linux-kernel - [PATCH] kgdb: Ignore DIE_PAGE_FAULT event in notify handler [2.6.32] kernel

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Date:	Mon, 11 Aug 2014 15:31:58 -0700
From:	Sadasivan Shaiju <sshaiju@...sta.com>
To:	jason.wessel@...driver.com
Cc:	linux-kernel@...r.kernel.org, shaiju_sada@...oo.com
Subject: [PATCH] kgdb: Ignore DIE_PAGE_FAULT event in notify handler [2.6.32] kernel

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  merge this  patch to the main line community .  If any
questions  please contact me  at sshaiju@...sta.com
(shaiju_sada@...oo.com)

Regards,
shaiju

Download attachment "4995-kgdb-Ignore-DIE_PAGE_FAULT-event-in-notify-handler.patch" of type "application/octet-stream" (1256 bytes)