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From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: catalin.marinas@arm.com, Will Deacon <will@kernel.org>,
	dianders@chromium.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: Fix early single-stepping
Date: Wed, 28 Oct 2020 10:48:27 +0100	[thread overview]
Message-ID: <20201028094827.GC2328726@myrica> (raw)
In-Reply-To: <20201028180731.13d770167b521dc28c189bbb@kernel.org>

On Wed, Oct 28, 2020 at 06:07:31PM +0900, Masami Hiramatsu wrote:
> > > Yes, I think so. Same order problem as the OS lock, they need to be reset
> > > before enable_debug_monitors(). On CPU0 that would be before
> > > early_initcall and for secondaries the hotplug notifier needs to be
> > > installed earlier as well. I'll send a v2.
> > 
> > Cheers. An alternative (which I think would be better in the long run
> > anyway) would be to avoid using hardware step in kprobes and instead rely
> > on a BRK instruction to trap after running the trampoline.
> 
> But how we trap the instruction which can change pc? (like br?)
> Are all those instruction emulated now?

According to aarch64_insn_is_steppable() anything that changes the PC is
emulated. I'm also checking whether there is a change of behavior with
synchronous exceptions taken while single-stepping (page faults).

Thanks,
Jean

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  reply	other threads:[~2020-10-28  9:49 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-26 17:29 [PATCH] arm64: Fix early single-stepping Jean-Philippe Brucker
2020-10-26 17:38 ` Will Deacon
2020-10-27  0:48   ` Masami Hiramatsu
2020-10-27 10:13 ` Masami Hiramatsu
2020-10-27 10:42   ` Masami Hiramatsu
2020-10-27 11:59     ` Jean-Philippe Brucker
2020-10-27 12:33       ` Will Deacon
2020-10-27 13:49         ` Masami Hiramatsu
2020-10-28  8:28           ` Jean-Philippe Brucker
2020-10-28  8:36             ` Will Deacon
2020-10-28  9:07               ` Masami Hiramatsu
2020-10-28  9:48                 ` Jean-Philippe Brucker [this message]
2020-10-28 12:21                   ` Masami Hiramatsu
2020-11-25 16:09               ` Masami Hiramatsu
2020-11-25 16:11                 ` Will Deacon
2020-11-25 16:18                   ` Masami Hiramatsu

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