1 files changed, 43 insertions, 0 deletions

diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
new file mode 100644
index 00000000000..97be9cb5448
--- /dev/null
+++ b/arch/x86/lib/usercopy.c
@@ -0,0 +1,43 @@
+/*
+ * 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);