From: Oleg Nesterov <oleg@redhat.com>
To: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "Suzuki K. Poulose" <suzuki@in.ibm.com>,
bigeasy@linutronix.de, srikar@linux.vnet.ibm.com,
peterz@infradead.org, benh@kernel.crashing.org, mingo@elte.hu,
anton@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 4/4] uprobes/powerpc: Make use of generic routines to enable single step
Date: Tue, 18 Dec 2012 20:10:13 +0100 [thread overview]
Message-ID: <20121218191013.GA26913@redhat.com> (raw)
In-Reply-To: <20121218053603.GB6116@in.ibm.com>
On 12/18, Ananth N Mavinakayanahalli wrote:
>
> On Fri, Dec 14, 2012 at 09:02:41PM +0100, Oleg Nesterov wrote:
> > >
> > > - uprobe_restore_context_sstep(&utask->autask);
> > > + uprobe_restore_context_sstep(&utask->autask, regs);
> >
> > I am not sure ppc needs this, but note that x86 does a bit more.
> >
> > Not only we need to restore the "single-step" state, we need to
> > send SIGTRAP if it was not set by us. The same for _skip_sstep.
>
> Do you mean restoring the TF equivalent on powerpc to what it was before?
>
> If so, powerpc has always been unique in this aspect -- the single-step
> exception handler *always* resets the sstep bit in MSR. Any user needing
> to continue single-stepping has to explicitly set it again.
I meant another thing.
Suppose that, say, gdb tries to single-step over the probed insn.
In this case we need to send SIGTRAP after xol/emulate. Please look at
send_sig(SIGTRAP) in arch/x86/kernel/uprobes.c:arch_uprobe_post_xol()
and arch_uprobe_skip_sstep().
Oleg.
next prev parent reply other threads:[~2012-12-18 19:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-03 15:07 [PATCH v2 0/4] uprobes/powerpc: Replace ptrace helpers for single stepping Suzuki K. Poulose
2012-12-03 15:07 ` [PATCH v2 1/4] kprobes/powerpc: Do not disable External interrupts during single step Suzuki K. Poulose
2012-12-11 5:48 ` Suzuki K. Poulose
2013-01-04 4:42 ` Benjamin Herrenschmidt
2013-01-07 12:03 ` Sebastian Andrzej Siewior
2012-12-03 15:08 ` [PATCH v2 2/4] powerpc: Move the single step enable code to a generic path Suzuki K. Poulose
2012-12-10 10:34 ` Ananth N Mavinakayanahalli
2012-12-03 15:09 ` [PATCH v2 3/4] uprobes/powerpc: Introduce routines for save/restore context Suzuki K. Poulose
2012-12-03 15:15 ` Ananth N Mavinakayanahalli
2012-12-03 15:48 ` Suzuki K. Poulose
2012-12-10 10:35 ` Ananth N Mavinakayanahalli
2012-12-03 15:10 ` [PATCH v2 4/4] uprobes/powerpc: Make use of generic routines to enable single step Suzuki K. Poulose
2012-12-10 10:35 ` Ananth N Mavinakayanahalli
2012-12-14 20:02 ` Oleg Nesterov
2012-12-18 5:11 ` Suzuki K. Poulose
2012-12-18 5:36 ` Ananth N Mavinakayanahalli
2012-12-18 19:10 ` Oleg Nesterov [this message]
2012-12-19 4:53 ` Ananth N Mavinakayanahalli
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