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
39extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
40
41/* A combined operation mode + behavior flags. */
42typedef unsigned int __bitwise uffd_flags_t;
43
44/* Mutually exclusive modes of operation. */
45enum mfill_atomic_mode {
46 MFILL_ATOMIC_COPY,
47 MFILL_ATOMIC_ZEROPAGE,
48 MFILL_ATOMIC_CONTINUE,
49 MFILL_ATOMIC_POISON,
50 NR_MFILL_ATOMIC_MODES,
51};
52
53#define MFILL_ATOMIC_MODE_BITS (const_ilog2(NR_MFILL_ATOMIC_MODES - 1) + 1)
54#define MFILL_ATOMIC_BIT(nr) BIT(MFILL_ATOMIC_MODE_BITS + (nr))
55#define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr))
56#define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1))
57
58static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
59{
60 return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected);
61}
62
63static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode)
64{
65 flags &= ~MFILL_ATOMIC_MODE_MASK;
66 return flags | ((__force uffd_flags_t) mode);
67}
68
69/* Flags controlling behavior. These behavior changes are mode-independent. */
70#define MFILL_ATOMIC_WP MFILL_ATOMIC_FLAG(0)
71
72extern int mfill_atomic_install_pte(pmd_t *dst_pmd,
73 struct vm_area_struct *dst_vma,
74 unsigned long dst_addr, struct page *page,
75 bool newly_allocated, uffd_flags_t flags);
76
77extern ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start,
78 unsigned long src_start, unsigned long len,
79 atomic_t *mmap_changing, uffd_flags_t flags);
80extern ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm,
81 unsigned long dst_start,
82 unsigned long len,
83 atomic_t *mmap_changing);
84extern ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long dst_start,
85 unsigned long len, atomic_t *mmap_changing,
86 uffd_flags_t flags);
87extern ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start,
88 unsigned long len, atomic_t *mmap_changing,
89 uffd_flags_t flags);
90extern int mwriteprotect_range(struct mm_struct *dst_mm,
91 unsigned long start, unsigned long len,
92 bool enable_wp, atomic_t *mmap_changing);
93extern long uffd_wp_range(struct vm_area_struct *vma,
94 unsigned long start, unsigned long len, bool enable_wp);
95
96/* mm helpers */
97static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
98 struct vm_userfaultfd_ctx vm_ctx)
99{
100 return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx;
101}
102
103/*
104 * Never enable huge pmd sharing on some uffd registered vmas:
105 *
106 * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry.
107 *
108 * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for
109 * VMAs which share huge pmds. (If you have two mappings to the same
110 * underlying pages, and fault in the non-UFFD-registered one with a write,
111 * with huge pmd sharing this would *also* setup the second UFFD-registered
112 * mapping, and we'd not get minor faults.)
113 */
114static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma)
115{
116 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
117}
118
119/*
120 * Don't do fault around for either WP or MINOR registered uffd range. For
121 * MINOR registered range, fault around will be a total disaster and ptes can
122 * be installed without notifications; for WP it should mostly be fine as long
123 * as the fault around checks for pte_none() before the installation, however
124 * to be super safe we just forbid it.
125 */
126static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
127{
128 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
129}
130
131static inline bool userfaultfd_missing(struct vm_area_struct *vma)
132{
133 return vma->vm_flags & VM_UFFD_MISSING;
134}
135
136static inline bool userfaultfd_wp(struct vm_area_struct *vma)
137{
138 return vma->vm_flags & VM_UFFD_WP;
139}
140
141static inline bool userfaultfd_minor(struct vm_area_struct *vma)
142{
143 return vma->vm_flags & VM_UFFD_MINOR;
144}
145
146static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
147 pte_t pte)
148{
149 return userfaultfd_wp(vma) && pte_uffd_wp(pte);
150}
151
152static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
153 pmd_t pmd)
154{
155 return userfaultfd_wp(vma) && pmd_uffd_wp(pmd);
156}
157
158static inline bool userfaultfd_armed(struct vm_area_struct *vma)
159{
160 return vma->vm_flags & __VM_UFFD_FLAGS;
161}
162
163static inline bool vma_can_userfault(struct vm_area_struct *vma,
164 unsigned long vm_flags,
165 bool wp_async)
166{
167 vm_flags &= __VM_UFFD_FLAGS;
168
169 if ((vm_flags & VM_UFFD_MINOR) &&
170 (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
171 return false;
172
173 /*
174 * If wp async enabled, and WP is the only mode enabled, allow any
175 * memory type.
176 */
177 if (wp_async && (vm_flags == VM_UFFD_WP))
178 return true;
179
180#ifndef CONFIG_PTE_MARKER_UFFD_WP
181 /*
182 * If user requested uffd-wp but not enabled pte markers for
183 * uffd-wp, then shmem & hugetlbfs are not supported but only
184 * anonymous.
185 */
186 if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
187 return false;
188#endif
189
190 /* By default, allow any of anon|shmem|hugetlb */
191 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
192 vma_is_shmem(vma);
193}
194
195extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
196extern void dup_userfaultfd_complete(struct list_head *);
197
198extern void mremap_userfaultfd_prep(struct vm_area_struct *,
199 struct vm_userfaultfd_ctx *);
200extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *,
201 unsigned long from, unsigned long to,
202 unsigned long len);
203
204extern bool userfaultfd_remove(struct vm_area_struct *vma,
205 unsigned long start,
206 unsigned long end);
207
208extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
209 unsigned long start, unsigned long end, struct list_head *uf);
210extern void userfaultfd_unmap_complete(struct mm_struct *mm,
211 struct list_head *uf);
212extern bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma);
213extern bool userfaultfd_wp_async(struct vm_area_struct *vma);
214
215#else /* CONFIG_USERFAULTFD */
216
217/* mm helpers */
218static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
219 unsigned long reason)
220{
221 return VM_FAULT_SIGBUS;
222}
223
224static inline long uffd_wp_range(struct vm_area_struct *vma,
225 unsigned long start, unsigned long len,
226 bool enable_wp)
227{
228 return false;
229}
230
231static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
232 struct vm_userfaultfd_ctx vm_ctx)
233{
234 return true;
235}
236
237static inline bool userfaultfd_missing(struct vm_area_struct *vma)
238{
239 return false;
240}
241
242static inline bool userfaultfd_wp(struct vm_area_struct *vma)
243{
244 return false;
245}
246
247static inline bool userfaultfd_minor(struct vm_area_struct *vma)
248{
249 return false;
250}
251
252static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
253 pte_t pte)
254{
255 return false;
256}
257
258static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
259 pmd_t pmd)
260{
261 return false;
262}
263
264
265static inline bool userfaultfd_armed(struct vm_area_struct *vma)
266{
267 return false;
268}
269
270static inline int dup_userfaultfd(struct vm_area_struct *vma,
271 struct list_head *l)
272{
273 return 0;
274}
275
276static inline void dup_userfaultfd_complete(struct list_head *l)
277{
278}
279
280static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma,
281 struct vm_userfaultfd_ctx *ctx)
282{
283}
284
285static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx,
286 unsigned long from,
287 unsigned long to,
288 unsigned long len)
289{
290}
291
292static inline bool userfaultfd_remove(struct vm_area_struct *vma,
293 unsigned long start,
294 unsigned long end)
295{
296 return true;
297}
298
299static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
300 unsigned long start, unsigned long end,
301 struct list_head *uf)
302{
303 return 0;
304}
305
306static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
307 struct list_head *uf)
308{
309}
310
311static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
312{
313 return false;
314}
315
316static inline bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma)
317{
318 return false;
319}
320
321static inline bool userfaultfd_wp_async(struct vm_area_struct *vma)
322{
323 return false;
324}
325
326#endif /* CONFIG_USERFAULTFD */
327
328static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
329{
330 /* Only wr-protect mode uses pte markers */
331 if (!userfaultfd_wp(vma))
332 return false;
333
334 /* File-based uffd-wp always need markers */
335 if (!vma_is_anonymous(vma))
336 return true;
337
338 /*
339 * Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
340 * enabled (to apply markers on zero pages).
341 */
342 return userfaultfd_wp_unpopulated(vma);
343}
344
345static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
346{
347#ifdef CONFIG_PTE_MARKER_UFFD_WP
348 return is_pte_marker_entry(entry) &&
349 (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
350#else
351 return false;
352#endif
353}
354
355static inline bool pte_marker_uffd_wp(pte_t pte)
356{
357#ifdef CONFIG_PTE_MARKER_UFFD_WP
358 swp_entry_t entry;
359
360 if (!is_swap_pte(pte))
361 return false;
362
363 entry = pte_to_swp_entry(pte);
364
365 return pte_marker_entry_uffd_wp(entry);
366#else
367 return false;
368#endif
369}
370
371/*
372 * Returns true if this is a swap pte and was uffd-wp wr-protected in either
373 * forms (pte marker or a normal swap pte), false otherwise.
374 */
375static inline bool pte_swp_uffd_wp_any(pte_t pte)
376{
377#ifdef CONFIG_PTE_MARKER_UFFD_WP
378 if (!is_swap_pte(pte))
379 return false;
380
381 if (pte_swp_uffd_wp(pte))
382 return true;
383
384 if (pte_marker_uffd_wp(pte))
385 return true;
386#endif
387 return false;
388}
389
390#endif /* _LINUX_USERFAULTFD_K_H */
391

source code of linux/include/linux/userfaultfd_k.h