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 UFFD_FEATURE_MOVE)
46#define UFFD_API_IOCTLS \
47 ((__u64)1 << _UFFDIO_REGISTER | \
48 (__u64)1 << _UFFDIO_UNREGISTER | \
49 (__u64)1 << _UFFDIO_API)
50#define UFFD_API_RANGE_IOCTLS \
51 ((__u64)1 << _UFFDIO_WAKE | \
52 (__u64)1 << _UFFDIO_COPY | \
53 (__u64)1 << _UFFDIO_ZEROPAGE | \
54 (__u64)1 << _UFFDIO_MOVE | \
55 (__u64)1 << _UFFDIO_WRITEPROTECT | \
56 (__u64)1 << _UFFDIO_CONTINUE | \
57 (__u64)1 << _UFFDIO_POISON)
58#define UFFD_API_RANGE_IOCTLS_BASIC \
59 ((__u64)1 << _UFFDIO_WAKE | \
60 (__u64)1 << _UFFDIO_COPY | \
61 (__u64)1 << _UFFDIO_WRITEPROTECT | \
62 (__u64)1 << _UFFDIO_CONTINUE | \
63 (__u64)1 << _UFFDIO_POISON)
64
65/*
66 * Valid ioctl command number range with this API is from 0x00 to
67 * 0x3F. UFFDIO_API is the fixed number, everything else can be
68 * changed by implementing a different UFFD_API. If sticking to the
69 * same UFFD_API more ioctl can be added and userland will be aware of
70 * which ioctl the running kernel implements through the ioctl command
71 * bitmask written by the UFFDIO_API.
72 */
73#define _UFFDIO_REGISTER (0x00)
74#define _UFFDIO_UNREGISTER (0x01)
75#define _UFFDIO_WAKE (0x02)
76#define _UFFDIO_COPY (0x03)
77#define _UFFDIO_ZEROPAGE (0x04)
78#define _UFFDIO_MOVE (0x05)
79#define _UFFDIO_WRITEPROTECT (0x06)
80#define _UFFDIO_CONTINUE (0x07)
81#define _UFFDIO_POISON (0x08)
82#define _UFFDIO_API (0x3F)
83
84/* userfaultfd ioctl ids */
85#define UFFDIO 0xAA
86#define UFFDIO_API _IOWR(UFFDIO, _UFFDIO_API, \
87 struct uffdio_api)
88#define UFFDIO_REGISTER _IOWR(UFFDIO, _UFFDIO_REGISTER, \
89 struct uffdio_register)
90#define UFFDIO_UNREGISTER _IOR(UFFDIO, _UFFDIO_UNREGISTER, \
91 struct uffdio_range)
92#define UFFDIO_WAKE _IOR(UFFDIO, _UFFDIO_WAKE, \
93 struct uffdio_range)
94#define UFFDIO_COPY _IOWR(UFFDIO, _UFFDIO_COPY, \
95 struct uffdio_copy)
96#define UFFDIO_ZEROPAGE _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \
97 struct uffdio_zeropage)
98#define UFFDIO_MOVE _IOWR(UFFDIO, _UFFDIO_MOVE, \
99 struct uffdio_move)
100#define UFFDIO_WRITEPROTECT _IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \
101 struct uffdio_writeprotect)
102#define UFFDIO_CONTINUE _IOWR(UFFDIO, _UFFDIO_CONTINUE, \
103 struct uffdio_continue)
104#define UFFDIO_POISON _IOWR(UFFDIO, _UFFDIO_POISON, \
105 struct uffdio_poison)
106
107/* read() structure */
108struct uffd_msg {
109 __u8 event;
110
111 __u8 reserved1;
112 __u16 reserved2;
113 __u32 reserved3;
114
115 union {
116 struct {
117 __u64 flags;
118 __u64 address;
119 union {
120 __u32 ptid;
121 } feat;
122 } pagefault;
123
124 struct {
125 __u32 ufd;
126 } fork;
127
128 struct {
129 __u64 from;
130 __u64 to;
131 __u64 len;
132 } remap;
133
134 struct {
135 __u64 start;
136 __u64 end;
137 } remove;
138
139 struct {
140 /* unused reserved fields */
141 __u64 reserved1;
142 __u64 reserved2;
143 __u64 reserved3;
144 } reserved;
145 } arg;
146} __packed;
147
148/*
149 * Start at 0x12 and not at 0 to be more strict against bugs.
150 */
151#define UFFD_EVENT_PAGEFAULT 0x12
152#define UFFD_EVENT_FORK 0x13
153#define UFFD_EVENT_REMAP 0x14
154#define UFFD_EVENT_REMOVE 0x15
155#define UFFD_EVENT_UNMAP 0x16
156
157/* flags for UFFD_EVENT_PAGEFAULT */
158#define UFFD_PAGEFAULT_FLAG_WRITE (1<<0) /* If this was a write fault */
159#define UFFD_PAGEFAULT_FLAG_WP (1<<1) /* If reason is VM_UFFD_WP */
160#define UFFD_PAGEFAULT_FLAG_MINOR (1<<2) /* If reason is VM_UFFD_MINOR */
161
162struct uffdio_api {
163 /* userland asks for an API number and the features to enable */
164 __u64 api;
165 /*
166 * Kernel answers below with the all available features for
167 * the API, this notifies userland of which events and/or
168 * which flags for each event are enabled in the current
169 * kernel.
170 *
171 * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
172 * are to be considered implicitly always enabled in all kernels as
173 * long as the uffdio_api.api requested matches UFFD_API.
174 *
175 * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
176 * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
177 * hugetlbfs virtual memory ranges. Adding or not adding
178 * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
179 * no real functional effect after UFFDIO_API returns, but
180 * it's only useful for an initial feature set probe at
181 * UFFDIO_API time. There are two ways to use it:
182 *
183 * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
184 * uffdio_api.features before calling UFFDIO_API, an error
185 * will be returned by UFFDIO_API on a kernel without
186 * hugetlbfs missing support
187 *
188 * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
189 * uffdio_api.features and instead it will be set by the
190 * kernel in the uffdio_api.features if the kernel supports
191 * it, so userland can later check if the feature flag is
192 * present in uffdio_api.features after UFFDIO_API
193 * succeeded.
194 *
195 * UFFD_FEATURE_MISSING_SHMEM works the same as
196 * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
197 * (i.e. tmpfs and other shmem based APIs).
198 *
199 * UFFD_FEATURE_SIGBUS feature means no page-fault
200 * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead
201 * a SIGBUS signal will be sent to the faulting process.
202 *
203 * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will
204 * be returned, if feature is not requested 0 will be returned.
205 *
206 * UFFD_FEATURE_MINOR_HUGETLBFS indicates that minor faults
207 * can be intercepted (via REGISTER_MODE_MINOR) for
208 * hugetlbfs-backed pages.
209 *
210 * UFFD_FEATURE_MINOR_SHMEM indicates the same support as
211 * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead.
212 *
213 * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page
214 * faults would be provided and the offset within the page would not be
215 * masked.
216 *
217 * UFFD_FEATURE_WP_HUGETLBFS_SHMEM indicates that userfaultfd
218 * write-protection mode is supported on both shmem and hugetlbfs.
219 *
220 * UFFD_FEATURE_WP_UNPOPULATED indicates that userfaultfd
221 * write-protection mode will always apply to unpopulated pages
222 * (i.e. empty ptes). This will be the default behavior for shmem
223 * & hugetlbfs, so this flag only affects anonymous memory behavior
224 * when userfault write-protection mode is registered.
225 *
226 * UFFD_FEATURE_WP_ASYNC indicates that userfaultfd write-protection
227 * asynchronous mode is supported in which the write fault is
228 * automatically resolved and write-protection is un-set.
229 * It implies UFFD_FEATURE_WP_UNPOPULATED.
230 *
231 * UFFD_FEATURE_MOVE indicates that the kernel supports moving an
232 * existing page contents from userspace.
233 */
234#define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0)
235#define UFFD_FEATURE_EVENT_FORK (1<<1)
236#define UFFD_FEATURE_EVENT_REMAP (1<<2)
237#define UFFD_FEATURE_EVENT_REMOVE (1<<3)
238#define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4)
239#define UFFD_FEATURE_MISSING_SHMEM (1<<5)
240#define UFFD_FEATURE_EVENT_UNMAP (1<<6)
241#define UFFD_FEATURE_SIGBUS (1<<7)
242#define UFFD_FEATURE_THREAD_ID (1<<8)
243#define UFFD_FEATURE_MINOR_HUGETLBFS (1<<9)
244#define UFFD_FEATURE_MINOR_SHMEM (1<<10)
245#define UFFD_FEATURE_EXACT_ADDRESS (1<<11)
246#define UFFD_FEATURE_WP_HUGETLBFS_SHMEM (1<<12)
247#define UFFD_FEATURE_WP_UNPOPULATED (1<<13)
248#define UFFD_FEATURE_POISON (1<<14)
249#define UFFD_FEATURE_WP_ASYNC (1<<15)
250#define UFFD_FEATURE_MOVE (1<<16)
251 __u64 features;
252
253 __u64 ioctls;
254};
255
256struct uffdio_range {
257 __u64 start;
258 __u64 len;
259};
260
261struct uffdio_register {
262 struct uffdio_range range;
263#define UFFDIO_REGISTER_MODE_MISSING ((__u64)1<<0)
264#define UFFDIO_REGISTER_MODE_WP ((__u64)1<<1)
265#define UFFDIO_REGISTER_MODE_MINOR ((__u64)1<<2)
266 __u64 mode;
267
268 /*
269 * kernel answers which ioctl commands are available for the
270 * range, keep at the end as the last 8 bytes aren't read.
271 */
272 __u64 ioctls;
273};
274
275struct uffdio_copy {
276 __u64 dst;
277 __u64 src;
278 __u64 len;
279#define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0)
280 /*
281 * UFFDIO_COPY_MODE_WP will map the page write protected on
282 * the fly. UFFDIO_COPY_MODE_WP is available only if the
283 * write protected ioctl is implemented for the range
284 * according to the uffdio_register.ioctls.
285 */
286#define UFFDIO_COPY_MODE_WP ((__u64)1<<1)
287 __u64 mode;
288
289 /*
290 * "copy" is written by the ioctl and must be at the end: the
291 * copy_from_user will not read the last 8 bytes.
292 */
293 __s64 copy;
294};
295
296struct uffdio_zeropage {
297 struct uffdio_range range;
298#define UFFDIO_ZEROPAGE_MODE_DONTWAKE ((__u64)1<<0)
299 __u64 mode;
300
301 /*
302 * "zeropage" is written by the ioctl and must be at the end:
303 * the copy_from_user will not read the last 8 bytes.
304 */
305 __s64 zeropage;
306};
307
308struct uffdio_writeprotect {
309 struct uffdio_range range;
310/*
311 * UFFDIO_WRITEPROTECT_MODE_WP: set the flag to write protect a range,
312 * unset the flag to undo protection of a range which was previously
313 * write protected.
314 *
315 * UFFDIO_WRITEPROTECT_MODE_DONTWAKE: set the flag to avoid waking up
316 * any wait thread after the operation succeeds.
317 *
318 * NOTE: Write protecting a region (WP=1) is unrelated to page faults,
319 * therefore DONTWAKE flag is meaningless with WP=1. Removing write
320 * protection (WP=0) in response to a page fault wakes the faulting
321 * task unless DONTWAKE is set.
322 */
323#define UFFDIO_WRITEPROTECT_MODE_WP ((__u64)1<<0)
324#define UFFDIO_WRITEPROTECT_MODE_DONTWAKE ((__u64)1<<1)
325 __u64 mode;
326};
327
328struct uffdio_continue {
329 struct uffdio_range range;
330#define UFFDIO_CONTINUE_MODE_DONTWAKE ((__u64)1<<0)
331 /*
332 * UFFDIO_CONTINUE_MODE_WP will map the page write protected on
333 * the fly. UFFDIO_CONTINUE_MODE_WP is available only if the
334 * write protected ioctl is implemented for the range
335 * according to the uffdio_register.ioctls.
336 */
337#define UFFDIO_CONTINUE_MODE_WP ((__u64)1<<1)
338 __u64 mode;
339
340 /*
341 * Fields below here are written by the ioctl and must be at the end:
342 * the copy_from_user will not read past here.
343 */
344 __s64 mapped;
345};
346
347struct uffdio_poison {
348 struct uffdio_range range;
349#define UFFDIO_POISON_MODE_DONTWAKE ((__u64)1<<0)
350 __u64 mode;
351
352 /*
353 * Fields below here are written by the ioctl and must be at the end:
354 * the copy_from_user will not read past here.
355 */
356 __s64 updated;
357};
358
359struct uffdio_move {
360 __u64 dst;
361 __u64 src;
362 __u64 len;
363 /*
364 * Especially if used to atomically remove memory from the
365 * address space the wake on the dst range is not needed.
366 */
367#define UFFDIO_MOVE_MODE_DONTWAKE ((__u64)1<<0)
368#define UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES ((__u64)1<<1)
369 __u64 mode;
370 /*
371 * "move" is written by the ioctl and must be at the end: the
372 * copy_from_user will not read the last 8 bytes.
373 */
374 __s64 move;
375};
376
377/*
378 * Flags for the userfaultfd(2) system call itself.
379 */
380
381/*
382 * Create a userfaultfd that can handle page faults only in user mode.
383 */
384#define UFFD_USER_MODE_ONLY 1
385
386#endif /* _LINUX_USERFAULTFD_H */
387

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

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