/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 *      Berkeley style UIO structures   -       Alan Cox 1994.
 */
#ifndef __LINUX_UIO_H
#define __LINUX_UIO_H

#include <linux/kernel.h>
#include <linux/thread_info.h>
#include <linux/mm_types.h>
#include <uapi/linux/uio.h>

struct page;
struct pipe_inode_info;

struct kvec {
        void *iov_base; /* and that should *never* hold a userland pointer */
        size_t iov_len;
};

enum iter_type {
        /* iter types */
        ITER_IOVEC,
        ITER_KVEC,
        ITER_BVEC,
        ITER_PIPE,
        ITER_XARRAY,
        ITER_DISCARD,
};

struct iov_iter_state {
        size_t iov_offset;
        size_t count;
        unsigned long nr_segs;
};

struct iov_iter {
        u8 iter_type;
        bool nofault;
        bool data_source;
        size_t iov_offset;
        size_t count;
        union {
                const struct iovec *iov;
                const struct kvec *kvec;
                const struct bio_vec *bvec;
                struct xarray *xarray;
                struct pipe_inode_info *pipe;
        };
        union {
                unsigned long nr_segs;
                struct {
                        unsigned int head;
                        unsigned int start_head;
                };
                loff_t xarray_start;
        };
};

static inline enum iter_type iov_iter_type(const struct iov_iter *i)
{
        return i->iter_type;
}

static inline void iov_iter_save_state(struct iov_iter *iter,
                                       struct iov_iter_state *state)
{
        state->iov_offset = iter->iov_offset;
        state->count = iter->count;
        state->nr_segs = iter->nr_segs;
}

static inline bool iter_is_iovec(const struct iov_iter *i)
{
        return iov_iter_type(i) == ITER_IOVEC;
}

static inline bool iov_iter_is_kvec(const struct iov_iter *i)
{
        return iov_iter_type(i) == ITER_KVEC;
}

static inline bool iov_iter_is_bvec(const struct iov_iter *i)
{
        return iov_iter_type(i) == ITER_BVEC;
}

static inline bool iov_iter_is_pipe(const struct iov_iter *i)
{
        return iov_iter_type(i) == ITER_PIPE;
}

static inline bool iov_iter_is_discard(const struct iov_iter *i)
{
        return iov_iter_type(i) == ITER_DISCARD;
}

static inline bool iov_iter_is_xarray(const struct iov_iter *i)
{
        return iov_iter_type(i) == ITER_XARRAY;
}

static inline unsigned char iov_iter_rw(const struct iov_iter *i)
{
        return i->data_source ? WRITE : READ;
}

/*
 * Total number of bytes covered by an iovec.
 *
 * NOTE that it is not safe to use this function until all the iovec's
 * segment lengths have been validated.  Because the individual lengths can
 * overflow a size_t when added together.
 */
static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
{
        unsigned long seg;
        size_t ret = 0;

        for (seg = 0; seg < nr_segs; seg++)
                ret += iov[seg].iov_len;
        return ret;
}

static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
{
        return (struct iovec) {
                .iov_base = iter->iov->iov_base + iter->iov_offset,
                .iov_len = min(iter->count,
                               iter->iov->iov_len - iter->iov_offset),
        };
}

size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,
                                  size_t bytes, struct iov_iter *i);
void iov_iter_advance(struct iov_iter *i, size_t bytes);
void iov_iter_revert(struct iov_iter *i, size_t bytes);
size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t bytes);
size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t bytes);
size_t iov_iter_single_seg_count(const struct iov_iter *i);
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i);
size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i);

size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);

static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset,
                size_t bytes, struct iov_iter *i)
{
        return copy_page_to_iter(&folio->page, offset, bytes, i);
}

static __always_inline __must_check
size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
        if (unlikely(!check_copy_size(addr, bytes, true)))
                return 0;
        else
                return _copy_to_iter(addr, bytes, i);
}

static __always_inline __must_check
size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
        if (unlikely(!check_copy_size(addr, bytes, false)))
                return 0;
        else
                return _copy_from_iter(addr, bytes, i);
}

static __always_inline __must_check
bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
{
        size_t copied = copy_from_iter(addr, bytes, i);
        if (likely(copied == bytes))
                return true;
        iov_iter_revert(i, copied);
        return false;
}

static __always_inline __must_check
size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
{
        if (unlikely(!check_copy_size(addr, bytes, false)))
                return 0;
        else
                return _copy_from_iter_nocache(addr, bytes, i);
}

static __always_inline __must_check
bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
{
        size_t copied = copy_from_iter_nocache(addr, bytes, i);
        if (likely(copied == bytes))
                return true;
        iov_iter_revert(i, copied);
        return false;
}

#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
/*
 * Note, users like pmem that depend on the stricter semantics of
 * _copy_from_iter_flushcache() than _copy_from_iter_nocache() must check for
 * IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) before assuming that the
 * destination is flushed from the cache on return.
 */
size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
#else
#define _copy_from_iter_flushcache _copy_from_iter_nocache
#endif

#ifdef CONFIG_ARCH_HAS_COPY_MC
size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
#else
#define _copy_mc_to_iter _copy_to_iter
#endif

size_t iov_iter_zero(size_t bytes, struct iov_iter *);
unsigned long iov_iter_alignment(const struct iov_iter *i);
unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov,
                        unsigned long nr_segs, size_t count);
void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec *kvec,
                        unsigned long nr_segs, size_t count);
void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
                        unsigned long nr_segs, size_t count);
void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode_info *pipe,
                        size_t count);
void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
                     loff_t start, size_t count);
ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
                        size_t maxsize, unsigned maxpages, size_t *start);
ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
                        size_t maxsize, size_t *start);
int iov_iter_npages(const struct iov_iter *i, int maxpages);
void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state);

const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);

static inline size_t iov_iter_count(const struct iov_iter *i)
{
        return i->count;
}

/*
 * Cap the iov_iter by given limit; note that the second argument is
 * *not* the new size - it's upper limit for such.  Passing it a value
 * greater than the amount of data in iov_iter is fine - it'll just do
 * nothing in that case.
 */
static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
{
        /*
         * count doesn't have to fit in size_t - comparison extends both
         * operands to u64 here and any value that would be truncated by
         * conversion in assignement is by definition greater than all
         * values of size_t, including old i->count.
         */
        if (i->count > count)
                i->count = count;
}

/*
 * reexpand a previously truncated iterator; count must be no more than how much
 * we had shrunk it.
 */
static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
{
        i->count = count;
}

static inline int
iov_iter_npages_cap(struct iov_iter *i, int maxpages, size_t max_bytes)
{
        size_t shorted = 0;
        int npages;

        if (iov_iter_count(i) > max_bytes) {
                shorted = iov_iter_count(i) - max_bytes;
                iov_iter_truncate(i, max_bytes);
        }
        npages = iov_iter_npages(i, INT_MAX);
        if (shorted)
                iov_iter_reexpand(i, iov_iter_count(i) + shorted);

        return npages;
}

struct csum_state {
        __wsum csum;
        size_t off;
};

size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csstate, struct iov_iter *i);
size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);

static __always_inline __must_check
bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
                                  __wsum *csum, struct iov_iter *i)
{
        size_t copied = csum_and_copy_from_iter(addr, bytes, csum, i);
        if (likely(copied == bytes))
                return true;
        iov_iter_revert(i, copied);
        return false;
}
size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
                struct iov_iter *i);

struct iovec *iovec_from_user(const struct iovec __user *uvector,
                unsigned long nr_segs, unsigned long fast_segs,
                struct iovec *fast_iov, bool compat);
ssize_t import_iovec(int type, const struct iovec __user *uvec,
                 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
                 struct iov_iter *i);
ssize_t __import_iovec(int type, const struct iovec __user *uvec,
                 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
                 struct iov_iter *i, bool compat);
int import_single_range(int type, void __user *buf, size_t len,
                 struct iovec *iov, struct iov_iter *i);

#endif