2 * Copyright (c) 2007 Seccuris Inc.
5 * This sofware was developed by Robert N. M. Watson under contract to
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
35 #include <sys/param.h>
37 #include <sys/malloc.h>
39 #include <sys/mutex.h>
41 #include <sys/sf_buf.h>
42 #include <sys/socket.h>
45 #include <machine/atomic.h>
49 #include <net/bpf_zerocopy.h>
50 #include <net/bpfdesc.h>
54 #include <vm/vm_extern.h>
55 #include <vm/vm_map.h>
56 #include <vm/vm_page.h>
59 * Zero-copy buffer scheme for BPF: user space "donates" two buffers, which
60 * are mapped into the kernel address space using sf_bufs and used directly
61 * by BPF. Memory is wired since page faults cannot be tolerated in the
62 * contexts where the buffers are copied to (locks held, interrupt context,
63 * etc). Access to shared memory buffers is synchronized using a header on
64 * each buffer, allowing the number of system calls to go to zero as BPF
65 * reaches saturation (buffers filled as fast as they can be drained by the
66 * user process). Full details of the protocol for communicating between the
67 * user process and BPF may be found in bpf(4).
71 * Maximum number of pages per buffer. Since all BPF devices use two, the
72 * maximum per device is 2*BPF_MAX_PAGES. Resource limits on the number of
73 * sf_bufs may be an issue, so do not set this too high. On older systems,
74 * kernel address space limits may also be an issue.
76 #define BPF_MAX_PAGES 512
79 * struct zbuf describes a memory buffer loaned by a user process to the
80 * kernel. We represent this as a series of pages managed using an array of
81 * sf_bufs. Even though the memory is contiguous in user space, it may not
82 * be mapped contiguously in the kernel (i.e., a set of physically
83 * non-contiguous pages in the direct map region) so we must implement
84 * scatter-gather copying. One significant mitigating factor is that on
85 * systems with a direct memory map, we can avoid TLB misses.
87 * At the front of the shared memory region is a bpf_zbuf_header, which
88 * contains shared control data to allow user space and the kernel to
89 * synchronize; this is included in zb_size, but not bpf_bufsize, so that BPF
90 * knows that the space is not available.
93 vm_offset_t zb_uaddr; /* User address at time of setup. */
94 size_t zb_size; /* Size of buffer, incl. header. */
95 u_int zb_numpages; /* Number of pages. */
96 int zb_flags; /* Flags on zbuf. */
97 struct sf_buf **zb_pages; /* Pages themselves. */
98 struct bpf_zbuf_header *zb_header; /* Shared header. */
102 * When a buffer has been assigned to userspace, flag it as such, as the
103 * buffer may remain in the store position as a result of the user process
104 * not yet having acknowledged the buffer in the hold position yet.
106 #define ZBUF_FLAG_ASSIGNED 0x00000001 /* Set when owned by user. */
109 * Release a page we've previously wired.
112 zbuf_page_free(vm_page_t pp)
116 vm_page_unwire(pp, 0);
117 if (pp->wire_count == 0 && pp->object == NULL)
123 * Free an sf_buf with attached page.
126 zbuf_sfbuf_free(struct sf_buf *sf)
130 pp = sf_buf_page(sf);
136 * Free a zbuf, including its page array, sbufs, and pages. Allow partially
137 * allocated zbufs to be freed so that it may be used even during a zbuf
141 zbuf_free(struct zbuf *zb)
145 for (i = 0; i < zb->zb_numpages; i++) {
146 if (zb->zb_pages[i] != NULL)
147 zbuf_sfbuf_free(zb->zb_pages[i]);
149 free(zb->zb_pages, M_BPF);
154 * Given a user pointer to a page of user memory, return an sf_buf for the
155 * page. Because we may be requesting quite a few sf_bufs, prefer failure to
156 * deadlock and use SFB_NOWAIT.
158 static struct sf_buf *
159 zbuf_sfbuf_get(struct vm_map *map, vm_offset_t uaddr)
164 if (vm_fault_quick_hold_pages(map, uaddr, PAGE_SIZE, VM_PROT_READ |
165 VM_PROT_WRITE, &pp, 1) < 0)
171 sf = sf_buf_alloc(pp, SFB_NOWAIT);
180 * Create a zbuf describing a range of user address space memory. Validate
181 * page alignment, size requirements, etc.
184 zbuf_setup(struct thread *td, vm_offset_t uaddr, size_t len,
194 * User address must be page-aligned.
196 if (uaddr & PAGE_MASK)
200 * Length must be an integer number of full pages.
206 * Length must not exceed per-buffer resource limit.
208 if ((len / PAGE_SIZE) > BPF_MAX_PAGES)
212 * Allocate the buffer and set up each page with is own sf_buf.
215 zb = malloc(sizeof(*zb), M_BPF, M_ZERO | M_WAITOK);
216 zb->zb_uaddr = uaddr;
218 zb->zb_numpages = len / PAGE_SIZE;
219 zb->zb_pages = malloc(sizeof(struct sf_buf *) *
220 zb->zb_numpages, M_BPF, M_ZERO | M_WAITOK);
221 map = &td->td_proc->p_vmspace->vm_map;
222 for (i = 0; i < zb->zb_numpages; i++) {
223 zb->zb_pages[i] = zbuf_sfbuf_get(map,
224 uaddr + (i * PAGE_SIZE));
225 if (zb->zb_pages[i] == NULL) {
231 (struct bpf_zbuf_header *)sf_buf_kva(zb->zb_pages[0]);
232 bzero(zb->zb_header, sizeof(*zb->zb_header));
242 * Copy bytes from a source into the specified zbuf. The caller is
243 * responsible for performing bounds checking, etc.
246 bpf_zerocopy_append_bytes(struct bpf_d *d, caddr_t buf, u_int offset,
247 void *src, u_int len)
249 u_int count, page, poffset;
253 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
254 ("bpf_zerocopy_append_bytes: not in zbuf mode"));
255 KASSERT(buf != NULL, ("bpf_zerocopy_append_bytes: NULL buf"));
257 src_bytes = (u_char *)src;
258 zb = (struct zbuf *)buf;
260 KASSERT((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0,
261 ("bpf_zerocopy_append_bytes: ZBUF_FLAG_ASSIGNED"));
264 * Scatter-gather copy to user pages mapped into kernel address space
265 * using sf_bufs: copy up to a page at a time.
267 offset += sizeof(struct bpf_zbuf_header);
268 page = offset / PAGE_SIZE;
269 poffset = offset % PAGE_SIZE;
271 KASSERT(page < zb->zb_numpages, ("bpf_zerocopy_append_bytes:"
272 " page overflow (%d p %d np)\n", page, zb->zb_numpages));
274 count = min(len, PAGE_SIZE - poffset);
275 bcopy(src_bytes, ((u_char *)sf_buf_kva(zb->zb_pages[page])) +
278 if (poffset == PAGE_SIZE) {
282 KASSERT(poffset < PAGE_SIZE,
283 ("bpf_zerocopy_append_bytes: page offset overflow (%d)",
291 * Copy bytes from an mbuf chain to the specified zbuf: copying will be
292 * scatter-gather both from mbufs, which may be fragmented over memory, and
293 * to pages, which may not be contiguously mapped in kernel address space.
294 * As with bpf_zerocopy_append_bytes(), the caller is responsible for
295 * checking that this will not exceed the buffer limit.
298 bpf_zerocopy_append_mbuf(struct bpf_d *d, caddr_t buf, u_int offset,
299 void *src, u_int len)
301 u_int count, moffset, page, poffset;
302 const struct mbuf *m;
305 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
306 ("bpf_zerocopy_append_mbuf not in zbuf mode"));
307 KASSERT(buf != NULL, ("bpf_zerocopy_append_mbuf: NULL buf"));
309 m = (struct mbuf *)src;
310 zb = (struct zbuf *)buf;
312 KASSERT((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0,
313 ("bpf_zerocopy_append_mbuf: ZBUF_FLAG_ASSIGNED"));
316 * Scatter gather both from an mbuf chain and to a user page set
317 * mapped into kernel address space using sf_bufs. If we're lucky,
318 * each mbuf requires one copy operation, but if page alignment and
319 * mbuf alignment work out less well, we'll be doing two copies per
322 offset += sizeof(struct bpf_zbuf_header);
323 page = offset / PAGE_SIZE;
324 poffset = offset % PAGE_SIZE;
327 KASSERT(page < zb->zb_numpages,
328 ("bpf_zerocopy_append_mbuf: page overflow (%d p %d "
329 "np)\n", page, zb->zb_numpages));
331 ("bpf_zerocopy_append_mbuf: end of mbuf chain"));
333 count = min(m->m_len - moffset, len);
334 count = min(count, PAGE_SIZE - poffset);
335 bcopy(mtod(m, u_char *) + moffset,
336 ((u_char *)sf_buf_kva(zb->zb_pages[page])) + poffset,
339 if (poffset == PAGE_SIZE) {
343 KASSERT(poffset < PAGE_SIZE,
344 ("bpf_zerocopy_append_mbuf: page offset overflow (%d)",
347 if (moffset == m->m_len) {
356 * Notification from the BPF framework that a buffer in the store position is
357 * rejecting packets and may be considered full. We mark the buffer as
358 * immutable and assign to userspace so that it is immediately available for
359 * the user process to access.
362 bpf_zerocopy_buffull(struct bpf_d *d)
366 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
367 ("bpf_zerocopy_buffull: not in zbuf mode"));
369 zb = (struct zbuf *)d->bd_sbuf;
370 KASSERT(zb != NULL, ("bpf_zerocopy_buffull: zb == NULL"));
372 if ((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0) {
373 zb->zb_flags |= ZBUF_FLAG_ASSIGNED;
374 zb->zb_header->bzh_kernel_len = d->bd_slen;
375 atomic_add_rel_int(&zb->zb_header->bzh_kernel_gen, 1);
380 * Notification from the BPF framework that a buffer has moved into the held
381 * slot on a descriptor. Zero-copy BPF will update the shared page to let
382 * the user process know and flag the buffer as assigned if it hasn't already
383 * been marked assigned due to filling while it was in the store position.
385 * Note: identical logic as in bpf_zerocopy_buffull(), except that we operate
386 * on bd_hbuf and bd_hlen.
389 bpf_zerocopy_bufheld(struct bpf_d *d)
393 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
394 ("bpf_zerocopy_bufheld: not in zbuf mode"));
396 zb = (struct zbuf *)d->bd_hbuf;
397 KASSERT(zb != NULL, ("bpf_zerocopy_bufheld: zb == NULL"));
399 if ((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0) {
400 zb->zb_flags |= ZBUF_FLAG_ASSIGNED;
401 zb->zb_header->bzh_kernel_len = d->bd_hlen;
402 atomic_add_rel_int(&zb->zb_header->bzh_kernel_gen, 1);
407 * Notification from the BPF framework that the free buffer has been been
408 * rotated out of the held position to the free position. This happens when
409 * the user acknowledges the held buffer.
412 bpf_zerocopy_buf_reclaimed(struct bpf_d *d)
416 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
417 ("bpf_zerocopy_reclaim_buf: not in zbuf mode"));
419 KASSERT(d->bd_fbuf != NULL,
420 ("bpf_zerocopy_buf_reclaimed: NULL free buf"));
421 zb = (struct zbuf *)d->bd_fbuf;
422 zb->zb_flags &= ~ZBUF_FLAG_ASSIGNED;
426 * Query from the BPF framework regarding whether the buffer currently in the
427 * held position can be moved to the free position, which can be indicated by
428 * the user process making their generation number equal to the kernel
432 bpf_zerocopy_canfreebuf(struct bpf_d *d)
436 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
437 ("bpf_zerocopy_canfreebuf: not in zbuf mode"));
439 zb = (struct zbuf *)d->bd_hbuf;
442 if (zb->zb_header->bzh_kernel_gen ==
443 atomic_load_acq_int(&zb->zb_header->bzh_user_gen))
449 * Query from the BPF framework as to whether or not the buffer current in
450 * the store position can actually be written to. This may return false if
451 * the store buffer is assigned to userspace before the hold buffer is
455 bpf_zerocopy_canwritebuf(struct bpf_d *d)
459 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
460 ("bpf_zerocopy_canwritebuf: not in zbuf mode"));
462 zb = (struct zbuf *)d->bd_sbuf;
463 KASSERT(zb != NULL, ("bpf_zerocopy_canwritebuf: bd_sbuf NULL"));
465 if (zb->zb_flags & ZBUF_FLAG_ASSIGNED)
471 * Free zero copy buffers at request of descriptor.
474 bpf_zerocopy_free(struct bpf_d *d)
478 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
479 ("bpf_zerocopy_free: not in zbuf mode"));
481 zb = (struct zbuf *)d->bd_sbuf;
484 zb = (struct zbuf *)d->bd_hbuf;
487 zb = (struct zbuf *)d->bd_fbuf;
493 * Ioctl to return the maximum buffer size.
496 bpf_zerocopy_ioctl_getzmax(struct thread *td, struct bpf_d *d, size_t *i)
499 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
500 ("bpf_zerocopy_ioctl_getzmax: not in zbuf mode"));
502 *i = BPF_MAX_PAGES * PAGE_SIZE;
507 * Ioctl to force rotation of the two buffers, if there's any data available.
508 * This can be used by user space to implement timeouts when waiting for a
512 bpf_zerocopy_ioctl_rotzbuf(struct thread *td, struct bpf_d *d,
517 bzero(bz, sizeof(*bz));
519 if (d->bd_hbuf == NULL && d->bd_slen != 0) {
521 bzh = (struct zbuf *)d->bd_hbuf;
522 bz->bz_bufa = (void *)bzh->zb_uaddr;
523 bz->bz_buflen = d->bd_hlen;
530 * Ioctl to configure zero-copy buffers -- may be done only once.
533 bpf_zerocopy_ioctl_setzbuf(struct thread *td, struct bpf_d *d,
536 struct zbuf *zba, *zbb;
539 KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
540 ("bpf_zerocopy_ioctl_setzbuf: not in zbuf mode"));
543 * Must set both buffers. Cannot clear them.
545 if (bz->bz_bufa == NULL || bz->bz_bufb == NULL)
549 * Buffers must have a size greater than 0. Alignment and other size
550 * validity checking is done in zbuf_setup().
552 if (bz->bz_buflen == 0)
556 * Allocate new buffers.
558 error = zbuf_setup(td, (vm_offset_t)bz->bz_bufa, bz->bz_buflen,
562 error = zbuf_setup(td, (vm_offset_t)bz->bz_bufb, bz->bz_buflen,
570 * We only allow buffers to be installed once, so atomically check
571 * that no buffers are currently installed and install new buffers.
574 if (d->bd_hbuf != NULL || d->bd_sbuf != NULL || d->bd_fbuf != NULL ||
583 * Point BPF descriptor at buffers; initialize sbuf as zba so that
584 * it is always filled first in the sequence, per bpf(4).
586 d->bd_fbuf = (caddr_t)zbb;
587 d->bd_sbuf = (caddr_t)zba;
592 * We expose only the space left in the buffer after the size of the
593 * shared management region.
595 d->bd_bufsize = bz->bz_buflen - sizeof(struct bpf_zbuf_header);