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 */
103struct 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} __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
157struct 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
247struct uffdio_range {
248 __u64 start;
249 __u64 len;
250};
251
252struct 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
266struct 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
287struct 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
299struct 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
319struct 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
338struct 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

source code of linux/include/uapi/linux/userfaultfd.h