1 /*
2  *  include/linux/userfaultfd.h
3  *
4  *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
5  *  Copyright (C) 2015  Red Hat, Inc.
6  *
7  */
8 
9 #ifndef _LINUX_USERFAULTFD_H
10 #define _LINUX_USERFAULTFD_H
11 
12 #include <linux/types.h>
13 
14 #define UFFD_API ((__u64)0xAA)
15 /*
16  * After implementing the respective features it will become:
17  * #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP | \
18  *			      UFFD_FEATURE_EVENT_FORK)
19  */
20 #define UFFD_API_FEATURES (0)
21 #define UFFD_API_IOCTLS				\
22 	((__u64)1 << _UFFDIO_REGISTER |		\
23 	 (__u64)1 << _UFFDIO_UNREGISTER |	\
24 	 (__u64)1 << _UFFDIO_API)
25 #define UFFD_API_RANGE_IOCTLS			\
26 	((__u64)1 << _UFFDIO_WAKE |		\
27 	 (__u64)1 << _UFFDIO_COPY |		\
28 	 (__u64)1 << _UFFDIO_ZEROPAGE)
29 
30 /*
31  * Valid ioctl command number range with this API is from 0x00 to
32  * 0x3F.  UFFDIO_API is the fixed number, everything else can be
33  * changed by implementing a different UFFD_API. If sticking to the
34  * same UFFD_API more ioctl can be added and userland will be aware of
35  * which ioctl the running kernel implements through the ioctl command
36  * bitmask written by the UFFDIO_API.
37  */
38 #define _UFFDIO_REGISTER		(0x00)
39 #define _UFFDIO_UNREGISTER		(0x01)
40 #define _UFFDIO_WAKE			(0x02)
41 #define _UFFDIO_COPY			(0x03)
42 #define _UFFDIO_ZEROPAGE		(0x04)
43 #define _UFFDIO_API			(0x3F)
44 
45 /* userfaultfd ioctl ids */
46 #define UFFDIO 0xAA
47 #define UFFDIO_API		_IOWR(UFFDIO, _UFFDIO_API,	\
48 				      struct uffdio_api)
49 #define UFFDIO_REGISTER		_IOWR(UFFDIO, _UFFDIO_REGISTER, \
50 				      struct uffdio_register)
51 #define UFFDIO_UNREGISTER	_IOR(UFFDIO, _UFFDIO_UNREGISTER,	\
52 				     struct uffdio_range)
53 #define UFFDIO_WAKE		_IOR(UFFDIO, _UFFDIO_WAKE,	\
54 				     struct uffdio_range)
55 #define UFFDIO_COPY		_IOWR(UFFDIO, _UFFDIO_COPY,	\
56 				      struct uffdio_copy)
57 #define UFFDIO_ZEROPAGE		_IOWR(UFFDIO, _UFFDIO_ZEROPAGE,	\
58 				      struct uffdio_zeropage)
59 
60 /* read() structure */
61 struct uffd_msg {
62 	__u8	event;
63 
64 	__u8	reserved1;
65 	__u16	reserved2;
66 	__u32	reserved3;
67 
68 	union {
69 		struct {
70 			__u64	flags;
71 			__u64	address;
72 		} pagefault;
73 
74 		struct {
75 			/* unused reserved fields */
76 			__u64	reserved1;
77 			__u64	reserved2;
78 			__u64	reserved3;
79 		} reserved;
80 	} arg;
81 } __packed;
82 
83 /*
84  * Start at 0x12 and not at 0 to be more strict against bugs.
85  */
86 #define UFFD_EVENT_PAGEFAULT	0x12
87 #if 0 /* not available yet */
88 #define UFFD_EVENT_FORK		0x13
89 #endif
90 
91 /* flags for UFFD_EVENT_PAGEFAULT */
92 #define UFFD_PAGEFAULT_FLAG_WRITE	(1<<0)	/* If this was a write fault */
93 #define UFFD_PAGEFAULT_FLAG_WP		(1<<1)	/* If reason is VM_UFFD_WP */
94 
95 struct uffdio_api {
96 	/* userland asks for an API number and the features to enable */
97 	__u64 api;
98 	/*
99 	 * Kernel answers below with the all available features for
100 	 * the API, this notifies userland of which events and/or
101 	 * which flags for each event are enabled in the current
102 	 * kernel.
103 	 *
104 	 * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
105 	 * are to be considered implicitly always enabled in all kernels as
106 	 * long as the uffdio_api.api requested matches UFFD_API.
107 	 */
108 #if 0 /* not available yet */
109 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP		(1<<0)
110 #define UFFD_FEATURE_EVENT_FORK			(1<<1)
111 #endif
112 	__u64 features;
113 
114 	__u64 ioctls;
115 };
116 
117 struct uffdio_range {
118 	__u64 start;
119 	__u64 len;
120 };
121 
122 struct uffdio_register {
123 	struct uffdio_range range;
124 #define UFFDIO_REGISTER_MODE_MISSING	((__u64)1<<0)
125 #define UFFDIO_REGISTER_MODE_WP		((__u64)1<<1)
126 	__u64 mode;
127 
128 	/*
129 	 * kernel answers which ioctl commands are available for the
130 	 * range, keep at the end as the last 8 bytes aren't read.
131 	 */
132 	__u64 ioctls;
133 };
134 
135 struct uffdio_copy {
136 	__u64 dst;
137 	__u64 src;
138 	__u64 len;
139 	/*
140 	 * There will be a wrprotection flag later that allows to map
141 	 * pages wrprotected on the fly. And such a flag will be
142 	 * available if the wrprotection ioctl are implemented for the
143 	 * range according to the uffdio_register.ioctls.
144 	 */
145 #define UFFDIO_COPY_MODE_DONTWAKE		((__u64)1<<0)
146 	__u64 mode;
147 
148 	/*
149 	 * "copy" is written by the ioctl and must be at the end: the
150 	 * copy_from_user will not read the last 8 bytes.
151 	 */
152 	__s64 copy;
153 };
154 
155 struct uffdio_zeropage {
156 	struct uffdio_range range;
157 #define UFFDIO_ZEROPAGE_MODE_DONTWAKE		((__u64)1<<0)
158 	__u64 mode;
159 
160 	/*
161 	 * "zeropage" is written by the ioctl and must be at the end:
162 	 * the copy_from_user will not read the last 8 bytes.
163 	 */
164 	__s64 zeropage;
165 };
166 
167 #endif /* _LINUX_USERFAULTFD_H */
168