Fwd: [PATCH] kdb: Avoid using dbg_io_ops until it is initialized

Fwd: [PATCH] kdb: Avoid using dbg_io_ops until it is initialized

[Tim Bird]

Jason,

This patch has apparently fallen through the cracks.  Can you please apply?
This fixes a kernel panic for a use case where I'm setting a breakpoint
from kdb_cmds on kernel startup.  In this case, without this patch
dbg_io_ops is used before it is initialized.

Thanks,
 -- Tim

-------- Original Message --------
Subject: [PATCH] kdb:  Avoid using dbg_io_ops until it is initialized
Date: Wed, 21 Sep 2011 13:19:12 -0700
From: Tim Bird <tim.bird@am.sony.com>
To: Jason Wessel <jason.wessel@windriver.com>
CC: kgdb-bugreport@lists.sourceforge.net	<kgdb-bugreport@lists.sourceforge.net>, linux kernel	<linux-kernel@vger.kernel.org>

This fixes a bug with setting a breakpoint during kdb initialization
(from kdb_cmds).  Any call to kdb_printf() before the initialization
of the kgdboc serial console driver (which happens much later in
bootup than kdb_init), results in kernel panic due to the use of
dbg_io_ops before it is initialized.

Signed-off-by: Tim Bird <tim.bird@am.sony.com>
---
 kernel/debug/kdb/kdb_io.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index c9b7f4f..3bc995f 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -675,7 +675,7 @@ kdb_printit:
 	if (!dbg_kdb_mode && kgdb_connected) {
 		gdbstub_msg_write(kdb_buffer, retlen);
 	} else {
-		if (!dbg_io_ops->is_console) {
+		if (dbg_io_ops && !dbg_io_ops->is_console) {
 			len = strlen(kdb_buffer);
 			cp = kdb_buffer;
 			while (len--) {
-- 
1.7.2.3

Re: Fwd: [PATCH] kdb: Avoid using dbg_io_ops until it is initialized

[Jason Wessel]

On 03/20/2012 11:34 AM, Tim Bird wrote:
> Jason,
>
> This patch has apparently fallen through the cracks.  Can you please apply?
> This fixes a kernel panic for a use case where I'm setting a breakpoint
> from kdb_cmds on kernel startup.  In this case, without this patch
> dbg_io_ops is used before it is initialized.

Many thanks Tim.

I'll review/regression test this and add it to the merge queue.   I found another patch from you in the same week from last year that I will also review.  I am not exactly sure why these never made it to my review list, but what once was lost is now found.

Cheers,
Jason.