about summary refs log tree commit diff
path: root/sysdeps/generic/segfault.c
blob: 24ed3f8308a4b640c0f536591473ffaa4ca87839 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
/* Catch segmentation faults and print backtrace.
   Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <ctype.h>
#include <execinfo.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdio-common/_itoa.h>

#include <bp-checks.h>

/* Get the definition of "struct layout".  */
#include <frame.h>

/* This file defines macros to access the content of the sigcontext element
   passed up by the signal handler.  */
#include <sigcontextinfo.h>

/* Get code to possibly dump the content of all registers.  */
#include <register-dump.h>

/* This is a global variable set at program start time.  It marks the
   highest used stack address.  */
extern void *__libc_stack_end;


/* This implementation assumes a stack layout that matches the defaults
   used by gcc's `__builtin_frame_address' and `__builtin_return_address'
   (FP is the frame pointer register):

	  +-----------------+     +-----------------+
    FP -> | previous FP --------> | previous FP ------>...
	  |                 |     |                 |
	  | return address  |     | return address  |
	  +-----------------+     +-----------------+

  */

/* Get some notion of the current stack.  Need not be exactly the top
   of the stack, just something somewhere in the current frame.  */
#ifndef CURRENT_STACK_FRAME
# define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
#endif

/* By default we assume that the stack grows downward.  */
#ifndef INNER_THAN
# define INNER_THAN <
#endif

/* By default assume the `next' pointer in struct layout points to the
   next struct layout.  */
#ifndef ADVANCE_STACK_FRAME
# define ADVANCE_STACK_FRAME(next) BOUNDED_1 ((struct layout *) (next))
#endif

/* We'll use tis a lot.  */
#define WRITE_STRING(s) write (fd, s, strlen (s))

/* Name of the output file.  */
static const char *fname;


/* We better should not use `strerror' since it can call far too many
   other functions which might fail.  Do it here ourselves.  */
static void
write_strsignal (int fd, int signal)
{
  if (signal < 0 || signal >= _NSIG || _sys_siglist[signal] == NULL)
    {
      char buf[30];
      char *ptr = _itoa_word (signal, &buf[sizeof (buf)], 10, 0);
      WRITE_STRING ("signal ");
      write (fd, buf, &buf[sizeof (buf)] - ptr);
    }
  else
    WRITE_STRING (_sys_siglist[signal]);
}


/* This function is called when a segmentation fault is caught.  The system
   is in an instable state now.  This means especially that malloc() might
   not work anymore.  */
static void
catch_segfault (int signal, SIGCONTEXT ctx)
{
  struct layout *current;
  void *__unbounded top_frame;
  void *__unbounded top_stack;
  int fd;
  void **arr;
  size_t cnt;
  struct sigaction sa;

  /* This is the name of the file we are writing to.  If none is given
     or we cannot write to this file write to stderr.  */
  fd = 2;
  if (fname != NULL)
    {
      fd = open (fname, O_TRUNC | O_WRONLY | O_CREAT, 0666);
      if (fd == -1)
	fd = 2;
    }

  WRITE_STRING ("*** ");
  write_strsignal (fd, signal);
  WRITE_STRING ("\n");

#ifdef REGISTER_DUMP
  REGISTER_DUMP;
#endif

  WRITE_STRING ("\nBacktrace:\n");

  top_frame = GET_FRAME (ctx);
  top_stack = GET_STACK (ctx);

  /* First count how many entries we'll have.  */
  cnt = 1;
  current = BOUNDED_1 ((struct layout *) top_frame);
  while (!((void *) current INNER_THAN top_stack
	   || !((void *) current INNER_THAN __libc_stack_end)))
    {
      ++cnt;

      current = ADVANCE_STACK_FRAME (current->next);
    }

  arr = alloca (cnt * sizeof (void *));

  /* First handle the program counter from the structure.  */
  arr[0] = GET_PC (ctx);

  current = BOUNDED_1 ((struct layout *) top_frame);
  cnt = 1;
  while (!((void *) current INNER_THAN top_stack
	   || !((void *) current INNER_THAN __libc_stack_end)))
    {
      arr[cnt++] = current->return_address;

      current = ADVANCE_STACK_FRAME (current->next);
    }

  /* If the last return address was NULL, assume that it doesn't count.  */
  if (arr[cnt-1] == NULL)
    cnt--;

  /* Now generate nicely formatted output.  */
  __backtrace_symbols_fd (arr, cnt, fd);

  /* Pass on the signal (so that a core file is produced).  */
  sa.sa_handler = SIG_DFL;
  sigemptyset (&sa.sa_mask);
  sa.sa_flags = 0;
  sigaction (signal, &sa, NULL);
  raise (signal);
}


static void
__attribute__ ((constructor))
install_handler (void)
{
  struct sigaction sa;
  const char *sigs = getenv ("SEGFAULT_SIGNALS");
  const char *name;

  sa.sa_handler = (void *) catch_segfault;
  sigemptyset (&sa.sa_mask);
  sa.sa_flags = SA_RESTART;

  /* Maybe we are expected to use an alternative stack.  */
  if (getenv ("SEGFAULT_USE_ALTSTACK") != 0)
    {
      void *stack_mem = malloc (2 * SIGSTKSZ);
      struct sigaltstack ss;

      if (stack_mem != NULL)
	{
	  ss.ss_sp = stack_mem;
	  ss.ss_flags = 0;
	  ss.ss_size = 2 * SIGSTKSZ;

	  if (sigaltstack (&ss, NULL) == 0)
	    sa.sa_flags |= SA_ONSTACK;
	}
    }

  if (sigs == NULL)
    sigaction (SIGSEGV, &sa, NULL);
  else if (sigs[0] == '\0')
    /* Do not do anything.  */
    return;
  else
    {
      const char *where;
      int all = __strcasecmp (sigs, "all") == 0;

#define INSTALL_FOR_SIG(sig, name) \
      where = __strcasestr (sigs, name);				      \
      if (all || (where != NULL						      \
		  && (where == sigs || !isalnum (where[-1]))		      \
		  && !isalnum (where[sizeof (name) - 1])))		      \
	sigaction (sig, &sa, NULL);

      INSTALL_FOR_SIG (SIGSEGV, "segv");
      INSTALL_FOR_SIG (SIGILL, "ill");
#ifdef SIGBUS
      INSTALL_FOR_SIG (SIGBUS, "bus");
#endif
#ifdef SIGSTKFLT
      INSTALL_FOR_SIG (SIGSTKFLT, "stkflt");
#endif
      INSTALL_FOR_SIG (SIGABRT, "abrt");
      INSTALL_FOR_SIG (SIGFPE, "fpe");
    }

  /* Preserve the output file name if there is any given.  */
  name = getenv ("SEGFAULT_OUTPUT_NAME");
  if (name != NULL && name[0] != '\0')
    fname = __strdup (name);
}