linux-kernel - Re: [BUG][SEVERE] Enabling EFI runtime services causes panics in the T2 security chip on Macs equipped with it.

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Date:   Tue, 11 Jan 2022 05:17:26 +0000
From:   Orlando Chamberlain <redecorating@...tonmail.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Aditya Garg <gargaditya08@...e.com>,
        "jk@...abs.org" <jk@...abs.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Aun-Ali Zaidi <admin@...eit.net>
Subject: Re: [BUG][SEVERE] Enabling EFI runtime services causes panics in the T2 security chip on Macs equipped with it.

On Tue, 11 Jan 2022 04:45:35 +1100
"Ard Biesheuvel" <ardb@...nel.org> wrote:

> On Mon, 10 Jan 2022 at 17:37, Ard Biesheuvel <ardb@...nel.org> wrote:
> >
> > On Mon, 10 Jan 2022 at 17:28, Aditya Garg <gargaditya08@...e.com>
> > wrote:  
> ...
> > > >>
> > > >> This seems to be triggered by EFI_QUERY_VARIABLE_INFO here
> > > >>  
> > > >
> > > > This is interesting. QueryVariableInfo() was introduced in EFI
> > > > 2.00, and for a very long time, Intel MACs would claim to
> > > > implement EFI 1.10 only. This means Linux would never attempt
> > > > to use QueryVariableInfo() on such platforms.
> > > >
> > > > Can you please check your boot log which revision it claims to
> > > > implement now?
> > > >
> > > > Mine says
> > > >
> > > > efi: EFI v1.10 by Apple  
> > >
> > > Mine says
> > >
> > > efi: EFI v2.40 by Apple
> > >  
> 
> Can you check whether things work as before after applying the change
> below?
> 
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 147c30a81f15..d7203355cc69 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -399,7 +399,7 @@ static int __init efi_systab_init(unsigned long
> phys) efi_nr_tables           = systab32->nr_tables;
>         }
> 
> -       efi.runtime_version = hdr->revision;
> +       efi.runtime_version = EFI_1_10_SYSTEM_TABLE_REVISION;
> 
>         efi_systab_report_header(hdr, efi_fw_vendor);
>         early_memunmap(p, size);

This patch works for me, I was able to use `efibootmgr -t 2` without
panics and the change to the boot timeout value persisted after a
reboot. (I don't think the Apple firmware would actually use this
timeout value for a timeout time, but it is an nvram vairable that i
was able to write to)

efi: EFI v2.40 by Apple
efi: ACPI=0x7affe000 ACPI 2.0=0x7affe014 SMBIOS=0x7aed0000 SMBIOS 3.0=0x7aece000 
SMBIOS 3.1.1 present.
DMI: Apple Inc. MacBookPro16,1/Mac-E1008331FDC96864, BIOS 1715.60.5.0.0 (iBridge: 19.16.10647.0.0,0) 11/16/2021

("iBridge" might be something to use for a quirk, as it should cover
all Macs with the T2 chip)


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