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/* 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 */
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