Date: Mon, 5 Dec 2016 17:12:43 +0000
From: Catalin Marinas <catalin.marinas@arm.com>
To: Yury Norov <ynorov@caviumnetworks.com>
Cc: arnd@arndb.de, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
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        zhouchengming1@huawei.com, Prasun.Kapoor@caviumnetworks.com,
        agraf@suse.de, geert@linux-m68k.org, kilobyte@angband.pl,
        manuel.montezelo@gmail.com, pinskia@gmail.com, linyongting@huawei.com,
        klimov.linux@gmail.com, broonie@kernel.org,
        bamvor.zhangjian@huawei.com, maxim.kuvyrkov@linaro.org,
        Nathan_Lynch@mentor.com, schwidefsky@de.ibm.com, davem@davemloft.net,
        christoph.muellner@theobroma-systems.com
Subject: Re: [PATCH 11/18] arm64: ilp32: share aarch32 syscall handlers
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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