[PATCH v2] lib/crypto: riscv/chacha: Avoid s0/fp register

[Eric Biggers]

On Tue, Dec 02, 2025 at 01:25:07PM +0800, Vivian Wang wrote:
> In chacha_zvkb, avoid using the s0 register, which is the frame pointer,
> by reallocating KEY0 to t5. This makes stack traces available if e.g. a
> crash happens in chacha_zvkb.
> 
> No frame pointer maintenence is otherwise required since this is a leaf
> function.

maintenence => maintenance

>  SYM_FUNC_START(chacha_zvkb)
>  	addi		sp, sp, -96
> -	sd		s0, 0(sp)

I know it's annoying, but would you mind also changing the 96 to 88, and
decreasing all the offsets by 8, so that we don't leave a hole in the
stack where s0 used to be?  Likewise at the end of the function.

- Eric