LXR linux/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
  15struct page;
  16
  17struct kvec {
  18        void *iov_base; /* and that should *never* hold a userland pointer */
  19        size_t iov_len;
  20};
  21
  22enum {
  23        ITER_IOVEC = 0,
  24        ITER_KVEC = 2,
  25        ITER_BVEC = 4,
  26};
  27
  28struct 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 */
  46static 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
  56static 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
  72unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  73
  74size_t iov_iter_copy_from_user_atomic(struct page *page,
  75                struct iov_iter *i, unsigned long offset, size_t bytes);
  76void iov_iter_advance(struct iov_iter *i, size_t bytes);
  77int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
  78size_t iov_iter_single_seg_count(const struct iov_iter *i);
  79size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
  80                         struct iov_iter *i);
  81size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
  82                         struct iov_iter *i);
  83unsigned long iov_iter_alignment(const struct iov_iter *i);
  84void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
  85                        unsigned long nr_segs, size_t count);
  86ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
  87                        size_t maxsize, size_t *start);
  88ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
  89                        size_t maxsize, size_t *start);
  90int iov_iter_npages(const struct iov_iter *i, int maxpages);
  91
  92static inline size_t iov_iter_count(struct iov_iter *i)
  93{
  94        return i->count;
  95}
  96
  97/*
  98 * Cap the iov_iter by given limit; note that the second argument is
  99 * *not* the new size - it's upper limit for such.  Passing it a value
 100 * greater than the amount of data in iov_iter is fine - it'll just do
 101 * nothing in that case.
 102 */
 103static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
 104{
 105        /*
 106         * count doesn't have to fit in size_t - comparison extends both
 107         * operands to u64 here and any value that would be truncated by
 108         * conversion in assignement is by definition greater than all
 109         * values of size_t, including old i->count.
 110         */
 111        if (i->count > count)
 112                i->count = count;
 113}
 114
 115/*
 116 * reexpand a previously truncated iterator; count must be no more than how much
 117 * we had shrunk it.
 118 */
 119static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 120{
 121        i->count = count;
 122}
 123
 124int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
 125int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len);
 126int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
 127                        int offset, int len);
 128int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,
 129                      int offset, int len);
 130
 131#endif
 132