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 */ 334