1 /* 2 * Berkeley style UIO structures - Alan Cox 1994. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation; either version 7 * 2 of the License, or (at your option) any later version. 8 */ 9 #ifndef __LINUX_UIO_H 10 #define __LINUX_UIO_H 11 12 #include <linux/kernel.h> 13 #include <uapi/linux/uio.h> 14 15 struct page; 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 { 23 ITER_IOVEC = 0, 24 ITER_KVEC = 2, 25 ITER_BVEC = 4, 26 }; 27 28 struct iov_iter { 29 int type; 30 size_t iov_offset; 31 size_t count; 32 union { 33 const struct iovec *iov; 34 const struct bio_vec *bvec; 35 }; 36 unsigned long nr_segs; 37 }; 38 39 /* 40 * Total number of bytes covered by an iovec. 41 * 42 * NOTE that it is not safe to use this function until all the iovec's 43 * segment lengths have been validated. Because the individual lengths can 44 * overflow a size_t when added together. 45 */ 46 static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs) 47 { 48 unsigned long seg; 49 size_t ret = 0; 50 51 for (seg = 0; seg < nr_segs; seg++) 52 ret += iov[seg].iov_len; 53 return ret; 54 } 55 56 static inline struct iovec iov_iter_iovec(const struct iov_iter *iter) 57 { 58 return (struct iovec) { 59 .iov_base = iter->iov->iov_base + iter->iov_offset, 60 .iov_len = min(iter->count, 61 iter->iov->iov_len - iter->iov_offset), 62 }; 63 } 64 65 #define iov_for_each(iov, iter, start) \ 66 if (!((start).type & ITER_BVEC)) \ 67 for (iter = (start); \ 68 (iter).count && \ 69 ((iov = iov_iter_iovec(&(iter))), 1); \ 70 iov_iter_advance(&(iter), (iov).iov_len)) 71 72 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to); 73 74 size_t iov_iter_copy_from_user_atomic(struct page *page, 75 struct iov_iter *i, unsigned long offset, size_t bytes); 76 void iov_iter_advance(struct iov_iter *i, size_t bytes); 77 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes); 78 size_t iov_iter_single_seg_count(const struct iov_iter *i); 79 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, 80 struct iov_iter *i); 81 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes, 82 struct iov_iter *i); 83 size_t copy_to_iter(void *addr, size_t bytes, struct iov_iter *i); 84 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i); 85 size_t iov_iter_zero(size_t bytes, struct iov_iter *); 86 unsigned long iov_iter_alignment(const struct iov_iter *i); 87 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov, 88 unsigned long nr_segs, size_t count); 89 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages, 90 size_t maxsize, unsigned maxpages, size_t *start); 91 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages, 92 size_t maxsize, size_t *start); 93 int iov_iter_npages(const struct iov_iter *i, int maxpages); 94 95 static inline size_t iov_iter_count(struct iov_iter *i) 96 { 97 return i->count; 98 } 99 100 /* 101 * Cap the iov_iter by given limit; note that the second argument is 102 * *not* the new size - it's upper limit for such. Passing it a value 103 * greater than the amount of data in iov_iter is fine - it'll just do 104 * nothing in that case. 105 */ 106 static inline void iov_iter_truncate(struct iov_iter *i, u64 count) 107 { 108 /* 109 * count doesn't have to fit in size_t - comparison extends both 110 * operands to u64 here and any value that would be truncated by 111 * conversion in assignement is by definition greater than all 112 * values of size_t, including old i->count. 113 */ 114 if (i->count > count) 115 i->count = count; 116 } 117 118 /* 119 * reexpand a previously truncated iterator; count must be no more than how much 120 * we had shrunk it. 121 */ 122 static inline void iov_iter_reexpand(struct iov_iter *i, size_t count) 123 { 124 i->count = count; 125 } 126 127 int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len); 128 int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len); 129 int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov, 130 int offset, int len); 131 int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata, 132 int offset, int len); 133 134 #endif 135