[rfc] remote, btrace: add branch tracing protocol to Qbtrace packet

[markus.t.metzger@intel.com]

From: Markus Metzger <markus.t.metzger@intel.com>

We might want to add support for LBR branch tracing in the future.

To prepare for this, I would specify the branch trace recording method
in the Qbtrace packet when requesting branch tracing.

The supported branch trace recording methods will further be listed
in response to a QSupported packet.

The patch works but I'm not sure whether it is in the spirit of
the remote serial protocol.


This patch does not enable GDB to support different recording methods.
GDB still only supports BTS-based branch trace recording.

But I hope this will avoid having to change the remote serial protocol
later on when we want to add the new recording method.


2013-02-22 Markus Metzger  <markus.t.metzger@intel.com>
---
 gdb/doc/gdb.texinfo    |   10 +++++++---
 gdb/gdbserver/server.c |    6 +++---
 gdb/remote.c           |    4 ++--
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index d6842f1..ec934a5 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -37570,7 +37570,10 @@ rather than reporting the hit to @value{GDBN}.
 The remote stub understands the @samp{qbtrace} packet.
 
 @item Qbtrace
-The remote stub understands the @samp{Qbtrace} packet.
+The remote stub understands the @samp{Qbtrace} packet.  The branch
+trace recording method will be specified after the packet name
+separated by a single colon (@code{:}).  There will be one entry for
+each supported branch trace recording method.
 
 @end table
 
@@ -37951,8 +37954,9 @@ No new branch trace data is available.
 A badly formed request or an error was encountered.
 @end table
 
-@item Qbtrace:on
-Enable branch tracing for the current thread.
+@item Qbtrace:@var{method}
+Enable branch tracing for the current thread using the @var{method}
+branch trace recording method.
 
 Reply:
 @table @samp
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index c335af7..debef5d 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -463,12 +463,12 @@ handle_btrace_general_set (char *own_buf)
 
   err = NULL;
 
-  if (strcmp (op, "on") == 0)
+  if (strcmp (op, "bts") == 0)
     err = handle_btrace_enable (thread);
   else if (strcmp (op, "off") == 0)
     err = handle_btrace_disable (thread);
   else
-    err = "E.Bad Qbtrace operation. Use on or off.";
+    err = "E.Bad Qbtrace operation. Use bts or off.";
 
   if (err != 0)
     strcpy (own_buf, err);
@@ -1828,7 +1828,7 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
       if (target_supports_btrace ())
 	{
 	  strcat (own_buf, ";qbtrace+");
-	  strcat (own_buf, ";Qbtrace+");
+	  strcat (own_buf, ";Qbtrace:bts+");
 	  strcat (own_buf, ";qXfer:btrace:read+");
 	}
 
diff --git a/gdb/remote.c b/gdb/remote.c
index 6f95125..2322ece 100755
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -11164,7 +11164,7 @@ send_Qbtrace (ptid_t ptid, int enable)
   set_general_thread (ptid);
 
   buf += xsnprintf (buf, endbuf - buf, "%s:", packet->name);
-  buf += xsnprintf (buf, endbuf - buf, enable ? "on" : "off");
+  buf += xsnprintf (buf, endbuf - buf, enable ? "bts" : "off");
   putpkt (rs->buf);
   getpkt (&rs->buf, &rs->buf_size, 0);
 
@@ -11928,7 +11928,7 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
        "qbtrace", "query-btrace", 0);
 
   add_packet_config_cmd (&remote_protocol_packets[PACKET_Qbtrace],
-       "Qbtrace", "enable-btrace", 0);
+       "Qbtrace:bts", "enable-btrace", 0);
 
   add_packet_config_cmd (&remote_protocol_packets[PACKET_qXfer_btrace],
        "qXfer:btrace", "read-btrace", 0);
-- 
1.7.1