question about RISCV EFI stub support

Atish Patra atishp at
Wed Feb 24 18:35:52 EST 2021

On Wed, Feb 24, 2021 at 3:14 AM Kefeng Wang < at> wrote:
> Hi Atish and Ard,
> The commit "cb7d2dd5612a RISC-V: Add PE/COFF header for EFI stub" use
> 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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