linux-kernel - Re: [PATCH v2 00/23] x86_64: Improvements at compressed kernel stage

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Message-ID: <4a942ab07fd320ba9a058c8a112503bd@ispras.ru>
Date:   Wed, 09 Nov 2022 02:49:08 +0300
From:   Evgeniy Baskov <baskov@...ras.ru>
To:     "Limonciello, Mario" <mario.limonciello@....com>
Cc:     Ard Biesheuvel <ardb@...nel.org>, 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>,
        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 v2 00/23] x86_64: Improvements at compressed kernel stage

On 2022-11-08 21:17, Limonciello, Mario wrote:
> On 11/8/2022 01:01, Evgeniy Baskov wrote:
>> On 2022-11-04 21:21, Limonciello, Mario wrote:
>>> On 10/25/2022 09:12, Evgeniy Baskov wrote:
>>>> ...
>>>> 
>>> 
>>> Hi,
>>> 
>>> I was talking to Peter Jones recently about what was still missing 
>>> for
>>> NX support in the kernel and he pointed me at this series.
>>> 
>>> So I had a try with this series on top of:
>>> 
>>> ee6050c8af96 ("Merge tag 'ata-6.1-rc4' of
>>> git://git.kernel.org/pub/scm/linux/kernel/git/dlemoal/libata")
>>> 
>>> Unfortunately I can't boot the system with this series applied.
>>> This is not on a system that enforces NX pre-boot (but that was my
>>> goal after I could prove booting on something that doesn't).
>>> I didn't apply Peter's patch 6 you referenced in your cover letter,
>>> but I don't expect that's the reason for the failure.
>>> 
>>> I get:
>>> 
>>> "Failed to allocate space for tmp_cmdline"
>>> 
>>>    -- System Halted
>>> 
>>> This is early enough [1] that I don't have anything else output to a
>>> serial log from the kernel.
>>> 
>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Ftorvalds%2Flinux%2Fblob%2Fd4013bc4d49f6da8178a340348369bb9920225c9%2Farch%2Fx86%2Fboot%2Fcompressed%2Fkaslr.c%23L268&amp;data=05%7C01%7Cmario.limonciello%40amd.com%7C9280e92e85bc4e2b52cd08dac15704a5%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638034876740462327%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=oiCJUa8M3x%2FYCxVjJj98R7iU%2FzIj%2FQxdVOWbnqGWCNI%3D&amp;reserved=0
>>> 
>>> Since this is only in the kaslr path, I tried to turn that off with
>>> 'nokaslr' on the kernel command line.
>>> 
>>> I then get a failure of:
>>> 
>>> "Out of memory while allocating zstd_dctx"
>>> 
>>>   -- System Halted
>>> 
>>> This kernel was booted from the following path:
>>> -> Insyde BIOS
>>> --> shim (from Fedora 36 repository)
>>> ---> GRUB (from Peter for Fedora 36 w/ some level NX support)
>>> ----> kernel binary (self-built)
>>> 
>>> The BIOS on this system doesn't validate NX, but also the shim binary
>>> did not have the NX bit set in the PE header.
>>> 
>>> Your cover letter referenced CONFIG_EFI_STUB_EXTRACT_DIRECT but I
>>> didn't find this option in the series.  I also tried both with
>>> CONFIG_EFI_DXE_MEM_ATTRIBUTES=y or unset, same result.
>> 
>> Hi,
>> 
>> Thanks for your feedback!
>> 
> 
> Sure!
> 
>> CONFIG_EFI_STUB_EXTRACT_DIRECT option was removed in v2 of the series
>> and direct extraction is unconditional now.
>> 
>> You are getting really weird errors, which unfortunately I am unable
>> to reproduce yet. I've tried booting with fedora's grub and the series
>> applied on top of ee6050c8af96, but it did boot successfully.
> 
> Well so I expect the unique difference is that I'm using Peter's GRUB
> that has some NX support landed.  He has binaries for it here:
> 
> https://blog.uncooperative.org/~pjones/nx/repo/
> 
> *Theoretically* a BIOS that enforces NX should be able to boot a shim 
> with
> the NX compat bit set which should be able to boot that GRUB
> supporting NX which should be able to boot this series.
> 
>> 
>>  From the error messages it's some problem with malloc() 
>> implementation
>> of compressed kernel code. I suspect that malloc_ptr inside .bss is 
>> not
>> zeroed. This should not happen when booting via either non-UEFI
>> interface, or via UEFI (when kernel is properly loaded as PE image).
>> The problem, I think, arises when kernel is loaded as a blob, but EFI
>> handover protocol is used to start its execution. This is what grub
>> seems to be doing.
>> 
>> Can you please try booting with patches below applied on top?
>> If this fixes the problem, I'll include these changes in v3.
> 
> Yup, spot on.  I can the kernel from Peter's NX enabled GRUB now with:
> * 6.1-rc4
> * Your existing 23 patch series
> * this new patch
> 



> Thanks!!
> 
> Would you mind CC me when you submit v3?  As I have an interest in
> seeing NX support I'd like to continue to follow along on the series.

Ok.
> 
> Anything in the series you don't change in any material way from v2
> please feel free to include:
> 
> Tested-by: Mario Limonciello <mario.limonciello@....com>
> 

Great, thanks!