ascend inclusion
category: Feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4NDAW
CVE: NA

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This share a kernel memory range to userspace.
Introduce vm_struct flag VM_SHAREPOOL to indicate that a vm_struct
shared to userspace and we cannot vfree such a vm_area.
Signed-off-by: NWang Wensheng <wangwensheng4@huawei.com>
Signed-off-by: NTang Yizhou <tangyizhou@huawei.com>
Signed-off-by: NZhou Guanghui <zhouguanghui1@huawei.com>
Reviewed-by: Kefeng Wang<wangkefeng.wang@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>