question about RISCV EFI stub support

[Atish Patra]

On Wed, Feb 24, 2021 at 3:14 AM Kefeng Wang <wangkefeng.wang at huawei.com> wrote:
>
> Hi Atish and Ard,
>
> The commit "cb7d2dd5612a RISC-V: Add PE/COFF header for EFI stub" use
> c.li to
>
> add Magic "MZ" signature for PE/COFF header, which select RISCV_ISA_C,
> but "C"
>
> to the ISA is optional,  and if "C" is not support ,  EFI boot is not
> supported.
>
> Could we use ".word MZ_MAGIC" like x86 code or some other way to support
> "MZ" signature?
>
.word won't work but .short will. With .word, you end up 0000 in the 2
bytes which can be interpreted as illegal instruction.

I guess your larger objective is to make the C extension optional and
not enabled by default for the Linux kernel.
Do you just want it for a custom kernel or the upstream kernel ?

> Thanks,
>
> Kefeng
>
>
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-- 
Regards,
Atish