1 /* vi: set sw=4 ts=4: */
2 /*
3 * openvt.c - open a vt to run a command.
4 *
5 * busyboxed by Quy Tonthat <quy@signal3.com>
6 * hacked by Tito <farmatito@tiscali.it>
7 *
8 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
9 */
10 //config:config OPENVT
11 //config: bool "openvt (7.2 kb)"
12 //config: default y
13 //config: help
14 //config: This program is used to start a command on an unused
15 //config: virtual terminal.
16
17 //applet:IF_OPENVT(APPLET(openvt, BB_DIR_USR_BIN, BB_SUID_DROP))
18
19 //kbuild:lib-$(CONFIG_OPENVT) += openvt.o
20
21 //usage:#define openvt_trivial_usage
22 //usage: "[-c N] [-sw] [PROG ARGS]"
23 //usage:#define openvt_full_usage "\n\n"
24 //usage: "Start PROG on a new virtual terminal\n"
25 //usage: "\n -c N Use specified VT"
26 //usage: "\n -s Switch to the VT"
27 /* //usage: "\n -l Run PROG as login shell (by prepending '-')" */
28 //usage: "\n -w Wait for PROG to exit"
29 //usage:
30 //usage:#define openvt_example_usage
31 //usage: "openvt 2 /bin/ash\n"
32
33 #include <linux/vt.h>
34 #include "libbb.h"
35
36 /* "Standard" openvt's man page (we do not support all of this):
37
38 openvt [-c NUM] [-fsulv] [--] [command [args]]
39
40 Find the first available VT, and run command on it. Stdio is directed
41 to that VT. If no command is specified then $SHELL is used.
42
43 -c NUM
44 Use the given VT number, not the first free one.
45 -f
46 Force opening a VT: don't try to check if VT is already in use.
47 -s
48 Switch to the new VT when starting the command.
49 The VT of the new command will be made the new current VT.
50 -u
51 Figure out the owner of the current VT, and run login as that user.
52 Suitable to be called by init. Shouldn't be used with -c or -l.
53 -l
54 Make the command a login shell: a "-" is prepended to the argv[0]
55 when command is executed.
56 -v
57 Verbose.
58 -w
59 Wait for command to complete. If -w and -s are used together,
60 switch back to the controlling terminal when the command completes.
61
62 bbox:
63 -u: not implemented
64 -f: always in effect
65 -l: not implemented, ignored
66 -v: ignored
67 -ws: does NOT switch back
68 */
69
70 /* Helper: does this fd understand VT_xxx? */
not_vt_fd(int fd)71 static int not_vt_fd(int fd)
72 {
73 struct vt_stat vtstat;
74 return ioctl(fd, VT_GETSTATE, &vtstat); /* !0: error, it's not VT fd */
75 }
76
77 /* Helper: get a fd suitable for VT_xxx */
get_vt_fd(void)78 static int get_vt_fd(void)
79 {
80 int fd;
81
82 /* Do we, by chance, already have it? */
83 for (fd = 0; fd < 3; fd++)
84 if (!not_vt_fd(fd))
85 return fd;
86 fd = open(DEV_CONSOLE, O_RDONLY | O_NONBLOCK);
87 if (fd >= 0 && !not_vt_fd(fd))
88 return fd;
89 bb_simple_error_msg_and_die("can't find open VT");
90 }
91
find_free_vtno(void)92 static int find_free_vtno(void)
93 {
94 int vtno;
95 int fd = get_vt_fd();
96
97 errno = 0;
98 /*xfunc_error_retval = 3; - do we need compat? */
99 if (ioctl(fd, VT_OPENQRY, &vtno) != 0 || vtno <= 0)
100 bb_simple_perror_msg_and_die("can't find open VT");
101 // Not really needed, grep for DAEMON_CLOSE_EXTRA_FDS
102 // if (fd > 2)
103 // close(fd);
104 return vtno;
105 }
106
107 /* vfork scares gcc, it generates bigger code.
108 * Keep it away from main program.
109 * TODO: move to libbb; or adapt existing libbb's spawn().
110 */
vfork_child(char ** argv)111 static NOINLINE void vfork_child(char **argv)
112 {
113 if (vfork() == 0) {
114 /* CHILD */
115 /* Try to make this VT our controlling tty */
116 setsid(); /* lose old ctty */
117 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /* 0: don't forcibly steal */);
118 //bb_error_msg("our sid %d", getsid(0));
119 //bb_error_msg("our pgrp %d", getpgrp());
120 //bb_error_msg("VT's sid %d", tcgetsid(0));
121 //bb_error_msg("VT's pgrp %d", tcgetpgrp(0));
122 BB_EXECVP_or_die(argv);
123 }
124 }
125
126 int openvt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
openvt_main(int argc UNUSED_PARAM,char ** argv)127 int openvt_main(int argc UNUSED_PARAM, char **argv)
128 {
129 char vtname[sizeof(VC_FORMAT) + sizeof(int)*3];
130 struct vt_stat vtstat;
131 char *str_c;
132 int vtno;
133 int flags;
134 enum {
135 OPT_c = (1 << 0),
136 OPT_w = (1 << 1),
137 OPT_s = (1 << 2),
138 OPT_l = (1 << 3),
139 OPT_f = (1 << 4),
140 OPT_v = (1 << 5),
141 };
142
143 /* "+" - stop on first non-option */
144 flags = getopt32(argv, "+c:wslfv", &str_c);
145 argv += optind;
146
147 if (flags & OPT_c) {
148 /* Check for illegal vt number: < 1 or > 63 */
149 vtno = xatou_range(str_c, 1, 63);
150 } else {
151 vtno = find_free_vtno();
152 }
153
154 /* Grab new VT */
155 sprintf(vtname, VC_FORMAT, vtno);
156 /* (Try to) clean up stray open fds above fd 2 */
157 bb_daemon_helper(DAEMON_CLOSE_EXTRA_FDS);
158 close(STDIN_FILENO);
159 /*setsid(); - BAD IDEA: after we exit, child is SIGHUPed... */
160 xopen(vtname, O_RDWR);
161 xioctl(STDIN_FILENO, VT_GETSTATE, &vtstat);
162
163 if (flags & OPT_s) {
164 console_make_active(STDIN_FILENO, vtno);
165 }
166
167 if (!argv[0]) {
168 argv--;
169 argv[0] = (char *) get_shell_name();
170 /*argv[1] = NULL; - already is */
171 }
172
173 xdup2(STDIN_FILENO, STDOUT_FILENO);
174 xdup2(STDIN_FILENO, STDERR_FILENO);
175
176 #ifdef BLOAT
177 {
178 /* Handle -l (login shell) option */
179 const char *prog = argv[0];
180 if (flags & OPT_l)
181 argv[0] = xasprintf("-%s", argv[0]);
182 }
183 #endif
184
185 vfork_child(argv);
186 if (flags & OPT_w) {
187 /* We have only one child, wait for it */
188 safe_waitpid(-1, NULL, 0); /* loops on EINTR */
189 if (flags & OPT_s) {
190 console_make_active(STDIN_FILENO, vtstat.v_active);
191 // Compat: even with -c N (try to) disallocate:
192 // # /usr/app/kbd-1.12/bin/openvt -f -c 9 -ws sleep 5
193 // openvt: could not deallocate console 9
194 xioctl(STDIN_FILENO, VT_DISALLOCATE, (void*)(ptrdiff_t)vtno);
195 }
196 }
197 return EXIT_SUCCESS;
198 }
199