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