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 
13 struct page;
14 
15 typedef unsigned int __bitwise iov_iter_extraction_t;
16 
17 struct kvec {
18 	void *iov_base; /* and that should *never* hold a userland pointer */
19 	size_t iov_len;
20 };
21 
22 enum 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 
35 struct iov_iter_state {
36 	size_t iov_offset;
37 	size_t count;
38 	unsigned long nr_segs;
39 };
40 
41 struct 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 
iter_iov(const struct iov_iter * iter)81 static 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 
iov_iter_type(const struct iov_iter * i)91 static inline enum iter_type iov_iter_type(const struct iov_iter *i)
92 {
93 	return i->iter_type;
94 }
95 
iov_iter_save_state(struct iov_iter * iter,struct iov_iter_state * state)96 static 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 
iter_is_ubuf(const struct iov_iter * i)104 static inline bool iter_is_ubuf(const struct iov_iter *i)
105 {
106 	return iov_iter_type(i) == ITER_UBUF;
107 }
108 
iter_is_iovec(const struct iov_iter * i)109 static inline bool iter_is_iovec(const struct iov_iter *i)
110 {
111 	return iov_iter_type(i) == ITER_IOVEC;
112 }
113 
iov_iter_is_kvec(const struct iov_iter * i)114 static inline bool iov_iter_is_kvec(const struct iov_iter *i)
115 {
116 	return iov_iter_type(i) == ITER_KVEC;
117 }
118 
iov_iter_is_bvec(const struct iov_iter * i)119 static inline bool iov_iter_is_bvec(const struct iov_iter *i)
120 {
121 	return iov_iter_type(i) == ITER_BVEC;
122 }
123 
iov_iter_is_discard(const struct iov_iter * i)124 static inline bool iov_iter_is_discard(const struct iov_iter *i)
125 {
126 	return iov_iter_type(i) == ITER_DISCARD;
127 }
128 
iov_iter_is_xarray(const struct iov_iter * i)129 static inline bool iov_iter_is_xarray(const struct iov_iter *i)
130 {
131 	return iov_iter_type(i) == ITER_XARRAY;
132 }
133 
iov_iter_rw(const struct iov_iter * i)134 static inline unsigned char iov_iter_rw(const struct iov_iter *i)
135 {
136 	return i->data_source ? WRITE : READ;
137 }
138 
user_backed_iter(const struct iov_iter * i)139 static 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  */
iov_length(const struct iovec * iov,unsigned long nr_segs)151 static 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 
161 size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
162 				  size_t bytes, struct iov_iter *i);
163 void iov_iter_advance(struct iov_iter *i, size_t bytes);
164 void iov_iter_revert(struct iov_iter *i, size_t bytes);
165 size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t bytes);
166 size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t bytes);
167 size_t iov_iter_single_seg_count(const struct iov_iter *i);
168 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
169 			 struct iov_iter *i);
170 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
171 			 struct iov_iter *i);
172 
173 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
174 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
175 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
176 
copy_folio_to_iter(struct folio * folio,size_t offset,size_t bytes,struct iov_iter * i)177 static 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(&folio->page, offset, bytes, i);
181 }
182 
copy_folio_from_iter_atomic(struct folio * folio,size_t offset,size_t bytes,struct iov_iter * i)183 static 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(&folio->page, offset, bytes, i);
187 }
188 
189 size_t copy_page_to_iter_nofault(struct page *page, unsigned offset,
190 				 size_t bytes, struct iov_iter *i);
191 
192 static __always_inline __must_check
copy_to_iter(const void * addr,size_t bytes,struct iov_iter * i)193 size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
194 {
195 	if (check_copy_size(addr, bytes, true))
196 		return _copy_to_iter(addr, bytes, i);
197 	return 0;
198 }
199 
200 static __always_inline __must_check
copy_from_iter(void * addr,size_t bytes,struct iov_iter * i)201 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
202 {
203 	if (check_copy_size(addr, bytes, false))
204 		return _copy_from_iter(addr, bytes, i);
205 	return 0;
206 }
207 
208 static __always_inline __must_check
copy_from_iter_full(void * addr,size_t bytes,struct iov_iter * i)209 bool 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, copied);
215 	return false;
216 }
217 
218 static __always_inline __must_check
copy_from_iter_nocache(void * addr,size_t bytes,struct iov_iter * i)219 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
220 {
221 	if (check_copy_size(addr, bytes, false))
222 		return _copy_from_iter_nocache(addr, bytes, i);
223 	return 0;
224 }
225 
226 static __always_inline __must_check
copy_from_iter_full_nocache(void * addr,size_t bytes,struct iov_iter * i)227 bool 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, 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  */
243 size_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
249 size_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 
254 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
255 bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
256 			unsigned len_mask);
257 unsigned long iov_iter_alignment(const struct iov_iter *i);
258 unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
259 void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov,
260 			unsigned long nr_segs, size_t count);
261 void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec *kvec,
262 			unsigned long nr_segs, size_t count);
263 void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
264 			unsigned long nr_segs, size_t count);
265 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
266 void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
267 		     loff_t start, size_t count);
268 ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
269 			size_t maxsize, unsigned maxpages, size_t *start);
270 ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages,
271 			size_t maxsize, size_t *start);
272 int iov_iter_npages(const struct iov_iter *i, int maxpages);
273 void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state);
274 
275 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
276 
iov_iter_count(const struct iov_iter * i)277 static 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  */
iov_iter_truncate(struct iov_iter * i,u64 count)288 static 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  */
iov_iter_reexpand(struct iov_iter * i,size_t count)304 static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
305 {
306 	i->count = count;
307 }
308 
309 static inline int
iov_iter_npages_cap(struct iov_iter * i,int maxpages,size_t max_bytes)310 iov_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, max_bytes);
318 	}
319 	npages = iov_iter_npages(i, maxpages);
320 	if (shorted)
321 		iov_iter_reexpand(i, iov_iter_count(i) + shorted);
322 
323 	return npages;
324 }
325 
326 struct 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);
329 ssize_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);
332 ssize_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);
335 int import_ubuf(int type, void __user *buf, size_t len, struct iov_iter *i);
336 
iov_iter_ubuf(struct iov_iter * i,unsigned int direction,void __user * buf,size_t count)337 static 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 
353 ssize_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  */
iov_iter_extract_will_pin(const struct iov_iter * iter)374 static inline bool iov_iter_extract_will_pin(const struct iov_iter *iter)
375 {
376 	return user_backed_iter(iter);
377 }
378 
379 struct sg_table;
380 ssize_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