Merge branch 'bpf-add-support-for-sys-enter-exit-tracepoints'

Merge branch 'bpf-add-support-for-sys-enter-exit-tracepoints'

Yonghong Song says:

====================
bpf: add support for sys_{enter|exit}_* tracepoints

Currently, bpf programs cannot be attached to sys_enter_* and sys_exit_*
style tracepoints. The main reason is that syscalls/sys_enter_* and syscalls/sys_exit_*
tracepoints are treated differently from other tracepoints and there
is no bpf hook to it.

This patch set adds bpf support for these syscalls tracepoints and also
adds a test case for it.

Changelogs:
v3 -> v4:
 - Check the legality of ctx offset access for syscall tracepoint as well.
   trace_event_get_offsets will return correct max offset for each
   specific syscall tracepoint.
 - Use variable length array to avoid hardcode 6 as the maximum
   arguments beyond syscall_nr.
v2 -> v3:
 - Fix a build issue
v1 -> v2:
 - Do not use TRACE_EVENT_FL_CAP_ANY to identify syscall tracepoint.
   Instead use trace_event_call->class.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>