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: releng/5.1/sys/kern/imgact_shell.c 108533 2003-01-01 18:49:04Z schweikh $
   27  */
   28 
   29 #include <sys/param.h>
   30 #include <sys/systm.h>
   31 #include <sys/sysproto.h>
   32 #include <sys/exec.h>
   33 #include <sys/imgact.h>
   34 #include <sys/kernel.h>
   35 
   36 #if BYTE_ORDER == LITTLE_ENDIAN
   37 #define SHELLMAGIC      0x2123 /* #! */
   38 #else
   39 #define SHELLMAGIC      0x2321
   40 #endif
   41 
   42 /*
   43  * Shell interpreter image activator. An interpreter name beginning
   44  *      at imgp->stringbase is the minimal successful exit requirement.
   45  */
   46 int
   47 exec_shell_imgact(imgp)
   48         struct image_params *imgp;
   49 {
   50         const char *image_header = imgp->image_header;
   51         const char *ihp, *line_endp;
   52         char *interp;
   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          * Copy shell name and arguments from image_header into string
   69          *      buffer.
   70          */
   71 
   72         /*
   73          * Find end of line; return if the line > MAXSHELLCMDLEN long.
   74          */
   75         for (ihp = &image_header[2]; *ihp != '\n' && *ihp != '#'; ++ihp) {
   76                 if (ihp >= &image_header[MAXSHELLCMDLEN])
   77                         return(ENAMETOOLONG);
   78         }
   79         line_endp = ihp;
   80 
   81         /* reset for another pass */
   82         ihp = &image_header[2];
   83 
   84         /* Skip over leading spaces - until the interpreter name */
   85         while ((*ihp == ' ') || (*ihp == '\t')) ihp++;
   86 
   87         /* copy the interpreter name */
   88         interp = imgp->interpreter_name;
   89         while ((ihp < line_endp) && (*ihp != ' ') && (*ihp != '\t'))
   90                 *interp++ = *ihp++;
   91         *interp = '\0';
   92 
   93         /* Disallow a null interpreter filename */
   94         if (*imgp->interpreter_name == '\0')
   95                 return(ENOEXEC);
   96 
   97         /* reset for another pass */
   98         ihp = &image_header[2];
   99 
  100         /* copy the interpreter name and arguments */
  101         while (ihp < line_endp) {
  102                 /* Skip over leading spaces */
  103                 while ((*ihp == ' ') || (*ihp == '\t')) ihp++;
  104 
  105                 if (ihp < line_endp) {
  106                         /*
  107                          * Copy to end of token. No need to watch stringspace
  108                          *      because this is at the front of the string buffer
  109                          *      and the maximum shell command length is tiny.
  110                          */
  111                         while ((ihp < line_endp) && (*ihp != ' ') && (*ihp != '\t')) {
  112                                 *imgp->stringp++ = *ihp++;
  113                                 imgp->stringspace--;
  114                         }
  115 
  116                         *imgp->stringp++ = 0;
  117                         imgp->stringspace--;
  118 
  119                         imgp->argc++;
  120                 }
  121         }
  122 
  123         imgp->argv0 = imgp->fname;
  124 
  125         return(0);
  126 }
  127 
  128 /*
  129  * Tell kern_execve.c about it, with a little help from the linker.
  130  */
  131 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
  132 EXEC_SET(shell, shell_execsw);

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