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