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 struct pipe_inode_info;
  17
  18 struct kvec {
  19         void *iov_base; /* and that should *never* hold a userland pointer */
  20         size_t iov_len;
  21 };
  22
  23 enum {
  24         ITER_IOVEC = 0,
  25         ITER_KVEC = 2,
  26         ITER_BVEC = 4,
  27         ITER_PIPE = 8,
  28 };
  29
  30 struct iov_iter {
  31         int type;
  32         size_t iov_offset;
  33         size_t count;
  34         union {
  35                 const struct iovec *iov;
  36                 const struct kvec *kvec;
  37                 const struct bio_vec *bvec;
  38                 struct pipe_inode_info *pipe;
  39         };
  40         union {
  41                 unsigned long nr_segs;
  42                 int idx;
  43         };
  44 };
  45
  46 /*
  47  * Total number of bytes covered by an iovec.
  48  *
  49  * NOTE that it is not safe to use this function until all the iovec's
  50  * segment lengths have been validated.  Because the individual lengths can
  51  * overflow a size_t when added together.
  52  */
  53 static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
  54 {
  55         unsigned long seg;
  56         size_t ret = 0;
  57
  58         for (seg = 0; seg < nr_segs; seg++)
  59                 ret += iov[seg].iov_len;
  60         return ret;
  61 }
  62
  63 static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
  64 {
  65         return (struct iovec) {
  66                 .iov_base = iter->iov->iov_base + iter->iov_offset,
  67                 .iov_len = min(iter->count,
  68                                iter->iov->iov_len - iter->iov_offset),
  69         };
  70 }
  71
  72 #define iov_for_each(iov, iter, start)                          \
  73         if (!((start).type & (ITER_BVEC | ITER_PIPE)))          \
  74         for (iter = (start);                                    \
  75              (iter).count &&                                    \
  76              ((iov = iov_iter_iovec(&(iter))), 1);              \
  77              iov_iter_advance(&(iter), (iov).iov_len))
  78
  79 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  80
  81 size_t iov_iter_copy_from_user_atomic(struct page *page,
  82                 struct iov_iter *i, unsigned long offset, size_t bytes);
  83 void iov_iter_advance(struct iov_iter *i, size_t bytes);
  84 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
  85 size_t iov_iter_single_seg_count(const struct iov_iter *i);
  86 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
  87                          struct iov_iter *i);
  88 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
  89                          struct iov_iter *i);
  90 size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
  91 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
  92 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
  93 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
  94 unsigned long iov_iter_alignment(const struct iov_iter *i);
  95 unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
  96 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
  97                         unsigned long nr_segs, size_t count);
  98 void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
  99                         unsigned long nr_segs, size_t count);
 100 void iov_iter_bvec(struct iov_iter *i, int direction, const struct bio_vec *bvec,
 101                         unsigned long nr_segs, size_t count);
 102 void iov_iter_pipe(struct iov_iter *i, int direction, struct pipe_inode_info *pipe,
 103                         size_t count);
 104 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
 105                         size_t maxsize, unsigned maxpages, size_t *start);
 106 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
 107                         size_t maxsize, size_t *start);
 108 int iov_iter_npages(const struct iov_iter *i, int maxpages);
 109
 110 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
 111
 112 static inline size_t iov_iter_count(const struct iov_iter *i)
 113 {
 114         return i->count;
 115 }
 116
 117 static inline bool iter_is_iovec(const struct iov_iter *i)
 118 {
 119         return !(i->type & (ITER_BVEC | ITER_KVEC | ITER_PIPE));
 120 }
 121
 122 /*
 123  * Get one of READ or WRITE out of iter->type without any other flags OR'd in
 124  * with it.
 125  *
 126  * The ?: is just for type safety.
 127  */
 128 #define iov_iter_rw(i) ((0 ? (struct iov_iter *)0 : (i))->type & RW_MASK)
 129
 130 /*
 131  * Cap the iov_iter by given limit; note that the second argument is
 132  * *not* the new size - it's upper limit for such.  Passing it a value
 133  * greater than the amount of data in iov_iter is fine - it'll just do
 134  * nothing in that case.
 135  */
 136 static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
 137 {
 138         /*
 139          * count doesn't have to fit in size_t - comparison extends both
 140          * operands to u64 here and any value that would be truncated by
 141          * conversion in assignement is by definition greater than all
 142          * values of size_t, including old i->count.
 143          */
 144         if (i->count > count)
 145                 i->count = count;
 146 }
 147
 148 /*
 149  * reexpand a previously truncated iterator; count must be no more than how much
 150  * we had shrunk it.
 151  */
 152 static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 153 {
 154         i->count = count;
 155 }
 156 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 157 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 158
 159 int import_iovec(int type, const struct iovec __user * uvector,
 160                  unsigned nr_segs, unsigned fast_segs,
 161                  struct iovec **iov, struct iov_iter *i);
 162
 163 #ifdef CONFIG_COMPAT
 164 struct compat_iovec;
 165 int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
 166                  unsigned nr_segs, unsigned fast_segs,
 167                  struct iovec **iov, struct iov_iter *i);
 168 #endif
 169
 170 int import_single_range(int type, void __user *buf, size_t len,
 171                  struct iovec *iov, struct iov_iter *i);
 172
 173 #endif