--- zzzz-none-000/linux-3.10.107/arch/arm/lib/uaccess_with_memcpy.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/arm/lib/uaccess_with_memcpy.c	2021-02-04 17:41:59.000000000 +0000
@@ -18,6 +18,7 @@
 #include <linux/hardirq.h> /* for in_atomic() */
 #include <linux/gfp.h>
 #include <linux/highmem.h>
+#include <linux/hugetlb.h>
 #include <asm/current.h>
 #include <asm/page.h>
 
@@ -40,7 +41,35 @@
 		return 0;
 
 	pmd = pmd_offset(pud, addr);
-	if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd)))
+	if (unlikely(pmd_none(*pmd)))
+		return 0;
+
+	/*
+	 * A pmd can be bad if it refers to a HugeTLB or THP page.
+	 *
+	 * Both THP and HugeTLB pages have the same pmd layout
+	 * and should not be manipulated by the pte functions.
+	 *
+	 * Lock the page table for the destination and check
+	 * to see that it's still huge and whether or not we will
+	 * need to fault on write, or if we have a splitting THP.
+	 */
+	if (unlikely(pmd_thp_or_huge(*pmd))) {
+		ptl = &current->mm->page_table_lock;
+		spin_lock(ptl);
+		if (unlikely(!pmd_thp_or_huge(*pmd)
+			|| pmd_hugewillfault(*pmd)
+			|| pmd_trans_splitting(*pmd))) {
+			spin_unlock(ptl);
+			return 0;
+		}
+
+		*ptep = NULL;
+		*ptlp = ptl;
+		return 1;
+	}
+
+	if (unlikely(pmd_bad(*pmd)))
 		return 0;
 
 	pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
@@ -59,6 +88,7 @@
 static unsigned long noinline
 __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
 {
+	unsigned long ua_flags;
 	int atomic;
 
 	if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
@@ -67,7 +97,7 @@
 	}
 
 	/* the mmap semaphore is taken only if not in an atomic context */
-	atomic = in_atomic();
+	atomic = faulthandler_disabled();
 
 	if (!atomic)
 		down_read(&current->mm->mmap_sem);
@@ -89,12 +119,17 @@
 		if (tocopy > n)
 			tocopy = n;
 
+		ua_flags = uaccess_save_and_enable();
 		memcpy((void *)to, from, tocopy);
+		uaccess_restore(ua_flags);
 		to += tocopy;
 		from += tocopy;
 		n -= tocopy;
 
-		pte_unmap_unlock(pte, ptl);
+		if (pte)
+			pte_unmap_unlock(pte, ptl);
+		else
+			spin_unlock(ptl);
 	}
 	if (!atomic)
 		up_read(&current->mm->mmap_sem);
@@ -104,7 +139,7 @@
 }
 
 unsigned long
-__copy_to_user(void __user *to, const void *from, unsigned long n)
+arm_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	/*
 	 * This test is stubbed out of the main function above to keep
@@ -113,14 +148,21 @@
 	 * With frame pointer disabled, tail call optimization kicks in
 	 * as well making this test almost invisible.
 	 */
-	if (n < 64)
-		return __copy_to_user_std(to, from, n);
-	return __copy_to_user_memcpy(to, from, n);
+	if (n < 64) {
+		unsigned long ua_flags = uaccess_save_and_enable();
+		n = __copy_to_user_std(to, from, n);
+		uaccess_restore(ua_flags);
+	} else {
+		n = __copy_to_user_memcpy(to, from, n);
+	}
+	return n;
 }
 	
 static unsigned long noinline
 __clear_user_memset(void __user *addr, unsigned long n)
 {
+	unsigned long ua_flags;
+
 	if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
 		memset((void *)addr, 0, n);
 		return 0;
@@ -143,11 +185,16 @@
 		if (tocopy > n)
 			tocopy = n;
 
+		ua_flags = uaccess_save_and_enable();
 		memset((void *)addr, 0, tocopy);
+		uaccess_restore(ua_flags);
 		addr += tocopy;
 		n -= tocopy;
 
-		pte_unmap_unlock(pte, ptl);
+		if (pte)
+			pte_unmap_unlock(pte, ptl);
+		else
+			spin_unlock(ptl);
 	}
 	up_read(&current->mm->mmap_sem);
 
@@ -155,12 +202,17 @@
 	return n;
 }
 
-unsigned long __clear_user(void __user *addr, unsigned long n)
+unsigned long arm_clear_user(void __user *addr, unsigned long n)
 {
 	/* See rational for this in __copy_to_user() above. */
-	if (n < 64)
-		return __clear_user_std(addr, n);
-	return __clear_user_memset(addr, n);
+	if (n < 64) {
+		unsigned long ua_flags = uaccess_save_and_enable();
+		n = __clear_user_std(addr, n);
+		uaccess_restore(ua_flags);
+	} else {
+		n = __clear_user_memset(addr, n);
+	}
+	return n;
 }
 
 #if 0