The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/imgact_shell.c

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    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         size_t length, offset;
   53         int error;
   54 
   55         /* a shell script? */
   56         if (((const short *) image_header)[0] != SHELLMAGIC)
   57                 return(-1);
   58 
   59         /*
   60          * Don't allow a shell script to be the shell for a shell
   61          *      script. :-)
   62          */
   63         if (imgp->interpreted)
   64                 return(ENOEXEC);
   65 
   66         imgp->interpreted = 1;
   67 
   68         /*
   69          * Figure out the number of bytes that need to be reserved in the
   70          * argument string to copy the contents of the interpreter's command
   71          * line into the argument string.
   72          */
   73         ihp = &image_header[2];
   74         offset = 0;
   75         while (ihp < &image_header[PAGE_SIZE]) {
   76                 /* Skip any whitespace */
   77                 if (*ihp == ' ' || *ihp == '\t') {
   78                         ++ihp;
   79                         continue;
   80                 }
   81 
   82                 /* End of line? */
   83                 if (*ihp == '\n' || *ihp == '#' || *ihp == '\0')
   84                         break;
   85 
   86                 /* Found a token */
   87                 do {
   88                         ++offset;
   89                         ++ihp;
   90                 } while (ihp < &image_header[PAGE_SIZE] &&
   91                          *ihp != ' ' && *ihp != '\t' && 
   92                          *ihp != '\n' && *ihp != '#' && *ihp != '\0');
   93 
   94                 /* Take into account the \0 that will terminate the token */
   95                 ++offset;
   96         }
   97 
   98         /* If the script gives a null line as the interpreter, we bail */
   99         if (offset == 0)
  100                 return (ENOEXEC);
  101 
  102         /* It should not be possible for offset to exceed PAGE_SIZE */
  103         KKASSERT(offset <= PAGE_SIZE);
  104 
  105         /* Check that we aren't too big */
  106         if (ihp == &image_header[PAGE_SIZE])
  107                 return (ENAMETOOLONG);
  108 
  109         /*
  110          * The full path name of the original script file must be tagged
  111          * onto the end, adjust the offset to deal with it.  
  112          *
  113          * The original argv0 is being replaced, set 'length' to the number
  114          * of bytes being removed.  So 'offset' is the number of bytes being
  115          * added and 'length' is the number of bytes being removed.
  116          */
  117         offset += strlen(imgp->args->fname) + 1;        /* add fname */
  118         length = strlen(imgp->args->begin_argv) + 1;    /* bytes to delete */
  119 
  120         if (offset - length > imgp->args->space)
  121                 return (E2BIG);
  122 
  123         bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
  124                 imgp->args->endp - (imgp->args->begin_argv + length));
  125 
  126         offset -= length;               /* calculate actual adjustment */
  127         imgp->args->begin_envv += offset;
  128         imgp->args->endp += offset;
  129         imgp->args->space -= offset;
  130         /* decr argc remove old argv[0], incr argc for fname add, net 0 */
  131 
  132         /*
  133          * Loop through the interpreter name yet again, copying as
  134          * we go.
  135          */
  136         ihp = &image_header[2];
  137         offset = 0;
  138         while (ihp < &image_header[PAGE_SIZE]) {
  139                 /* Skip whitespace */
  140                 if (*ihp == ' ' || *ihp == '\t') {
  141                         ++ihp;
  142                         continue;
  143                 }
  144 
  145                 /* End of line? */
  146                 if (*ihp == '\n' || *ihp == '#' || *ihp == '\0')
  147                         break;
  148 
  149                 /* Found a token, copy it */
  150                 do {
  151                         imgp->args->begin_argv[offset] = *ihp;
  152                         ++ihp;
  153                         ++offset;
  154                 } while (ihp < &image_header[PAGE_SIZE] &&
  155                          *ihp != ' ' && *ihp != '\t' && 
  156                          *ihp != '\n' && *ihp != '#' && *ihp != '\0');
  157 
  158                 /* And terminate the argument */
  159                 imgp->args->begin_argv[offset] = '\0';
  160                 imgp->args->argc++;
  161                 ++offset;
  162         }
  163 
  164         /*
  165          * Finally, add the filename onto the end for the interpreter to
  166          * use and copy the interpreter's name to imgp->interpreter_name
  167          * for exec to use.
  168          */
  169         error = copystr(imgp->args->fname, imgp->args->buf + offset,
  170                         imgp->args->space, &length);
  171 
  172         if (error == 0) {
  173                 error = copystr(imgp->args->begin_argv, imgp->interpreter_name,
  174                                 MAXSHELLCMDLEN, &length);
  175         }
  176         return (error);
  177 }
  178 
  179 /*
  180  * Tell kern_execve.c about it, with a little help from the linker.
  181  */
  182 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
  183 EXEC_SET(shell, shell_execsw);

Cache object: 2e72d56edf64154f858f1f805acc3858


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