Implement multiple-filesystem support for remote targets

This commit allows GDB to access executables and shared libraries
on remote targets where the remote stub does not share a common
filesystem with the inferior(s).  A new packet "vFile:setfs" is
added to the remote protocol and the three remote hostio functions
with filename arguments are modified to send "vFile:setfs" packets
as necessary.

gdb/ChangeLog:

	* remote.c (struct remote_state) <fs_pid>: New field.
	(new_remote_state): Initialize the above.
	(PACKET_vFile_setfs): New enum value.
	(remote_hostio_set_filesystem): New function.
	(remote_hostio_open): Call the above.
	(remote_hostio_unlink): Likewise.
	(remote_hostio_readlink): Likewise.
	(_initialize_remote): Register new "set/show remote
	hostio-setfs-packet" command.
	* NEWS: Announce new vFile:setfs packet.

gdb/doc/ChangeLog:

	* gdb.texinfo (Remote Configuration): Document the
	"set/show remote hostio-setfs-packet" command.
	(Host I/O Packets): Document the vFile:setfs packet.

2 files changed, 24 insertions, 0 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index a9a8137..9264cfa 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,5 +1,11 @@
 2015-06-10  Gary Benson <gbenson@redhat.com>
 
+	* gdb.texinfo (Remote Configuration): Document the
+	"set/show remote hostio-setfs-packet" command.
+	(Host I/O Packets): Document the vFile:setfs packet.
+
+2015-06-10  Gary Benson <gbenson@redhat.com>
+
 	* gdb.texinfo (Debugging Output): Document the "set/show debug
 	linux-namespaces" command.
 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 4bb092c..f502143 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -19916,6 +19916,10 @@ are:
 @tab @code{vFile:fstat}
 @tab Host I/O
 
+@item @code{hostio-setfs-packet}
+@tab @code{vFile:setfs}
+@tab Host I/O
+
 @item @code{noack-packet}
 @tab @code{QStartNoAckMode}
 @tab Packet acknowledgment
@@ -37742,6 +37746,20 @@ attachment (i.e.@: a trailing semicolon).  The return value is the
 number of target bytes read; the binary attachment may be longer if
 some characters were escaped.
 
+@item vFile:setfs: @var{pid}
+Select the filesystem on which @code{vFile} operations with
+@var{filename} arguments will operate.  This is required for
+@value{GDBN} to be able to access files on remote targets where
+the remote stub does not share a common filesystem with the
+inferior(s).
+
+If @var{pid} is nonzero, select the filesystem as seen by process
+@var{pid}.  If @var{pid} is zero, select the filesystem as seen by
+the remote stub.  Return 0 on success, or -1 if an error occurs.
+If @code{vFile:setfs:} indicates success, the selected filesystem
+remains selected until the next successful @code{vFile:setfs:}
+operation.
+
 @end table
 
 @node Interrupts