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 struct iov_iter {
  23         const struct iovec *iov;
  24         unsigned long nr_segs;
  25         size_t iov_offset;
  26         size_t count;
  27 };
  28
  29 /*
  30  * Total number of bytes covered by an iovec.
  31  *
  32  * NOTE that it is not safe to use this function until all the iovec's
  33  * segment lengths have been validated.  Because the individual lengths can
  34  * overflow a size_t when added together.
  35  */
  36 static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
  37 {
  38         unsigned long seg;
  39         size_t ret = 0;
  40
  41         for (seg = 0; seg < nr_segs; seg++)
  42                 ret += iov[seg].iov_len;
  43         return ret;
  44 }
  45
  46 static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
  47 {
  48         return (struct iovec) {
  49                 .iov_base = iter->iov->iov_base + iter->iov_offset,
  50                 .iov_len = min(iter->count,
  51                                iter->iov->iov_len - iter->iov_offset),
  52         };
  53 }
  54
  55 #define iov_for_each(iov, iter, start)                          \
  56         for (iter = (start);                                    \
  57              (iter).count &&                                    \
  58              ((iov = iov_iter_iovec(&(iter))), 1);              \
  59              iov_iter_advance(&(iter), (iov).iov_len))
  60
  61 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  62
  63 size_t iov_iter_copy_from_user_atomic(struct page *page,
  64                 struct iov_iter *i, unsigned long offset, size_t bytes);
  65 size_t iov_iter_copy_from_user(struct page *page,
  66                 struct iov_iter *i, unsigned long offset, size_t bytes);
  67 void iov_iter_advance(struct iov_iter *i, size_t bytes);
  68 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
  69 size_t iov_iter_single_seg_count(const struct iov_iter *i);
  70 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
  71                          struct iov_iter *i);
  72
  73 static inline void iov_iter_init(struct iov_iter *i,
  74                         const struct iovec *iov, unsigned long nr_segs,
  75                         size_t count, size_t written)
  76 {
  77         i->iov = iov;
  78         i->nr_segs = nr_segs;
  79         i->iov_offset = 0;
  80         i->count = count + written;
  81
  82         iov_iter_advance(i, written);
  83 }
  84
  85 static inline size_t iov_iter_count(struct iov_iter *i)
  86 {
  87         return i->count;
  88 }
  89
  90 int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
  91 int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len);
  92
  93 #endif