posix/execvp.c

   1 /* Copyright (C) 1991,92, 1995-99, 2002, 2004, 2005, 2007
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <alloca.h>
  21 #include <unistd.h>
  22 #include <stdarg.h>
  23 #include <stdbool.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <errno.h>
  27 #include <paths.h>
  28
  29
  30 /* The file is accessible but it is not an executable file.  Invoke
  31    the shell to interpret it as a script.  */
  32 static void
  33 internal_function
  34 scripts_argv (const char *file, char *const argv[], int argc, char **new_argv)
  35 {
  36   /* Construct an argument list for the shell.  */
  37   new_argv[0] = (char *) _PATH_BSHELL;
  38   new_argv[1] = (char *) file;
  39   while (argc > 1)
  40     {
  41       new_argv[argc] = argv[argc - 1];
  42       --argc;
  43     }
  44 }
  45
  46
  47 /* Execute FILE, searching in the `PATH' environment variable if it contains
  48    no slashes, with arguments ARGV and environment from `environ'.  */
  49 int
  50 execvp (file, argv)
  51      const char *file;
  52      char *const argv[];
  53 {
  54   if (*file == '\0')
  55     {
  56       /* We check the simple case first. */
  57       __set_errno (ENOENT);
  58       return -1;
  59     }
  60
  61   if (strchr (file, '/') != NULL)
  62     {
  63       /* Don't search when it contains a slash.  */
  64       __execve (file, argv, __environ);
  65
  66       if (errno == ENOEXEC)
  67         {
  68           /* Count the arguments.  */
  69           int argc = 0;
  70           while (argv[argc++])
  71             ;
  72           size_t len = (argc + 1) * sizeof (char *);
  73           char **script_argv;
  74           void *ptr = NULL;
  75           if (__libc_use_alloca (len))
  76             script_argv = alloca (len);
  77           else
  78             script_argv = ptr = malloc (len);
  79
  80           if (script_argv != NULL)
  81             {
  82               scripts_argv (file, argv, argc, script_argv);
  83               __execve (script_argv[0], script_argv, __environ);
  84
  85               free (ptr);
  86             }
  87         }
  88     }
  89   else
  90     {
  91       size_t pathlen;
  92       size_t alloclen = 0;
  93       char *path = getenv ("PATH");
  94       if (path == NULL)
  95         {
  96           pathlen = confstr (_CS_PATH, (char *) NULL, 0);
  97           alloclen = pathlen + 1;
  98         }
  99       else
 100         pathlen = strlen (path);
 101
 102       size_t len = strlen (file) + 1;
 103       alloclen += pathlen + len + 1;
 104
 105       char *name;
 106       char *path_malloc = NULL;
 107       if (__libc_use_alloca (alloclen))
 108         name = alloca (alloclen);
 109       else
 110         {
 111           path_malloc = name = malloc (alloclen);
 112           if (name == NULL)
 113             return -1;
 114         }
 115
 116       if (path == NULL)
 117         {
 118           /* There is no `PATH' in the environment.
 119              The default search path is the current directory
 120              followed by the path `confstr' returns for `_CS_PATH'.  */
 121           path = name + pathlen + len + 1;
 122           path[0] = ':';
 123           (void) confstr (_CS_PATH, path + 1, pathlen);
 124         }
 125
 126       /* Copy the file name at the top.  */
 127       name = (char *) memcpy (name + pathlen + 1, file, len);
 128       /* And add the slash.  */
 129       *--name = '/';
 130
 131       char **script_argv = NULL;
 132       void *script_argv_malloc = NULL;
 133       bool got_eacces = false;
 134       char *p = path;
 135       do
 136         {
 137           char *startp;
 138
 139           path = p;
 140           p = __strchrnul (path, ':');
 141
 142           if (p == path)
 143             /* Two adjacent colons, or a colon at the beginning or the end
 144                of `PATH' means to search the current directory.  */
 145             startp = name + 1;
 146           else
 147             startp = (char *) memcpy (name - (p - path), path, p - path);
 148
 149           /* Try to execute this name.  If it works, execve will not return. */
 150           __execve (startp, argv, __environ);
 151
 152           if (errno == ENOEXEC)
 153             {
 154               if (script_argv == NULL)
 155                 {
 156                   /* Count the arguments.  */
 157                   int argc = 0;
 158                   while (argv[argc++])
 159                     ;
 160                   size_t arglen = (argc + 1) * sizeof (char *);
 161                   if (__libc_use_alloca (alloclen + arglen))
 162                     script_argv = alloca (arglen);
 163                   else
 164                     script_argv = script_argv_malloc = malloc (arglen);
 165                   if (script_argv == NULL)
 166                     {
 167                       /* A possible EACCES error is not as important as
 168                          the ENOMEM.  */
 169                       got_eacces = false;
 170                       break;
 171                     }
 172                   scripts_argv (startp, argv, argc, script_argv);
 173                 }
 174
 175               __execve (script_argv[0], script_argv, __environ);
 176             }
 177
 178           switch (errno)
 179             {
 180             case EACCES:
 181               /* Record the we got a `Permission denied' error.  If we end
 182                  up finding no executable we can use, we want to diagnose
 183                  that we did find one but were denied access.  */
 184               got_eacces = true;
 185             case ENOENT:
 186             case ESTALE:
 187             case ENOTDIR:
 188               /* Those errors indicate the file is missing or not executable
 189                  by us, in which case we want to just try the next path
 190                  directory.  */
 191             case ENODEV:
 192             case ETIMEDOUT:
 193               /* Some strange filesystems like AFS return even
 194                  stranger error numbers.  They cannot reasonably mean
 195                  anything else so ignore those, too.  */
 196               break;
 197
 198             default:
 199               /* Some other error means we found an executable file, but
 200                  something went wrong executing it; return the error to our
 201                  caller.  */
 202               return -1;
 203             }
 204         }
 205       while (*p++ != '\0');
 206
 207       /* We tried every element and none of them worked.  */
 208       if (got_eacces)
 209         /* At least one failure was due to permissions, so report that
 210            error.  */
 211         __set_errno (EACCES);
 212
 213       free (script_argv_malloc);
 214       free (path_malloc);
 215     }
 216
 217   /* Return the error from the last attempt (probably ENOENT).  */
 218   return -1;
 219 }
 220 libc_hidden_def (execvp)