libgfortran/runtime/backtrace.c

   1 /* Copyright (C) 2006, 2007, 2009, 2011 Free Software Foundation, Inc.
   2    Contributed by François-Xavier Coudert
   3
   4 This file is part of the GNU Fortran runtime library (libgfortran).
   5
   6 Libgfortran is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 3, or (at your option)
   9 any later version.
  10
  11 Libgfortran 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
  14 GNU General Public License for more details.
  15
  16 Under Section 7 of GPL version 3, you are granted additional
  17 permissions described in the GCC Runtime Library Exception, version
  18 3.1, as published by the Free Software Foundation.
  19
  20 You should have received a copy of the GNU General Public License and
  21 a copy of the GCC Runtime Library Exception along with this program;
  22 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 <http://www.gnu.org/licenses/>.  */
  24
  25 #include "libgfortran.h"
  26
  27 #include <string.h>
  28 #include <stdlib.h>
  29
  30 #ifdef HAVE_UNISTD_H
  31 #include <unistd.h>
  32 #endif
  33
  34 #ifdef HAVE_SYS_WAIT_H
  35 #include <sys/wait.h>
  36 #endif
  37
  38 #include <limits.h>
  39
  40 #include "unwind.h"
  41
  42
  43 /* Macros for common sets of capabilities: can we fork and exec, can
  44    we use glibc-style backtrace functions, and can we use pipes.  */
  45 #define CAN_FORK (defined(HAVE_FORK) && defined(HAVE_EXECVE) \
  46                   && defined(HAVE_WAIT))
  47 #define CAN_PIPE (CAN_FORK && defined(HAVE_PIPE) \
  48                   && defined(HAVE_DUP2) && defined(HAVE_FDOPEN) \
  49                   && defined(HAVE_CLOSE))
  50
  51 #ifndef PATH_MAX
  52 #define PATH_MAX 4096
  53 #endif
  54
  55
  56 /* GDB style #NUM index for each stack frame.  */
  57
  58 static void
  59 bt_header (int num)
  60 {
  61   st_printf ("#%d  ", num);
  62 }
  63
  64
  65 /* fgets()-like function that reads a line from a fd, without
  66    needing to malloc() a buffer, and does not use locks, hence should
  67    be async-signal-safe.  */
  68
  69 static char *
  70 fd_gets (char *s, int size, int fd)
  71 {
  72   for (int i = 0; i < size; i++)
  73     {
  74       char c;
  75       ssize_t nread = read (fd, &c, 1);
  76       if (nread == 1)
  77         {
  78           s[i] = c;
  79           if (c == '\n')
  80             {
  81               if (i + 1 < size)
  82                 s[i+1] = '\0';
  83               else
  84                 s[i] = '\0';
  85               break;
  86             }
  87         }
  88       else
  89         {
  90           s[i] = '\0';
  91           if (i == 0)
  92             return NULL;
  93           break;
  94         }
  95     }
  96   return s;
  97 }
  98
  99
 100 extern char *addr2line_path;
 101
 102 /* Struct containing backtrace state.  */
 103 typedef struct
 104 {
 105   int frame_number;
 106   int direct_output;
 107   int outfd;
 108   int infd;
 109   int error;
 110 }
 111 bt_state;
 112
 113 static _Unwind_Reason_Code
 114 trace_function (struct _Unwind_Context *context, void *state_ptr)
 115 {
 116   bt_state* state = (bt_state*) state_ptr;
 117   _Unwind_Ptr ip;
 118 #ifdef HAVE_GETIPINFO
 119   int ip_before_insn = 0;
 120   ip = _Unwind_GetIPInfo (context, &ip_before_insn);
 121
 122   /* If the unwinder gave us a 'return' address, roll it back a little
 123      to ensure we get the correct line number for the call itself.  */
 124   if (! ip_before_insn)
 125     --ip;
 126 #else
 127   ip = _Unwind_GetIP (context);
 128 #endif
 129
 130   if (state->direct_output)
 131     {
 132       bt_header(state->frame_number);
 133       st_printf ("%p\n", (void*) ip);
 134     }
 135   else
 136     {
 137       char addr_buf[GFC_XTOA_BUF_SIZE], func[1024], file[PATH_MAX];
 138       char *p;
 139       const char* addr = gfc_xtoa (ip, addr_buf, sizeof (addr_buf));
 140       write (state->outfd, addr, strlen (addr));
 141       write (state->outfd, "\n", 1);
 142
 143       if (! fd_gets (func, sizeof(func), state->infd))
 144         {
 145           state->error = 1;
 146           goto done;
 147         }
 148       if (! fd_gets (file, sizeof(file), state->infd))
 149         {
 150           state->error = 1;
 151           goto done;
 152         }
 153
 154         for (p = func; *p != '\n' && *p != '\r'; p++)
 155           ;
 156         *p = '\0';
 157
 158         /* _start is a setup routine that calls main(), and main() is
 159            the frontend routine that calls some setup stuff and then
 160            calls MAIN__, so at this point we should stop.  */
 161         if (strcmp (func, "_start") == 0 || strcmp (func, "main") == 0)
 162           return _URC_END_OF_STACK;
 163
 164         bt_header (state->frame_number);
 165         estr_write ("0x");
 166         estr_write (addr);
 167
 168         if (func[0] != '?' && func[1] != '?')
 169           {
 170             estr_write (" in ");
 171             estr_write (func);
 172           }
 173
 174         if (strncmp (file, "??", 2) == 0)
 175           estr_write ("\n");
 176         else
 177           {
 178             estr_write (" at ");
 179             estr_write (file);
 180           }
 181     }
 182
 183  done:
 184
 185   state->frame_number++;
 186
 187   return _URC_NO_REASON;
 188 }
 189
 190
 191 /* Display the backtrace.  */
 192
 193 void
 194 show_backtrace (void)
 195 {
 196   bt_state state;
 197   state.frame_number = 0;
 198   state.error = 0;
 199
 200   estr_write ("\nA fatal error occurred! Backtrace for this error:\n");
 201
 202 #if CAN_PIPE
 203
 204   if (addr2line_path == NULL)
 205     goto fallback_noerr;
 206
 207   /* We attempt to extract file and line information from addr2line.  */
 208   do
 209   {
 210     /* Local variables.  */
 211     int f[2], pid, inp[2];
 212
 213     /* Don't output an error message if something goes wrong, we'll simply
 214        fall back to printing the addresses.  */
 215     if (pipe (f) != 0)
 216       break;
 217     if (pipe (inp) != 0)
 218       break;
 219     if ((pid = fork ()) == -1)
 220       break;
 221
 222     if (pid == 0)
 223       {
 224         /* Child process.  */
 225 #define NUM_FIXEDARGS 7
 226         char *arg[NUM_FIXEDARGS];
 227         char *newenv[] = { NULL };
 228
 229         close (f[0]);
 230
 231         close (inp[1]);
 232         if (dup2 (inp[0], STDIN_FILENO) == -1)
 233           _exit (1);
 234         close (inp[0]);
 235
 236         close (STDERR_FILENO);
 237
 238         if (dup2 (f[1], STDOUT_FILENO) == -1)
 239           _exit (1);
 240         close (f[1]);
 241
 242         arg[0] = addr2line_path;
 243         arg[1] = (char *) "-e";
 244         arg[2] = full_exe_path ();
 245         arg[3] = (char *) "-f";
 246         arg[4] = (char *) "-s";
 247         arg[5] = (char *) "-C";
 248         arg[6] = NULL;
 249         execve (addr2line_path, arg, newenv);
 250         _exit (1);
 251 #undef NUM_FIXEDARGS
 252       }
 253
 254     /* Father process.  */
 255     close (f[1]);
 256     close (inp[0]);
 257
 258     state.outfd = inp[1];
 259     state.infd = f[0];
 260     state.direct_output = 0;
 261     _Unwind_Backtrace (trace_function, &state);
 262     if (state.error)
 263       goto fallback;
 264     close (inp[1]);
 265     wait (NULL);
 266     return;
 267
 268 fallback:
 269     estr_write ("** Something went wrong while running addr2line. **\n"
 270                 "** Falling back to a simpler backtrace scheme. **\n");
 271   }
 272   while (0);
 273
 274 #endif /* CAN_PIPE */
 275
 276 fallback_noerr:
 277   /* Fallback to the simple backtrace without addr2line.  */
 278   state.direct_output = 1;
 279   _Unwind_Backtrace (trace_function, &state);
 280 }