linux-hardening - Re: [PATCH 00/16] x86_64: Improvements at compressed kernel stage

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Date:   Tue, 18 Oct 2022 17:04:47 -0400
From:   Peter Jones <pjones@...hat.com>
To:     Evgeniy Baskov <baskov@...ras.ru>
Cc:     Ard Biesheuvel <ardb@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org, x86@...nel.org,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 00/16] x86_64: Improvements at compressed kernel stage

On Tue, Sep 06, 2022 at 01:41:04PM +0300, Evgeniy Baskov wrote:
> This patchset is aimed
> * to improve UEFI compatibility of compressed kernel code for x86_64
> * to setup proper memory access attributes for code and rodata sections
> * to implement W^X protection policy throughout the whole execution 
>   of compressed kernel for EFISTUB code path. 

Hi Evgeniy,

I've tested this set of patches with the Mu firmware that supports the W^X
feature and a modified bootloader to also support it, and also with an
existing firmware and the grub2 build in fedora 36.  On the firmware
without W^X support, this all works for me.  With W^X support, it works
so long as I use CONFIG_EFI_STUB_EXTRACT_DIRECT, though I still need
some changes in grub's loader.  IMO that's a big step forward.

I can't currently make it work with W^X enabled but without direct
extraction, and I'm still investigating why not, but I figured I'd give
you a heads up.

-- 
        Peter