linux-kernel - Re: [PATCH 5.4] arm64: kprobes: Use BRK instead of single-step when executing instructions out-of-line

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Date:   Mon, 20 Jun 2022 13:53:41 +0200
From:   Greg KH <greg@...ah.com>
To:     Mark-PK Tsai <mark-pk.tsai@...iatek.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        yj.chiang@...iatek.com,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        stable@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 5.4] arm64: kprobes: Use BRK instead of single-step when
 executing instructions out-of-line

On Wed, Jun 15, 2022 at 09:59:23AM +0800, Mark-PK Tsai wrote:
> From: Jean-Philippe Brucker <jean-philippe@...aro.org>
> 
> commit 7ee31a3aa8f490c6507bc4294df6b70bed1c593e upstream.
> 
> Commit 36dadef23fcc ("kprobes: Init kprobes in early_initcall") enabled
> using kprobes from early_initcall. Unfortunately at this point the
> hardware debug infrastructure is not operational. The OS lock may still
> be locked, and the hardware watchpoints may have unknown values when
> kprobe enables debug monitors to single-step instructions.
> 
> Rather than using hardware single-step, append a BRK instruction after
> the instruction to be executed out-of-line.
> 
> Fixes: 36dadef23fcc ("kprobes: Init kprobes in early_initcall")
> Suggested-by: Will Deacon <will@...nel.org>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
> Link: https://lore.kernel.org/r/20201103134900.337243-1-jean-philippe@linaro.org
> Signed-off-by: Will Deacon <will@...nel.org>
> Link: https://lore.kernel.org/lkml/20220610063619.7921-1-mark-pk.tsai@mediatek.com/
> Cc: stable@...r.kernel.org
> Signed-off-by: Mark-PK Tsai <mark-pk.tsai@...iatek.com>

Now queued up, thanks.

greg k-h