Re: [PATCH] riscv: Add semihosting support [v4]

[Peter Maydell]

On Thu, 30 Jan 2020 at 11:38, Palmer Dabbelt <address@hidden> wrote:
> * The semihosting comment doesn't define the semihosting call numbers, just 
> the
>   sequence to get to a call.  That said, we haven't written down the Linux ABI
>   either -- though there's a much larger breadth of software out there that
>   implements it and won't break ABI compatibility, so maybe that's considered
>   sufficient in Linux land where it's not for semihosting.

I think the difference with Linux is that there's a clear
single authoritative source for what the ABI is -- Linus's
'mainline' kernel (so for instance random out-of-tree forks,
syscall patch proposals, etc that have not yet hit mainline
don't count as being fixed-in-stone ABI). Semihosting doesn't
have the same single clear "owning project", at least on
the Arm side of things.

I don't think a semihosting specification for RISC-V needs
necessarily to be a very heavyweight thing -- it is, after
all, a debug API at heart -- but I do agree that you should
have one.

thanks
-- PMM