From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 87DD419342B; Mon, 30 Sep 2024 17:13:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727716412; cv=none; b=YYkMrxTC+fLzX8KSOBQw2BVC1iHzdQx3H7zLwqTCEXE1zCO70Go/sAaets1hMCJxB89OG7K6PiYeuYuRJphApQip8/dpNOfMIj8ARRGN1PYBOVatuYaoPcfs6CVVAISHjO6Cnr5/Q0W65zstgG9EQdcq3mSomO7zrjKi/+Hhs/w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727716412; c=relaxed/simple; bh=Eew9bXlDuPZUSAxAdTkv17Hsuq5cqSvBcNnD9EMG2lE=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=tSqFUHsjXSpdBqzq+55VkPxZHGpsoOemAlPJZa2BNBpYeo2IWhAcHlW7mPgApEOW35XixgC43cL1UqCe25eLDF3TakbFwDOP9b+FU1jtsu09sDHxI9ZfLIL/rJB6bPMoFl1vfua2npvnIy4wUoBtBu2g8smsTIUBRwJtx3XmPm0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5F91C4CECE; Mon, 30 Sep 2024 17:13:28 +0000 (UTC) Date: Mon, 30 Sep 2024 13:14:15 -0400 From: Steven Rostedt To: Jonathan Corbet Cc: Hans de Goede , LKML , Linux trace kernel , Masami Hiramatsu , Mathieu Desnoyers , Mike Rapoport , Kees Cook , Ard Biesheuvel , linux-doc@vger.kernel.org Subject: Re: [PATCH] Documentation/tracing: Mention that RESET_ATTACK_MITIGATION can clear memory Message-ID: <20240930131415.1438c0b7@gandalf.local.home> In-Reply-To: References: <20240926130159.19e6d0e2@rorschach.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 26 Sep 2024 19:54:48 +0200 Hans de Goede wrote: > Hi, > > On 26-Sep-24 7:01 PM, Steven Rostedt wrote: > > From: Steven Rostedt > > > > At the 2024 Linux Plumbers Conference, I was talking with Hans de Goede > > about the persistent buffer to display traces from previous boots. He > > mentioned that UEFI can clear memory. In my own tests I have not seen > > this. He later informed me that it requires the config option: > > > > CONFIG_RESET_ATTACK_MITIGATION > > > > It appears that setting this will allow the memory to be cleared on boot > > up, which will definitely clear out the trace of the previous boot. > > > > Add this information under the trace_instance in kernel-parameters.txt > > to let people know that this can cause issues. > > > > Link: https://lore.kernel.org/all/20170825155019.6740-2-ard.biesheuvel@linaro.org/ > > > > Reported-by: Hans de Goede > > Signed-off-by: Steven Rostedt (Google) > > Thanks, patch looks good to me: > > Reviewed-by: Hans de Goede Thanks, And I forgot to send this to the Documentation maintainers :-p Jon, could you take this? Do you need me to resend, or can you just pull it from lore? https://lore.kernel.org/linux-trace-kernel/20240926130159.19e6d0e2@rorschach.local.home/ -- Steve > > Regards, > > Hans > > > > > --- > > Documentation/admin-guide/kernel-parameters.txt | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index bb48ae24ae69..f9b79294f84a 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -6850,6 +6850,9 @@ > > > > reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq > > > > + Note, CONFIG_RESET_ATTACK_MITIGATION can force a memory reset on boot which > > + will clear any trace that was stored. > > + > > See also Documentation/trace/debugging.rst > > > >