[PATCH] Locate executables on remote stubs without multiprocess extensions

[Gary Benson <gbenson at redhat dot com>]

Hi all,

This commit allows GDB to determine filenames of main executables
when debugging using remote stubs without multiprocess extensions.
The qXfer:exec-file:read packet is extended to allow an empty
annex, with the meaning that the remote stub should supply the
filename of whatever it thinks is the current process.

Built and regtested on RHEL6.6 x86_64.

Is this ok to commit?

Cheers,
Gary


gdb/ChangeLog:

	* remote.c (remote_add_inferior): Call exec_file_locate_attach
	for fake PIDs as well as real ones.
	(remote_pid_to_exec_file): Send empty annex if PID is fake.

gdb/doc/ChangeLog:

	* gdb.texinfo (General Query Packets): Document
	qXfer:exec-file:read with empty annex.

gdb/gdbserver/ChangeLog:

	* server.c (handle_qxfer_exec_file): Use current process
	if annex is empty.
---
 gdb/ChangeLog           |    6 ++++++
 gdb/doc/ChangeLog       |    5 +++++
 gdb/doc/gdb.texinfo     |    3 ++-
 gdb/gdbserver/ChangeLog |    5 +++++
 gdb/gdbserver/server.c  |   25 ++++++++++++++++++++-----
 gdb/remote.c            |   15 ++++++++++++---
 6 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 9e2787d..63e063a 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -36558,7 +36558,8 @@ by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
 Return the full absolute name of the file that was executed to create
 a process running on the remote system.  The annex specifies the
 numeric process ID of the process to query, encoded as a hexadecimal
-number.
+number.  If the annex part is empty the remote stub should return the
+filename corresponding to the currently executing process.
 
 This packet is not probed by default; the remote stub must request it,
 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index d2e20d9..516a311 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -1144,17 +1144,32 @@ handle_qxfer_exec_file (const char *const_annex,
 			gdb_byte *readbuf, const gdb_byte *writebuf,
 			ULONGEST offset, LONGEST len)
 {
-  char *annex, *file;
+  char *file;
   ULONGEST pid;
   int total_len;
 
   if (the_target->pid_to_exec_file == NULL || writebuf != NULL)
     return -2;
 
-  annex = alloca (strlen (const_annex) + 1);
-  strcpy (annex, const_annex);
-  annex = unpack_varlen_hex (annex, &pid);
-  if (annex[0] != '\0' || pid == 0)
+  if (const_annex[0] == '\0')
+    {
+      if (current_thread == NULL)
+	return -1;
+
+      pid = pid_of (current_thread);
+    }
+  else
+    {
+      char *annex = alloca (strlen (const_annex) + 1);
+
+      strcpy (annex, const_annex);
+      annex = unpack_varlen_hex (annex, &pid);
+
+      if (annex[0] != '\0')
+	return -1;
+    }
+
+  if (pid < 0)
     return -1;
 
   file = (*the_target->pid_to_exec_file) (pid);
diff --git a/gdb/remote.c b/gdb/remote.c
index 099ddbb..6b18960 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1558,7 +1558,7 @@ remote_add_inferior (int fake_pid_p, int pid, int attached,
 
   /* If no main executable is currently open then attempt to
      open the file that was executed to create this inferior.  */
-  if (try_open_exec && !fake_pid_p && get_exec_file (0) == NULL)
+  if (try_open_exec && get_exec_file (0) == NULL)
     exec_file_locate_attach (pid, 1);
 
   return inf;
@@ -11710,7 +11710,8 @@ static char *
 remote_pid_to_exec_file (struct target_ops *self, int pid)
 {
   static char *filename = NULL;
-  char annex[9];
+  struct inferior *inf;
+  char *annex = NULL;
 
   if (packet_support (PACKET_qXfer_exec_file) != PACKET_ENABLE)
     return NULL;
@@ -11718,7 +11719,15 @@ remote_pid_to_exec_file (struct target_ops *self, int pid)
   if (filename != NULL)
     xfree (filename);
 
-  xsnprintf (annex, sizeof (annex), "%x", pid);
+  inf = find_inferior_pid (pid);
+  if (inf != NULL && !inf->fake_pid_p)
+    {
+      const int annex_size = 9;
+
+      annex = alloca (annex_size);
+      xsnprintf (annex, annex_size, "%x", pid);
+    }
+
   filename = target_read_stralloc (&current_target,
 				   TARGET_OBJECT_EXEC_FILE, annex);
 
-- 
1.7.1