old-cross-binutils/gdb/serial.c
Pedro Alves 00340e1b91 Introduce a serial interface for select'able events
This patch adds a new "event" struct serial type, that is an
abstraction specifically for waking up blocking waits/selects,
implemented on top of a pipe on POSIX, and on top of a native Windows
event (CreateEvent, etc.) on Windows.

This will be used to plug signal handler / mainline code races.

For example, GDB can indefinitely delay handling a quit request if the
user presses Ctrl-C between the last QUIT call and the next (blocking)
gdb_select call in the event loop:

      QUIT;
                  <<< press ctrl-c here and end up blocked in gdb_select
		      indefinitely.

      gdb_select (...); // whoops, SIGINT was already handled, no EINTR.

A global alone (either the quit flag, or the "ready" flag of the async
signal handlers in the event loop) is not sufficient.

To plug races such as these on POSIX systems, we have to register some
waitable file descriptor in the set of files gdb_select waits on, and
write to it from the signal handler.  This is classically a pipe, and
the pattern called the self-pipe trick.  On Linux, it could be a more
efficient eventfd instead, but I'm sticking with a pipe for
simplifity, as we need it for portability anyway.

(Alternatively, we could use pselect/ppoll, and block signals until
the pselect.  The latter is not a design I think GDB could use,
because we want the QUIT macro to be super cheap, as it is used in
loops.  Plus, Windows.)

This is a "struct serial" because Windows's gdb_select relies on that.
Windows's gdb_select, our "select" replacement, knows how to wait on
all kinds of handles (regular files, pipes, sockets, console, etc.)
unlike the native Windows "select" function, which can only wait on
sockets.  Each file descriptor for a "serial" type that is not
normally waitable with WaitForMultipleObjects must have a
corresponding struct serial instance.  gdb_select then internally
looks up the struct serial instance that wraps each file descriptor,
and asks it for the corresponding Windows waitable handle.

We could use serial_pipe() to create a "struct serial"-wrapped pipe
that is usable everywhere, including Windows.  That's what currently
python/python.c uses for cross-thread posting of events.

However, serial_write and serial_readchar are not designed to be
async-signal-safe on POSIX hosts.  It's easier to bypass those when
setting/clearing the event source.

And writing and a serial pipe is a bit heavy weight on Windows.
gdb_select requires an extra thread to wait on the pipe and several
Windows events, when a single manual-reset Windows event, with no
extra thread is sufficient.

The intended usage is simply:

- Call make_serial_event to create a serial event object.

- From the signal handler call serial_event_set to set the event.

- From mainline code, have select/poll wait for serial_event_fd(), in
  addition to whatever other files you're about to wait for.

gdb/ChangeLog:
2016-04-12  Pedro Alves  <palves@redhat.com>

	* Makefile.in (SFILES): Add ser-event.c.
	(HFILES_NO_SRCDIR): Add ser-event.h.
	(COMMON_OBS): Add ser-event.o.
	* ser-event.c, ser-event.h: New files.
	* serial.c (new_serial): New function, factored out from
	(serial_fdopen_ops): ... this.
	(serial_open_ops_1): New function, factored out from
	(serial_open): ... this.
	(serial_open_ops): New function.
	* serial.h (struct serial): Forware declare.
	(serial_open_ops): New declaration.
2016-04-12 16:53:21 +01:00

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/* Generic serial interface routines
Copyright (C) 1992-2016 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 <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include <ctype.h>
#include "serial.h"
#include "gdbcmd.h"
#include "cli/cli-utils.h"
extern void _initialize_serial (void);
/* Is serial being debugged? */
static unsigned int global_serial_debug_p;
typedef const struct serial_ops *serial_ops_p;
DEF_VEC_P (serial_ops_p);
/* Serial I/O handlers. */
VEC (serial_ops_p) *serial_ops_list = NULL;
/* Pointer to list of scb's. */
static struct serial *scb_base;
/* Non-NULL gives filename which contains a recording of the remote session,
suitable for playback by gdbserver. */
static char *serial_logfile = NULL;
static struct ui_file *serial_logfp = NULL;
static const struct serial_ops *serial_interface_lookup (const char *);
static void serial_logchar (struct ui_file *stream,
int ch_type, int ch, int timeout);
static const char logbase_hex[] = "hex";
static const char logbase_octal[] = "octal";
static const char logbase_ascii[] = "ascii";
static const char *const logbase_enums[] =
{logbase_hex, logbase_octal, logbase_ascii, NULL};
static const char *serial_logbase = logbase_ascii;
static int serial_current_type = 0;
/* Log char CH of type CHTYPE, with TIMEOUT. */
/* Define bogus char to represent a BREAK. Should be careful to choose a value
that can't be confused with a normal char, or an error code. */
#define SERIAL_BREAK 1235
static void
serial_logchar (struct ui_file *stream, int ch_type, int ch, int timeout)
{
if (ch_type != serial_current_type)
{
fprintf_unfiltered (stream, "\n%c ", ch_type);
serial_current_type = ch_type;
}
if (serial_logbase != logbase_ascii)
fputc_unfiltered (' ', stream);
switch (ch)
{
case SERIAL_TIMEOUT:
fprintf_unfiltered (stream, "<Timeout: %d seconds>", timeout);
return;
case SERIAL_ERROR:
fprintf_unfiltered (stream, "<Error: %s>", safe_strerror (errno));
return;
case SERIAL_EOF:
fputs_unfiltered ("<Eof>", stream);
return;
case SERIAL_BREAK:
fputs_unfiltered ("<Break>", stream);
return;
default:
if (serial_logbase == logbase_hex)
fprintf_unfiltered (stream, "%02x", ch & 0xff);
else if (serial_logbase == logbase_octal)
fprintf_unfiltered (stream, "%03o", ch & 0xff);
else
switch (ch)
{
case '\\':
fputs_unfiltered ("\\\\", stream);
break;
case '\b':
fputs_unfiltered ("\\b", stream);
break;
case '\f':
fputs_unfiltered ("\\f", stream);
break;
case '\n':
fputs_unfiltered ("\\n", stream);
break;
case '\r':
fputs_unfiltered ("\\r", stream);
break;
case '\t':
fputs_unfiltered ("\\t", stream);
break;
case '\v':
fputs_unfiltered ("\\v", stream);
break;
default:
fprintf_unfiltered (stream,
isprint (ch) ? "%c" : "\\x%02x", ch & 0xFF);
break;
}
}
}
void
serial_log_command (struct target_ops *self, const char *cmd)
{
if (!serial_logfp)
return;
serial_current_type = 'c';
fputs_unfiltered ("\nc ", serial_logfp);
fputs_unfiltered (cmd, serial_logfp);
/* Make sure that the log file is as up-to-date as possible,
in case we are getting ready to dump core or something. */
gdb_flush (serial_logfp);
}
static const struct serial_ops *
serial_interface_lookup (const char *name)
{
const struct serial_ops *ops;
int i;
for (i = 0; VEC_iterate (serial_ops_p, serial_ops_list, i, ops); ++i)
if (strcmp (name, ops->name) == 0)
return ops;
return NULL;
}
void
serial_add_interface (const struct serial_ops *optable)
{
VEC_safe_push (serial_ops_p, serial_ops_list, optable);
}
/* Return the open serial device for FD, if found, or NULL if FD is
not already opened. */
struct serial *
serial_for_fd (int fd)
{
struct serial *scb;
for (scb = scb_base; scb; scb = scb->next)
if (scb->fd == fd)
return scb;
return NULL;
}
/* Create a new serial for OPS. */
static struct serial *
new_serial (const struct serial_ops *ops)
{
struct serial *scb;
scb = XCNEW (struct serial);
scb->ops = ops;
scb->bufp = scb->buf;
scb->error_fd = -1;
scb->refcnt = 1;
return scb;
}
static struct serial *serial_open_ops_1 (const struct serial_ops *ops,
const char *open_name);
/* Open up a device or a network socket, depending upon the syntax of NAME. */
struct serial *
serial_open (const char *name)
{
struct serial *scb;
const struct serial_ops *ops;
const char *open_name = name;
if (strcmp (name, "pc") == 0)
ops = serial_interface_lookup ("pc");
else if (startswith (name, "lpt"))
ops = serial_interface_lookup ("parallel");
else if (startswith (name, "|"))
{
ops = serial_interface_lookup ("pipe");
/* Discard ``|'' and any space before the command itself. */
++open_name;
open_name = skip_spaces_const (open_name);
}
/* Check for a colon, suggesting an IP address/port pair.
Do this *after* checking for all the interesting prefixes. We
don't want to constrain the syntax of what can follow them. */
else if (strchr (name, ':'))
ops = serial_interface_lookup ("tcp");
else
ops = serial_interface_lookup ("hardwire");
if (!ops)
return NULL;
return serial_open_ops_1 (ops, open_name);
}
/* Open up a serial for OPS, passing OPEN_NAME to the open method. */
static struct serial *
serial_open_ops_1 (const struct serial_ops *ops, const char *open_name)
{
struct serial *scb;
scb = new_serial (ops);
/* `...->open (...)' would get expanded by the open(2) syscall macro. */
if ((*scb->ops->open) (scb, open_name))
{
xfree (scb);
return NULL;
}
scb->next = scb_base;
scb_base = scb;
if (serial_logfile != NULL)
{
serial_logfp = gdb_fopen (serial_logfile, "w");
if (serial_logfp == NULL)
perror_with_name (serial_logfile);
}
return scb;
}
/* See serial.h. */
struct serial *
serial_open_ops (const struct serial_ops *ops)
{
return serial_open_ops_1 (ops, NULL);
}
/* Open a new serial stream using a file handle, using serial
interface ops OPS. */
static struct serial *
serial_fdopen_ops (const int fd, const struct serial_ops *ops)
{
struct serial *scb;
if (!ops)
{
ops = serial_interface_lookup ("terminal");
if (!ops)
ops = serial_interface_lookup ("hardwire");
}
if (!ops)
return NULL;
scb = new_serial (ops);
scb->next = scb_base;
scb_base = scb;
if ((ops->fdopen) != NULL)
(*ops->fdopen) (scb, fd);
else
scb->fd = fd;
return scb;
}
struct serial *
serial_fdopen (const int fd)
{
return serial_fdopen_ops (fd, NULL);
}
static void
do_serial_close (struct serial *scb, int really_close)
{
struct serial *tmp_scb;
if (serial_logfp)
{
fputs_unfiltered ("\nEnd of log\n", serial_logfp);
serial_current_type = 0;
/* XXX - What if serial_logfp == gdb_stdout or gdb_stderr? */
ui_file_delete (serial_logfp);
serial_logfp = NULL;
}
/* ensure that the FD has been taken out of async mode. */
if (scb->async_handler != NULL)
serial_async (scb, NULL, NULL);
if (really_close)
scb->ops->close (scb);
/* For serial_is_open. */
scb->bufp = NULL;
if (scb_base == scb)
scb_base = scb_base->next;
else
for (tmp_scb = scb_base; tmp_scb; tmp_scb = tmp_scb->next)
{
if (tmp_scb->next != scb)
continue;
tmp_scb->next = tmp_scb->next->next;
break;
}
serial_unref (scb);
}
void
serial_close (struct serial *scb)
{
do_serial_close (scb, 1);
}
void
serial_un_fdopen (struct serial *scb)
{
do_serial_close (scb, 0);
}
int
serial_is_open (struct serial *scb)
{
return scb->bufp != NULL;
}
void
serial_ref (struct serial *scb)
{
scb->refcnt++;
}
void
serial_unref (struct serial *scb)
{
--scb->refcnt;
if (scb->refcnt == 0)
xfree (scb);
}
int
serial_readchar (struct serial *scb, int timeout)
{
int ch;
/* FIXME: cagney/1999-10-11: Don't enable this check until the ASYNC
code is finished. */
if (0 && serial_is_async_p (scb) && timeout < 0)
internal_error (__FILE__, __LINE__,
_("serial_readchar: blocking read in async mode"));
ch = scb->ops->readchar (scb, timeout);
if (serial_logfp != NULL)
{
serial_logchar (serial_logfp, 'r', ch, timeout);
/* Make sure that the log file is as up-to-date as possible,
in case we are getting ready to dump core or something. */
gdb_flush (serial_logfp);
}
if (serial_debug_p (scb))
{
fprintf_unfiltered (gdb_stdlog, "[");
serial_logchar (gdb_stdlog, 'r', ch, timeout);
fprintf_unfiltered (gdb_stdlog, "]");
gdb_flush (gdb_stdlog);
}
return (ch);
}
int
serial_write (struct serial *scb, const void *buf, size_t count)
{
if (serial_logfp != NULL)
{
const char *str = (const char *) buf;
size_t c;
for (c = 0; c < count; c++)
serial_logchar (serial_logfp, 'w', str[c] & 0xff, 0);
/* Make sure that the log file is as up-to-date as possible,
in case we are getting ready to dump core or something. */
gdb_flush (serial_logfp);
}
if (serial_debug_p (scb))
{
const char *str = (const char *) buf;
size_t c;
for (c = 0; c < count; c++)
{
fprintf_unfiltered (gdb_stdlog, "[");
serial_logchar (gdb_stdlog, 'w', str[c] & 0xff, 0);
fprintf_unfiltered (gdb_stdlog, "]");
}
gdb_flush (gdb_stdlog);
}
return (scb->ops->write (scb, buf, count));
}
void
serial_printf (struct serial *desc, const char *format,...)
{
va_list args;
char *buf;
va_start (args, format);
buf = xstrvprintf (format, args);
serial_write (desc, buf, strlen (buf));
xfree (buf);
va_end (args);
}
int
serial_drain_output (struct serial *scb)
{
return scb->ops->drain_output (scb);
}
int
serial_flush_output (struct serial *scb)
{
return scb->ops->flush_output (scb);
}
int
serial_flush_input (struct serial *scb)
{
return scb->ops->flush_input (scb);
}
int
serial_send_break (struct serial *scb)
{
if (serial_logfp != NULL)
serial_logchar (serial_logfp, 'w', SERIAL_BREAK, 0);
return (scb->ops->send_break (scb));
}
void
serial_raw (struct serial *scb)
{
scb->ops->go_raw (scb);
}
serial_ttystate
serial_get_tty_state (struct serial *scb)
{
return scb->ops->get_tty_state (scb);
}
serial_ttystate
serial_copy_tty_state (struct serial *scb, serial_ttystate ttystate)
{
return scb->ops->copy_tty_state (scb, ttystate);
}
int
serial_set_tty_state (struct serial *scb, serial_ttystate ttystate)
{
return scb->ops->set_tty_state (scb, ttystate);
}
void
serial_print_tty_state (struct serial *scb,
serial_ttystate ttystate,
struct ui_file *stream)
{
scb->ops->print_tty_state (scb, ttystate, stream);
}
int
serial_noflush_set_tty_state (struct serial *scb,
serial_ttystate new_ttystate,
serial_ttystate old_ttystate)
{
return scb->ops->noflush_set_tty_state (scb, new_ttystate, old_ttystate);
}
int
serial_setbaudrate (struct serial *scb, int rate)
{
return scb->ops->setbaudrate (scb, rate);
}
int
serial_setstopbits (struct serial *scb, int num)
{
return scb->ops->setstopbits (scb, num);
}
/* See serial.h. */
int
serial_setparity (struct serial *scb, int parity)
{
return scb->ops->setparity (scb, parity);
}
int
serial_can_async_p (struct serial *scb)
{
return (scb->ops->async != NULL);
}
int
serial_is_async_p (struct serial *scb)
{
return (scb->ops->async != NULL) && (scb->async_handler != NULL);
}
void
serial_async (struct serial *scb,
serial_event_ftype *handler,
void *context)
{
int changed = ((scb->async_handler == NULL) != (handler == NULL));
scb->async_handler = handler;
scb->async_context = context;
/* Only change mode if there is a need. */
if (changed)
scb->ops->async (scb, handler != NULL);
}
void
serial_debug (struct serial *scb, int debug_p)
{
scb->debug_p = debug_p;
}
int
serial_debug_p (struct serial *scb)
{
return scb->debug_p || global_serial_debug_p;
}
#ifdef USE_WIN32API
void
serial_wait_handle (struct serial *scb, HANDLE *read, HANDLE *except)
{
if (scb->ops->wait_handle)
scb->ops->wait_handle (scb, read, except);
else
{
*read = (HANDLE) _get_osfhandle (scb->fd);
*except = NULL;
}
}
void
serial_done_wait_handle (struct serial *scb)
{
if (scb->ops->done_wait_handle)
scb->ops->done_wait_handle (scb);
}
#endif
int
serial_pipe (struct serial *scbs[2])
{
const struct serial_ops *ops;
int fildes[2];
ops = serial_interface_lookup ("pipe");
if (!ops)
{
errno = ENOSYS;
return -1;
}
if (gdb_pipe (fildes) == -1)
return -1;
scbs[0] = serial_fdopen_ops (fildes[0], ops);
scbs[1] = serial_fdopen_ops (fildes[1], ops);
return 0;
}
/* Serial set/show framework. */
static struct cmd_list_element *serial_set_cmdlist;
static struct cmd_list_element *serial_show_cmdlist;
static void
serial_set_cmd (char *args, int from_tty)
{
printf_unfiltered ("\"set serial\" must be followed "
"by the name of a command.\n");
help_list (serial_set_cmdlist, "set serial ", all_commands, gdb_stdout);
}
static void
serial_show_cmd (char *args, int from_tty)
{
cmd_show_list (serial_show_cmdlist, from_tty, "");
}
/* Baud rate specified for talking to serial target systems. Default
is left as -1, so targets can choose their own defaults. */
/* FIXME: This means that "show serial baud" and gr_files_info can
print -1 or (unsigned int)-1. This is a Bad User Interface. */
int baud_rate = -1;
static void
serial_baud_show_cmd (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
fprintf_filtered (file, _("Baud rate for remote serial I/O is %s.\n"),
value);
}
/* Parity for serial port. */
int serial_parity = GDBPARITY_NONE;
static const char parity_none[] = "none";
static const char parity_odd[] = "odd";
static const char parity_even[] = "even";
static const char *const parity_enums[] =
{parity_none, parity_odd, parity_even, NULL};
static const char *parity = parity_none;
/* Set serial_parity value. */
static void
set_parity (char *ignore_args, int from_tty, struct cmd_list_element *c)
{
if (parity == parity_odd)
serial_parity = GDBPARITY_ODD;
else if (parity == parity_even)
serial_parity = GDBPARITY_EVEN;
else
serial_parity = GDBPARITY_NONE;
}
void
_initialize_serial (void)
{
#if 0
add_com ("connect", class_obscure, connect_command, _("\
Connect the terminal directly up to the command monitor.\n\
Use <CR>~. or <CR>~^D to break out."));
#endif /* 0 */
add_prefix_cmd ("serial", class_maintenance, serial_set_cmd, _("\
Set default serial/parallel port configuration."),
&serial_set_cmdlist, "set serial ",
0/*allow-unknown*/,
&setlist);
add_prefix_cmd ("serial", class_maintenance, serial_show_cmd, _("\
Show default serial/parallel port configuration."),
&serial_show_cmdlist, "show serial ",
0/*allow-unknown*/,
&showlist);
/* If target is open when baud changes, it doesn't take effect until
the next open (I think, not sure). */
add_setshow_zinteger_cmd ("baud", no_class, &baud_rate, _("\
Set baud rate for remote serial I/O."), _("\
Show baud rate for remote serial I/O."), _("\
This value is used to set the speed of the serial port when debugging\n\
using remote targets."),
NULL,
serial_baud_show_cmd,
&serial_set_cmdlist, &serial_show_cmdlist);
add_setshow_enum_cmd ("parity", no_class, parity_enums,
&parity, _("\
Set parity for remote serial I/O"), _("\
Show parity for remote serial I/O"), NULL,
set_parity,
NULL, /* FIXME: i18n: */
&serial_set_cmdlist, &serial_show_cmdlist);
add_setshow_filename_cmd ("remotelogfile", no_class, &serial_logfile, _("\
Set filename for remote session recording."), _("\
Show filename for remote session recording."), _("\
This file is used to record the remote session for future playback\n\
by gdbserver."),
NULL,
NULL, /* FIXME: i18n: */
&setlist, &showlist);
add_setshow_enum_cmd ("remotelogbase", no_class, logbase_enums,
&serial_logbase, _("\
Set numerical base for remote session logging"), _("\
Show numerical base for remote session logging"), NULL,
NULL,
NULL, /* FIXME: i18n: */
&setlist, &showlist);
add_setshow_zuinteger_cmd ("serial", class_maintenance,
&global_serial_debug_p, _("\
Set serial debugging."), _("\
Show serial debugging."), _("\
When non-zero, serial port debugging is enabled."),
NULL,
NULL, /* FIXME: i18n: */
&setdebuglist, &showdebuglist);
}