// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/bvec.h>
#include <linux/fault-inject-usercopy.h>
#include <linux/uio.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/splice.h>
#include <linux/compat.h>
#include <linux/scatterlist.h>
#include <linux/instrumented.h>
#include <linux/iov_iter.h>
static __always_inline
size_t copy_to_user_iter(void __user *iter_to, size_t progress,
size_t len, void *from, void *priv2)
{
if (should_fail_usercopy())
return len;
if (access_ok(iter_to, len)) {
from += progress;
instrument_copy_to_user(iter_to, from, len);
len = raw_copy_to_user(iter_to, from, len);
}
return len;
}
static __always_inline
size_t copy_to_user_iter_nofault(void __user *iter_to, size_t progress,
size_t len, void *from, void *priv2)
{
ssize_t res;
if (should_fail_usercopy())
return len;
from += progress;
res = copy_to_user_nofault(iter_to, from, len);
return res < 0 ? len : res;
}
static __always_inline
size_t copy_from_user_iter(void __user *iter_from, size_t progress,
size_t len, void *to, void *priv2)
{
size_t res = len;
if (should_fail_usercopy())
return len;
if (access_ok(iter_from, len)) {
to += progress;
instrument_copy_from_user_before(to, iter_from, len);
res = raw_copy_from_user(to, iter_from, len);
instrument_copy_from_user_after(to, iter_from, len, res);
}
return res;
}
static __always_inline
size_t memcpy_to_iter(void *iter_to, size_t progress,
size_t len, void *from, void *priv2)
{
memcpy(iter_to, from + progress, len);
return 0;
}
static __always_inline
size_t memcpy_from_iter(void *iter_from, size_t progress,
size_t len, void *to, void *priv2)
{
memcpy(to + progress, iter_from, len);
return 0;
}
/*
* fault_in_iov_iter_readable - fault in iov iterator for reading
* @i: iterator
* @size: maximum length
*
* Fault in one or more iovecs of the given iov_iter, to a maximum length of
* @size. For each iovec, fault in each page that constitutes the iovec.
*
* Returns the number of bytes not faulted in (like copy_to_user() and
* copy_from_user()).
*
* Always returns 0 for non-userspace iterators.
*/
size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size)
{
if (iter_is_ubuf(i)) {
size_t n = min(size, iov_iter_count(i));
n -= fault_in_readable(i->ubuf + i->iov_offset, n);
return size - n;
} else if (iter_is_iovec(i)) {
size_t count = min(size, iov_iter_count(i));
const struct iovec *p;
size_t skip;
size -= count;
for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) {
size_t len = min(count, p->iov_len - skip);
size_t ret;
if (unlikely(!len))
continue;
ret = fault_in_readable(p->iov_base + skip, len);
count -= len - ret;
if (ret)
break;
}
return count + size;
}
return 0;
}
EXPORT_SYMBOL(fault_in_iov_iter_readable);
/*
* fault_in_iov_iter_writeable - fault in iov iterator for writing
* @i: iterator
* @size: maximum length
*
* Faults in the iterator using get_user_pages(), i.e., without triggering
* hardware page faults. This is primarily useful when we already know that
* some or all of the pages in @i aren't in memory.
*
* Returns the number of bytes not faulted in, like copy_to_user() and
* copy_from_user().
*
* Always returns 0 for non-user-space iterators.
*/
size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size)
{
if (iter_is_ubuf(i)) {
size_t n = min(size, iov_iter_count(i));
n -= fault_in_safe_writeable(i->ubuf + i->iov_offset, n);
return size - n;
} else if (iter_is_iovec(i)) {
size_t count = min(size, iov_iter_count(i));
const struct iovec *p;
size_t skip;
size -= count;
for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) {
size_t len = min(count, p->iov_len - skip);
size_t ret;
if (unlikely(!len))
continue;
ret = fault_in_safe_writeable(p->iov_base + skip, len);
count -= len - ret;
if (ret)
break;
}
return count + size;
}
return 0;
}
EXPORT_SYMBOL(fault_in_iov_iter_writeable);
void iov_iter_init(struct iov_iter *i, unsigned int direction,
const struct iovec *iov, unsigned long nr_segs,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter) {
.iter_type = ITER_IOVEC,
.nofault = false,
.data_source = direction,
.__iov = iov,
.nr_segs = nr_segs,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_init);
size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(i->data_source))
return 0;
if (user_backed_iter(i))
might_fault();
return iterate_and_advance(i, bytes, (void *)addr,
copy_to_user_iter, memcpy_to_iter);
}
EXPORT_SYMBOL(_copy_to_iter);
#ifdef CONFIG_ARCH_HAS_COPY_MC
static __always_inline
size_t copy_to_user_iter_mc(void __user *iter_to, size_t progress,
size_t len, void *from, void *priv2)
{
if (access_ok(iter_to, len)) {
from += progress;
instrument_copy_to_user(iter_to, from, len);
len = copy_mc_to_user(iter_to, from, len);
}
return len;
}
static __always_inline
size_t memcpy_to_iter_mc(void *iter_to, size_t progress,
size_t len, void *from, void *priv2)
{
return copy_mc_to_kernel(iter_to, from + progress, len);
}
/**
* _copy_mc_to_iter - copy to iter with source memory error exception handling
* @addr: source kernel address
* @bytes: total transfer length
* @i: destination iterator
*
* The pmem driver deploys this for the dax operation
* (dax_copy_to_iter()) for dax reads (bypass page-cache and the
* block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
* successfully copied.
*
* The main differences between this and typical _copy_to_iter().
*
* * Typical tail/residue handling after a fault retries the copy
* byte-by-byte until the fault happens again. Re-triggering machine
* checks is potentially fatal so the implementation uses source
* alignment and poison alignment assumptions to avoid re-triggering
* hardware exceptions.
*
* * ITER_KVEC and ITER_BVEC can return short copies. Compare to
* copy_to_iter() where only ITER_IOVEC attempts might return a short copy.
*
* Return: number of bytes copied (may be %0)
*/
size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(i->data_source))
return 0;
if (user_backed_iter(i))
might_fault();
return iterate_and_advance(i, bytes, (void *)addr,
copy_to_user_iter_mc, memcpy_to_iter_mc);
}
EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
#endif /* CONFIG_ARCH_HAS_COPY_MC */
static __always_inline
size_t __copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
return iterate_and_advance(i, bytes, addr,
copy_from_user_iter, memcpy_from_iter);
}
size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(!i->data_source))
return 0;
if (user_backed_iter(i))
might_fault();
return __copy_from_iter(addr, bytes, i);
}
EXPORT_SYMBOL(_copy_from_iter);
static __always_inline
size_t copy_from_user_iter_nocache(void __user *iter_from, size_t progress,
size_t len, void *to, void *priv2)
{
return __copy_from_user_inatomic_nocache(to + progress, iter_from, len);
}
size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(!i->data_source))
return 0;
return iterate_and_advance(i, bytes, addr,
copy_from_user_iter_nocache,
memcpy_from_iter);
}
EXPORT_SYMBOL(_copy_from_iter_nocache);
#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
static __always_inline
size_t copy_from_user_iter_flushcache(void __user *iter_from, size_t progress,
size_t len, void *to, void *priv2)
{
return __copy_from_user_flushcache(to + progress, iter_from, len);
}
static __always_inline
size_t memcpy_from_iter_flushcache(void *iter_from, size_t progress,
size_t len, void *to, void *priv2)
{
memcpy_flushcache(to + progress, iter_from, len);
return 0;
}
/**
* _copy_from_iter_flushcache - write destination through cpu cache
* @addr: destination kernel address
* @bytes: total transfer length
* @i: source iterator
*
* The pmem driver arranges for filesystem-dax to use this facility via
* dax_copy_from_iter() for ensuring that writes to persistent memory
* are flushed through the CPU cache. It is differentiated from
* _copy_from_iter_nocache() in that guarantees all data is flushed for
* all iterator types. The _copy_from_iter_nocache() only attempts to
* bypass the cache for the ITER_IOVEC case, and on some archs may use
* instructions that strand dirty-data in the cache.
*
* Return: number of bytes copied (may be %0)
*/
size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(!i->data_source))
return 0;
return iterate_and_advance(i, bytes, addr,
copy_from_user_iter_flushcache,
memcpy_from_iter_flushcache);
}
EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
#endif
static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
{
struct page *head;
size_t v = n + offset;
/*
* The general case needs to access the page order in order
* to compute the page size.
* However, we mostly deal with order-0 pages and thus can
* avoid a possible cache line miss for requests that fit all
* page orders.
*/
if (n <= v && v <= PAGE_SIZE)
return true;
head = compound_head(page);
v += (page - head) << PAGE_SHIFT;
if (WARN_ON(n > v || v > page_size(head)))
return false;
return true;
}
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t res = 0;
if (!page_copy_sane(page, offset, bytes))
return 0;
if (WARN_ON_ONCE(i->data_source))
return 0;
page += offset / PAGE_SIZE; // first subpage
offset %= PAGE_SIZE;
while (1) {
void *kaddr = kmap_local_page(page);
size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
n = _copy_to_iter(kaddr + offset, n, i);
kunmap_local(kaddr);
res += n;
bytes -= n;
if (!bytes || !n)
break;
offset += n;
if (offset == PAGE_SIZE) {
page++;
offset = 0;
}
}
return res;
}
EXPORT_SYMBOL(copy_page_to_iter);
size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, size_t bytes,
struct iov_iter *i)
{
size_t res = 0;
if (!page_copy_sane(page, offset, bytes))
return 0;
if (WARN_ON_ONCE(i->data_source))
return 0;
page += offset / PAGE_SIZE; // first subpage
offset %= PAGE_SIZE;
while (1) {
void *kaddr = kmap_local_page(page);
size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
n = iterate_and_advance(i, n, kaddr + offset,
copy_to_user_iter_nofault,
memcpy_to_iter);
kunmap_local(kaddr);
res += n;
bytes -= n;
if (!bytes || !n)
break;
offset += n;
if (offset == PAGE_SIZE) {
page++;
offset = 0;
}
}
return res;
}
EXPORT_SYMBOL(copy_page_to_iter_nofault);
size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t res = 0;
if (!page_copy_sane(page, offset, bytes))
return 0;
page += offset / PAGE_SIZE; // first subpage
offset %= PAGE_SIZE;
while (1) {
void *kaddr = kmap_local_page(page);
size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
n = _copy_from_iter(kaddr + offset, n, i);
kunmap_local(kaddr);
res += n;
bytes -= n;
if (!bytes || !n)
break;
offset += n;
if (offset == PAGE_SIZE) {
page++;
offset = 0;
}
}
return res;
}
EXPORT_SYMBOL(copy_page_from_iter);
static __always_inline
size_t zero_to_user_iter(void __user *iter_to, size_t progress,
size_t len, void *priv, void *priv2)
{
return clear_user(iter_to, len);
}
static __always_inline
size_t zero_to_iter(void *iter_to, size_t progress,
size_t len, void *priv, void *priv2)
{
memset(iter_to, 0, len);
return 0;
}
size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
{
return iterate_and_advance(i, bytes, NULL,
zero_to_user_iter, zero_to_iter);
}
EXPORT_SYMBOL(iov_iter_zero);
size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
size_t bytes, struct iov_iter *i)
{
size_t n, copied = 0;
if (!page_copy_sane(page, offset, bytes))
return 0;
if (WARN_ON_ONCE(!i->data_source))
return 0;
do {
char *p;
n = bytes - copied;
if (PageHighMem(page)) {
page += offset / PAGE_SIZE;
offset %= PAGE_SIZE;
n = min_t(size_t, n, PAGE_SIZE - offset);
}
p = kmap_atomic(page) + offset;
n = __copy_from_iter(p, n, i);
kunmap_atomic(p);
copied += n;
offset += n;
} while (PageHighMem(page) && copied != bytes && n > 0);
return copied;
}
EXPORT_SYMBOL(copy_page_from_iter_atomic);
static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
{
const struct bio_vec *bvec, *end;
if (!i->count)
return;
i->count -= size;
size += i->iov_offset;
for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) {
if (likely(size < bvec->bv_len))
break;
size -= bvec->bv_len;
}
i->iov_offset = size;
i->nr_segs -= bvec - i->bvec;
i->bvec = bvec;
}
static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
{
const struct iovec *iov, *end;
if (!i->count)
return;
i->count -= size;
size += i->iov_offset; // from beginning of current segment
for (iov = iter_iov(i), end = iov + i->nr_segs; iov < end; iov++) {
if (likely(size < iov->iov_len))
break;
size -= iov->iov_len;
}
i->iov_offset = size;
i->nr_segs -= iov - iter_iov(i);
i->__iov = iov;
}
static void iov_iter_folioq_advance(struct iov_iter *i, size_t size)
{
const struct folio_queue *folioq = i->folioq;
unsigned int slot = i->folioq_slot;
if (!i->count)
return;
i->count -= size;
if (slot >= folioq_nr_slots(folioq)) {
folioq = folioq->next;
slot = 0;
}
size += i->iov_offset; /* From beginning of current segment. */
do {
size_t fsize = folioq_folio_size(folioq, slot);
if (likely(size < fsize))
break;
size -= fsize;
slot++;
if (slot >= folioq_nr_slots(folioq) && folioq->next) {
folioq = folioq->next;
slot = 0;
}
} while (size);
i->iov_offset = size;
i->folioq_slot = slot;
i->folioq = folioq;
}
void iov_iter_advance(struct iov_iter *i, size_t size)
{
if (unlikely(i->count < size))
size = i->count;
if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) {
i->iov_offset += size;
i->count -= size;
} else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
/* iovec and kvec have identical layouts */
iov_iter_iovec_advance(i, size);
} else if (iov_iter_is_bvec(i)) {
iov_iter_bvec_advance(i, size);
} else if (iov_iter_is_folioq(i)) {
iov_iter_folioq_advance(i, size);
} else if (iov_iter_is_discard(i)) {
i->count -= size;
}
}
EXPORT_SYMBOL(iov_iter_advance);
static void iov_iter_folioq_revert(struct iov_iter *i, size_t unroll)
{
const struct folio_queue *folioq = i->folioq;
unsigned int slot = i->folioq_slot;
for (;;) {
size_t fsize;
if (slot == 0) {
folioq = folioq->prev;
slot = folioq_nr_slots(folioq);
}
slot--;
fsize = folioq_folio_size(folioq, slot);
if (unroll <= fsize) {
i->iov_offset = fsize - unroll;
break;
}
unroll -= fsize;
}
i->folioq_slot = slot;
i->folioq = folioq;
}
void iov_iter_revert(struct iov_iter *i, size_t unroll)
{
if (!unroll)
return;
if (WARN_ON(unroll > MAX_RW_COUNT))
return;
i->count += unroll;
if (unlikely(iov_iter_is_discard(i)))
return;
if (unroll <= i->iov_offset) {
i->iov_offset -= unroll;
return;
}
unroll -= i->iov_offset;
if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) {
BUG(); /* We should never go beyond the start of the specified
* range since we might then be straying into pages that
* aren't pinned.
*/
} else if (iov_iter_is_bvec(i)) {
const struct bio_vec *bvec = i->bvec;
while (1) {
size_t n = (--bvec)->bv_len;
i->nr_segs++;
if (unroll <= n) {
i->bvec = bvec;
i->iov_offset = n - unroll;
return;
}
unroll -= n;
}
} else if (iov_iter_is_folioq(i)) {
i->iov_offset = 0;
iov_iter_folioq_revert(i, unroll);
} else { /* same logics for iovec and kvec */
const struct iovec *iov = iter_iov(i);
while (1) {
size_t n = (--iov)->iov_len;
i->nr_segs++;
if (unroll <= n) {
i->__iov = iov;
i->iov_offset = n - unroll;
return;
}
unroll -= n;
}
}
}
EXPORT_SYMBOL(iov_iter_revert);
/*
* Return the count of just the current iov_iter segment.
*/
size_t iov_iter_single_seg_count(const struct iov_iter *i)
{
if (i->nr_segs > 1) {
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return min(i->count, iter_iov(i)->iov_len - i->iov_offset);
if (iov_iter_is_bvec(i))
return min(i->count, i->bvec->bv_len - i->iov_offset);
}
if (unlikely(iov_iter_is_folioq(i)))
return !i->count ? 0 :
umin(folioq_folio_size(i->folioq, i->folioq_slot), i->count);
return i->count;
}
EXPORT_SYMBOL(iov_iter_single_seg_count);
void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
const struct kvec *kvec, unsigned long nr_segs,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter){
.iter_type = ITER_KVEC,
.data_source = direction,
.kvec = kvec,
.nr_segs = nr_segs,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_kvec);
void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
const struct bio_vec *bvec, unsigned long nr_segs,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter){
.iter_type = ITER_BVEC,
.data_source = direction,
.bvec = bvec,
.nr_segs = nr_segs,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_bvec);
/**
* iov_iter_folio_queue - Initialise an I/O iterator to use the folios in a folio queue
* @i: The iterator to initialise.
* @direction: The direction of the transfer.
* @folioq: The starting point in the folio queue.
* @first_slot: The first slot in the folio queue to use
* @offset: The offset into the folio in the first slot to start at
* @count: The size of the I/O buffer in bytes.
*
* Set up an I/O iterator to either draw data out of the pages attached to an
* inode or to inject data into those pages. The pages *must* be prevented
* from evaporation, either by taking a ref on them or locking them by the
* caller.
*/
void iov_iter_folio_queue(struct iov_iter *i, unsigned int direction,
const struct folio_queue *folioq, unsigned int first_slot,
unsigned int offset, size_t count)
{
BUG_ON(direction & ~1);
*i = (struct iov_iter) {
.iter_type = ITER_FOLIOQ,
.data_source = direction,
.folioq = folioq,
.folioq_slot = first_slot,
.count = count,
.iov_offset = offset,
};
}
EXPORT_SYMBOL(iov_iter_folio_queue);
/**
* iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
* @i: The iterator to initialise.
* @direction: The direction of the transfer.
* @xarray: The xarray to access.
* @start: The start file position.
* @count: The size of the I/O buffer in bytes.
*
* Set up an I/O iterator to either draw data out of the pages attached to an
* inode or to inject data into those pages. The pages *must* be prevented
* from evaporation, either by taking a ref on them or locking them by the
* caller.
*/
void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
struct xarray *xarray, loff_t start, size_t count)
{
BUG_ON(direction & ~1);
*i = (struct iov_iter) {
.iter_type = ITER_XARRAY,
.data_source = direction,
.xarray = xarray,
.xarray_start = start,
.count = count,
.iov_offset = 0
};
}
EXPORT_SYMBOL(iov_iter_xarray);
/**
* iov_iter_discard - Initialise an I/O iterator that discards data
* @i: The iterator to initialise.
* @direction: The direction of the transfer.
* @count: The size of the I/O buffer in bytes.
*
* Set up an I/O iterator that just discards everything that's written to it.
* It's only available as a READ iterator.
*/
void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
{
BUG_ON(direction != READ);
*i = (struct iov_iter){
.iter_type = ITER_DISCARD,
.data_source = false,
.count = count,
.iov_offset = 0
};
}
EXPORT_SYMBOL(iov_iter_discard);
static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask,
unsigned len_mask)
{
const struct iovec *iov = iter_iov(i);
size_t size = i->count;
size_t skip = i->iov_offset;
do {
size_t len = iov->iov_len - skip;
if (len > size)
len = size;
if (len & len_mask)
return false;
if ((unsigned long)(iov->iov_base + skip) & addr_mask)
return false;
iov++;
size -= len;
skip = 0;
} while (size);
return true;
}
static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
unsigned len_mask)
{
const struct bio_vec *bvec = i->bvec;
unsigned skip = i->iov_offset;
size_t size = i->count;
do {
size_t len = bvec->bv_len;
if (len > size)
len = size;
if (len & len_mask)
return false;
if ((unsigned long)(bvec->bv_offset + skip) & addr_mask)
return false;
bvec++;
size -= len;
skip = 0;
} while (size);
return true;
}
/**
* iov_iter_is_aligned() - Check if the addresses and lengths of each segments
* are aligned to the parameters.
*
* @i: &struct iov_iter to restore
* @addr_mask: bit mask to check against the iov element's addresses
* @len_mask: bit mask to check against the iov element's lengths
*
* Return: false if any addresses or lengths intersect with the provided masks
*/
bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
unsigned len_mask)
{
if (likely(iter_is_ubuf(i))) {
if (i->count & len_mask)
return false;
if ((unsigned long)(i->ubuf + i->iov_offset) & addr_mask)
return false;
return true;
}
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_iter_aligned_iovec(i, addr_mask, len_mask);
if (iov_iter_is_bvec(i))
return iov_iter_aligned_bvec(i, addr_mask, len_mask);
/* With both xarray and folioq types, we're dealing with whole folios. */
if (iov_iter_is_xarray(i)) {
if (i->count & len_mask)
return false;
if ((i->xarray_start + i->iov_offset) & addr_mask)
return false;
}
if (iov_iter_is_folioq(i)) {
if (i->count & len_mask)
return false;
if (i->iov_offset & addr_mask)
return false;
}
return true;
}
EXPORT_SYMBOL_GPL(iov_iter_is_aligned);
static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
{
const struct iovec *iov = iter_iov(i);
unsigned long res = 0;
size_t size = i->count;
size_t skip = i->iov_offset;
do {
size_t len = iov->iov_len - skip;
if (len) {
res |= (unsigned long)iov->iov_base + skip;
if (len > size)
len = size;
res |= len;
size -= len;
}
iov++;
skip = 0;
} while (size);
return res;
}
static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
{
const struct bio_vec *bvec = i->bvec;
unsigned res = 0;
size_t size = i->count;
unsigned skip = i->iov_offset;
do {
size_t len = bvec->bv_len - skip;
res |= (unsigned long)bvec->bv_offset + skip;
if (len > size)
len = size;
res |= len;
bvec++;
size -= len;
skip = 0;
} while (size);
return res;
}
unsigned long iov_iter_alignment(const struct iov_iter *i)
{
if (likely(iter_is_ubuf(i))) {
size_t size = i->count;
if (size)
return ((unsigned long)i->ubuf + i->iov_offset) | size;
return 0;
}
/* iovec and kvec have identical layouts */
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_iter_alignment_iovec(i);
if (iov_iter_is_bvec(i))
return iov_iter_alignment_bvec(i);
/* With both xarray and folioq types, we're dealing with whole folios. */
if (iov_iter_is_folioq(i))
return i->iov_offset | i->count;
if (iov_iter_is_xarray(i))
return (i->xarray_start + i->iov_offset) | i->count;
return 0;
}
EXPORT_SYMBOL(iov_iter_alignment);
unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
{
unsigned long res = 0;
unsigned long v = 0;
size_t size = i->count;
unsigned k;
if (iter_is_ubuf(i))
return 0;
if (WARN_ON(!iter_is_iovec(i)))
return ~0U;
for (k = 0; k < i->nr_segs; k++) {
const struct iovec *iov = iter_iov(i) + k;
if (iov->iov_len) {
unsigned long base = (unsigned long)iov->iov_base;
if (v) // if not the first one
res |= base | v; // this start | previous end
v = base + iov->iov_len;
if (size <= iov->iov_len)
break;
size -= iov->iov_len;
}
}
return res;
}
EXPORT_SYMBOL(iov_iter_gap_alignment);
static int want_pages_array(struct page ***res, size_t size,
size_t start, unsigned int maxpages)
{
unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE);
if (count > maxpages)
count = maxpages;
WARN_ON(!count); // caller should've prevented that
if (!*res) {
*res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
if (!*res)
return 0;
}
return count;
}
static ssize_t iter_folioq_get_pages(struct iov_iter *iter,
struct page ***ppages, size_t maxsize,
unsigned maxpages, size_t *_start_offset)
{
const struct folio_queue *folioq = iter->folioq;
struct page **pages;
unsigned int slot = iter->folioq_slot;
size_t extracted = 0, count = iter->count, iov_offset = iter->iov_offset;
if (slot >= folioq_nr_slots(folioq)) {
folioq = folioq->next;
slot = 0;
if (WARN_ON(iov_offset != 0))
return -EIO;
}
maxpages = want_pages_array(ppages, maxsize, iov_offset & ~PAGE_MASK, maxpages);
if (!maxpages)
return -ENOMEM;
*_start_offset = iov_offset & ~PAGE_MASK;
pages = *ppages;
for (;;) {
struct folio *folio = folioq_folio(folioq, slot);
size_t offset = iov_offset, fsize = folioq_folio_size(folioq, slot);
size_t part = PAGE_SIZE - offset % PAGE_SIZE;
part = umin(part, umin(maxsize - extracted, fsize - offset));
count -= part;
iov_offset += part;
extracted += part;
*pages = folio_page(folio, offset / PAGE_SIZE);
get_page(*pages);
pages++;
maxpages--;
if (maxpages == 0 || extracted >= maxsize)
break;
if (iov_offset >= fsize) {
iov_offset = 0;
slot++;
if (slot == folioq_nr_slots(folioq) && folioq->next) {
folioq = folioq->next;
slot = 0;
}
}
}
iter->count = count;
iter->iov_offset = iov_offset;
iter->folioq = folioq;
iter->folioq_slot = slot;
return extracted;
}
static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
pgoff_t index, unsigned int nr_pages)
{
XA_STATE(xas, xa, index);
struct page *page;
unsigned int ret = 0;
rcu_read_lock();
for (page = xas_load(&xas); page; page = xas_next(&xas)) {
if (xas_retry(&xas, page))
continue;
/* Has the page moved or been split? */
if (unlikely(page != xas_reload(&xas))) {
xas_reset(&xas);
continue;
}
pages[ret] = find_subpage(page, xas.xa_index);
get_page(pages[ret]);
if (++ret == nr_pages)
break;
}
rcu_read_unlock();
return ret;
}
static ssize_t iter_xarray_get_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned maxpages, size_t *_start_offset)
{
unsigned nr, offset, count;
pgoff_t index;
loff_t pos;
pos = i->xarray_start + i->iov_offset;
index = pos >> PAGE_SHIFT;
offset = pos & ~PAGE_MASK;
*_start_offset = offset;
count = want_pages_array(pages, maxsize, offset, maxpages);
if (!count)
return -ENOMEM;
nr = iter_xarray_populate_pages(*pages, i->xarray, index, count);
if (nr == 0)
return 0;
maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
i->iov_offset += maxsize;
i->count -= maxsize;
return maxsize;
}
/* must be done on non-empty ITER_UBUF or ITER_IOVEC one */
static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size)
{
size_t skip;
long k;
if (iter_is_ubuf(i))
return (unsigned long)i->ubuf + i->iov_offset;
for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
const struct iovec *iov = iter_iov(i) + k;
size_t len = iov->iov_len - skip;
if (unlikely(!len))
continue;
if (*size > len)
*size = len;
return (unsigned long)iov->iov_base + skip;
}
BUG(); // if it had been empty, we wouldn't get called
}
/* must be done on non-empty ITER_BVEC one */
static struct page *first_bvec_segment(const struct iov_iter *i,
size_t *size, size_t *start)
{
struct page *page;
size_t skip = i->iov_offset, len;
len = i->bvec->bv_len - skip;
if (*size > len)
*size = len;
skip += i->bvec->bv_offset;
page = i->bvec->bv_page + skip / PAGE_SIZE;
*start = skip % PAGE_SIZE;
return page;
}
static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages, size_t *start)
{
unsigned int n, gup_flags = 0;
if (maxsize > i->count)
maxsize = i->count;
if (!maxsize)
return 0;
if (maxsize > MAX_RW_COUNT)
maxsize = MAX_RW_COUNT;
if (likely(user_backed_iter(i))) {
unsigned long addr;
int res;
if (iov_iter_rw(i) != WRITE)
gup_flags |= FOLL_WRITE;
if (i->nofault)
gup_flags |= FOLL_NOFAULT;
addr = first_iovec_segment(i, &maxsize);
*start = addr % PAGE_SIZE;
addr &= PAGE_MASK;
n = want_pages_array(pages, maxsize, *start, maxpages);
if (!n)
return -ENOMEM;
res = get_user_pages_fast(addr, n, gup_flags, *pages);
if (unlikely(res <= 0))
return res;
maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start);
iov_iter_advance(i, maxsize);
return maxsize;
}
if (iov_iter_is_bvec(i)) {
struct page **p;
struct page *page;
page = first_bvec_segment(i, &maxsize, start);
n = want_pages_array(pages, maxsize, *start, maxpages);
if (!n)
return -ENOMEM;
p = *pages;
for (int k = 0; k < n; k++)
get_page(p[k] = page + k);
maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start);
i->count -= maxsize;
i->iov_offset += maxsize;
if (i->iov_offset == i->bvec->bv_len) {
i->iov_offset = 0;
i->bvec++;
i->nr_segs--;
}
return maxsize;
}
if (iov_iter_is_folioq(i))
return iter_folioq_get_pages(i, pages, maxsize, maxpages, start);
if (iov_iter_is_xarray(i))
return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
return -EFAULT;
}
ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
size_t maxsize, unsigned maxpages, size_t *start)
{
if (!maxpages)
return 0;
BUG_ON(!pages);
return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
}
EXPORT_SYMBOL(iov_iter_get_pages2);
ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
struct page ***pages, size_t maxsize, size_t *start)
{
ssize_t len;
*pages = NULL;
len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
if (len <= 0) {
kvfree(*pages);
*pages = NULL;
}
return len;
}
EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
static int iov_npages(const struct iov_iter *i, int maxpages)
{
size_t skip = i->iov_offset, size = i->count;
const struct iovec *p;
int npages = 0;
for (p = iter_iov(i); size; skip = 0, p++) {
unsigned offs = offset_in_page(p->iov_base + skip);
size_t len = min(p->iov_len - skip, size);
if (len) {
size -= len;
npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
if (unlikely(npages > maxpages))
return maxpages;
}
}
return npages;
}
static int bvec_npages(const struct iov_iter *i, int maxpages)
{
size_t skip = i->iov_offset, size = i->count;
const struct bio_vec *p;
int npages = 0;
for (p = i->bvec; size; skip = 0, p++) {
unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
size_t len = min(p->bv_len - skip, size);
size -= len;
npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
if (unlikely(npages > maxpages))
return maxpages;
}
return npages;
}
int iov_iter_npages(const struct iov_iter *i, int maxpages)
{
if (unlikely(!i->count))
return 0;
if (likely(iter_is_ubuf(i))) {
unsigned offs = offset_in_page(i->ubuf + i->iov_offset);
int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE);
return min(npages, maxpages);
}
/* iovec and kvec have identical layouts */
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_npages(i, maxpages);
if (iov_iter_is_bvec(i))
return bvec_npages(i, maxpages);
if (iov_iter_is_folioq(i)) {
unsigned offset = i->iov_offset % PAGE_SIZE;
int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
return min(npages, maxpages);
}
if (iov_iter_is_xarray(i)) {
unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
return min(npages, maxpages);
}
return 0;
}
EXPORT_SYMBOL(iov_iter_npages);
const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
{
*new = *old;
if (iov_iter_is_bvec(new))
return new->bvec = kmemdup(new->bvec,
new->nr_segs * sizeof(struct bio_vec),
flags);
else if (iov_iter_is_kvec(new) || iter_is_iovec(new))
/* iovec and kvec have identical layout */
return new->__iov = kmemdup(new->__iov,
new->nr_segs * sizeof(struct iovec),
flags);
return NULL;
}
EXPORT_SYMBOL(dup_iter);
static __noclone int copy_compat_iovec_from_user(struct iovec *iov,
const struct iovec __user *uvec, u32 nr_segs)
{
const struct compat_iovec __user *uiov =
(const struct compat_iovec __user *)uvec;
int ret = -EFAULT;
u32 i;
if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
return -EFAULT;
for (i = 0; i < nr_segs; i++) {
compat_uptr_t buf;
compat_ssize_t len;
unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
/* check for compat_size_t not fitting in compat_ssize_t .. */
if (len < 0) {
ret = -EINVAL;
goto uaccess_end;
}
iov[i].iov_base = compat_ptr(buf);
iov[i].iov_len = len;
}
ret = 0;
uaccess_end:
user_access_end();
return ret;
}
static __noclone int copy_iovec_from_user(struct iovec *iov,
const struct iovec __user *uiov, unsigned long nr_segs)
{
int ret = -EFAULT;
if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
return -EFAULT;
do {
void __user *buf;
ssize_t len;
unsafe_get_user(len, &uiov->iov_len, uaccess_end);
unsafe_get_user(buf, &uiov->iov_base, uaccess_end);
/* check for size_t not fitting in ssize_t .. */
if (unlikely(len < 0)) {
ret = -EINVAL;
goto uaccess_end;
}
iov->iov_base = buf;
iov->iov_len = len;
uiov++; iov++;
} while (--nr_segs);
ret = 0;
uaccess_end:
user_access_end();
return ret;
}
struct iovec *iovec_from_user(const struct iovec __user *uvec,
unsigned long nr_segs, unsigned long fast_segs,
struct iovec *fast_iov, bool compat)
{
struct iovec *iov = fast_iov;
int ret;
/*
* SuS says "The readv() function *may* fail if the iovcnt argument was
* less than or equal to 0, or greater than {IOV_MAX}. Linux has
* traditionally returned zero for zero segments, so...
*/
if (nr_segs == 0)
return iov;
if (nr_segs > UIO_MAXIOV)
return ERR_PTR(-EINVAL);
if (nr_segs > fast_segs) {
iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
if (!iov)
return ERR_PTR(-ENOMEM);
}
if (unlikely(compat))
ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
else
ret = copy_iovec_from_user(iov, uvec, nr_segs);
if (ret) {
if (iov != fast_iov)
kfree(iov);
return ERR_PTR(ret);
}
return iov;
}
/*
* Single segment iovec supplied by the user, import it as ITER_UBUF.
*/
static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec,
struct iovec **iovp, struct iov_iter *i,
bool compat)
{
struct iovec *iov = *iovp;
ssize_t ret;
if (compat)
ret = copy_compat_iovec_from_user(iov, uvec, 1);
else
ret = copy_iovec_from_user(iov, uvec, 1);
if (unlikely(ret))
return ret;
ret = import_ubuf(type, iov->iov_base, iov->iov_len, i);
if (unlikely(ret))
return ret;
*iovp = NULL;
return i->count;
}
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)
{
ssize_t total_len = 0;
unsigned long seg;
struct iovec *iov;
if (nr_segs == 1)
return __import_iovec_ubuf(type, uvec, iovp, i, compat);
iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
if (IS_ERR(iov)) {
*iovp = NULL;
return PTR_ERR(iov);
}
/*
* According to the Single Unix Specification we should return EINVAL if
* an element length is < 0 when cast to ssize_t or if the total length
* would overflow the ssize_t return value of the system call.
*
* Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
* overflow case.
*/
for (seg = 0; seg < nr_segs; seg++) {
ssize_t len = (ssize_t)iov[seg].iov_len;
if (!access_ok(iov[seg].iov_base, len)) {
if (iov != *iovp)
kfree(iov);
*iovp = NULL;
return -EFAULT;
}
if (len > MAX_RW_COUNT - total_len) {
len = MAX_RW_COUNT - total_len;
iov[seg].iov_len = len;
}
total_len += len;
}
iov_iter_init(i, type, iov, nr_segs, total_len);
if (iov == *iovp)
*iovp = NULL;
else
*iovp = iov;
return total_len;
}
/**
* import_iovec() - Copy an array of &struct iovec from userspace
* into the kernel, check that it is valid, and initialize a new
* &struct iov_iter iterator to access it.
*
* @type: One of %READ or %WRITE.
* @uvec: Pointer to the userspace array.
* @nr_segs: Number of elements in userspace array.
* @fast_segs: Number of elements in @iov.
* @iovp: (input and output parameter) Pointer to pointer to (usually small
* on-stack) kernel array.
* @i: Pointer to iterator that will be initialized on success.
*
* If the array pointed to by *@iov is large enough to hold all @nr_segs,
* then this function places %NULL in *@iov on return. Otherwise, a new
* array will be allocated and the result placed in *@iov. This means that
* the caller may call kfree() on *@iov regardless of whether the small
* on-stack array was used or not (and regardless of whether this function
* returns an error or not).
*
* Return: Negative error code on error, bytes imported on success
*/
ssize_t import_iovec(int type, const struct iovec __user *uvec,
unsigned nr_segs, unsigned fast_segs,
struct iovec **iovp, struct iov_iter *i)
{
return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
in_compat_syscall());
}
EXPORT_SYMBOL(import_iovec);
int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i)
{
if (len > MAX_RW_COUNT)
len = MAX_RW_COUNT;
if (unlikely(!access_ok(buf, len)))
return -EFAULT;
iov_iter_ubuf(i, rw, buf, len);
return 0;
}
EXPORT_SYMBOL_GPL(import_ubuf);
/**
* iov_iter_restore() - Restore a &struct iov_iter to the same state as when
* iov_iter_save_state() was called.
*
* @i: &struct iov_iter to restore
* @state: state to restore from
*
* Used after iov_iter_save_state() to bring restore @i, if operations may
* have advanced it.
*
* Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
*/
void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
{
if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i) &&
!iter_is_ubuf(i)) && !iov_iter_is_kvec(i))
return;
i->iov_offset = state->iov_offset;
i->count = state->count;
if (iter_is_ubuf(i))
return;
/*
* For the *vec iters, nr_segs + iov is constant - if we increment
* the vec, then we also decrement the nr_segs count. Hence we don't
* need to track both of these, just one is enough and we can deduct
* the other from that. ITER_KVEC and ITER_IOVEC are the same struct
* size, so we can just increment the iov pointer as they are unionzed.
* ITER_BVEC _may_ be the same size on some archs, but on others it is
* not. Be safe and handle it separately.
*/
BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
if (iov_iter_is_bvec(i))
i->bvec -= state->nr_segs - i->nr_segs;
else
i->__iov -= state->nr_segs - i->nr_segs;
i->nr_segs = state->nr_segs;
}
/*
* Extract a list of contiguous pages from an ITER_FOLIOQ iterator. This does
* not get references on the pages, nor does it get a pin on them.
*/
static ssize_t iov_iter_extract_folioq_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
const struct folio_queue *folioq = i->folioq;
struct page **p;
unsigned int nr = 0;
size_t extracted = 0, offset, slot = i->folioq_slot;
if (slot >= folioq_nr_slots(folioq)) {
folioq = folioq->next;
slot = 0;
if (WARN_ON(i->iov_offset != 0))
return -EIO;
}
offset = i->iov_offset & ~PAGE_MASK;
*offset0 = offset;
maxpages = want_pages_array(pages, maxsize, offset, maxpages);
if (!maxpages)
return -ENOMEM;
p = *pages;
for (;;) {
struct folio *folio = folioq_folio(folioq, slot);
size_t offset = i->iov_offset, fsize = folioq_folio_size(folioq, slot);
size_t part = PAGE_SIZE - offset % PAGE_SIZE;
if (offset < fsize) {
part = umin(part, umin(maxsize - extracted, fsize - offset));
i->count -= part;
i->iov_offset += part;
extracted += part;
p[nr++] = folio_page(folio, offset / PAGE_SIZE);
}
if (nr >= maxpages || extracted >= maxsize)
break;
if (i->iov_offset >= fsize) {
i->iov_offset = 0;
slot++;
if (slot == folioq_nr_slots(folioq) && folioq->next) {
folioq = folioq->next;
slot = 0;
}
}
}
i->folioq = folioq;
i->folioq_slot = slot;
return extracted;
}
/*
* Extract a list of contiguous pages from an ITER_XARRAY iterator. This does not
* get references on the pages, nor does it get a pin on them.
*/
static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
struct page *page, **p;
unsigned int nr = 0, offset;
loff_t pos = i->xarray_start + i->iov_offset;
pgoff_t index = pos >> PAGE_SHIFT;
XA_STATE(xas, i->xarray, index);
offset = pos & ~PAGE_MASK;
*offset0 = offset;
maxpages = want_pages_array(pages, maxsize, offset, maxpages);
if (!maxpages)
return -ENOMEM;
p = *pages;
rcu_read_lock();
for (page = xas_load(&xas); page; page = xas_next(&xas)) {
if (xas_retry(&xas, page))
continue;
/* Has the page moved or been split? */
if (unlikely(page != xas_reload(&xas))) {
xas_reset(&xas);
continue;
}
p[nr++] = find_subpage(page, xas.xa_index);
if (nr == maxpages)
break;
}
rcu_read_unlock();
maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
iov_iter_advance(i, maxsize);
return maxsize;
}
/*
* Extract a list of contiguous pages from an ITER_BVEC iterator. This does
* not get references on the pages, nor does it get a pin on them.
*/
static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
struct page **p, *page;
size_t skip = i->iov_offset, offset, size;
int k;
for (;;) {
if (i->nr_segs == 0)
return 0;
size = min(maxsize, i->bvec->bv_len - skip);
if (size)
break;
i->iov_offset = 0;
i->nr_segs--;
i->bvec++;
skip = 0;
}
skip += i->bvec->bv_offset;
page = i->bvec->bv_page + skip / PAGE_SIZE;
offset = skip % PAGE_SIZE;
*offset0 = offset;
maxpages = want_pages_array(pages, size, offset, maxpages);
if (!maxpages)
return -ENOMEM;
p = *pages;
for (k = 0; k < maxpages; k++)
p[k] = page + k;
size = min_t(size_t, size, maxpages * PAGE_SIZE - offset);
iov_iter_advance(i, size);
return size;
}
/*
* Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
* This does not get references on the pages, nor does it get a pin on them.
*/
static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
struct page **p, *page;
const void *kaddr;
size_t skip = i->iov_offset, offset, len, size;
int k;
for (;;) {
if (i->nr_segs == 0)
return 0;
size = min(maxsize, i->kvec->iov_len - skip);
if (size)
break;
i->iov_offset = 0;
i->nr_segs--;
i->kvec++;
skip = 0;
}
kaddr = i->kvec->iov_base + skip;
offset = (unsigned long)kaddr & ~PAGE_MASK;
*offset0 = offset;
maxpages = want_pages_array(pages, size, offset, maxpages);
if (!maxpages)
return -ENOMEM;
p = *pages;
kaddr -= offset;
len = offset + size;
for (k = 0; k < maxpages; k++) {
size_t seg = min_t(size_t, len, PAGE_SIZE);
if (is_vmalloc_or_module_addr(kaddr))
page = vmalloc_to_page(kaddr);
else
page = virt_to_page(kaddr);
p[k] = page;
len -= seg;
kaddr += PAGE_SIZE;
}
size = min_t(size_t, size, maxpages * PAGE_SIZE - offset);
iov_iter_advance(i, size);
return size;
}
/*
* Extract a list of contiguous pages from a user iterator and get a pin on
* each of them. This should only be used if the iterator is user-backed
* (IOBUF/UBUF).
*
* It does not get refs on the pages, but the pages must be unpinned by the
* caller once the transfer is complete.
*
* This is safe to be used where background IO/DMA *is* going to be modifying
* the buffer; using a pin rather than a ref makes forces fork() to give the
* child a copy of the page.
*/
static ssize_t iov_iter_extract_user_pages(struct iov_iter *i,
struct page ***pages,
size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
unsigned long addr;
unsigned int gup_flags = 0;
size_t offset;
int res;
if (i->data_source == ITER_DEST)
gup_flags |= FOLL_WRITE;
if (extraction_flags & ITER_ALLOW_P2PDMA)
gup_flags |= FOLL_PCI_P2PDMA;
if (i->nofault)
gup_flags |= FOLL_NOFAULT;
addr = first_iovec_segment(i, &maxsize);
*offset0 = offset = addr % PAGE_SIZE;
addr &= PAGE_MASK;
maxpages = want_pages_array(pages, maxsize, offset, maxpages);
if (!maxpages)
return -ENOMEM;
res = pin_user_pages_fast(addr, maxpages, gup_flags, *pages);
if (unlikely(res <= 0))
return res;
maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset);
iov_iter_advance(i, maxsize);
return maxsize;
}
/**
* iov_iter_extract_pages - Extract a list of contiguous pages from an iterator
* @i: The iterator to extract from
* @pages: Where to return the list of pages
* @maxsize: The maximum amount of iterator to extract
* @maxpages: The maximum size of the list of pages
* @extraction_flags: Flags to qualify request
* @offset0: Where to return the starting offset into (*@pages)[0]
*
* Extract a list of contiguous pages from the current point of the iterator,
* advancing the iterator. The maximum number of pages and the maximum amount
* of page contents can be set.
*
* If *@pages is NULL, a page list will be allocated to the required size and
* *@pages will be set to its base. If *@pages is not NULL, it will be assumed
* that the caller allocated a page list at least @maxpages in size and this
* will be filled in.
*
* @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
* be allowed on the pages extracted.
*
* The iov_iter_extract_will_pin() function can be used to query how cleanup
* should be performed.
*
* Extra refs or pins on the pages may be obtained as follows:
*
* (*) If the iterator is user-backed (ITER_IOVEC/ITER_UBUF), pins will be
* added to the pages, but refs will not be taken.
* iov_iter_extract_will_pin() will return true.
*
* (*) If the iterator is ITER_KVEC, ITER_BVEC, ITER_FOLIOQ or ITER_XARRAY, the
* pages are merely listed; no extra refs or pins are obtained.
* iov_iter_extract_will_pin() will return 0.
*
* Note also:
*
* (*) Use with ITER_DISCARD is not supported as that has no content.
*
* On success, the function sets *@pages to the new pagelist, if allocated, and
* sets *offset0 to the offset into the first page.
*
* It may also return -ENOMEM and -EFAULT.
*/
ssize_t iov_iter_extract_pages(struct iov_iter *i,
struct page ***pages,
size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT);
if (!maxsize)
return 0;
if (likely(user_backed_iter(i)))
return iov_iter_extract_user_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
if (iov_iter_is_kvec(i))
return iov_iter_extract_kvec_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
if (iov_iter_is_bvec(i))
return iov_iter_extract_bvec_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
if (iov_iter_is_folioq(i))
return iov_iter_extract_folioq_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
if (iov_iter_is_xarray(i))
return iov_iter_extract_xarray_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
return -EFAULT;
}
EXPORT_SYMBOL_GPL(iov_iter_extract_pages);
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