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https://github.com/freebsd/freebsd-src
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592 lines
16 KiB
C
592 lines
16 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause
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*
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* Copyright (c) 2007 Seccuris Inc.
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* All rights reserved.
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*
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* This software was developed by Robert N. M. Watson under contract to
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* Seccuris Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#include "opt_bpf.h"
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#include <sys/param.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/sf_buf.h>
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#include <sys/socket.h>
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#include <sys/uio.h>
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#include <machine/atomic.h>
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#include <net/if.h>
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#include <net/bpf.h>
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#include <net/bpf_zerocopy.h>
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#include <net/bpfdesc.h>
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#include <vm/vm.h>
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#include <vm/vm_param.h>
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#include <vm/pmap.h>
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#include <vm/vm_extern.h>
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#include <vm/vm_map.h>
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#include <vm/vm_page.h>
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/*
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* Zero-copy buffer scheme for BPF: user space "donates" two buffers, which
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* are mapped into the kernel address space using sf_bufs and used directly
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* by BPF. Memory is wired since page faults cannot be tolerated in the
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* contexts where the buffers are copied to (locks held, interrupt context,
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* etc). Access to shared memory buffers is synchronized using a header on
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* each buffer, allowing the number of system calls to go to zero as BPF
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* reaches saturation (buffers filled as fast as they can be drained by the
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* user process). Full details of the protocol for communicating between the
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* user process and BPF may be found in bpf(4).
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*/
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/*
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* Maximum number of pages per buffer. Since all BPF devices use two, the
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* maximum per device is 2*BPF_MAX_PAGES. Resource limits on the number of
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* sf_bufs may be an issue, so do not set this too high. On older systems,
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* kernel address space limits may also be an issue.
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*/
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#define BPF_MAX_PAGES 512
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/*
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* struct zbuf describes a memory buffer loaned by a user process to the
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* kernel. We represent this as a series of pages managed using an array of
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* sf_bufs. Even though the memory is contiguous in user space, it may not
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* be mapped contiguously in the kernel (i.e., a set of physically
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* non-contiguous pages in the direct map region) so we must implement
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* scatter-gather copying. One significant mitigating factor is that on
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* systems with a direct memory map, we can avoid TLB misses.
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*
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* At the front of the shared memory region is a bpf_zbuf_header, which
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* contains shared control data to allow user space and the kernel to
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* synchronize; this is included in zb_size, but not bpf_bufsize, so that BPF
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* knows that the space is not available.
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*/
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struct zbuf {
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vm_offset_t zb_uaddr; /* User address at time of setup. */
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size_t zb_size; /* Size of buffer, incl. header. */
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u_int zb_numpages; /* Number of pages. */
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int zb_flags; /* Flags on zbuf. */
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struct sf_buf **zb_pages; /* Pages themselves. */
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struct bpf_zbuf_header *zb_header; /* Shared header. */
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};
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/*
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* When a buffer has been assigned to userspace, flag it as such, as the
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* buffer may remain in the store position as a result of the user process
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* not yet having acknowledged the buffer in the hold position yet.
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*/
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#define ZBUF_FLAG_ASSIGNED 0x00000001 /* Set when owned by user. */
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/*
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* Release a page we've previously wired.
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*/
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static void
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zbuf_page_free(vm_page_t pp)
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{
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vm_page_unwire(pp, PQ_INACTIVE);
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}
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/*
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* Free an sf_buf with attached page.
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*/
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static void
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zbuf_sfbuf_free(struct sf_buf *sf)
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{
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vm_page_t pp;
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pp = sf_buf_page(sf);
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sf_buf_free(sf);
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zbuf_page_free(pp);
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}
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/*
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* Free a zbuf, including its page array, sbufs, and pages. Allow partially
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* allocated zbufs to be freed so that it may be used even during a zbuf
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* setup.
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*/
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static void
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zbuf_free(struct zbuf *zb)
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{
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int i;
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for (i = 0; i < zb->zb_numpages; i++) {
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if (zb->zb_pages[i] != NULL)
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zbuf_sfbuf_free(zb->zb_pages[i]);
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}
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free(zb->zb_pages, M_BPF);
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free(zb, M_BPF);
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}
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/*
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* Given a user pointer to a page of user memory, return an sf_buf for the
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* page. Because we may be requesting quite a few sf_bufs, prefer failure to
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* deadlock and use SFB_NOWAIT.
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*/
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static struct sf_buf *
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zbuf_sfbuf_get(struct vm_map *map, vm_offset_t uaddr)
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{
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struct sf_buf *sf;
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vm_page_t pp;
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if (vm_fault_quick_hold_pages(map, uaddr, PAGE_SIZE, VM_PROT_READ |
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VM_PROT_WRITE, &pp, 1) < 0)
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return (NULL);
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sf = sf_buf_alloc(pp, SFB_NOWAIT);
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if (sf == NULL) {
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zbuf_page_free(pp);
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return (NULL);
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}
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return (sf);
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}
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/*
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* Create a zbuf describing a range of user address space memory. Validate
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* page alignment, size requirements, etc.
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*/
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static int
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zbuf_setup(struct thread *td, vm_offset_t uaddr, size_t len,
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struct zbuf **zbp)
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{
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struct zbuf *zb;
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struct vm_map *map;
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int error, i;
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*zbp = NULL;
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/*
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* User address must be page-aligned.
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*/
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if (uaddr & PAGE_MASK)
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return (EINVAL);
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/*
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* Length must be an integer number of full pages.
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*/
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if (len & PAGE_MASK)
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return (EINVAL);
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/*
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* Length must not exceed per-buffer resource limit.
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*/
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if ((len / PAGE_SIZE) > BPF_MAX_PAGES)
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return (EINVAL);
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/*
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* Allocate the buffer and set up each page with is own sf_buf.
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*/
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error = 0;
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zb = malloc(sizeof(*zb), M_BPF, M_ZERO | M_WAITOK);
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zb->zb_uaddr = uaddr;
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zb->zb_size = len;
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zb->zb_numpages = len / PAGE_SIZE;
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zb->zb_pages = malloc(sizeof(struct sf_buf *) *
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zb->zb_numpages, M_BPF, M_ZERO | M_WAITOK);
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map = &td->td_proc->p_vmspace->vm_map;
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for (i = 0; i < zb->zb_numpages; i++) {
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zb->zb_pages[i] = zbuf_sfbuf_get(map,
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uaddr + (i * PAGE_SIZE));
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if (zb->zb_pages[i] == NULL) {
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error = EFAULT;
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goto error;
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}
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}
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zb->zb_header =
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(struct bpf_zbuf_header *)sf_buf_kva(zb->zb_pages[0]);
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bzero(zb->zb_header, sizeof(*zb->zb_header));
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*zbp = zb;
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return (0);
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error:
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zbuf_free(zb);
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return (error);
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}
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/*
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* Copy bytes from a source into the specified zbuf. The caller is
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* responsible for performing bounds checking, etc.
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*/
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void
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bpf_zerocopy_append_bytes(struct bpf_d *d, caddr_t buf, u_int offset,
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void *src, u_int len)
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{
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u_int count, page, poffset;
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u_char *src_bytes;
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_append_bytes: not in zbuf mode"));
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KASSERT(buf != NULL, ("bpf_zerocopy_append_bytes: NULL buf"));
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src_bytes = (u_char *)src;
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zb = (struct zbuf *)buf;
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KASSERT((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0,
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("bpf_zerocopy_append_bytes: ZBUF_FLAG_ASSIGNED"));
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/*
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* Scatter-gather copy to user pages mapped into kernel address space
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* using sf_bufs: copy up to a page at a time.
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*/
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offset += sizeof(struct bpf_zbuf_header);
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page = offset / PAGE_SIZE;
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poffset = offset % PAGE_SIZE;
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while (len > 0) {
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KASSERT(page < zb->zb_numpages, ("bpf_zerocopy_append_bytes:"
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" page overflow (%d p %d np)\n", page, zb->zb_numpages));
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count = min(len, PAGE_SIZE - poffset);
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bcopy(src_bytes, ((u_char *)sf_buf_kva(zb->zb_pages[page])) +
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poffset, count);
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poffset += count;
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if (poffset == PAGE_SIZE) {
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poffset = 0;
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page++;
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}
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KASSERT(poffset < PAGE_SIZE,
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("bpf_zerocopy_append_bytes: page offset overflow (%d)",
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poffset));
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len -= count;
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src_bytes += count;
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}
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}
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/*
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* Copy bytes from an mbuf chain to the specified zbuf: copying will be
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* scatter-gather both from mbufs, which may be fragmented over memory, and
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* to pages, which may not be contiguously mapped in kernel address space.
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* As with bpf_zerocopy_append_bytes(), the caller is responsible for
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* checking that this will not exceed the buffer limit.
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*/
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void
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bpf_zerocopy_append_mbuf(struct bpf_d *d, caddr_t buf, u_int offset,
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void *src, u_int len)
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{
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u_int count, moffset, page, poffset;
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const struct mbuf *m;
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_append_mbuf not in zbuf mode"));
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KASSERT(buf != NULL, ("bpf_zerocopy_append_mbuf: NULL buf"));
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m = (struct mbuf *)src;
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zb = (struct zbuf *)buf;
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KASSERT((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0,
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("bpf_zerocopy_append_mbuf: ZBUF_FLAG_ASSIGNED"));
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/*
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* Scatter gather both from an mbuf chain and to a user page set
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* mapped into kernel address space using sf_bufs. If we're lucky,
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* each mbuf requires one copy operation, but if page alignment and
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* mbuf alignment work out less well, we'll be doing two copies per
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* mbuf.
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*/
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offset += sizeof(struct bpf_zbuf_header);
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page = offset / PAGE_SIZE;
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poffset = offset % PAGE_SIZE;
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moffset = 0;
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while (len > 0) {
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KASSERT(page < zb->zb_numpages,
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("bpf_zerocopy_append_mbuf: page overflow (%d p %d "
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"np)\n", page, zb->zb_numpages));
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KASSERT(m != NULL,
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("bpf_zerocopy_append_mbuf: end of mbuf chain"));
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count = min(m->m_len - moffset, len);
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count = min(count, PAGE_SIZE - poffset);
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bcopy(mtod(m, u_char *) + moffset,
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((u_char *)sf_buf_kva(zb->zb_pages[page])) + poffset,
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count);
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poffset += count;
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if (poffset == PAGE_SIZE) {
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poffset = 0;
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page++;
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}
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KASSERT(poffset < PAGE_SIZE,
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("bpf_zerocopy_append_mbuf: page offset overflow (%d)",
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poffset));
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moffset += count;
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if (moffset == m->m_len) {
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m = m->m_next;
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moffset = 0;
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}
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len -= count;
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}
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}
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/*
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* Notification from the BPF framework that a buffer in the store position is
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* rejecting packets and may be considered full. We mark the buffer as
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* immutable and assign to userspace so that it is immediately available for
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* the user process to access.
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*/
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void
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bpf_zerocopy_buffull(struct bpf_d *d)
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{
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_buffull: not in zbuf mode"));
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zb = (struct zbuf *)d->bd_sbuf;
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KASSERT(zb != NULL, ("bpf_zerocopy_buffull: zb == NULL"));
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if ((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0) {
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zb->zb_flags |= ZBUF_FLAG_ASSIGNED;
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zb->zb_header->bzh_kernel_len = d->bd_slen;
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atomic_add_rel_int(&zb->zb_header->bzh_kernel_gen, 1);
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}
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}
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/*
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* Notification from the BPF framework that a buffer has moved into the held
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* slot on a descriptor. Zero-copy BPF will update the shared page to let
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* the user process know and flag the buffer as assigned if it hasn't already
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* been marked assigned due to filling while it was in the store position.
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*
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* Note: identical logic as in bpf_zerocopy_buffull(), except that we operate
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* on bd_hbuf and bd_hlen.
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*/
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void
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bpf_zerocopy_bufheld(struct bpf_d *d)
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{
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_bufheld: not in zbuf mode"));
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zb = (struct zbuf *)d->bd_hbuf;
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KASSERT(zb != NULL, ("bpf_zerocopy_bufheld: zb == NULL"));
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if ((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0) {
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zb->zb_flags |= ZBUF_FLAG_ASSIGNED;
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zb->zb_header->bzh_kernel_len = d->bd_hlen;
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atomic_add_rel_int(&zb->zb_header->bzh_kernel_gen, 1);
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}
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}
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/*
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* Notification from the BPF framework that the free buffer has been been
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* rotated out of the held position to the free position. This happens when
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* the user acknowledges the held buffer.
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*/
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void
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bpf_zerocopy_buf_reclaimed(struct bpf_d *d)
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{
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_reclaim_buf: not in zbuf mode"));
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KASSERT(d->bd_fbuf != NULL,
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("bpf_zerocopy_buf_reclaimed: NULL free buf"));
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zb = (struct zbuf *)d->bd_fbuf;
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zb->zb_flags &= ~ZBUF_FLAG_ASSIGNED;
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}
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/*
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* Query from the BPF framework regarding whether the buffer currently in the
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* held position can be moved to the free position, which can be indicated by
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* the user process making their generation number equal to the kernel
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* generation number.
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*/
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int
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bpf_zerocopy_canfreebuf(struct bpf_d *d)
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{
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_canfreebuf: not in zbuf mode"));
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zb = (struct zbuf *)d->bd_hbuf;
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if (zb == NULL)
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return (0);
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if (zb->zb_header->bzh_kernel_gen ==
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atomic_load_acq_int(&zb->zb_header->bzh_user_gen))
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return (1);
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return (0);
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}
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/*
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* Query from the BPF framework as to whether or not the buffer current in
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* the store position can actually be written to. This may return false if
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* the store buffer is assigned to userspace before the hold buffer is
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* acknowledged.
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*/
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int
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bpf_zerocopy_canwritebuf(struct bpf_d *d)
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{
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_canwritebuf: not in zbuf mode"));
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zb = (struct zbuf *)d->bd_sbuf;
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KASSERT(zb != NULL, ("bpf_zerocopy_canwritebuf: bd_sbuf NULL"));
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if (zb->zb_flags & ZBUF_FLAG_ASSIGNED)
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return (0);
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return (1);
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}
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/*
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* Free zero copy buffers at request of descriptor.
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*/
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void
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bpf_zerocopy_free(struct bpf_d *d)
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{
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struct zbuf *zb;
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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("bpf_zerocopy_free: not in zbuf mode"));
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zb = (struct zbuf *)d->bd_sbuf;
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if (zb != NULL)
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zbuf_free(zb);
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zb = (struct zbuf *)d->bd_hbuf;
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if (zb != NULL)
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zbuf_free(zb);
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zb = (struct zbuf *)d->bd_fbuf;
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if (zb != NULL)
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zbuf_free(zb);
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}
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/*
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* Ioctl to return the maximum buffer size.
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*/
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int
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bpf_zerocopy_ioctl_getzmax(struct thread *td, struct bpf_d *d, size_t *i)
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{
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KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
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|
("bpf_zerocopy_ioctl_getzmax: not in zbuf mode"));
|
|
|
|
*i = BPF_MAX_PAGES * PAGE_SIZE;
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Ioctl to force rotation of the two buffers, if there's any data available.
|
|
* This can be used by user space to implement timeouts when waiting for a
|
|
* buffer to fill.
|
|
*/
|
|
int
|
|
bpf_zerocopy_ioctl_rotzbuf(struct thread *td, struct bpf_d *d,
|
|
struct bpf_zbuf *bz)
|
|
{
|
|
struct zbuf *bzh;
|
|
|
|
bzero(bz, sizeof(*bz));
|
|
BPFD_LOCK(d);
|
|
if (d->bd_hbuf == NULL && d->bd_slen != 0) {
|
|
ROTATE_BUFFERS(d);
|
|
bzh = (struct zbuf *)d->bd_hbuf;
|
|
bz->bz_bufa = (void *)bzh->zb_uaddr;
|
|
bz->bz_buflen = d->bd_hlen;
|
|
}
|
|
BPFD_UNLOCK(d);
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Ioctl to configure zero-copy buffers -- may be done only once.
|
|
*/
|
|
int
|
|
bpf_zerocopy_ioctl_setzbuf(struct thread *td, struct bpf_d *d,
|
|
struct bpf_zbuf *bz)
|
|
{
|
|
struct zbuf *zba, *zbb;
|
|
int error;
|
|
|
|
KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
|
|
("bpf_zerocopy_ioctl_setzbuf: not in zbuf mode"));
|
|
|
|
/*
|
|
* Must set both buffers. Cannot clear them.
|
|
*/
|
|
if (bz->bz_bufa == NULL || bz->bz_bufb == NULL)
|
|
return (EINVAL);
|
|
|
|
/*
|
|
* Buffers must have a size greater than 0. Alignment and other size
|
|
* validity checking is done in zbuf_setup().
|
|
*/
|
|
if (bz->bz_buflen == 0)
|
|
return (EINVAL);
|
|
|
|
/*
|
|
* Allocate new buffers.
|
|
*/
|
|
error = zbuf_setup(td, (vm_offset_t)bz->bz_bufa, bz->bz_buflen,
|
|
&zba);
|
|
if (error)
|
|
return (error);
|
|
error = zbuf_setup(td, (vm_offset_t)bz->bz_bufb, bz->bz_buflen,
|
|
&zbb);
|
|
if (error) {
|
|
zbuf_free(zba);
|
|
return (error);
|
|
}
|
|
|
|
/*
|
|
* We only allow buffers to be installed once, so atomically check
|
|
* that no buffers are currently installed and install new buffers.
|
|
*/
|
|
BPFD_LOCK(d);
|
|
if (d->bd_hbuf != NULL || d->bd_sbuf != NULL || d->bd_fbuf != NULL ||
|
|
d->bd_bif != NULL) {
|
|
BPFD_UNLOCK(d);
|
|
zbuf_free(zba);
|
|
zbuf_free(zbb);
|
|
return (EINVAL);
|
|
}
|
|
|
|
/*
|
|
* Point BPF descriptor at buffers; initialize sbuf as zba so that
|
|
* it is always filled first in the sequence, per bpf(4).
|
|
*/
|
|
d->bd_fbuf = (caddr_t)zbb;
|
|
d->bd_sbuf = (caddr_t)zba;
|
|
d->bd_slen = 0;
|
|
d->bd_hlen = 0;
|
|
|
|
/*
|
|
* We expose only the space left in the buffer after the size of the
|
|
* shared management region.
|
|
*/
|
|
d->bd_bufsize = bz->bz_buflen - sizeof(struct bpf_zbuf_header);
|
|
BPFD_UNLOCK(d);
|
|
return (0);
|
|
}
|