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 /* 16 * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and 17 * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR. In 18 * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ 19 * means the userland is reading). 20 */ 21 #define UFFD_API ((__u64)0xAA) 22 #define UFFD_API_REGISTER_MODES (UFFDIO_REGISTER_MODE_MISSING | \ 23 UFFDIO_REGISTER_MODE_WP | \ 24 UFFDIO_REGISTER_MODE_MINOR) 25 #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP | \ 26 UFFD_FEATURE_EVENT_FORK | \ 27 UFFD_FEATURE_EVENT_REMAP | \ 28 UFFD_FEATURE_EVENT_REMOVE | \ 29 UFFD_FEATURE_EVENT_UNMAP | \ 30 UFFD_FEATURE_MISSING_HUGETLBFS | \ 31 UFFD_FEATURE_MISSING_SHMEM | \ 32 UFFD_FEATURE_SIGBUS | \ 33 UFFD_FEATURE_THREAD_ID | \ 34 UFFD_FEATURE_MINOR_HUGETLBFS | \ 35 UFFD_FEATURE_MINOR_SHMEM | \ 36 UFFD_FEATURE_EXACT_ADDRESS) 37 #define UFFD_API_IOCTLS \ 38 ((__u64)1 << _UFFDIO_REGISTER | \ 39 (__u64)1 << _UFFDIO_UNREGISTER | \ 40 (__u64)1 << _UFFDIO_API) 41 #define UFFD_API_RANGE_IOCTLS \ 42 ((__u64)1 << _UFFDIO_WAKE | \ 43 (__u64)1 << _UFFDIO_COPY | \ 44 (__u64)1 << _UFFDIO_ZEROPAGE | \ 45 (__u64)1 << _UFFDIO_WRITEPROTECT | \ 46 (__u64)1 << _UFFDIO_CONTINUE) 47 #define UFFD_API_RANGE_IOCTLS_BASIC \ 48 ((__u64)1 << _UFFDIO_WAKE | \ 49 (__u64)1 << _UFFDIO_COPY | \ 50 (__u64)1 << _UFFDIO_CONTINUE) 51 52 /* 53 * Valid ioctl command number range with this API is from 0x00 to 54 * 0x3F. UFFDIO_API is the fixed number, everything else can be 55 * changed by implementing a different UFFD_API. If sticking to the 56 * same UFFD_API more ioctl can be added and userland will be aware of 57 * which ioctl the running kernel implements through the ioctl command 58 * bitmask written by the UFFDIO_API. 59 */ 60 #define _UFFDIO_REGISTER (0x00) 61 #define _UFFDIO_UNREGISTER (0x01) 62 #define _UFFDIO_WAKE (0x02) 63 #define _UFFDIO_COPY (0x03) 64 #define _UFFDIO_ZEROPAGE (0x04) 65 #define _UFFDIO_WRITEPROTECT (0x06) 66 #define _UFFDIO_CONTINUE (0x07) 67 #define _UFFDIO_API (0x3F) 68 69 /* userfaultfd ioctl ids */ 70 #define UFFDIO 0xAA 71 #define UFFDIO_API _IOWR(UFFDIO, _UFFDIO_API, \ 72 struct uffdio_api) 73 #define UFFDIO_REGISTER _IOWR(UFFDIO, _UFFDIO_REGISTER, \ 74 struct uffdio_register) 75 #define UFFDIO_UNREGISTER _IOR(UFFDIO, _UFFDIO_UNREGISTER, \ 76 struct uffdio_range) 77 #define UFFDIO_WAKE _IOR(UFFDIO, _UFFDIO_WAKE, \ 78 struct uffdio_range) 79 #define UFFDIO_COPY _IOWR(UFFDIO, _UFFDIO_COPY, \ 80 struct uffdio_copy) 81 #define UFFDIO_ZEROPAGE _IOWR(UFFDIO, _UFFDIO_ZEROPAGE, \ 82 struct uffdio_zeropage) 83 #define UFFDIO_WRITEPROTECT _IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \ 84 struct uffdio_writeprotect) 85 #define UFFDIO_CONTINUE _IOWR(UFFDIO, _UFFDIO_CONTINUE, \ 86 struct uffdio_continue) 87 88 /* read() structure */ 89 struct uffd_msg { 90 __u8 event; 91 92 __u8 reserved1; 93 __u16 reserved2; 94 __u32 reserved3; 95 96 union { 97 struct { 98 __u64 flags; 99 __u64 address; 100 union { 101 __u32 ptid; 102 } feat; 103 } pagefault; 104 105 struct { 106 __u32 ufd; 107 } fork; 108 109 struct { 110 __u64 from; 111 __u64 to; 112 __u64 len; 113 } remap; 114 115 struct { 116 __u64 start; 117 __u64 end; 118 } remove; 119 120 struct { 121 /* unused reserved fields */ 122 __u64 reserved1; 123 __u64 reserved2; 124 __u64 reserved3; 125 } reserved; 126 } arg; 127 } __attribute__((packed)); 128 129 /* 130 * Start at 0x12 and not at 0 to be more strict against bugs. 131 */ 132 #define UFFD_EVENT_PAGEFAULT 0x12 133 #define UFFD_EVENT_FORK 0x13 134 #define UFFD_EVENT_REMAP 0x14 135 #define UFFD_EVENT_REMOVE 0x15 136 #define UFFD_EVENT_UNMAP 0x16 137 138 /* flags for UFFD_EVENT_PAGEFAULT */ 139 #define UFFD_PAGEFAULT_FLAG_WRITE (1<<0) /* If this was a write fault */ 140 #define UFFD_PAGEFAULT_FLAG_WP (1<<1) /* If reason is VM_UFFD_WP */ 141 #define UFFD_PAGEFAULT_FLAG_MINOR (1<<2) /* If reason is VM_UFFD_MINOR */ 142 143 struct uffdio_api { 144 /* userland asks for an API number and the features to enable */ 145 __u64 api; 146 /* 147 * Kernel answers below with the all available features for 148 * the API, this notifies userland of which events and/or 149 * which flags for each event are enabled in the current 150 * kernel. 151 * 152 * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE 153 * are to be considered implicitly always enabled in all kernels as 154 * long as the uffdio_api.api requested matches UFFD_API. 155 * 156 * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER 157 * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on 158 * hugetlbfs virtual memory ranges. Adding or not adding 159 * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has 160 * no real functional effect after UFFDIO_API returns, but 161 * it's only useful for an initial feature set probe at 162 * UFFDIO_API time. There are two ways to use it: 163 * 164 * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the 165 * uffdio_api.features before calling UFFDIO_API, an error 166 * will be returned by UFFDIO_API on a kernel without 167 * hugetlbfs missing support 168 * 169 * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in 170 * uffdio_api.features and instead it will be set by the 171 * kernel in the uffdio_api.features if the kernel supports 172 * it, so userland can later check if the feature flag is 173 * present in uffdio_api.features after UFFDIO_API 174 * succeeded. 175 * 176 * UFFD_FEATURE_MISSING_SHMEM works the same as 177 * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem 178 * (i.e. tmpfs and other shmem based APIs). 179 * 180 * UFFD_FEATURE_SIGBUS feature means no page-fault 181 * (UFFD_EVENT_PAGEFAULT) event will be delivered, instead 182 * a SIGBUS signal will be sent to the faulting process. 183 * 184 * UFFD_FEATURE_THREAD_ID pid of the page faulted task_struct will 185 * be returned, if feature is not requested 0 will be returned. 186 * 187 * UFFD_FEATURE_MINOR_HUGETLBFS indicates that minor faults 188 * can be intercepted (via REGISTER_MODE_MINOR) for 189 * hugetlbfs-backed pages. 190 * 191 * UFFD_FEATURE_MINOR_SHMEM indicates the same support as 192 * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead. 193 * 194 * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page 195 * faults would be provided and the offset within the page would not be 196 * masked. 197 */ 198 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) 199 #define UFFD_FEATURE_EVENT_FORK (1<<1) 200 #define UFFD_FEATURE_EVENT_REMAP (1<<2) 201 #define UFFD_FEATURE_EVENT_REMOVE (1<<3) 202 #define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4) 203 #define UFFD_FEATURE_MISSING_SHMEM (1<<5) 204 #define UFFD_FEATURE_EVENT_UNMAP (1<<6) 205 #define UFFD_FEATURE_SIGBUS (1<<7) 206 #define UFFD_FEATURE_THREAD_ID (1<<8) 207 #define UFFD_FEATURE_MINOR_HUGETLBFS (1<<9) 208 #define UFFD_FEATURE_MINOR_SHMEM (1<<10) 209 #define UFFD_FEATURE_EXACT_ADDRESS (1<<11) 210 __u64 features; 211 212 __u64 ioctls; 213 }; 214 215 struct uffdio_range { 216 __u64 start; 217 __u64 len; 218 }; 219 220 struct uffdio_register { 221 struct uffdio_range range; 222 #define UFFDIO_REGISTER_MODE_MISSING ((__u64)1<<0) 223 #define UFFDIO_REGISTER_MODE_WP ((__u64)1<<1) 224 #define UFFDIO_REGISTER_MODE_MINOR ((__u64)1<<2) 225 __u64 mode; 226 227 /* 228 * kernel answers which ioctl commands are available for the 229 * range, keep at the end as the last 8 bytes aren't read. 230 */ 231 __u64 ioctls; 232 }; 233 234 struct uffdio_copy { 235 __u64 dst; 236 __u64 src; 237 __u64 len; 238 #define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0) 239 /* 240 * UFFDIO_COPY_MODE_WP will map the page write protected on 241 * the fly. UFFDIO_COPY_MODE_WP is available only if the 242 * write protected ioctl is implemented for the range 243 * according to the uffdio_register.ioctls. 244 */ 245 #define UFFDIO_COPY_MODE_WP ((__u64)1<<1) 246 __u64 mode; 247 248 /* 249 * "copy" is written by the ioctl and must be at the end: the 250 * copy_from_user will not read the last 8 bytes. 251 */ 252 __s64 copy; 253 }; 254 255 struct uffdio_zeropage { 256 struct uffdio_range range; 257 #define UFFDIO_ZEROPAGE_MODE_DONTWAKE ((__u64)1<<0) 258 __u64 mode; 259 260 /* 261 * "zeropage" is written by the ioctl and must be at the end: 262 * the copy_from_user will not read the last 8 bytes. 263 */ 264 __s64 zeropage; 265 }; 266 267 struct uffdio_writeprotect { 268 struct uffdio_range range; 269 /* 270 * UFFDIO_WRITEPROTECT_MODE_WP: set the flag to write protect a range, 271 * unset the flag to undo protection of a range which was previously 272 * write protected. 273 * 274 * UFFDIO_WRITEPROTECT_MODE_DONTWAKE: set the flag to avoid waking up 275 * any wait thread after the operation succeeds. 276 * 277 * NOTE: Write protecting a region (WP=1) is unrelated to page faults, 278 * therefore DONTWAKE flag is meaningless with WP=1. Removing write 279 * protection (WP=0) in response to a page fault wakes the faulting 280 * task unless DONTWAKE is set. 281 */ 282 #define UFFDIO_WRITEPROTECT_MODE_WP ((__u64)1<<0) 283 #define UFFDIO_WRITEPROTECT_MODE_DONTWAKE ((__u64)1<<1) 284 __u64 mode; 285 }; 286 287 struct uffdio_continue { 288 struct uffdio_range range; 289 #define UFFDIO_CONTINUE_MODE_DONTWAKE ((__u64)1<<0) 290 __u64 mode; 291 292 /* 293 * Fields below here are written by the ioctl and must be at the end: 294 * the copy_from_user will not read past here. 295 */ 296 __s64 mapped; 297 }; 298 299 /* 300 * Flags for the userfaultfd(2) system call itself. 301 */ 302 303 /* 304 * Create a userfaultfd that can handle page faults only in user mode. 305 */ 306 #define UFFD_USER_MODE_ONLY 1 307 308 #endif /* _LINUX_USERFAULTFD_H */ 309