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