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-rw-r--r--lib/iov_iter.c1894
1 files changed, 1894 insertions, 0 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
new file mode 100644
index 000000000..c3ca28ca6
--- /dev/null
+++ b/lib/iov_iter.c
@@ -0,0 +1,1894 @@
+// 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 ubuf and kbuf alike */
+#define iterate_buf(i, n, base, len, off, __p, STEP) { \
+ size_t __maybe_unused off = 0; \
+ len = n; \
+ base = __p + i->iov_offset; \
+ len -= (STEP); \
+ i->iov_offset += len; \
+ n = len; \
+}
+
+/* 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 folio *folio; \
+ loff_t start = i->xarray_start + i->iov_offset; \
+ pgoff_t index = start / PAGE_SIZE; \
+ XA_STATE(xas, i->xarray, index); \
+ \
+ len = PAGE_SIZE - offset_in_page(start); \
+ rcu_read_lock(); \
+ xas_for_each(&xas, folio, ULONG_MAX) { \
+ unsigned left; \
+ size_t offset; \
+ if (xas_retry(&xas, folio)) \
+ continue; \
+ if (WARN_ON(xa_is_value(folio))) \
+ break; \
+ if (WARN_ON(folio_test_hugetlb(folio))) \
+ break; \
+ offset = offset_in_folio(folio, start + __off); \
+ while (offset < folio_size(folio)) { \
+ base = kmap_local_folio(folio, offset); \
+ len = min(n, len); \
+ left = (STEP); \
+ kunmap_local(base); \
+ len -= left; \
+ __off += len; \
+ n -= len; \
+ if (left || n == 0) \
+ goto __out; \
+ offset += len; \
+ len = PAGE_SIZE; \
+ } \
+ } \
+__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_ubuf(i))) { \
+ void __user *base; \
+ size_t len; \
+ iterate_buf(i, n, base, len, off, \
+ i->ubuf, (I)) \
+ } else 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)
+{
+ size_t res = n;
+
+ if (should_fail_usercopy())
+ return n;
+ if (access_ok(from, n)) {
+ instrument_copy_from_user_before(to, from, n);
+ res = raw_copy_from_user(to, from, n);
+ instrument_copy_from_user_after(to, from, n, res);
+ }
+ return res;
+}
+
+static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
+ unsigned int slot)
+{
+ return &pipe->bufs[slot & (pipe->ring_size - 1)];
+}
+
+#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_occupancy = pipe_occupancy(p_head, p_tail);
+ unsigned int i_head = i->head;
+ unsigned int idx;
+
+ if (i->last_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_buf(pipe, i_head);
+ if (unlikely(p->offset + p->len != abs(i->last_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 = %d\n", i_head, i->last_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 struct page *push_anon(struct pipe_inode_info *pipe, unsigned size)
+{
+ struct page *page = alloc_page(GFP_USER);
+ if (page) {
+ struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
+ *buf = (struct pipe_buffer) {
+ .ops = &default_pipe_buf_ops,
+ .page = page,
+ .offset = 0,
+ .len = size
+ };
+ }
+ return page;
+}
+
+static void push_page(struct pipe_inode_info *pipe, struct page *page,
+ unsigned int offset, unsigned int size)
+{
+ struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
+ *buf = (struct pipe_buffer) {
+ .ops = &page_cache_pipe_buf_ops,
+ .page = page,
+ .offset = offset,
+ .len = size
+ };
+ get_page(page);
+}
+
+static inline int last_offset(const struct pipe_buffer *buf)
+{
+ if (buf->ops == &default_pipe_buf_ops)
+ return buf->len; // buf->offset is 0 for those
+ else
+ return -(buf->offset + buf->len);
+}
+
+static struct page *append_pipe(struct iov_iter *i, size_t size,
+ unsigned int *off)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ int offset = i->last_offset;
+ struct pipe_buffer *buf;
+ struct page *page;
+
+ if (offset > 0 && offset < PAGE_SIZE) {
+ // some space in the last buffer; add to it
+ buf = pipe_buf(pipe, pipe->head - 1);
+ size = min_t(size_t, size, PAGE_SIZE - offset);
+ buf->len += size;
+ i->last_offset += size;
+ i->count -= size;
+ *off = offset;
+ return buf->page;
+ }
+ // OK, we need a new buffer
+ *off = 0;
+ size = min_t(size_t, size, PAGE_SIZE);
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+ return NULL;
+ page = push_anon(pipe, size);
+ if (!page)
+ return NULL;
+ i->head = pipe->head - 1;
+ i->last_offset = size;
+ i->count -= size;
+ return page;
+}
+
+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;
+ unsigned int head = pipe->head;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ if (offset && i->last_offset == -offset) { // could we merge it?
+ struct pipe_buffer *buf = pipe_buf(pipe, head - 1);
+ if (buf->page == page) {
+ buf->len += bytes;
+ i->last_offset -= bytes;
+ i->count -= bytes;
+ return bytes;
+ }
+ }
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+ return 0;
+
+ push_page(pipe, page, offset, bytes);
+ i->last_offset = -(offset + bytes);
+ i->head = head;
+ i->count -= bytes;
+ return bytes;
+}
+
+/*
+ * 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 = i->iov, 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 = i->iov, 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,
+ .user_backed = true,
+ .data_source = direction,
+ .iov = iov,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
+}
+EXPORT_SYMBOL(iov_iter_init);
+
+// returns the offset in partial buffer (if any)
+static inline unsigned int pipe_npages(const struct iov_iter *i, int *npages)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ int used = pipe->head - pipe->tail;
+ int off = i->last_offset;
+
+ *npages = max((int)pipe->max_usage - used, 0);
+
+ if (off > 0 && off < PAGE_SIZE) { // anon and not full
+ (*npages)++;
+ return off;
+ }
+ return 0;
+}
+
+static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ unsigned int off, chunk;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ for (size_t n = bytes; n; n -= chunk) {
+ struct page *page = append_pipe(i, n, &off);
+ chunk = min_t(size_t, n, PAGE_SIZE - off);
+ if (!page)
+ return bytes - n;
+ memcpy_to_page(page, off, addr, chunk);
+ addr += chunk;
+ }
+ 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)
+{
+ __wsum sum = *sump;
+ size_t off = 0;
+ unsigned int chunk, r;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ while (bytes) {
+ struct page *page = append_pipe(i, bytes, &r);
+ char *p;
+
+ if (!page)
+ break;
+ chunk = min_t(size_t, bytes, PAGE_SIZE - r);
+ p = kmap_local_page(page);
+ sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off);
+ kunmap_local(p);
+ off += chunk;
+ bytes -= chunk;
+ }
+ *sump = sum;
+ 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 (user_backed_iter(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)
+{
+ size_t xfer = 0;
+ unsigned int off, chunk;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ while (bytes) {
+ struct page *page = append_pipe(i, bytes, &off);
+ unsigned long rem;
+ char *p;
+
+ if (!page)
+ break;
+ chunk = min_t(size_t, bytes, PAGE_SIZE - off);
+ p = kmap_local_page(page);
+ rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
+ chunk -= rem;
+ kunmap_local(p);
+ xfer += chunk;
+ bytes -= chunk;
+ if (rem) {
+ iov_iter_revert(i, rem);
+ break;
+ }
+ }
+ 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 (user_backed_iter(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 (user_backed_iter(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;
+}
+
+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;
+ if (unlikely(iov_iter_is_pipe(i)))
+ return copy_page_to_iter_pipe(page, offset, bytes, i);
+ 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_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 size_t pipe_zero(size_t bytes, struct iov_iter *i)
+{
+ unsigned int chunk, off;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
+ if (!sanity(i))
+ return 0;
+
+ for (size_t n = bytes; n; n -= chunk) {
+ struct page *page = append_pipe(i, n, &off);
+ char *p;
+
+ if (!page)
+ return bytes - n;
+ chunk = min_t(size_t, n, PAGE_SIZE - off);
+ p = kmap_local_page(page);
+ memset(p + off, 0, chunk);
+ kunmap_local(p);
+ }
+ 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 void pipe_advance(struct iov_iter *i, size_t size)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ int off = i->last_offset;
+
+ if (!off && !size) {
+ pipe_discard_from(pipe, i->start_head); // discard everything
+ return;
+ }
+ i->count -= size;
+ while (1) {
+ struct pipe_buffer *buf = pipe_buf(pipe, i->head);
+ if (off) /* make it relative to the beginning of buffer */
+ size += abs(off) - buf->offset;
+ if (size <= buf->len) {
+ buf->len = size;
+ i->last_offset = last_offset(buf);
+ break;
+ }
+ size -= buf->len;
+ i->head++;
+ off = 0;
+ }
+ pipe_discard_from(pipe, i->head + 1); // discard everything past this one
+}
+
+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 = 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_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_pipe(i)) {
+ pipe_advance(i, 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 head = pipe->head;
+
+ while (head > i->start_head) {
+ struct pipe_buffer *b = pipe_buf(pipe, --head);
+ if (unroll < b->len) {
+ b->len -= unroll;
+ i->last_offset = last_offset(b);
+ i->head = head;
+ return;
+ }
+ unroll -= b->len;
+ pipe_buf_release(pipe, b);
+ pipe->head--;
+ }
+ i->last_offset = 0;
+ i->head = head;
+ 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) || 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 { /* 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,
+ .last_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 bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask,
+ unsigned len_mask)
+{
+ 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 > size)
+ len = size;
+ if (len & len_mask)
+ return false;
+ if ((unsigned long)(i->iov[k].iov_base + skip) & addr_mask)
+ return false;
+
+ size -= len;
+ if (!size)
+ break;
+ }
+ return true;
+}
+
+static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
+ unsigned len_mask)
+{
+ 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;
+
+ if (len > size)
+ len = size;
+ if (len & len_mask)
+ return false;
+ if ((unsigned long)(i->bvec[k].bv_offset + skip) & addr_mask)
+ return false;
+
+ size -= len;
+ if (!size)
+ break;
+ }
+ 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);
+
+ if (iov_iter_is_pipe(i)) {
+ size_t size = i->count;
+
+ if (size & len_mask)
+ return false;
+ if (size && i->last_offset > 0) {
+ if (i->last_offset & addr_mask)
+ return false;
+ }
+
+ return true;
+ }
+
+ if (iov_iter_is_xarray(i)) {
+ if (i->count & len_mask)
+ return false;
+ if ((i->xarray_start + 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)
+{
+ 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)
+{
+ 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);
+
+ if (iov_iter_is_pipe(i)) {
+ size_t size = i->count;
+
+ if (size && i->last_offset > 0)
+ return size | i->last_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 (iter_is_ubuf(i))
+ return 0;
+
+ 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 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 pipe_get_pages(struct iov_iter *i,
+ struct page ***pages, size_t maxsize, unsigned maxpages,
+ size_t *start)
+{
+ unsigned int npages, count, off, chunk;
+ struct page **p;
+ size_t left;
+
+ if (!sanity(i))
+ return -EFAULT;
+
+ *start = off = pipe_npages(i, &npages);
+ if (!npages)
+ return -EFAULT;
+ count = want_pages_array(pages, maxsize, off, min(npages, maxpages));
+ if (!count)
+ return -ENOMEM;
+ p = *pages;
+ for (npages = 0, left = maxsize ; npages < count; npages++, left -= chunk) {
+ struct page *page = append_pipe(i, left, &off);
+ if (!page)
+ break;
+ chunk = min_t(size_t, left, PAGE_SIZE - off);
+ get_page(*p++ = page);
+ }
+ if (!npages)
+ return -EFAULT;
+ return maxsize - left;
+}
+
+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) {
+ size_t len = i->iov[k].iov_len - skip;
+
+ if (unlikely(!len))
+ continue;
+ if (*size > len)
+ *size = len;
+ return (unsigned long)i->iov[k].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;
+
+ 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 int gup_flags = 0;
+ 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_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;
+}
+
+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);
+
+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;
+ 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_pipe(i)) {
+ int npages;
+
+ if (!sanity(i))
+ return 0;
+
+ pipe_npages(i, &npages);
+ 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 (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 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) && !iter_is_ubuf(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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-08 04:34:52 +0000