356 lines
9.4 KiB
C
356 lines
9.4 KiB
C
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#define _GNU_SOURCE 1
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#include <errno.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <stdarg.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stropts.h>
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#include <sys/ioctl.h>
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#include <sys/stat.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <termios.h>
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#include <unistd.h>
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static void
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fail_io (const char *msg, ...)
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__attribute__ ((noreturn))
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__attribute__ ((format (printf, 1, 2)));
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/* Prints MSG, formatting as with printf(),
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plus an error message based on errno,
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and exits. */
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static void
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fail_io (const char *msg, ...)
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{
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va_list args;
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va_start (args, msg);
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vfprintf (stderr, msg, args);
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va_end (args);
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if (errno != 0)
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fprintf (stderr, ": %s", strerror (errno));
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putc ('\n', stderr);
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exit (EXIT_FAILURE);
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}
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/* If FD is a terminal, configures it for noncanonical input mode
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with VMIN and VTIME set as indicated.
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If FD is not a terminal, has no effect. */
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static void
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make_noncanon (int fd, int vmin, int vtime)
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{
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if (isatty (fd))
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{
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struct termios termios;
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if (tcgetattr (fd, &termios) < 0)
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fail_io ("tcgetattr");
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termios.c_lflag &= ~(ICANON | ECHO);
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termios.c_cc[VMIN] = vmin;
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termios.c_cc[VTIME] = vtime;
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if (tcsetattr (fd, TCSANOW, &termios) < 0)
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fail_io ("tcsetattr");
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}
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}
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/* Make FD non-blocking if NONBLOCKING is true,
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or blocking if NONBLOCKING is false. */
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static void
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make_nonblocking (int fd, bool nonblocking)
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{
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int flags = fcntl (fd, F_GETFL);
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if (flags < 0)
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fail_io ("fcntl");
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if (nonblocking)
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flags |= O_NONBLOCK;
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else
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flags &= ~O_NONBLOCK;
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if (fcntl (fd, F_SETFL, flags) < 0)
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fail_io ("fcntl");
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}
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/* Handle a read or write on *FD, which is the pty if FD_IS_PTY
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is true, that returned end-of-file or error indication RETVAL.
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The system call is named CALL, for use in error messages.
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Returns true if processing may continue, false if we're all
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done. */
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static bool
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handle_error (ssize_t retval, int *fd, bool fd_is_pty, const char *call)
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{
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if (fd_is_pty)
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{
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if (retval < 0)
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{
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if (errno == EIO)
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{
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/* Slave side of pty has been closed. */
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return false;
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}
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else
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fail_io (call);
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}
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else
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return true;
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}
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else
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{
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if (retval == 0)
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{
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close (*fd);
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*fd = -1;
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return true;
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}
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else
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fail_io (call);
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}
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}
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/* Copies data from stdin to PTY and from PTY to stdout until no
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more data can be read or written. */
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static void
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relay (int pty, int dead_child_fd)
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{
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struct pipe
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{
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int in, out;
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char buf[BUFSIZ];
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size_t size, ofs;
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bool active;
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};
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struct pipe pipes[2];
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/* Make PTY, stdin, and stdout non-blocking. */
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make_nonblocking (pty, true);
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make_nonblocking (STDIN_FILENO, true);
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make_nonblocking (STDOUT_FILENO, true);
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/* Configure noncanonical mode on PTY and stdin to avoid
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waiting for end-of-line. We want to minimize context
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switching on PTY (for efficiency) and minimize latency on
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stdin to avoid a laggy user experience. */
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make_noncanon (pty, 16, 1);
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make_noncanon (STDIN_FILENO, 1, 0);
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memset (pipes, 0, sizeof pipes);
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pipes[0].in = STDIN_FILENO;
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pipes[0].out = pty;
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pipes[1].in = pty;
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pipes[1].out = STDOUT_FILENO;
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while (pipes[0].in != -1 || pipes[1].in != -1)
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{
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fd_set read_fds, write_fds;
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int retval;
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int i;
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FD_ZERO (&read_fds);
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FD_ZERO (&write_fds);
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for (i = 0; i < 2; i++)
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{
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struct pipe *p = &pipes[i];
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/* Don't do anything with the stdin->pty pipe until we
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have some data for the pty->stdout pipe. If we get
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too eager, Bochs will throw away our input. */
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if (i == 0 && !pipes[1].active)
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continue;
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if (p->in != -1 && p->size + p->ofs < sizeof p->buf)
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FD_SET (p->in, &read_fds);
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if (p->out != -1 && p->size > 0)
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FD_SET (p->out, &write_fds);
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}
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FD_SET (dead_child_fd, &read_fds);
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do
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{
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retval = select (FD_SETSIZE, &read_fds, &write_fds, NULL, NULL);
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}
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while (retval < 0 && errno == EINTR);
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if (retval < 0)
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fail_io ("select");
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if (FD_ISSET (dead_child_fd, &read_fds))
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{
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/* Child died. Do final relaying. */
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struct pipe *p = &pipes[1];
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if (p->out == -1)
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return;
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make_nonblocking (STDOUT_FILENO, false);
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for (;;)
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{
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ssize_t n;
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/* Write buffer. */
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while (p->size > 0)
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{
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n = write (p->out, p->buf + p->ofs, p->size);
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if (n < 0)
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fail_io ("write");
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else if (n == 0)
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fail_io ("zero-length write");
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p->ofs += n;
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p->size -= n;
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}
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p->ofs = 0;
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p->size = n = read (p->in, p->buf, sizeof p->buf);
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if (n <= 0)
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return;
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}
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}
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for (i = 0; i < 2; i++)
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{
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struct pipe *p = &pipes[i];
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if (p->in != -1 && FD_ISSET (p->in, &read_fds))
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{
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ssize_t n = read (p->in, p->buf + p->ofs + p->size,
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sizeof p->buf - p->ofs - p->size);
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if (n > 0)
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{
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p->active = true;
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p->size += n;
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if (p->size == BUFSIZ && p->ofs != 0)
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{
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memmove (p->buf, p->buf + p->ofs, p->size);
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p->ofs = 0;
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}
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}
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else if (!handle_error (n, &p->in, p->in == pty, "read"))
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return;
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}
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if (p->out != -1 && FD_ISSET (p->out, &write_fds))
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{
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ssize_t n = write (p->out, p->buf + p->ofs, p->size);
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if (n > 0)
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{
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p->ofs += n;
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p->size -= n;
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if (p->size == 0)
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p->ofs = 0;
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}
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else if (!handle_error (n, &p->out, p->out == pty, "write"))
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return;
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}
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}
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}
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}
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static int dead_child_fd;
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static void
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sigchld_handler (int signo __attribute__ ((unused)))
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{
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if (write (dead_child_fd, "", 1) < 0)
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_exit (1);
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}
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int
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main (int argc __attribute__ ((unused)), char *argv[])
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{
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int master, slave;
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char *name;
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pid_t pid;
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struct sigaction sa;
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int pipe_fds[2];
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struct itimerval zero_itimerval, old_itimerval;
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if (argc < 2)
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{
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fprintf (stderr,
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"usage: squish-pty COMMAND [ARG]...\n"
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"Squishes both stdin and stdout into a single pseudoterminal,\n"
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"which is passed as stdout to run the specified COMMAND.\n");
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return EXIT_FAILURE;
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}
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/* Open master side of pty and get ready to open slave. */
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master = open ("/dev/ptmx", O_RDWR | O_NOCTTY);
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if (master < 0)
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fail_io ("open \"/dev/ptmx\"");
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if (grantpt (master) < 0)
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fail_io ("grantpt");
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if (unlockpt (master) < 0)
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fail_io ("unlockpt");
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/* Open slave side of pty. */
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name = ptsname (master);
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if (name == NULL)
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fail_io ("ptsname");
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slave = open (name, O_RDWR);
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if (slave < 0)
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fail_io ("open \"%s\"", name);
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/* System V implementations need STREAMS configuration for the
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slave. */
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if (isastream (slave))
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{
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if (ioctl (slave, I_PUSH, "ptem") < 0
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|| ioctl (slave, I_PUSH, "ldterm") < 0)
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fail_io ("ioctl");
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}
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/* Arrange to get notified when a child dies, by writing a byte
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to a pipe fd. We really want to use pselect() and
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sigprocmask(), but Solaris 2.7 doesn't have it. */
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if (pipe (pipe_fds) < 0)
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fail_io ("pipe");
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dead_child_fd = pipe_fds[1];
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memset (&sa, 0, sizeof sa);
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sa.sa_handler = sigchld_handler;
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sigemptyset (&sa.sa_mask);
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sa.sa_flags = SA_RESTART;
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if (sigaction (SIGCHLD, &sa, NULL) < 0)
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fail_io ("sigaction");
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/* Save the virtual interval timer, which might have been set
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by the process that ran us. It really should be applied to
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our child process. */
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memset (&zero_itimerval, 0, sizeof zero_itimerval);
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if (setitimer (ITIMER_VIRTUAL, &zero_itimerval, &old_itimerval) < 0)
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fail_io ("setitimer");
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pid = fork ();
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if (pid < 0)
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fail_io ("fork");
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else if (pid != 0)
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{
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/* Running in parent process. */
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int status;
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close (slave);
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relay (master, pipe_fds[0]);
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/* If the subprocess has died, die in the same fashion.
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In particular, dying from SIGVTALRM tells the pintos
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script that we ran out of CPU time. */
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if (waitpid (pid, &status, WNOHANG) > 0)
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{
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if (WIFEXITED (status))
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return WEXITSTATUS (status);
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else if (WIFSIGNALED (status))
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raise (WTERMSIG (status));
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}
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return 0;
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}
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else
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{
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/* Running in child process. */
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if (setitimer (ITIMER_VIRTUAL, &old_itimerval, NULL) < 0)
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fail_io ("setitimer");
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if (dup2 (slave, STDOUT_FILENO) < 0)
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fail_io ("dup2");
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if (close (pipe_fds[0]) < 0 || close (pipe_fds[1]) < 0
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|| close (slave) < 0 || close (master) < 0)
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fail_io ("close");
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execvp (argv[1], argv + 1);
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fail_io ("exec");
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}
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}
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