1 files changed, 355 insertions, 0 deletions

diff --git a/utils/squish-pty.c b/utils/squish-pty.c
new file mode 100644
index 0000000..c8375a5
--- /dev/null
+++ b/utils/squish-pty.c
@@ -0,0 +1,355 @@
+#define _GNU_SOURCE 1
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stropts.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <termios.h>
+#include <unistd.h>
+
+static void
+fail_io (const char *msg, ...)
+     __attribute__ ((noreturn))
+     __attribute__ ((format (printf, 1, 2)));
+
+/* Prints MSG, formatting as with printf(),
+   plus an error message based on errno,
+   and exits. */
+static void
+fail_io (const char *msg, ...)
+{
+  va_list args;
+
+  va_start (args, msg);
+  vfprintf (stderr, msg, args);
+  va_end (args);
+
+  if (errno != 0)
+    fprintf (stderr, ": %s", strerror (errno));
+  putc ('\n', stderr);
+  exit (EXIT_FAILURE);
+}
+
+/* If FD is a terminal, configures it for noncanonical input mode
+   with VMIN and VTIME set as indicated.
+   If FD is not a terminal, has no effect. */
+static void
+make_noncanon (int fd, int vmin, int vtime)
+{
+  if (isatty (fd)) 
+    {
+      struct termios termios;
+      if (tcgetattr (fd, &termios) < 0)
+        fail_io ("tcgetattr");
+      termios.c_lflag &= ~(ICANON | ECHO);
+      termios.c_cc[VMIN] = vmin;
+      termios.c_cc[VTIME] = vtime;
+      if (tcsetattr (fd, TCSANOW, &termios) < 0)
+        fail_io ("tcsetattr");
+    }
+}
+
+/* Make FD non-blocking if NONBLOCKING is true,
+   or blocking if NONBLOCKING is false. */
+static void
+make_nonblocking (int fd, bool nonblocking) 
+{
+  int flags = fcntl (fd, F_GETFL);
+  if (flags < 0)
+    fail_io ("fcntl");
+  if (nonblocking)
+    flags |= O_NONBLOCK;
+  else
+    flags &= ~O_NONBLOCK;
+  if (fcntl (fd, F_SETFL, flags) < 0)
+    fail_io ("fcntl");
+}
+
+/* Handle a read or write on *FD, which is the pty if FD_IS_PTY
+   is true, that returned end-of-file or error indication RETVAL.
+   The system call is named CALL, for use in error messages.
+   Returns true if processing may continue, false if we're all
+   done. */
+static bool
+handle_error (ssize_t retval, int *fd, bool fd_is_pty, const char *call)
+{
+  if (fd_is_pty)
+    {
+      if (retval < 0)
+        {
+          if (errno == EIO)
+            {
+              /* Slave side of pty has been closed. */
+              return false;
+            }
+          else
+            fail_io (call); 
+        }
+      else
+        return true;
+    }
+  else 
+    {
+      if (retval == 0)
+        {
+          close (*fd);
+          *fd = -1;
+          return true;
+        }
+      else
+        fail_io (call);
+    }
+}
+
+/* Copies data from stdin to PTY and from PTY to stdout until no
+   more data can be read or written. */
+static void
+relay (int pty, int dead_child_fd) 
+{
+  struct pipe 
+    {
+      int in, out;
+      char buf[BUFSIZ];
+      size_t size, ofs;
+      bool active;
+    };
+  struct pipe pipes[2];
+
+  /* Make PTY, stdin, and stdout non-blocking. */
+  make_nonblocking (pty, true);
+  make_nonblocking (STDIN_FILENO, true);
+  make_nonblocking (STDOUT_FILENO, true);
+
+  /* Configure noncanonical mode on PTY and stdin to avoid
+     waiting for end-of-line.  We want to minimize context
+     switching on PTY (for efficiency) and minimize latency on
+     stdin to avoid a laggy user experience. */
+  make_noncanon (pty, 16, 1);
+  make_noncanon (STDIN_FILENO, 1, 0);
+
+  memset (pipes, 0, sizeof pipes);
+  pipes[0].in = STDIN_FILENO;
+  pipes[0].out = pty;
+  pipes[1].in = pty;
+  pipes[1].out = STDOUT_FILENO;
+  
+  while (pipes[0].in != -1 || pipes[1].in != -1)
+    {
+      fd_set read_fds, write_fds;
+      int retval;
+      int i;
+
+      FD_ZERO (&read_fds);
+      FD_ZERO (&write_fds);
+      for (i = 0; i < 2; i++)
+        {
+          struct pipe *p = &pipes[i];
+
+          /* Don't do anything with the stdin->pty pipe until we
+             have some data for the pty->stdout pipe.  If we get
+             too eager, Bochs will throw away our input. */
+          if (i == 0 && !pipes[1].active)
+            continue;
+          
+          if (p->in != -1 && p->size + p->ofs < sizeof p->buf)
+            FD_SET (p->in, &read_fds);
+          if (p->out != -1 && p->size > 0)
+            FD_SET (p->out, &write_fds); 
+        }
+      FD_SET (dead_child_fd, &read_fds);
+
+      do 
+        {
+          retval = select (FD_SETSIZE, &read_fds, &write_fds, NULL, NULL); 
+        }
+      while (retval < 0 && errno == EINTR);
+      if (retval < 0) 
+        fail_io ("select");
+
+      if (FD_ISSET (dead_child_fd, &read_fds))
+        {
+          /* Child died.  Do final relaying. */
+          struct pipe *p = &pipes[1];
+          if (p->out == -1)
+            return;
+          make_nonblocking (STDOUT_FILENO, false);
+          for (;;) 
+            {
+              ssize_t n;
+                  
+              /* Write buffer. */
+              while (p->size > 0) 
+                {
+                  n = write (p->out, p->buf + p->ofs, p->size);
+                  if (n < 0)
+                    fail_io ("write");
+                  else if (n == 0)
+                    fail_io ("zero-length write");
+                  p->ofs += n;
+                  p->size -= n;
+                }
+              p->ofs = 0;
+
+              p->size = n = read (p->in, p->buf, sizeof p->buf);
+              if (n <= 0)
+                return;
+            }
+        }
+
+      for (i = 0; i < 2; i++) 
+        {
+          struct pipe *p = &pipes[i];
+          if (p->in != -1 && FD_ISSET (p->in, &read_fds))
+            {
+              ssize_t n = read (p->in, p->buf + p->ofs + p->size,
+                                sizeof p->buf - p->ofs - p->size);
+              if (n > 0) 
+                {
+                  p->active = true;
+                  p->size += n;
+                  if (p->size == BUFSIZ && p->ofs != 0)
+                    {
+                      memmove (p->buf, p->buf + p->ofs, p->size);
+                      p->ofs = 0;
+                    }
+                }
+              else if (!handle_error (n, &p->in, p->in == pty, "read"))
+                return;
+            }
+          if (p->out != -1 && FD_ISSET (p->out, &write_fds)) 
+            {
+              ssize_t n = write (p->out, p->buf + p->ofs, p->size);
+              if (n > 0) 
+                {
+                  p->ofs += n;
+                  p->size -= n;
+                  if (p->size == 0)
+                    p->ofs = 0;
+                }
+              else if (!handle_error (n, &p->out, p->out == pty, "write"))
+                return;
+            }
+        }
+    }
+}
+
+static int dead_child_fd;
+
+static void
+sigchld_handler (int signo __attribute__ ((unused))) 
+{
+  if (write (dead_child_fd, "", 1) < 0)
+    _exit (1);
+}
+
+int
+main (int argc __attribute__ ((unused)), char *argv[])
+{
+  int master, slave;
+  char *name;
+  pid_t pid;
+  struct sigaction sa;
+  int pipe_fds[2];
+  struct itimerval zero_itimerval, old_itimerval;
+
+  if (argc < 2) 
+    {
+      fprintf (stderr,
+               "usage: squish-pty COMMAND [ARG]...\n"
+               "Squishes both stdin and stdout into a single pseudoterminal,\n"
+               "which is passed as stdout to run the specified COMMAND.\n");
+      return EXIT_FAILURE;
+    }
+
+  /* Open master side of pty and get ready to open slave. */
+  master = open ("/dev/ptmx", O_RDWR | O_NOCTTY);
+  if (master < 0)
+    fail_io ("open \"/dev/ptmx\"");
+  if (grantpt (master) < 0)
+    fail_io ("grantpt");
+  if (unlockpt (master) < 0)
+    fail_io ("unlockpt");
+
+  /* Open slave side of pty. */
+  name = ptsname (master);
+  if (name == NULL)
+    fail_io ("ptsname");
+  slave = open (name, O_RDWR);
+  if (slave < 0)
+    fail_io ("open \"%s\"", name);
+
+  /* System V implementations need STREAMS configuration for the
+     slave. */
+  if (isastream (slave))
+    {
+      if (ioctl (slave, I_PUSH, "ptem") < 0
+          || ioctl (slave, I_PUSH, "ldterm") < 0)
+        fail_io ("ioctl");
+    }
+
+  /* Arrange to get notified when a child dies, by writing a byte
+     to a pipe fd.  We really want to use pselect() and
+     sigprocmask(), but Solaris 2.7 doesn't have it. */
+  if (pipe (pipe_fds) < 0)
+    fail_io ("pipe");
+  dead_child_fd = pipe_fds[1];
+
+  memset (&sa, 0, sizeof sa);
+  sa.sa_handler = sigchld_handler;
+  sigemptyset (&sa.sa_mask);
+  sa.sa_flags = SA_RESTART;
+  if (sigaction (SIGCHLD, &sa, NULL) < 0)
+    fail_io ("sigaction");
+
+  /* Save the virtual interval timer, which might have been set
+     by the process that ran us.  It really should be applied to
+     our child process. */
+  memset (&zero_itimerval, 0, sizeof zero_itimerval);
+  if (setitimer (ITIMER_VIRTUAL, &zero_itimerval, &old_itimerval) < 0)
+    fail_io ("setitimer");
+  
+  pid = fork ();
+  if (pid < 0)
+    fail_io ("fork");
+  else if (pid != 0) 
+    {
+      /* Running in parent process. */
+      int status;
+      close (slave);
+      relay (master, pipe_fds[0]);
+
+      /* If the subprocess has died, die in the same fashion.
+         In particular, dying from SIGVTALRM tells the pintos
+         script that we ran out of CPU time. */
+      if (waitpid (pid, &status, WNOHANG) > 0)
+        {
+          if (WIFEXITED (status))
+            return WEXITSTATUS (status);
+          else if (WIFSIGNALED (status))
+            raise (WTERMSIG (status));
+        }
+      return 0; 
+    }
+  else 
+    {
+      /* Running in child process. */
+      if (setitimer (ITIMER_VIRTUAL, &old_itimerval, NULL) < 0)
+        fail_io ("setitimer");
+      if (dup2 (slave, STDOUT_FILENO) < 0)
+        fail_io ("dup2");
+      if (close (pipe_fds[0]) < 0 || close (pipe_fds[1]) < 0
+          || close (slave) < 0 || close (master) < 0)
+        fail_io ("close");
+      execvp (argv[1], argv + 1);
+      fail_io ("exec");
+    }
+}