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From: Peter Zijlstra <peterz@infradead.org>
To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Mike Leach <mike.leach@linaro.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Leo Yan <leo.yan@linaro.org>,
	coresight@lists.linaro.org, Stephen Boyd <swboyd@chromium.org>,
	Denis Nikitin <denik@chromium.org>,
	Mattias Nissler <mnissler@chromium.org>,
	Al Grant <al.grant@arm.com>,
	linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/4] perf/core: Add support to exclude kernel mode instruction tracing
Date: Fri, 29 Jan 2021 20:30:40 +0100	[thread overview]
Message-ID: <20210129193040.GJ8912@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <89c7ff59d887a0360434e607bd625393ec3190e5.1611909025.git.saiprakash.ranjan@codeaurora.org>

On Sat, Jan 30, 2021 at 12:35:10AM +0530, Sai Prakash Ranjan wrote:

> Here the idea is to protect such important information from all users
> including root users since root privileges does not have to mean full
> control over the kernel [1] and root compromise does not have to be
> the end of the world.

And yet, your thing lacks:

> +config EXCLUDE_KERNEL_HW_ITRACE
> +	bool "Exclude kernel mode hardware assisted instruction tracing"
> +	depends on PERF_EVENTS
	depends on SECURITY_LOCKDOWN

or whatever the appropriate symbol is.

> +	help
> +	  Exclude kernel mode instruction tracing by hardware tracing
> +	  family such as ARM Coresight ETM, Intel PT and so on.
> +
> +	  This option allows to disable kernel mode instruction tracing
> +	  offered by hardware assisted tracing for all users(including root)
> +	  especially for production systems where only userspace tracing might
> +	  be preferred for security reasons.

Also, colour me unconvinced, pretty much all kernel level PMU usage
can be employed to side-channel / infer crypto keys, why focus on
ITRACE over others?

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc: Mark Rutland <mark.rutland@arm.com>, Al Grant <al.grant@arm.com>,
	Denis Nikitin <denik@chromium.org>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org,
	Mattias Nissler <mnissler@chromium.org>,
	linux-kernel@vger.kernel.org,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Stephen Boyd <swboyd@chromium.org>,
	Ingo Molnar <mingo@redhat.com>, Leo Yan <leo.yan@linaro.org>,
	Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
	linux-arm-kernel@lists.infradead.org,
	Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCH 1/4] perf/core: Add support to exclude kernel mode instruction tracing
Date: Fri, 29 Jan 2021 20:30:40 +0100	[thread overview]
Message-ID: <20210129193040.GJ8912@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <89c7ff59d887a0360434e607bd625393ec3190e5.1611909025.git.saiprakash.ranjan@codeaurora.org>

On Sat, Jan 30, 2021 at 12:35:10AM +0530, Sai Prakash Ranjan wrote:

> Here the idea is to protect such important information from all users
> including root users since root privileges does not have to mean full
> control over the kernel [1] and root compromise does not have to be
> the end of the world.

And yet, your thing lacks:

> +config EXCLUDE_KERNEL_HW_ITRACE
> +	bool "Exclude kernel mode hardware assisted instruction tracing"
> +	depends on PERF_EVENTS
	depends on SECURITY_LOCKDOWN

or whatever the appropriate symbol is.

> +	help
> +	  Exclude kernel mode instruction tracing by hardware tracing
> +	  family such as ARM Coresight ETM, Intel PT and so on.
> +
> +	  This option allows to disable kernel mode instruction tracing
> +	  offered by hardware assisted tracing for all users(including root)
> +	  especially for production systems where only userspace tracing might
> +	  be preferred for security reasons.

Also, colour me unconvinced, pretty much all kernel level PMU usage
can be employed to side-channel / infer crypto keys, why focus on
ITRACE over others?

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-01-29 19:32 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-29 19:05 [PATCH 0/4] Add support to exclude kernel mode hardware assisted instruction tracing Sai Prakash Ranjan
2021-01-29 19:05 ` [PATCH 1/4] perf/core: Add support to exclude kernel mode " Sai Prakash Ranjan
2021-01-29 19:30   ` Peter Zijlstra [this message]
2021-01-29 19:30     ` Peter Zijlstra
2021-02-01  7:41     ` Sai Prakash Ranjan
2021-02-01 13:41       ` Peter Zijlstra
2021-02-01 13:41         ` Peter Zijlstra
2021-02-02  6:11         ` Sai Prakash Ranjan
2021-02-10  7:38           ` Sai Prakash Ranjan
2021-01-29 19:05 ` [PATCH 2/4] perf evsel: Print warning for excluding " Sai Prakash Ranjan
2021-01-29 19:05 ` [PATCH 3/4] coresight: etm4x: Add support to exclude kernel mode tracing Sai Prakash Ranjan
2021-02-22 20:14   ` Doug Anderson
2021-02-22 20:14     ` Doug Anderson
2021-02-24 14:51     ` Sai Prakash Ranjan
2021-01-29 19:05 ` [PATCH 4/4] coresight: etm3x: " Sai Prakash Ranjan

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