1 files changed, 54 insertions, 0 deletions
diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
new file mode 100644
index 000000000000..988528b5da43
--- /dev/null
+++ b/include/linux/secretmem.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _LINUX_SECRETMEM_H
+#define _LINUX_SECRETMEM_H
+
+#ifdef CONFIG_SECRETMEM
+
+extern const struct address_space_operations secretmem_aops;
+
+static inline bool page_is_secretmem(struct page *page)
+{
+	struct address_space *mapping;
+
+	/*
+	 * Using page_mapping() is quite slow because of the actual call
+	 * instruction and repeated compound_head(page) inside the
+	 * page_mapping() function.
+	 * We know that secretmem pages are not compound and LRU so we can
+	 * save a couple of cycles here.
+	 */
+	if (PageCompound(page) || !PageLRU(page))
+		return false;
+
+	mapping = (struct address_space *)
+		((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
+
+	if (!mapping || mapping != page->mapping)
+		return false;
+
+	return mapping->a_ops == &secretmem_aops;
+}
+
+bool vma_is_secretmem(struct vm_area_struct *vma);
+bool secretmem_active(void);
+
+#else
+
+static inline bool vma_is_secretmem(struct vm_area_struct *vma)
+{
+	return false;
+}
+
+static inline bool page_is_secretmem(struct page *page)
+{
+	return false;
+}
+
+static inline bool secretmem_active(void)
+{
+	return false;
+}
+
+#endif /* CONFIG_SECRETMEM */
+
+#endif /* _LINUX_SECRETMEM_H */