linux-kernel - Re: [PATCH] coresight: etm3x: Fix buffer overwrite in cntr_val

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Message-ID: <20251127092942.GO724103@e132581.arm.com>
Date: Thu, 27 Nov 2025 09:29:42 +0000
From: Leo Yan <leo.yan@....com>
To: Mike Leach <mike.leach@...aro.org>
Cc: James Clark <james.clark@...aro.org>,
	Kuan-Wei Chiu <visitorckw@...il.com>, suzuki.poulose@....com,
	alexander.shishkin@...ux.intel.com, pratikp@...eaurora.org,
	mathieu.poirier@...aro.org, gregkh@...uxfoundation.org,
	jserv@...s.ncku.edu.tw, marscheng@...gle.com, ericchancf@...gle.com,
	milesjiang@...gle.com, nickpan@...gle.com,
	coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: etm3x: Fix buffer overwrite in cntr_val_show()

On Wed, Nov 26, 2025 at 04:14:19PM +0000, Mike Leach wrote:

[...]

> > > The key to this is not the questions we are asked, but which platforms
> > > are still supported by the linux kernel.
> > >
> > > The ETMv3 driver supports both ETMv3 and PTM trace (the programming
> > > model is the same, even if the trace decode is vastly different).
> > >
> > > So as long as there are  platforms supported that use either of those,
> > > we need to keep the driver in.
> > >
> >
> > We're not running tests though, so if we find out it's fundamentally
> > broken somehow it could be another justification to remove it, even if
> > the kernel supports the devices. Do you have a board that you can test
> > on Mike?
> 
> Don't have one myself, but I believe the TC2 was used in development,
> (that's the A15/A7 32 bit part - not total compute!) which somewhat
> conveniently had both etmv3 and ptm trace.

If ETMv4 can be used by Armv7 (arm32) CPUs, and nowdays if Armv7 + ETMv4
is a popular design, it makes sense for me to remove ETMv3 driver.

If Armv7 CPUs are always bound to ETMv3 / PTM, then we should keep the
driver.

Thanks,
Leo