Commit 0a1ec07a authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by David S. Miller

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: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0cededf3
......@@ -1717,6 +1717,11 @@ extern int skb_copy_datagram_from_iovec(struct sk_buff *skb,
int offset,
struct iovec *from,
int len);
extern int skb_copy_datagram_const_iovec(const struct sk_buff *from,
int offset,
const struct iovec *to,
int to_offset,
int size);
extern void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
extern int skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
unsigned int flags);
......
......@@ -318,6 +318,8 @@ extern int csum_partial_copy_fromiovecend(unsigned char *kdata,
extern int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode);
extern int memcpy_toiovec(struct iovec *v, unsigned char *kdata, int len);
extern int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,
int offset, int len);
extern int move_addr_to_user(struct sockaddr *kaddr, int klen, void __user *uaddr, int __user *ulen);
extern int move_addr_to_kernel(void __user *uaddr, int ulen, struct sockaddr *kaddr);
extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
......
......@@ -338,6 +338,98 @@ fault:
return -EFAULT;
}
/**
* skb_copy_datagram_const_iovec - Copy a datagram to an iovec.
* @skb: buffer to copy
* @offset: offset in the buffer to start copying from
* @to: io vector to copy to
* @to_offset: offset in the io vector to start copying to
* @len: amount of data to copy from buffer to iovec
*
* Returns 0 or -EFAULT.
* Note: the iovec is not modified during the copy.
*/
int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,
const struct iovec *to, int to_offset,
int len)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
/* Copy header. */
if (copy > 0) {
if (copy > len)
copy = len;
if (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
to_offset += copy;
}
/* Copy paged appendix. Hmm... why does this look so complicated? */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
int end;
WARN_ON(start > offset + len);
end = start + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
int err;
u8 *vaddr;
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
struct page *page = frag->page;
if (copy > len)
copy = len;
vaddr = kmap(page);
err = memcpy_toiovecend(to, vaddr + frag->page_offset +
offset - start, to_offset, copy);
kunmap(page);
if (err)
goto fault;
if (!(len -= copy))
return 0;
offset += copy;
to_offset += copy;
}
start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
int end;
WARN_ON(start > offset + len);
end = start + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
if (skb_copy_datagram_const_iovec(list,
offset - start,
to, to_offset,
copy))
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
to_offset += copy;
}
start = end;
}
}
if (!len)
return 0;
fault:
return -EFAULT;
}
EXPORT_SYMBOL(skb_copy_datagram_const_iovec);
/**
* skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
* @skb: buffer to copy
......
......@@ -97,6 +97,31 @@ int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len)
return 0;
}
/*
* Copy kernel to iovec. Returns -EFAULT on error.
*/
int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,
int offset, int len)
{
int copy;
for (; len > 0; ++iov) {
/* Skip over the finished iovecs */
if (unlikely(offset >= iov->iov_len)) {
offset -= iov->iov_len;
continue;
}
copy = min_t(unsigned int, iov->iov_len - offset, len);
offset = 0;
if (copy_to_user(iov->iov_base, kdata, copy))
return -EFAULT;
kdata += copy;
len -= copy;
}
return 0;
}
/*
* Copy iovec to kernel. Returns -EFAULT on error.
*
......@@ -236,3 +261,4 @@ EXPORT_SYMBOL(csum_partial_copy_fromiovecend);
EXPORT_SYMBOL(memcpy_fromiovec);
EXPORT_SYMBOL(memcpy_fromiovecend);
EXPORT_SYMBOL(memcpy_toiovec);
EXPORT_SYMBOL(memcpy_toiovecend);
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