1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2 /*
3  *  include/linux/userfaultfd.h
4  *
5  *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
6  *  Copyright (C) 2015  Red Hat, Inc.
7  *
8  */
9 
10 #ifndef _LINUX_USERFAULTFD_H
11 #define _LINUX_USERFAULTFD_H
12 
13 #include <linux/types.h>
14 
15 /* ioctls for /dev/userfaultfd */
16 #define USERFAULTFD_IOC 0xAA
17 #define USERFAULTFD_IOC_NEW _IO(USERFAULTFD_IOC, 0x00)
18 
19 /*
20  * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and
21  * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR.  In
22  * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ
23  * means the userland is reading).
24  */
25 #define UFFD_API ((__u64)0xAA)
26 #define UFFD_API_REGISTER_MODES (UFFDIO_REGISTER_MODE_MISSING |	\
27 				 UFFDIO_REGISTER_MODE_WP |	\
28 				 UFFDIO_REGISTER_MODE_MINOR)
29 #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP |	\
30 			   UFFD_FEATURE_EVENT_FORK |		\
31 			   UFFD_FEATURE_EVENT_REMAP |		\
32 			   UFFD_FEATURE_EVENT_REMOVE |		\
33 			   UFFD_FEATURE_EVENT_UNMAP |		\
34 			   UFFD_FEATURE_MISSING_HUGETLBFS |	\
35 			   UFFD_FEATURE_MISSING_SHMEM |		\
36 			   UFFD_FEATURE_SIGBUS |		\
37 			   UFFD_FEATURE_THREAD_ID |		\
38 			   UFFD_FEATURE_MINOR_HUGETLBFS |	\
39 			   UFFD_FEATURE_MINOR_SHMEM |		\
40 			   UFFD_FEATURE_EXACT_ADDRESS |		\
41 			   UFFD_FEATURE_WP_HUGETLBFS_SHMEM |	\
42 			   UFFD_FEATURE_WP_UNPOPULATED |	\
43 			   UFFD_FEATURE_POISON |		\
44 			   UFFD_FEATURE_WP_ASYNC)
45 #define UFFD_API_IOCTLS				\
46 	((__u64)1 << _UFFDIO_REGISTER |		\
47 	 (__u64)1 << _UFFDIO_UNREGISTER |	\
48 	 (__u64)1 << _UFFDIO_API)
49 #define UFFD_API_RANGE_IOCTLS			\
50 	((__u64)1 << _UFFDIO_WAKE |		\
51 	 (__u64)1 << _UFFDIO_COPY |		\
52 	 (__u64)1 << _UFFDIO_ZEROPAGE |		\
53 	 (__u64)1 << _UFFDIO_WRITEPROTECT |	\
54 	 (__u64)1 << _UFFDIO_CONTINUE |		\
55 	 (__u64)1 << _UFFDIO_POISON)
56 #define UFFD_API_RANGE_IOCTLS_BASIC		\
57 	((__u64)1 << _UFFDIO_WAKE |		\
58 	 (__u64)1 << _UFFDIO_COPY |		\
59 	 (__u64)1 << _UFFDIO_WRITEPROTECT |	\
60 	 (__u64)1 << _UFFDIO_CONTINUE |		\
61 	 (__u64)1 << _UFFDIO_POISON)
62 
63 /*
64  * Valid ioctl command number range with this API is from 0x00 to
65  * 0x3F.  UFFDIO_API is the fixed number, everything else can be
66  * changed by implementing a different UFFD_API. If sticking to the
67  * same UFFD_API more ioctl can be added and userland will be aware of
68  * which ioctl the running kernel implements through the ioctl command
69  * bitmask written by the UFFDIO_API.
70  */
71 #define _UFFDIO_REGISTER		(0x00)
72 #define _UFFDIO_UNREGISTER		(0x01)
73 #define _UFFDIO_WAKE			(0x02)
74 #define _UFFDIO_COPY			(0x03)
75 #define _UFFDIO_ZEROPAGE		(0x04)
76 #define _UFFDIO_WRITEPROTECT		(0x06)
77 #define _UFFDIO_CONTINUE		(0x07)
78 #define _UFFDIO_POISON			(0x08)
79 #define _UFFDIO_API			(0x3F)
80 
81 /* userfaultfd ioctl ids */
82 #define UFFDIO 0xAA
83 #define UFFDIO_API		_IOWR(UFFDIO, _UFFDIO_API,	\
84 				      struct uffdio_api)
85 #define UFFDIO_REGISTER		_IOWR(UFFDIO, _UFFDIO_REGISTER, \
86 				      struct uffdio_register)
87 #define UFFDIO_UNREGISTER	_IOR(UFFDIO, _UFFDIO_UNREGISTER,	\
88 				     struct uffdio_range)
89 #define UFFDIO_WAKE		_IOR(UFFDIO, _UFFDIO_WAKE,	\
90 				     struct uffdio_range)
91 #define UFFDIO_COPY		_IOWR(UFFDIO, _UFFDIO_COPY,	\
92 				      struct uffdio_copy)
93 #define UFFDIO_ZEROPAGE		_IOWR(UFFDIO, _UFFDIO_ZEROPAGE,	\
94 				      struct uffdio_zeropage)
95 #define UFFDIO_WRITEPROTECT	_IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \
96 				      struct uffdio_writeprotect)
97 #define UFFDIO_CONTINUE		_IOWR(UFFDIO, _UFFDIO_CONTINUE,	\
98 				      struct uffdio_continue)
99 #define UFFDIO_POISON		_IOWR(UFFDIO, _UFFDIO_POISON, \
100 				      struct uffdio_poison)
101 
102 /* read() structure */
103 struct uffd_msg {
104 	__u8	event;
105 
106 	__u8	reserved1;
107 	__u16	reserved2;
108 	__u32	reserved3;
109 
110 	union {
111 		struct {
112 			__u64	flags;
113 			__u64	address;
114 			union {
115 				__u32 ptid;
116 			} feat;
117 		} pagefault;
118 
119 		struct {
120 			__u32	ufd;
121 		} fork;
122 
123 		struct {
124 			__u64	from;
125 			__u64	to;
126 			__u64	len;
127 		} remap;
128 
129 		struct {
130 			__u64	start;
131 			__u64	end;
132 		} remove;
133 
134 		struct {
135 			/* unused reserved fields */
136 			__u64	reserved1;
137 			__u64	reserved2;
138 			__u64	reserved3;
139 		} reserved;
140 	} arg;
141 } __attribute__((packed));
142 
143 /*
144  * Start at 0x12 and not at 0 to be more strict against bugs.
145  */
146 #define UFFD_EVENT_PAGEFAULT	0x12
147 #define UFFD_EVENT_FORK		0x13
148 #define UFFD_EVENT_REMAP	0x14
149 #define UFFD_EVENT_REMOVE	0x15
150 #define UFFD_EVENT_UNMAP	0x16
151 
152 /* flags for UFFD_EVENT_PAGEFAULT */
153 #define UFFD_PAGEFAULT_FLAG_WRITE	(1<<0)	/* If this was a write fault */
154 #define UFFD_PAGEFAULT_FLAG_WP		(1<<1)	/* If reason is VM_UFFD_WP */
155 #define UFFD_PAGEFAULT_FLAG_MINOR	(1<<2)	/* If reason is VM_UFFD_MINOR */
156 
157 struct uffdio_api {
158 	/* userland asks for an API number and the features to enable */
159 	__u64 api;
160 	/*
161 	 * Kernel answers below with the all available features for
162 	 * the API, this notifies userland of which events and/or
163 	 * which flags for each event are enabled in the current
164 	 * kernel.
165 	 *
166 	 * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
167 	 * are to be considered implicitly always enabled in all kernels as
168 	 * long as the uffdio_api.api requested matches UFFD_API.
169 	 *
170 	 * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
171 	 * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
172 	 * hugetlbfs virtual memory ranges. Adding or not adding
173 	 * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
174 	 * no real functional effect after UFFDIO_API returns, but
175 	 * it's only useful for an initial feature set probe at
176 	 * UFFDIO_API time. There are two ways to use it:
177 	 *
178 	 * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
179 	 *    uffdio_api.features before calling UFFDIO_API, an error
180 	 *    will be returned by UFFDIO_API on a kernel without
181 	 *    hugetlbfs missing support
182 	 *
183 	 * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
184 	 *    uffdio_api.features and instead it will be set by the
185 	 *    kernel in the uffdio_api.features if the kernel supports
186 	 *    it, so userland can later check if the feature flag is
187 	 *    present in uffdio_api.features after UFFDIO_API
188 	 *    succeeded.
189 	 *
190 	 * UFFD_FEATURE_MISSING_SHMEM works the same as
191 	 * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
192 	 * (i.e. tmpfs and other shmem based APIs).
193 	 *
194 	 * UFFD_FEATURE_SIGBUS feature means no page-fault
195 	 * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead
196 	 * a SIGBUS signal will be sent to the faulting process.
197 	 *
198 	 * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will
199 	 * be returned, if feature is not requested 0 will be returned.
200 	 *
201 	 * UFFD_FEATURE_MINOR_HUGETLBFS indicates that minor faults
202 	 * can be intercepted (via REGISTER_MODE_MINOR) for
203 	 * hugetlbfs-backed pages.
204 	 *
205 	 * UFFD_FEATURE_MINOR_SHMEM indicates the same support as
206 	 * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead.
207 	 *
208 	 * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page
209 	 * faults would be provided and the offset within the page would not be
210 	 * masked.
211 	 *
212 	 * UFFD_FEATURE_WP_HUGETLBFS_SHMEM indicates that userfaultfd
213 	 * write-protection mode is supported on both shmem and hugetlbfs.
214 	 *
215 	 * UFFD_FEATURE_WP_UNPOPULATED indicates that userfaultfd
216 	 * write-protection mode will always apply to unpopulated pages
217 	 * (i.e. empty ptes).  This will be the default behavior for shmem
218 	 * & hugetlbfs, so this flag only affects anonymous memory behavior
219 	 * when userfault write-protection mode is registered.
220 	 *
221 	 * UFFD_FEATURE_WP_ASYNC indicates that userfaultfd write-protection
222 	 * asynchronous mode is supported in which the write fault is
223 	 * automatically resolved and write-protection is un-set.
224 	 * It implies UFFD_FEATURE_WP_UNPOPULATED.
225 	 */
226 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP		(1<<0)
227 #define UFFD_FEATURE_EVENT_FORK			(1<<1)
228 #define UFFD_FEATURE_EVENT_REMAP		(1<<2)
229 #define UFFD_FEATURE_EVENT_REMOVE		(1<<3)
230 #define UFFD_FEATURE_MISSING_HUGETLBFS		(1<<4)
231 #define UFFD_FEATURE_MISSING_SHMEM		(1<<5)
232 #define UFFD_FEATURE_EVENT_UNMAP		(1<<6)
233 #define UFFD_FEATURE_SIGBUS			(1<<7)
234 #define UFFD_FEATURE_THREAD_ID			(1<<8)
235 #define UFFD_FEATURE_MINOR_HUGETLBFS		(1<<9)
236 #define UFFD_FEATURE_MINOR_SHMEM		(1<<10)
237 #define UFFD_FEATURE_EXACT_ADDRESS		(1<<11)
238 #define UFFD_FEATURE_WP_HUGETLBFS_SHMEM		(1<<12)
239 #define UFFD_FEATURE_WP_UNPOPULATED		(1<<13)
240 #define UFFD_FEATURE_POISON			(1<<14)
241 #define UFFD_FEATURE_WP_ASYNC			(1<<15)
242 	__u64 features;
243 
244 	__u64 ioctls;
245 };
246 
247 struct uffdio_range {
248 	__u64 start;
249 	__u64 len;
250 };
251 
252 struct uffdio_register {
253 	struct uffdio_range range;
254 #define UFFDIO_REGISTER_MODE_MISSING	((__u64)1<<0)
255 #define UFFDIO_REGISTER_MODE_WP		((__u64)1<<1)
256 #define UFFDIO_REGISTER_MODE_MINOR	((__u64)1<<2)
257 	__u64 mode;
258 
259 	/*
260 	 * kernel answers which ioctl commands are available for the
261 	 * range, keep at the end as the last 8 bytes aren't read.
262 	 */
263 	__u64 ioctls;
264 };
265 
266 struct uffdio_copy {
267 	__u64 dst;
268 	__u64 src;
269 	__u64 len;
270 #define UFFDIO_COPY_MODE_DONTWAKE		((__u64)1<<0)
271 	/*
272 	 * UFFDIO_COPY_MODE_WP will map the page write protected on
273 	 * the fly.  UFFDIO_COPY_MODE_WP is available only if the
274 	 * write protected ioctl is implemented for the range
275 	 * according to the uffdio_register.ioctls.
276 	 */
277 #define UFFDIO_COPY_MODE_WP			((__u64)1<<1)
278 	__u64 mode;
279 
280 	/*
281 	 * "copy" is written by the ioctl and must be at the end: the
282 	 * copy_from_user will not read the last 8 bytes.
283 	 */
284 	__s64 copy;
285 };
286 
287 struct uffdio_zeropage {
288 	struct uffdio_range range;
289 #define UFFDIO_ZEROPAGE_MODE_DONTWAKE		((__u64)1<<0)
290 	__u64 mode;
291 
292 	/*
293 	 * "zeropage" is written by the ioctl and must be at the end:
294 	 * the copy_from_user will not read the last 8 bytes.
295 	 */
296 	__s64 zeropage;
297 };
298 
299 struct uffdio_writeprotect {
300 	struct uffdio_range range;
301 /*
302  * UFFDIO_WRITEPROTECT_MODE_WP: set the flag to write protect a range,
303  * unset the flag to undo protection of a range which was previously
304  * write protected.
305  *
306  * UFFDIO_WRITEPROTECT_MODE_DONTWAKE: set the flag to avoid waking up
307  * any wait thread after the operation succeeds.
308  *
309  * NOTE: Write protecting a region (WP=1) is unrelated to page faults,
310  * therefore DONTWAKE flag is meaningless with WP=1.  Removing write
311  * protection (WP=0) in response to a page fault wakes the faulting
312  * task unless DONTWAKE is set.
313  */
314 #define UFFDIO_WRITEPROTECT_MODE_WP		((__u64)1<<0)
315 #define UFFDIO_WRITEPROTECT_MODE_DONTWAKE	((__u64)1<<1)
316 	__u64 mode;
317 };
318 
319 struct uffdio_continue {
320 	struct uffdio_range range;
321 #define UFFDIO_CONTINUE_MODE_DONTWAKE		((__u64)1<<0)
322 	/*
323 	 * UFFDIO_CONTINUE_MODE_WP will map the page write protected on
324 	 * the fly.  UFFDIO_CONTINUE_MODE_WP is available only if the
325 	 * write protected ioctl is implemented for the range
326 	 * according to the uffdio_register.ioctls.
327 	 */
328 #define UFFDIO_CONTINUE_MODE_WP			((__u64)1<<1)
329 	__u64 mode;
330 
331 	/*
332 	 * Fields below here are written by the ioctl and must be at the end:
333 	 * the copy_from_user will not read past here.
334 	 */
335 	__s64 mapped;
336 };
337 
338 struct uffdio_poison {
339 	struct uffdio_range range;
340 #define UFFDIO_POISON_MODE_DONTWAKE		((__u64)1<<0)
341 	__u64 mode;
342 
343 	/*
344 	 * Fields below here are written by the ioctl and must be at the end:
345 	 * the copy_from_user will not read past here.
346 	 */
347 	__s64 updated;
348 };
349 
350 /*
351  * Flags for the userfaultfd(2) system call itself.
352  */
353 
354 /*
355  * Create a userfaultfd that can handle page faults only in user mode.
356  */
357 #define UFFD_USER_MODE_ONLY 1
358 
359 #endif /* _LINUX_USERFAULTFD_H */
360