[PATCH] Allow remote debugging over a local domain socket

[John Darrington <john at darrington dot wattle dot id dot au>]

Extend the "target remote"  and "target extended-remote" commands
such that if the filename provided is a unix 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:
	* gdb/NEWS:  Mention changed commands.
	* gdb/configure.ac (SER_HARDWIRE): Add ser-socket.o
	* gdb/doc/gdb.texinfo (Remote Connection Commands):  Describe
          changed commands.
	* gdb/ser-socket.c: New file.
	* gdb/ser-socket.h: New file.
	* gdb/Makefile.in: Add new files.
	* gdb/serial.c (serial_open): Check if filename is a socket
          and lookup the appropriate interface accordingly.
---
 gdb/Makefile.in     |   2 +
 gdb/NEWS            |   5 ++
 gdb/configure.ac    |   2 +-
 gdb/doc/gdb.texinfo |  19 +++++++-
 gdb/ser-socket.c    | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/ser-socket.h    |  31 ++++++++++++
 gdb/serial.c        |  10 +++-
 7 files changed, 198 insertions(+), 3 deletions(-)
 create mode 100644 gdb/ser-socket.c
 create mode 100644 gdb/ser-socket.h

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index f448d1ee19..cb98f987da 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -1355,6 +1355,7 @@ HFILES_NO_SRCDIR = \
 	sentinel-frame.h \
 	ser-base.h \
 	ser-event.h \
+	ser-socket.h \
 	ser-tcp.h \
 	ser-unix.h \
 	serial.h \
@@ -2324,6 +2325,7 @@ ALLDEPFILES = \
 	ser-go32.c \
 	ser-mingw.c \
 	ser-pipe.c \
+	ser-socket.c \
 	ser-tcp.c \
 	sh-nbsd-nat.c \
 	sh-nbsd-tdep.c \
diff --git a/gdb/NEWS b/gdb/NEWS
index c46056525a..c7436e0ced 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -40,6 +40,11 @@ maint show dwarf unwinders
 
 * 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
diff --git a/gdb/configure.ac b/gdb/configure.ac
index 13bc5f9a8f..f6735858d7 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -1870,7 +1870,7 @@ lose
 
 
 dnl Figure out which of the many generic ser-*.c files the _host_ supports.
-SER_HARDWIRE="ser-base.o ser-unix.o ser-pipe.o ser-tcp.o"
+SER_HARDWIRE="ser-base.o ser-unix.o ser-pipe.o ser-socket.o ser-tcp.o"
 case ${host} in
   *go32* ) SER_HARDWIRE=ser-go32.o ;;
   *djgpp* ) SER_HARDWIRE=ser-go32.o ;;
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index e4ecd57a9e..5ae53e0582 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -20703,7 +20703,8 @@ 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 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
@@ -20728,6 +20729,22 @@ 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}
+Use @var{local-socket} to communicate with the target.  For example,
+to use a local 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.
+
 @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}}
diff --git a/gdb/ser-socket.c b/gdb/ser-socket.c
new file mode 100644
index 0000000000..54d14f36ad
--- /dev/null
+++ b/gdb/ser-socket.c
@@ -0,0 +1,132 @@
+/* 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 "ser-socket.h"
+
+#include <sys/socket.h>
+#include <sys/un.h>
+
+
+/* Open a AF_UNIX socket.  */
+int
+socket_open (struct serial *scb, const char *name)
+{
+  struct sockaddr_un addr;
+
+  memset (&addr, 0, sizeof addr);
+  addr.sun_family = AF_UNIX;
+#ifndef UNIX_MAX_PATH
+# define UNIX_MAX_PATH 108
+#endif
+  strncpy (addr.sun_path, name, UNIX_MAX_PATH - 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;
+}
+
+void
+socket_close (struct serial *scb)
+{
+  if (scb->fd == -1)
+    return;
+
+  close (scb->fd);
+  scb->fd = -1;
+}
+
+int
+socket_read_prim (struct serial *scb, size_t count)
+{
+  /* Need to cast to silence -Wpointer-sign on MinGW, as Winsock's
+     'recv' takes 'char *' as second argument, while 'scb->buf' is
+     'unsigned char *'.  */
+  return recv (scb->fd, (char *) scb->buf, count, 0);
+}
+
+int
+socket_write_prim (struct serial *scb, const void *buf, size_t count)
+{
+  /* On Windows, the second parameter to send is a "const char *"; on
+     UNIX systems it is generally "const void *".  The cast to "const
+     char *" is OK everywhere, since in C++ any data pointer type can
+     be implicitly converted to "const void *".  */
+  return send (scb->fd, (const char *) buf, count, 0);
+}
+
+int
+ser_socket_send_break (struct serial *scb)
+{
+  /* Send telnet IAC and BREAK characters.  */
+  return (serial_write (scb, "\377\363", 2));
+}
+
+#ifndef USE_WIN32API
+
+/* The SOCKET ops.  */
+
+static const struct serial_ops socket_ops =
+{
+  "socket",
+  socket_open,
+  socket_close,
+  NULL,
+  ser_base_readchar,
+  ser_base_write,
+  ser_base_flush_output,
+  ser_base_flush_input,
+  ser_socket_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,
+  socket_read_prim,
+  socket_write_prim
+};
+
+#endif /* USE_WIN32API */
+
+void
+_initialize_ser_socket (void)
+{
+#ifdef USE_WIN32API
+  /* Do nothing; Windoze does not have local domain sockets. */
+#else
+  serial_add_interface (&socket_ops);
+#endif /* USE_WIN32API */
+}
diff --git a/gdb/ser-socket.h b/gdb/ser-socket.h
new file mode 100644
index 0000000000..58509302d6
--- /dev/null
+++ b/gdb/ser-socket.h
@@ -0,0 +1,31 @@
+/* Serial interface for raw TCP connections on Un*x like systems.
+
+   Copyright (C) 2006-2018 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/>.  */
+
+#ifndef SER_SOCKET_H
+#define SER_SOCKET_H
+
+struct serial;
+
+extern int socket_open (struct serial *scb, const char *name);
+extern void socket_close (struct serial *scb);
+extern int socket_read_prim (struct serial *scb, size_t count);
+extern int socket_write_prim (struct serial *scb, const void *buf, size_t count);
+extern int ser_socket_send_break (struct serial *scb);
+
+#endif
diff --git a/gdb/serial.c b/gdb/serial.c
index fb2b212918..13b1af3873 100644
--- a/gdb/serial.c
+++ b/gdb/serial.c
@@ -213,7 +213,15 @@ serial_open (const char *name)
   else if (strchr (name, ':'))
     ops = serial_interface_lookup ("tcp");
   else
-    ops = serial_interface_lookup ("hardwire");
+    {
+      /* Check to see if name is a socket.  If it is, then treat is
+         as such.  Otherwise assume that it's a character device.  */
+      struct stat sb;
+      if (0 == stat (name, &sb) && ((sb.st_mode & S_IFMT) == S_IFSOCK))
+	ops = serial_interface_lookup ("socket");
+      else
+	ops = serial_interface_lookup ("hardware");
+    }
 
   if (!ops)
     return NULL;
-- 
2.11.0