linux-user: fix O_NONBLOCK in signalfd4() and eventfd2() syscalls

linux-user: fix O_NONBLOCK in signalfd4() and eventfd2() syscalls

On the hppa target userspace binaries may call signalfd4() and
eventfd2() with an old TARGET_O_NONBLOCK value of 000200004 instead of
000200000 for the "mask" syscall parameter, in which case the current
emulation doesn't handle the translation to the native O_NONBLOCK value
correctly.

The 0x04 bit is not masked out before the new O_NONBLOCK bit is set and
as such when calling the native syscall errors out with EINVAL.

Fix this by introducing TARGET_O_NONBLOCK_MASK which is used to mask off
all possible bits. This define defaults to TARGET_O_NONBLOCK when not
defined otherwise, so for all other targets the implementation will
behave as before.

This patch needs to be applied on top of my previous two patches.

Bug was found and patch was verified by using qemu-hppa as debian buildd
server on x86_64.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210210061214.GA221322@ls3530.fritz.box>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>