1a028e5072
This reverts eefa390628
The simplification made in that change works with the assumption that
the 'offset' parameter to these functions is always positive or zero,
which is not true. It can be and often is negative in order to access
SKB header values in front of skb->data.
Signed-off-by: David S. Miller <davem@davemloft.net>
133 lines
3.3 KiB
C
133 lines
3.3 KiB
C
/*
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* Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
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* Portions based on net/core/datagram.c and copyrighted by their authors.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 59
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* Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* The full GNU General Public License is included in this distribution in the
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* file called COPYING.
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*/
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/*
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* This code allows the net stack to make use of a DMA engine for
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* skb to iovec copies.
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*/
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#include <linux/dmaengine.h>
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#include <linux/socket.h>
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#include <linux/rtnetlink.h> /* for BUG_TRAP */
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#include <net/tcp.h>
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#include <net/netdma.h>
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#define NET_DMA_DEFAULT_COPYBREAK 4096
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int sysctl_tcp_dma_copybreak = NET_DMA_DEFAULT_COPYBREAK;
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/**
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* dma_skb_copy_datagram_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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* @iovec - io vector to copy to
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* @len - amount of data to copy from buffer to iovec
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* @pinned_list - locked iovec buffer data
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*
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* Note: the iovec is modified during the copy.
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*/
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int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
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struct sk_buff *skb, int offset, struct iovec *to,
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size_t len, struct dma_pinned_list *pinned_list)
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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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dma_cookie_t cookie = 0;
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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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cookie = dma_memcpy_to_iovec(chan, to, pinned_list,
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skb->data + offset, copy);
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if (cookie < 0)
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goto fault;
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len -= copy;
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if (len == 0)
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goto end;
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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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BUG_TRAP(start <= offset + len);
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end = start + skb_shinfo(skb)->frags[i].size;
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copy = end - offset;
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if ((copy = end - offset) > 0) {
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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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cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,
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frag->page_offset + offset - start, copy);
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if (cookie < 0)
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goto fault;
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len -= copy;
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if (len == 0)
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goto end;
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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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BUG_TRAP(start <= offset + len);
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end = start + list->len;
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copy = end - offset;
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if (copy > 0) {
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if (copy > len)
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copy = len;
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cookie = dma_skb_copy_datagram_iovec(chan, list,
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offset - start, to, copy,
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pinned_list);
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if (cookie < 0)
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goto fault;
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len -= copy;
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if (len == 0)
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goto end;
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offset += copy;
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}
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start = end;
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}
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}
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end:
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if (!len) {
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skb->dma_cookie = cookie;
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return cookie;
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}
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fault:
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return -EFAULT;
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}
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