linux-stable/lib/iov_iter.c
Jens Axboe 8fb0f47a9d iov_iter: add helper to save iov_iter state
In an ideal world, when someone is passed an iov_iter and returns X bytes,
then X bytes would have been consumed/advanced from the iov_iter. But we
have use cases that always consume the entire iterator, a few examples
of that are iomap and bdev O_DIRECT. This means we cannot rely on the
state of the iov_iter once we've called ->read_iter() or ->write_iter().

This would be easier if we didn't always have to deal with truncate of
the iov_iter, as rewinding would be trivial without that. We recently
added a commit to track the truncate state, but that grew the iov_iter
by 8 bytes and wasn't the best solution.

Implement a helper to save enough of the iov_iter state to sanely restore
it after we've called the read/write iterator helpers. This currently
only works for IOVEC/BVEC/KVEC as that's all we need, support for other
iterator types are left as an exercise for the reader.

Link: https://lore.kernel.org/linux-fsdevel/CAHk-=wiacKV4Gh-MYjteU0LwNBSGpWrK-Ov25HdqB1ewinrFPg@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-09-14 08:12:18 -06:00

2010 lines
48 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <crypto/hash.h>
#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 <net/checksum.h>
#include <linux/scatterlist.h>
#include <linux/instrumented.h>
#define PIPE_PARANOIA /* for now */
/* covers iovec and kvec alike */
#define iterate_iovec(i, n, base, len, off, __p, STEP) { \
size_t off = 0; \
size_t skip = i->iov_offset; \
do { \
len = min(n, __p->iov_len - skip); \
if (likely(len)) { \
base = __p->iov_base + skip; \
len -= (STEP); \
off += len; \
skip += len; \
n -= len; \
if (skip < __p->iov_len) \
break; \
} \
__p++; \
skip = 0; \
} while (n); \
i->iov_offset = skip; \
n = off; \
}
#define iterate_bvec(i, n, base, len, off, p, STEP) { \
size_t off = 0; \
unsigned skip = i->iov_offset; \
while (n) { \
unsigned offset = p->bv_offset + skip; \
unsigned left; \
void *kaddr = kmap_local_page(p->bv_page + \
offset / PAGE_SIZE); \
base = kaddr + offset % PAGE_SIZE; \
len = min(min(n, (size_t)(p->bv_len - skip)), \
(size_t)(PAGE_SIZE - offset % PAGE_SIZE)); \
left = (STEP); \
kunmap_local(kaddr); \
len -= left; \
off += len; \
skip += len; \
if (skip == p->bv_len) { \
skip = 0; \
p++; \
} \
n -= len; \
if (left) \
break; \
} \
i->iov_offset = skip; \
n = off; \
}
#define iterate_xarray(i, n, base, len, __off, STEP) { \
__label__ __out; \
size_t __off = 0; \
struct page *head = NULL; \
loff_t start = i->xarray_start + i->iov_offset; \
unsigned offset = start % PAGE_SIZE; \
pgoff_t index = start / PAGE_SIZE; \
int j; \
\
XA_STATE(xas, i->xarray, index); \
\
rcu_read_lock(); \
xas_for_each(&xas, head, ULONG_MAX) { \
unsigned left; \
if (xas_retry(&xas, head)) \
continue; \
if (WARN_ON(xa_is_value(head))) \
break; \
if (WARN_ON(PageHuge(head))) \
break; \
for (j = (head->index < index) ? index - head->index : 0; \
j < thp_nr_pages(head); j++) { \
void *kaddr = kmap_local_page(head + j); \
base = kaddr + offset; \
len = PAGE_SIZE - offset; \
len = min(n, len); \
left = (STEP); \
kunmap_local(kaddr); \
len -= left; \
__off += len; \
n -= len; \
if (left || n == 0) \
goto __out; \
offset = 0; \
} \
} \
__out: \
rcu_read_unlock(); \
i->iov_offset += __off; \
n = __off; \
}
#define __iterate_and_advance(i, n, base, len, off, I, K) { \
if (unlikely(i->count < n)) \
n = i->count; \
if (likely(n)) { \
if (likely(iter_is_iovec(i))) { \
const struct iovec *iov = i->iov; \
void __user *base; \
size_t len; \
iterate_iovec(i, n, base, len, off, \
iov, (I)) \
i->nr_segs -= iov - i->iov; \
i->iov = iov; \
} else if (iov_iter_is_bvec(i)) { \
const struct bio_vec *bvec = i->bvec; \
void *base; \
size_t len; \
iterate_bvec(i, n, base, len, off, \
bvec, (K)) \
i->nr_segs -= bvec - i->bvec; \
i->bvec = bvec; \
} else if (iov_iter_is_kvec(i)) { \
const struct kvec *kvec = i->kvec; \
void *base; \
size_t len; \
iterate_iovec(i, n, base, len, off, \
kvec, (K)) \
i->nr_segs -= kvec - i->kvec; \
i->kvec = kvec; \
} else if (iov_iter_is_xarray(i)) { \
void *base; \
size_t len; \
iterate_xarray(i, n, base, len, off, \
(K)) \
} \
i->count -= n; \
} \
}
#define iterate_and_advance(i, n, base, len, off, I, K) \
__iterate_and_advance(i, n, base, len, off, I, ((void)(K),0))
static int copyout(void __user *to, const void *from, size_t n)
{
if (should_fail_usercopy())
return n;
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
n = raw_copy_to_user(to, from, n);
}
return n;
}
static int copyin(void *to, const void __user *from, size_t n)
{
if (should_fail_usercopy())
return n;
if (access_ok(from, n)) {
instrument_copy_from_user(to, from, n);
n = raw_copy_from_user(to, from, n);
}
return n;
}
static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, left, wanted;
const struct iovec *iov;
char __user *buf;
void *kaddr, *from;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
might_fault();
wanted = bytes;
iov = i->iov;
skip = i->iov_offset;
buf = iov->iov_base + skip;
copy = min(bytes, iov->iov_len - skip);
if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
kaddr = kmap_atomic(page);
from = kaddr + offset;
/* first chunk, usually the only one */
left = copyout(buf, from, copy);
copy -= left;
skip += copy;
from += copy;
bytes -= copy;
while (unlikely(!left && bytes)) {
iov++;
buf = iov->iov_base;
copy = min(bytes, iov->iov_len);
left = copyout(buf, from, copy);
copy -= left;
skip = copy;
from += copy;
bytes -= copy;
}
if (likely(!bytes)) {
kunmap_atomic(kaddr);
goto done;
}
offset = from - kaddr;
buf += copy;
kunmap_atomic(kaddr);
copy = min(bytes, iov->iov_len - skip);
}
/* Too bad - revert to non-atomic kmap */
kaddr = kmap(page);
from = kaddr + offset;
left = copyout(buf, from, copy);
copy -= left;
skip += copy;
from += copy;
bytes -= copy;
while (unlikely(!left && bytes)) {
iov++;
buf = iov->iov_base;
copy = min(bytes, iov->iov_len);
left = copyout(buf, from, copy);
copy -= left;
skip = copy;
from += copy;
bytes -= copy;
}
kunmap(page);
done:
if (skip == iov->iov_len) {
iov++;
skip = 0;
}
i->count -= wanted - bytes;
i->nr_segs -= iov - i->iov;
i->iov = iov;
i->iov_offset = skip;
return wanted - bytes;
}
static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, left, wanted;
const struct iovec *iov;
char __user *buf;
void *kaddr, *to;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
might_fault();
wanted = bytes;
iov = i->iov;
skip = i->iov_offset;
buf = iov->iov_base + skip;
copy = min(bytes, iov->iov_len - skip);
if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
kaddr = kmap_atomic(page);
to = kaddr + offset;
/* first chunk, usually the only one */
left = copyin(to, buf, copy);
copy -= left;
skip += copy;
to += copy;
bytes -= copy;
while (unlikely(!left && bytes)) {
iov++;
buf = iov->iov_base;
copy = min(bytes, iov->iov_len);
left = copyin(to, buf, copy);
copy -= left;
skip = copy;
to += copy;
bytes -= copy;
}
if (likely(!bytes)) {
kunmap_atomic(kaddr);
goto done;
}
offset = to - kaddr;
buf += copy;
kunmap_atomic(kaddr);
copy = min(bytes, iov->iov_len - skip);
}
/* Too bad - revert to non-atomic kmap */
kaddr = kmap(page);
to = kaddr + offset;
left = copyin(to, buf, copy);
copy -= left;
skip += copy;
to += copy;
bytes -= copy;
while (unlikely(!left && bytes)) {
iov++;
buf = iov->iov_base;
copy = min(bytes, iov->iov_len);
left = copyin(to, buf, copy);
copy -= left;
skip = copy;
to += copy;
bytes -= copy;
}
kunmap(page);
done:
if (skip == iov->iov_len) {
iov++;
skip = 0;
}
i->count -= wanted - bytes;
i->nr_segs -= iov - i->iov;
i->iov = iov;
i->iov_offset = skip;
return wanted - bytes;
}
#ifdef PIPE_PARANOIA
static bool sanity(const struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_head = pipe->head;
unsigned int p_tail = pipe->tail;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
unsigned int i_head = i->head;
unsigned int idx;
if (i->iov_offset) {
struct pipe_buffer *p;
if (unlikely(p_occupancy == 0))
goto Bad; // pipe must be non-empty
if (unlikely(i_head != p_head - 1))
goto Bad; // must be at the last buffer...
p = &pipe->bufs[i_head & p_mask];
if (unlikely(p->offset + p->len != i->iov_offset))
goto Bad; // ... at the end of segment
} else {
if (i_head != p_head)
goto Bad; // must be right after the last buffer
}
return true;
Bad:
printk(KERN_ERR "idx = %d, offset = %zd\n", i_head, i->iov_offset);
printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
p_head, p_tail, pipe->ring_size);
for (idx = 0; idx < pipe->ring_size; idx++)
printk(KERN_ERR "[%p %p %d %d]\n",
pipe->bufs[idx].ops,
pipe->bufs[idx].page,
pipe->bufs[idx].offset,
pipe->bufs[idx].len);
WARN_ON(1);
return false;
}
#else
#define sanity(i) true
#endif
static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
struct pipe_buffer *buf;
unsigned int p_tail = pipe->tail;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int i_head = i->head;
size_t off;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
if (!sanity(i))
return 0;
off = i->iov_offset;
buf = &pipe->bufs[i_head & p_mask];
if (off) {
if (offset == off && buf->page == page) {
/* merge with the last one */
buf->len += bytes;
i->iov_offset += bytes;
goto out;
}
i_head++;
buf = &pipe->bufs[i_head & p_mask];
}
if (pipe_full(i_head, p_tail, pipe->max_usage))
return 0;
buf->ops = &page_cache_pipe_buf_ops;
get_page(page);
buf->page = page;
buf->offset = offset;
buf->len = bytes;
pipe->head = i_head + 1;
i->iov_offset = offset + bytes;
i->head = i_head;
out:
i->count -= bytes;
return bytes;
}
/*
* Fault in one or more iovecs of the given iov_iter, to a maximum length of
* bytes. For each iovec, fault in each page that constitutes the iovec.
*
* Return 0 on success, or non-zero if the memory could not be accessed (i.e.
* because it is an invalid address).
*/
int iov_iter_fault_in_readable(const struct iov_iter *i, size_t bytes)
{
if (iter_is_iovec(i)) {
const struct iovec *p;
size_t skip;
if (bytes > i->count)
bytes = i->count;
for (p = i->iov, skip = i->iov_offset; bytes; p++, skip = 0) {
size_t len = min(bytes, p->iov_len - skip);
int err;
if (unlikely(!len))
continue;
err = fault_in_pages_readable(p->iov_base + skip, len);
if (unlikely(err))
return err;
bytes -= len;
}
}
return 0;
}
EXPORT_SYMBOL(iov_iter_fault_in_readable);
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,
.data_source = direction,
.iov = iov,
.nr_segs = nr_segs,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_init);
static inline bool allocated(struct pipe_buffer *buf)
{
return buf->ops == &default_pipe_buf_ops;
}
static inline void data_start(const struct iov_iter *i,
unsigned int *iter_headp, size_t *offp)
{
unsigned int p_mask = i->pipe->ring_size - 1;
unsigned int iter_head = i->head;
size_t off = i->iov_offset;
if (off && (!allocated(&i->pipe->bufs[iter_head & p_mask]) ||
off == PAGE_SIZE)) {
iter_head++;
off = 0;
}
*iter_headp = iter_head;
*offp = off;
}
static size_t push_pipe(struct iov_iter *i, size_t size,
int *iter_headp, size_t *offp)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_tail = pipe->tail;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int iter_head;
size_t off;
ssize_t left;
if (unlikely(size > i->count))
size = i->count;
if (unlikely(!size))
return 0;
left = size;
data_start(i, &iter_head, &off);
*iter_headp = iter_head;
*offp = off;
if (off) {
left -= PAGE_SIZE - off;
if (left <= 0) {
pipe->bufs[iter_head & p_mask].len += size;
return size;
}
pipe->bufs[iter_head & p_mask].len = PAGE_SIZE;
iter_head++;
}
while (!pipe_full(iter_head, p_tail, pipe->max_usage)) {
struct pipe_buffer *buf = &pipe->bufs[iter_head & p_mask];
struct page *page = alloc_page(GFP_USER);
if (!page)
break;
buf->ops = &default_pipe_buf_ops;
buf->page = page;
buf->offset = 0;
buf->len = min_t(ssize_t, left, PAGE_SIZE);
left -= buf->len;
iter_head++;
pipe->head = iter_head;
if (left == 0)
return size;
}
return size - left;
}
static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int i_head;
size_t n, off;
if (!sanity(i))
return 0;
bytes = n = push_pipe(i, bytes, &i_head, &off);
if (unlikely(!n))
return 0;
do {
size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
memcpy_to_page(pipe->bufs[i_head & p_mask].page, off, addr, chunk);
i->head = i_head;
i->iov_offset = off + chunk;
n -= chunk;
addr += chunk;
off = 0;
i_head++;
} while (n);
i->count -= bytes;
return bytes;
}
static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
__wsum sum, size_t off)
{
__wsum next = csum_partial_copy_nocheck(from, to, len);
return csum_block_add(sum, next, off);
}
static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
struct iov_iter *i, __wsum *sump)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_mask = pipe->ring_size - 1;
__wsum sum = *sump;
size_t off = 0;
unsigned int i_head;
size_t r;
if (!sanity(i))
return 0;
bytes = push_pipe(i, bytes, &i_head, &r);
while (bytes) {
size_t chunk = min_t(size_t, bytes, PAGE_SIZE - r);
char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off);
kunmap_local(p);
i->head = i_head;
i->iov_offset = r + chunk;
bytes -= chunk;
off += chunk;
r = 0;
i_head++;
}
*sump = sum;
i->count -= off;
return off;
}
size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i)))
return copy_pipe_to_iter(addr, bytes, i);
if (iter_is_iovec(i))
might_fault();
iterate_and_advance(i, bytes, base, len, off,
copyout(base, addr + off, len),
memcpy(base, addr + off, len)
)
return bytes;
}
EXPORT_SYMBOL(_copy_to_iter);
#ifdef CONFIG_ARCH_HAS_COPY_MC
static int copyout_mc(void __user *to, const void *from, size_t n)
{
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
n = copy_mc_to_user((__force void *) to, from, n);
}
return n;
}
static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int i_head;
size_t n, off, xfer = 0;
if (!sanity(i))
return 0;
n = push_pipe(i, bytes, &i_head, &off);
while (n) {
size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
unsigned long rem;
rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
chunk -= rem;
kunmap_local(p);
i->head = i_head;
i->iov_offset = off + chunk;
xfer += chunk;
if (rem)
break;
n -= chunk;
off = 0;
i_head++;
}
i->count -= xfer;
return xfer;
}
/**
* _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, ITER_PIPE, 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 (unlikely(iov_iter_is_pipe(i)))
return copy_mc_pipe_to_iter(addr, bytes, i);
if (iter_is_iovec(i))
might_fault();
__iterate_and_advance(i, bytes, base, len, off,
copyout_mc(base, addr + off, len),
copy_mc_to_kernel(base, addr + off, len)
)
return bytes;
}
EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
#endif /* CONFIG_ARCH_HAS_COPY_MC */
size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i))) {
WARN_ON(1);
return 0;
}
if (iter_is_iovec(i))
might_fault();
iterate_and_advance(i, bytes, base, len, off,
copyin(addr + off, base, len),
memcpy(addr + off, base, len)
)
return bytes;
}
EXPORT_SYMBOL(_copy_from_iter);
size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i))) {
WARN_ON(1);
return 0;
}
iterate_and_advance(i, bytes, base, len, off,
__copy_from_user_inatomic_nocache(addr + off, base, len),
memcpy(addr + off, base, len)
)
return bytes;
}
EXPORT_SYMBOL(_copy_from_iter_nocache);
#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
/**
* _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 (unlikely(iov_iter_is_pipe(i))) {
WARN_ON(1);
return 0;
}
iterate_and_advance(i, bytes, base, len, off,
__copy_from_user_flushcache(addr + off, base, len),
memcpy_flushcache(addr + off, base, len)
)
return bytes;
}
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 (likely(n <= v && v <= (page_size(head))))
return true;
WARN_ON(1);
return false;
}
static size_t __copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
if (likely(iter_is_iovec(i)))
return copy_page_to_iter_iovec(page, offset, bytes, i);
if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
void *kaddr = kmap_local_page(page);
size_t wanted = _copy_to_iter(kaddr + offset, bytes, i);
kunmap_local(kaddr);
return wanted;
}
if (iov_iter_is_pipe(i))
return copy_page_to_iter_pipe(page, offset, bytes, i);
if (unlikely(iov_iter_is_discard(i))) {
if (unlikely(i->count < bytes))
bytes = i->count;
i->count -= bytes;
return bytes;
}
WARN_ON(1);
return 0;
}
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t res = 0;
if (unlikely(!page_copy_sane(page, offset, bytes)))
return 0;
page += offset / PAGE_SIZE; // first subpage
offset %= PAGE_SIZE;
while (1) {
size_t n = __copy_page_to_iter(page, offset,
min(bytes, (size_t)PAGE_SIZE - offset), i);
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_from_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
if (unlikely(!page_copy_sane(page, offset, bytes)))
return 0;
if (likely(iter_is_iovec(i)))
return copy_page_from_iter_iovec(page, offset, bytes, i);
if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
void *kaddr = kmap_local_page(page);
size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
kunmap_local(kaddr);
return wanted;
}
WARN_ON(1);
return 0;
}
EXPORT_SYMBOL(copy_page_from_iter);
static size_t pipe_zero(size_t bytes, struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int i_head;
size_t n, off;
if (!sanity(i))
return 0;
bytes = n = push_pipe(i, bytes, &i_head, &off);
if (unlikely(!n))
return 0;
do {
size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
memset(p + off, 0, chunk);
kunmap_local(p);
i->head = i_head;
i->iov_offset = off + chunk;
n -= chunk;
off = 0;
i_head++;
} while (n);
i->count -= bytes;
return bytes;
}
size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i)))
return pipe_zero(bytes, i);
iterate_and_advance(i, bytes, base, len, count,
clear_user(base, len),
memset(base, 0, len)
)
return bytes;
}
EXPORT_SYMBOL(iov_iter_zero);
size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
struct iov_iter *i)
{
char *kaddr = kmap_atomic(page), *p = kaddr + offset;
if (unlikely(!page_copy_sane(page, offset, bytes))) {
kunmap_atomic(kaddr);
return 0;
}
if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
kunmap_atomic(kaddr);
WARN_ON(1);
return 0;
}
iterate_and_advance(i, bytes, base, len, off,
copyin(p + off, base, len),
memcpy(p + off, base, len)
)
kunmap_atomic(kaddr);
return bytes;
}
EXPORT_SYMBOL(copy_page_from_iter_atomic);
static inline void pipe_truncate(struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_tail = pipe->tail;
unsigned int p_head = pipe->head;
unsigned int p_mask = pipe->ring_size - 1;
if (!pipe_empty(p_head, p_tail)) {
struct pipe_buffer *buf;
unsigned int i_head = i->head;
size_t off = i->iov_offset;
if (off) {
buf = &pipe->bufs[i_head & p_mask];
buf->len = off - buf->offset;
i_head++;
}
while (p_head != i_head) {
p_head--;
pipe_buf_release(pipe, &pipe->bufs[p_head & p_mask]);
}
pipe->head = p_head;
}
}
static void pipe_advance(struct iov_iter *i, size_t size)
{
struct pipe_inode_info *pipe = i->pipe;
if (size) {
struct pipe_buffer *buf;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int i_head = i->head;
size_t off = i->iov_offset, left = size;
if (off) /* make it relative to the beginning of buffer */
left += off - pipe->bufs[i_head & p_mask].offset;
while (1) {
buf = &pipe->bufs[i_head & p_mask];
if (left <= buf->len)
break;
left -= buf->len;
i_head++;
}
i->head = i_head;
i->iov_offset = buf->offset + left;
}
i->count -= size;
/* ... and discard everything past that point */
pipe_truncate(i);
}
static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
{
struct bvec_iter bi;
bi.bi_size = i->count;
bi.bi_bvec_done = i->iov_offset;
bi.bi_idx = 0;
bvec_iter_advance(i->bvec, &bi, size);
i->bvec += bi.bi_idx;
i->nr_segs -= bi.bi_idx;
i->count = bi.bi_size;
i->iov_offset = bi.bi_bvec_done;
}
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 = i->iov, 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 - i->iov;
i->iov = iov;
}
void iov_iter_advance(struct iov_iter *i, size_t size)
{
if (unlikely(i->count < size))
size = i->count;
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_pipe(i)) {
pipe_advance(i, size);
} else if (unlikely(iov_iter_is_xarray(i))) {
i->iov_offset += size;
i->count -= size;
} else if (iov_iter_is_discard(i)) {
i->count -= size;
}
}
EXPORT_SYMBOL(iov_iter_advance);
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_pipe(i))) {
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_mask = pipe->ring_size - 1;
unsigned int i_head = i->head;
size_t off = i->iov_offset;
while (1) {
struct pipe_buffer *b = &pipe->bufs[i_head & p_mask];
size_t n = off - b->offset;
if (unroll < n) {
off -= unroll;
break;
}
unroll -= n;
if (!unroll && i_head == i->start_head) {
off = 0;
break;
}
i_head--;
b = &pipe->bufs[i_head & p_mask];
off = b->offset + b->len;
}
i->iov_offset = off;
i->head = i_head;
pipe_truncate(i);
return;
}
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)) {
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 { /* same logics for iovec and kvec */
const struct iovec *iov = i->iov;
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, i->iov->iov_len - i->iov_offset);
if (iov_iter_is_bvec(i))
return min(i->count, i->bvec->bv_len - i->iov_offset);
}
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);
void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
struct pipe_inode_info *pipe,
size_t count)
{
BUG_ON(direction != READ);
WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
*i = (struct iov_iter){
.iter_type = ITER_PIPE,
.data_source = false,
.pipe = pipe,
.head = pipe->head,
.start_head = pipe->head,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_pipe);
/**
* 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 unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
{
unsigned long res = 0;
size_t size = i->count;
size_t skip = i->iov_offset;
unsigned k;
for (k = 0; k < i->nr_segs; k++, skip = 0) {
size_t len = i->iov[k].iov_len - skip;
if (len) {
res |= (unsigned long)i->iov[k].iov_base + skip;
if (len > size)
len = size;
res |= len;
size -= len;
if (!size)
break;
}
}
return res;
}
static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
{
unsigned res = 0;
size_t size = i->count;
unsigned skip = i->iov_offset;
unsigned k;
for (k = 0; k < i->nr_segs; k++, skip = 0) {
size_t len = i->bvec[k].bv_len - skip;
res |= (unsigned long)i->bvec[k].bv_offset + skip;
if (len > size)
len = size;
res |= len;
size -= len;
if (!size)
break;
}
return res;
}
unsigned long iov_iter_alignment(const struct iov_iter *i)
{
/* 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);
if (iov_iter_is_pipe(i)) {
unsigned int p_mask = i->pipe->ring_size - 1;
size_t size = i->count;
if (size && i->iov_offset && allocated(&i->pipe->bufs[i->head & p_mask]))
return size | i->iov_offset;
return size;
}
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 (WARN_ON(!iter_is_iovec(i)))
return ~0U;
for (k = 0; k < i->nr_segs; k++) {
if (i->iov[k].iov_len) {
unsigned long base = (unsigned long)i->iov[k].iov_base;
if (v) // if not the first one
res |= base | v; // this start | previous end
v = base + i->iov[k].iov_len;
if (size <= i->iov[k].iov_len)
break;
size -= i->iov[k].iov_len;
}
}
return res;
}
EXPORT_SYMBOL(iov_iter_gap_alignment);
static inline ssize_t __pipe_get_pages(struct iov_iter *i,
size_t maxsize,
struct page **pages,
int iter_head,
size_t *start)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_mask = pipe->ring_size - 1;
ssize_t n = push_pipe(i, maxsize, &iter_head, start);
if (!n)
return -EFAULT;
maxsize = n;
n += *start;
while (n > 0) {
get_page(*pages++ = pipe->bufs[iter_head & p_mask].page);
iter_head++;
n -= PAGE_SIZE;
}
return maxsize;
}
static ssize_t pipe_get_pages(struct iov_iter *i,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
{
unsigned int iter_head, npages;
size_t capacity;
if (!sanity(i))
return -EFAULT;
data_start(i, &iter_head, start);
/* Amount of free space: some of this one + all after this one */
npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
capacity = min(npages, maxpages) * PAGE_SIZE - *start;
return __pipe_get_pages(i, min(maxsize, capacity), pages, iter_head, start);
}
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;
pgoff_t index, count;
size_t size = maxsize, actual;
loff_t pos;
if (!size || !maxpages)
return 0;
pos = i->xarray_start + i->iov_offset;
index = pos >> PAGE_SHIFT;
offset = pos & ~PAGE_MASK;
*_start_offset = offset;
count = 1;
if (size > PAGE_SIZE - offset) {
size -= PAGE_SIZE - offset;
count += size >> PAGE_SHIFT;
size &= ~PAGE_MASK;
if (size)
count++;
}
if (count > maxpages)
count = maxpages;
nr = iter_xarray_populate_pages(pages, i->xarray, index, count);
if (nr == 0)
return 0;
actual = PAGE_SIZE * nr;
actual -= offset;
if (nr == count && size > 0) {
unsigned last_offset = (nr > 1) ? 0 : offset;
actual -= PAGE_SIZE - (last_offset + size);
}
return actual;
}
/* must be done on non-empty ITER_IOVEC one */
static unsigned long first_iovec_segment(const struct iov_iter *i,
size_t *size, size_t *start,
size_t maxsize, unsigned maxpages)
{
size_t skip;
long k;
for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
unsigned long addr = (unsigned long)i->iov[k].iov_base + skip;
size_t len = i->iov[k].iov_len - skip;
if (unlikely(!len))
continue;
if (len > maxsize)
len = maxsize;
len += (*start = addr % PAGE_SIZE);
if (len > maxpages * PAGE_SIZE)
len = maxpages * PAGE_SIZE;
*size = len;
return addr & PAGE_MASK;
}
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,
size_t maxsize, unsigned maxpages)
{
struct page *page;
size_t skip = i->iov_offset, len;
len = i->bvec->bv_len - skip;
if (len > maxsize)
len = maxsize;
skip += i->bvec->bv_offset;
page = i->bvec->bv_page + skip / PAGE_SIZE;
len += (*start = skip % PAGE_SIZE);
if (len > maxpages * PAGE_SIZE)
len = maxpages * PAGE_SIZE;
*size = len;
return page;
}
ssize_t iov_iter_get_pages(struct iov_iter *i,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
{
size_t len;
int n, res;
if (maxsize > i->count)
maxsize = i->count;
if (!maxsize)
return 0;
if (likely(iter_is_iovec(i))) {
unsigned long addr;
addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
n = DIV_ROUND_UP(len, PAGE_SIZE);
res = get_user_pages_fast(addr, n,
iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0,
pages);
if (unlikely(res < 0))
return res;
return (res == n ? len : res * PAGE_SIZE) - *start;
}
if (iov_iter_is_bvec(i)) {
struct page *page;
page = first_bvec_segment(i, &len, start, maxsize, maxpages);
n = DIV_ROUND_UP(len, PAGE_SIZE);
while (n--)
get_page(*pages++ = page++);
return len - *start;
}
if (iov_iter_is_pipe(i))
return pipe_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;
}
EXPORT_SYMBOL(iov_iter_get_pages);
static struct page **get_pages_array(size_t n)
{
return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
}
static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *start)
{
struct page **p;
unsigned int iter_head, npages;
ssize_t n;
if (!sanity(i))
return -EFAULT;
data_start(i, &iter_head, start);
/* Amount of free space: some of this one + all after this one */
npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
n = npages * PAGE_SIZE - *start;
if (maxsize > n)
maxsize = n;
else
npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
p = get_pages_array(npages);
if (!p)
return -ENOMEM;
n = __pipe_get_pages(i, maxsize, p, iter_head, start);
if (n > 0)
*pages = p;
else
kvfree(p);
return n;
}
static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *_start_offset)
{
struct page **p;
unsigned nr, offset;
pgoff_t index, count;
size_t size = maxsize, actual;
loff_t pos;
if (!size)
return 0;
pos = i->xarray_start + i->iov_offset;
index = pos >> PAGE_SHIFT;
offset = pos & ~PAGE_MASK;
*_start_offset = offset;
count = 1;
if (size > PAGE_SIZE - offset) {
size -= PAGE_SIZE - offset;
count += size >> PAGE_SHIFT;
size &= ~PAGE_MASK;
if (size)
count++;
}
p = get_pages_array(count);
if (!p)
return -ENOMEM;
*pages = p;
nr = iter_xarray_populate_pages(p, i->xarray, index, count);
if (nr == 0)
return 0;
actual = PAGE_SIZE * nr;
actual -= offset;
if (nr == count && size > 0) {
unsigned last_offset = (nr > 1) ? 0 : offset;
actual -= PAGE_SIZE - (last_offset + size);
}
return actual;
}
ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *start)
{
struct page **p;
size_t len;
int n, res;
if (maxsize > i->count)
maxsize = i->count;
if (!maxsize)
return 0;
if (likely(iter_is_iovec(i))) {
unsigned long addr;
addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
n = DIV_ROUND_UP(len, PAGE_SIZE);
p = get_pages_array(n);
if (!p)
return -ENOMEM;
res = get_user_pages_fast(addr, n,
iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0, p);
if (unlikely(res < 0)) {
kvfree(p);
return res;
}
*pages = p;
return (res == n ? len : res * PAGE_SIZE) - *start;
}
if (iov_iter_is_bvec(i)) {
struct page *page;
page = first_bvec_segment(i, &len, start, maxsize, ~0U);
n = DIV_ROUND_UP(len, PAGE_SIZE);
*pages = p = get_pages_array(n);
if (!p)
return -ENOMEM;
while (n--)
get_page(*p++ = page++);
return len - *start;
}
if (iov_iter_is_pipe(i))
return pipe_get_pages_alloc(i, pages, maxsize, start);
if (iov_iter_is_xarray(i))
return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
return -EFAULT;
}
EXPORT_SYMBOL(iov_iter_get_pages_alloc);
size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
struct iov_iter *i)
{
__wsum sum, next;
sum = *csum;
if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
WARN_ON(1);
return 0;
}
iterate_and_advance(i, bytes, base, len, off, ({
next = csum_and_copy_from_user(base, addr + off, len);
sum = csum_block_add(sum, next, off);
next ? 0 : len;
}), ({
sum = csum_and_memcpy(addr + off, base, len, sum, off);
})
)
*csum = sum;
return bytes;
}
EXPORT_SYMBOL(csum_and_copy_from_iter);
size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
struct iov_iter *i)
{
struct csum_state *csstate = _csstate;
__wsum sum, next;
if (unlikely(iov_iter_is_discard(i))) {
WARN_ON(1); /* for now */
return 0;
}
sum = csum_shift(csstate->csum, csstate->off);
if (unlikely(iov_iter_is_pipe(i)))
bytes = csum_and_copy_to_pipe_iter(addr, bytes, i, &sum);
else iterate_and_advance(i, bytes, base, len, off, ({
next = csum_and_copy_to_user(addr + off, base, len);
sum = csum_block_add(sum, next, off);
next ? 0 : len;
}), ({
sum = csum_and_memcpy(base, addr + off, len, sum, off);
})
)
csstate->csum = csum_shift(sum, csstate->off);
csstate->off += bytes;
return bytes;
}
EXPORT_SYMBOL(csum_and_copy_to_iter);
size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
struct iov_iter *i)
{
#ifdef CONFIG_CRYPTO_HASH
struct ahash_request *hash = hashp;
struct scatterlist sg;
size_t copied;
copied = copy_to_iter(addr, bytes, i);
sg_init_one(&sg, addr, copied);
ahash_request_set_crypt(hash, &sg, NULL, copied);
crypto_ahash_update(hash);
return copied;
#else
return 0;
#endif
}
EXPORT_SYMBOL(hash_and_copy_to_iter);
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 = i->iov; 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;
/* 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_pipe(i)) {
unsigned int iter_head;
int npages;
size_t off;
if (!sanity(i))
return 0;
data_start(i, &iter_head, &off);
/* some of this one + all after this one */
npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
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 (unlikely(iov_iter_is_pipe(new))) {
WARN_ON(1);
return NULL;
}
if (unlikely(iov_iter_is_discard(new) || iov_iter_is_xarray(new)))
return NULL;
if (iov_iter_is_bvec(new))
return new->bvec = kmemdup(new->bvec,
new->nr_segs * sizeof(struct bio_vec),
flags);
else
/* iovec and kvec have identical layout */
return new->iov = kmemdup(new->iov,
new->nr_segs * sizeof(struct iovec),
flags);
}
EXPORT_SYMBOL(dup_iter);
static int copy_compat_iovec_from_user(struct iovec *iov,
const struct iovec __user *uvec, unsigned long nr_segs)
{
const struct compat_iovec __user *uiov =
(const struct compat_iovec __user *)uvec;
int ret = -EFAULT, 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 int copy_iovec_from_user(struct iovec *iov,
const struct iovec __user *uvec, unsigned long nr_segs)
{
unsigned long seg;
if (copy_from_user(iov, uvec, nr_segs * sizeof(*uvec)))
return -EFAULT;
for (seg = 0; seg < nr_segs; seg++) {
if ((ssize_t)iov[seg].iov_len < 0)
return -EINVAL;
}
return 0;
}
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 (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;
}
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;
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_single_range(int rw, void __user *buf, size_t len,
struct iovec *iov, struct iov_iter *i)
{
if (len > MAX_RW_COUNT)
len = MAX_RW_COUNT;
if (unlikely(!access_ok(buf, len)))
return -EFAULT;
iov->iov_base = buf;
iov->iov_len = len;
iov_iter_init(i, rw, iov, 1, len);
return 0;
}
EXPORT_SYMBOL(import_single_range);
/**
* 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)) &&
!iov_iter_is_kvec(i))
return;
i->iov_offset = state->iov_offset;
i->count = state->count;
/*
* 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;
}