From mboxrd@z Thu Jan  1 00:00:00 1970
From: ynorov@caviumnetworks.com (Yury Norov)
Date: Wed, 2 Dec 2015 13:01:53 +0300
Subject: [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate
 table (in entry.S) to use it
In-Reply-To: <3754277.KmO9Nk3XLD@wuerfel>
References: <1447795019-30176-1-git-send-email-ynorov@caviumnetworks.com>
 <1447795019-30176-15-git-send-email-ynorov@caviumnetworks.com>
 <3754277.KmO9Nk3XLD@wuerfel>
Message-ID: <20151202100153.GA21461@yury-N73SV>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Nov 17, 2015 at 10:57:52PM +0100, Arnd Bergmann wrote:

It looks, all them are needed.

> > +asmlinkage long compat_sys_mmap2_wrapper(void);
> > +#define sys_mmap2                      compat_sys_mmap2_wrapper

This wrapper checks alignement of pgoff, if page sise is greater than
4K

> > +asmlinkage long compat_sys_fstatfs64_wrapper(void);
> > +#define compat_sys_fstatfs64    compat_sys_fstatfs64_wrapper
> > +asmlinkage long compat_sys_statfs64_wrapper(void);
> > +#define compat_sys_statfs64             compat_sys_statfs64_wrapper

This two hacks fix an alignment issue. I didn't check all details but
it looks like sizeof(compat_statfs64) is different in kernel and library.
And this size is passed as 2nd argument to compat syscalls. We can
handle it in userspace but I don't see any advantage. 

All this handlers are shared between ilp32 and aarch32.
This is best we came up, as it doesn't add new hacks, but reuses old
ones...