Re: That's how (why) BSD is dying (Was: BPF64)

On Mon, 16 Sep 2024 11:15:30 +1000
Simon Burge <[email protected]> wrote:

> Vadim Goncharov wrote:
> 
> > And e.g. https://en.wikipedia.org/wiki/MIPS_architecture
> > says 2 registers are for kernel - OK, and what if we are kernel
> > itself? :-) Do we need Thread Pointer of Global Pointer, or we can
> > stash them to stack? Etc.  
> 
> Where in that page does it say that a MIPS kernel can only use two
> registers?  It clearly says that two registers are reserved for kernel
> use, but certainly doesn't claim to say that the kernel can only use
> two regs.

Well, that's my bad wording. I wanted to say, that, a JIT compiler
can use N registers for it's needs, where N is get by taking
architecture's number of general-purpose registers - and subtracting
from them those which are required by platform ABI etc. Amongst those
requirements are stack pointer etc. and - on MIPS in userland - two
registers are listed "for kernel", so you subtract them, too. But what
if we are in MIPS kernel? Now, are those two registers still reserved
for something, or can be used by in-kernel JIT ? In other words, is it
(on MIPS) N in userland and N+2 in kernel, or not? or...?

-- 
WBR, @nuclight