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