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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/leafops.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#define __VMA_UFFD_FLAGS mk_vma_flags(VMA_UFFD_MISSING_BIT, VMA_UFFD_WP_BIT, \
27 VMA_UFFD_MINOR_BIT)
28
29/*
30 * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
31 * new flags, since they might collide with O_* ones. We want
32 * to re-use O_* flags that couldn't possibly have a meaning
33 * from userfaultfd, in order to leave a free define-space for
34 * shared O_* flags.
35 */
36#define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
37
38/*
39 * Start with fault_pending_wqh and fault_wqh so they're more likely
40 * to be in the same cacheline.
41 *
42 * Locking order:
43 * fd_wqh.lock
44 * fault_pending_wqh.lock
45 * fault_wqh.lock
46 * event_wqh.lock
47 *
48 * To avoid deadlocks, IRQs must be disabled when taking any of the above locks,
49 * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's
50 * also taken in IRQ context.
51 */
52struct userfaultfd_ctx {
53 /* waitqueue head for the pending (i.e. not read) userfaults */
54 wait_queue_head_t fault_pending_wqh;
55 /* waitqueue head for the userfaults */
56 wait_queue_head_t fault_wqh;
57 /* waitqueue head for the pseudo fd to wakeup poll/read */
58 wait_queue_head_t fd_wqh;
59 /* waitqueue head for events */
60 wait_queue_head_t event_wqh;
61 /* a refile sequence protected by fault_pending_wqh lock */
62 seqcount_spinlock_t refile_seq;
63 /* pseudo fd refcounting */
64 refcount_t refcount;
65 /* userfaultfd syscall flags */
66 unsigned int flags;
67 /* features requested from the userspace */
68 unsigned int features;
69 /* released */
70 bool released;
71 /*
72 * Prevents userfaultfd operations (fill/move/wp) from happening while
73 * some non-cooperative event(s) is taking place. Increments are done
74 * in write-mode. Whereas, userfaultfd operations, which includes
75 * reading mmap_changing, is done under read-mode.
76 */
77 struct rw_semaphore map_changing_lock;
78 /* memory mappings are changing because of non-cooperative event */
79 atomic_t mmap_changing;
80 /* mm with one ore more vmas attached to this userfaultfd_ctx */
81 struct mm_struct *mm;
82};
83
84extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
85
86/* VMA userfaultfd operations */
87struct vm_uffd_ops {
88 /* Checks if a VMA can support userfaultfd */
89 bool (*can_userfault)(struct vm_area_struct *vma, vm_flags_t vm_flags);
90 /*
91 * Called to resolve UFFDIO_CONTINUE request.
92 * Should return the folio found at pgoff in the VMA's pagecache if it
93 * exists or ERR_PTR otherwise.
94 * The returned folio is locked and with reference held.
95 */
96 struct folio *(*get_folio_noalloc)(struct inode *inode, pgoff_t pgoff);
97 /*
98 * Called during resolution of UFFDIO_COPY request.
99 * Should allocate and return a folio or NULL if allocation fails.
100 */
101 struct folio *(*alloc_folio)(struct vm_area_struct *vma,
102 unsigned long addr);
103 /*
104 * Called during resolution of UFFDIO_COPY request.
105 * Should only be called with a folio returned by alloc_folio() above.
106 * The folio will be set to locked.
107 * Returns 0 on success, error code on failure.
108 */
109 int (*filemap_add)(struct folio *folio, struct vm_area_struct *vma,
110 unsigned long addr);
111 /*
112 * Called during resolution of UFFDIO_COPY request on the error
113 * handling path.
114 * Should revert the operation of ->filemap_add().
115 */
116 void (*filemap_remove)(struct folio *folio, struct vm_area_struct *vma);
117};
118
119/* A combined operation mode + behavior flags. */
120typedef unsigned int __bitwise uffd_flags_t;
121
122/* Mutually exclusive modes of operation. */
123enum mfill_atomic_mode {
124 MFILL_ATOMIC_COPY,
125 MFILL_ATOMIC_ZEROPAGE,
126 MFILL_ATOMIC_CONTINUE,
127 MFILL_ATOMIC_POISON,
128 NR_MFILL_ATOMIC_MODES,
129};
130
131#define MFILL_ATOMIC_MODE_BITS (const_ilog2(NR_MFILL_ATOMIC_MODES - 1) + 1)
132#define MFILL_ATOMIC_BIT(nr) BIT(MFILL_ATOMIC_MODE_BITS + (nr))
133#define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr))
134#define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1))
135
136static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
137{
138 return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected);
139}
140
141static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode)
142{
143 flags &= ~MFILL_ATOMIC_MODE_MASK;
144 return flags | ((__force uffd_flags_t) mode);
145}
146
147/* Flags controlling behavior. These behavior changes are mode-independent. */
148#define MFILL_ATOMIC_WP MFILL_ATOMIC_FLAG(0)
149
150extern ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned long dst_start,
151 unsigned long src_start, unsigned long len,
152 uffd_flags_t flags);
153extern ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx,
154 unsigned long dst_start,
155 unsigned long len);
156extern ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned long dst_start,
157 unsigned long len, uffd_flags_t flags);
158extern ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned long start,
159 unsigned long len, uffd_flags_t flags);
160extern int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long start,
161 unsigned long len, bool enable_wp);
162extern long uffd_wp_range(struct vm_area_struct *vma,
163 unsigned long start, unsigned long len, bool enable_wp);
164
165/* move_pages */
166void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2);
167void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2);
168ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
169 unsigned long src_start, unsigned long len, __u64 flags);
170int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval,
171 struct vm_area_struct *dst_vma,
172 struct vm_area_struct *src_vma,
173 unsigned long dst_addr, unsigned long src_addr);
174
175/* mm helpers */
176static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
177 struct vm_userfaultfd_ctx vm_ctx)
178{
179 return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx;
180}
181
182/*
183 * Never enable huge pmd sharing on some uffd registered vmas:
184 *
185 * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry.
186 *
187 * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for
188 * VMAs which share huge pmds. (If you have two mappings to the same
189 * underlying pages, and fault in the non-UFFD-registered one with a write,
190 * with huge pmd sharing this would *also* setup the second UFFD-registered
191 * mapping, and we'd not get minor faults.)
192 */
193static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma)
194{
195 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
196}
197
198/*
199 * Don't do fault around for either WP or MINOR registered uffd range. For
200 * MINOR registered range, fault around will be a total disaster and ptes can
201 * be installed without notifications; for WP it should mostly be fine as long
202 * as the fault around checks for pte_none() before the installation, however
203 * to be super safe we just forbid it.
204 */
205static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
206{
207 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
208}
209
210static inline bool userfaultfd_missing(struct vm_area_struct *vma)
211{
212 return vma->vm_flags & VM_UFFD_MISSING;
213}
214
215static inline bool userfaultfd_wp(struct vm_area_struct *vma)
216{
217 return vma->vm_flags & VM_UFFD_WP;
218}
219
220static inline bool userfaultfd_minor(struct vm_area_struct *vma)
221{
222 return vma->vm_flags & VM_UFFD_MINOR;
223}
224
225static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
226 pte_t pte)
227{
228 return userfaultfd_wp(vma) && pte_uffd_wp(pte);
229}
230
231static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
232 pmd_t pmd)
233{
234 return userfaultfd_wp(vma) && pmd_uffd_wp(pmd);
235}
236
237static inline bool userfaultfd_armed(struct vm_area_struct *vma)
238{
239 return vma->vm_flags & __VM_UFFD_FLAGS;
240}
241
242bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags,
243 bool wp_async);
244
245static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
246{
247 struct userfaultfd_ctx *uffd_ctx = vma->vm_userfaultfd_ctx.ctx;
248
249 return uffd_ctx && (uffd_ctx->features & UFFD_FEATURE_EVENT_REMAP) == 0;
250}
251
252extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
253extern void dup_userfaultfd_complete(struct list_head *);
254void dup_userfaultfd_fail(struct list_head *);
255
256extern void mremap_userfaultfd_prep(struct vm_area_struct *,
257 struct vm_userfaultfd_ctx *);
258extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *,
259 unsigned long from, unsigned long to,
260 unsigned long len);
261void mremap_userfaultfd_fail(struct vm_userfaultfd_ctx *);
262
263extern bool userfaultfd_remove(struct vm_area_struct *vma,
264 unsigned long start,
265 unsigned long end);
266
267extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
268 unsigned long start, unsigned long end, struct list_head *uf);
269extern void userfaultfd_unmap_complete(struct mm_struct *mm,
270 struct list_head *uf);
271extern bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma);
272extern bool userfaultfd_wp_async(struct vm_area_struct *vma);
273
274void userfaultfd_reset_ctx(struct vm_area_struct *vma);
275
276struct vm_area_struct *userfaultfd_clear_vma(struct vma_iterator *vmi,
277 struct vm_area_struct *prev,
278 struct vm_area_struct *vma,
279 unsigned long start,
280 unsigned long end);
281
282int userfaultfd_register_range(struct userfaultfd_ctx *ctx,
283 struct vm_area_struct *vma,
284 vm_flags_t vm_flags,
285 unsigned long start, unsigned long end,
286 bool wp_async);
287
288void userfaultfd_release_new(struct userfaultfd_ctx *ctx);
289
290void userfaultfd_release_all(struct mm_struct *mm,
291 struct userfaultfd_ctx *ctx);
292
293static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
294{
295 /* Only wr-protect mode uses pte markers */
296 if (!userfaultfd_wp(vma))
297 return false;
298
299 /* File-based uffd-wp always need markers */
300 if (!vma_is_anonymous(vma))
301 return true;
302
303 /*
304 * Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
305 * enabled (to apply markers on zero pages).
306 */
307 return userfaultfd_wp_unpopulated(vma);
308}
309
310/*
311 * Returns true if this is a swap pte and was uffd-wp wr-protected in either
312 * forms (pte marker or a normal swap pte), false otherwise.
313 */
314static inline bool pte_swp_uffd_wp_any(pte_t pte)
315{
316 if (!uffd_supports_wp_marker())
317 return false;
318
319 if (pte_present(pte))
320 return false;
321
322 if (pte_swp_uffd_wp(pte))
323 return true;
324
325 if (pte_is_uffd_wp_marker(pte))
326 return true;
327
328 return false;
329}
330#else /* CONFIG_USERFAULTFD */
331
332/* mm helpers */
333static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
334 unsigned long reason)
335{
336 return VM_FAULT_SIGBUS;
337}
338
339static inline long uffd_wp_range(struct vm_area_struct *vma,
340 unsigned long start, unsigned long len,
341 bool enable_wp)
342{
343 return false;
344}
345
346static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
347 struct vm_userfaultfd_ctx vm_ctx)
348{
349 return true;
350}
351
352static inline bool userfaultfd_missing(struct vm_area_struct *vma)
353{
354 return false;
355}
356
357static inline bool userfaultfd_wp(struct vm_area_struct *vma)
358{
359 return false;
360}
361
362static inline bool userfaultfd_minor(struct vm_area_struct *vma)
363{
364 return false;
365}
366
367static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
368 pte_t pte)
369{
370 return false;
371}
372
373static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
374 pmd_t pmd)
375{
376 return false;
377}
378
379
380static inline bool userfaultfd_armed(struct vm_area_struct *vma)
381{
382 return false;
383}
384
385static inline int dup_userfaultfd(struct vm_area_struct *vma,
386 struct list_head *l)
387{
388 return 0;
389}
390
391static inline void dup_userfaultfd_complete(struct list_head *l)
392{
393}
394
395static inline void dup_userfaultfd_fail(struct list_head *l)
396{
397}
398
399static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma,
400 struct vm_userfaultfd_ctx *ctx)
401{
402}
403
404static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx,
405 unsigned long from,
406 unsigned long to,
407 unsigned long len)
408{
409}
410
411static inline void mremap_userfaultfd_fail(struct vm_userfaultfd_ctx *ctx)
412{
413}
414
415static inline bool userfaultfd_remove(struct vm_area_struct *vma,
416 unsigned long start,
417 unsigned long end)
418{
419 return true;
420}
421
422static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
423 unsigned long start, unsigned long end,
424 struct list_head *uf)
425{
426 return 0;
427}
428
429static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
430 struct list_head *uf)
431{
432}
433
434static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
435{
436 return false;
437}
438
439static inline bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma)
440{
441 return false;
442}
443
444static inline bool userfaultfd_wp_async(struct vm_area_struct *vma)
445{
446 return false;
447}
448
449static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
450{
451 return false;
452}
453
454static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
455{
456 return false;
457}
458
459/*
460 * Returns true if this is a swap pte and was uffd-wp wr-protected in either
461 * forms (pte marker or a normal swap pte), false otherwise.
462 */
463static inline bool pte_swp_uffd_wp_any(pte_t pte)
464{
465 return false;
466}
467#endif /* CONFIG_USERFAULTFD */
468#endif /* _LINUX_USERFAULTFD_K_H */