PATCH[2.6.32] kgdb patch

[Sadasivan Shaiju <sshaiju@mvista.com>]

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Hi,

I  work for Montavista (Cavium Inc) as  a  Technical  Lead .  I want to
push some  of the kernel  patches to  rt community (2.6.32 kernel 2.6.33
rt patch)  , so  that  It  will  go  to  the  main line These patches  are
reviewed  and approved  by  our system Architect.  I request  you to
include  in the main line .  These  issues  were  reported  by our
customer CISCO.


Problem Description:
If  kprobes  is  enabled  along  with  kgdb, kgdb gives a SIGHUP on the
host side.

Root Cause:
Inside the do_page_fault() (arch/mips/mm/fault.c) there is a call to
notify_die() when kprobes is enabled.

When kgdb is enabled the register_die_notifier() handler catches this
exception
(which is 3 - TLB miss on store) and says it does not know it and returns
it as
a SIGHUP.

How Solved:
Made kgdb ignore this particular die notification (cmd == DIE_PAGE_FAULT)
in its
handler.


I  request you to include the above patch in to the main line kernel . If
any questions  please contact me at  sshaiju@mvista.com
(shaiju_sada@yahoo.com)


Regards,
Shaiju.

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From 056caa9991512704cb39f65828e1ffea47830c6c Mon Sep 17 00:00:00 2001
From: sadasivan shaiju <shaiju@localhost.localdomain>
Date: Wed, 27 Jul 2011 14:54:39 -0700
Subject: [PATCH] kgdb: Ignore DIE_PAGE_FAULT event in notify handler

Source: MontaVista Software, LLC
MR: 45280
Type: Defect Fix
Disposition: Needs submitting to kernel.org
ChangeID: 5bec09f7ec0a4775169f5cba16976bc3a6b45598
Description:

Ignore notify_die() from do_pagefault(), in kgdb's register_die_notifier()
handler

Signed-off-by: Sadasivan <sshaiju@mvista.com>
Signed-off-by: Dale Farnsworth <dfarnsworth@mvista.com>
---
 arch/mips/kernel/kgdb.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
index 50c9bb8..3e4ae31 100644
--- a/arch/mips/kernel/kgdb.c
+++ b/arch/mips/kernel/kgdb.c
@@ -191,6 +191,11 @@ static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd,
 	struct pt_regs *regs = args->regs;
 	int trap = (regs->cp0_cause & 0x7c) >> 2;
 
+        /* ignore the notify_die() from do_page_fault(), which is meant for kprobes */
+
+	if(cmd == DIE_PAGE_FAULT)
+		return NOTIFY_DONE;       
+
 	/* Userpace events, ignore. */
 	if (user_mode(regs))
 		return NOTIFY_DONE;
-- 
1.7.0.1