1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * include/linux/userfaultfd_k.h 4 * 5 * Copyright (C) 2015 Red Hat, Inc. 6 * 7 */ 8 9 #ifndef _LINUX_USERFAULTFD_K_H 10 #define _LINUX_USERFAULTFD_K_H 11 12 #ifdef CONFIG_USERFAULTFD 13 14 #include <linux/userfaultfd.h> /* linux/include/uapi/linux/userfaultfd.h */ 15 16 #include <linux/fcntl.h> 17 #include <linux/mm.h> 18 #include <linux/swap.h> 19 #include <linux/swapops.h> 20 #include <asm-generic/pgtable_uffd.h> 21 #include <linux/hugetlb_inline.h> 22 23 /* The set of all possible UFFD-related VM flags. */ 24 #define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR) 25 26 /* 27 * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining 28 * new flags, since they might collide with O_* ones. We want 29 * to re-use O_* flags that couldn't possibly have a meaning 30 * from userfaultfd, in order to leave a free define-space for 31 * shared O_* flags. 32 */ 33 #define UFFD_CLOEXEC O_CLOEXEC 34 #define UFFD_NONBLOCK O_NONBLOCK 35 36 #define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK) 37 #define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS) 38 39 /* 40 * Start with fault_pending_wqh and fault_wqh so they're more likely 41 * to be in the same cacheline. 42 * 43 * Locking order: 44 * fd_wqh.lock 45 * fault_pending_wqh.lock 46 * fault_wqh.lock 47 * event_wqh.lock 48 * 49 * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, 50 * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's 51 * also taken in IRQ context. 52 */ 53 struct userfaultfd_ctx { 54 /* waitqueue head for the pending (i.e. not read) userfaults */ 55 wait_queue_head_t fault_pending_wqh; 56 /* waitqueue head for the userfaults */ 57 wait_queue_head_t fault_wqh; 58 /* waitqueue head for the pseudo fd to wakeup poll/read */ 59 wait_queue_head_t fd_wqh; 60 /* waitqueue head for events */ 61 wait_queue_head_t event_wqh; 62 /* a refile sequence protected by fault_pending_wqh lock */ 63 seqcount_spinlock_t refile_seq; 64 /* pseudo fd refcounting */ 65 refcount_t refcount; 66 /* userfaultfd syscall flags */ 67 unsigned int flags; 68 /* features requested from the userspace */ 69 unsigned int features; 70 /* released */ 71 bool released; 72 /* 73 * Prevents userfaultfd operations (fill/move/wp) from happening while 74 * some non-cooperative event(s) is taking place. Increments are done 75 * in write-mode. Whereas, userfaultfd operations, which includes 76 * reading mmap_changing, is done under read-mode. 77 */ 78 struct rw_semaphore map_changing_lock; 79 /* memory mappings are changing because of non-cooperative event */ 80 atomic_t mmap_changing; 81 /* mm with one ore more vmas attached to this userfaultfd_ctx */ 82 struct mm_struct *mm; 83 }; 84 85 extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); 86 87 /* A combined operation mode + behavior flags. */ 88 typedef unsigned int __bitwise uffd_flags_t; 89 90 /* Mutually exclusive modes of operation. */ 91 enum mfill_atomic_mode { 92 MFILL_ATOMIC_COPY, 93 MFILL_ATOMIC_ZEROPAGE, 94 MFILL_ATOMIC_CONTINUE, 95 MFILL_ATOMIC_POISON, 96 NR_MFILL_ATOMIC_MODES, 97 }; 98 99 #define MFILL_ATOMIC_MODE_BITS (const_ilog2(NR_MFILL_ATOMIC_MODES - 1) + 1) 100 #define MFILL_ATOMIC_BIT(nr) BIT(MFILL_ATOMIC_MODE_BITS + (nr)) 101 #define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr)) 102 #define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1)) 103 104 static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected) 105 { 106 return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected); 107 } 108 109 static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode) 110 { 111 flags &= ~MFILL_ATOMIC_MODE_MASK; 112 return flags | ((__force uffd_flags_t) mode); 113 } 114 115 /* Flags controlling behavior. These behavior changes are mode-independent. */ 116 #define MFILL_ATOMIC_WP MFILL_ATOMIC_FLAG(0) 117 118 extern int mfill_atomic_install_pte(pmd_t *dst_pmd, 119 struct vm_area_struct *dst_vma, 120 unsigned long dst_addr, struct page *page, 121 bool newly_allocated, uffd_flags_t flags); 122 123 extern ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned long dst_start, 124 unsigned long src_start, unsigned long len, 125 uffd_flags_t flags); 126 extern ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx, 127 unsigned long dst_start, 128 unsigned long len); 129 extern ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned long dst_start, 130 unsigned long len, uffd_flags_t flags); 131 extern ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned long start, 132 unsigned long len, uffd_flags_t flags); 133 extern int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long start, 134 unsigned long len, bool enable_wp); 135 extern long uffd_wp_range(struct vm_area_struct *vma, 136 unsigned long start, unsigned long len, bool enable_wp); 137 138 /* move_pages */ 139 void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2); 140 void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2); 141 ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, 142 unsigned long src_start, unsigned long len, __u64 flags); 143 int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval, 144 struct vm_area_struct *dst_vma, 145 struct vm_area_struct *src_vma, 146 unsigned long dst_addr, unsigned long src_addr); 147 148 /* mm helpers */ 149 static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, 150 struct vm_userfaultfd_ctx vm_ctx) 151 { 152 return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx; 153 } 154 155 /* 156 * Never enable huge pmd sharing on some uffd registered vmas: 157 * 158 * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry. 159 * 160 * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for 161 * VMAs which share huge pmds. (If you have two mappings to the same 162 * underlying pages, and fault in the non-UFFD-registered one with a write, 163 * with huge pmd sharing this would *also* setup the second UFFD-registered 164 * mapping, and we'd not get minor faults.) 165 */ 166 static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma) 167 { 168 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR); 169 } 170 171 /* 172 * Don't do fault around for either WP or MINOR registered uffd range. For 173 * MINOR registered range, fault around will be a total disaster and ptes can 174 * be installed without notifications; for WP it should mostly be fine as long 175 * as the fault around checks for pte_none() before the installation, however 176 * to be super safe we just forbid it. 177 */ 178 static inline bool uffd_disable_fault_around(struct vm_area_struct *vma) 179 { 180 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR); 181 } 182 183 static inline bool userfaultfd_missing(struct vm_area_struct *vma) 184 { 185 return vma->vm_flags & VM_UFFD_MISSING; 186 } 187 188 static inline bool userfaultfd_wp(struct vm_area_struct *vma) 189 { 190 return vma->vm_flags & VM_UFFD_WP; 191 } 192 193 static inline bool userfaultfd_minor(struct vm_area_struct *vma) 194 { 195 return vma->vm_flags & VM_UFFD_MINOR; 196 } 197 198 static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma, 199 pte_t pte) 200 { 201 return userfaultfd_wp(vma) && pte_uffd_wp(pte); 202 } 203 204 static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma, 205 pmd_t pmd) 206 { 207 return userfaultfd_wp(vma) && pmd_uffd_wp(pmd); 208 } 209 210 static inline bool userfaultfd_armed(struct vm_area_struct *vma) 211 { 212 return vma->vm_flags & __VM_UFFD_FLAGS; 213 } 214 215 static inline bool vma_can_userfault(struct vm_area_struct *vma, 216 unsigned long vm_flags, 217 bool wp_async) 218 { 219 vm_flags &= __VM_UFFD_FLAGS; 220 221 if ((vm_flags & VM_UFFD_MINOR) && 222 (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma))) 223 return false; 224 225 /* 226 * If wp async enabled, and WP is the only mode enabled, allow any 227 * memory type. 228 */ 229 if (wp_async && (vm_flags == VM_UFFD_WP)) 230 return true; 231 232 #ifndef CONFIG_PTE_MARKER_UFFD_WP 233 /* 234 * If user requested uffd-wp but not enabled pte markers for 235 * uffd-wp, then shmem & hugetlbfs are not supported but only 236 * anonymous. 237 */ 238 if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma)) 239 return false; 240 #endif 241 242 /* By default, allow any of anon|shmem|hugetlb */ 243 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || 244 vma_is_shmem(vma); 245 } 246 247 extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *); 248 extern void dup_userfaultfd_complete(struct list_head *); 249 250 extern void mremap_userfaultfd_prep(struct vm_area_struct *, 251 struct vm_userfaultfd_ctx *); 252 extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *, 253 unsigned long from, unsigned long to, 254 unsigned long len); 255 256 extern bool userfaultfd_remove(struct vm_area_struct *vma, 257 unsigned long start, 258 unsigned long end); 259 260 extern int userfaultfd_unmap_prep(struct vm_area_struct *vma, 261 unsigned long start, unsigned long end, struct list_head *uf); 262 extern void userfaultfd_unmap_complete(struct mm_struct *mm, 263 struct list_head *uf); 264 extern bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma); 265 extern bool userfaultfd_wp_async(struct vm_area_struct *vma); 266 267 #else /* CONFIG_USERFAULTFD */ 268 269 /* mm helpers */ 270 static inline vm_fault_t handle_userfault(struct vm_fault *vmf, 271 unsigned long reason) 272 { 273 return VM_FAULT_SIGBUS; 274 } 275 276 static inline long uffd_wp_range(struct vm_area_struct *vma, 277 unsigned long start, unsigned long len, 278 bool enable_wp) 279 { 280 return false; 281 } 282 283 static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, 284 struct vm_userfaultfd_ctx vm_ctx) 285 { 286 return true; 287 } 288 289 static inline bool userfaultfd_missing(struct vm_area_struct *vma) 290 { 291 return false; 292 } 293 294 static inline bool userfaultfd_wp(struct vm_area_struct *vma) 295 { 296 return false; 297 } 298 299 static inline bool userfaultfd_minor(struct vm_area_struct *vma) 300 { 301 return false; 302 } 303 304 static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma, 305 pte_t pte) 306 { 307 return false; 308 } 309 310 static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma, 311 pmd_t pmd) 312 { 313 return false; 314 } 315 316 317 static inline bool userfaultfd_armed(struct vm_area_struct *vma) 318 { 319 return false; 320 } 321 322 static inline int dup_userfaultfd(struct vm_area_struct *vma, 323 struct list_head *l) 324 { 325 return 0; 326 } 327 328 static inline void dup_userfaultfd_complete(struct list_head *l) 329 { 330 } 331 332 static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma, 333 struct vm_userfaultfd_ctx *ctx) 334 { 335 } 336 337 static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx, 338 unsigned long from, 339 unsigned long to, 340 unsigned long len) 341 { 342 } 343 344 static inline bool userfaultfd_remove(struct vm_area_struct *vma, 345 unsigned long start, 346 unsigned long end) 347 { 348 return true; 349 } 350 351 static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma, 352 unsigned long start, unsigned long end, 353 struct list_head *uf) 354 { 355 return 0; 356 } 357 358 static inline void userfaultfd_unmap_complete(struct mm_struct *mm, 359 struct list_head *uf) 360 { 361 } 362 363 static inline bool uffd_disable_fault_around(struct vm_area_struct *vma) 364 { 365 return false; 366 } 367 368 static inline bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma) 369 { 370 return false; 371 } 372 373 static inline bool userfaultfd_wp_async(struct vm_area_struct *vma) 374 { 375 return false; 376 } 377 378 #endif /* CONFIG_USERFAULTFD */ 379 380 static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma) 381 { 382 /* Only wr-protect mode uses pte markers */ 383 if (!userfaultfd_wp(vma)) 384 return false; 385 386 /* File-based uffd-wp always need markers */ 387 if (!vma_is_anonymous(vma)) 388 return true; 389 390 /* 391 * Anonymous uffd-wp only needs the markers if WP_UNPOPULATED 392 * enabled (to apply markers on zero pages). 393 */ 394 return userfaultfd_wp_unpopulated(vma); 395 } 396 397 static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry) 398 { 399 #ifdef CONFIG_PTE_MARKER_UFFD_WP 400 return is_pte_marker_entry(entry) && 401 (pte_marker_get(entry) & PTE_MARKER_UFFD_WP); 402 #else 403 return false; 404 #endif 405 } 406 407 static inline bool pte_marker_uffd_wp(pte_t pte) 408 { 409 #ifdef CONFIG_PTE_MARKER_UFFD_WP 410 swp_entry_t entry; 411 412 if (!is_swap_pte(pte)) 413 return false; 414 415 entry = pte_to_swp_entry(pte); 416 417 return pte_marker_entry_uffd_wp(entry); 418 #else 419 return false; 420 #endif 421 } 422 423 /* 424 * Returns true if this is a swap pte and was uffd-wp wr-protected in either 425 * forms (pte marker or a normal swap pte), false otherwise. 426 */ 427 static inline bool pte_swp_uffd_wp_any(pte_t pte) 428 { 429 #ifdef CONFIG_PTE_MARKER_UFFD_WP 430 if (!is_swap_pte(pte)) 431 return false; 432 433 if (pte_swp_uffd_wp(pte)) 434 return true; 435 436 if (pte_marker_uffd_wp(pte)) 437 return true; 438 #endif 439 return false; 440 } 441 442 #endif /* _LINUX_USERFAULTFD_K_H */ 443