Allow remote debugging over a Unix local domain socket.

Extend the "target remote" and "target extended-remote" commands
such that if the filename provided is a Unix local domain (AF_UNIX)
socket, then it'll be treated as such, instead of trying to open
it as if it were a character device.

gdb/ChangeLog:
	* NEWS: Mention changed commands.
	* ser-uds.c: New file.
	* configure.ac (SER_HARDWIRE): Add ser-uds.o.
	* configure: Regenerate.
	* Makefile.in: Add new file.
	* serial.c (serial_open): Check if filename is a socket
	  and lookup the appropriate interface accordingly.

gdb/doc/ChangeLog:
	* gdb.texinfo (Remote Connection Commands): Describe
	  the changes to target remote and target extended-remote
	  relating to Unix domain sockets.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2018-10-02  John Darrington <john@darrington.wattle.id.au>
+
+	* NEWS: Mention changed commands.
+	* ser-uds.c: New file.
+	* configure.ac (SER_HARDWIRE): Add ser-uds.o.
+	* configure: Regenerate.
+	* Makefile.in: Add new file.
+	* serial.c (serial_open): Check if filename is a socket
+	  and lookup the appropriate interface accordingly.
+
 2018-10-01  Alan Hayward  <alan.hayward@arm.com>
 
 	* aarch64-linux-tdep.c (AARCH64_SIGCONTEXT_RESERVED_OFFSET): Add

gdb/Makefile.in

@@ -2323,6 +2323,7 @@ ALLDEPFILES = \
 	ser-mingw.c \
 	ser-pipe.c \
 	ser-tcp.c \
+	ser-uds.c \
 	sh-nbsd-nat.c \
 	sh-nbsd-tdep.c \
 	sh-tdep.c \

gdb/NEWS

@@ -69,6 +69,11 @@ info proc files
 
 * Changed commands
 
+target remote FILENAME
+target extended-remote FILENAME
+  If FILENAME is a Unix domain socket, GDB will attempt to connect
+  to this socket instead of opening FILENAME as a character device.
+
 thread apply [all | COUNT | -COUNT] [FLAG]... COMMAND
   The 'thread apply' command accepts new FLAG arguments.
   FLAG arguments allow to control what output to produce and how to handle

gdb/configure

@@ -15592,6 +15592,7 @@ case ${host} in
   *go32* ) SER_HARDWIRE=ser-go32.o ;;
   *djgpp* ) SER_HARDWIRE=ser-go32.o ;;
   *mingw32*) SER_HARDWIRE="ser-base.o ser-tcp.o ser-mingw.o" ;;
+  *) SER_HARDWIRE="$SER_HARDWIRE ser-uds.o" ;;
 esac
 
 

gdb/configure.ac

@@ -1853,6 +1853,7 @@ case ${host} in
   *go32* ) SER_HARDWIRE=ser-go32.o ;;
   *djgpp* ) SER_HARDWIRE=ser-go32.o ;;
   *mingw32*) SER_HARDWIRE="ser-base.o ser-tcp.o ser-mingw.o" ;;
+  *) SER_HARDWIRE="$SER_HARDWIRE ser-uds.o" ;;
 esac
 AC_SUBST(SER_HARDWIRE)
 

gdb/doc/ChangeLog

@@ -1,3 +1,9 @@
+2018-10-02  John Darrington <john@darrington.wattle.id.au>
+
+        * gdb.texinfo (Remote Connection Commands): Describe
+	  the changes to target remote and target extended-remote
+	  relating to Unix domain sockets.
+
 2018-10-01  Tom Tromey  <tom@tromey.com>
 
 	* gdb.texinfo (Configure Options): Document configure options.

gdb/doc/gdb.texinfo

@@ -20782,7 +20782,8 @@ programs.
 
 @subsection Remote Connection Commands
 @cindex remote connection commands
-@value{GDBN} can communicate with the target over a serial line, or
+@value{GDBN} can communicate with the target over a serial line, a
+local Unix domain socket, or
 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}.  In
 each case, @value{GDBN} uses the same protocol for debugging your
 program; only the medium carrying the debugging packets varies.  The
@@ -20807,6 +20808,24 @@ If you're using a serial line, you may want to give @value{GDBN} the
 (@pxref{Remote Configuration, set serial baud}) before the
 @code{target} command.
 
+@item target remote @var{local-socket}
+@itemx target extended-remote @var{local-socket}
+@cindex local socket, @code{target remote}
+@cindex Unix domain socket
+Use @var{local-socket} to communicate with the target.  For example,
+to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
+
+@smallexample
+target remote /tmp/gdb-socket0
+@end smallexample
+
+Note that this command has the same form as the command to connect
+to a serial line.  @value{GDBN} will automatically determine which
+kind of file you have specified and will make the appropriate kind
+of connection.
+This feature is not available if the host system does not support
+Unix domain sockets.
+
 @item target remote @code{@var{host}:@var{port}}
 @itemx target remote @code{@var{[host]}:@var{port}}
 @itemx target remote @code{tcp:@var{host}:@var{port}}

gdb/ser-uds.c

@@ -0,0 +1,118 @@
+/* Serial interface for local domain connections on Un*x like systems.
+
+   Copyright (C) 1992-2018 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 "serial.h"
+#include "ser-base.h"
+
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#ifndef UNIX_PATH_MAX
+#define UNIX_PATH_MAX sizeof(((struct sockaddr_un *) NULL)->sun_path)
+#endif
+
+/* Open an AF_UNIX socket.  */
+
+static int
+uds_open (struct serial *scb, const char *name)
+{
+  struct sockaddr_un addr;
+
+  if (strlen (name) > UNIX_PATH_MAX - 1)
+    {
+      warning
+        (_("The socket name is too long.  It may be no longer than %s bytes."),
+         pulongest (UNIX_PATH_MAX - 1L));
+      return -1;
+    }
+
+  memset (&addr, 0, sizeof addr);
+  addr.sun_family = AF_UNIX;
+  strncpy (addr.sun_path, name, UNIX_PATH_MAX - 1);
+
+  int sock = socket (AF_UNIX, SOCK_STREAM, 0);
+
+  if (connect (sock, (struct sockaddr *) &addr,
+	       sizeof (struct sockaddr_un)) < 0)
+    {
+      close (sock);
+      scb->fd = -1;
+      return -1;
+    }
+
+  scb->fd = sock;
+
+  return 0;
+}
+
+static void
+uds_close (struct serial *scb)
+{
+  if (scb->fd == -1)
+    return;
+
+  close (scb->fd);
+  scb->fd = -1;
+}
+
+static int
+uds_read_prim (struct serial *scb, size_t count)
+{
+  return recv (scb->fd, scb->buf, count, 0);
+}
+
+static int
+uds_write_prim (struct serial *scb, const void *buf, size_t count)
+{
+  return send (scb->fd, buf, count, 0);
+}
+
+/* The local socket ops.  */
+
+static const struct serial_ops uds_ops =
+{
+  "local",
+  uds_open,
+  uds_close,
+  NULL,
+  ser_base_readchar,
+  ser_base_write,
+  ser_base_flush_output,
+  ser_base_flush_input,
+  ser_base_send_break,
+  ser_base_raw,
+  ser_base_get_tty_state,
+  ser_base_copy_tty_state,
+  ser_base_set_tty_state,
+  ser_base_print_tty_state,
+  ser_base_setbaudrate,
+  ser_base_setstopbits,
+  ser_base_setparity,
+  ser_base_drain_output,
+  ser_base_async,
+  uds_read_prim,
+  uds_write_prim
+};
+
+void
+_initialize_ser_socket (void)
+{
+  serial_add_interface (&uds_ops);
+}

gdb/serial.c

@@ -213,7 +213,17 @@ serial_open (const char *name)
   else if (strchr (name, ':'))
     ops = serial_interface_lookup ("tcp");
   else
-    ops = serial_interface_lookup ("hardwire");
+    {
+#ifndef USE_WIN32API
+      /* Check to see if name is a socket.  If it is, then treat it
+         as such.  Otherwise assume that it's a character device.  */
+      struct stat sb;
+      if (stat (name, &sb) == 0 && (sb.st_mode & S_IFMT) == S_IFSOCK)
+	ops = serial_interface_lookup ("local");
+      else
+#endif
+	ops = serial_interface_lookup ("hardwire");
+    }
 
   if (!ops)
     return NULL;