| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com) |
| 4 | */ |
| 5 | |
| 6 | #include <stdlib.h> |
| 7 | #include <unistd.h> |
| 8 | #include <errno.h> |
| 9 | #include <sched.h> |
| 10 | #include <signal.h> |
| 11 | #include <termios.h> |
| 12 | #include <sys/ioctl.h> |
| 13 | #include "chan_user.h" |
| 14 | #include <os.h> |
| 15 | #include <um_malloc.h> |
| 16 | |
| 17 | void generic_close(int fd, void *unused) |
| 18 | { |
| 19 | close(fd); |
| 20 | } |
| 21 | |
| 22 | int generic_read(int fd, __u8 *c_out, void *unused) |
| 23 | { |
| 24 | int n; |
| 25 | |
| 26 | CATCH_EINTR(n = read(fd, c_out, sizeof(*c_out))); |
| 27 | if (n > 0) |
| 28 | return n; |
| 29 | else if (n == 0) |
| 30 | return -EIO; |
| 31 | else if (errno == EAGAIN) |
| 32 | return 0; |
| 33 | return -errno; |
| 34 | } |
| 35 | |
| 36 | /* XXX Trivial wrapper around write */ |
| 37 | |
| 38 | int generic_write(int fd, const __u8 *buf, size_t n, void *unused) |
| 39 | { |
| 40 | int written = 0; |
| 41 | int err; |
| 42 | |
| 43 | /* The FD may be in blocking mode, as such, need to retry short writes, |
| 44 | * they may have been interrupted by a signal. |
| 45 | */ |
| 46 | do { |
| 47 | errno = 0; |
| 48 | err = write(fd, buf + written, n - written); |
| 49 | if (err > 0) { |
| 50 | written += err; |
| 51 | continue; |
| 52 | } |
| 53 | } while (err < 0 && errno == EINTR); |
| 54 | |
| 55 | if (written > 0) |
| 56 | return written; |
| 57 | else if (errno == EAGAIN) |
| 58 | return 0; |
| 59 | else if (err == 0) |
| 60 | return -EIO; |
| 61 | return -errno; |
| 62 | } |
| 63 | |
| 64 | int generic_window_size(int fd, void *unused, unsigned short *rows_out, |
| 65 | unsigned short *cols_out) |
| 66 | { |
| 67 | struct winsize size; |
| 68 | int ret; |
| 69 | |
| 70 | if (ioctl(fd, TIOCGWINSZ, &size) < 0) |
| 71 | return -errno; |
| 72 | |
| 73 | ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col)); |
| 74 | |
| 75 | *rows_out = size.ws_row; |
| 76 | *cols_out = size.ws_col; |
| 77 | |
| 78 | return ret; |
| 79 | } |
| 80 | |
| 81 | void generic_free(void *data) |
| 82 | { |
| 83 | kfree(data); |
| 84 | } |
| 85 | |
| 86 | int generic_console_write(int fd, const char *buf, int n) |
| 87 | { |
| 88 | sigset_t old, no_sigio; |
| 89 | struct termios save, new; |
| 90 | int err; |
| 91 | |
| 92 | if (isatty(fd)) { |
| 93 | sigemptyset(&no_sigio); |
| 94 | sigaddset(&no_sigio, SIGIO); |
| 95 | if (sigprocmask(SIG_BLOCK, &no_sigio, &old)) |
| 96 | goto error; |
| 97 | |
| 98 | CATCH_EINTR(err = tcgetattr(fd, &save)); |
| 99 | if (err) |
| 100 | goto error; |
| 101 | new = save; |
| 102 | /* |
| 103 | * The terminal becomes a bit less raw, to handle \n also as |
| 104 | * "Carriage Return", not only as "New Line". Otherwise, the new |
| 105 | * line won't start at the first column. |
| 106 | */ |
| 107 | new.c_oflag |= OPOST; |
| 108 | CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new)); |
| 109 | if (err) |
| 110 | goto error; |
| 111 | } |
| 112 | err = generic_write(fd, buf, n, NULL); |
| 113 | /* |
| 114 | * Restore raw mode, in any case; we *must* ignore any error apart |
| 115 | * EINTR, except for debug. |
| 116 | */ |
| 117 | if (isatty(fd)) { |
| 118 | CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save)); |
| 119 | sigprocmask(SIG_SETMASK, &old, NULL); |
| 120 | } |
| 121 | |
| 122 | return err; |
| 123 | error: |
| 124 | return -errno; |
| 125 | } |
| 126 | |
| 127 | /* |
| 128 | * UML SIGWINCH handling |
| 129 | * |
| 130 | * The point of this is to handle SIGWINCH on consoles which have host |
| 131 | * ttys and relay them inside UML to whatever might be running on the |
| 132 | * console and cares about the window size (since SIGWINCH notifies |
| 133 | * about terminal size changes). |
| 134 | * |
| 135 | * So, we have a separate thread for each host tty attached to a UML |
| 136 | * device (side-issue - I'm annoyed that one thread can't have |
| 137 | * multiple controlling ttys for the purpose of handling SIGWINCH, but |
| 138 | * I imagine there are other reasons that doesn't make any sense). |
| 139 | * |
| 140 | * SIGWINCH can't be received synchronously, so you have to set up to |
| 141 | * receive it as a signal. That being the case, if you are going to |
| 142 | * wait for it, it is convenient to sit in sigsuspend() and wait for |
| 143 | * the signal to bounce you out of it (see below for how we make sure |
| 144 | * to exit only on SIGWINCH). |
| 145 | */ |
| 146 | |
| 147 | static void winch_handler(int sig) |
| 148 | { |
| 149 | } |
| 150 | |
| 151 | struct winch_data { |
| 152 | int pty_fd; |
| 153 | int pipe_fd; |
| 154 | }; |
| 155 | |
| 156 | static __noreturn int winch_thread(void *arg) |
| 157 | { |
| 158 | struct winch_data *data = arg; |
| 159 | sigset_t sigs; |
| 160 | int pty_fd, pipe_fd; |
| 161 | int count; |
| 162 | char c = 1; |
| 163 | |
| 164 | pty_fd = data->pty_fd; |
| 165 | pipe_fd = data->pipe_fd; |
| 166 | count = write(pipe_fd, &c, sizeof(c)); |
| 167 | if (count != sizeof(c)) |
| 168 | os_info("winch_thread : failed to write synchronization byte, err = %d\n", |
| 169 | -count); |
| 170 | |
| 171 | /* |
| 172 | * We are not using SIG_IGN on purpose, so don't fix it as I thought to |
| 173 | * do! If using SIG_IGN, the sigsuspend() call below would not stop on |
| 174 | * SIGWINCH. |
| 175 | */ |
| 176 | |
| 177 | signal(SIGWINCH, winch_handler); |
| 178 | sigfillset(&sigs); |
| 179 | /* Block all signals possible. */ |
| 180 | if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) { |
| 181 | os_info("winch_thread : sigprocmask failed, errno = %d\n", |
| 182 | errno); |
| 183 | goto wait_kill; |
| 184 | } |
| 185 | /* In sigsuspend(), block anything else than SIGWINCH. */ |
| 186 | sigdelset(&sigs, SIGWINCH); |
| 187 | |
| 188 | if (setsid() < 0) { |
| 189 | os_info("winch_thread : setsid failed, errno = %d\n", |
| 190 | errno); |
| 191 | goto wait_kill; |
| 192 | } |
| 193 | |
| 194 | if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) { |
| 195 | os_info("winch_thread : TIOCSCTTY failed on " |
| 196 | "fd %d err = %d\n", pty_fd, errno); |
| 197 | goto wait_kill; |
| 198 | } |
| 199 | |
| 200 | if (tcsetpgrp(pty_fd, os_getpid()) < 0) { |
| 201 | os_info("winch_thread : tcsetpgrp failed on fd %d err = %d\n", |
| 202 | pty_fd, errno); |
| 203 | goto wait_kill; |
| 204 | } |
| 205 | |
| 206 | /* |
| 207 | * These are synchronization calls between various UML threads on the |
| 208 | * host - since they are not different kernel threads, we cannot use |
| 209 | * kernel semaphores. We don't use SysV semaphores because they are |
| 210 | * persistent. |
| 211 | */ |
| 212 | count = read(pipe_fd, &c, sizeof(c)); |
| 213 | if (count != sizeof(c)) |
| 214 | os_info("winch_thread : failed to read synchronization byte, err = %d\n", |
| 215 | errno); |
| 216 | |
| 217 | while(1) { |
| 218 | /* |
| 219 | * This will be interrupted by SIGWINCH only, since |
| 220 | * other signals are blocked. |
| 221 | */ |
| 222 | sigsuspend(&sigs); |
| 223 | |
| 224 | count = write(pipe_fd, &c, sizeof(c)); |
| 225 | if (count != sizeof(c)) |
| 226 | os_info("winch_thread : write failed, err = %d\n", |
| 227 | errno); |
| 228 | } |
| 229 | |
| 230 | wait_kill: |
| 231 | c = 2; |
| 232 | count = write(pipe_fd, &c, sizeof(c)); |
| 233 | while (1) |
| 234 | pause(); |
| 235 | } |
| 236 | |
| 237 | static int winch_tramp(int fd, struct tty_port *port, int *fd_out, |
| 238 | unsigned long *stack_out) |
| 239 | { |
| 240 | struct winch_data data; |
| 241 | int fds[2], n, err, pid; |
| 242 | char c; |
| 243 | |
| 244 | err = os_pipe(fds, 1, 1); |
| 245 | if (err < 0) { |
| 246 | printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n", |
| 247 | -err); |
| 248 | goto out; |
| 249 | } |
| 250 | |
| 251 | data = ((struct winch_data) { .pty_fd = fd, |
| 252 | .pipe_fd = fds[1] } ); |
| 253 | /* |
| 254 | * CLONE_FILES so this thread doesn't hold open files which are open |
| 255 | * now, but later closed in a different thread. This is a |
| 256 | * problem with /dev/net/tun, which if held open by this |
| 257 | * thread, prevents the TUN/TAP device from being reused. |
| 258 | */ |
| 259 | pid = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out); |
| 260 | if (pid < 0) { |
| 261 | err = pid; |
| 262 | printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n", |
| 263 | -err); |
| 264 | goto out_close; |
| 265 | } |
| 266 | |
| 267 | *fd_out = fds[0]; |
| 268 | n = read(fds[0], &c, sizeof(c)); |
| 269 | if (n != sizeof(c)) { |
| 270 | printk(UM_KERN_ERR "winch_tramp : failed to read " |
| 271 | "synchronization byte\n"); |
| 272 | printk(UM_KERN_ERR "read failed, err = %d\n", errno); |
| 273 | printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd); |
| 274 | err = -EINVAL; |
| 275 | goto out_close; |
| 276 | } |
| 277 | |
| 278 | err = os_set_fd_block(*fd_out, 0); |
| 279 | if (err) { |
| 280 | printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd " |
| 281 | "non-blocking.\n"); |
| 282 | goto out_close; |
| 283 | } |
| 284 | |
| 285 | return pid; |
| 286 | |
| 287 | out_close: |
| 288 | close(fds[1]); |
| 289 | close(fds[0]); |
| 290 | out: |
| 291 | return err; |
| 292 | } |
| 293 | |
| 294 | void register_winch(int fd, struct tty_port *port) |
| 295 | { |
| 296 | unsigned long stack; |
| 297 | int pid, thread, count, thread_fd = -1; |
| 298 | char c = 1; |
| 299 | |
| 300 | if (!isatty(fd)) |
| 301 | return; |
| 302 | |
| 303 | pid = tcgetpgrp(fd); |
| 304 | if (is_skas_winch(pid, fd, port)) { |
| 305 | register_winch_irq(-1, fd, -1, port, 0); |
| 306 | return; |
| 307 | } |
| 308 | |
| 309 | if (pid == -1) { |
| 310 | thread = winch_tramp(fd, port, &thread_fd, &stack); |
| 311 | if (thread < 0) |
| 312 | return; |
| 313 | |
| 314 | register_winch_irq(thread_fd, fd, thread, port, stack); |
| 315 | |
| 316 | count = write(thread_fd, &c, sizeof(c)); |
| 317 | if (count != sizeof(c)) |
| 318 | printk(UM_KERN_ERR "register_winch : failed to write " |
| 319 | "synchronization byte, err = %d\n", errno); |
| 320 | } |
| 321 | } |