1 /* vi: set sw=4 ts=4: */
2 /*
3 * setlogcons: Send kernel messages to the current console or to console N
4 *
5 * Copyright (C) 2006 by Jan Kiszka <jan.kiszka@web.de>
6 *
7 * Based on setlogcons (kbd-1.12) by Andries E. Brouwer
8 *
9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
10 */
11 //config:config SETLOGCONS
12 //config: bool "setlogcons (1.8 kb)"
13 //config: default y
14 //config: help
15 //config: This program redirects the output console of kernel messages.
16
17 //applet:IF_SETLOGCONS(APPLET_NOEXEC(setlogcons, setlogcons, BB_DIR_USR_SBIN, BB_SUID_DROP, setlogcons))
18
19 //kbuild:lib-$(CONFIG_SETLOGCONS) += setlogcons.o
20
21 //usage:#define setlogcons_trivial_usage
22 //usage: "[N]"
23 //usage:#define setlogcons_full_usage "\n\n"
24 //usage: "Pin kernel output to VT console N. Default:0 (do not pin)"
25
26 // Comment from kernel source:
27 /* ...
28 * By default, the kernel messages are always printed on the current virtual
29 * console. However, the user may modify that default with the
30 * TIOCL_SETKMSGREDIRECT ioctl call.
31 *
32 * This function sets the kernel message console to be @new. It returns the old
33 * virtual console number. The virtual terminal number 0 (both as parameter and
34 * return value) means no redirection (i.e. always printed on the currently
35 * active console).
36 */
37
38 #include "libbb.h"
39
40 int setlogcons_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
setlogcons_main(int argc UNUSED_PARAM,char ** argv)41 int setlogcons_main(int argc UNUSED_PARAM, char **argv)
42 {
43 char *devname;
44 struct {
45 char fn;
46 char subarg;
47 } arg = {
48 11, /* redirect kernel messages (TIOCL_SETKMSGREDIRECT) */
49 0
50 };
51
52 if (argv[1])
53 arg.subarg = xatou_range(argv[1], 0, 63);
54
55 /* Can just call it on "/dev/tty1" always, but...
56 * in my testing, inactive (never opened) VTs are not
57 * redirected to, despite ioctl not failing.
58 *
59 * By using "/dev/ttyN", ensure it is activated.
60 */
61 devname = xasprintf("/dev/tty%u", arg.subarg);
62 xioctl(xopen(devname, O_RDONLY), TIOCLINUX, &arg);
63
64 return EXIT_SUCCESS;
65 }
66