posix/execvpe.c

   1 /* Copyright (C) 1991-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <alloca.h>
  19 #include <unistd.h>
  20 #include <stdarg.h>
  21 #include <stdbool.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <errno.h>
  25 #include <paths.h>
  26
  27
  28 /* The file is accessible but it is not an executable file.  Invoke
  29    the shell to interpret it as a script.  */
  30 static void
  31 internal_function
  32 scripts_argv (const char *file, char *const argv[], int argc, char **new_argv)
  33 {
  34   /* Construct an argument list for the shell.  */
  35   new_argv[0] = (char *) _PATH_BSHELL;
  36   new_argv[1] = (char *) file;
  37   while (argc > 1)
  38     {
  39       new_argv[argc] = argv[argc - 1];
  40       --argc;
  41     }
  42 }
  43
  44
  45 /* Execute FILE, searching in the `PATH' environment variable if it contains
  46    no slashes, with arguments ARGV and environment from ENVP.  */
  47 int
  48 __execvpe (file, argv, envp)
  49      const char *file;
  50      char *const argv[];
  51      char *const envp[];
  52 {
  53   if (*file == '\0')
  54     {
  55       /* We check the simple case first. */
  56       __set_errno (ENOENT);
  57       return -1;
  58     }
  59
  60   if (strchr (file, '/') != NULL)
  61     {
  62       /* Don't search when it contains a slash.  */
  63       __execve (file, argv, envp);
  64
  65       if (errno == ENOEXEC)
  66         {
  67           /* Count the arguments.  */
  68           int argc = 0;
  69           while (argv[argc++])
  70             ;
  71           size_t len = (argc + 1) * sizeof (char *);
  72           char **script_argv;
  73           void *ptr = NULL;
  74           if (__libc_use_alloca (len))
  75             script_argv = alloca (len);
  76           else
  77             script_argv = ptr = malloc (len);
  78
  79           if (script_argv != NULL)
  80             {
  81               scripts_argv (file, argv, argc, script_argv);
  82               __execve (script_argv[0], script_argv, envp);
  83
  84               free (ptr);
  85             }
  86         }
  87     }
  88   else
  89     {
  90       size_t pathlen;
  91       size_t alloclen = 0;
  92       char *path = getenv ("PATH");
  93       if (path == NULL)
  94         {
  95           pathlen = confstr (_CS_PATH, (char *) NULL, 0);
  96           alloclen = pathlen + 1;
  97         }
  98       else
  99         pathlen = strlen (path);
 100
 101       size_t len = strlen (file) + 1;
 102       alloclen += pathlen + len + 1;
 103
 104       char *name;
 105       char *path_malloc = NULL;
 106       if (__libc_use_alloca (alloclen))
 107         name = alloca (alloclen);
 108       else
 109         {
 110           path_malloc = name = malloc (alloclen);
 111           if (name == NULL)
 112             return -1;
 113         }
 114
 115       if (path == NULL)
 116         {
 117           /* There is no `PATH' in the environment.
 118              The default search path is the current directory
 119              followed by the path `confstr' returns for `_CS_PATH'.  */
 120           path = name + pathlen + len + 1;
 121           path[0] = ':';
 122           (void) confstr (_CS_PATH, path + 1, pathlen);
 123         }
 124
 125       /* Copy the file name at the top.  */
 126       name = (char *) memcpy (name + pathlen + 1, file, len);
 127       /* And add the slash.  */
 128       *--name = '/';
 129
 130       char **script_argv = NULL;
 131       void *script_argv_malloc = NULL;
 132       bool got_eacces = false;
 133       char *p = path;
 134       do
 135         {
 136           char *startp;
 137
 138           path = p;
 139           p = __strchrnul (path, ':');
 140
 141           if (p == path)
 142             /* Two adjacent colons, or a colon at the beginning or the end
 143                of `PATH' means to search the current directory.  */
 144             startp = name + 1;
 145           else
 146             startp = (char *) memcpy (name - (p - path), path, p - path);
 147
 148           /* Try to execute this name.  If it works, execve will not return. */
 149           __execve (startp, argv, envp);
 150
 151           if (errno == ENOEXEC)
 152             {
 153               if (script_argv == NULL)
 154                 {
 155                   /* Count the arguments.  */
 156                   int argc = 0;
 157                   while (argv[argc++])
 158                     ;
 159                   size_t arglen = (argc + 1) * sizeof (char *);
 160                   if (__libc_use_alloca (alloclen + arglen))
 161                     script_argv = alloca (arglen);
 162                   else
 163                     script_argv = script_argv_malloc = malloc (arglen);
 164                   if (script_argv == NULL)
 165                     {
 166                       /* A possible EACCES error is not as important as
 167                          the ENOMEM.  */
 168                       got_eacces = false;
 169                       break;
 170                     }
 171                   scripts_argv (startp, argv, argc, script_argv);
 172                 }
 173
 174               __execve (script_argv[0], script_argv, envp);
 175             }
 176
 177           switch (errno)
 178             {
 179             case EACCES:
 180               /* Record the we got a `Permission denied' error.  If we end
 181                  up finding no executable we can use, we want to diagnose
 182                  that we did find one but were denied access.  */
 183               got_eacces = true;
 184             case ENOENT:
 185             case ESTALE:
 186             case ENOTDIR:
 187               /* Those errors indicate the file is missing or not executable
 188                  by us, in which case we want to just try the next path
 189                  directory.  */
 190             case ENODEV:
 191             case ETIMEDOUT:
 192               /* Some strange filesystems like AFS return even
 193                  stranger error numbers.  They cannot reasonably mean
 194                  anything else so ignore those, too.  */
 195               break;
 196
 197             default:
 198               /* Some other error means we found an executable file, but
 199                  something went wrong executing it; return the error to our
 200                  caller.  */
 201               return -1;
 202             }
 203         }
 204       while (*p++ != '\0');
 205
 206       /* We tried every element and none of them worked.  */
 207       if (got_eacces)
 208         /* At least one failure was due to permissions, so report that
 209            error.  */
 210         __set_errno (EACCES);
 211
 212       free (script_argv_malloc);
 213       free (path_malloc);
 214     }
 215
 216   /* Return the error from the last attempt (probably ENOENT).  */
 217   return -1;
 218 }
 219 weak_alias (__execvpe, execvpe)