linux-kernel - Re: [PATCH V6 6/8] Add EFI stub for ARM

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Date:	Tue, 14 Jan 2014 17:47:27 -0800
From:	Roy Franz <roy.franz@...aro.org>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Matt Fleming <matt.fleming@...el.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Patch Tracking <patches@...aro.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Mark Salter <msalter@...hat.com>,
	Grant Likely <grant.likely@...aro.org>,
	Dave Martin <dave.martin@....com>
Subject: Re: [PATCH V6 6/8] Add EFI stub for ARM

On Tue, Jan 14, 2014 at 1:05 AM, Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
> On 10 January 2014 17:30, Roy Franz <roy.franz@...aro.org> wrote:
>> This patch adds EFI stub support for the ARM Linux kernel.  The EFI stub
>> operates similarly to the x86 stub: it is a shim between the EFI firmware
>> and the normal zImage entry point, and sets up the environment that the
>> zImage is expecting.  This includes loading the initrd (optionaly) and
>> device tree from the system partition based on the kernel command line.
>> The stub updates the device tree as necessary, adding entries for EFI
>> runtime services. The PE/COFF "MZ" header at offset 0 results in the
>> first instruction being an add that corrupts r5, which is not used by
>> the zImage interface.
>>
>> Signed-off-by: Roy Franz <roy.franz@...aro.org>
>> Acked-by: Grant Likely <grant.likely@...aro.org>
>> ---
>
> [...]
>
>> diff --git a/arch/arm/boot/compressed/efi-header.S b/arch/arm/boot/compressed/efi-header.S
>> new file mode 100644
>> index 0000000..dbb7101
>> --- /dev/null
>> +++ b/arch/arm/boot/compressed/efi-header.S
>> @@ -0,0 +1,117 @@
>> +@ Copyright (C) 2013 Linaro Ltd;  <roy.franz@...aro.org>
>> +@
>> +@ This file contains the PE/COFF header that is part of the
>> +@ EFI stub.
>> +@
>> +
>> +       .org    0x3c
>> +       @
>> +       @ The PE header can be anywhere in the file, but for
>> +       @ simplicity we keep it together with the MSDOS header
>> +       @ The offset to the PE/COFF header needs to be at offset
>> +       @ 0x3C in the MSDOS header.
>> +       @ The only 2 fields of the MSDOS header that are used are this
>> +       @ PE/COFF offset, and the "MZ" bytes at offset 0x0.
>> +       @
>> +       .long   pe_header                       @ Offset to the PE header.
>> +
>> +      .align 3
>> +pe_header:
>> +       .ascii  "PE"
>> +       .short  0
>> +
>> +coff_header:
>> +       .short  0x01c2                          @ ARM or Thumb
>
> Could you explain why you are using 0x1c2 (Thumb) here and not 0x1c0 (ARM) ?
>
> Cheers,
> Ard.

Nope.  It should be 0x1c0.

Roy
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