livepatch/core: Validate function old_name before 'klp_init_object_loaded'

Offering: HULK
hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4WBFN



--------------------------------

Refer to following procedure:
  klp_init_object
    klp_init_object_loaded
      klp_find_object_symbol <-- 1. oops happened when old_name is NULL!!!
    klp_init_func  <-- 2. currently old_name is first time check here

This problem was introduced in commit 7834e94c ("livepatch/arm64:
Fix func size less than limit") which exchange order of 'klp_init_func'
and 'klp_init_object_loaded' then cause old_name being used before check.

We move these checks before 'klp_init_object_loaded' and add several
logs to tell why check failed.

Fixes: 7834e94c ("livepatch/arm64: Fix func size less than limit")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>