[U-Boot] [RFC 1/1] efi_loader: fix building of helloworld.efi on x86_64

[Heinrich Schuchardt]

On 09/12/2017 03:24 PM, Bin Meng wrote:
> Hi Heinrich,
> 
> On Tue, Sep 12, 2017 at 4:18 PM, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>> On 09/12/2017 05:00 AM, Bin Meng wrote:
>>> Hi Heinrich,
>>>
>>> On Sun, Sep 10, 2017 at 4:55 PM, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>>> Variable EFI_LDS is set based on CONFIG_EFI_STUB_64BIT.
>>>> It influences which lds script is used for compiling helloworld.efi.
>>>> This results in building helloworld.efi failing on x86_64 if
>>>> CONFIG_EFI_STUB_64BIT is not set. CONFIG_EFI_STUB_64BIT is only
>>>> visible if EFI_STUB is selected. We should be able to compile a 64bit
>>>> helloworld.efi irrespective of EFI_STUB.
>>>>
>>>> With the patch the bitness of the efi build is taken from the
>>>> architecture choice.
>>>>
>>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>>> ---
>>>> For proper testing
>>>> https://lists.denx.de/pipermail/u-boot/2017-September/305184.html
>>>> must be fixed.
>>>>
>>>> So I send this as RFC.
>>>
>>> Sorry I missed this. This does not go to the U-Boot ML. Did you intend
>>> to keep the discussion among us?
>>>
>> CC: U-Boot Mailing List <u-boot at lists.denx.de>
>>
>>>>
>>>> Alex, do you remember why CONFIG_EFI_STUB_64BIT was introduced in the
>>>> first place.
>>>>
>>>
>>> The CONFIG_EFI_STUB_64BIT was introduced to support booting from a
>>> 64-bit EFI BIOS.
>>>
>>>> Would you ever use a stub with a different bitness than U-Boot?
>>>>
>>>
>>> Yes, for example U-Boot x86 32-bit to boot a 64-bit EFI payload.
>>
>> My understanding is that the EFI stub is used if U-Boot is loaded as an
>> EFI application.
>>
> 
> Maybe there is some confusion. I was referring to the EFI payload as
> documented in doc/README.efi. Are you referring to the same EFI
> application in that doc?
> 

Ok, "U-Boot on EFI".

So I guess we have to separate the $LDS_EFI used for the stub from the
one used for helloworld.efi.

>> It has nothing to do with the EFI application or driver loaded by
>> U-boot's bootefi command, which I assume you reference as "to boot a
>> 64-bit EFI payload".
>>
>> A stub with different bitness than U-Boot would be needed if we wanted
>> to load 64 bit U-Boot as a 32 bit EFI application or a 32 bit U-Boot as
>> a 64 bit EFI application. Is this required in any scenario?
>>
> 
> Regards,
> Bin
>