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


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

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

Version: -  FREEBSD  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-2  -  FREEBSD-11-1  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-4  -  FREEBSD-10-3  -  FREEBSD-10-2  -  FREEBSD-10-1  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-3  -  FREEBSD-9-2  -  FREEBSD-9-1  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-4  -  FREEBSD-8-3  -  FREEBSD-8-2  -  FREEBSD-8-1  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-4  -  FREEBSD-7-3  -  FREEBSD-7-2  -  FREEBSD-7-1  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-4  -  FREEBSD-6-3  -  FREEBSD-6-2  -  FREEBSD-6-1  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-5  -  FREEBSD-5-4  -  FREEBSD-5-3  -  FREEBSD-5-2  -  FREEBSD-5-1  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  linux-2.6  -  linux-2.4.22  -  MK83  -  MK84  -  PLAN9  -  DFBSD  -  NETBSD  -  NETBSD5  -  NETBSD4  -  NETBSD3  -  NETBSD20  -  OPENBSD  -  xnu-517  -  xnu-792  -  xnu-792.6.70  -  xnu-1228  -  xnu-1456.1.26  -  xnu-1699.24.8  -  xnu-2050.18.24  -  OPENSOLARIS  -  minix-3-1-1 
SearchContext: -  none  -  3  -  10 

    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 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: releng/9.1/sys/kern/imgact_shell.c 219352 2011-03-06 22:59:30Z kib $");
   29 
   30 #include <sys/param.h>
   31 #include <sys/vnode.h>
   32 #include <sys/proc.h>
   33 #include <sys/sbuf.h>
   34 #include <sys/systm.h>
   35 #include <sys/sysproto.h>
   36 #include <sys/exec.h>
   37 #include <sys/imgact.h>
   38 #include <sys/kernel.h>
   39 
   40 #if BYTE_ORDER == LITTLE_ENDIAN
   41 #define SHELLMAGIC      0x2123 /* #! */
   42 #else
   43 #define SHELLMAGIC      0x2321
   44 #endif
   45 
   46 /*
   47  * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE.  This is
   48  * significant because the caller has only mapped in one page of the
   49  * file we're reading.
   50  */
   51 #if MAXSHELLCMDLEN > PAGE_SIZE
   52 #error "MAXSHELLCMDLEN is larger than a single page!"
   53 #endif
   54 
   55 /*
   56  * MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!'
   57  * prefix and terminating newline.
   58  */
   59 CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3);
   60 
   61 /**
   62  * Shell interpreter image activator. An interpreter name beginning at
   63  * imgp->args->begin_argv is the minimal successful exit requirement.
   64  *
   65  * If the given file is a shell-script, then the first line will start
   66  * with the two characters `#!' (aka SHELLMAGIC), followed by the name
   67  * of the shell-interpreter to run, followed by zero or more tokens.
   68  *
   69  * The interpreter is then started up such that it will see:
   70  *    arg[0] -> The name of interpreter as specified after `#!' in the
   71  *              first line of the script.  The interpreter name must
   72  *              not be longer than MAXSHELLCMDLEN bytes.
   73  *    arg[1] -> *If* there are any additional tokens on the first line,
   74  *              then we add a new arg[1], which is a copy of the rest of
   75  *              that line.  The copy starts at the first token after the
   76  *              interpreter name.  We leave it to the interpreter to
   77  *              parse the tokens in that value.
   78  *    arg[x] -> the full pathname of the script.  This will either be
   79  *              arg[2] or arg[1], depending on whether or not tokens
   80  *              were found after the interpreter name.
   81  *  arg[x+1] -> all the arguments that were specified on the original
   82  *              command line.
   83  *
   84  * This processing is described in the execve(2) man page.
   85  */
   86 
   87 /*
   88  * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as
   89  * found on the first line of the script, and setup each token as a separate
   90  * value in arg[].  This extra processing did not match the behavior of other
   91  * OS's, and caused a few subtle problems.  For one, it meant the kernel was
   92  * deciding how those values should be parsed (wrt characters for quoting or
   93  * comments, etc), while the interpreter might have other rules for parsing.
   94  * It also meant the interpreter had no way of knowing which arguments came
   95  * from the first line of the shell script, and which arguments were specified
   96  * by the user on the command line.  That extra processing was dropped in the
   97  * 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029).
   98  */
   99 int
  100 exec_shell_imgact(imgp)
  101         struct image_params *imgp;
  102 {
  103         const char *image_header = imgp->image_header;
  104         const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname;
  105         int error, offset;
  106         size_t length;
  107         struct vattr vattr;
  108         struct sbuf *sname;
  109 
  110         /* a shell script? */
  111         if (((const short *)image_header)[0] != SHELLMAGIC)
  112                 return (-1);
  113 
  114         /*
  115          * Don't allow a shell script to be the shell for a shell
  116          *      script. :-)
  117          */
  118         if (imgp->interpreted)
  119                 return (ENOEXEC);
  120 
  121         imgp->interpreted = 1;
  122 
  123         /*
  124          * At this point we have the first page of the file mapped.
  125          * However, we don't know how far into the page the contents are
  126          * valid -- the actual file might be much shorter than the page.
  127          * So find out the file size.
  128          */
  129         error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred);
  130         if (error)
  131                 return (error);
  132 
  133         /*
  134          * Copy shell name and arguments from image_header into a string
  135          * buffer.
  136          */
  137         maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)];
  138         ihp = &image_header[2];
  139 
  140         /*
  141          * Find the beginning and end of the interpreter_name.  If the
  142          * line does not include any interpreter, or if the name which
  143          * was found is too long, we bail out.
  144          */
  145         while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
  146                 ihp++;
  147         interpb = ihp;
  148         while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n')
  149             && (*ihp != '\0')))
  150                 ihp++;
  151         interpe = ihp;
  152         if (interpb == interpe)
  153                 return (ENOEXEC);
  154         if (interpe - interpb >= MAXINTERP)
  155                 return (ENAMETOOLONG);
  156 
  157         /*
  158          * Find the beginning of the options (if any), and the end-of-line.
  159          * Then trim the trailing blanks off the value.  Note that some
  160          * other operating systems do *not* trim the trailing whitespace...
  161          */
  162         while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
  163                 ihp++;
  164         optb = ihp;
  165         while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0')))
  166                 ihp++;
  167         opte = ihp;
  168         if (opte == maxp)
  169                 return (ENOEXEC);
  170         while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t')))
  171                 opte = ihp;
  172 
  173         if (imgp->args->fname != NULL) {
  174                 fname = imgp->args->fname;
  175                 sname = NULL;
  176         } else {
  177                 sname = sbuf_new_auto();
  178                 sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd);
  179                 sbuf_finish(sname);
  180                 fname = sbuf_data(sname);
  181         }
  182 
  183         /*
  184          * We need to "pop" (remove) the present value of arg[0], and "push"
  185          * either two or three new values in the arg[] list.  To do this,
  186          * we first shift all the other values in the `begin_argv' area to
  187          * provide the exact amount of room for the values added.  Set up
  188          * `offset' as the number of bytes to be added to the `begin_argv'
  189          * area, and 'length' as the number of bytes being removed.
  190          */
  191         offset = interpe - interpb + 1;                 /* interpreter */
  192         if (opte > optb)                                /* options (if any) */
  193                 offset += opte - optb + 1;
  194         offset += strlen(fname) + 1;                    /* fname of script */
  195         length = (imgp->args->argc == 0) ? 0 :
  196             strlen(imgp->args->begin_argv) + 1;         /* bytes to delete */
  197 
  198         if (offset > imgp->args->stringspace + length) {
  199                 if (sname != NULL)
  200                         sbuf_delete(sname);
  201                 return (E2BIG);
  202         }
  203 
  204         bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
  205             imgp->args->endp - (imgp->args->begin_argv + length));
  206 
  207         offset -= length;               /* calculate actual adjustment */
  208         imgp->args->begin_envv += offset;
  209         imgp->args->endp += offset;
  210         imgp->args->stringspace -= offset;
  211 
  212         /*
  213          * If there was no arg[0] when we started, then the interpreter_name
  214          * is adding an argument (instead of replacing the arg[0] we started
  215          * with).  And we're always adding an argument when we include the
  216          * full pathname of the original script.
  217          */
  218         if (imgp->args->argc == 0)
  219                 imgp->args->argc = 1;
  220         imgp->args->argc++;
  221 
  222         /*
  223          * The original arg[] list has been shifted appropriately.  Copy in
  224          * the interpreter name and options-string.
  225          */
  226         length = interpe - interpb;
  227         bcopy(interpb, imgp->args->begin_argv, length);
  228         *(imgp->args->begin_argv + length) = '\0';
  229         offset = length + 1;
  230         if (opte > optb) {
  231                 length = opte - optb;
  232                 bcopy(optb, imgp->args->begin_argv + offset, length);
  233                 *(imgp->args->begin_argv + offset + length) = '\0';
  234                 offset += length + 1;
  235                 imgp->args->argc++;
  236         }
  237 
  238         /*
  239          * Finally, add the filename onto the end for the interpreter to
  240          * use and copy the interpreter's name to imgp->interpreter_name
  241          * for exec to use.
  242          */
  243         error = copystr(fname, imgp->args->begin_argv + offset,
  244             imgp->args->stringspace, NULL);
  245 
  246         if (error == 0)
  247                 imgp->interpreter_name = imgp->args->begin_argv;
  248 
  249         if (sname != NULL)
  250                 sbuf_delete(sname);
  251         return (error);
  252 }
  253 
  254 /*
  255  * Tell kern_execve.c about it, with a little help from the linker.
  256  */
  257 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
  258 EXEC_SET(shell, shell_execsw);

Cache object: 434778803e1b9649601f0c9a145ef118


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.