[PATCH v2 5/5] Extend "set cwd" to work on gdbserver

[Sergio Durigan Junior <sergiodj at redhat dot com>]

This is the "natural" extension necessary for the "set cwd" command
(and the whole "set the inferior's cwd" logic) to work on gdbserver.

The idea here is to have a new remote packet, QSetWorkingDir (name
adopted from LLDB's extension to the RSP, as can be seen at
<https://raw.githubusercontent.com/llvm-mirror/lldb/master/docs/lldb-gdb-remote.txt>),
which sends an hex-encoded string representing the working directory
that gdbserver is supposed to cd into before executing the inferior.
The good thing is that since this feature is already implemented on
nat/fork-inferior.c, all gdbserver has to do is to basically implement
"set_inferior_cwd" and call it whenever such packet arrives.

Aside from that, the patch consists basically of updates to the
testcase (making it available on remote targets) the documentation.

No regressions found.

gdb/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* NEWS (Changes since GDB 8.0): Add entry about new
	'set-cwd-on-gdbserver' feature.
	(New remote packets): Add entry for QSetWorkingDir.
	* common/common-inferior.h (set_inferior_cwd): New prototype.
	* infcmd.c (set_inferior_cwd): Remove "static".
	* remote.c: Add PACKET_QSetWorkingDir.
	(remote_protocol_features) <QSetWorkingDir>: New entry for
	PACKET_QSetWorkingDir.
	(extended_remote_handle_inferior_cwd): New function.
	(extended_remote_create_inferior): Call
	"extended_remote_handle_inferior_cwd".
	(_initialize_remote): Call "add_packet_config_cmd" for
	QSetWorkingDir.

gdb/gdbserver/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* inferiors.c (set_inferior_cwd): New function.
	* server.c (handle_general_set): Handle QSetWorkingDir packet.
	(handle_query): Inform that QSetWorkingDir is supported.
	* win32-low.c (create_process): Pass "inferior_cwd" to
	CreateProcess.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.base/set-cwd.exp: Make it available on gdbserver.

gdb/doc/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.texinfo (Starting your Program) <The working directory.>:
	Mention remote debugging.
	(Working Directory) <Your Program's Working Directory>:
	Likewise.
	(Connecting) <Remote Packet>: Add "set-working-dir"
	and "QSetWorkingDir" to the table.
	(Remote Protocol) <QSetWorkingDir>: New item, explaining the
	packet.
---
 gdb/NEWS                           | 11 ++++++++++
 gdb/common/common-inferior.h       |  4 ++++
 gdb/doc/gdb.texinfo                | 44 ++++++++++++++++++++++++++++++++++----
 gdb/gdbserver/inferiors.c          |  9 ++++++++
 gdb/gdbserver/server.c             | 18 +++++++++++++++-
 gdb/gdbserver/win32-low.c          |  5 +++--
 gdb/infcmd.c                       |  5 ++---
 gdb/remote.c                       | 35 ++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.base/set-cwd.exp | 14 ++++++++----
 9 files changed, 131 insertions(+), 14 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 0dcfcc98af..a0f78e4c35 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -39,6 +39,14 @@
      variables that are to be set or unset from GDB.  These variables
      will affect the environment to be passed to the inferior.
 
+  ** On Unix systems, GDBserver is now able to enter a directory
+     before starting an inferior.
+
+     This is done by using the "cd" command in GDB, which instructs it
+     to tell GDBserver about this directory change the next time an
+     inferior is run.  If you want to make GDBserver enter the
+     directory your GDB is currently in, you can do a "cd ." in GDB.
+
 * New remote packets
 
 QEnvironmentHexEncoded
@@ -56,6 +64,9 @@ QEnvironmentReset
 QStartupWithShell
   Indicates whether the inferior must be started with a shell or not.
 
+QSetWorkingDir
+  Tell GDBserver to enter another directory before starting the inferior.
+
 * The "maintenance print c-tdesc" command now takes an optional
   argument which is the file name of XML target description.
 
diff --git a/gdb/common/common-inferior.h b/gdb/common/common-inferior.h
index 515a8c0f4e..65c23a936b 100644
--- a/gdb/common/common-inferior.h
+++ b/gdb/common/common-inferior.h
@@ -34,4 +34,8 @@ extern char *get_exec_file (int err);
    been set, then return NULL.  */
 extern const char *get_inferior_cwd ();
 
+/* Set the inferior current working directory.  This directory will be
+   entered by the debugger before executing the inferior.  */
+extern void set_inferior_cwd (const char *cwd);
+
 #endif /* ! COMMON_INFERIOR_H */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index c513a49c26..fc20a74bce 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -2059,8 +2059,10 @@ your program.  @xref{Environment, ,Your Program's Environment}.
 @item The @emph{working directory.}
 You can set your program's working directory with the command
 @code{set cwd}.  If you do not set any working directory with this
-command, your program will inherit @value{GDBN}'s working directory.
-@xref{Working Directory, ,Your Program's Working Directory}.
+command, your program will inherit @value{GDBN}'s working directory if
+native debugging, or @code{gdbserver}'s working directory if remote
+debugging.  @xref{Working Directory, ,Your Program's Working
+Directory}.
 
 @item The @emph{standard input and output.}
 Your program normally uses the same device for standard input and
@@ -2429,7 +2431,9 @@ Each time you start your program with @code{run}, the inferior will be
 initialized with the current working directory specified by the
 @code{set cwd} command.  If no directory has been specified by this
 command, then the inferior will inherit @value{GDBN}'s current working
-directory as its working directory.
+directory as its working directory if native debugging, or it will
+inherit @code{gdbserver}'s current working directory if remote
+debugging.
 
 You can also change @value{GDBN}'s current working directory by using
 the @code{cd} command.
@@ -2444,7 +2448,8 @@ Specify Files}.
 @item set cwd @r{[}@var{directory}@r{]}
 Set the inferior's working directory to @var{directory}.  If not
 given, @var{directory} uses @file{'~'}.  This has no effect on
-@value{GDBN}'s working directory.
+@value{GDBN}'s working directory.  This setting works for both native
+and remote debugging.
 
 @kindex show cwd
 @cindex show inferior's working directory
@@ -20982,6 +20987,10 @@ are:
 @tab @code{QEnvironmentReset}
 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
 
+@item @code{set-working-dir}
+@tab @code{QSetWorkingDir}
+@tab @code{cd}
+
 @item @code{conditional-breakpoints-packet}
 @tab @code{Z0 and Z1}
 @tab @code{Support for target-side breakpoint condition evaluation}
@@ -36770,6 +36779,30 @@ Reply:
 @table @samp
 @item OK
 The request succeeded.
+
+@item QSetWorkingDir:@var{hex-value}
+@anchor{QSetWorkingDir packet}
+@cindex set working directory, remote request
+@cindex @samp{QSetWorkingDir} packet
+On UNIX-like targets, it is possible to set the current working
+directory that @command{gdbserver} will enter before starting the
+inferior.  This packet is used to inform @command{gdbserver} of a
+directory into which it should enter during the startup process.
+
+The packet is composed by @var{hex-value}, an hex encoded
+representation of the directory to be entered by @command{gdbserver}.
+
+This packet is only transmitted when the user issues a @code{cd}
+command in @value{GDBN} (@pxref{Working Directory, ,Your Program's
+Working Directory}).
+
+This packet is only available in extended mode (@pxref{extended
+mode}).
+
+Reply:
+@table @samp
+@item OK
+The request succeeded.
 @end table
 
 This packet is not probed by default; the remote stub must request it,
@@ -36800,6 +36833,9 @@ Reply:
 @table @samp
 @item OK
 The request succeeded.
+
+@item E @var{nn}
+An error occurred.  The error number @var{nn} is given as hex digits.
 @end table
 
 This packet is not probed by default; the remote stub must request it,
diff --git a/gdb/gdbserver/inferiors.c b/gdb/gdbserver/inferiors.c
index e78ad4faf1..326d01f4d9 100644
--- a/gdb/gdbserver/inferiors.c
+++ b/gdb/gdbserver/inferiors.c
@@ -456,3 +456,12 @@ get_inferior_cwd ()
 {
   return current_inferior_cwd;
 }
+
+/* See common/common-inferior.h.  */
+
+void
+set_inferior_cwd (const char *cwd)
+{
+  xfree ((void *) current_inferior_cwd);
+  current_inferior_cwd = xstrdup (cwd);
+}
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index f4faff9d77..a159708632 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -869,6 +869,21 @@ handle_general_set (char *own_buf)
       return;
     }
 
+  if (startswith (own_buf, "QSetWorkingDir:"))
+    {
+      const char *p = own_buf + strlen ("QSetWorkingDir:");
+      std::string path = hex2str (p);
+
+      set_inferior_cwd (path.c_str ());
+
+      if (remote_debug)
+	debug_printf (_("[Changed current directory to %s]\n"),
+		      path.c_str ());
+      write_ok (own_buf);
+
+      return;
+    }
+
   /* Otherwise we didn't know what packet it was.  Say we didn't
      understand it.  */
   own_buf[0] = 0;
@@ -2345,7 +2360,8 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
       sprintf (own_buf,
 	       "PacketSize=%x;QPassSignals+;QProgramSignals+;"
 	       "QStartupWithShell+;QEnvironmentHexEncoded+;"
-	       "QEnvironmentReset+;QEnvironmentUnset+",
+	       "QEnvironmentReset+;QEnvironmentUnset+;"
+	       "QSetWorkingDir+",
 	       PBUFSIZ - 1);
 
       if (target_supports_catch_syscall ())
diff --git a/gdb/gdbserver/win32-low.c b/gdb/gdbserver/win32-low.c
index cc84d15c2f..b9fff29d74 100644
--- a/gdb/gdbserver/win32-low.c
+++ b/gdb/gdbserver/win32-low.c
@@ -562,6 +562,7 @@ static BOOL
 create_process (const char *program, char *args,
 		DWORD flags, PROCESS_INFORMATION *pi)
 {
+  const char *inferior_cwd = get_inferior_cwd ();
   BOOL ret;
 
 #ifdef _WIN32_WCE
@@ -586,7 +587,7 @@ create_process (const char *program, char *args,
 			FALSE,    /* inherit handles, not supported */
 			flags,    /* start flags */
 			NULL,     /* environment, not supported */
-			NULL,     /* current directory, not supported */
+			inferior_cwd,     /* current directory */
 			NULL,     /* start info, not supported */
 			pi);      /* proc info */
 #else
@@ -599,7 +600,7 @@ create_process (const char *program, char *args,
 			TRUE,     /* inherit handles */
 			flags,    /* start flags */
 			NULL,     /* environment */
-			NULL,     /* current directory */
+			inferior_cwd,     /* current directory */
 			&si,      /* start info */
 			pi);      /* proc info */
 #endif
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 178a3ca15f..a51a3d4e40 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -252,10 +252,9 @@ show_args_command (struct ui_file *file, int from_tty,
   deprecated_show_value_hack (file, from_tty, c, get_inferior_args ());
 }
 
-/* Set the inferior current working directory.  This directory will be
-   entered by GDB before executing the inferior.  */
+/* See common/common-inferior.h.  */
 
-static void
+void
 set_inferior_cwd (const char *cwd)
 {
   struct inferior *inf = current_inferior ();
diff --git a/gdb/remote.c b/gdb/remote.c
index 0963693a22..d900157ca9 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1428,6 +1428,7 @@ enum {
   PACKET_QPassSignals,
   PACKET_QCatchSyscalls,
   PACKET_QProgramSignals,
+  PACKET_QSetWorkingDir,
   PACKET_QStartupWithShell,
   PACKET_QEnvironmentHexEncoded,
   PACKET_QEnvironmentReset,
@@ -4637,6 +4638,8 @@ static const struct protocol_feature remote_protocol_features[] = {
     PACKET_QCatchSyscalls },
   { "QProgramSignals", PACKET_DISABLE, remote_supported_packet,
     PACKET_QProgramSignals },
+  { "QSetWorkingDir", PACKET_DISABLE, remote_supported_packet,
+    PACKET_QSetWorkingDir },
   { "QStartupWithShell", PACKET_DISABLE, remote_supported_packet,
     PACKET_QStartupWithShell },
   { "QEnvironmentHexEncoded", PACKET_DISABLE, remote_supported_packet,
@@ -9616,6 +9619,33 @@ extended_remote_environment_support (struct remote_state *rs)
       send_environment_packet (rs, "unset", "QEnvironmentUnset", el.c_str ());
 }
 
+/* Helper function to handle the change of the current working
+   directory in the remote.  */
+
+static void
+extended_remote_handle_inferior_cwd (struct remote_state *rs)
+{
+  if (packet_support (PACKET_QSetWorkingDir) != PACKET_DISABLE)
+    {
+      const char *inferior_cwd = get_inferior_cwd ();
+
+      if (inferior_cwd != NULL)
+	{
+	  std::string hexpath = bin2hex ((const gdb_byte *) inferior_cwd,
+					 strlen (inferior_cwd));
+
+	  xsnprintf (rs->buf, get_remote_packet_size (),
+		     "QSetWorkingDir:%s", hexpath.c_str ());
+	  putpkt (rs->buf);
+	  getpkt (&rs->buf, &rs->buf_size, 0);
+	  if (strcmp (rs->buf, "OK") != 0)
+	    error (_("\
+Remote replied unexpectedly while changing working directory: %s"),
+		   rs->buf);
+	}
+    }
+}
+
 /* In the extended protocol we want to be able to do things like
    "run" and have them basically work as expected.  So we need
    a special create_inferior function.  We support changing the
@@ -9658,6 +9688,8 @@ Remote replied unexpectedly while setting startup-with-shell: %s"),
 
   extended_remote_environment_support (rs);
 
+  extended_remote_handle_inferior_cwd (rs);
+
   /* Now restart the remote server.  */
   run_worked = extended_remote_run (args) != -1;
   if (!run_worked)
@@ -14126,6 +14158,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
   add_packet_config_cmd (&remote_protocol_packets[PACKET_QProgramSignals],
 			 "QProgramSignals", "program-signals", 0);
 
+  add_packet_config_cmd (&remote_protocol_packets[PACKET_QSetWorkingDir],
+			 "QSetWorkingDir", "set-working-dir", 0);
+
   add_packet_config_cmd (&remote_protocol_packets[PACKET_QStartupWithShell],
 			 "QStartupWithShell", "startup-with-shell", 0);
 
diff --git a/gdb/testsuite/gdb.base/set-cwd.exp b/gdb/testsuite/gdb.base/set-cwd.exp
index 3a6ffd3862..d3104287a0 100644
--- a/gdb/testsuite/gdb.base/set-cwd.exp
+++ b/gdb/testsuite/gdb.base/set-cwd.exp
@@ -15,10 +15,16 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-if { ![isnative] || [is_remote target] || [is_remote host]
-     || [target_info gdb_protocol] == "extended-remote" } then {
-    untested "not implemented on gdbserver"
-    return
+if { [target_info exists gdb_protocol] } {
+    if { [target_info gdb_protocol] == "remote" } {
+	untested "not implemented on native-gdbserver"
+	return
+    }
+
+    load_lib gdbserver-support.exp
+    if { [skip_gdbserver_tests] } {
+	return
+    }
 }
 
 standard_testfile
-- 
2.13.3