1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * Berkeley style UIO structures - Alan Cox 1994.
4 */
5#ifndef __LINUX_UIO_H
6#define __LINUX_UIO_H
7
8#include <linux/kernel.h>
9#include <linux/thread_info.h>
10#include <linux/mm_types.h>
11#include <uapi/linux/uio.h>
12
13struct page;
14
15typedef unsigned int __bitwise iov_iter_extraction_t;
16
17struct kvec {
18 void *iov_base; /* and that should *never* hold a userland pointer */
19 size_t iov_len;
20};
21
22enum iter_type {
23 /* iter types */
24 ITER_UBUF,
25 ITER_IOVEC,
26 ITER_BVEC,
27 ITER_KVEC,
28 ITER_XARRAY,
29 ITER_DISCARD,
30};
31
32#define ITER_SOURCE 1 // == WRITE
33#define ITER_DEST 0 // == READ
34
35struct iov_iter_state {
36 size_t iov_offset;
37 size_t count;
38 unsigned long nr_segs;
39};
40
41struct iov_iter {
42 u8 iter_type;
43 bool nofault;
44 bool data_source;
45 size_t iov_offset;
46 /*
47 * Hack alert: overlay ubuf_iovec with iovec + count, so
48 * that the members resolve correctly regardless of the type
49 * of iterator used. This means that you can use:
50 *
51 * &iter->__ubuf_iovec or iter->__iov
52 *
53 * interchangably for the user_backed cases, hence simplifying
54 * some of the cases that need to deal with both.
55 */
56 union {
57 /*
58 * This really should be a const, but we cannot do that without
59 * also modifying any of the zero-filling iter init functions.
60 * Leave it non-const for now, but it should be treated as such.
61 */
62 struct iovec __ubuf_iovec;
63 struct {
64 union {
65 /* use iter_iov() to get the current vec */
66 const struct iovec *__iov;
67 const struct kvec *kvec;
68 const struct bio_vec *bvec;
69 struct xarray *xarray;
70 void __user *ubuf;
71 };
72 size_t count;
73 };
74 };
75 union {
76 unsigned long nr_segs;
77 loff_t xarray_start;
78 };
79};
80
81static inline const struct iovec *iter_iov(const struct iov_iter *iter)
82{
83 if (iter->iter_type == ITER_UBUF)
84 return (const struct iovec *) &iter->__ubuf_iovec;
85 return iter->__iov;
86}
87
88#define iter_iov_addr(iter) (iter_iov(iter)->iov_base + (iter)->iov_offset)
89#define iter_iov_len(iter) (iter_iov(iter)->iov_len - (iter)->iov_offset)
90
91static inline enum iter_type iov_iter_type(const struct iov_iter *i)
92{
93 return i->iter_type;
94}
95
96static inline void iov_iter_save_state(struct iov_iter *iter,
97 struct iov_iter_state *state)
98{
99 state->iov_offset = iter->iov_offset;
100 state->count = iter->count;
101 state->nr_segs = iter->nr_segs;
102}
103
104static inline bool iter_is_ubuf(const struct iov_iter *i)
105{
106 return iov_iter_type(i) == ITER_UBUF;
107}
108
109static inline bool iter_is_iovec(const struct iov_iter *i)
110{
111 return iov_iter_type(i) == ITER_IOVEC;
112}
113
114static inline bool iov_iter_is_kvec(const struct iov_iter *i)
115{
116 return iov_iter_type(i) == ITER_KVEC;
117}
118
119static inline bool iov_iter_is_bvec(const struct iov_iter *i)
120{
121 return iov_iter_type(i) == ITER_BVEC;
122}
123
124static inline bool iov_iter_is_discard(const struct iov_iter *i)
125{
126 return iov_iter_type(i) == ITER_DISCARD;
127}
128
129static inline bool iov_iter_is_xarray(const struct iov_iter *i)
130{
131 return iov_iter_type(i) == ITER_XARRAY;
132}
133
134static inline unsigned char iov_iter_rw(const struct iov_iter *i)
135{
136 return i->data_source ? WRITE : READ;
137}
138
139static inline bool user_backed_iter(const struct iov_iter *i)
140{
141 return iter_is_ubuf(i) || iter_is_iovec(i);
142}
143
144/*
145 * Total number of bytes covered by an iovec.
146 *
147 * NOTE that it is not safe to use this function until all the iovec's
148 * segment lengths have been validated. Because the individual lengths can
149 * overflow a size_t when added together.
150 */
151static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
152{
153 unsigned long seg;
154 size_t ret = 0;
155
156 for (seg = 0; seg < nr_segs; seg++)
157 ret += iov[seg].iov_len;
158 return ret;
159}
160
161size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
162 size_t bytes, struct iov_iter *i);
163void iov_iter_advance(struct iov_iter *i, size_t bytes);
164void iov_iter_revert(struct iov_iter *i, size_t bytes);
165size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t bytes);
166size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t bytes);
167size_t iov_iter_single_seg_count(const struct iov_iter *i);
168size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
169 struct iov_iter *i);
170size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
171 struct iov_iter *i);
172
173size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
174size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
175size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
176
177static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset,
178 size_t bytes, struct iov_iter *i)
179{
180 return copy_page_to_iter(page: &folio->page, offset, bytes, i);
181}
182
183static inline size_t copy_folio_from_iter_atomic(struct folio *folio,
184 size_t offset, size_t bytes, struct iov_iter *i)
185{
186 return copy_page_from_iter_atomic(page: &folio->page, offset, bytes, i);
187}
188
189size_t copy_page_to_iter_nofault(struct page *page, unsigned offset,
190 size_t bytes, struct iov_iter *i);
191
192static __always_inline __must_check
193size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
194{
195 if (check_copy_size(addr, bytes, is_source: true))
196 return _copy_to_iter(addr, bytes, i);
197 return 0;
198}
199
200static __always_inline __must_check
201size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
202{
203 if (check_copy_size(addr, bytes, is_source: false))
204 return _copy_from_iter(addr, bytes, i);
205 return 0;
206}
207
208static __always_inline __must_check
209bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
210{
211 size_t copied = copy_from_iter(addr, bytes, i);
212 if (likely(copied == bytes))
213 return true;
214 iov_iter_revert(i, bytes: copied);
215 return false;
216}
217
218static __always_inline __must_check
219size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
220{
221 if (check_copy_size(addr, bytes, is_source: false))
222 return _copy_from_iter_nocache(addr, bytes, i);
223 return 0;
224}
225
226static __always_inline __must_check
227bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
228{
229 size_t copied = copy_from_iter_nocache(addr, bytes, i);
230 if (likely(copied == bytes))
231 return true;
232 iov_iter_revert(i, bytes: copied);
233 return false;
234}
235
236#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
237/*
238 * Note, users like pmem that depend on the stricter semantics of
239 * _copy_from_iter_flushcache() than _copy_from_iter_nocache() must check for
240 * IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) before assuming that the
241 * destination is flushed from the cache on return.
242 */
243size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
244#else
245#define _copy_from_iter_flushcache _copy_from_iter_nocache
246#endif
247
248#ifdef CONFIG_ARCH_HAS_COPY_MC
249size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
250#else
251#define _copy_mc_to_iter _copy_to_iter
252#endif
253
254size_t iov_iter_zero(size_t bytes, struct iov_iter *);
255bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
256 unsigned len_mask);
257unsigned long iov_iter_alignment(const struct iov_iter *i);
258unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
259void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov,
260 unsigned long nr_segs, size_t count);
261void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec *kvec,
262 unsigned long nr_segs, size_t count);
263void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
264 unsigned long nr_segs, size_t count);
265void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
266void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
267 loff_t start, size_t count);
268ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
269 size_t maxsize, unsigned maxpages, size_t *start);
270ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages,
271 size_t maxsize, size_t *start);
272int iov_iter_npages(const struct iov_iter *i, int maxpages);
273void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state);
274
275const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
276
277static inline size_t iov_iter_count(const struct iov_iter *i)
278{
279 return i->count;
280}
281
282/*
283 * Cap the iov_iter by given limit; note that the second argument is
284 * *not* the new size - it's upper limit for such. Passing it a value
285 * greater than the amount of data in iov_iter is fine - it'll just do
286 * nothing in that case.
287 */
288static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
289{
290 /*
291 * count doesn't have to fit in size_t - comparison extends both
292 * operands to u64 here and any value that would be truncated by
293 * conversion in assignement is by definition greater than all
294 * values of size_t, including old i->count.
295 */
296 if (i->count > count)
297 i->count = count;
298}
299
300/*
301 * reexpand a previously truncated iterator; count must be no more than how much
302 * we had shrunk it.
303 */
304static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
305{
306 i->count = count;
307}
308
309static inline int
310iov_iter_npages_cap(struct iov_iter *i, int maxpages, size_t max_bytes)
311{
312 size_t shorted = 0;
313 int npages;
314
315 if (iov_iter_count(i) > max_bytes) {
316 shorted = iov_iter_count(i) - max_bytes;
317 iov_iter_truncate(i, count: max_bytes);
318 }
319 npages = iov_iter_npages(i, maxpages);
320 if (shorted)
321 iov_iter_reexpand(i, count: iov_iter_count(i) + shorted);
322
323 return npages;
324}
325
326struct iovec *iovec_from_user(const struct iovec __user *uvector,
327 unsigned long nr_segs, unsigned long fast_segs,
328 struct iovec *fast_iov, bool compat);
329ssize_t import_iovec(int type, const struct iovec __user *uvec,
330 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
331 struct iov_iter *i);
332ssize_t __import_iovec(int type, const struct iovec __user *uvec,
333 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
334 struct iov_iter *i, bool compat);
335int import_ubuf(int type, void __user *buf, size_t len, struct iov_iter *i);
336
337static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
338 void __user *buf, size_t count)
339{
340 WARN_ON(direction & ~(READ | WRITE));
341 *i = (struct iov_iter) {
342 .iter_type = ITER_UBUF,
343 .data_source = direction,
344 .ubuf = buf,
345 .count = count,
346 .nr_segs = 1
347 };
348}
349/* Flags for iov_iter_get/extract_pages*() */
350/* Allow P2PDMA on the extracted pages */
351#define ITER_ALLOW_P2PDMA ((__force iov_iter_extraction_t)0x01)
352
353ssize_t iov_iter_extract_pages(struct iov_iter *i, struct page ***pages,
354 size_t maxsize, unsigned int maxpages,
355 iov_iter_extraction_t extraction_flags,
356 size_t *offset0);
357
358/**
359 * iov_iter_extract_will_pin - Indicate how pages from the iterator will be retained
360 * @iter: The iterator
361 *
362 * Examine the iterator and indicate by returning true or false as to how, if
363 * at all, pages extracted from the iterator will be retained by the extraction
364 * function.
365 *
366 * %true indicates that the pages will have a pin placed in them that the
367 * caller must unpin. This is must be done for DMA/async DIO to force fork()
368 * to forcibly copy a page for the child (the parent must retain the original
369 * page).
370 *
371 * %false indicates that no measures are taken and that it's up to the caller
372 * to retain the pages.
373 */
374static inline bool iov_iter_extract_will_pin(const struct iov_iter *iter)
375{
376 return user_backed_iter(i: iter);
377}
378
379struct sg_table;
380ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t len,
381 struct sg_table *sgtable, unsigned int sg_max,
382 iov_iter_extraction_t extraction_flags);
383
384#endif
385

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