  55
  56   if (state->threaded)
  57     {
  58       /* Use __sync_bool_compare_and_swap to do an atomic load.  */
  59       while (!__sync_bool_compare_and_swap
  60              (&state->fileline_initialization_failed, failed, failed))
  61         failed = state->fileline_initialization_failed;
  62     }
  63
  64   if (failed)
  65     {
  66       error_callback (data, "failed to read executable information", -1);
  67       return 0;
  68     }
  69
  70   fileline_fn = state->fileline_fn;
  71   if (state->threaded)
  72     {
  73       while (!__sync_bool_compare_and_swap (&state->fileline_fn, fileline_fn,
  74                                             fileline_fn))
  75         fileline_fn = state->fileline_fn;
  76     }
  77   if (fileline_fn != NULL)
  78     return 1;
  79
  80   /* We have not initialized the information.  Do it now.  */
  81
  82   if (state->filename != NULL)
  83     descriptor = backtrace_open (state->filename, error_callback, data, NULL);
  84   else
  85     descriptor = backtrace_open ("/proc/self/exe", error_callback, data, NULL);
  86   if (descriptor < 0)
  87     failed = 1;
  88
  89   if (!failed)
  90     {
  91       if (!backtrace_initialize (state, descriptor, error_callback, data,
  92                                  &fileline_fn))
  93         failed = 1;
  94     }
  95
  96   if (failed)
  97     {
  98       if (!state->threaded)
  99         state->fileline_initialization_failed = 1;
 100       else
 101         __sync_bool_compare_and_swap (&state->fileline_initialization_failed,
 102                                       0, failed);
 103       return 0;
 104     }
 105
 106   if (!state->threaded)
 107     state->fileline_fn = fileline_fn;
 108   else
 109     {
 110       __sync_bool_compare_and_swap (&state->fileline_fn, NULL, fileline_fn);
 111
 112       /* At this point we know that state->fileline_fn is not NULL.
 113          Either we stored our value, or some other thread stored its
 114          value.  If some other thread stored its value, we leak the
 115          one we just initialized.  Either way, state->fileline_fn is
 116          initialized.  The compare_and_swap is a full memory barrier,
 117          so we should have full access to that value even if it was
 118          created by another thread.  */
 119     }
 120
 121   return 1;
 122 }
 123
 124 /* Given a PC, find the file name, line number, and function name.  */
 125
 126 int
 127 backtrace_pcinfo (struct backtrace_state *state, uintptr_t pc,
 128                   backtrace_full_callback callback,
 129                   backtrace_error_callback error_callback, void *data)
 130 {
 131   if (!fileline_initialize (state, error_callback, data))
 132     return 0;
 133
 134   if (state->fileline_initialization_failed)
 135     return 0;
 136
 137   return state->fileline_fn (state, pc, callback, error_callback, data);
 138 }
 139
 140 /* Given a PC, find the symbol for it, and its value.  */
 141
 142 int
 143 backtrace_syminfo (struct backtrace_state *state, uintptr_t pc,
 144                    backtrace_syminfo_callback callback,
 145                    backtrace_error_callback error_callback, void *data)
 146 {
 147   if (!fileline_initialize (state, error_callback, data))
 148     return 0;
 149
 150   if (state->fileline_initialization_failed)
 151     return 0;
 152
 153   state->syminfo_fn (state, pc, callback, error_callback, data);
 154   return 1;
 155 }