linux-kernel - Re: [PATCH v3 00/24] x86_64: Improvements at compressed kernel stage

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Message-ID: <CAMj1kXEVffE8nm5qP_tGzQ9zGaXP11RtdFQhhwQc_DDyAk6qOw@mail.gmail.com>
Date:   Wed, 14 Dec 2022 11:09:32 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Evgeniy Baskov <baskov@...ras.ru>
Cc:     Peter Jones <pjones@...hat.com>, 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>,
        "Limonciello, Mario" <mario.limonciello@....com>,
        joeyli <jlee@...e.com>, 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 v3 00/24] x86_64: Improvements at compressed kernel stage

On Tue, 13 Dec 2022 at 23:16, Evgeniy Baskov <baskov@...ras.ru> wrote:
>
> On 2022-12-13 21:13, Peter Jones wrote:
> > On Tue, Dec 13, 2022 at 01:03:17PM -0500, Peter Jones wrote:
> >> On Tue, Nov 22, 2022 at 02:12:09PM +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 patch set on hardware and QEMU+MU firmware, and it
> >> works for me with a couple of minor issues:
> >>
> >> - on one machine that has the DXE protocol but not the EFI one, we get
> >>   an error because the firmware doesn't support EFI_MEMORY_RP
> >> - on QEMU I'm seeing the size of "(unsigned long)_head - image_base"
> >>   wind up as 0, which leads to an EFI_INVALID_PARAMETER on the
> >>   clear_memory_attributes() call.
> >>
> >> In both cases the system winds up working, but with unnecessary
> >> console
> >> output.
> >
> > I just realized I've overstated here - I haven't actually hit the first
> > problem on x86, only on ARM, where we don't currently use this code.  I
> > discovered it in grub, and checked your patch set to see if you had the
> > same issue I did.  That said, "in both cases the system winds up
> > working" is probably still true - in that the edk2 code supports
> > EFI_MEMORY_RP on x86 but not ARM, so x86 won't hit the issue when using
> > DXE unless someone cooks up another implementation.  Nevertheless I
> > believe the patch to fix it is correct and should be applied.
> >
> > Thanks!
>
> Hi,
>
> Thank you for testing and fixes!
>
> I have also discovered one issue with v3, that can only be hit when
> booting with grub -- there's one kernel_add_identity_map() missing in
> the get_acpi_srat_table() function, before header->length is read.
> So I'll prepare the v4 soon and include your new patches there.
>

Happy to see this is converging. Please rebase onto latest mainline as
well - some cleanups to the early boot code have landed there
yesterday.