Re: Introduction + interest in a riscv64 port of GNU Mach/Hurd

Hi Sergey,

Thanks for the input on the gp/x3 question — it's an interesting discussion
and I've noted it in the project progress.

Right now my focus is on getting the kernel functional: trap handling, UART
console, timer, Sv39 paging, and booting in QEMU. I'd prefer to defer the
ABI discussion until the kernel boots and we have a working base. At that
point we'll need to make this decision before starting the glibc port, and
it would be great to have your input then.

For now I'm going with the standard psABI conventions to avoid blocking on
toolchain changes.

Best,
Diego

El mar, 25 ago 2026 a la(s) 6:11 a.m., Sergey Bugaev ([email protected])
escribió:

> Hey,
>
> I'm happy to discuss (what I remember of) the AArch64 port design
> questions and decisions we made. Incidentally, I'm also looking into
> RISC-V (just learning basic things about it), so it would be
> interesting to watch, and potentially participate, in a Mach porting
> effort.
>
> And a small rant of what I've seen this far: the 'la' instruction (and
> the PIC/non-PIC terminology) makes no sense, what were they thinking?
> Fortunately it's only a pseudo-instruction and we can always use 'lga'
> and 'lla', or the actual instructions behind those, and ignore the
> existence of 'la'. The 'gp' thing (and the linker relaxation around
> it) only seem useful for firmwares and small kernels, and perhaps it'd
> actually be useful for gnumach, but it does seem fairly useless for
> userland (considering libraries), and there could be better ways to
> make use of the register. I heard that some ABIs (Haiku, Android,
> Fuschia?) are _not_ using x3 as gp, and there's official ELF support
> for this (Tag_RISCV_x3_reg_usage), what would you all think about
> potentially doing the same for riscv64-gnu userland?
>
> Sergey
>