Re: [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

[Yury Norov <ynorov@caviumnetworks.com>]

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...