userfaultfd_k.h

  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/*
 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_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
 34
 35/*
 36 * Start with fault_pending_wqh and fault_wqh so they're more likely
 37 * to be in the same cacheline.
 38 *
 39 * Locking order:
 40 *	fd_wqh.lock
 41 *		fault_pending_wqh.lock
 42 *			fault_wqh.lock
 43 *		event_wqh.lock
 44 *
 45 * To avoid deadlocks, IRQs must be disabled when taking any of the above locks,
 46 * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's
 47 * also taken in IRQ context.
 48 */
 49struct userfaultfd_ctx {
 50	/* waitqueue head for the pending (i.e. not read) userfaults */
 51	wait_queue_head_t fault_pending_wqh;
 52	/* waitqueue head for the userfaults */
 53	wait_queue_head_t fault_wqh;
 54	/* waitqueue head for the pseudo fd to wakeup poll/read */
 55	wait_queue_head_t fd_wqh;
 56	/* waitqueue head for events */
 57	wait_queue_head_t event_wqh;
 58	/* a refile sequence protected by fault_pending_wqh lock */
 59	seqcount_spinlock_t refile_seq;
 60	/* pseudo fd refcounting */
 61	refcount_t refcount;
 62	/* userfaultfd syscall flags */
 63	unsigned int flags;
 64	/* features requested from the userspace */
 65	unsigned int features;
 66	/* released */
 67	bool released;
 68	/*
 69	 * Prevents userfaultfd operations (fill/move/wp) from happening while
 70	 * some non-cooperative event(s) is taking place. Increments are done
 71	 * in write-mode. Whereas, userfaultfd operations, which includes
 72	 * reading mmap_changing, is done under read-mode.
 73	 */
 74	struct rw_semaphore map_changing_lock;
 75	/* memory mappings are changing because of non-cooperative event */
 76	atomic_t mmap_changing;
 77	/* mm with one ore more vmas attached to this userfaultfd_ctx */
 78	struct mm_struct *mm;
 79};
 80
 81extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
 82
 83/* A combined operation mode + behavior flags. */
 84typedef unsigned int __bitwise uffd_flags_t;
 85
 86/* Mutually exclusive modes of operation. */
 87enum mfill_atomic_mode {
 88	MFILL_ATOMIC_COPY,
 89	MFILL_ATOMIC_ZEROPAGE,
 90	MFILL_ATOMIC_CONTINUE,
 91	MFILL_ATOMIC_POISON,
 92	NR_MFILL_ATOMIC_MODES,
 93};
 94
 95#define MFILL_ATOMIC_MODE_BITS (const_ilog2(NR_MFILL_ATOMIC_MODES - 1) + 1)
 96#define MFILL_ATOMIC_BIT(nr) BIT(MFILL_ATOMIC_MODE_BITS + (nr))
 97#define MFILL_ATOMIC_FLAG(nr) ((__force uffd_flags_t) MFILL_ATOMIC_BIT(nr))
 98#define MFILL_ATOMIC_MODE_MASK ((__force uffd_flags_t) (MFILL_ATOMIC_BIT(0) - 1))
 99
100static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)
101{
102	return (flags & MFILL_ATOMIC_MODE_MASK) == ((__force uffd_flags_t) expected);
103}
104
105static inline uffd_flags_t uffd_flags_set_mode(uffd_flags_t flags, enum mfill_atomic_mode mode)
106{
107	flags &= ~MFILL_ATOMIC_MODE_MASK;
108	return flags | ((__force uffd_flags_t) mode);
109}
110
111/* Flags controlling behavior. These behavior changes are mode-independent. */
112#define MFILL_ATOMIC_WP MFILL_ATOMIC_FLAG(0)
113
114extern int mfill_atomic_install_pte(pmd_t *dst_pmd,
115				    struct vm_area_struct *dst_vma,
116				    unsigned long dst_addr, struct page *page,
117				    bool newly_allocated, uffd_flags_t flags);
118
119extern ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned long dst_start,
120				 unsigned long src_start, unsigned long len,
121				 uffd_flags_t flags);
122extern ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx,
123				     unsigned long dst_start,
124				     unsigned long len);
125extern ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned long dst_start,
126				     unsigned long len, uffd_flags_t flags);
127extern ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned long start,
128				   unsigned long len, uffd_flags_t flags);
129extern int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long start,
130			       unsigned long len, bool enable_wp);
131extern long uffd_wp_range(struct vm_area_struct *vma,
132			  unsigned long start, unsigned long len, bool enable_wp);
133
134/* move_pages */
135void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2);
136void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2);
137ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
138		   unsigned long src_start, unsigned long len, __u64 flags);
139int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval,
140			struct vm_area_struct *dst_vma,
141			struct vm_area_struct *src_vma,
142			unsigned long dst_addr, unsigned long src_addr);
143
144/* mm helpers */
145static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
146					struct vm_userfaultfd_ctx vm_ctx)
147{
148	return vma->vm_userfaultfd_ctx.ctx == vm_ctx.ctx;
149}
150
151/*
152 * Never enable huge pmd sharing on some uffd registered vmas:
153 *
154 * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry.
155 *
156 * - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for
157 *   VMAs which share huge pmds. (If you have two mappings to the same
158 *   underlying pages, and fault in the non-UFFD-registered one with a write,
159 *   with huge pmd sharing this would *also* setup the second UFFD-registered
160 *   mapping, and we'd not get minor faults.)
161 */
162static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma)
163{
164	return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
165}
166
167/*
168 * Don't do fault around for either WP or MINOR registered uffd range.  For
169 * MINOR registered range, fault around will be a total disaster and ptes can
170 * be installed without notifications; for WP it should mostly be fine as long
171 * as the fault around checks for pte_none() before the installation, however
172 * to be super safe we just forbid it.
173 */
174static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
175{
176	return vma->vm_flags & (VM_UFFD_WP | VM_UFFD_MINOR);
177}
178
179static inline bool userfaultfd_missing(struct vm_area_struct *vma)
180{
181	return vma->vm_flags & VM_UFFD_MISSING;
182}
183
184static inline bool userfaultfd_wp(struct vm_area_struct *vma)
185{
186	return vma->vm_flags & VM_UFFD_WP;
187}
188
189static inline bool userfaultfd_minor(struct vm_area_struct *vma)
190{
191	return vma->vm_flags & VM_UFFD_MINOR;
192}
193
194static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
195				      pte_t pte)
196{
197	return userfaultfd_wp(vma) && pte_uffd_wp(pte);
198}
199
200static inline bool userfaultfd_huge_pmd_wp(struct vm_area_struct *vma,
201					   pmd_t pmd)
202{
203	return userfaultfd_wp(vma) && pmd_uffd_wp(pmd);
204}
205
206static inline bool userfaultfd_armed(struct vm_area_struct *vma)
207{
208	return vma->vm_flags & __VM_UFFD_FLAGS;
209}
210
211static inline bool vma_can_userfault(struct vm_area_struct *vma,
212				     vm_flags_t vm_flags,
213				     bool wp_async)
214{
215	vm_flags &= __VM_UFFD_FLAGS;
216
217	if (vma->vm_flags & VM_DROPPABLE)
218		return false;
219
220	if ((vm_flags & VM_UFFD_MINOR) &&
221	    (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
222		return false;
223
224	/*
225	 * If wp async enabled, and WP is the only mode enabled, allow any
226	 * memory type.
227	 */
228	if (wp_async && (vm_flags == VM_UFFD_WP))
229		return true;
230
231	/*
232	 * If user requested uffd-wp but not enabled pte markers for
233	 * uffd-wp, then shmem & hugetlbfs are not supported but only
234	 * anonymous.
235	 */
236	if (!uffd_supports_wp_marker() && (vm_flags & VM_UFFD_WP) &&
237	    !vma_is_anonymous(vma))
238		return false;
239
240	/* By default, allow any of anon|shmem|hugetlb */
241	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
242	    vma_is_shmem(vma);
243}
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 */