Re: [PATCH 11/18] arm64: ilp32: share aarch32 syscall handlers

[Catalin Marinas]

On Fri, Oct 21, 2016 at 11:33:10PM +0300, Yury Norov wrote:
> off_t is  passed in register pair just like in aarch32.
> In this patch corresponding aarch32 handlers are shared to
> ilp32 code.
[...]
> +/*
> + * Note: off_4k (w5) is always in units of 4K. If we can't do the
> + * requested offset because it is not page-aligned, we return -EINVAL.
> + */
> +ENTRY(compat_sys_mmap2_wrapper)
> +#if PAGE_SHIFT > 12
> +	tst	w5, #~PAGE_MASK >> 12
> +	b.ne	1f
> +	lsr	w5, w5, #PAGE_SHIFT - 12
> +#endif
> +	b	sys_mmap_pgoff
> +1:	mov	x0, #-EINVAL
> +	ret
> +ENDPROC(compat_sys_mmap2_wrapper)

For compat sys_mmap2, the pgoff argument is in multiples of 4K. This was
traditionally used for architectures where off_t is 32-bit to allow
mapping files to 2^44.

Since off_t is 64-bit with AArch64/ILP32, should we just pass the off_t
as a 64-bit value in two different registers (w5 and w6)?

-- 
Catalin