linux-kernel - Re: [PATCH V5 1/6] efi-stub.txt updates for ARM

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Date:	Thu, 05 Dec 2013 15:19:23 +0000
From:	Grant Likely <grant.likely@...aro.org>
To:	Roy Franz <roy.franz@...aro.org>, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	matt.fleming@...el.com, linux@....linux.org.uk
Cc:	leif.lindholm@...aro.org, dave.martin@....com, msalter@...hat.com,
	patches@...aro.org, Roy Franz <roy.franz@...aro.org>
Subject: Re: [PATCH V5 1/6] efi-stub.txt updates for ARM

On Wed, 27 Nov 2013 15:31:50 -0800, Roy Franz <roy.franz@...aro.org> wrote:
> Update efi-stub.txt documentation to be more general
> and not x86 specific.  Add ARM only "dtb=" command
> line option description.
> 
> Signed-off-by: Roy Franz <roy.franz@...aro.org>

Acked-by: Grant Likely <grant.likely@...aro.org>

> ---
>  Documentation/efi-stub.txt |   27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/efi-stub.txt b/Documentation/efi-stub.txt
> index 44e6bb6..19e897c 100644
> --- a/Documentation/efi-stub.txt
> +++ b/Documentation/efi-stub.txt
> @@ -1,13 +1,16 @@
>  			  The EFI Boot Stub
>  		     ---------------------------
>  
> -On the x86 platform, a bzImage can masquerade as a PE/COFF image,
> -thereby convincing EFI firmware loaders to load it as an EFI
> -executable. The code that modifies the bzImage header, along with the
> -EFI-specific entry point that the firmware loader jumps to are
> -collectively known as the "EFI boot stub", and live in
> +On the x86 and ARM platforms, a kernel zImage/bzImage can masquerade
> +as a PE/COFF image, thereby convincing EFI firmware loaders to load
> +it as an EFI executable. The code that modifies the bzImage header,
> +along with the EFI-specific entry point that the firmware loader
> +jumps to are collectively known as the "EFI boot stub", and live in
>  arch/x86/boot/header.S and arch/x86/boot/compressed/eboot.c,
> -respectively.
> +respectively.  For ARM the EFI stub is implemented in
> +arch/arm/boot/compressed/efi-header.S and
> +arch/arm/boot/compressed/efi-stub.c.  EFI stub code that is shared
> +between architectures is in drivers/firmware/efi/efi-stub-helper.c.
>  
>  By using the EFI boot stub it's possible to boot a Linux kernel
>  without the use of a conventional EFI boot loader, such as grub or
> @@ -23,7 +26,9 @@ The bzImage located in arch/x86/boot/bzImage must be copied to the EFI
>  System Partiion (ESP) and renamed with the extension ".efi". Without
>  the extension the EFI firmware loader will refuse to execute it. It's
>  not possible to execute bzImage.efi from the usual Linux file systems
> -because EFI firmware doesn't have support for them.
> +because EFI firmware doesn't have support for them.  For ARM the
> +arch/arm/boot/zImage should be copied to the system partition, and it
> +may not need to be renamed.
>  
>  
>  **** Passing kernel parameters from the EFI shell
> @@ -63,3 +68,11 @@ Notice how bzImage.efi can be specified with a relative path. That's
>  because the image we're executing is interpreted by the EFI shell,
>  which understands relative paths, whereas the rest of the command line
>  is passed to bzImage.efi.
> +
> +
> +**** The "dtb=" option
> +
> +For the ARM architecture, we also need to be able to provide a device
> +tree to the kernel.  This is done with the "dtb=" command line option,
> +and is process in the same manner as the "initrd=" option that is described
> +above.
> -- 
> 1.7.10.4
> 

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