1/* fileline.c -- Get file and line number information in a backtrace.
2   Copyright (C) 2012-2016 Free Software Foundation, Inc.
3   Written by Ian Lance Taylor, Google.
4
5Redistribution and use in source and binary forms, with or without
6modification, are permitted provided that the following conditions are
7met:
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
21THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
23WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
24DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
25INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
26(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
27SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
29STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
30IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
31POSSIBILITY OF SUCH DAMAGE.  */
32
33#include "config.h"
34
35#include <sys/types.h>
36#include <sys/stat.h>
37#include <errno.h>
38#include <fcntl.h>
39#include <stdlib.h>
40
41#include "backtrace.h"
42#include "internal.h"
43
44#ifndef HAVE_GETEXECNAME
45#define getexecname() NULL
46#endif
47
48/* Initialize the fileline information from the executable.  Returns 1
49   on success, 0 on failure.  */
50
51static int
52fileline_initialize (struct backtrace_state *state,
53		     backtrace_error_callback error_callback, void *data)
54{
55  int failed;
56  fileline fileline_fn;
57  int pass;
58  int called_error_callback;
59  int descriptor;
60
61  if (!state->threaded)
62    failed = state->fileline_initialization_failed;
63  else
64    failed = backtrace_atomic_load_int (&state->fileline_initialization_failed);
65
66  if (failed)
67    {
68      error_callback (data, "failed to read executable information", -1);
69      return 0;
70    }
71
72  if (!state->threaded)
73    fileline_fn = state->fileline_fn;
74  else
75    fileline_fn = backtrace_atomic_load_pointer (&state->fileline_fn);
76  if (fileline_fn != NULL)
77    return 1;
78
79  /* We have not initialized the information.  Do it now.  */
80
81  descriptor = -1;
82  called_error_callback = 0;
83  for (pass = 0; pass < 4; ++pass)
84    {
85      const char *filename;
86      int does_not_exist;
87
88      switch (pass)
89	{
90	case 0:
91	  filename = state->filename;
92	  break;
93	case 1:
94	  filename = getexecname ();
95	  break;
96	case 2:
97	  filename = "/proc/self/exe";
98	  break;
99	case 3:
100	  filename = "/proc/curproc/file";
101	  break;
102	default:
103	  abort ();
104	}
105
106      if (filename == NULL)
107	continue;
108
109      descriptor = backtrace_open (filename, error_callback, data,
110				   &does_not_exist);
111      if (descriptor < 0 && !does_not_exist)
112	{
113	  called_error_callback = 1;
114	  break;
115	}
116      if (descriptor >= 0)
117	break;
118    }
119
120  if (descriptor < 0)
121    {
122      if (!called_error_callback)
123	{
124	  if (state->filename != NULL)
125	    error_callback (data, state->filename, ENOENT);
126	  else
127	    error_callback (data,
128			    "libbacktrace could not find executable to open",
129			    0);
130	}
131      failed = 1;
132    }
133
134  if (!failed)
135    {
136      if (!backtrace_initialize (state, descriptor, error_callback, data,
137				 &fileline_fn))
138	failed = 1;
139    }
140
141  if (failed)
142    {
143      if (!state->threaded)
144	state->fileline_initialization_failed = 1;
145      else
146	backtrace_atomic_store_int (&state->fileline_initialization_failed, 1);
147      return 0;
148    }
149
150  if (!state->threaded)
151    state->fileline_fn = fileline_fn;
152  else
153    {
154      backtrace_atomic_store_pointer (&state->fileline_fn, fileline_fn);
155
156      /* Note that if two threads initialize at once, one of the data
157	 sets may be leaked.  */
158    }
159
160  return 1;
161}
162
163/* Given a PC, find the file name, line number, and function name.
164   N.B. The result is not necessarily useful. It will be zero if
165   fileline_initialize fails, but it will also be zero if everything
166   succeeds and CALLBACK returns 0 (which is intended behavior for
167   CALLBACK: see backtrace.h:backtrace_full_callback).  */
168
169int
170backtrace_pcinfo (struct backtrace_state *state, uintptr_t pc,
171		  backtrace_full_callback callback,
172		  backtrace_error_callback error_callback, void *data)
173{
174  if (!fileline_initialize (state, error_callback, data))
175    return 0;
176
177  if (state->fileline_initialization_failed)
178    return 0;
179
180  return state->fileline_fn (state, pc, callback, error_callback, data);
181}
182
183/* Given a PC, find the symbol for it, and its value.
184   Returns non-zero on success, zero on failure.
185   N.B. If the result is "success" error_callback may still have been called.
186   Plus if the result is "success", a symbol may not have been found.
187   CALLBACK will be called with NULL parameter values if a symbol isn't found.
188   It is up to the caller to handle all of this appropriately.  */
189
190int
191backtrace_syminfo (struct backtrace_state *state, uintptr_t pc,
192		   backtrace_syminfo_callback callback,
193		   backtrace_error_callback error_callback, void *data)
194{
195  if (!fileline_initialize (state, error_callback, data))
196    return 0;
197
198  if (state->fileline_initialization_failed)
199    return 0;
200
201  state->syminfo_fn (state, pc, callback, error_callback, data);
202  return 1;
203}
204