2 * Copyright (c) 1993, David Greenman
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
30 #include <sys/param.h>
31 #include <sys/vnode.h>
33 #include <sys/systm.h>
34 #include <sys/sysproto.h>
36 #include <sys/imgact.h>
37 #include <sys/kernel.h>
39 #if BYTE_ORDER == LITTLE_ENDIAN
40 #define SHELLMAGIC 0x2123 /* #! */
42 #define SHELLMAGIC 0x2321
46 * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is
47 * significant because the caller has only mapped in one page of the
48 * file we're reading. This code should be changed to know how to
49 * read in the second page, but I'm not doing that just yet...
51 #if MAXSHELLCMDLEN > PAGE_SIZE
52 #error "MAXSHELLCMDLEN is larger than a single page!"
56 * Shell interpreter image activator. An interpreter name beginning at
57 * imgp->args->begin_argv is the minimal successful exit requirement.
59 * If the given file is a shell-script, then the first line will start
60 * with the two characters `#!' (aka SHELLMAGIC), followed by the name
61 * of the shell-interpreter to run, followed by zero or more tokens.
63 * The interpreter is then started up such that it will see:
64 * arg[0] -> The name of interpreter as specified after `#!' in the
65 * first line of the script. The interpreter name must
66 * not be longer than MAXSHELLCMDLEN bytes.
67 * arg[1] -> *If* there are any additional tokens on the first line,
68 * then we add a new arg[1], which is a copy of the rest of
69 * that line. The copy starts at the first token after the
70 * interpreter name. We leave it to the interpreter to
71 * parse the tokens in that value.
72 * arg[x] -> the full pathname of the script. This will either be
73 * arg[2] or arg[1], depending on whether or not tokens
74 * were found after the interpreter name.
75 * arg[x+1] -> all the arguments that were specified on the original
78 * This processing is described in the execve(2) man page.
82 * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as
83 * found on the first line of the script, and setup each token as a separate
84 * value in arg[]. This extra processing did not match the behavior of other
85 * OS's, and caused a few subtle problems. For one, it meant the kernel was
86 * deciding how those values should be parsed (wrt characters for quoting or
87 * comments, etc), while the interpreter might have other rules for parsing.
88 * It also meant the interpreter had no way of knowing which arguments came
89 * from the first line of the shell script, and which arguments were specified
90 * by the user on the command line. That extra processing was dropped in the
91 * 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029).
94 exec_shell_imgact(imgp)
95 struct image_params *imgp;
97 const char *image_header = imgp->image_header;
98 const char *ihp, *interpb, *interpe, *maxp, *optb, *opte;
100 size_t length, clength;
103 /* a shell script? */
104 if (((const short *) image_header)[0] != SHELLMAGIC)
108 * Don't allow a shell script to be the shell for a shell
111 if (imgp->interpreted)
114 imgp->interpreted = 1;
117 * At this point we have the first page of the file mapped.
118 * However, we don't know how far into the page the contents are
119 * valid -- the actual file might be much shorter than the page.
120 * So find out the file size.
122 error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred, curthread);
127 * Copy shell name and arguments from image_header into a string
128 * buffer. Remember that the caller has mapped only the
129 * first page of the file into memory.
131 clength = (vattr.va_size > PAGE_SIZE) ? PAGE_SIZE : vattr.va_size;
133 maxp = &image_header[clength];
134 ihp = &image_header[2];
137 * Find the beginning and end of the interpreter_name. If the
138 * line does not include any interpreter, or if the name which
139 * was found is too long, we bail out.
141 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
144 while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n')
148 if (interpb == interpe)
150 if ((interpe - interpb) >= MAXSHELLCMDLEN)
151 return (ENAMETOOLONG);
154 * Find the beginning of the options (if any), and the end-of-line.
155 * Then trim the trailing blanks off the value. Note that some
156 * other operating systems do *not* trim the trailing whitespace...
158 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t')))
161 while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0')))
164 while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t')))
168 * We need to "pop" (remove) the present value of arg[0], and "push"
169 * either two or three new values in the arg[] list. To do this,
170 * we first shift all the other values in the `begin_argv' area to
171 * provide the exact amount of room for the values added. Set up
172 * `offset' as the number of bytes to be added to the `begin_argv'
173 * area, and 'length' as the number of bytes being removed.
175 offset = interpe - interpb + 1; /* interpreter */
176 if (opte > optb) /* options (if any) */
177 offset += opte - optb + 1;
178 offset += strlen(imgp->args->fname) + 1; /* fname of script */
179 length = (imgp->args->argc == 0) ? 0 :
180 strlen(imgp->args->begin_argv) + 1; /* bytes to delete */
182 if (offset - length > imgp->args->stringspace)
185 bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
186 imgp->args->endp - (imgp->args->begin_argv + length));
188 offset -= length; /* calculate actual adjustment */
189 imgp->args->begin_envv += offset;
190 imgp->args->endp += offset;
191 imgp->args->stringspace -= offset;
194 * If there was no arg[0] when we started, then the interpreter_name
195 * is adding an argument (instead of replacing the arg[0] we started
196 * with). And we're always adding an argument when we include the
197 * full pathname of the original script.
199 if (imgp->args->argc == 0)
200 imgp->args->argc = 1;
204 * The original arg[] list has been shifted appropriately. Copy in
205 * the interpreter name and options-string.
207 length = interpe - interpb;
208 bcopy(interpb, imgp->args->buf, length);
209 *(imgp->args->buf + length) = '\0';
212 length = opte - optb;
213 bcopy(optb, imgp->args->buf + offset, length);
214 *(imgp->args->buf + offset + length) = '\0';
215 offset += length + 1;
220 * Finally, add the filename onto the end for the interpreter to
221 * use and copy the interpreter's name to imgp->interpreter_name
224 error = copystr(imgp->args->fname, imgp->args->buf + offset,
225 imgp->args->stringspace, &length);
228 error = copystr(imgp->args->begin_argv, imgp->interpreter_name,
229 MAXSHELLCMDLEN, &length);
235 * Tell kern_execve.c about it, with a little help from the linker.
237 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
238 EXEC_SET(shell, shell_execsw);