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