[3320] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Copyright (c) 2007 Denys Vlasenko <vda.linux@googlemail.com>
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| 4 | *
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| 5 | * Licensed under GPLv2, see file LICENSE in this source tree.
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| 6 | */
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| 7 | #include "libbb.h"
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| 8 |
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| 9 | //applet:IF_CTTYHACK(APPLET(cttyhack, _BB_DIR_BIN, _BB_SUID_DROP))
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| 10 |
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| 11 | //kbuild:lib-$(CONFIG_CTTYHACK) += cttyhack.o
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| 12 |
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| 13 | //config:config CTTYHACK
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| 14 | //config: bool "cttyhack"
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| 15 | //config: default y
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| 16 | //config: help
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| 17 | //config: One common problem reported on the mailing list is "can't access tty;
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| 18 | //config: job control turned off" error message which typically appears when
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| 19 | //config: one tries to use shell with stdin/stdout opened to /dev/console.
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| 20 | //config: This device is special - it cannot be a controlling tty.
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| 21 | //config:
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| 22 | //config: Proper solution is to use correct device instead of /dev/console.
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| 23 | //config:
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| 24 | //config: cttyhack provides "quick and dirty" solution to this problem.
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| 25 | //config: It analyzes stdin with various ioctls, trying to determine whether
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| 26 | //config: it is a /dev/ttyN or /dev/ttySN (virtual terminal or serial line).
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| 27 | //config: If it detects one, it closes stdin/out/err and reopens that device.
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| 28 | //config: Then it executes given program. Opening the device will make
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| 29 | //config: that device a controlling tty. This may require cttyhack
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| 30 | //config: to be a session leader.
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| 31 | //config:
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| 32 | //config: Example for /etc/inittab (for busybox init):
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| 33 | //config:
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| 34 | //config: ::respawn:/bin/cttyhack /bin/sh
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| 35 | //config:
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| 36 | //config: Starting an interactive shell from boot shell script:
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| 37 | //config:
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| 38 | //config: setsid cttyhack sh
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| 39 | //config:
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| 40 | //config: Giving controlling tty to shell running with PID 1:
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| 41 | //config:
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| 42 | //config: # exec cttyhack sh
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| 43 | //config:
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| 44 | //config: Without cttyhack, you need to know exact tty name,
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| 45 | //config: and do something like this:
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| 46 | //config:
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| 47 | //config: # exec setsid sh -c 'exec sh </dev/tty1 >/dev/tty1 2>&1'
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| 48 | //config:
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| 49 |
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| 50 | //usage:#define cttyhack_trivial_usage
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| 51 | //usage: "PROG ARGS"
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| 52 | //usage:#define cttyhack_full_usage "\n\n"
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| 53 | //usage: "Give PROG a controlling tty if possible."
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| 54 | //usage: "\nExample for /etc/inittab (for busybox init):"
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| 55 | //usage: "\n ::respawn:/bin/cttyhack /bin/sh"
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| 56 | //usage: "\nGiving controlling tty to shell running with PID 1:"
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| 57 | //usage: "\n $ exec cttyhack sh"
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| 58 | //usage: "\nStarting interactive shell from boot shell script:"
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| 59 | //usage: "\n setsid cttyhack sh"
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| 60 |
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| 61 | #if !defined(__linux__) && !defined(TIOCGSERIAL) && !ENABLE_WERROR
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| 62 | # warning cttyhack will not be able to detect a controlling tty on this system
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| 63 | #endif
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| 64 |
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| 65 | /* From <linux/vt.h> */
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| 66 | struct vt_stat {
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| 67 | unsigned short v_active; /* active vt */
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| 68 | unsigned short v_signal; /* signal to send */
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| 69 | unsigned short v_state; /* vt bitmask */
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| 70 | };
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| 71 | enum { VT_GETSTATE = 0x5603 }; /* get global vt state info */
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| 72 |
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| 73 | /* From <linux/serial.h> */
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| 74 | struct serial_struct {
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| 75 | int type;
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| 76 | int line;
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| 77 | unsigned int port;
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| 78 | int irq;
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| 79 | int flags;
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| 80 | int xmit_fifo_size;
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| 81 | int custom_divisor;
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| 82 | int baud_base;
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| 83 | unsigned short close_delay;
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| 84 | char io_type;
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| 85 | char reserved_char[1];
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| 86 | int hub6;
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| 87 | unsigned short closing_wait; /* time to wait before closing */
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| 88 | unsigned short closing_wait2; /* no longer used... */
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| 89 | unsigned char *iomem_base;
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| 90 | unsigned short iomem_reg_shift;
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| 91 | unsigned int port_high;
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| 92 | unsigned long iomap_base; /* cookie passed into ioremap */
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| 93 | int reserved[1];
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| 94 | };
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| 95 |
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| 96 | int cttyhack_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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| 97 | int cttyhack_main(int argc UNUSED_PARAM, char **argv)
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| 98 | {
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| 99 | int fd;
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| 100 | char console[sizeof(int)*3 + 16];
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| 101 | union {
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| 102 | struct vt_stat vt;
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| 103 | struct serial_struct sr;
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| 104 | char paranoia[sizeof(struct serial_struct) * 3];
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| 105 | } u;
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| 106 |
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| 107 | if (!*++argv) {
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| 108 | bb_show_usage();
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| 109 | }
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| 110 |
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| 111 | strcpy(console, "/dev/tty");
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| 112 | fd = open(console, O_RDWR);
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| 113 | if (fd >= 0) {
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| 114 | /* We already have ctty, nothing to do */
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| 115 | close(fd);
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| 116 | } else {
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| 117 | /* We don't have ctty (or don't have "/dev/tty" node...) */
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| 118 | if (0) {}
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| 119 | #ifdef TIOCGSERIAL
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| 120 | else if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
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| 121 | /* this is a serial console */
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| 122 | sprintf(console + 8, "S%d", u.sr.line);
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| 123 | }
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| 124 | #endif
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| 125 | #ifdef __linux__
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| 126 | else if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
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| 127 | /* this is linux virtual tty */
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| 128 | sprintf(console + 8, "S%d" + 1, u.vt.v_active);
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| 129 | }
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| 130 | #endif
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| 131 | if (console[8]) {
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| 132 | fd = xopen(console, O_RDWR);
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| 133 | //bb_error_msg("switching to '%s'", console);
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| 134 | dup2(fd, 0);
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| 135 | dup2(fd, 1);
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| 136 | dup2(fd, 2);
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| 137 | while (fd > 2)
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| 138 | close(fd--);
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| 139 | /* Some other session may have it as ctty,
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| 140 | * steal it from them:
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| 141 | */
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| 142 | ioctl(0, TIOCSCTTY, 1);
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| 143 | }
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| 144 | }
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| 145 |
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| 146 | BB_EXECVP_or_die(argv);
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| 147 | }
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