Subject: EFI_STUB fails to boot non-EFI on arm64

From: [email-masked] (Catalin Marinas)
Date: Fri, 23 May 2014 14:47:20 +0100

On Fri, May 23, 2014 at 02:16:56PM +0100, Leif Lindholm wrote:
> Subject: [PATCH] arm64: efi: only attempt efi map setup if booting via EFI
> 
> Booting a kernel with CONFIG_EFI enabled on a non-EFI system caused
> an oops with the current UEFI support code.
> Add the required test to prevent this.
> 
> Signed-off-by: Leif Lindholm <[email-masked]>
> ---
>  arch/arm64/kernel/efi.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index 7bfd650..14db1f6 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -333,6 +333,9 @@ void __init efi_init(void)
>  
>  void __init efi_idmap_init(void)
>  {
> +	if (!efi_enabled(EFI_BOOT))
> +		return;
> +

That's a first (possibly temporary) step and I think it's fine:

Acked-by: Catalin Marinas <[email-masked]>

But we need some further tweaking to the way we call efi_init().
Currently it doesn't matter whether Linux booted as an EFI application
or not and efi_init() is always called, causing some pr_err() in
fdt_find_uefi_params(). It's not really an error as we support the same
image booting non-EFI as well.

Can we add another of detecting whether it's an EFI application and
avoid calling efi_init()? I can see x86 sets some efi_loader_signature
string in exit_boot() and checks against it later when calling
efi_init().

-- 
Catalin