arm64: uaccess: simplify __copy_user_flushcache()

mainline inclusion
from mainline-v5.11-rc1
commit 9e94fdad
category: performance
bugzilla: https://e.gitee.com/open_euler/issues/list?issue=I4SCW7
CVE: NA

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Currently __copy_user_flushcache() open-codes raw_copy_from_user(), and
doesn't use uaccess_mask_ptr() on the user address. Let's have it call
raw_copy_from_user(), which is both a simplification and ensures that
user pointers are masked under speculation.

There should be no functional change as a result of this patch.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Reviewed-by: NRobin Murphy <robin.murphy@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201202131558.39270-6-mark.rutland@arm.comSigned-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NZhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm64/lib/uaccess_flushcache.c

@@ -30,9 +30,7 @@ unsigned long __copy_user_flushcache(void *to, const void __user *from,
 {
 	unsigned long rc;
 
-	uaccess_enable_not_uao();
-	rc = __arch_copy_from_user(to, from, n);
-	uaccess_disable_not_uao();
+	rc = raw_copy_from_user(to, from, n);
 
 	/* See above */
 	__clean_dcache_area_pop(to, n - rc);