livepatch: Narrow the scope of the 'text_mutex' lock

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6NVPT



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Currently, arch_klp_code_modify_{prepare, post_process} is implemented
only in the x86 architecture. It is used to hold the 'text_mutex' lock
before entering the stop_machine and modifying the code, and to release
the lock after exiting the stop_machine. klp_mem_prepare() needs to hold
the 'text_mutex' lock only when saving old instruction code on x86 to
ensure that it holds valid instructions.

Place klp_mem_prepare() before arch_klp_code_modify_prepare() and lock the
save instruction action separately to narrow the 'text_mutex' lock.

Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Reviewed-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>