linux-kernel - Re: [RFC PATCH 0/2] arm64 kgdb fixes for single stepping

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Message-ID: <20200213101057.GB1405@willie-the-truck>
Date:   Thu, 13 Feb 2020 10:10:58 +0000
From:   Will Deacon <will@...nel.org>
To:     minyard@....org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] arm64 kgdb fixes for single stepping

On Wed, Feb 12, 2020 at 09:11:29PM -0600, minyard@....org wrote:
> I got a bug report about using kgdb on arm64, and it turns out it was
> fairly broken.  Patch 2 has a description of what was going on.  I am
> using a Marvell 8100 board.
> 
> The following patches fix the problem, but probably not in the
> best way.  They are what I hacked out to show the problems.
> 
> I am not quite sure how this will interact with kprobes and hardware
> breakpoints which use the same code, but they would have been broken,
> too, so this is not making them any worse.

This should all be handled by kgdb itself, not by changing the low-level
debug exception handling. For example, the '&kgdb_step_hook' can take
care of re-arming the step state machine and kgdb can also simply disable
interrupts during the step if it doesn't want to step into the handler.

Will