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