summaryrefslogtreecommitdiff
path: root/include/linux/userfaultfd_k.h
blob: ac7b0c96d351e4483523bbc787ac018cd8abb2ff (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
/* SPDX-License-Identifier: GPL-2.0 */
/*
 *  include/linux/userfaultfd_k.h
 *
 *  Copyright (C) 2015  Red Hat, Inc.
 *
 */

#ifndef _LINUX_USERFAULTFD_K_H
#define _LINUX_USERFAULTFD_K_H

#ifdef CONFIG_USERFAULTFD

#include <linux/userfaultfd.h> /* linux/include/uapi/linux/userfaultfd.h */

#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <asm-generic/pgtable_uffd.h>
#include <linux/hugetlb_inline.h>

/* The set of all possible UFFD-related VM flags. */
#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR)

/*
 * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
 * new flags, since they might collide with O_* ones. We want
 * to re-use O_* flags that couldn't possibly have a meaning
 * from userfaultfd, in order to leave a free define-space for
 * shared O_* flags.
 */
#define UFFD_CLOEXEC O_CLOEXEC
#define UFFD_NONBLOCK O_NONBLOCK

#define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
#define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS)

extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);

/* A combined operation mode + behavior flags. */
typedef unsigned int __bitwise uffd_flags_t;

/* Mutually exclusive modes of operation. */
enum mfill_atomic_mode {
	MFILL_ATOMIC_COPY,
	MFILL_ATOMIC_ZEROPAGE,
	MFILL_ATOMIC_CONTINUE,
	NR_MFILL_ATOMIC_MODES,
};

#define MFILL_ATOMIC_MODE_BITS (const_ilog2(NR_MFILL_ATOMIC_MODES - 1) + 1)
#define MFILL_ATOMIC_BIT(nr) BIT(MFILL_ATOMIC_MODE_BITS + (nr))
#define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr))
#define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1))

static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
{
	return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected);
}

static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode)
{
	flags &= ~MFILL_ATOMIC_MODE_MASK;
	return flags | ((__force uffd_flags_t) mode);
}

/* Flags controlling behavior. These behavior changes are mode-independent. */
#define MFILL_ATOMIC_WP MFILL_ATOMIC_FLAG(0)

extern int mfill_atomic_install_pte(pmd_t *dst_pmd,
				    struct vm_area_struct *dst_vma,
				    unsigned long dst_addr, struct page *page,
				    bool newly_allocated, uffd_flags_t flags);

extern ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start,
				 unsigned long src_start, unsigned long len,
				 atomic_t *mmap_changing, uffd_flags_t flags);
extern ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm,
				     unsigned long dst_start,
				     unsigned long len,
				     atomic_t *mmap_changing);
extern ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long dst_start,
				     unsigned long len, atomic_t *mmap_changing,
				     uffd_flags_t flags);
extern int mwriteprotect_range(struct mm_struct *dst_mm,
			       unsigned long start, unsigned long len,
			       bool enable_wp, atomic_t *mmap_changing);
extern long uffd_wp_range(struct vm_area_struct *vma,
			  unsigned long start, unsigned long len, bool enable_wp);

/* mm helpers */
static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
					struct vm_userfaultfd_ctx vm_ctx)
{
	return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx;
}

/*
 * Never enable huge pmd sharing on some uffd registered vmas:
 *
 * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry.
 *
 * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for
 *   VMAs which share huge pmds. (If you have two mappings to the same
 *   underlying pages, and fault in the non-UFFD-registered one with a write,
 *   with huge pmd sharing this would *also* setup the second UFFD-registered
 *   mapping, and we'd not get minor faults.)
 */
static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma)
{
	return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
}

/*
 * Don't do fault around for either WP or MINOR registered uffd range.  For
 * MINOR registered range, fault around will be a total disaster and ptes can
 * be installed without notifications; for WP it should mostly be fine as long
 * as the fault around checks for pte_none() before the installation, however
 * to be super safe we just forbid it.
 */
static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
{
	return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
}

static inline bool userfaultfd_missing(struct vm_area_struct *vma)
{
	return vma->vm_flags & VM_UFFD_MISSING;
}

static inline bool userfaultfd_wp(struct vm_area_struct *vma)
{
	return vma->vm_flags & VM_UFFD_WP;
}

static inline bool userfaultfd_minor(struct vm_area_struct *vma)
{
	return vma->vm_flags & VM_UFFD_MINOR;
}

static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
				      pte_t pte)
{
	return userfaultfd_wp(vma) && pte_uffd_wp(pte);
}

static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
					   pmd_t pmd)
{
	return userfaultfd_wp(vma) && pmd_uffd_wp(pmd);
}

static inline bool userfaultfd_armed(struct vm_area_struct *vma)
{
	return vma->vm_flags & __VM_UFFD_FLAGS;
}

static inline bool vma_can_userfault(struct vm_area_struct *vma,
				     unsigned long vm_flags)
{
	if ((vm_flags & VM_UFFD_MINOR) &&
	    (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
		return false;
#ifndef CONFIG_PTE_MARKER_UFFD_WP
	/*
	 * If user requested uffd-wp but not enabled pte markers for
	 * uffd-wp, then shmem & hugetlbfs are not supported but only
	 * anonymous.
	 */
	if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
		return false;
#endif
	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
	    vma_is_shmem(vma);
}

extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
extern void dup_userfaultfd_complete(struct list_head *);

extern void mremap_userfaultfd_prep(struct vm_area_struct *,
				    struct vm_userfaultfd_ctx *);
extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *,
					unsigned long from, unsigned long to,
					unsigned long len);

extern bool userfaultfd_remove(struct vm_area_struct *vma,
			       unsigned long start,
			       unsigned long end);

extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
		unsigned long start, unsigned long end, struct list_head *uf);
extern void userfaultfd_unmap_complete(struct mm_struct *mm,
				       struct list_head *uf);
extern bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma);

#else /* CONFIG_USERFAULTFD */

/* mm helpers */
static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
				unsigned long reason)
{
	return VM_FAULT_SIGBUS;
}

static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
					struct vm_userfaultfd_ctx vm_ctx)
{
	return true;
}

static inline bool userfaultfd_missing(struct vm_area_struct *vma)
{
	return false;
}

static inline bool userfaultfd_wp(struct vm_area_struct *vma)
{
	return false;
}

static inline bool userfaultfd_minor(struct vm_area_struct *vma)
{
	return false;
}

static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
				      pte_t pte)
{
	return false;
}

static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
					   pmd_t pmd)
{
	return false;
}


static inline bool userfaultfd_armed(struct vm_area_struct *vma)
{
	return false;
}

static inline int dup_userfaultfd(struct vm_area_struct *vma,
				  struct list_head *l)
{
	return 0;
}

static inline void dup_userfaultfd_complete(struct list_head *l)
{
}

static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma,
					   struct vm_userfaultfd_ctx *ctx)
{
}

static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx,
					       unsigned long from,
					       unsigned long to,
					       unsigned long len)
{
}

static inline bool userfaultfd_remove(struct vm_area_struct *vma,
				      unsigned long start,
				      unsigned long end)
{
	return true;
}

static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
					 unsigned long start, unsigned long end,
					 struct list_head *uf)
{
	return 0;
}

static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
					      struct list_head *uf)
{
}

static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
{
	return false;
}

static inline bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma)
{
	return false;
}

#endif /* CONFIG_USERFAULTFD */

static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
{
	/* Only wr-protect mode uses pte markers */
	if (!userfaultfd_wp(vma))
		return false;

	/* File-based uffd-wp always need markers */
	if (!vma_is_anonymous(vma))
		return true;

	/*
	 * Anonymous uffd-wp only needs the markers if WP_UNPOPULATED
	 * enabled (to apply markers on zero pages).
	 */
	return userfaultfd_wp_unpopulated(vma);
}

static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
	return is_pte_marker_entry(entry) &&
	    (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
#else
	return false;
#endif
}

static inline bool pte_marker_uffd_wp(pte_t pte)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
	swp_entry_t entry;

	if (!is_swap_pte(pte))
		return false;

	entry = pte_to_swp_entry(pte);

	return pte_marker_entry_uffd_wp(entry);
#else
	return false;
#endif
}

/*
 * Returns true if this is a swap pte and was uffd-wp wr-protected in either
 * forms (pte marker or a normal swap pte), false otherwise.
 */
static inline bool pte_swp_uffd_wp_any(pte_t pte)
{
#ifdef CONFIG_PTE_MARKER_UFFD_WP
	if (!is_swap_pte(pte))
		return false;

	if (pte_swp_uffd_wp(pte))
		return true;

	if (pte_marker_uffd_wp(pte))
		return true;
#endif
	return false;
}

#endif /* _LINUX_USERFAULTFD_K_H */