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 #define UFFD_API_IOCTLS \ 43 ((__u64)1 << _UFFDIO_REGISTER | \ 44 (__u64)1 << _UFFDIO_UNREGISTER | \ 45 (__u64)1 << _UFFDIO_API) 46 #define UFFD_API_RANGE_IOCTLS \ 47 ((__u64)1 << _UFFDIO_WAKE | \ 48 (__u64)1 << _UFFDIO_COPY | \ 49 (__u64)1 << _UFFDIO_ZEROPAGE | \ 50 (__u64)1 << _UFFDIO_WRITEPROTECT | \ 51 (__u64)1 << _UFFDIO_CONTINUE) 52 #define UFFD_API_RANGE_IOCTLS_BASIC \ 53 ((__u64)1 << _UFFDIO_WAKE | \ 54 (__u64)1 << _UFFDIO_COPY | \ 55 (__u64)1 << _UFFDIO_CONTINUE | \ 56 (__u64)1 << _UFFDIO_WRITEPROTECT) 57 58 /* 59 * Valid ioctl command number range with this API is from 0x00 to 60 * 0x3F. UFFDIO_API is the fixed number, everything else can be 61 * changed by implementing a different UFFD_API. If sticking to the 62 * same UFFD_API more ioctl can be added and userland will be aware of 63 * which ioctl the running kernel implements through the ioctl command 64 * bitmask written by the UFFDIO_API. 65 */ 66 #define _UFFDIO_REGISTER (0x00) 67 #define _UFFDIO_UNREGISTER (0x01) 68 #define _UFFDIO_WAKE (0x02) 69 #define _UFFDIO_COPY (0x03) 70 #define _UFFDIO_ZEROPAGE (0x04) 71 #define _UFFDIO_WRITEPROTECT (0x06) 72 #define _UFFDIO_CONTINUE (0x07) 73 #define _UFFDIO_API (0x3F) 74 75 /* userfaultfd ioctl ids */ 76 #define UFFDIO 0xAA 77 #define UFFDIO_API _IOWR(UFFDIO, _UFFDIO_API, \ 78 struct uffdio_api) 79 #define UFFDIO_REGISTER _IOWR(UFFDIO, _UFFDIO_REGISTER, \ 80 struct uffdio_register) 81 #define UFFDIO_UNREGISTER _IOR(UFFDIO, _UFFDIO_UNREGISTER, \ 82 struct uffdio_range) 83 #define UFFDIO_WAKE _IOR(UFFDIO, _UFFDIO_WAKE, \ 84 struct uffdio_range) 85 #define UFFDIO_COPY _IOWR(UFFDIO, _UFFDIO_COPY, \ 86 struct uffdio_copy) 87 #define UFFDIO_ZEROPAGE _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \ 88 struct uffdio_zeropage) 89 #define UFFDIO_WRITEPROTECT _IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \ 90 struct uffdio_writeprotect) 91 #define UFFDIO_CONTINUE _IOWR(UFFDIO, _UFFDIO_CONTINUE, \ 92 struct uffdio_continue) 93 94 /* read() structure */ 95 struct uffd_msg { 96 __u8 event; 97 98 __u8 reserved1; 99 __u16 reserved2; 100 __u32 reserved3; 101 102 union { 103 struct { 104 __u64 flags; 105 __u64 address; 106 union { 107 __u32 ptid; 108 } feat; 109 } pagefault; 110 111 struct { 112 __u32 ufd; 113 } fork; 114 115 struct { 116 __u64 from; 117 __u64 to; 118 __u64 len; 119 } remap; 120 121 struct { 122 __u64 start; 123 __u64 end; 124 } remove; 125 126 struct { 127 /* unused reserved fields */ 128 __u64 reserved1; 129 __u64 reserved2; 130 __u64 reserved3; 131 } reserved; 132 } arg; 133 } __attribute__((packed)); 134 135 /* 136 * Start at 0x12 and not at 0 to be more strict against bugs. 137 */ 138 #define UFFD_EVENT_PAGEFAULT 0x12 139 #define UFFD_EVENT_FORK 0x13 140 #define UFFD_EVENT_REMAP 0x14 141 #define UFFD_EVENT_REMOVE 0x15 142 #define UFFD_EVENT_UNMAP 0x16 143 144 /* flags for UFFD_EVENT_PAGEFAULT */ 145 #define UFFD_PAGEFAULT_FLAG_WRITE (1<<0) /* If this was a write fault */ 146 #define UFFD_PAGEFAULT_FLAG_WP (1<<1) /* If reason is VM_UFFD_WP */ 147 #define UFFD_PAGEFAULT_FLAG_MINOR (1<<2) /* If reason is VM_UFFD_MINOR */ 148 149 struct uffdio_api { 150 /* userland asks for an API number and the features to enable */ 151 __u64 api; 152 /* 153 * Kernel answers below with the all available features for 154 * the API, this notifies userland of which events and/or 155 * which flags for each event are enabled in the current 156 * kernel. 157 * 158 * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE 159 * are to be considered implicitly always enabled in all kernels as 160 * long as the uffdio_api.api requested matches UFFD_API. 161 * 162 * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER 163 * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on 164 * hugetlbfs virtual memory ranges. Adding or not adding 165 * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has 166 * no real functional effect after UFFDIO_API returns, but 167 * it's only useful for an initial feature set probe at 168 * UFFDIO_API time. There are two ways to use it: 169 * 170 * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the 171 * uffdio_api.features before calling UFFDIO_API, an error 172 * will be returned by UFFDIO_API on a kernel without 173 * hugetlbfs missing support 174 * 175 * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in 176 * uffdio_api.features and instead it will be set by the 177 * kernel in the uffdio_api.features if the kernel supports 178 * it, so userland can later check if the feature flag is 179 * present in uffdio_api.features after UFFDIO_API 180 * succeeded. 181 * 182 * UFFD_FEATURE_MISSING_SHMEM works the same as 183 * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem 184 * (i.e. tmpfs and other shmem based APIs). 185 * 186 * UFFD_FEATURE_SIGBUS feature means no page-fault 187 * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead 188 * a SIGBUS signal will be sent to the faulting process. 189 * 190 * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will 191 * be returned, if feature is not requested 0 will be returned. 192 * 193 * UFFD_FEATURE_MINOR_HUGETLBFS indicates that minor faults 194 * can be intercepted (via REGISTER_MODE_MINOR) for 195 * hugetlbfs-backed pages. 196 * 197 * UFFD_FEATURE_MINOR_SHMEM indicates the same support as 198 * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead. 199 * 200 * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page 201 * faults would be provided and the offset within the page would not be 202 * masked. 203 * 204 * UFFD_FEATURE_WP_HUGETLBFS_SHMEM indicates that userfaultfd 205 * write-protection mode is supported on both shmem and hugetlbfs. 206 */ 207 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) 208 #define UFFD_FEATURE_EVENT_FORK (1<<1) 209 #define UFFD_FEATURE_EVENT_REMAP (1<<2) 210 #define UFFD_FEATURE_EVENT_REMOVE (1<<3) 211 #define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4) 212 #define UFFD_FEATURE_MISSING_SHMEM (1<<5) 213 #define UFFD_FEATURE_EVENT_UNMAP (1<<6) 214 #define UFFD_FEATURE_SIGBUS (1<<7) 215 #define UFFD_FEATURE_THREAD_ID (1<<8) 216 #define UFFD_FEATURE_MINOR_HUGETLBFS (1<<9) 217 #define UFFD_FEATURE_MINOR_SHMEM (1<<10) 218 #define UFFD_FEATURE_EXACT_ADDRESS (1<<11) 219 #define UFFD_FEATURE_WP_HUGETLBFS_SHMEM (1<<12) 220 __u64 features; 221 222 __u64 ioctls; 223 }; 224 225 struct uffdio_range { 226 __u64 start; 227 __u64 len; 228 }; 229 230 struct uffdio_register { 231 struct uffdio_range range; 232 #define UFFDIO_REGISTER_MODE_MISSING ((__u64)1<<0) 233 #define UFFDIO_REGISTER_MODE_WP ((__u64)1<<1) 234 #define UFFDIO_REGISTER_MODE_MINOR ((__u64)1<<2) 235 __u64 mode; 236 237 /* 238 * kernel answers which ioctl commands are available for the 239 * range, keep at the end as the last 8 bytes aren't read. 240 */ 241 __u64 ioctls; 242 }; 243 244 struct uffdio_copy { 245 __u64 dst; 246 __u64 src; 247 __u64 len; 248 #define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0) 249 /* 250 * UFFDIO_COPY_MODE_WP will map the page write protected on 251 * the fly. UFFDIO_COPY_MODE_WP is available only if the 252 * write protected ioctl is implemented for the range 253 * according to the uffdio_register.ioctls. 254 */ 255 #define UFFDIO_COPY_MODE_WP ((__u64)1<<1) 256 __u64 mode; 257 258 /* 259 * "copy" is written by the ioctl and must be at the end: the 260 * copy_from_user will not read the last 8 bytes. 261 */ 262 __s64 copy; 263 }; 264 265 struct uffdio_zeropage { 266 struct uffdio_range range; 267 #define UFFDIO_ZEROPAGE_MODE_DONTWAKE ((__u64)1<<0) 268 __u64 mode; 269 270 /* 271 * "zeropage" is written by the ioctl and must be at the end: 272 * the copy_from_user will not read the last 8 bytes. 273 */ 274 __s64 zeropage; 275 }; 276 277 struct uffdio_writeprotect { 278 struct uffdio_range range; 279 /* 280 * UFFDIO_WRITEPROTECT_MODE_WP: set the flag to write protect a range, 281 * unset the flag to undo protection of a range which was previously 282 * write protected. 283 * 284 * UFFDIO_WRITEPROTECT_MODE_DONTWAKE: set the flag to avoid waking up 285 * any wait thread after the operation succeeds. 286 * 287 * NOTE: Write protecting a region (WP=1) is unrelated to page faults, 288 * therefore DONTWAKE flag is meaningless with WP=1. Removing write 289 * protection (WP=0) in response to a page fault wakes the faulting 290 * task unless DONTWAKE is set. 291 */ 292 #define UFFDIO_WRITEPROTECT_MODE_WP ((__u64)1<<0) 293 #define UFFDIO_WRITEPROTECT_MODE_DONTWAKE ((__u64)1<<1) 294 __u64 mode; 295 }; 296 297 struct uffdio_continue { 298 struct uffdio_range range; 299 #define UFFDIO_CONTINUE_MODE_DONTWAKE ((__u64)1<<0) 300 __u64 mode; 301 302 /* 303 * Fields below here are written by the ioctl and must be at the end: 304 * the copy_from_user will not read past here. 305 */ 306 __s64 mapped; 307 }; 308 309 /* 310 * Flags for the userfaultfd(2) system call itself. 311 */ 312 313 /* 314 * Create a userfaultfd that can handle page faults only in user mode. 315 */ 316 #define UFFD_USER_MODE_ONLY 1 317 318 #endif /* _LINUX_USERFAULTFD_H */ 319