linux-kernel - [PATCH] FRV: Reinstate null behaviour for the GDB remote protocol 'p' command

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Date:	Wed, 09 Jun 2010 19:52:22 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	dhowells@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH] FRV: Reinstate null behaviour for the GDB remote protocol 'p'
	command

Reinstate the null behaviour that the in-kernel gdbstub had for the GDB remote
protocol 'p' command (retrieve a single register value) prior to the following
commit:

	commit 7ca8b9c0dafd1cb36289aa4c92c7beae7adcd34f
	Author: David Howells <dhowells@...hat.com>
	Date:   Mon May 24 14:32:54 2010 -0700
	Subject: frv: extend gdbstub to support more features of gdb

Before that, the 'p' command just returned an empty reply, which causes gdb to
then go and use the 'g' command.  However, since that commit, the 'p' command
returns an error string, which causes gdb to abort its connection to the
target.

Not all gdb versions are affected, some use try 'g' first, and if that works,
don't bother with 'p', and so don't see the error.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 arch/frv/kernel/gdb-stub.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)


diff --git a/arch/frv/kernel/gdb-stub.c b/arch/frv/kernel/gdb-stub.c
index 84d103c..a4dba6b 100644
--- a/arch/frv/kernel/gdb-stub.c
+++ b/arch/frv/kernel/gdb-stub.c
@@ -1789,6 +1789,12 @@ void gdbstub(int sigval)
 			flush_cache = 1;
 			break;
 
+			/* pNN: Read value of reg N and return it */
+		case 'p':
+			/* return no value, indicating that we don't support
+			 * this command and that gdb should use 'g' instead */
+			break;
+
 			/* PNN,=RRRRRRRR: Write value R to reg N return OK */
 		case 'P':
 			ptr = &input_buffer[1];

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