linux-kernel - Re: [PATCH v2] x86: Preserve iopl on fork and execve

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Date:	Tue, 12 May 2015 12:05:45 -0600
From:	Alex Henrie <alexhenrie24@...il.com>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>
Cc:	Arjan van de Ven <arjanvandeven@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Kees Cook <keescook@...omium.org>,
	"H . Peter Anvin" <hpa@...or.com>, Doug Johnson <dougvj@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Tyler Hicks <tyhicks@...onical.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arjan van de Ven <arjan@...radead.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH v2] x86: Preserve iopl on fork and execve

2015-05-12 9:47 GMT-06:00 Austin S Hemmelgarn <ahferroin7@...il.com>:
> On 2015-05-12 11:25, Arjan van de Ven wrote:
>> If you look at a modern linux distro, nothing should need/use iopl and
>> co anymore, so maybe an interesting
>> question is if we can stick these behind a CONFIG_ option (default on
>> of course for compatibility)... just like
>> some of the /dev/mem like things are now hidable for folks who know
>> they don't need them.
>
> Personally, I _really_ like this idea.  The only thing I know of on any
> modern distro that even considers using ioperm is hwclock, and it only does
> so if it can't access the RTC through other means (and if you have an RTC,
> you really should have the /dev interface enabled).

Removing iopl might be OK. Removing ioperm would break my use case of
legacy code that needs direct access to the parallel port.

-Alex
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