[U-Boot] [PATCH 2/2] x86: Allow 32-bit toolchain to compile 64-bit U-Boot

[Bin Meng]

Hi Andy,

On Sun, Jul 23, 2017 at 6:01 PM, Andy Shevchenko
<andy.shevchenko at gmail.com> wrote:
> On Sun, Jul 23, 2017 at 12:37 PM, Bin Meng <bmeng.cn at gmail.com> wrote:
>> Attempting to use a 32-bit toolchain (eg: kernel.org 4.9
>> i386-linux-gcc) to compile 64-bit U-Boot (qemu-x86_64_defconfig)
>> fails with the following errors:
>>
>>   arch/x86/cpu/intel_common/microcode.c:79:2: error: PIC register
>>   clobbered by 'ebx' in 'asm'
>>
>> The issue is with 32-bit toolchain compiling sources for 64-bit.
>> Using a 64-bit toolchain (eg: kernel.org 4.9 x86_64-linux-gcc)
>> works out of the box. When compiling sources for 32-bit, '-m32' is
>> passed to the toolchain (no matter it's 32-bit or 64-bit).
>>
>> Now do the same thing, passing '-m64' to the toolchain for 64-bit
>> sources build.
>>
>
> The subject is a bit cofusing. As I read (and as I understand) we need
> to have 64-bit toolchain available (multilib package and so on).
> Basically what you do is "enforcing 64-bit toolchain to be used". Right?
>

Yes, multilib package is required for 64-bit toolchain to build 32-bit
U-Boot. Maybe the confusion comes from what we call 32-bit/64-bit
toolchains. Or maybe we should call it pre-configured toolchain for
building 32-bit/64-bit codes? The issue is when using kernel.org
i386-linux-gcc to build qemu-x86_64_defconfig (64-bit U-Boot), the
issue is seen. It's because the i386-linux-gcc is pre-configured with
'-m32' which is for building 32-bit codes.

>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>> ---
>>
>>  arch/x86/config.mk | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>

Regards,
Bin