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 copy_mc;
44 bool nofault;
45 bool data_source;
46 size_t iov_offset;
47 /*
48 * Hack alert: overlay ubuf_iovec with iovec + count, so
49 * that the members resolve correctly regardless of the type
50 * of iterator used. This means that you can use:
51 *
52 * &iter->__ubuf_iovec or iter->__iov
53 *
54 * interchangably for the user_backed cases, hence simplifying
55 * some of the cases that need to deal with both.
56 */
57 union {
58 /*
59 * This really should be a const, but we cannot do that without
60 * also modifying any of the zero-filling iter init functions.
61 * Leave it non-const for now, but it should be treated as such.
62 */
63 struct iovec __ubuf_iovec;
64 struct {
65 union {
66 /* use iter_iov() to get the current vec */
67 const struct iovec *__iov;
68 const struct kvec *kvec;
69 const struct bio_vec *bvec;
70 struct xarray *xarray;
71 void __user *ubuf;
72 };
73 size_t count;
74 };
75 };
76 union {
77 unsigned long nr_segs;
78 loff_t xarray_start;
79 };
80};
81
82static inline const struct iovec *iter_iov(const struct iov_iter *iter)
83{
84 if (iter->iter_type == ITER_UBUF)
85 return (const struct iovec *) &iter->__ubuf_iovec;
86 return iter->__iov;
87}
88
89#define iter_iov_addr(iter) (iter_iov(iter)->iov_base + (iter)->iov_offset)
90#define iter_iov_len(iter) (iter_iov(iter)->iov_len - (iter)->iov_offset)
91
92static inline enum iter_type iov_iter_type(const struct iov_iter *i)
93{
94 return i->iter_type;
95}
96
97static inline void iov_iter_save_state(struct iov_iter *iter,
98 struct iov_iter_state *state)
99{
100 state->iov_offset = iter->iov_offset;
101 state->count = iter->count;
102 state->nr_segs = iter->nr_segs;
103}
104
105static inline bool iter_is_ubuf(const struct iov_iter *i)
106{
107 return iov_iter_type(i) == ITER_UBUF;
108}
109
110static inline bool iter_is_iovec(const struct iov_iter *i)
111{
112 return iov_iter_type(i) == ITER_IOVEC;
113}
114
115static inline bool iov_iter_is_kvec(const struct iov_iter *i)
116{
117 return iov_iter_type(i) == ITER_KVEC;
118}
119
120static inline bool iov_iter_is_bvec(const struct iov_iter *i)
121{
122 return iov_iter_type(i) == ITER_BVEC;
123}
124
125static inline bool iov_iter_is_discard(const struct iov_iter *i)
126{
127 return iov_iter_type(i) == ITER_DISCARD;
128}
129
130static inline bool iov_iter_is_xarray(const struct iov_iter *i)
131{
132 return iov_iter_type(i) == ITER_XARRAY;
133}
134
135static inline unsigned char iov_iter_rw(const struct iov_iter *i)
136{
137 return i->data_source ? WRITE : READ;
138}
139
140static inline bool user_backed_iter(const struct iov_iter *i)
141{
142 return iter_is_ubuf(i) || iter_is_iovec(i);
143}
144
145/*
146 * Total number of bytes covered by an iovec.
147 *
148 * NOTE that it is not safe to use this function until all the iovec's
149 * segment lengths have been validated. Because the individual lengths can
150 * overflow a size_t when added together.
151 */
152static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
153{
154 unsigned long seg;
155 size_t ret = 0;
156
157 for (seg = 0; seg < nr_segs; seg++)
158 ret += iov[seg].iov_len;
159 return ret;
160}
161
162size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
163 size_t bytes, struct iov_iter *i);
164void iov_iter_advance(struct iov_iter *i, size_t bytes);
165void iov_iter_revert(struct iov_iter *i, size_t bytes);
166size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t bytes);
167size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t bytes);
168size_t iov_iter_single_seg_count(const struct iov_iter *i);
169size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
170 struct iov_iter *i);
171size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
172 struct iov_iter *i);
173
174size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
175size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
176size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
177
178static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset,
179 size_t bytes, struct iov_iter *i)
180{
181 return copy_page_to_iter(page: &folio->page, offset, bytes, i);
182}
183
184static inline size_t copy_folio_from_iter_atomic(struct folio *folio,
185 size_t offset, size_t bytes, struct iov_iter *i)
186{
187 return copy_page_from_iter_atomic(page: &folio->page, offset, bytes, i);
188}
189
190size_t copy_page_to_iter_nofault(struct page *page, unsigned offset,
191 size_t bytes, struct iov_iter *i);
192
193static __always_inline __must_check
194size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
195{
196 if (check_copy_size(addr, bytes, is_source: true))
197 return _copy_to_iter(addr, bytes, i);
198 return 0;
199}
200
201static __always_inline __must_check
202size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
203{
204 if (check_copy_size(addr, bytes, is_source: false))
205 return _copy_from_iter(addr, bytes, i);
206 return 0;
207}
208
209static __always_inline __must_check
210bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
211{
212 size_t copied = copy_from_iter(addr, bytes, i);
213 if (likely(copied == bytes))
214 return true;
215 iov_iter_revert(i, bytes: copied);
216 return false;
217}
218
219static __always_inline __must_check
220size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
221{
222 if (check_copy_size(addr, bytes, is_source: false))
223 return _copy_from_iter_nocache(addr, bytes, i);
224 return 0;
225}
226
227static __always_inline __must_check
228bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
229{
230 size_t copied = copy_from_iter_nocache(addr, bytes, i);
231 if (likely(copied == bytes))
232 return true;
233 iov_iter_revert(i, bytes: copied);
234 return false;
235}
236
237#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
238/*
239 * Note, users like pmem that depend on the stricter semantics of
240 * _copy_from_iter_flushcache() than _copy_from_iter_nocache() must check for
241 * IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) before assuming that the
242 * destination is flushed from the cache on return.
243 */
244size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
245#else
246#define _copy_from_iter_flushcache _copy_from_iter_nocache
247#endif
248
249#ifdef CONFIG_ARCH_HAS_COPY_MC
250size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
251static inline void iov_iter_set_copy_mc(struct iov_iter *i)
252{
253 i->copy_mc = true;
254}
255
256static inline bool iov_iter_is_copy_mc(const struct iov_iter *i)
257{
258 return i->copy_mc;
259}
260#else
261#define _copy_mc_to_iter _copy_to_iter
262static inline void iov_iter_set_copy_mc(struct iov_iter *i) { }
263static inline bool iov_iter_is_copy_mc(const struct iov_iter *i)
264{
265 return false;
266}
267#endif
268
269size_t iov_iter_zero(size_t bytes, struct iov_iter *);
270bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
271 unsigned len_mask);
272unsigned long iov_iter_alignment(const struct iov_iter *i);
273unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
274void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov,
275 unsigned long nr_segs, size_t count);
276void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec *kvec,
277 unsigned long nr_segs, size_t count);
278void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
279 unsigned long nr_segs, size_t count);
280void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
281void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
282 loff_t start, size_t count);
283ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
284 size_t maxsize, unsigned maxpages, size_t *start);
285ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages,
286 size_t maxsize, size_t *start);
287int iov_iter_npages(const struct iov_iter *i, int maxpages);
288void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state);
289
290const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
291
292static inline size_t iov_iter_count(const struct iov_iter *i)
293{
294 return i->count;
295}
296
297/*
298 * Cap the iov_iter by given limit; note that the second argument is
299 * *not* the new size - it's upper limit for such. Passing it a value
300 * greater than the amount of data in iov_iter is fine - it'll just do
301 * nothing in that case.
302 */
303static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
304{
305 /*
306 * count doesn't have to fit in size_t - comparison extends both
307 * operands to u64 here and any value that would be truncated by
308 * conversion in assignement is by definition greater than all
309 * values of size_t, including old i->count.
310 */
311 if (i->count > count)
312 i->count = count;
313}
314
315/*
316 * reexpand a previously truncated iterator; count must be no more than how much
317 * we had shrunk it.
318 */
319static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
320{
321 i->count = count;
322}
323
324static inline int
325iov_iter_npages_cap(struct iov_iter *i, int maxpages, size_t max_bytes)
326{
327 size_t shorted = 0;
328 int npages;
329
330 if (iov_iter_count(i) > max_bytes) {
331 shorted = iov_iter_count(i) - max_bytes;
332 iov_iter_truncate(i, count: max_bytes);
333 }
334 npages = iov_iter_npages(i, maxpages);
335 if (shorted)
336 iov_iter_reexpand(i, count: iov_iter_count(i) + shorted);
337
338 return npages;
339}
340
341struct iovec *iovec_from_user(const struct iovec __user *uvector,
342 unsigned long nr_segs, unsigned long fast_segs,
343 struct iovec *fast_iov, bool compat);
344ssize_t import_iovec(int type, const struct iovec __user *uvec,
345 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
346 struct iov_iter *i);
347ssize_t __import_iovec(int type, const struct iovec __user *uvec,
348 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
349 struct iov_iter *i, bool compat);
350int import_single_range(int type, void __user *buf, size_t len,
351 struct iovec *iov, struct iov_iter *i);
352int import_ubuf(int type, void __user *buf, size_t len, struct iov_iter *i);
353
354static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
355 void __user *buf, size_t count)
356{
357 WARN_ON(direction & ~(READ | WRITE));
358 *i = (struct iov_iter) {
359 .iter_type = ITER_UBUF,
360 .copy_mc = false,
361 .data_source = direction,
362 .ubuf = buf,
363 .count = count,
364 .nr_segs = 1
365 };
366}
367/* Flags for iov_iter_get/extract_pages*() */
368/* Allow P2PDMA on the extracted pages */
369#define ITER_ALLOW_P2PDMA ((__force iov_iter_extraction_t)0x01)
370
371ssize_t iov_iter_extract_pages(struct iov_iter *i, struct page ***pages,
372 size_t maxsize, unsigned int maxpages,
373 iov_iter_extraction_t extraction_flags,
374 size_t *offset0);
375
376/**
377 * iov_iter_extract_will_pin - Indicate how pages from the iterator will be retained
378 * @iter: The iterator
379 *
380 * Examine the iterator and indicate by returning true or false as to how, if
381 * at all, pages extracted from the iterator will be retained by the extraction
382 * function.
383 *
384 * %true indicates that the pages will have a pin placed in them that the
385 * caller must unpin. This is must be done for DMA/async DIO to force fork()
386 * to forcibly copy a page for the child (the parent must retain the original
387 * page).
388 *
389 * %false indicates that no measures are taken and that it's up to the caller
390 * to retain the pages.
391 */
392static inline bool iov_iter_extract_will_pin(const struct iov_iter *iter)
393{
394 return user_backed_iter(i: iter);
395}
396
397struct sg_table;
398ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t len,
399 struct sg_table *sgtable, unsigned int sg_max,
400 iov_iter_extraction_t extraction_flags);
401
402#endif
403

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