From: Frederic Weisbecker <fweisbec@gmail.com>
To: "K.Prasad" <prasad@linux.vnet.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
Alan Stern <stern@rowland.harvard.edu>
Subject: Re: [RFC Patch 2/2][Bugfix][x86][hw-breakpoint] Fix return-code to notifier chain in hw_breakpoint_handler
Date: Thu, 31 Dec 2009 01:33:49 +0100 [thread overview]
Message-ID: <20091231003348.GB23808@nowhere> (raw)
In-Reply-To: <20091226182833.GC9494@in.ibm.com>
On Sat, Dec 26, 2009 at 11:58:33PM +0530, K.Prasad wrote:
> The hw-breakpoint handler will return NOTIFY_DONE for user-space breakpoints
> to generate SIGTRAP signal (and not for kernel-space addresses).
>
> Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
> ---
> arch/x86/kernel/hw_breakpoint.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> Index: linux-2.6-tip/arch/x86/kernel/hw_breakpoint.c
> ===================================================================
> --- linux-2.6-tip.orig/arch/x86/kernel/hw_breakpoint.c
> +++ linux-2.6-tip/arch/x86/kernel/hw_breakpoint.c
> @@ -502,8 +502,6 @@ static int __kprobes hw_breakpoint_handl
> rcu_read_lock();
>
> bp = per_cpu(bp_per_reg[i], cpu);
> - if (bp)
> - rc = NOTIFY_DONE;
> /*
> * Reset the 'i'th TRAP bit in dr6 to denote completion of
> * exception handling
> @@ -517,6 +515,13 @@ static int __kprobes hw_breakpoint_handl
> rcu_read_unlock();
> break;
> }
> + /*
> + * Further processing in do_debug() is needed for a) user-space
> + * breakpoints (to generate signals) and b) when the system has
> + * taken exception due to multiple causes
> + */
> + if (bp->attr.bp_addr < TASK_SIZE)
> + rc = NOTIFY_DONE;
>
> perf_bp_event(bp, args->regs);
>
>
Looks good. This stops any further checks though. This
is fine in case we have the DR_STEP bit as we will
toggle to NOTIFY_DONE. But what about vm86 case? Is it
possible we might still have something to handle in this
side? (although I don't quite understand how we can have
a breakpoint triggered in vm86 mode).
next prev parent reply other threads:[~2009-12-31 0:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20091226175533.149765731@linux.vnet.ibm.com>
2009-12-26 18:27 ` [RFC Patch 1/2][Bugfix][x86][hw-breakpoint] Clear reserved bits of DR6 in do_debug() K.Prasad
2009-12-30 23:45 ` Frederic Weisbecker
2009-12-31 18:49 ` K.Prasad
2010-01-10 3:22 ` Frederic Weisbecker
2009-12-26 18:28 ` [RFC Patch 2/2][Bugfix][x86][hw-breakpoint] Fix return-code to notifier chain in hw_breakpoint_handler K.Prasad
2009-12-31 0:33 ` Frederic Weisbecker [this message]
2009-12-31 0:38 ` Frederic Weisbecker
2009-12-31 19:02 ` K.Prasad
2010-01-10 3:18 ` Frederic Weisbecker
2010-01-11 19:15 ` Jan Kiszka
2010-01-16 19:41 ` K.Prasad
2010-01-20 6:01 ` K.Prasad
2010-01-22 9:14 ` Jan Kiszka
2010-01-22 9:21 ` K.Prasad
2010-01-25 22:21 ` Frederic Weisbecker
2010-01-27 10:29 ` K.Prasad
2009-12-31 0:44 ` Frederic Weisbecker
2010-01-25 22:11 ` Frederic Weisbecker
2010-01-27 10:28 ` K.Prasad
2010-01-27 16:11 ` Frederic Weisbecker
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