libgfortran/runtime/backtrace.c

   1 /* Copyright (C) 2006-2014 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, and
  44    can we use pipes to communicate with the subprocess.  */
  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_CLOSE))
  49
  50 #ifndef PATH_MAX
  51 #define PATH_MAX 4096
  52 #endif
  53
  54
  55 /* GDB style #NUM index for each stack frame.  */
  56
  57 static void
  58 bt_header (int num)
  59 {
  60   st_printf ("#%d  ", num);
  61 }
  62
  63
  64 /* fgets()-like function that reads a line from a fd, without
  65    needing to malloc() a buffer, and does not use locks, hence should
  66    be async-signal-safe.  */
  67
  68 static char *
  69 fd_gets (char *s, int size, int fd)
  70 {
  71   for (int i = 0; i < size; i++)
  72     {
  73       char c;
  74       ssize_t nread = read (fd, &c, 1);
  75       if (nread == 1)
  76         {
  77           s[i] = c;
  78           if (c == '\n')
  79             {
  80               if (i + 1 < size)
  81                 s[i+1] = '\0';
  82               else
  83                 s[i] = '\0';
  84               break;
  85             }
  86         }
  87       else
  88         {
  89           s[i] = '\0';
  90           if (i == 0)
  91             return NULL;
  92           break;
  93         }
  94     }
  95   return s;
  96 }
  97
  98
  99 extern char *addr2line_path;
 100
 101 /* Struct containing backtrace state.  */
 102 typedef struct
 103 {
 104   int frame_number;
 105   int direct_output;
 106   int outfd;
 107   int infd;
 108   int error;
 109 }
 110 bt_state;
 111
 112 static _Unwind_Reason_Code
 113 trace_function (struct _Unwind_Context *context, void *state_ptr)
 114 {
 115   bt_state* state = (bt_state*) state_ptr;
 116   _Unwind_Ptr ip;
 117 #ifdef HAVE_GETIPINFO
 118   int ip_before_insn = 0;
 119   ip = _Unwind_GetIPInfo (context, &ip_before_insn);
 120
 121   /* If the unwinder gave us a 'return' address, roll it back a little
 122      to ensure we get the correct line number for the call itself.  */
 123   if (! ip_before_insn)
 124     --ip;
 125 #else
 126   ip = _Unwind_GetIP (context);
 127 #endif
 128
 129   if (state->direct_output)
 130     {
 131       bt_header(state->frame_number);
 132       st_printf ("%p\n", (void*) ip);
 133     }
 134   else
 135     {
 136       char addr_buf[GFC_XTOA_BUF_SIZE], func[1024], file[PATH_MAX];
 137       char *p;
 138       const char* addr = gfc_xtoa (ip, addr_buf, sizeof (addr_buf));
 139       write (state->outfd, addr, strlen (addr));
 140       write (state->outfd, "\n", 1);
 141
 142       if (! fd_gets (func, sizeof(func), state->infd))
 143         {
 144           state->error = 1;
 145           goto done;
 146         }
 147       if (! fd_gets (file, sizeof(file), state->infd))
 148         {
 149           state->error = 1;
 150           goto done;
 151         }
 152
 153         for (p = func; *p != '\n' && *p != '\r'; p++)
 154           ;
 155         *p = '\0';
 156
 157         /* _start is a setup routine that calls main(), and main() is
 158            the frontend routine that calls some setup stuff and then
 159            calls MAIN__, so at this point we should stop.  */
 160         if (strcmp (func, "_start") == 0 || strcmp (func, "main") == 0)
 161           return _URC_END_OF_STACK;
 162
 163         bt_header (state->frame_number);
 164         estr_write ("0x");
 165         estr_write (addr);
 166
 167         if (func[0] != '?' && func[1] != '?')
 168           {
 169             estr_write (" in ");
 170             estr_write (func);
 171           }
 172
 173         if (strncmp (file, "??", 2) == 0)
 174           estr_write ("\n");
 175         else
 176           {
 177             estr_write (" at ");
 178             estr_write (file);
 179           }
 180     }
 181
 182  done:
 183
 184   state->frame_number++;
 185
 186   return _URC_NO_REASON;
 187 }
 188
 189
 190 /* Display the backtrace.  */
 191
 192 void
 193 backtrace (void)
 194 {
 195   bt_state state;
 196   state.frame_number = 0;
 197   state.error = 0;
 198
 199 #if CAN_PIPE
 200
 201   if (addr2line_path == NULL)
 202     goto fallback_noerr;
 203
 204   /* We attempt to extract file and line information from addr2line.  */
 205   do
 206   {
 207     /* Local variables.  */
 208     int f[2], pid, inp[2];
 209
 210     /* Don't output an error message if something goes wrong, we'll simply
 211        fall back to printing the addresses.  */
 212     if (pipe (f) != 0)
 213       break;
 214     if (pipe (inp) != 0)
 215       break;
 216     if ((pid = fork ()) == -1)
 217       break;
 218
 219     if (pid == 0)
 220       {
 221         /* Child process.  */
 222 #define NUM_FIXEDARGS 7
 223         char *arg[NUM_FIXEDARGS];
 224         char *newenv[] = { NULL };
 225
 226         close (f[0]);
 227
 228         close (inp[1]);
 229         if (dup2 (inp[0], STDIN_FILENO) == -1)
 230           _exit (1);
 231         close (inp[0]);
 232
 233         close (STDERR_FILENO);
 234
 235         if (dup2 (f[1], STDOUT_FILENO) == -1)
 236           _exit (1);
 237         close (f[1]);
 238
 239         arg[0] = addr2line_path;
 240         arg[1] = (char *) "-e";
 241         arg[2] = full_exe_path ();
 242         arg[3] = (char *) "-f";
 243         arg[4] = (char *) "-s";
 244         arg[5] = (char *) "-C";
 245         arg[6] = NULL;
 246         execve (addr2line_path, arg, newenv);
 247         _exit (1);
 248 #undef NUM_FIXEDARGS
 249       }
 250
 251     /* Father process.  */
 252     close (f[1]);
 253     close (inp[0]);
 254
 255     state.outfd = inp[1];
 256     state.infd = f[0];
 257     state.direct_output = 0;
 258     _Unwind_Backtrace (trace_function, &state);
 259     if (state.error)
 260       goto fallback;
 261     close (inp[1]);
 262     close (f[0]);
 263     wait (NULL);
 264     return;
 265
 266 fallback:
 267     estr_write ("** Something went wrong while running addr2line. **\n"
 268                 "** Falling back to a simpler backtrace scheme. **\n");
 269   }
 270   while (0);
 271
 272 fallback_noerr:
 273 #endif /* CAN_PIPE */
 274
 275   /* Fallback to the simple backtrace without addr2line.  */
 276   state.direct_output = 1;
 277   _Unwind_Backtrace (trace_function, &state);
 278 }
 279 iexport(backtrace);