linux-kernel - Re: [PATCH] Add a text

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Message-ID: <87mwkzvvck.fsf@tassilo.jf.intel.com>
Date:	Wed, 20 Nov 2013 09:25:31 -0800
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Add a text_poke syscall

"H. Peter Anvin" <hpa@...or.com> writes:
>
> We're talking user space here, which has different requirement (COW,
> memory protection, ...) which means it is not really the same code.  You
> can't take a page fault while patching the kernel.

The syscall pins the page, then it calls the kernel code.
There are no page faults during patching.

> I'm referring to if some thread actually stumbles over INT 3, which is
> indeed not very long for one patch site (as long as you don't end up
> with page faults.)  However, for tracing, you may want to do tens of
> thousands of patches, and you really want to batch them.

For tens of thousand of patches you very likely don't want 
live patching, but a stop everything approach.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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