1 files changed, 16 insertions, 0 deletions

diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index 51e5cd9b906a..5dbbaa6e594c 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -85,3 +85,19 @@ int memcpy_real(void *dest, void *src, size_t count)
         arch_local_irq_restore(flags);
         return rc;
 }
+
+/*
+ * Copy memory to absolute zero
+ */
+void copy_to_absolute_zero(void *dest, void *src, size_t count)
+{
+        unsigned long cr0;
+
+        BUG_ON((unsigned long) dest + count >= sizeof(struct _lowcore));
+        preempt_disable();
+        __ctl_store(cr0, 0, 0);
+        __ctl_clear_bit(0, 28); /* disable lowcore protection */
+        memcpy_real(dest + store_prefix(), src, count);
+        __ctl_load(cr0, 0, 0);
+        preempt_enable();
+}