From: Oleg Nesterov <oleg@redhat.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Anton Arapov <anton@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-kernel@vger.kernel.org,
Jim Keniston <jkenisto@linux.vnet.ibm.com>
Subject: Re: [PATCH 3/5] uprobes: Fix UPROBE_SKIP_SSTEP checks in handle_swbp()
Date: Sat, 29 Sep 2012 19:42:28 +0200 [thread overview]
Message-ID: <20120929174228.GA27035@redhat.com> (raw)
In-Reply-To: <20120924200825.GA25264@redhat.com>
On 09/24, Oleg Nesterov wrote:
>
> Anyway,
>
> > for example
> > 0f 1f 40 00
>
> OK, thanks, objdump reports "nopl 0x0(%rax)", looks fine.
>
> But. I do not see how __skip_sstep() can handle this case correctly.
> Not only it should update regs->ip afaics, it should also account 2
> extra bytes _after_ 0f 1f.
>
> > 0f 1f 44 00 00
>
> OK, nopl 0x0(%rax,%rax,1), but in this case we need to skip 3
> extra bytes.
>
>
> I am starting to think this code is broken and we should simply remove
> all checks except 0x66 and 0x90. In this case we do not even need to
> update regs->ip.
>
> Otherwise this code needs to know the insn's length.
>
> Right?
OK, I verified that the application is really killed by SIGILL if
you probe such an instruction. I'll send the fix which simply removes
this code. I do not know how to figure out the actual insn length.
Oleg.
next prev parent reply other threads:[~2012-09-29 17:41 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-14 17:15 [PATCH 0/5] uprobes: handle_swbp() fixes Oleg Nesterov
2012-09-14 17:15 ` [PATCH 1/5] uprobes: Do not leak UTASK_BP_HIT if find_active_uprobe() fails Oleg Nesterov
2012-09-14 17:35 ` Oleg Nesterov
2012-09-20 13:53 ` Srikar Dronamraju
2012-09-14 17:15 ` [PATCH 2/5] uprobes: Do not setup ->active_uprobe/state prematurely Oleg Nesterov
2012-09-20 13:55 ` Srikar Dronamraju
2012-09-14 17:15 ` [PATCH 3/5] uprobes: Fix UPROBE_SKIP_SSTEP checks in handle_swbp() Oleg Nesterov
2012-09-15 7:39 ` Ananth N Mavinakayanahalli
2012-09-15 15:01 ` Oleg Nesterov
2012-09-17 17:20 ` Srikar Dronamraju
2012-09-18 16:07 ` Oleg Nesterov
2012-09-20 14:43 ` Srikar Dronamraju
2012-09-24 20:08 ` Oleg Nesterov
2012-09-29 17:42 ` Oleg Nesterov [this message]
2012-09-20 14:05 ` Srikar Dronamraju
2012-09-14 17:16 ` [PATCH 4/5] uprobes: Kill UTASK_BP_HIT state Oleg Nesterov
2012-09-16 14:38 ` Oleg Nesterov
2012-09-20 14:06 ` Srikar Dronamraju
2012-09-14 17:16 ` [PATCH 5/5] uprobes: Move clear_thread_flag(TIF_UPROBE) to uprobe_notify_resume() Oleg Nesterov
2012-09-20 14:06 ` Srikar Dronamraju
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