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-rw-r--r--arch/x86/lib/usercopy.c43
1 files changed, 15 insertions, 28 deletions
diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index 4f74d94c8d97..5465b8613944 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -11,39 +11,26 @@
#include <linux/sched.h>
/*
- * best effort, GUP based copy_from_user() that is NMI-safe
+ * We rely on the nested NMI work to allow atomic faults from the NMI path; the
+ * nested NMI paths are careful to preserve CR2.
*/
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;
+ unsigned long ret;
if (__range_not_ok(from, n, TASK_SIZE))
- return len;
-
- 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;
+ return 0;
+
+ /*
+ * Even though this function is typically called from NMI/IRQ context
+ * disable pagefaults so that its behaviour is consistent even when
+ * called form other contexts.
+ */
+ pagefault_disable();
+ ret = __copy_from_user_inatomic(to, from, n);
+ pagefault_enable();
+
+ return n - ret;
}
EXPORT_SYMBOL_GPL(copy_from_user_nmi);