On Tue, 21 Apr 2015, Arnd Bergmann wrote:

quoted

COMPAT_SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
                       struct compat_itimerspec __user *, setting)

As a side note, I want to kill off the get_fs()/set_fs() calls in
the process. These always make me dizzy when I try to work out whether
there is a potential security hole (there is not in this case), and
they can be slow on some architectures.

Yeah. I have to take a deep breath every time I look at those :)
 

My preferred solution is one where we end up with the same syscalls
for both 32-bit and 64-bit, and basically use the
compat_sys_timer_gettime() implementation (or a simplified version)
for the existing , something like this:

No objections from my side. I was not looking into the syscall magic
yet. I just wanted to avoid the code churn and have the guts of the
syscalls factored out for simple reusage.

....
 

Note the use of a separate __kernel_itimerspec64 for the user interface
here, which I think will be needed to hide the differences between the
normal itimerspec on 64-bit machines, and the new itimerspec on 32-bit
platforms that will be defined differently (using 'long long').

Confused.

timespec64 / itimerspec64 should be the same independent of 64bit and
32bit. So why do we need another variant ?

I would also prefer not too many people to work on the syscalls, and
would rather have Baolin not touch any of the syscall prototypes for
the moment.

I did not ask him to change any of the syscall prototypes. I just
wanted him to split out the guts of the syscall into a seperate static
function to avoid all that code churn.

Thanks,

	tglx