[PATCH v3 5/5] Extend "set cwd" to work on gdbserver

[Sergio Durigan Junior <sergiodj@redhat.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) and 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".
	(show_cwd_command): Expand text to include remote debugging.
	* remote.c: Add PACKET_QSetWorkingDir.
	(remote_protocol_features) <QSetWorkingDir>: New entry for
	PACKET_QSetWorkingDir.
	(extended_remote_set_inferior_cwd): New function.
	(extended_remote_create_inferior): Call
	"extended_remote_set_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 the inferior's 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                           | 12 ++++++++++++
 gdb/common/common-inferior.h       |  3 +++
 gdb/doc/gdb.texinfo                | 39 +++++++++++++++++++++++++++++++++++---
 gdb/gdbserver/inferiors.c          |  9 +++++++++
 gdb/gdbserver/server.c             | 18 +++++++++++++++++-
 gdb/gdbserver/win32-low.c          | 15 ++++++++++++---
 gdb/infcmd.c                       |  7 ++++---
 gdb/remote.c                       | 37 ++++++++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.base/set-cwd.exp | 11 +++++++++--
 9 files changed, 139 insertions(+), 12 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index c131713293..4ac340eeb5 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -23,6 +23,14 @@
 
 * New features in the GDB remote stub, GDBserver
 
+  ** GDBserver is now able to set the inferior's current working
+     directory.
+
+     The user can set the desired working directory to be used by the
+     remote inferior on GDB, using the new "set cwd" command, which
+     will instruct GDB to tell GDBserver about this directory change
+     the next time an inferior is run.
+
   ** New "--selftest" command line option runs some GDBserver self
      tests.  These self tests are disabled in releases.
 
@@ -56,6 +64,10 @@ QEnvironmentReset
 QStartupWithShell
   Indicates whether the inferior must be started with a shell or not.
 
+QSetWorkingDir
+  Tell GDBserver that the inferior to be started should use a specific
+  working directory.
+
 * 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..26acddc84a 100644
--- a/gdb/common/common-inferior.h
+++ b/gdb/common/common-inferior.h
@@ -34,4 +34,7 @@ extern char *get_exec_file (int err);
    been set, then return NULL.  */
 extern const char *get_inferior_cwd ();
 
+/* Set the inferior current working directory.  */
+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 899afb92b6..7434de2a68 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
@@ -2439,7 +2441,9 @@ 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.
@@ -20993,6 +20997,10 @@ 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{set cwd}
+
 @item @code{conditional-breakpoints-packet}
 @tab @code{Z0 and Z1}
 @tab @code{Support for target-side breakpoint condition evaluation}
@@ -36781,6 +36789,28 @@ 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
+This packet is used to inform @command{gdbserver} of the intended
+current working directory for programs that are going to be executed.
+
+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{set cwd}
+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,
@@ -36811,6 +36841,9 @@ 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 f3eee31052..14f8a732a7 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;
@@ -2355,7 +2370,8 @@ 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..62b222d2fa 100644
--- a/gdb/gdbserver/win32-low.c
+++ b/gdb/gdbserver/win32-low.c
@@ -562,10 +562,11 @@ 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
-  wchar_t *p, *wprogram, *wargs;
+  wchar_t *p, *wprogram, *wargs, *wcwd = NULL;
   size_t argslen;
 
   wprogram = alloca ((strlen (program) + 1) * sizeof (wchar_t));
@@ -579,6 +580,14 @@ create_process (const char *program, char *args,
   wargs = alloca ((argslen + 1) * sizeof (wchar_t));
   mbstowcs (wargs, args, argslen + 1);
 
+  if (inferior_cwd != NULL)
+    {
+      size_t cwdlen = strlen (inferior_cwd);
+
+      wcwd = alloca ((cwdlen + 1) * sizeof (wchar_t));
+      mbstowcs (wcwd, inferior_cwd, cwdlen + 1);
+    }
+
   ret = CreateProcessW (wprogram, /* image name */
 			wargs,    /* command line */
 			NULL,     /* security, not supported */
@@ -586,7 +595,7 @@ create_process (const char *program, char *args,
 			FALSE,    /* inherit handles, not supported */
 			flags,    /* start flags */
 			NULL,     /* environment, not supported */
-			NULL,     /* current directory, not supported */
+			wcwd,     /* current directory */
 			NULL,     /* start info, not supported */
 			pi);      /* proc info */
 #else
@@ -599,7 +608,7 @@ 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 4c5bbfdbf2..f483a33a44 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -250,9 +250,9 @@ 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.  */
+/* See common/common-inferior.h.  */
 
-static void
+void
 set_inferior_cwd (const char *cwd)
 {
   if (*cwd == '\0')
@@ -292,7 +292,8 @@ show_cwd_command (struct ui_file *file, int from_tty,
     fprintf_filtered (gdb_stdout,
 		      _("\
 You have not set the inferior's current working directory.\n\
-The inferior will inherit GDB's cwd.\n"));
+The inferior will inherit GDB's cwd if native debugging, or gdbserver's\n\
+cwd if remote debugging.\n"));
   else
     fprintf_filtered (gdb_stdout,
 		      _("Current working directory that will be used "
diff --git a/gdb/remote.c b/gdb/remote.c
index 33b0c2a09d..18d3aaea3f 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1434,6 +1434,7 @@ enum {
   PACKET_QPassSignals,
   PACKET_QCatchSyscalls,
   PACKET_QProgramSignals,
+  PACKET_QSetWorkingDir,
   PACKET_QStartupWithShell,
   PACKET_QEnvironmentHexEncoded,
   PACKET_QEnvironmentReset,
@@ -4665,6 +4666,8 @@ 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,
@@ -9644,6 +9647,35 @@ extended_remote_environment_support (struct remote_state *rs)
       send_environment_packet (rs, "unset", "QEnvironmentUnset", el.c_str ());
 }
 
+/* Helper function to set the current working directory for the
+   inferior in the remote.  */
+
+static void
+extended_remote_set_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 (packet_ok (rs->buf,
+			 &remote_protocol_packets[PACKET_QSetWorkingDir])
+	      != PACKET_OK)
+	    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
@@ -9686,6 +9718,8 @@ Remote replied unexpectedly while setting startup-with-shell: %s"),
 
   extended_remote_environment_support (rs);
 
+  extended_remote_set_inferior_cwd (rs);
+
   /* Now restart the remote server.  */
   run_worked = extended_remote_run (args) != -1;
   if (!run_worked)
@@ -14185,6 +14219,9 @@ 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 f2700ec44d..32458e384e 100644
--- a/gdb/testsuite/gdb.base/set-cwd.exp
+++ b/gdb/testsuite/gdb.base/set-cwd.exp
@@ -15,11 +15,18 @@
 # 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 { [use_gdb_stub] || [target_info gdb_protocol] == "extended-remote" } {
-    untested "not implemented on gdbserver"
+if { [use_gdb_stub] } {
+    untested "not valid on native-gdbserver"
     return
 }
 
+if { [target_info gdb_protocol] == "remote" } {
+    load_lib gdbserver-support.exp
+    if { [skip_gdbserver_tests] } {
+	return
+    }
+}
+
 standard_testfile
 
 if { [prepare_for_testing "failed to prepare" $testfile $srcfile debug] } {
-- 
2.13.3