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1/* SPDX-License-Identifier: GPL-2.0 */
2
3/*
4 * Copyright (c) 2025, Google LLC.
5 * Pasha Tatashin <pasha.tatashin@soleen.com>
6 */
7#ifndef _LINUX_LIVEUPDATE_H
8#define _LINUX_LIVEUPDATE_H
9
10#include <linux/bug.h>
11#include <linux/compiler.h>
12#include <linux/kho/abi/luo.h>
13#include <linux/list.h>
14#include <linux/types.h>
15#include <uapi/linux/liveupdate.h>
16
17struct liveupdate_file_handler;
18struct file;
19
20/**
21 * struct liveupdate_file_op_args - Arguments for file operation callbacks.
22 * @handler: The file handler being called.
23 * @retrieved: The retrieve status for the 'can_finish / finish'
24 * operation.
25 * @file: The file object. For retrieve: [OUT] The callback sets
26 * this to the new file. For other ops: [IN] The caller sets
27 * this to the file being operated on.
28 * @serialized_data: The opaque u64 handle, preserve/prepare/freeze may update
29 * this field.
30 * @private_data: Private data for the file used to hold runtime state that
31 * is not preserved. Set by the handler's .preserve()
32 * callback, and must be freed in the handler's
33 * .unpreserve() callback.
34 *
35 * This structure bundles all parameters for the file operation callbacks.
36 * The 'data' and 'file' fields are used for both input and output.
37 */
38struct liveupdate_file_op_args {
39 struct liveupdate_file_handler *handler;
40 bool retrieved;
41 struct file *file;
42 u64 serialized_data;
43 void *private_data;
44};
45
46/**
47 * struct liveupdate_file_ops - Callbacks for live-updatable files.
48 * @can_preserve: Required. Lightweight check to see if this handler is
49 * compatible with the given file.
50 * @preserve: Required. Performs state-saving for the file.
51 * @unpreserve: Required. Cleans up any resources allocated by @preserve.
52 * @freeze: Optional. Final actions just before kernel transition.
53 * @unfreeze: Optional. Undo freeze operations.
54 * @retrieve: Required. Restores the file in the new kernel.
55 * @can_finish: Optional. Check if this FD can finish, i.e. all restoration
56 * pre-requirements for this FD are satisfied. Called prior to
57 * finish, in order to do successful finish calls for all
58 * resources in the session.
59 * @finish: Required. Final cleanup in the new kernel.
60 * @owner: Module reference
61 *
62 * All operations (except can_preserve) receive a pointer to a
63 * 'struct liveupdate_file_op_args' containing the necessary context.
64 */
65struct liveupdate_file_ops {
66 bool (*can_preserve)(struct liveupdate_file_handler *handler,
67 struct file *file);
68 int (*preserve)(struct liveupdate_file_op_args *args);
69 void (*unpreserve)(struct liveupdate_file_op_args *args);
70 int (*freeze)(struct liveupdate_file_op_args *args);
71 void (*unfreeze)(struct liveupdate_file_op_args *args);
72 int (*retrieve)(struct liveupdate_file_op_args *args);
73 bool (*can_finish)(struct liveupdate_file_op_args *args);
74 void (*finish)(struct liveupdate_file_op_args *args);
75 struct module *owner;
76};
77
78/**
79 * struct liveupdate_file_handler - Represents a handler for a live-updatable file type.
80 * @ops: Callback functions
81 * @compatible: The compatibility string (e.g., "memfd-v1", "vfiofd-v1")
82 * that uniquely identifies the file type this handler
83 * supports. This is matched against the compatible string
84 * associated with individual &struct file instances.
85 *
86 * Modules that want to support live update for specific file types should
87 * register an instance of this structure. LUO uses this registration to
88 * determine if a given file can be preserved and to find the appropriate
89 * operations to manage its state across the update.
90 */
91struct liveupdate_file_handler {
92 const struct liveupdate_file_ops *ops;
93 const char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
94
95 /* private: */
96
97 /*
98 * Used for linking this handler instance into a global list of
99 * registered file handlers.
100 */
101 struct list_head __private list;
102};
103
104#ifdef CONFIG_LIVEUPDATE
105
106/* Return true if live update orchestrator is enabled */
107bool liveupdate_enabled(void);
108
109/* Called during kexec to tell LUO that entered into reboot */
110int liveupdate_reboot(void);
111
112int liveupdate_register_file_handler(struct liveupdate_file_handler *fh);
113int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh);
114
115#else /* CONFIG_LIVEUPDATE */
116
117static inline bool liveupdate_enabled(void)
118{
119 return false;
120}
121
122static inline int liveupdate_reboot(void)
123{
124 return 0;
125}
126
127static inline int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
128{
129 return -EOPNOTSUPP;
130}
131
132static inline int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
133{
134 return -EOPNOTSUPP;
135}
136
137#endif /* CONFIG_LIVEUPDATE */
138#endif /* _LINUX_LIVEUPDATE_H */