On Thu, Jan 14, 2016 at 08:23:17PM +0300, Yury Norov wrote:

The problem that makes us to use wrappers is that some compat
architectures allows user code to access top halves of registers.
This is not a problem for syscalls that are already handled by compat
code, or for that who has types of the same size in kernel and
userspace. In case of lp64/ilp32 the problem is in pointer types, long,
unsigned long.

S390 folks already have the solution for it. In this patch,
it is turned to be general, as arm64/ilp32 needs it too.

Build-tested on s390.

Signed-off-by: Yury Norov <redacted>
---

[...]

+#ifndef __SC_COMPAT_CAST
+#define __SC_COMPAT_CAST(t, a)	((t)(long) ((t)(-1) < 0 ? (s32)(a) : (u32)(a)))
+#endif

It should be like:
#define __SC_COMPAT_CAST(t, a)	((t) ((t)(-1) < 0 ? (s64)(s32)(a) : (u64)(u32)(a)))