linux-kernel - Re: [PATCH] x86/microcode: allow non-root reading of microcode version and processor flags

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Message-Id: <CD5DA006-0D28-4CB9-95FA-231F0E20BF44@poczta.fm>
Date:   Sun, 26 Aug 2018 20:23:48 +0800
From:   Jacek Tomaka <jacek.tomaka@...zta.fm>
To:     Boris Petkov <bp@...en8.de>
Cc:     Jacek Tomaka <jacekt@...eo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/microcode: allow non-root reading of microcode version and processor flags


> On 26 Aug 2018, at 7:52 pm, Boris Petkov <bp@...en8.de> wrote:
> 
>> On August 25, 2018 6:50:39 AM GMT+03:00, Jacek Tomaka <jacekt@...eo.com> wrote:
>> /sys/devices/system/cpu/cpuX/microcode
>> 
>> Before:
>> -r-------- processor_flags
>> -r-------- version
>> 
>> After:
>> -r--r--r-- processor_flags
>> -r--r--r-- version
>> 
>> Microcode version has been already readable for non root users via
>> /proc/cpuinfo. However it is easier to access it from
>> /sys/devices/system/cpu/cpuX/microcode/version
> 
> Easier than /proc/cpuinfo?! Sorry, not really. 

Why not?

> You'd need to elaborate in greater detail what exactly you're trying to achieve.

I am trying to get microcode version from user space. Reading it from /proc/cpuinfo requires greping/awking to extract the bits of information that are readily available in microcode/version.

Any reason why the same piece of information has different access permissions, depending on the way it is accessed?

Regards.
Jacek Tomaka