Merge branch 'bpf-improve-verifier-ARG_CONST_SIZE_OR_ZERO-semantics'

Yonghong Song says:

====================
bpf: improve verifier ARG_CONST_SIZE_OR_ZERO semantics

This patch set intends to change verifier ARG_CONST_SIZE_OR_ZERO
semantics so that simpler bpf programs can be written with verifier
acceptance. Patch #1 comment provided the detailed examples and
the patch itself implements the new semantics. Patch #2
changes bpf_probe_read helper arg2 type from
ARG_CONST_SIZE to ARG_CONST_SIZE_OR_ZERO. Patch #3 fixed a few
test cases and added some for better coverage.
====================

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