sys/kern/imgact_shell.c

   1 /*
   2  * Copyright (c) 1993, David Greenman
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  * $FreeBSD: src/sys/kern/imgact_shell.c,v 1.21.2.2 2001/12/22 01:21:39 jwd Exp $
  27  * $DragonFly: src/sys/kern/imgact_shell.c,v 1.6 2005/02/28 05:44:52 dillon Exp $
  28  */
  29
  30 #include <sys/param.h>
  31 #include <sys/systm.h>
  32 #include <sys/sysproto.h>
  33 #include <sys/exec.h>
  34 #include <sys/imgact.h>
  35 #include <sys/kernel.h>
  36
  37 #if BYTE_ORDER == LITTLE_ENDIAN
  38 #define SHELLMAGIC      0x2123 /* #! */
  39 #else
  40 #define SHELLMAGIC      0x2321
  41 #endif
  42
  43 /*
  44  * Shell interpreter image activator. A interpreter name beginning
  45  *      at imgp->args->begin_argv is the minimal successful exit requirement.
  46  */
  47 int
  48 exec_shell_imgact(struct image_params *imgp)
  49 {
  50         const char *image_header = imgp->image_header;
  51         const char *ihp;
  52         int error, length, offset;
  53
  54         /* a shell script? */
  55         if (((const short *) image_header)[0] != SHELLMAGIC)
  56                 return(-1);
  57
  58         /*
  59          * Don't allow a shell script to be the shell for a shell
  60          *      script. :-)
  61          */
  62         if (imgp->interpreted)
  63                 return(ENOEXEC);
  64
  65         imgp->interpreted = 1;
  66
  67         /*
  68          * Figure out the number of bytes that need to be reserved in the
  69          * argument string to copy the contents of the interpreter's command
  70          * line into the argument string.
  71          */
  72         ihp = &image_header[2];
  73         offset = 0;
  74         while (ihp < &image_header[PAGE_SIZE]) {
  75                 /* Skip any whitespace */
  76                 if (*ihp == ' ' || *ihp == '\t') {
  77                         ++ihp;
  78                         continue;
  79                 }
  80
  81                 /* End of line? */
  82                 if (*ihp == '\n' || *ihp == '#' || *ihp == '\0')
  83                         break;
  84
  85                 /* Found a token */
  86                 do {
  87                         ++offset;
  88                         ++ihp;
  89                 } while (ihp < &image_header[PAGE_SIZE] &&
  90                          *ihp != ' ' && *ihp != '\t' &&
  91                          *ihp != '\n' && *ihp != '#' && *ihp != '\0');
  92
  93                 /* Take into account the \0 that will terminate the token */
  94                 ++offset;
  95         }
  96
  97         /* If the script gives a null line as the interpreter, we bail */
  98         if (offset == 0)
  99                 return (ENOEXEC);
 100
 101         /* It should not be possible for offset to exceed PAGE_SIZE */
 102         KKASSERT(offset <= PAGE_SIZE);
 103
 104         /* Check that we aren't too big */
 105         if (ihp == &image_header[PAGE_SIZE])
 106                 return (ENAMETOOLONG);
 107
 108         /*
 109          * The full path name of the original script file must be tagged
 110          * onto the end, adjust the offset to deal with it.
 111          *
 112          * The original argv0 is being replaced, set 'length' to the number
 113          * of bytes being removed.  So 'offset' is the number of bytes being
 114          * added and 'length' is the number of bytes being removed.
 115          */
 116         offset += strlen(imgp->args->fname) + 1;        /* add fname */
 117         length = strlen(imgp->args->begin_argv) + 1;    /* bytes to delete */
 118
 119         if (offset - length > imgp->args->space)
 120                 return (E2BIG);
 121
 122         bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
 123                 imgp->args->endp - (imgp->args->begin_argv + length));
 124
 125         offset -= length;               /* calculate actual adjustment */
 126         imgp->args->begin_envv += offset;
 127         imgp->args->endp += offset;
 128         imgp->args->space -= offset;
 129         /* decr argc remove old argv[0], incr argc for fname add, net 0 */
 130
 131         /*
 132          * Loop through the interpreter name yet again, copying as
 133          * we go.
 134          */
 135         ihp = &image_header[2];
 136         offset = 0;
 137         while (ihp < &image_header[PAGE_SIZE]) {
 138                 /* Skip whitespace */
 139                 if (*ihp == ' ' || *ihp == '\t') {
 140                         ++ihp;
 141                         continue;
 142                 }
 143
 144                 /* End of line? */
 145                 if (*ihp == '\n' || *ihp == '#' || *ihp == '\0')
 146                         break;
 147
 148                 /* Found a token, copy it */
 149                 do {
 150                         imgp->args->begin_argv[offset] = *ihp;
 151                         ++ihp;
 152                         ++offset;
 153                 } while (ihp < &image_header[PAGE_SIZE] &&
 154                          *ihp != ' ' && *ihp != '\t' &&
 155                          *ihp != '\n' && *ihp != '#' && *ihp != '\0');
 156
 157                 /* And terminate the argument */
 158                 imgp->args->begin_argv[offset] = '\0';
 159                 imgp->args->argc++;
 160                 ++offset;
 161         }
 162
 163         /*
 164          * Finally, add the filename onto the end for the interpreter to
 165          * use and copy the interpreter's name to imgp->interpreter_name
 166          * for exec to use.
 167          */
 168         error = copystr(imgp->args->fname, imgp->args->buf + offset,
 169                         imgp->args->space, &length);
 170
 171         if (error == 0) {
 172                 error = copystr(imgp->args->begin_argv, imgp->interpreter_name,
 173                                 MAXSHELLCMDLEN, &length);
 174         }
 175         return (error);
 176 }
 177
 178 /*
 179  * Tell kern_execve.c about it, with a little help from the linker.
 180  */
 181 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
 182 EXEC_SET(shell, shell_execsw);