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_DROPPABLE)
222 return false;
223
224 if ((vm_flags & VM_UFFD_MINOR) &&
225 (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
226 return false;
227
228 /*
229 * If wp async enabled, and WP is the only mode enabled, allow any
230 * memory type.
231 */
232 if (wp_async && (vm_flags == VM_UFFD_WP))
233 return true;
234
235 #ifndef CONFIG_PTE_MARKER_UFFD_WP
236 /*
237 * If user requested uffd-wp but not enabled pte markers for
238 * uffd-wp, then shmem & hugetlbfs are not supported but only
239 * anonymous.
240 */
241 if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
242 return false;
243 #endif
244
245 /* By default, allow any of anon|shmem|hugetlb */
246 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
247 vma_is_shmem(vma);
248 }
249
250 extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
251 extern void dup_userfaultfd_complete(struct list_head *);
252
253 extern void mremap_userfaultfd_prep(struct vm_area_struct *,
254 struct vm_userfaultfd_ctx *);
255 extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *,
256 unsigned long from, unsigned long to,
257 unsigned long len);
258
259 extern bool userfaultfd_remove(struct vm_area_struct *vma,
260 unsigned long start,
261 unsigned long end);
262
263 extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
264 unsigned long start, unsigned long end, struct list_head *uf);
265 extern void userfaultfd_unmap_complete(struct mm_struct *mm,
266 struct list_head *uf);
267 extern bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma);
268 extern bool userfaultfd_wp_async(struct vm_area_struct *vma);
269
270 #else /* CONFIG_USERFAULTFD */
271
272 /* mm helpers */
273 static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
274 unsigned long reason)
275 {
276 return VM_FAULT_SIGBUS;
277 }
278
279 static inline long uffd_wp_range(struct vm_area_struct *vma,
280 unsigned long start, unsigned long len,
281 bool enable_wp)
282 {
283 return false;
284 }
285
286 static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
287 struct vm_userfaultfd_ctx vm_ctx)
288 {
289 return true;
290 }
291
292 static inline bool userfaultfd_missing(struct vm_area_struct *vma)
293 {
294 return false;
295 }
296
297 static inline bool userfaultfd_wp(struct vm_area_struct *vma)
298 {
299 return false;
300 }
301
302 static inline bool userfaultfd_minor(struct vm_area_struct *vma)
303 {
304 return false;
305 }
306
307 static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
308 pte_t pte)
309 {
310 return false;
311 }
312
313 static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
314 pmd_t pmd)
315 {
316 return false;
317 }
318
319
320 static inline bool userfaultfd_armed(struct vm_area_struct *vma)
321 {
322 return false;
323 }
324
325 static inline int dup_userfaultfd(struct vm_area_struct *vma,
326 struct list_head *l)
327 {
328 return 0;
329 }
330
331 static inline void dup_userfaultfd_complete(struct list_head *l)
332 {
333 }
334
335 static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma,
336 struct vm_userfaultfd_ctx *ctx)
337 {
338 }
339
340 static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx,
341 unsigned long from,
342 unsigned long to,
343 unsigned long len)
344 {
345 }
346
347 static inline bool userfaultfd_remove(struct vm_area_struct *vma,
348 unsigned long start,
349 unsigned long end)
350 {
351 return true;
352 }
353
354 static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
355 unsigned long start, unsigned long end,
356 struct list_head *uf)
357 {
358 return 0;
359 }
360
361 static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
362 struct list_head *uf)
363 {
364 }
365
366 static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
367 {
368 return false;
369 }
370
371 static inline bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma)
372 {
373 return false;
374 }
375
376 static inline bool userfaultfd_wp_async(struct vm_area_struct *vma)
377 {
378 return false;
379 }
380
381 #endif /* CONFIG_USERFAULTFD */
382
383 static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
384 {
385 /* Only wr-protect mode uses pte markers */
386 if (!userfaultfd_wp(vma))
387 return false;
388
389 /* File-based uffd-wp always need markers */
390 if (!vma_is_anonymous(vma))
391 return true;
392
393 /*
394 * Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
395 * enabled (to apply markers on zero pages).
396 */
397 return userfaultfd_wp_unpopulated(vma);
398 }
399
400 static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
401 {
402 #ifdef CONFIG_PTE_MARKER_UFFD_WP
403 return is_pte_marker_entry(entry) &&
404 (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
405 #else
406 return false;
407 #endif
408 }
409
410 static inline bool pte_marker_uffd_wp(pte_t pte)
411 {
412 #ifdef CONFIG_PTE_MARKER_UFFD_WP
413 swp_entry_t entry;
414
415 if (!is_swap_pte(pte))
416 return false;
417
418 entry = pte_to_swp_entry(pte);
419
420 return pte_marker_entry_uffd_wp(entry);
421 #else
422 return false;
423 #endif
424 }
425
426 /*
427 * Returns true if this is a swap pte and was uffd-wp wr-protected in either
428 * forms (pte marker or a normal swap pte), false otherwise.
429 */
430 static inline bool pte_swp_uffd_wp_any(pte_t pte)
431 {
432 #ifdef CONFIG_PTE_MARKER_UFFD_WP
433 if (!is_swap_pte(pte))
434 return false;
435
436 if (pte_swp_uffd_wp(pte))
437 return true;
438
439 if (pte_marker_uffd_wp(pte))
440 return true;
441 #endif
442 return false;
443 }
444
445 #endif /* _LINUX_USERFAULTFD_K_H */
446
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