usercopy.c
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/*
* User address space access functions.
*
* For licencing details see kernel-base/COPYING
*/
#include <linux/highmem.h>
#include <linux/module.h>
/*
* best effort, GUP based copy_from_user() that is NMI-safe
*/
unsigned long
copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
{
unsigned long offset, addr = (unsigned long)from;
unsigned long size, len = 0;
struct page *page;
void *map;
int ret;
do {
ret = __get_user_pages_fast(addr, 1, 0, &page);
if (!ret)
break;
offset = addr & (PAGE_SIZE - 1);
size = min(PAGE_SIZE - offset, n - len);
map = kmap_atomic(page);
memcpy(to, map+offset, size);
kunmap_atomic(map);
put_page(page);
len += size;
to += size;
addr += size;
} while (len < n);
return len;
}
EXPORT_SYMBOL_GPL(copy_from_user_nmi);