arm64: remove page granularity limitation from KFENCE

maillist inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4XWBS

Reference: https://lore.kernel.org/all/20210524172433.015b3b6b@xhacker.debian/



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Jisheng Zhang has another way of saving memory, we combine his two patches into
one and made some adaptations with dynamic kfence objects.

Description of the original patch:

Some architectures may want to allocate the __kfence_pool differently
for example, allocate the __kfence_pool earlier before paging_init().
We also delay the memset() to kfence_init_pool().

KFENCE requires linear map to be mapped at page granularity, so that
it is possible to protect/unprotect single pages in the KFENCE pool.
Currently if KFENCE is enabled, arm64 maps all pages at page
granularity, it seems overkilled. In fact, we only need to map the
pages in KFENCE pool itself at page granularity. We acchieve this goal
by allocating KFENCE pool before paging_init() so we know the KFENCE
pool address, then we take care to map the pool at page granularity
during map_mem().

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>