[U-Boot] [PATCH 04/18] x86: efi: payload: Enforce toolchain to generate 64-bit EFI payload stub codes

[Bin Meng]

Hi Alex,

On Mon, Jun 11, 2018 at 1:55 PM, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 11.06.18 04:34, Bin Meng wrote:
>> On Mon, Jun 11, 2018 at 3:11 AM, Alexander Graf <agraf at suse.de> wrote:
>>>
>>>
>>> On 10.06.18 15:25, Bin Meng wrote:
>>>> Attempting to use a toolchain that is preconfigured to generate code
>>>> for the 32-bit architecture (i386), for example, the i386-linux-gcc
>>>> toolchain on kernel.org, to compile the 64-bit EFI payload does not
>>>> build. This updates the makefile fragments to ensure '-m64' is passed
>>>> to toolchain when building the 64-bit EFI payload stub codes.
>>>>
>>>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>>>
>>> Is there any sane reason to keep the split between EFI and U-Boot long
>>> size alive? The x86_64 U-Boot port is getting along reasonably well from
>>> what I can tell and 32bit UEFI implementations on 64-bit hosts are dying
>>> out.
>>>
>>
>> I think you are mixing two type of things. U-Boot building as 32-bit
>> or 64-bit is one thing. How to build U-Boot is another thing. This
>> patch was to address the build.
>>
>>> So can't we just remove all of that cruft altogether instead and just
>>> have x86_64 U-Boot with 64bit EFI stub and i386 U-Boot with 32bit EFI
>>> stub as only combinations?
>>>
>>
>> Some day once U-Boot x86_64 support is mature, we can consider that.
>> Even if we only support 64-bit U-Boot as the 64-bit EFI payload, that
>> does not mean i386-linux-gcc cannot be used. '-m64' is required to
>> pass to such toolchain to cross-compile 64-bit codes correctly.
>
> Yes, but then all of this would be unconditional for the full code base
> and not depend on CONFIG_EFI_STUB_64BIT at all :).
>

No, it is not unconditional. The '-m64' flag will only be added when
compiling efi_stub.c if CONFIG_EFI_STUB_64BIT is on. See below.

CFLAGS_efi_stub.o := -fpic -fshort-wchar -DEFI_STUB \
       $(if $(CONFIG_EFI_STUB_64BIT),-m64)

> I'm just wary that the efi payload code is quite hard to follow with all
> the combinations of 32/64 payload/u-boot bitnesses.

Yes, but not that bad. Still manageable :)

Regards,
Bin