linux-kernel - Re: pgprot_encrypted macro is broken

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Message-ID: <CAMZm_CmW7pHwfEfCQfXRJPiHOjeGviQunfwxY_1ejrihKab5rA@mail.gmail.com>
Date:   Mon, 20 Jun 2022 09:39:09 +0200
From:   Federico Di Pierro <nierro92@...il.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>, x86@...nel.org
Subject: Re: pgprot_encrypted macro is broken

> Why does your driver need to use that macro? pgprot_encrypted() is
> mostly only directly used by core kernel code, not by drivers... and
> if memory encryption is enabled, almost all memory mappings created by
> the kernel should be marked as encrypted automatically.

This is interesting; i don't really know the history behind our piece
of code; as far as i understand,
we have a shared ring buffer with userspace, onto which we push tracing events,
and we must mark it as encrypted when
the kmod runs on an AMD SME enabled kernel to allow userspace to grab sane data.

This is the commit that introduced the change (if you wish to give it a look):
https://github.com/falcosecurity/libs/commit/0333501cf429c045c61aaf5909812156f090786e

Do you see any workaround not involving `pgprot_encrypted` ?

Thank you very much for your answer, much appreciated!
Regards,
Federico