263 lines
8.7 KiB
C
263 lines
8.7 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 1993, David Greenman
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/vnode.h>
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#include <sys/proc.h>
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#include <sys/sbuf.h>
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#include <sys/systm.h>
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#include <sys/sysproto.h>
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#include <sys/exec.h>
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#include <sys/imgact.h>
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#include <sys/kernel.h>
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#if BYTE_ORDER == LITTLE_ENDIAN
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#define SHELLMAGIC 0x2123 /* #! */
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#else
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#define SHELLMAGIC 0x2321
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#endif
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/*
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* At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is
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* significant because the caller has only mapped in one page of the
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* file we're reading.
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*/
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#if MAXSHELLCMDLEN > PAGE_SIZE
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#error "MAXSHELLCMDLEN is larger than a single page!"
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#endif
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/*
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* MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!'
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* prefix and terminating newline.
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*/
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CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3);
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/**
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* Shell interpreter image activator. An interpreter name beginning at
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* imgp->args->begin_argv is the minimal successful exit requirement.
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*
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* If the given file is a shell-script, then the first line will start
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* with the two characters `#!' (aka SHELLMAGIC), followed by the name
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* of the shell-interpreter to run, followed by zero or more tokens.
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*
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* The interpreter is then started up such that it will see:
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* arg[0] -> The name of interpreter as specified after `#!' in the
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* first line of the script. The interpreter name must
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* not be longer than MAXSHELLCMDLEN bytes.
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* arg[1] -> *If* there are any additional tokens on the first line,
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* then we add a new arg[1], which is a copy of the rest of
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* that line. The copy starts at the first token after the
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* interpreter name. We leave it to the interpreter to
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* parse the tokens in that value.
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* arg[x] -> the full pathname of the script. This will either be
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* arg[2] or arg[1], depending on whether or not tokens
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* were found after the interpreter name.
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* arg[x+1] -> all the arguments that were specified on the original
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* command line.
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*
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* This processing is described in the execve(2) man page.
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*/
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/*
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* HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as
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* found on the first line of the script, and setup each token as a separate
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* value in arg[]. This extra processing did not match the behavior of other
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* OS's, and caused a few subtle problems. For one, it meant the kernel was
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* deciding how those values should be parsed (wrt characters for quoting or
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* comments, etc), while the interpreter might have other rules for parsing.
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* It also meant the interpreter had no way of knowing which arguments came
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* from the first line of the shell script, and which arguments were specified
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* by the user on the command line. That extra processing was dropped in the
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* 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029).
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*/
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int
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exec_shell_imgact(struct image_params *imgp)
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{
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const char *image_header = imgp->image_header;
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const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname;
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int error, offset;
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size_t length;
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struct vattr vattr;
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struct sbuf *sname;
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/* a shell script? */
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if (((const short *)image_header)[0] != SHELLMAGIC)
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return (-1);
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/*
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* Don't allow a shell script to be the shell for a shell
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* script. :-)
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*/
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if (imgp->interpreted & IMGACT_SHELL)
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return (ENOEXEC);
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imgp->interpreted |= IMGACT_SHELL;
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/*
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* At this point we have the first page of the file mapped.
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* However, we don't know how far into the page the contents are
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* valid -- the actual file might be much shorter than the page.
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* So find out the file size.
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*/
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error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred);
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if (error)
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return (error);
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/*
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* Copy shell name and arguments from image_header into a string
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* buffer.
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*/
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maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)];
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ihp = &image_header[2];
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/*
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* Find the beginning and end of the interpreter_name. If the
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* line does not include any interpreter, or if the name which
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* was found is too long, we bail out.
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*/
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while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
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ihp++;
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interpb = ihp;
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while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n')
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&& (*ihp != '\0')))
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ihp++;
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interpe = ihp;
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if (interpb == interpe)
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return (ENOEXEC);
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if (interpe - interpb >= MAXINTERP)
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return (ENAMETOOLONG);
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/*
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* Find the beginning of the options (if any), and the end-of-line.
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* Then trim the trailing blanks off the value. Note that some
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* other operating systems do *not* trim the trailing whitespace...
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*/
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while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
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ihp++;
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optb = ihp;
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while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0')))
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ihp++;
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opte = ihp;
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if (opte == maxp)
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return (ENOEXEC);
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while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t')))
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opte = ihp;
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if (imgp->args->fname != NULL) {
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fname = imgp->args->fname;
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sname = NULL;
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} else {
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sname = sbuf_new_auto();
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sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd);
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sbuf_finish(sname);
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fname = sbuf_data(sname);
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}
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/*
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* We need to "pop" (remove) the present value of arg[0], and "push"
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* either two or three new values in the arg[] list. To do this,
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* we first shift all the other values in the `begin_argv' area to
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* provide the exact amount of room for the values added. Set up
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* `offset' as the number of bytes to be added to the `begin_argv'
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* area, and 'length' as the number of bytes being removed.
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*/
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offset = interpe - interpb + 1; /* interpreter */
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if (opte > optb) /* options (if any) */
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offset += opte - optb + 1;
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offset += strlen(fname) + 1; /* fname of script */
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length = (imgp->args->argc == 0) ? 0 :
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strlen(imgp->args->begin_argv) + 1; /* bytes to delete */
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if (offset > imgp->args->stringspace + length) {
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if (sname != NULL)
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sbuf_delete(sname);
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return (E2BIG);
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}
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bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
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imgp->args->endp - (imgp->args->begin_argv + length));
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offset -= length; /* calculate actual adjustment */
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imgp->args->begin_envv += offset;
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imgp->args->endp += offset;
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imgp->args->stringspace -= offset;
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/*
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* If there was no arg[0] when we started, then the interpreter_name
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* is adding an argument (instead of replacing the arg[0] we started
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* with). And we're always adding an argument when we include the
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* full pathname of the original script.
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*/
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if (imgp->args->argc == 0)
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imgp->args->argc = 1;
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imgp->args->argc++;
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/*
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* The original arg[] list has been shifted appropriately. Copy in
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* the interpreter name and options-string.
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*/
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length = interpe - interpb;
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bcopy(interpb, imgp->args->begin_argv, length);
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*(imgp->args->begin_argv + length) = '\0';
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offset = length + 1;
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if (opte > optb) {
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length = opte - optb;
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bcopy(optb, imgp->args->begin_argv + offset, length);
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*(imgp->args->begin_argv + offset + length) = '\0';
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offset += length + 1;
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imgp->args->argc++;
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}
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/*
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* Finally, add the filename onto the end for the interpreter to
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* use and copy the interpreter's name to imgp->interpreter_name
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* for exec to use.
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*/
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error = copystr(fname, imgp->args->begin_argv + offset,
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imgp->args->stringspace, NULL);
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if (error == 0)
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imgp->interpreter_name = imgp->args->begin_argv;
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if (sname != NULL)
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sbuf_delete(sname);
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return (error);
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}
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/*
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* Tell kern_execve.c about it, with a little help from the linker.
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*/
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static struct execsw shell_execsw = {
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.ex_imgact = exec_shell_imgact,
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.ex_name = "#!"
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};
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EXEC_SET(shell, shell_execsw);
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