imgact_shell.c revision 140992 
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: head/sys/kern/imgact_shell.c 140992 2005-01-29 23:12:00Z sobomax $");
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. An interpreter name beginning
45 *	at imgp->args->begin_argv is the minimal successful exit requirement.
46 */
47int
48exec_shell_imgact(imgp)
49	struct image_params *imgp;
50{
51	const char *image_header = imgp->image_header;
52	const char *ihp;
53	int error, length, offset;
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[MAXSHELLCMDLEN]) {
76		/* Skip any whitespace */
77		while ((*ihp == ' ') || (*ihp == '\t')) {
78			ihp++;
79			continue;
80		}
81
82		/* End of line? */
83		if ((*ihp == '\n') || (*ihp == '#'))
84			break;
85
86		/* Found a token */
87		while ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') &&
88		    (*ihp != '#')) {
89			offset++;
90			ihp++;
91		}
92		/* Include terminating nulls in the offset */
93		offset++;
94	}
95
96	/* If the script gives a null line as the interpreter, we bail */
97	if (offset == 0)
98		return (ENOEXEC);
99
100	/* Check that we aren't too big */
101	if (offset > MAXSHELLCMDLEN)
102		return (ENAMETOOLONG);
103
104	/*
105	 * The full path name of the original script file must be tagged
106	 * onto the end, adjust the offset to deal with it.
107	 *
108	 * The original argv[0] is being replaced, set 'length' to the number
109	 * of bytes being removed.  So 'offset' is the number of bytes being
110	 * added and 'length' is the number of bytes being removed.
111	 */
112	offset += strlen(imgp->args->fname) + 1;	/* add fname */
113	length = (imgp->args->argc == 0) ? 0 :
114	    strlen(imgp->args->begin_argv) + 1;		/* bytes to delete */
115
116	if (offset - length > imgp->args->stringspace)
117		return (E2BIG);
118
119	bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
120	    imgp->args->endp - (imgp->args->begin_argv + length));
121
122	offset -= length;		/* calculate actual adjustment */
123	imgp->args->begin_envv += offset;
124	imgp->args->endp += offset;
125	imgp->args->stringspace -= offset;
126
127	/*
128	 * If there were no arguments then we've added one, otherwise
129	 * decr argc remove old argv[0], incr argc for fname add, net 0
130	 */
131	if (imgp->args->argc == 0)
132		imgp->args->argc = 1;
133
134	/*
135	 * Loop through the interpreter name yet again, copying as
136	 * we go.
137	 */
138	ihp = &image_header[2];
139	offset = 0;
140	while (ihp < &image_header[MAXSHELLCMDLEN]) {
141		/* Skip whitespace */
142		while ((*ihp == ' ' || *ihp == '\t')) {
143			ihp++;
144			continue;
145		}
146
147		/* End of line? */
148		if ((*ihp == '\n') || (*ihp == '#'))
149			break;
150
151		/* Found a token, copy it */
152		while ((*ihp != ' ') && (*ihp != '\t') &&
153		    (*ihp != '\n') && (*ihp != '#')) {
154			imgp->args->begin_argv[offset++] = *ihp++;
155		}
156		imgp->args->begin_argv[offset++] = '\0';
157		imgp->args->argc++;
158	}
159
160	/*
161	 * Finally, add the filename onto the end for the interpreter to
162	 * use and copy the interpreter's name to imgp->interpreter_name
163	 * for exec to use.
164	 */
165	error = copystr(imgp->args->fname, imgp->args->buf + offset,
166	    imgp->args->stringspace, &length);
167
168	if (error == 0)
169		error = copystr(imgp->args->begin_argv, imgp->interpreter_name,
170		    MAXSHELLCMDLEN, &length);
171
172	return (error);
173}
174
175/*
176 * Tell kern_execve.c about it, with a little help from the linker.
177 */
178static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
179EXEC_SET(shell, shell_execsw);
180