linux-kernel - Re: [PATCH] Fix triplefault on x86-64 bootup

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Message-Id: <200708121201.48383.ak@suse.de>
Date:	Sun, 12 Aug 2007 12:01:48 +0200
From:	Andi Kleen <ak@...e.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Petr Vandrovec <petr@...drovec.name>, discuss@...-64.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix triplefault on x86-64 bootup

On Sunday 12 August 2007 10:59, Linus Torvalds wrote:
> On Sun, 12 Aug 2007, Linus Torvalds wrote:
> > Hmm. Patch looks ok, I just wonder what started triggering this for you?
>
> Oh. It's the "Make patching more robust" commit.

No it should have been the earlier text_poke change which first
started using mempcy in that path.

> "Robust" my ass.
>
> We used to just copy the replacement in one go (works fine, since it just
> overwrote the two first bytes), and then "nop_out()" the rest (works fine,
> since it didn't matter for memcpy).
>
> That whole commit looks a bit dubious. It also adds a 254-byte stack
> usage (anything actually even close to that big?). Gaah.

The x86-64 copy_user copies the whole function as alternative
and it is over 200 bytes.
The original patch had a smaller buffer and cause x86-64 to BUG
at boot

-Andi


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