1 files changed, 77 insertions, 0 deletions
diff --git a/include/linux/kho/abi/memfd.h b/include/linux/kho/abi/memfd.h
new file mode 100644
index 000000000000..da7d063474a1
--- /dev/null
+++ b/include/linux/kho/abi/memfd.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ *
+ * Copyright (C) 2025 Amazon.com Inc. or its affiliates.
+ * Pratyush Yadav <ptyadav@amazon.de>
+ */
+
+#ifndef _LINUX_KHO_ABI_MEMFD_H
+#define _LINUX_KHO_ABI_MEMFD_H
+
+#include <linux/types.h>
+#include <linux/kexec_handover.h>
+
+/**
+ * DOC: memfd Live Update ABI
+ *
+ * This header defines the ABI for preserving the state of a memfd across a
+ * kexec reboot using the LUO.
+ *
+ * The state is serialized into a packed structure `struct memfd_luo_ser`
+ * which is handed over to the next kernel via the KHO mechanism.
+ *
+ * This interface is a contract. Any modification to the structure layout
+ * constitutes a breaking change. Such changes require incrementing the
+ * version number in the MEMFD_LUO_FH_COMPATIBLE string.
+ */
+
+/**
+ * MEMFD_LUO_FOLIO_DIRTY - The folio is dirty.
+ *
+ * This flag indicates the folio contains data from user. A non-dirty folio is
+ * one that was allocated (say using fallocate(2)) but not written to.
+ */
+#define MEMFD_LUO_FOLIO_DIRTY		BIT(0)
+
+/**
+ * MEMFD_LUO_FOLIO_UPTODATE - The folio is up-to-date.
+ *
+ * An up-to-date folio has been zeroed out. shmem zeroes out folios on first
+ * use. This flag tracks which folios need zeroing.
+ */
+#define MEMFD_LUO_FOLIO_UPTODATE	BIT(1)
+
+/**
+ * struct memfd_luo_folio_ser - Serialized state of a single folio.
+ * @pfn:       The page frame number of the folio.
+ * @flags:     Flags to describe the state of the folio.
+ * @index:     The page offset (pgoff_t) of the folio within the original file.
+ */
+struct memfd_luo_folio_ser {
+	u64 pfn:52;
+	u64 flags:12;
+	u64 index;
+} __packed;
+
+/**
+ * struct memfd_luo_ser - Main serialization structure for a memfd.
+ * @pos:       The file's current position (f_pos).
+ * @size:      The total size of the file in bytes (i_size).
+ * @nr_folios: Number of folios in the folios array.
+ * @folios:    KHO vmalloc descriptor pointing to the array of
+ *             struct memfd_luo_folio_ser.
+ */
+struct memfd_luo_ser {
+	u64 pos;
+	u64 size;
+	u64 nr_folios;
+	struct kho_vmalloc folios;
+} __packed;
+
+/* The compatibility string for memfd file handler */
+#define MEMFD_LUO_FH_COMPATIBLE	"memfd-v1"
+
+#endif /* _LINUX_KHO_ABI_MEMFD_H */