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 <linux/thread_info.h>
  14 #include <uapi/linux/uio.h>
  15
  16 struct page;
  17 struct pipe_inode_info;
  18
  19 struct kvec {
  20         void *iov_base; /* and that should *never* hold a userland pointer */
  21         size_t iov_len;
  22 };
  23
  24 enum {
  25         ITER_IOVEC = 0,
  26         ITER_KVEC = 2,
  27         ITER_BVEC = 4,
  28         ITER_PIPE = 8,
  29 };
  30
  31 struct iov_iter {
  32         int type;
  33         size_t iov_offset;
  34         size_t count;
  35         union {
  36                 const struct iovec *iov;
  37                 const struct kvec *kvec;
  38                 const struct bio_vec *bvec;
  39                 struct pipe_inode_info *pipe;
  40         };
  41         union {
  42                 unsigned long nr_segs;
  43                 struct {
  44                         int idx;
  45                         int start_idx;
  46                 };
  47         };
  48 };
  49
  50 /*
  51  * Total number of bytes covered by an iovec.
  52  *
  53  * NOTE that it is not safe to use this function until all the iovec's
  54  * segment lengths have been validated.  Because the individual lengths can
  55  * overflow a size_t when added together.
  56  */
  57 static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
  58 {
  59         unsigned long seg;
  60         size_t ret = 0;
  61
  62         for (seg = 0; seg < nr_segs; seg++)
  63                 ret += iov[seg].iov_len;
  64         return ret;
  65 }
  66
  67 static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
  68 {
  69         return (struct iovec) {
  70                 .iov_base = iter->iov->iov_base + iter->iov_offset,
  71                 .iov_len = min(iter->count,
  72                                iter->iov->iov_len - iter->iov_offset),
  73         };
  74 }
  75
  76 #define iov_for_each(iov, iter, start)                          \
  77         if (!((start).type & (ITER_BVEC | ITER_PIPE)))          \
  78         for (iter = (start);                                    \
  79              (iter).count &&                                    \
  80              ((iov = iov_iter_iovec(&(iter))), 1);              \
  81              iov_iter_advance(&(iter), (iov).iov_len))
  82
  83 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  84
  85 size_t iov_iter_copy_from_user_atomic(struct page *page,
  86                 struct iov_iter *i, unsigned long offset, size_t bytes);
  87 void iov_iter_advance(struct iov_iter *i, size_t bytes);
  88 void iov_iter_revert(struct iov_iter *i, size_t bytes);
  89 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
  90 size_t iov_iter_single_seg_count(const struct iov_iter *i);
  91 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
  92                          struct iov_iter *i);
  93 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
  94                          struct iov_iter *i);
  95
  96 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
  97 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
  98 bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i);
  99 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
 100 bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i);
 101
 102 static __always_inline __must_check
 103 size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 104 {
 105         if (unlikely(!check_copy_size(addr, bytes, true)))
 106                 return 0;
 107         else
 108                 return _copy_to_iter(addr, bytes, i);
 109 }
 110
 111 static __always_inline __must_check
 112 size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 113 {
 114         if (unlikely(!check_copy_size(addr, bytes, false)))
 115                 return 0;
 116         else
 117                 return _copy_from_iter(addr, bytes, i);
 118 }
 119
 120 static __always_inline __must_check
 121 bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 122 {
 123         if (unlikely(!check_copy_size(addr, bytes, false)))
 124                 return false;
 125         else
 126                 return _copy_from_iter_full(addr, bytes, i);
 127 }
 128
 129 static __always_inline __must_check
 130 size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 131 {
 132         if (unlikely(!check_copy_size(addr, bytes, false)))
 133                 return 0;
 134         else
 135                 return _copy_from_iter_nocache(addr, bytes, i);
 136 }
 137
 138 static __always_inline __must_check
 139 bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
 140 {
 141         if (unlikely(!check_copy_size(addr, bytes, false)))
 142                 return false;
 143         else
 144                 return _copy_from_iter_full_nocache(addr, bytes, i);
 145 }
 146
 147 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 148 /*
 149  * Note, users like pmem that depend on the stricter semantics of
 150  * copy_from_iter_flushcache() than copy_from_iter_nocache() must check for
 151  * IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) before assuming that the
 152  * destination is flushed from the cache on return.
 153  */
 154 size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
 155 #else
 156 #define _copy_from_iter_flushcache _copy_from_iter_nocache
 157 #endif
 158
 159 static __always_inline __must_check
 160 size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 161 {
 162         if (unlikely(!check_copy_size(addr, bytes, false)))
 163                 return 0;
 164         else
 165                 return _copy_from_iter_flushcache(addr, bytes, i);
 166 }
 167
 168 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
 169 unsigned long iov_iter_alignment(const struct iov_iter *i);
 170 unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
 171 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
 172                         unsigned long nr_segs, size_t count);
 173 void iov_iter_kvec(struct iov_iter *i, int direction, const struct kvec *kvec,
 174                         unsigned long nr_segs, size_t count);
 175 void iov_iter_bvec(struct iov_iter *i, int direction, const struct bio_vec *bvec,
 176                         unsigned long nr_segs, size_t count);
 177 void iov_iter_pipe(struct iov_iter *i, int direction, struct pipe_inode_info *pipe,
 178                         size_t count);
 179 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
 180                         size_t maxsize, unsigned maxpages, size_t *start);
 181 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
 182                         size_t maxsize, size_t *start);
 183 int iov_iter_npages(const struct iov_iter *i, int maxpages);
 184
 185 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
 186
 187 static inline size_t iov_iter_count(const struct iov_iter *i)
 188 {
 189         return i->count;
 190 }
 191
 192 static inline bool iter_is_iovec(const struct iov_iter *i)
 193 {
 194         return !(i->type & (ITER_BVEC | ITER_KVEC | ITER_PIPE));
 195 }
 196
 197 /*
 198  * Get one of READ or WRITE out of iter->type without any other flags OR'd in
 199  * with it.
 200  *
 201  * The ?: is just for type safety.
 202  */
 203 #define iov_iter_rw(i) ((0 ? (struct iov_iter *)0 : (i))->type & (READ | WRITE))
 204
 205 /*
 206  * Cap the iov_iter by given limit; note that the second argument is
 207  * *not* the new size - it's upper limit for such.  Passing it a value
 208  * greater than the amount of data in iov_iter is fine - it'll just do
 209  * nothing in that case.
 210  */
 211 static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
 212 {
 213         /*
 214          * count doesn't have to fit in size_t - comparison extends both
 215          * operands to u64 here and any value that would be truncated by
 216          * conversion in assignement is by definition greater than all
 217          * values of size_t, including old i->count.
 218          */
 219         if (i->count > count)
 220                 i->count = count;
 221 }
 222
 223 /*
 224  * reexpand a previously truncated iterator; count must be no more than how much
 225  * we had shrunk it.
 226  */
 227 static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 228 {
 229         i->count = count;
 230 }
 231 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 232 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 233 bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 234
 235 int import_iovec(int type, const struct iovec __user * uvector,
 236                  unsigned nr_segs, unsigned fast_segs,
 237                  struct iovec **iov, struct iov_iter *i);
 238
 239 #ifdef CONFIG_COMPAT
 240 struct compat_iovec;
 241 int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
 242                  unsigned nr_segs, unsigned fast_segs,
 243                  struct iovec **iov, struct iov_iter *i);
 244 #endif
 245
 246 int import_single_range(int type, void __user *buf, size_t len,
 247                  struct iovec *iov, struct iov_iter *i);
 248
 249 #endif