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"
12 //config: default y
13 //config: select PLATFORM_LINUX
14 //config: help
15 //config: This program is used to start a command on an unused
16 //config: virtual terminal.
17
18 //applet:IF_OPENVT(APPLET(openvt, BB_DIR_USR_BIN, BB_SUID_DROP))
19
20 //kbuild:lib-$(CONFIG_OPENVT) += openvt.o
21
22 //usage:#define openvt_trivial_usage
23 //usage: "[-c N] [-sw] [PROG ARGS]"
24 //usage:#define openvt_full_usage "\n\n"
25 //usage: "Start PROG on a new virtual terminal\n"
26 //usage: "\n -c N Use specified VT"
27 //usage: "\n -s Switch to the VT"
28 /* //usage: "\n -l Run PROG as login shell (by prepending '-')" */
29 //usage: "\n -w Wait for PROG to exit"
30 //usage:
31 //usage:#define openvt_example_usage
32 //usage: "openvt 2 /bin/ash\n"
33
34 #include <linux/vt.h>
35 #include "libbb.h"
36
37 /* "Standard" openvt's man page (we do not support all of this):
38
39 openvt [-c NUM] [-fsulv] [--] [command [args]]
40
41 Find the first available VT, and run command on it. Stdio is directed
42 to that VT. If no command is specified then $SHELL is used.
43
44 -c NUM
45 Use the given VT number, not the first free one.
46 -f
47 Force opening a VT: don't try to check if VT is already in use.
48 -s
49 Switch to the new VT when starting the command.
50 The VT of the new command will be made the new current VT.
51 -u
52 Figure out the owner of the current VT, and run login as that user.
53 Suitable to be called by init. Shouldn't be used with -c or -l.
54 -l
55 Make the command a login shell: a "-" is prepended to the argv[0]
56 when command is executed.
57 -v
58 Verbose.
59 -w
60 Wait for command to complete. If -w and -s are used together,
61 switch back to the controlling terminal when the command completes.
62
63 bbox:
64 -u: not implemented
65 -f: always in effect
66 -l: not implemented, ignored
67 -v: ignored
68 -ws: does NOT switch back
69 */
70
71 /* Helper: does this fd understand VT_xxx? */
not_vt_fd(int fd)72 static int not_vt_fd(int fd)
73 {
74 struct vt_stat vtstat;
75 return ioctl(fd, VT_GETSTATE, &vtstat); /* !0: error, it's not VT fd */
76 }
77
78 /* Helper: get a fd suitable for VT_xxx */
get_vt_fd(void)79 static int get_vt_fd(void)
80 {
81 int fd;
82
83 /* Do we, by chance, already have it? */
84 for (fd = 0; fd < 3; fd++)
85 if (!not_vt_fd(fd))
86 return fd;
87 fd = open(DEV_CONSOLE, O_RDONLY | O_NONBLOCK);
88 if (fd >= 0 && !not_vt_fd(fd))
89 return fd;
90 bb_error_msg_and_die("can't find open VT");
91 }
92
find_free_vtno(void)93 static int find_free_vtno(void)
94 {
95 int vtno;
96 int fd = get_vt_fd();
97
98 errno = 0;
99 /*xfunc_error_retval = 3; - do we need compat? */
100 if (ioctl(fd, VT_OPENQRY, &vtno) != 0 || vtno <= 0)
101 bb_perror_msg_and_die("can't find open VT");
102 // Not really needed, grep for DAEMON_ONLY_SANITIZE
103 // if (fd > 2)
104 // close(fd);
105 return vtno;
106 }
107
108 /* vfork scares gcc, it generates bigger code.
109 * Keep it away from main program.
110 * TODO: move to libbb; or adapt existing libbb's spawn().
111 */
vfork_child(char ** argv)112 static NOINLINE void vfork_child(char **argv)
113 {
114 if (vfork() == 0) {
115 /* CHILD */
116 /* Try to make this VT our controlling tty */
117 setsid(); /* lose old ctty */
118 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /* 0: don't forcibly steal */);
119 //bb_error_msg("our sid %d", getsid(0));
120 //bb_error_msg("our pgrp %d", getpgrp());
121 //bb_error_msg("VT's sid %d", tcgetsid(0));
122 //bb_error_msg("VT's pgrp %d", tcgetpgrp(0));
123 BB_EXECVP_or_die(argv);
124 }
125 }
126
127 int openvt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
openvt_main(int argc UNUSED_PARAM,char ** argv)128 int openvt_main(int argc UNUSED_PARAM, char **argv)
129 {
130 char vtname[sizeof(VC_FORMAT) + sizeof(int)*3];
131 struct vt_stat vtstat;
132 char *str_c;
133 int vtno;
134 int flags;
135 enum {
136 OPT_c = (1 << 0),
137 OPT_w = (1 << 1),
138 OPT_s = (1 << 2),
139 OPT_l = (1 << 3),
140 OPT_f = (1 << 4),
141 OPT_v = (1 << 5),
142 };
143
144 /* "+" - stop on first non-option */
145 flags = getopt32(argv, "+c:wslfv", &str_c);
146 argv += optind;
147
148 if (flags & OPT_c) {
149 /* Check for illegal vt number: < 1 or > 63 */
150 vtno = xatou_range(str_c, 1, 63);
151 } else {
152 vtno = find_free_vtno();
153 }
154
155 /* Grab new VT */
156 sprintf(vtname, VC_FORMAT, vtno);
157 /* (Try to) clean up stray open fds above fd 2 */
158 bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS | DAEMON_ONLY_SANITIZE, NULL);
159 close(STDIN_FILENO);
160 /*setsid(); - BAD IDEA: after we exit, child is SIGHUPed... */
161 xopen(vtname, O_RDWR);
162 xioctl(STDIN_FILENO, VT_GETSTATE, &vtstat);
163
164 if (flags & OPT_s) {
165 console_make_active(STDIN_FILENO, vtno);
166 }
167
168 if (!argv[0]) {
169 argv--;
170 argv[0] = (char *) get_shell_name();
171 /*argv[1] = NULL; - already is */
172 }
173
174 xdup2(STDIN_FILENO, STDOUT_FILENO);
175 xdup2(STDIN_FILENO, STDERR_FILENO);
176
177 #ifdef BLOAT
178 {
179 /* Handle -l (login shell) option */
180 const char *prog = argv[0];
181 if (flags & OPT_l)
182 argv[0] = xasprintf("-%s", argv[0]);
183 }
184 #endif
185
186 vfork_child(argv);
187 if (flags & OPT_w) {
188 /* We have only one child, wait for it */
189 safe_waitpid(-1, NULL, 0); /* loops on EINTR */
190 if (flags & OPT_s) {
191 console_make_active(STDIN_FILENO, vtstat.v_active);
192 // Compat: even with -c N (try to) disallocate:
193 // # /usr/app/kbd-1.12/bin/openvt -f -c 9 -ws sleep 5
194 // openvt: could not deallocate console 9
195 xioctl(STDIN_FILENO, VT_DISALLOCATE, (void*)(ptrdiff_t)vtno);
196 }
197 }
198 return EXIT_SUCCESS;
199 }
200