linux-kernel - Re: [PATCH v4 11/39] x86/mm: Update pte_modify for _PAGE

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Message-ID: <Y7V+ZbTa3bWmXzKo@zn.tnic>
Date:   Wed, 4 Jan 2023 14:25:57 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v4 11/39] x86/mm: Update pte_modify for _PAGE_COW

On Tue, Dec 27, 2022 at 11:31:37PM +0000, Edgecombe, Rick P wrote:
> The comment is referring to the dirty bits possibly coming from
> newprot,

Ah right, ofc.

> but looking at it now I think the code was broken trying to
> fix the recent soft dirty test breakage. Now it might lose pre-existing
> dirty bits in the pte unessarily... I think.

Right, does this code need to be simplified?

I.e., match the shadow stack PTE (Write=0,Dirty=1) and handle that in a separate
helper?

So that the flows are separate. I'm not a mm guy but this function makes my head
hurt - dunno about other folks. :)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette