/* Serial interface for local (hardwired) serial ports on Un*x like systems
Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001, 2003,
2004, 2005, 2007 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see . */
#include "defs.h"
#include "serial.h"
#include "ser-base.h"
#include "ser-unix.h"
#include
#include
#include "terminal.h"
#include
#include
#include "gdb_select.h"
#include "gdb_string.h"
#include "gdbcmd.h"
#ifdef HAVE_TERMIOS
struct hardwire_ttystate
{
struct termios termios;
};
#ifdef CRTSCTS
/* Boolean to explicitly enable or disable h/w flow control. */
static int serial_hwflow;
static void
show_serial_hwflow (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
fprintf_filtered (file, _("Hardware flow control is %s.\n"), value);
}
#endif
#endif /* termios */
#ifdef HAVE_TERMIO
/* It is believed that all systems which have added job control to SVR3
(e.g. sco) have also added termios. Even if not, trying to figure out
all the variations (TIOCGPGRP vs. TCGETPGRP, etc.) would be pretty
bewildering. So we don't attempt it. */
struct hardwire_ttystate
{
struct termio termio;
};
#endif /* termio */
#ifdef HAVE_SGTTY
struct hardwire_ttystate
{
struct sgttyb sgttyb;
struct tchars tc;
struct ltchars ltc;
/* Line discipline flags. */
int lmode;
};
#endif /* sgtty */
static int hardwire_open (struct serial *scb, const char *name);
static void hardwire_raw (struct serial *scb);
static int wait_for (struct serial *scb, int timeout);
static int hardwire_readchar (struct serial *scb, int timeout);
static int do_hardwire_readchar (struct serial *scb, int timeout);
static int rate_to_code (int rate);
static int hardwire_setbaudrate (struct serial *scb, int rate);
static void hardwire_close (struct serial *scb);
static int get_tty_state (struct serial *scb,
struct hardwire_ttystate * state);
static int set_tty_state (struct serial *scb,
struct hardwire_ttystate * state);
static serial_ttystate hardwire_get_tty_state (struct serial *scb);
static int hardwire_set_tty_state (struct serial *scb, serial_ttystate state);
static int hardwire_noflush_set_tty_state (struct serial *, serial_ttystate,
serial_ttystate);
static void hardwire_print_tty_state (struct serial *, serial_ttystate,
struct ui_file *);
static int hardwire_drain_output (struct serial *);
static int hardwire_flush_output (struct serial *);
static int hardwire_flush_input (struct serial *);
static int hardwire_send_break (struct serial *);
static int hardwire_setstopbits (struct serial *, int);
void _initialize_ser_hardwire (void);
/* Open up a real live device for serial I/O */
static int
hardwire_open (struct serial *scb, const char *name)
{
scb->fd = open (name, O_RDWR);
if (scb->fd < 0)
return -1;
return 0;
}
static int
get_tty_state (struct serial *scb, struct hardwire_ttystate *state)
{
#ifdef HAVE_TERMIOS
if (tcgetattr (scb->fd, &state->termios) < 0)
return -1;
return 0;
#endif
#ifdef HAVE_TERMIO
if (ioctl (scb->fd, TCGETA, &state->termio) < 0)
return -1;
return 0;
#endif
#ifdef HAVE_SGTTY
if (ioctl (scb->fd, TIOCGETP, &state->sgttyb) < 0)
return -1;
if (ioctl (scb->fd, TIOCGETC, &state->tc) < 0)
return -1;
if (ioctl (scb->fd, TIOCGLTC, &state->ltc) < 0)
return -1;
if (ioctl (scb->fd, TIOCLGET, &state->lmode) < 0)
return -1;
return 0;
#endif
}
static int
set_tty_state (struct serial *scb, struct hardwire_ttystate *state)
{
#ifdef HAVE_TERMIOS
if (tcsetattr (scb->fd, TCSANOW, &state->termios) < 0)
return -1;
return 0;
#endif
#ifdef HAVE_TERMIO
if (ioctl (scb->fd, TCSETA, &state->termio) < 0)
return -1;
return 0;
#endif
#ifdef HAVE_SGTTY
if (ioctl (scb->fd, TIOCSETN, &state->sgttyb) < 0)
return -1;
if (ioctl (scb->fd, TIOCSETC, &state->tc) < 0)
return -1;
if (ioctl (scb->fd, TIOCSLTC, &state->ltc) < 0)
return -1;
if (ioctl (scb->fd, TIOCLSET, &state->lmode) < 0)
return -1;
return 0;
#endif
}
static serial_ttystate
hardwire_get_tty_state (struct serial *scb)
{
struct hardwire_ttystate *state;
state = (struct hardwire_ttystate *) xmalloc (sizeof *state);
if (get_tty_state (scb, state))
return NULL;
return (serial_ttystate) state;
}
static int
hardwire_set_tty_state (struct serial *scb, serial_ttystate ttystate)
{
struct hardwire_ttystate *state;
state = (struct hardwire_ttystate *) ttystate;
return set_tty_state (scb, state);
}
static int
hardwire_noflush_set_tty_state (struct serial *scb,
serial_ttystate new_ttystate,
serial_ttystate old_ttystate)
{
struct hardwire_ttystate new_state;
#ifdef HAVE_SGTTY
struct hardwire_ttystate *state = (struct hardwire_ttystate *) old_ttystate;
#endif
new_state = *(struct hardwire_ttystate *) new_ttystate;
/* Don't change in or out of raw mode; we don't want to flush input.
termio and termios have no such restriction; for them flushing input
is separate from setting the attributes. */
#ifdef HAVE_SGTTY
if (state->sgttyb.sg_flags & RAW)
new_state.sgttyb.sg_flags |= RAW;
else
new_state.sgttyb.sg_flags &= ~RAW;
/* I'm not sure whether this is necessary; the manpage just mentions
RAW not CBREAK. */
if (state->sgttyb.sg_flags & CBREAK)
new_state.sgttyb.sg_flags |= CBREAK;
else
new_state.sgttyb.sg_flags &= ~CBREAK;
#endif
return set_tty_state (scb, &new_state);
}
static void
hardwire_print_tty_state (struct serial *scb,
serial_ttystate ttystate,
struct ui_file *stream)
{
struct hardwire_ttystate *state = (struct hardwire_ttystate *) ttystate;
int i;
#ifdef HAVE_TERMIOS
fprintf_filtered (stream, "c_iflag = 0x%x, c_oflag = 0x%x,\n",
(int) state->termios.c_iflag,
(int) state->termios.c_oflag);
fprintf_filtered (stream, "c_cflag = 0x%x, c_lflag = 0x%x\n",
(int) state->termios.c_cflag,
(int) state->termios.c_lflag);
#if 0
/* This not in POSIX, and is not really documented by those systems
which have it (at least not Sun). */
fprintf_filtered (stream, "c_line = 0x%x.\n", state->termios.c_line);
#endif
fprintf_filtered (stream, "c_cc: ");
for (i = 0; i < NCCS; i += 1)
fprintf_filtered (stream, "0x%x ", state->termios.c_cc[i]);
fprintf_filtered (stream, "\n");
#endif
#ifdef HAVE_TERMIO
fprintf_filtered (stream, "c_iflag = 0x%x, c_oflag = 0x%x,\n",
state->termio.c_iflag, state->termio.c_oflag);
fprintf_filtered (stream, "c_cflag = 0x%x, c_lflag = 0x%x, c_line = 0x%x.\n",
state->termio.c_cflag, state->termio.c_lflag,
state->termio.c_line);
fprintf_filtered (stream, "c_cc: ");
for (i = 0; i < NCC; i += 1)
fprintf_filtered (stream, "0x%x ", state->termio.c_cc[i]);
fprintf_filtered (stream, "\n");
#endif
#ifdef HAVE_SGTTY
fprintf_filtered (stream, "sgttyb.sg_flags = 0x%x.\n",
state->sgttyb.sg_flags);
fprintf_filtered (stream, "tchars: ");
for (i = 0; i < (int) sizeof (struct tchars); i++)
fprintf_filtered (stream, "0x%x ", ((unsigned char *) &state->tc)[i]);
fprintf_filtered (stream, "\n");
fprintf_filtered (stream, "ltchars: ");
for (i = 0; i < (int) sizeof (struct ltchars); i++)
fprintf_filtered (stream, "0x%x ", ((unsigned char *) &state->ltc)[i]);
fprintf_filtered (stream, "\n");
fprintf_filtered (stream, "lmode: 0x%x\n", state->lmode);
#endif
}
/* Wait for the output to drain away, as opposed to flushing (discarding) it */
static int
hardwire_drain_output (struct serial *scb)
{
#ifdef HAVE_TERMIOS
return tcdrain (scb->fd);
#endif
#ifdef HAVE_TERMIO
return ioctl (scb->fd, TCSBRK, 1);
#endif
#ifdef HAVE_SGTTY
/* Get the current state and then restore it using TIOCSETP,
which should cause the output to drain and pending input
to be discarded. */
{
struct hardwire_ttystate state;
if (get_tty_state (scb, &state))
{
return (-1);
}
else
{
return (ioctl (scb->fd, TIOCSETP, &state.sgttyb));
}
}
#endif
}
static int
hardwire_flush_output (struct serial *scb)
{
#ifdef HAVE_TERMIOS
return tcflush (scb->fd, TCOFLUSH);
#endif
#ifdef HAVE_TERMIO
return ioctl (scb->fd, TCFLSH, 1);
#endif
#ifdef HAVE_SGTTY
/* This flushes both input and output, but we can't do better. */
return ioctl (scb->fd, TIOCFLUSH, 0);
#endif
}
static int
hardwire_flush_input (struct serial *scb)
{
ser_base_flush_input (scb);
#ifdef HAVE_TERMIOS
return tcflush (scb->fd, TCIFLUSH);
#endif
#ifdef HAVE_TERMIO
return ioctl (scb->fd, TCFLSH, 0);
#endif
#ifdef HAVE_SGTTY
/* This flushes both input and output, but we can't do better. */
return ioctl (scb->fd, TIOCFLUSH, 0);
#endif
}
static int
hardwire_send_break (struct serial *scb)
{
#ifdef HAVE_TERMIOS
return tcsendbreak (scb->fd, 0);
#endif
#ifdef HAVE_TERMIO
return ioctl (scb->fd, TCSBRK, 0);
#endif
#ifdef HAVE_SGTTY
{
int status;
struct timeval timeout;
status = ioctl (scb->fd, TIOCSBRK, 0);
/* Can't use usleep; it doesn't exist in BSD 4.2. */
/* Note that if this select() is interrupted by a signal it will not wait
the full length of time. I think that is OK. */
timeout.tv_sec = 0;
timeout.tv_usec = 250000;
gdb_select (0, 0, 0, 0, &timeout);
status = ioctl (scb->fd, TIOCCBRK, 0);
return status;
}
#endif
}
static void
hardwire_raw (struct serial *scb)
{
struct hardwire_ttystate state;
if (get_tty_state (scb, &state))
fprintf_unfiltered (gdb_stderr, "get_tty_state failed: %s\n", safe_strerror (errno));
#ifdef HAVE_TERMIOS
state.termios.c_iflag = 0;
state.termios.c_oflag = 0;
state.termios.c_lflag = 0;
state.termios.c_cflag &= ~(CSIZE | PARENB);
state.termios.c_cflag |= CLOCAL | CS8;
#ifdef CRTSCTS
/* h/w flow control. */
if (serial_hwflow)
state.termios.c_cflag |= CRTSCTS;
else
state.termios.c_cflag &= ~CRTSCTS;
#ifdef CRTS_IFLOW
if (serial_hwflow)
state.termios.c_cflag |= CRTS_IFLOW;
else
state.termios.c_cflag &= ~CRTS_IFLOW;
#endif
#endif
state.termios.c_cc[VMIN] = 0;
state.termios.c_cc[VTIME] = 0;
#endif
#ifdef HAVE_TERMIO
state.termio.c_iflag = 0;
state.termio.c_oflag = 0;
state.termio.c_lflag = 0;
state.termio.c_cflag &= ~(CSIZE | PARENB);
state.termio.c_cflag |= CLOCAL | CS8;
state.termio.c_cc[VMIN] = 0;
state.termio.c_cc[VTIME] = 0;
#endif
#ifdef HAVE_SGTTY
state.sgttyb.sg_flags |= RAW | ANYP;
state.sgttyb.sg_flags &= ~(CBREAK | ECHO);
#endif
scb->current_timeout = 0;
if (set_tty_state (scb, &state))
fprintf_unfiltered (gdb_stderr, "set_tty_state failed: %s\n", safe_strerror (errno));
}
/* Wait for input on scb, with timeout seconds. Returns 0 on success,
otherwise SERIAL_TIMEOUT or SERIAL_ERROR.
For termio{s}, we actually just setup VTIME if necessary, and let the
timeout occur in the read() in hardwire_read().
*/
/* FIXME: cagney/1999-09-16: Don't replace this with the equivalent
ser_base*() until the old TERMIOS/SGTTY/... timer code has been
flushed. . */
/* NOTE: cagney/1999-09-30: Much of the code below is dead. The only
possible values of the TIMEOUT parameter are ONE and ZERO.
Consequently all the code that tries to handle the possability of
an overflowed timer is unnecessary. */
static int
wait_for (struct serial *scb, int timeout)
{
#ifdef HAVE_SGTTY
while (1)
{
struct timeval tv;
fd_set readfds;
int numfds;
/* NOTE: Some OS's can scramble the READFDS when the select()
call fails (ex the kernel with Red Hat 5.2). Initialize all
arguments before each call. */
tv.tv_sec = timeout;
tv.tv_usec = 0;
FD_ZERO (&readfds);
FD_SET (scb->fd, &readfds);
if (timeout >= 0)
numfds = gdb_select (scb->fd + 1, &readfds, 0, 0, &tv);
else
numfds = gdb_select (scb->fd + 1, &readfds, 0, 0, 0);
if (numfds <= 0)
if (numfds == 0)
return SERIAL_TIMEOUT;
else if (errno == EINTR)
continue;
else
return SERIAL_ERROR; /* Got an error from select or poll */
return 0;
}
#endif /* HAVE_SGTTY */
#if defined HAVE_TERMIO || defined HAVE_TERMIOS
if (timeout == scb->current_timeout)
return 0;
scb->current_timeout = timeout;
{
struct hardwire_ttystate state;
if (get_tty_state (scb, &state))
fprintf_unfiltered (gdb_stderr, "get_tty_state failed: %s\n", safe_strerror (errno));
#ifdef HAVE_TERMIOS
if (timeout < 0)
{
/* No timeout. */
state.termios.c_cc[VTIME] = 0;
state.termios.c_cc[VMIN] = 1;
}
else
{
state.termios.c_cc[VMIN] = 0;
state.termios.c_cc[VTIME] = timeout * 10;
if (state.termios.c_cc[VTIME] != timeout * 10)
{
/* If c_cc is an 8-bit signed character, we can't go
bigger than this. If it is always unsigned, we could use
25. */
scb->current_timeout = 12;
state.termios.c_cc[VTIME] = scb->current_timeout * 10;
scb->timeout_remaining = timeout - scb->current_timeout;
}
}
#endif
#ifdef HAVE_TERMIO
if (timeout < 0)
{
/* No timeout. */
state.termio.c_cc[VTIME] = 0;
state.termio.c_cc[VMIN] = 1;
}
else
{
state.termio.c_cc[VMIN] = 0;
state.termio.c_cc[VTIME] = timeout * 10;
if (state.termio.c_cc[VTIME] != timeout * 10)
{
/* If c_cc is an 8-bit signed character, we can't go
bigger than this. If it is always unsigned, we could use
25. */
scb->current_timeout = 12;
state.termio.c_cc[VTIME] = scb->current_timeout * 10;
scb->timeout_remaining = timeout - scb->current_timeout;
}
}
#endif
if (set_tty_state (scb, &state))
fprintf_unfiltered (gdb_stderr, "set_tty_state failed: %s\n", safe_strerror (errno));
return 0;
}
#endif /* HAVE_TERMIO || HAVE_TERMIOS */
}
/* Read a character with user-specified timeout. TIMEOUT is number of seconds
to wait, or -1 to wait forever. Use timeout of 0 to effect a poll. Returns
char if successful. Returns SERIAL_TIMEOUT if timeout expired, EOF if line
dropped dead, or SERIAL_ERROR for any other error (see errno in that case). */
/* FIXME: cagney/1999-09-16: Don't replace this with the equivalent
ser_base*() until the old TERMIOS/SGTTY/... timer code has been
flushed. */
/* NOTE: cagney/1999-09-16: This function is not identical to
ser_base_readchar() as part of replacing it with ser_base*()
merging will be required - this code handles the case where read()
times out due to no data while ser_base_readchar() doesn't expect
that. */
static int
do_hardwire_readchar (struct serial *scb, int timeout)
{
int status, delta;
int detach = 0;
if (timeout > 0)
timeout++;
/* We have to be able to keep the GUI alive here, so we break the
original timeout into steps of 1 second, running the "keep the
GUI alive" hook each time through the loop.
Also, timeout = 0 means to poll, so we just set the delta to 0,
so we will only go through the loop once. */
delta = (timeout == 0 ? 0 : 1);
while (1)
{
/* N.B. The UI may destroy our world (for instance by calling
remote_stop,) in which case we want to get out of here as
quickly as possible. It is not safe to touch scb, since
someone else might have freed it. The
deprecated_ui_loop_hook signals that we should exit by
returning 1. */
if (deprecated_ui_loop_hook)
detach = deprecated_ui_loop_hook (0);
if (detach)
return SERIAL_TIMEOUT;
scb->timeout_remaining = (timeout < 0 ? timeout : timeout - delta);
status = wait_for (scb, delta);
if (status < 0)
return status;
status = read (scb->fd, scb->buf, BUFSIZ);
if (status <= 0)
{
if (status == 0)
{
/* Zero characters means timeout (it could also be EOF, but
we don't (yet at least) distinguish). */
if (scb->timeout_remaining > 0)
{
timeout = scb->timeout_remaining;
continue;
}
else if (scb->timeout_remaining < 0)
continue;
else
return SERIAL_TIMEOUT;
}
else if (errno == EINTR)
continue;
else
return SERIAL_ERROR; /* Got an error from read */
}
scb->bufcnt = status;
scb->bufcnt--;
scb->bufp = scb->buf;
return *scb->bufp++;
}
}
static int
hardwire_readchar (struct serial *scb, int timeout)
{
return generic_readchar (scb, timeout, do_hardwire_readchar);
}
#ifndef B19200
#define B19200 EXTA
#endif
#ifndef B38400
#define B38400 EXTB
#endif
/* Translate baud rates from integers to damn B_codes. Unix should
have outgrown this crap years ago, but even POSIX wouldn't buck it. */
static struct
{
int rate;
int code;
}
baudtab[] =
{
{
50, B50
}
,
{
75, B75
}
,
{
110, B110
}
,
{
134, B134
}
,
{
150, B150
}
,
{
200, B200
}
,
{
300, B300
}
,
{
600, B600
}
,
{
1200, B1200
}
,
{
1800, B1800
}
,
{
2400, B2400
}
,
{
4800, B4800
}
,
{
9600, B9600
}
,
{
19200, B19200
}
,
{
38400, B38400
}
,
#ifdef B57600
{
57600, B57600
}
,
#endif
#ifdef B115200
{
115200, B115200
}
,
#endif
#ifdef B230400
{
230400, B230400
}
,
#endif
#ifdef B460800
{
460800, B460800
}
,
#endif
{
-1, -1
}
,
};
static int
rate_to_code (int rate)
{
int i;
for (i = 0; baudtab[i].rate != -1; i++)
{
/* test for perfect macth. */
if (rate == baudtab[i].rate)
return baudtab[i].code;
else
{
/* check if it is in between valid values. */
if (rate < baudtab[i].rate)
{
if (i)
{
warning (_("Invalid baud rate %d. Closest values are %d and %d."),
rate, baudtab[i - 1].rate, baudtab[i].rate);
}
else
{
warning (_("Invalid baud rate %d. Minimum value is %d."),
rate, baudtab[0].rate);
}
return -1;
}
}
}
/* The requested speed was too large. */
warning (_("Invalid baud rate %d. Maximum value is %d."),
rate, baudtab[i - 1].rate);
return -1;
}
static int
hardwire_setbaudrate (struct serial *scb, int rate)
{
struct hardwire_ttystate state;
int baud_code = rate_to_code (rate);
if (baud_code < 0)
{
/* The baud rate was not valid.
A warning has already been issued. */
errno = EINVAL;
return -1;
}
if (get_tty_state (scb, &state))
return -1;
#ifdef HAVE_TERMIOS
cfsetospeed (&state.termios, baud_code);
cfsetispeed (&state.termios, baud_code);
#endif
#ifdef HAVE_TERMIO
#ifndef CIBAUD
#define CIBAUD CBAUD
#endif
state.termio.c_cflag &= ~(CBAUD | CIBAUD);
state.termio.c_cflag |= baud_code;
#endif
#ifdef HAVE_SGTTY
state.sgttyb.sg_ispeed = baud_code;
state.sgttyb.sg_ospeed = baud_code;
#endif
return set_tty_state (scb, &state);
}
static int
hardwire_setstopbits (struct serial *scb, int num)
{
struct hardwire_ttystate state;
int newbit;
if (get_tty_state (scb, &state))
return -1;
switch (num)
{
case SERIAL_1_STOPBITS:
newbit = 0;
break;
case SERIAL_1_AND_A_HALF_STOPBITS:
case SERIAL_2_STOPBITS:
newbit = 1;
break;
default:
return 1;
}
#ifdef HAVE_TERMIOS
if (!newbit)
state.termios.c_cflag &= ~CSTOPB;
else
state.termios.c_cflag |= CSTOPB; /* two bits */
#endif
#ifdef HAVE_TERMIO
if (!newbit)
state.termio.c_cflag &= ~CSTOPB;
else
state.termio.c_cflag |= CSTOPB; /* two bits */
#endif
#ifdef HAVE_SGTTY
return 0; /* sgtty doesn't support this */
#endif
return set_tty_state (scb, &state);
}
static void
hardwire_close (struct serial *scb)
{
if (scb->fd < 0)
return;
close (scb->fd);
scb->fd = -1;
}
void
_initialize_ser_hardwire (void)
{
struct serial_ops *ops = XMALLOC (struct serial_ops);
memset (ops, 0, sizeof (struct serial_ops));
ops->name = "hardwire";
ops->next = 0;
ops->open = hardwire_open;
ops->close = hardwire_close;
/* FIXME: Don't replace this with the equivalent ser_base*() until
the old TERMIOS/SGTTY/... timer code has been flushed. cagney
1999-09-16. */
ops->readchar = hardwire_readchar;
ops->write = ser_base_write;
ops->flush_output = hardwire_flush_output;
ops->flush_input = hardwire_flush_input;
ops->send_break = hardwire_send_break;
ops->go_raw = hardwire_raw;
ops->get_tty_state = hardwire_get_tty_state;
ops->set_tty_state = hardwire_set_tty_state;
ops->print_tty_state = hardwire_print_tty_state;
ops->noflush_set_tty_state = hardwire_noflush_set_tty_state;
ops->setbaudrate = hardwire_setbaudrate;
ops->setstopbits = hardwire_setstopbits;
ops->drain_output = hardwire_drain_output;
ops->async = ser_base_async;
ops->read_prim = ser_unix_read_prim;
ops->write_prim = ser_unix_write_prim;
serial_add_interface (ops);
#ifdef HAVE_TERMIOS
#ifdef CRTSCTS
add_setshow_boolean_cmd ("remoteflow", no_class,
&serial_hwflow, _("\
Set use of hardware flow control for remote serial I/O."), _("\
Show use of hardware flow control for remote serial I/O."), _("\
Enable or disable hardware flow control (RTS/CTS) on the serial port\n\
when debugging using remote targets."),
NULL,
show_serial_hwflow,
&setlist, &showlist);
#endif
#endif
}
int
ser_unix_read_prim (struct serial *scb, size_t count)
{
int status;
while (1)
{
status = read (scb->fd, scb->buf, count);
if (status != -1 || errno != EINTR)
break;
}
return status;
}
int
ser_unix_write_prim (struct serial *scb, const void *buf, size_t len)
{
/* ??? Historically, GDB has not retried calls to "write" that
result in EINTR. */
return write (scb->fd, buf, len);
}