From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@hack.frob.com>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, ananth@in.ibm.com,
a.p.zijlstra@chello.nl, mingo@redhat.com,
srikar@linux.vnet.ibm.com
Subject: Re: Q: user_enable_single_step() && update_debugctlmsr()
Date: Wed, 01 Aug 2012 15:32:37 +0200 [thread overview]
Message-ID: <50192FF5.1060208@linutronix.de> (raw)
In-Reply-To: <20120801130118.GA2386@redhat.com>
On 08/01/2012 03:01 PM, Oleg Nesterov wrote:
> Lets ignore uprobes which needs the changes anyway. This is
> only used by ptrace and the task is stopped. So, unless I missed
> something obvious, this update_debugctlmsr() is simply unneeded,
> __switch_to/__switch_to_xtra should notice _TIF_BLOCKSTEP and do
> update_debugctlmsr(DEBUGCTLMSR_BTF).
It looks like it unless a processes ptraces itself (which does not make
much sense anyway).
> But, worse, isn't it wrong? Suppose that debugger switches to
> another TIF_SINGLESTEP&& !TIF_BLOCKSTEP task, in this case
> we "leak" DEBUGCTLMSR_BTF, no?
__switch_to_xtra() should notice the difference in the TIF_BLOCKSTEP
flag and disable it.
> IOW, it seems to me we could safely remove update_debugctlmsr()
> arch/x86/kernel/step.c. However, if we want to re-use this code
> in uprobes, then we probably need to add "if (child == current)".
It looks that way.
>
> Or I am totally confused. Help!
>
> Oleg.
Sebastian
next prev parent reply other threads:[~2012-08-01 13:32 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-26 15:20 [PATCH] uprobes: don't enable/disable signle step if the user did it Sebastian Andrzej Siewior
2012-07-26 17:31 ` Oleg Nesterov
2012-07-27 17:39 ` Sebastian Andrzej Siewior
2012-07-27 18:04 ` Oleg Nesterov
2012-07-26 17:38 ` Sebastian Andrzej Siewior
2012-07-30 11:06 ` Ananth N Mavinakayanahalli
2012-07-30 14:16 ` Oleg Nesterov
2012-07-30 15:15 ` Sebastian Andrzej Siewior
2012-07-31 4:01 ` Ananth N Mavinakayanahalli
2012-07-31 5:22 ` Srikar Dronamraju
2012-07-31 17:38 ` Oleg Nesterov
2012-07-31 11:52 ` [PATCH 1/2] uprobes: Use a helper instead of ptrace's single step enable Sebastian Andrzej Siewior
2012-07-31 11:52 ` [PATCH 2/2] x86/uprobes: implement x86 specific arch_uprobe_*_step Sebastian Andrzej Siewior
2012-07-31 17:51 ` Oleg Nesterov
2012-07-31 19:30 ` Sebastian Andrzej Siewior
2012-08-01 12:26 ` Oleg Nesterov
2012-08-01 13:01 ` Q: user_enable_single_step() && update_debugctlmsr() Oleg Nesterov
2012-08-01 13:32 ` Sebastian Andrzej Siewior [this message]
2012-08-01 13:46 ` Oleg Nesterov
2012-08-01 13:54 ` Sebastian Andrzej Siewior
2012-08-01 14:01 ` Oleg Nesterov
2012-08-01 14:21 ` Sebastian Andrzej Siewior
2012-08-01 14:31 ` Oleg Nesterov
2012-08-01 14:47 ` Oleg Nesterov
2012-08-01 14:51 ` Sebastian Andrzej Siewior
2012-08-01 15:01 ` Oleg Nesterov
2012-08-01 15:12 ` Sebastian Andrzej Siewior
2012-08-01 15:14 ` Oleg Nesterov
2012-08-01 18:46 ` Sebastian Andrzej Siewior
2012-08-02 13:05 ` Oleg Nesterov
2012-08-02 13:20 ` Sebastian Andrzej Siewior
2012-08-02 13:24 ` Oleg Nesterov
2012-08-01 13:43 ` [PATCH 2/2] x86/uprobes: implement x86 specific arch_uprobe_*_step Oleg Nesterov
2012-08-02 4:58 ` Ananth N Mavinakayanahalli
2012-07-31 17:40 ` [PATCH 1/2] uprobes: Use a helper instead of ptrace's single step enable Oleg Nesterov
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