1/*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2023 Chelsio Communications, Inc. 5 * Written by: John Baldwin <jhb@FreeBSD.org> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include <sys/param.h> 30#include <sys/mbuf.h> 31#include <sys/memdesc.h> 32#include <sys/systm.h> 33#include <sys/uio.h> 34#include <vm/vm.h> 35#include <vm/pmap.h> 36#include <vm/vm_page.h> 37#include <vm/vm_param.h> 38#include <machine/bus.h> 39 40/* 41 * memdesc_copyback copies data from a source buffer into a buffer 42 * described by a memory descriptor. 43 */ 44static void 45phys_copyback(vm_paddr_t pa, int off, int size, const void *src) 46{ 47 const char *cp; 48 u_int page_off; 49 int todo; 50 void *p; 51 52 KASSERT(PMAP_HAS_DMAP, ("direct-map required")); 53 54 cp = src; 55 pa += off; 56 page_off = pa & PAGE_MASK; 57 while (size > 0) { 58 todo = min(PAGE_SIZE - page_off, size); 59 p = (void *)PHYS_TO_DMAP(pa); 60 memcpy(p, cp, todo); 61 size -= todo; 62 cp += todo; 63 pa += todo; 64 page_off = 0; 65 } 66} 67 68static void 69vlist_copyback(struct bus_dma_segment *vlist, int sglist_cnt, int off, 70 int size, const void *src) 71{ 72 const char *p; 73 int todo; 74 75 while (vlist->ds_len <= off) { 76 KASSERT(sglist_cnt > 1, ("out of sglist entries")); 77 78 off -= vlist->ds_len; 79 vlist++; 80 sglist_cnt--; 81 } 82 83 p = src; 84 while (size > 0) { 85 KASSERT(sglist_cnt >= 1, ("out of sglist entries")); 86 87 todo = size; 88 if (todo > vlist->ds_len - off) 89 todo = vlist->ds_len - off; 90 91 memcpy((char *)(uintptr_t)vlist->ds_addr + off, p, todo); 92 off = 0; 93 vlist++; 94 sglist_cnt--; 95 size -= todo; 96 p += todo; 97 } 98} 99 100static void 101plist_copyback(struct bus_dma_segment *plist, int sglist_cnt, int off, 102 int size, const void *src) 103{ 104 const char *p; 105 int todo; 106 107 while (plist->ds_len <= off) { 108 KASSERT(sglist_cnt > 1, ("out of sglist entries")); 109 110 off -= plist->ds_len; 111 plist++; 112 sglist_cnt--; 113 } 114 115 p = src; 116 while (size > 0) { 117 KASSERT(sglist_cnt >= 1, ("out of sglist entries")); 118 119 todo = size; 120 if (todo > plist->ds_len - off) 121 todo = plist->ds_len - off; 122 123 phys_copyback(plist->ds_addr, off, todo, p); 124 off = 0; 125 plist++; 126 sglist_cnt--; 127 size -= todo; 128 p += todo; 129 } 130} 131 132static void 133vmpages_copyback(vm_page_t *m, int off, int size, const void *src) 134{ 135 struct iovec iov[1]; 136 struct uio uio; 137 int error __diagused; 138 139 iov[0].iov_base = __DECONST(void *, src); 140 iov[0].iov_len = size; 141 uio.uio_iov = iov; 142 uio.uio_iovcnt = 1; 143 uio.uio_offset = 0; 144 uio.uio_resid = size; 145 uio.uio_segflg = UIO_SYSSPACE; 146 uio.uio_rw = UIO_WRITE; 147 error = uiomove_fromphys(m, off, size, &uio); 148 KASSERT(error == 0 && uio.uio_resid == 0, ("copy failed")); 149} 150 151void 152memdesc_copyback(struct memdesc *mem, int off, int size, const void *src) 153{ 154 KASSERT(off >= 0, ("%s: invalid offset %d", __func__, off)); 155 KASSERT(size >= 0, ("%s: invalid size %d", __func__, off)); 156 157 switch (mem->md_type) { 158 case MEMDESC_VADDR: 159 KASSERT(off + size <= mem->md_len, ("copy out of bounds")); 160 memcpy((char *)mem->u.md_vaddr + off, src, size); 161 break; 162 case MEMDESC_PADDR: 163 KASSERT(off + size <= mem->md_len, ("copy out of bounds")); 164 phys_copyback(mem->u.md_paddr, off, size, src); 165 break; 166 case MEMDESC_VLIST: 167 vlist_copyback(mem->u.md_list, mem->md_nseg, off, size, src); 168 break; 169 case MEMDESC_PLIST: 170 plist_copyback(mem->u.md_list, mem->md_nseg, off, size, src); 171 break; 172 case MEMDESC_UIO: 173 panic("Use uiomove instead"); 174 break; 175 case MEMDESC_MBUF: 176 m_copyback(mem->u.md_mbuf, off, size, src); 177 break; 178 case MEMDESC_VMPAGES: 179 KASSERT(off + size <= mem->md_len, ("copy out of bounds")); 180 vmpages_copyback(mem->u.md_ma, mem->md_offset + off, size, 181 src); 182 break; 183 default: 184 __assert_unreachable(); 185 } 186} 187 188/* 189 * memdesc_copydata copies data from a buffer described by a memory 190 * descriptor into a destination buffer. 191 */ 192static void 193phys_copydata(vm_paddr_t pa, int off, int size, void *dst) 194{ 195 char *cp; 196 u_int page_off; 197 int todo; 198 const void *p; 199 200 KASSERT(PMAP_HAS_DMAP, ("direct-map required")); 201 202 cp = dst; 203 pa += off; 204 page_off = pa & PAGE_MASK; 205 while (size > 0) { 206 todo = min(PAGE_SIZE - page_off, size); 207 p = (const void *)PHYS_TO_DMAP(pa); 208 memcpy(cp, p, todo); 209 size -= todo; 210 cp += todo; 211 pa += todo; 212 page_off = 0; 213 } 214} 215 216static void 217vlist_copydata(struct bus_dma_segment *vlist, int sglist_cnt, int off, 218 int size, void *dst) 219{ 220 char *p; 221 int todo; 222 223 while (vlist->ds_len <= off) { 224 KASSERT(sglist_cnt > 1, ("out of sglist entries")); 225 226 off -= vlist->ds_len; 227 vlist++; 228 sglist_cnt--; 229 } 230 231 p = dst; 232 while (size > 0) { 233 KASSERT(sglist_cnt >= 1, ("out of sglist entries")); 234 235 todo = size; 236 if (todo > vlist->ds_len - off) 237 todo = vlist->ds_len - off; 238 239 memcpy(p, (char *)(uintptr_t)vlist->ds_addr + off, todo); 240 off = 0; 241 vlist++; 242 sglist_cnt--; 243 size -= todo; 244 p += todo; 245 } 246} 247 248static void 249plist_copydata(struct bus_dma_segment *plist, int sglist_cnt, int off, 250 int size, void *dst) 251{ 252 char *p; 253 int todo; 254 255 while (plist->ds_len <= off) { 256 KASSERT(sglist_cnt > 1, ("out of sglist entries")); 257 258 off -= plist->ds_len; 259 plist++; 260 sglist_cnt--; 261 } 262 263 p = dst; 264 while (size > 0) { 265 KASSERT(sglist_cnt >= 1, ("out of sglist entries")); 266 267 todo = size; 268 if (todo > plist->ds_len - off) 269 todo = plist->ds_len - off; 270 271 phys_copydata(plist->ds_addr, off, todo, p); 272 off = 0; 273 plist++; 274 sglist_cnt--; 275 size -= todo; 276 p += todo; 277 } 278} 279 280static void 281vmpages_copydata(vm_page_t *m, int off, int size, void *dst) 282{ 283 struct iovec iov[1]; 284 struct uio uio; 285 int error __diagused; 286 287 iov[0].iov_base = dst; 288 iov[0].iov_len = size; 289 uio.uio_iov = iov; 290 uio.uio_iovcnt = 1; 291 uio.uio_offset = 0; 292 uio.uio_resid = size; 293 uio.uio_segflg = UIO_SYSSPACE; 294 uio.uio_rw = UIO_READ; 295 error = uiomove_fromphys(m, off, size, &uio); 296 KASSERT(error == 0 && uio.uio_resid == 0, ("copy failed")); 297} 298 299void 300memdesc_copydata(struct memdesc *mem, int off, int size, void *dst) 301{ 302 KASSERT(off >= 0, ("%s: invalid offset %d", __func__, off)); 303 KASSERT(size >= 0, ("%s: invalid size %d", __func__, off)); 304 305 switch (mem->md_type) { 306 case MEMDESC_VADDR: 307 KASSERT(off + size <= mem->md_len, ("copy out of bounds")); 308 memcpy(dst, (const char *)mem->u.md_vaddr + off, size); 309 break; 310 case MEMDESC_PADDR: 311 KASSERT(off + size <= mem->md_len, ("copy out of bounds")); 312 phys_copydata(mem->u.md_paddr, off, size, dst); 313 break; 314 case MEMDESC_VLIST: 315 vlist_copydata(mem->u.md_list, mem->md_nseg, off, size, dst); 316 break; 317 case MEMDESC_PLIST: 318 plist_copydata(mem->u.md_list, mem->md_nseg, off, size, dst); 319 break; 320 case MEMDESC_UIO: 321 panic("Use uiomove instead"); 322 break; 323 case MEMDESC_MBUF: 324 m_copydata(mem->u.md_mbuf, off, size, dst); 325 break; 326 case MEMDESC_VMPAGES: 327 KASSERT(off + size <= mem->md_len, ("copy out of bounds")); 328 vmpages_copydata(mem->u.md_ma, mem->md_offset + off, size, 329 dst); 330 break; 331 default: 332 __assert_unreachable(); 333 } 334} 335 336/* 337 * memdesc_alloc_ext_mbufs allocates a chain of external mbufs backed 338 * by the storage of a memory descriptor's data buffer. 339 */ 340static struct mbuf * 341vaddr_ext_mbuf(memdesc_alloc_ext_mbuf_t *ext_alloc, void *cb_arg, int how, 342 void *buf, size_t len, size_t *actual_len) 343{ 344 *actual_len = len; 345 return (ext_alloc(cb_arg, how, buf, len)); 346} 347 348static bool 349can_append_paddr(struct mbuf *m, vm_paddr_t pa) 350{ 351 u_int last_len; 352 353 /* Can always append to an empty mbuf. */ 354 if (m->m_epg_npgs == 0) 355 return (true); 356 357 /* Can't append to a full mbuf. */ 358 if (m->m_epg_npgs == MBUF_PEXT_MAX_PGS) 359 return (false); 360 361 /* Can't append a non-page-aligned address to a non-empty mbuf. */ 362 if ((pa & PAGE_MASK) != 0) 363 return (false); 364 365 /* Can't append if the last page is not a full page. */ 366 last_len = m->m_epg_last_len; 367 if (m->m_epg_npgs == 1) 368 last_len += m->m_epg_1st_off; 369 return (last_len == PAGE_SIZE); 370} 371 372/* 373 * Returns amount of data added to an M_EXTPG mbuf. 374 */ 375static size_t 376append_paddr_range(struct mbuf *m, vm_paddr_t pa, size_t len) 377{ 378 size_t appended; 379 380 appended = 0; 381 382 /* Append the first page. */ 383 if (m->m_epg_npgs == 0) { 384 m->m_epg_pa[0] = trunc_page(pa); 385 m->m_epg_npgs = 1; 386 m->m_epg_1st_off = pa & PAGE_MASK; 387 m->m_epg_last_len = PAGE_SIZE - m->m_epg_1st_off; 388 if (m->m_epg_last_len > len) 389 m->m_epg_last_len = len; 390 m->m_len = m->m_epg_last_len; 391 len -= m->m_epg_last_len; 392 pa += m->m_epg_last_len; 393 appended += m->m_epg_last_len; 394 } 395 KASSERT(len == 0 || (pa & PAGE_MASK) == 0, 396 ("PA not aligned before full pages")); 397 398 /* Full pages. */ 399 while (len >= PAGE_SIZE && m->m_epg_npgs < MBUF_PEXT_MAX_PGS) { 400 m->m_epg_pa[m->m_epg_npgs] = pa; 401 m->m_epg_npgs++; 402 m->m_epg_last_len = PAGE_SIZE; 403 m->m_len += PAGE_SIZE; 404 pa += PAGE_SIZE; 405 len -= PAGE_SIZE; 406 appended += PAGE_SIZE; 407 } 408 409 /* Final partial page. */ 410 if (len > 0 && m->m_epg_npgs < MBUF_PEXT_MAX_PGS) { 411 KASSERT(len < PAGE_SIZE, ("final page is full page")); 412 m->m_epg_pa[m->m_epg_npgs] = pa; 413 m->m_epg_npgs++; 414 m->m_epg_last_len = len; 415 m->m_len += len; 416 appended += len; 417 } 418 419 return (appended); 420} 421 422static struct mbuf * 423paddr_ext_mbuf(memdesc_alloc_extpg_mbuf_t *extpg_alloc, void *cb_arg, int how, 424 vm_paddr_t pa, size_t len, size_t *actual_len, bool can_truncate) 425{ 426 struct mbuf *m, *tail; 427 size_t appended; 428 429 if (can_truncate) { 430 vm_paddr_t end; 431 432 /* 433 * Trim any partial page at the end, but not if it's 434 * the only page. 435 */ 436 end = trunc_page(pa + len); 437 if (end > pa) 438 len = end - pa; 439 } 440 *actual_len = len; 441 442 m = tail = extpg_alloc(cb_arg, how); 443 if (m == NULL) 444 return (NULL); 445 while (len > 0) { 446 if (!can_append_paddr(tail, pa)) { 447 MBUF_EXT_PGS_ASSERT_SANITY(tail); 448 tail->m_next = extpg_alloc(cb_arg, how); 449 if (tail->m_next == NULL) 450 goto error; 451 tail = tail->m_next; 452 } 453 454 appended = append_paddr_range(tail, pa, len); 455 KASSERT(appended > 0, ("did not append anything")); 456 KASSERT(appended <= len, ("appended too much")); 457 458 pa += appended; 459 len -= appended; 460 } 461 462 MBUF_EXT_PGS_ASSERT_SANITY(tail); 463 return (m); 464error: 465 m_freem(m); 466 return (NULL); 467} 468 469static struct mbuf * 470vlist_ext_mbuf(memdesc_alloc_ext_mbuf_t *ext_alloc, void *cb_arg, int how, 471 struct bus_dma_segment *vlist, u_int sglist_cnt, size_t offset, 472 size_t len, size_t *actual_len) 473{ 474 struct mbuf *m, *n, *tail; 475 size_t todo; 476 477 *actual_len = len; 478 479 while (vlist->ds_len <= offset) { 480 KASSERT(sglist_cnt > 1, ("out of sglist entries")); 481 482 offset -= vlist->ds_len; 483 vlist++; 484 sglist_cnt--; 485 } 486 487 m = tail = NULL; 488 while (len > 0) { 489 KASSERT(sglist_cnt >= 1, ("out of sglist entries")); 490 491 todo = len; 492 if (todo > vlist->ds_len - offset) 493 todo = vlist->ds_len - offset; 494 495 n = ext_alloc(cb_arg, how, (char *)(uintptr_t)vlist->ds_addr + 496 offset, todo); 497 if (n == NULL) 498 goto error; 499 500 if (m == NULL) { 501 m = n; 502 tail = m; 503 } else { 504 tail->m_next = n; 505 tail = n; 506 } 507 508 offset = 0; 509 vlist++; 510 sglist_cnt--; 511 len -= todo; 512 } 513 514 return (m); 515error: 516 m_freem(m); 517 return (NULL); 518} 519 520static struct mbuf * 521plist_ext_mbuf(memdesc_alloc_extpg_mbuf_t *extpg_alloc, void *cb_arg, int how, 522 struct bus_dma_segment *plist, u_int sglist_cnt, size_t offset, size_t len, 523 size_t *actual_len, bool can_truncate) 524{ 525 vm_paddr_t pa; 526 struct mbuf *m, *tail; 527 size_t appended, totlen, todo; 528 529 while (plist->ds_len <= offset) { 530 KASSERT(sglist_cnt > 1, ("out of sglist entries")); 531 532 offset -= plist->ds_len; 533 plist++; 534 sglist_cnt--; 535 } 536 537 totlen = 0; 538 m = tail = extpg_alloc(cb_arg, how); 539 if (m == NULL) 540 return (NULL); 541 while (len > 0) { 542 KASSERT(sglist_cnt >= 1, ("out of sglist entries")); 543 544 pa = plist->ds_addr + offset; 545 todo = len; 546 if (todo > plist->ds_len - offset) 547 todo = plist->ds_len - offset; 548 549 /* 550 * If truncation is enabled, avoid sending a final 551 * partial page, but only if there is more data 552 * available in the current segment. Also, at least 553 * some data must be sent, so only drop the final page 554 * for this segment if the segment spans multiple 555 * pages or some other data is already queued. 556 */ 557 else if (can_truncate) { 558 vm_paddr_t end; 559 560 end = trunc_page(pa + len); 561 if (end <= pa && totlen != 0) { 562 /* 563 * This last segment is only a partial 564 * page. 565 */ 566 len = 0; 567 break; 568 } 569 todo = end - pa; 570 } 571 572 offset = 0; 573 len -= todo; 574 totlen += todo; 575 576 while (todo > 0) { 577 if (!can_append_paddr(tail, pa)) { 578 MBUF_EXT_PGS_ASSERT_SANITY(tail); 579 tail->m_next = extpg_alloc(cb_arg, how); 580 if (tail->m_next == NULL) 581 goto error; 582 tail = tail->m_next; 583 } 584 585 appended = append_paddr_range(tail, pa, todo); 586 KASSERT(appended > 0, ("did not append anything")); 587 588 pa += appended; 589 todo -= appended; 590 } 591 } 592 593 MBUF_EXT_PGS_ASSERT_SANITY(tail); 594 *actual_len = totlen; 595 return (m); 596error: 597 m_freem(m); 598 return (NULL); 599} 600 601static struct mbuf * 602vmpages_ext_mbuf(memdesc_alloc_extpg_mbuf_t *extpg_alloc, void *cb_arg, int how, 603 vm_page_t *ma, size_t offset, size_t len, size_t *actual_len, 604 bool can_truncate) 605{ 606 struct mbuf *m, *tail; 607 608 while (offset >= PAGE_SIZE) { 609 ma++; 610 offset -= PAGE_SIZE; 611 } 612 613 if (can_truncate) { 614 size_t end; 615 616 /* 617 * Trim any partial page at the end, but not if it's 618 * the only page. 619 */ 620 end = trunc_page(offset + len); 621 if (end > offset) 622 len = end - offset; 623 } 624 *actual_len = len; 625 626 m = tail = extpg_alloc(cb_arg, how); 627 if (m == NULL) 628 return (NULL); 629 630 /* First page. */ 631 m->m_epg_pa[0] = VM_PAGE_TO_PHYS(*ma); 632 ma++; 633 m->m_epg_npgs = 1; 634 m->m_epg_1st_off = offset; 635 m->m_epg_last_len = PAGE_SIZE - offset; 636 if (m->m_epg_last_len > len) 637 m->m_epg_last_len = len; 638 m->m_len = m->m_epg_last_len; 639 len -= m->m_epg_last_len; 640 641 /* Full pages. */ 642 while (len >= PAGE_SIZE) { 643 if (tail->m_epg_npgs == MBUF_PEXT_MAX_PGS) { 644 MBUF_EXT_PGS_ASSERT_SANITY(tail); 645 tail->m_next = extpg_alloc(cb_arg, how); 646 if (tail->m_next == NULL) 647 goto error; 648 tail = tail->m_next; 649 } 650 651 tail->m_epg_pa[tail->m_epg_npgs] = VM_PAGE_TO_PHYS(*ma); 652 ma++; 653 tail->m_epg_npgs++; 654 tail->m_epg_last_len = PAGE_SIZE; 655 tail->m_len += PAGE_SIZE; 656 len -= PAGE_SIZE; 657 } 658 659 /* Last partial page. */ 660 if (len > 0) { 661 if (tail->m_epg_npgs == MBUF_PEXT_MAX_PGS) { 662 MBUF_EXT_PGS_ASSERT_SANITY(tail); 663 tail->m_next = extpg_alloc(cb_arg, how); 664 if (tail->m_next == NULL) 665 goto error; 666 tail = tail->m_next; 667 } 668 669 tail->m_epg_pa[tail->m_epg_npgs] = VM_PAGE_TO_PHYS(*ma); 670 ma++; 671 tail->m_epg_npgs++; 672 tail->m_epg_last_len = len; 673 tail->m_len += len; 674 } 675 676 MBUF_EXT_PGS_ASSERT_SANITY(tail); 677 return (m); 678error: 679 m_freem(m); 680 return (NULL); 681} 682 683/* 684 * Somewhat similar to m_copym but optionally avoids a partial mbuf at 685 * the end. 686 */ 687static struct mbuf * 688mbuf_subchain(struct mbuf *m0, size_t offset, size_t len, 689 size_t *actual_len, bool can_truncate, int how) 690{ 691 struct mbuf *m, *tail; 692 size_t totlen; 693 694 while (offset >= m0->m_len) { 695 offset -= m0->m_len; 696 m0 = m0->m_next; 697 } 698 699 /* Always return at least one mbuf. */ 700 totlen = m0->m_len - offset; 701 if (totlen > len) 702 totlen = len; 703 704 m = m_get(how, MT_DATA); 705 if (m == NULL) 706 return (NULL); 707 m->m_len = totlen; 708 if (m0->m_flags & (M_EXT | M_EXTPG)) { 709 m->m_data = m0->m_data + offset; 710 mb_dupcl(m, m0); 711 } else 712 memcpy(mtod(m, void *), mtodo(m0, offset), m->m_len); 713 714 tail = m; 715 m0 = m0->m_next; 716 len -= totlen; 717 while (len > 0) { 718 /* 719 * If truncation is enabled, don't send any partial 720 * mbufs besides the first one. 721 */ 722 if (can_truncate && m0->m_len > len) 723 break; 724 725 tail->m_next = m_get(how, MT_DATA); 726 if (tail->m_next == NULL) 727 goto error; 728 tail = tail->m_next; 729 tail->m_len = m0->m_len; 730 if (m0->m_flags & (M_EXT | M_EXTPG)) { 731 tail->m_data = m0->m_data; 732 mb_dupcl(tail, m0); 733 } else 734 memcpy(mtod(tail, void *), mtod(m0, void *), 735 tail->m_len); 736 737 totlen += tail->m_len; 738 m0 = m0->m_next; 739 len -= tail->m_len; 740 } 741 *actual_len = totlen; 742 return (m); 743error: 744 m_freem(m); 745 return (NULL); 746} 747 748struct mbuf * 749memdesc_alloc_ext_mbufs(struct memdesc *mem, 750 memdesc_alloc_ext_mbuf_t *ext_alloc, 751 memdesc_alloc_extpg_mbuf_t *extpg_alloc, void *cb_arg, int how, 752 size_t offset, size_t len, size_t *actual_len, bool can_truncate) 753{ 754 struct mbuf *m; 755 size_t done; 756 757 switch (mem->md_type) { 758 case MEMDESC_VADDR: 759 m = vaddr_ext_mbuf(ext_alloc, cb_arg, how, 760 (char *)mem->u.md_vaddr + offset, len, &done); 761 break; 762 case MEMDESC_PADDR: 763 m = paddr_ext_mbuf(extpg_alloc, cb_arg, how, mem->u.md_paddr + 764 offset, len, &done, can_truncate); 765 break; 766 case MEMDESC_VLIST: 767 m = vlist_ext_mbuf(ext_alloc, cb_arg, how, mem->u.md_list, 768 mem->md_nseg, offset, len, &done); 769 break; 770 case MEMDESC_PLIST: 771 m = plist_ext_mbuf(extpg_alloc, cb_arg, how, mem->u.md_list, 772 mem->md_nseg, offset, len, &done, can_truncate); 773 break; 774 case MEMDESC_UIO: 775 panic("uio not supported"); 776 case MEMDESC_MBUF: 777 m = mbuf_subchain(mem->u.md_mbuf, offset, len, &done, 778 can_truncate, how); 779 break; 780 case MEMDESC_VMPAGES: 781 m = vmpages_ext_mbuf(extpg_alloc, cb_arg, how, mem->u.md_ma, 782 mem->md_offset + offset, len, &done, can_truncate); 783 break; 784 default: 785 __assert_unreachable(); 786 } 787 if (m == NULL) 788 return (NULL); 789 790 if (can_truncate) { 791 KASSERT(done <= len, ("chain too long")); 792 } else { 793 KASSERT(done == len, ("short chain with no limit")); 794 } 795 KASSERT(m_length(m, NULL) == done, ("length mismatch")); 796 if (actual_len != NULL) 797 *actual_len = done; 798 return (m); 799} 800