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