linux-kernel - Re: [PATCH 1/4] coresight/etm4x: disallow altering config via sysfs while enabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4f9d2bed-7ce0-429e-83cc-ad6cbcc6085e@arm.com>
Date: Thu, 9 Jan 2025 12:21:11 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: mike.leach@...aro.org, james.clark@...aro.org,
 alexander.shishkin@...ux.intel.com, coresight@...ts.linaro.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] coresight/etm4x: disallow altering config via sysfs
 while enabled

On 09/01/2025 12:01, Yeoreum Yun wrote:
> Hi Suzuki,
> 
>> Is it not better to have separate "configs" for perf and sysfs ?
>> And etmX driver can populate the "running" config, based on the
>> mode specific config. That way, the configs can be updated
>> independently without affecting the running config or the perf one.
>>
> 
> That was i've tried but I've accepted Mike's opinion that
> it's enough to check whether CS_MODE_DISABLED via coresight_get_mode()
> in *_store().
> 
> "the .._store functions in sysfs should use coresight_get_mode() to ensure
> this is set to CS_MODE_DISABLED before altering the config,
> which ensures that the trace system is inactive.
> We don't' really care about reading the config if trace is running."

There are two issues with that :

1. Sprinkling the get_mode call in each sysfs stor function doesn't look 
good to me.

2. Someone preparing for a sysfs session must not be prevented from 
doing so just because there is a perf session running.


Suzuki


> Thanks.
>