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

[Pedro Alves <palves at redhat dot com>]

On 09/21/2017 11:59 PM, Sergio Durigan Junior wrote:
> 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.
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Unix implementation detail.

> 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.

Unix implementation detail.  That's not how it works for Windows.

> 
> 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}.

Elsewhere in the manual we say "the remote server" instead of @code{gdbserver},
because not all remote debugging uses gdbserver.

>  
>  @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.

Ditto.

>  
>  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}

I think it'd be clearer to say @var{directory}, and
then say below that @var{directory} is an hex-encoded
string, like you're already doing.  That's what we do
elsewhere in the manual.

> +@anchor{QSetWorkingDir packet}
> +@cindex set working directory, remote request
> +@cindex @samp{QSetWorkingDir} packet
> +This packet is used to inform @command{gdbserver} of the intended

Ditto re. "gdbserver".

> +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 transmitted when set cwd" suggests to me that
the packet is sent immediately when the user types "set cwd".

  This packet is only transmitted if the user explicitly
  specifies a directory with the @kdb{set cwd} command.

note: 
  s/when/if/.
  s/@code/@kdb

> 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 ());

Please tweak the debug string to be clear that this is the
inferior's cwd, not gdbserver's.

> +      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"));

gdbserver -> remote server.

> +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)
> +	{

What happens if you do:

 set cwd foo
 run
 kill
 set cwd    # clear
 run

Do we clear the cwd on the remote end or we do we fail the
NULL check above?

> +/* See common/common-inferior.h.  */
> +
> +void
> +set_inferior_cwd (const char *cwd)
> +{
> +  xfree ((void *) current_inferior_cwd);
> +  current_inferior_cwd = xstrdup (cwd);
> +}

This always sets to non-NULL.  So is it really possible
to get back to the original clear state?  Doesn't look like it?
Do we have a test for that?


> +	  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);

Again "changing".   Maybe say "setting the inferior's working directory"
instead.


> +	}
> +    }
> +}
> +
>  /* 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"

There are many other boards that set use_gdb_stub, not just
native-gdbserver.  Other testcases say:

untested "skipping tests due to use_gdb_stub"


>      return
>  }
>  
> +if { [target_info gdb_protocol] == "remote" } {
> +    load_lib gdbserver-support.exp
> +    if { [skip_gdbserver_tests] } {
> +	return
> +    }
> +}
> +

Please remember to drop this part.

>  standard_testfile
>  
>  if { [prepare_for_testing "failed to prepare" $testfile $srcfile debug] } {
> 


Thanks,
Pedro Alves