include/linux/uio.h

   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 kvec *kvec;
  35                 const struct bio_vec *bvec;
  36         };
  37         unsigned long nr_segs;
  38 };
  39
  40 /*
  41  * Total number of bytes covered by an iovec.
  42  *
  43  * NOTE that it is not safe to use this function until all the iovec's
  44  * segment lengths have been validated.  Because the individual lengths can
  45  * overflow a size_t when added together.
  46  */
  47 static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
  48 {
  49         unsigned long seg;
  50         size_t ret = 0;
  51
  52         for (seg = 0; seg < nr_segs; seg++)
  53                 ret += iov[seg].iov_len;
  54         return ret;
  55 }
  56
  57 static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
  58 {
  59         return (struct iovec) {
  60                 .iov_base = iter->iov->iov_base + iter->iov_offset,
  61                 .iov_len = min(iter->count,
  62                                iter->iov->iov_len - iter->iov_offset),
  63         };
  64 }
  65
  66 #define iov_for_each(iov, iter, start)                          \
  67         if (!((start).type & ITER_BVEC))                        \
  68         for (iter = (start);                                    \
  69              (iter).count &&                                    \
  70              ((iov = iov_iter_iovec(&(iter))), 1);              \
  71              iov_iter_advance(&(iter), (iov).iov_len))
  72
  73 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  74
  75 size_t iov_iter_copy_from_user_atomic(struct page *page,
  76                 struct iov_iter *i, unsigned long offset, size_t bytes);
  77 void iov_iter_advance(struct iov_iter *i, size_t bytes);
  78 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
  79 size_t iov_iter_single_seg_count(const struct iov_iter *i);
  80 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
  81                          struct iov_iter *i);
  82 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
  83                          struct iov_iter *i);
  84 size_t copy_to_iter(void *addr, size_t bytes, struct iov_iter *i);
  85 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
  86 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
  87 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
  88 unsigned long iov_iter_alignment(const struct iov_iter *i);
  89 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
  90                         unsigned long nr_segs, size_t count);
  91 void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
  92                         unsigned long nr_segs, size_t count);
  93 void iov_iter_bvec(struct iov_iter *i, int direction, const struct bio_vec *bvec,
  94                         unsigned long nr_segs, size_t count);
  95 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
  96                         size_t maxsize, unsigned maxpages, size_t *start);
  97 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
  98                         size_t maxsize, size_t *start);
  99 int iov_iter_npages(const struct iov_iter *i, int maxpages);
 100
 101 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
 102
 103 static inline size_t iov_iter_count(struct iov_iter *i)
 104 {
 105         return i->count;
 106 }
 107
 108 static inline bool iter_is_iovec(struct iov_iter *i)
 109 {
 110         return !(i->type & (ITER_BVEC | ITER_KVEC));
 111 }
 112
 113 /*
 114  * Cap the iov_iter by given limit; note that the second argument is
 115  * *not* the new size - it's upper limit for such.  Passing it a value
 116  * greater than the amount of data in iov_iter is fine - it'll just do
 117  * nothing in that case.
 118  */
 119 static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
 120 {
 121         /*
 122          * count doesn't have to fit in size_t - comparison extends both
 123          * operands to u64 here and any value that would be truncated by
 124          * conversion in assignement is by definition greater than all
 125          * values of size_t, including old i->count.
 126          */
 127         if (i->count > count)
 128                 i->count = count;
 129 }
 130
 131 /*
 132  * reexpand a previously truncated iterator; count must be no more than how much
 133  * we had shrunk it.
 134  */
 135 static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 136 {
 137         i->count = count;
 138 }
 139 size_t csum_and_copy_to_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 140 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 141
 142 #endif