net: skb_copy_datagram_const_iovec()
There's an skb_copy_datagram_iovec() to copy out of a paged skb, but it modifies the iovec, and does not support starting at an offset in the destination. We want both in tun.c, so let's add the function. It's a carbon copy of skb_copy_datagram_iovec() with enough changes to be annoying. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -1717,6 +1717,11 @@ extern int skb_copy_datagram_from_iovec(struct sk_buff *skb,
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int offset,
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struct iovec *from,
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int len);
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extern int skb_copy_datagram_const_iovec(const struct sk_buff *from,
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int offset,
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const struct iovec *to,
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int to_offset,
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int size);
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extern void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
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extern int skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
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unsigned int flags);
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@ -318,6 +318,8 @@ extern int csum_partial_copy_fromiovecend(unsigned char *kdata,
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extern int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode);
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extern int memcpy_toiovec(struct iovec *v, unsigned char *kdata, int len);
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extern int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,
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int offset, int len);
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extern int move_addr_to_user(struct sockaddr *kaddr, int klen, void __user *uaddr, int __user *ulen);
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extern int move_addr_to_kernel(void __user *uaddr, int ulen, struct sockaddr *kaddr);
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extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
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@ -338,6 +338,98 @@ fault:
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return -EFAULT;
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}
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/**
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* skb_copy_datagram_const_iovec - Copy a datagram to an iovec.
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* @skb: buffer to copy
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* @offset: offset in the buffer to start copying from
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* @to: io vector to copy to
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* @to_offset: offset in the io vector to start copying to
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* @len: amount of data to copy from buffer to iovec
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*
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* Returns 0 or -EFAULT.
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* Note: the iovec is not modified during the copy.
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*/
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int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,
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const struct iovec *to, int to_offset,
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int len)
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{
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int start = skb_headlen(skb);
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int i, copy = start - offset;
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/* Copy header. */
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if (copy > 0) {
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if (copy > len)
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copy = len;
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if (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))
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goto fault;
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if ((len -= copy) == 0)
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return 0;
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offset += copy;
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to_offset += copy;
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}
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/* Copy paged appendix. Hmm... why does this look so complicated? */
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for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
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int end;
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WARN_ON(start > offset + len);
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end = start + skb_shinfo(skb)->frags[i].size;
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if ((copy = end - offset) > 0) {
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int err;
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u8 *vaddr;
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skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
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struct page *page = frag->page;
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if (copy > len)
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copy = len;
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vaddr = kmap(page);
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err = memcpy_toiovecend(to, vaddr + frag->page_offset +
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offset - start, to_offset, copy);
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kunmap(page);
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if (err)
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goto fault;
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if (!(len -= copy))
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return 0;
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offset += copy;
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to_offset += copy;
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}
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start = end;
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}
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if (skb_shinfo(skb)->frag_list) {
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struct sk_buff *list = skb_shinfo(skb)->frag_list;
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for (; list; list = list->next) {
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int end;
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WARN_ON(start > offset + len);
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end = start + list->len;
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if ((copy = end - offset) > 0) {
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if (copy > len)
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copy = len;
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if (skb_copy_datagram_const_iovec(list,
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offset - start,
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to, to_offset,
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copy))
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goto fault;
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if ((len -= copy) == 0)
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return 0;
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offset += copy;
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to_offset += copy;
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}
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start = end;
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}
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}
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if (!len)
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return 0;
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fault:
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return -EFAULT;
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}
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EXPORT_SYMBOL(skb_copy_datagram_const_iovec);
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/**
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* skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
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* @skb: buffer to copy
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@ -97,6 +97,31 @@ int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len)
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return 0;
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}
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/*
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* Copy kernel to iovec. Returns -EFAULT on error.
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*/
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int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,
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int offset, int len)
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{
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int copy;
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for (; len > 0; ++iov) {
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/* Skip over the finished iovecs */
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if (unlikely(offset >= iov->iov_len)) {
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offset -= iov->iov_len;
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continue;
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}
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copy = min_t(unsigned int, iov->iov_len - offset, len);
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offset = 0;
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if (copy_to_user(iov->iov_base, kdata, copy))
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return -EFAULT;
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kdata += copy;
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len -= copy;
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}
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return 0;
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}
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/*
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* Copy iovec to kernel. Returns -EFAULT on error.
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*
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@ -236,3 +261,4 @@ EXPORT_SYMBOL(csum_partial_copy_fromiovecend);
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EXPORT_SYMBOL(memcpy_fromiovec);
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EXPORT_SYMBOL(memcpy_fromiovecend);
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EXPORT_SYMBOL(memcpy_toiovec);
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EXPORT_SYMBOL(memcpy_toiovecend);
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