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 int sysctl_unprivileged_userfaultfd;
40
41extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
42
43/*
44 * The mode of operation for __mcopy_atomic and its helpers.
45 *
46 * This is almost an implementation detail (mcopy_atomic below doesn't take this
47 * as a parameter), but it's exposed here because memory-kind-specific
48 * implementations (e.g. hugetlbfs) need to know the mode of operation.
49 */
50enum mcopy_atomic_mode {
51 /* A normal copy_from_user into the destination range. */
52 MCOPY_ATOMIC_NORMAL,
53 /* Don't copy; map the destination range to the zero page. */
54 MCOPY_ATOMIC_ZEROPAGE,
55 /* Just install pte(s) with the existing page(s) in the page cache. */
56 MCOPY_ATOMIC_CONTINUE,
57};
58
59extern int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
60 struct vm_area_struct *dst_vma,
61 unsigned long dst_addr, struct page *page,
62 bool newly_allocated, bool wp_copy);
63
64extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
65 unsigned long src_start, unsigned long len,
66 atomic_t *mmap_changing, __u64 mode);
67extern ssize_t mfill_zeropage(struct mm_struct *dst_mm,
68 unsigned long dst_start,
69 unsigned long len,
70 atomic_t *mmap_changing);
71extern ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long dst_start,
72 unsigned long len, atomic_t *mmap_changing);
73extern int mwriteprotect_range(struct mm_struct *dst_mm,
74 unsigned long start, unsigned long len,
75 bool enable_wp, atomic_t *mmap_changing);
76
77/* mm helpers */
78static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
79 struct vm_userfaultfd_ctx vm_ctx)
80{
81 return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx;
82}
83
84/*
85 * Never enable huge pmd sharing on some uffd registered vmas:
86 *
87 * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry.
88 *
89 * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for
90 * VMAs which share huge pmds. (If you have two mappings to the same
91 * underlying pages, and fault in the non-UFFD-registered one with a write,
92 * with huge pmd sharing this would *also* setup the second UFFD-registered
93 * mapping, and we'd not get minor faults.)
94 */
95static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma)
96{
97 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
98}
99
100/*
101 * Don't do fault around for either WP or MINOR registered uffd range. For
102 * MINOR registered range, fault around will be a total disaster and ptes can
103 * be installed without notifications; for WP it should mostly be fine as long
104 * as the fault around checks for pte_none() before the installation, however
105 * to be super safe we just forbid it.
106 */
107static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
108{
109 return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
110}
111
112static inline bool userfaultfd_missing(struct vm_area_struct *vma)
113{
114 return vma->vm_flags & VM_UFFD_MISSING;
115}
116
117static inline bool userfaultfd_wp(struct vm_area_struct *vma)
118{
119 return vma->vm_flags & VM_UFFD_WP;
120}
121
122static inline bool userfaultfd_minor(struct vm_area_struct *vma)
123{
124 return vma->vm_flags & VM_UFFD_MINOR;
125}
126
127static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
128 pte_t pte)
129{
130 return userfaultfd_wp(vma) && pte_uffd_wp(pte);
131}
132
133static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
134 pmd_t pmd)
135{
136 return userfaultfd_wp(vma) && pmd_uffd_wp(pmd);
137}
138
139static inline bool userfaultfd_armed(struct vm_area_struct *vma)
140{
141 return vma->vm_flags & __VM_UFFD_FLAGS;
142}
143
144static inline bool vma_can_userfault(struct vm_area_struct *vma,
145 unsigned long vm_flags)
146{
147 if (vm_flags & VM_UFFD_MINOR)
148 return is_vm_hugetlb_page(vma) || vma_is_shmem(vma);
149
150#ifndef CONFIG_PTE_MARKER_UFFD_WP
151 /*
152 * If user requested uffd-wp but not enabled pte markers for
153 * uffd-wp, then shmem & hugetlbfs are not supported but only
154 * anonymous.
155 */
156 if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
157 return false;
158#endif
159 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
160 vma_is_shmem(vma);
161}
162
163extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
164extern void dup_userfaultfd_complete(struct list_head *);
165
166extern void mremap_userfaultfd_prep(struct vm_area_struct *,
167 struct vm_userfaultfd_ctx *);
168extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *,
169 unsigned long from, unsigned long to,
170 unsigned long len);
171
172extern bool userfaultfd_remove(struct vm_area_struct *vma,
173 unsigned long start,
174 unsigned long end);
175
176extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
177 unsigned long start, unsigned long end,
178 struct list_head *uf);
179extern void userfaultfd_unmap_complete(struct mm_struct *mm,
180 struct list_head *uf);
181
182#else /* CONFIG_USERFAULTFD */
183
184/* mm helpers */
185static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
186 unsigned long reason)
187{
188 return VM_FAULT_SIGBUS;
189}
190
191static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
192 struct vm_userfaultfd_ctx vm_ctx)
193{
194 return true;
195}
196
197static inline bool userfaultfd_missing(struct vm_area_struct *vma)
198{
199 return false;
200}
201
202static inline bool userfaultfd_wp(struct vm_area_struct *vma)
203{
204 return false;
205}
206
207static inline bool userfaultfd_minor(struct vm_area_struct *vma)
208{
209 return false;
210}
211
212static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
213 pte_t pte)
214{
215 return false;
216}
217
218static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
219 pmd_t pmd)
220{
221 return false;
222}
223
224
225static inline bool userfaultfd_armed(struct vm_area_struct *vma)
226{
227 return false;
228}
229
230static inline int dup_userfaultfd(struct vm_area_struct *vma,
231 struct list_head *l)
232{
233 return 0;
234}
235
236static inline void dup_userfaultfd_complete(struct list_head *l)
237{
238}
239
240static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma,
241 struct vm_userfaultfd_ctx *ctx)
242{
243}
244
245static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx,
246 unsigned long from,
247 unsigned long to,
248 unsigned long len)
249{
250}
251
252static inline bool userfaultfd_remove(struct vm_area_struct *vma,
253 unsigned long start,
254 unsigned long end)
255{
256 return true;
257}
258
259static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
260 unsigned long start, unsigned long end,
261 struct list_head *uf)
262{
263 return 0;
264}
265
266static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
267 struct list_head *uf)
268{
269}
270
271static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
272{
273 return false;
274}
275
276#endif /* CONFIG_USERFAULTFD */
277
278static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
279{
280#ifdef CONFIG_PTE_MARKER_UFFD_WP
281 return is_pte_marker_entry(entry) &&
282 (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
283#else
284 return false;
285#endif
286}
287
288static inline bool pte_marker_uffd_wp(pte_t pte)
289{
290#ifdef CONFIG_PTE_MARKER_UFFD_WP
291 swp_entry_t entry;
292
293 if (!is_swap_pte(pte))
294 return false;
295
296 entry = pte_to_swp_entry(pte);
297
298 return pte_marker_entry_uffd_wp(entry);
299#else
300 return false;
301#endif
302}
303
304/*
305 * Returns true if this is a swap pte and was uffd-wp wr-protected in either
306 * forms (pte marker or a normal swap pte), false otherwise.
307 */
308static inline bool pte_swp_uffd_wp_any(pte_t pte)
309{
310#ifdef CONFIG_PTE_MARKER_UFFD_WP
311 if (!is_swap_pte(pte))
312 return false;
313
314 if (pte_swp_uffd_wp(pte))
315 return true;
316
317 if (pte_marker_uffd_wp(pte))
318 return true;
319#endif
320 return false;
321}
322
323#endif /* _LINUX_USERFAULTFD_K_H */
324

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