1 /* 2 * Copyright (C) 2009 Matt Fleming <matt@console-pimps.org> 3 * 4 * This file is subject to the terms and conditions of the GNU General Public 5 * License. See the file "COPYING" in the main directory of this archive 6 * for more details. 7 * 8 * This is an implementation of a DWARF unwinder. Its main purpose is 9 * for generating stacktrace information. Based on the DWARF 3 10 * specification from http://www.dwarfstd.org. 11 * 12 * TODO: 13 * - DWARF64 doesn't work. 14 */ 15 16 /* #define DEBUG */ 17 #include <linux/kernel.h> 18 #include <linux/io.h> 19 #include <linux/list.h> 20 #include <linux/mm.h> 21 #include <asm/dwarf.h> 22 #include <asm/unwinder.h> 23 #include <asm/sections.h> 24 #include <asm/unaligned.h> 25 #include <asm/dwarf.h> 26 #include <asm/stacktrace.h> 27 28 static LIST_HEAD(dwarf_cie_list); 29 DEFINE_SPINLOCK(dwarf_cie_lock); 30 31 static LIST_HEAD(dwarf_fde_list); 32 DEFINE_SPINLOCK(dwarf_fde_lock); 33 34 static struct dwarf_cie *cached_cie; 35 36 /* 37 * Figure out whether we need to allocate some dwarf registers. If dwarf 38 * registers have already been allocated then we may need to realloc 39 * them. "reg" is a register number that we need to be able to access 40 * after this call. 41 * 42 * Register numbers start at zero, therefore we need to allocate space 43 * for "reg" + 1 registers. 44 */ 45 static void dwarf_frame_alloc_regs(struct dwarf_frame *frame, 46 unsigned int reg) 47 { 48 struct dwarf_reg *regs; 49 unsigned int num_regs = reg + 1; 50 size_t new_size; 51 size_t old_size; 52 53 new_size = num_regs * sizeof(*regs); 54 old_size = frame->num_regs * sizeof(*regs); 55 56 /* Fast path: don't allocate any regs if we've already got enough. */ 57 if (frame->num_regs >= num_regs) 58 return; 59 60 regs = kzalloc(new_size, GFP_ATOMIC); 61 if (!regs) { 62 printk(KERN_WARNING "Unable to allocate DWARF registers\n"); 63 /* 64 * Let's just bomb hard here, we have no way to 65 * gracefully recover. 66 */ 67 BUG(); 68 } 69 70 if (frame->regs) { 71 memcpy(regs, frame->regs, old_size); 72 kfree(frame->regs); 73 } 74 75 frame->regs = regs; 76 frame->num_regs = num_regs; 77 } 78 79 /** 80 * dwarf_read_addr - read dwarf data 81 * @src: source address of data 82 * @dst: destination address to store the data to 83 * 84 * Read 'n' bytes from @src, where 'n' is the size of an address on 85 * the native machine. We return the number of bytes read, which 86 * should always be 'n'. We also have to be careful when reading 87 * from @src and writing to @dst, because they can be arbitrarily 88 * aligned. Return 'n' - the number of bytes read. 89 */ 90 static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst) 91 { 92 u32 val = get_unaligned(src); 93 put_unaligned(val, dst); 94 return sizeof(unsigned long *); 95 } 96 97 /** 98 * dwarf_read_uleb128 - read unsigned LEB128 data 99 * @addr: the address where the ULEB128 data is stored 100 * @ret: address to store the result 101 * 102 * Decode an unsigned LEB128 encoded datum. The algorithm is taken 103 * from Appendix C of the DWARF 3 spec. For information on the 104 * encodings refer to section "7.6 - Variable Length Data". Return 105 * the number of bytes read. 106 */ 107 static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret) 108 { 109 unsigned int result; 110 unsigned char byte; 111 int shift, count; 112 113 result = 0; 114 shift = 0; 115 count = 0; 116 117 while (1) { 118 byte = __raw_readb(addr); 119 addr++; 120 count++; 121 122 result |= (byte & 0x7f) << shift; 123 shift += 7; 124 125 if (!(byte & 0x80)) 126 break; 127 } 128 129 *ret = result; 130 131 return count; 132 } 133 134 /** 135 * dwarf_read_leb128 - read signed LEB128 data 136 * @addr: the address of the LEB128 encoded data 137 * @ret: address to store the result 138 * 139 * Decode signed LEB128 data. The algorithm is taken from Appendix 140 * C of the DWARF 3 spec. Return the number of bytes read. 141 */ 142 static inline unsigned long dwarf_read_leb128(char *addr, int *ret) 143 { 144 unsigned char byte; 145 int result, shift; 146 int num_bits; 147 int count; 148 149 result = 0; 150 shift = 0; 151 count = 0; 152 153 while (1) { 154 byte = __raw_readb(addr); 155 addr++; 156 result |= (byte & 0x7f) << shift; 157 shift += 7; 158 count++; 159 160 if (!(byte & 0x80)) 161 break; 162 } 163 164 /* The number of bits in a signed integer. */ 165 num_bits = 8 * sizeof(result); 166 167 if ((shift < num_bits) && (byte & 0x40)) 168 result |= (-1 << shift); 169 170 *ret = result; 171 172 return count; 173 } 174 175 /** 176 * dwarf_read_encoded_value - return the decoded value at @addr 177 * @addr: the address of the encoded value 178 * @val: where to write the decoded value 179 * @encoding: the encoding with which we can decode @addr 180 * 181 * GCC emits encoded address in the .eh_frame FDE entries. Decode 182 * the value at @addr using @encoding. The decoded value is written 183 * to @val and the number of bytes read is returned. 184 */ 185 static int dwarf_read_encoded_value(char *addr, unsigned long *val, 186 char encoding) 187 { 188 unsigned long decoded_addr = 0; 189 int count = 0; 190 191 switch (encoding & 0x70) { 192 case DW_EH_PE_absptr: 193 break; 194 case DW_EH_PE_pcrel: 195 decoded_addr = (unsigned long)addr; 196 break; 197 default: 198 pr_debug("encoding=0x%x\n", (encoding & 0x70)); 199 BUG(); 200 } 201 202 if ((encoding & 0x07) == 0x00) 203 encoding |= DW_EH_PE_udata4; 204 205 switch (encoding & 0x0f) { 206 case DW_EH_PE_sdata4: 207 case DW_EH_PE_udata4: 208 count += 4; 209 decoded_addr += get_unaligned((u32 *)addr); 210 __raw_writel(decoded_addr, val); 211 break; 212 default: 213 pr_debug("encoding=0x%x\n", encoding); 214 BUG(); 215 } 216 217 return count; 218 } 219 220 /** 221 * dwarf_entry_len - return the length of an FDE or CIE 222 * @addr: the address of the entry 223 * @len: the length of the entry 224 * 225 * Read the initial_length field of the entry and store the size of 226 * the entry in @len. We return the number of bytes read. Return a 227 * count of 0 on error. 228 */ 229 static inline int dwarf_entry_len(char *addr, unsigned long *len) 230 { 231 u32 initial_len; 232 int count; 233 234 initial_len = get_unaligned((u32 *)addr); 235 count = 4; 236 237 /* 238 * An initial length field value in the range DW_LEN_EXT_LO - 239 * DW_LEN_EXT_HI indicates an extension, and should not be 240 * interpreted as a length. The only extension that we currently 241 * understand is the use of DWARF64 addresses. 242 */ 243 if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) { 244 /* 245 * The 64-bit length field immediately follows the 246 * compulsory 32-bit length field. 247 */ 248 if (initial_len == DW_EXT_DWARF64) { 249 *len = get_unaligned((u64 *)addr + 4); 250 count = 12; 251 } else { 252 printk(KERN_WARNING "Unknown DWARF extension\n"); 253 count = 0; 254 } 255 } else 256 *len = initial_len; 257 258 return count; 259 } 260 261 /** 262 * dwarf_lookup_cie - locate the cie 263 * @cie_ptr: pointer to help with lookup 264 */ 265 static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr) 266 { 267 struct dwarf_cie *cie, *n; 268 unsigned long flags; 269 270 spin_lock_irqsave(&dwarf_cie_lock, flags); 271 272 /* 273 * We've cached the last CIE we looked up because chances are 274 * that the FDE wants this CIE. 275 */ 276 if (cached_cie && cached_cie->cie_pointer == cie_ptr) { 277 cie = cached_cie; 278 goto out; 279 } 280 281 list_for_each_entry_safe(cie, n, &dwarf_cie_list, link) { 282 if (cie->cie_pointer == cie_ptr) { 283 cached_cie = cie; 284 break; 285 } 286 } 287 288 /* Couldn't find the entry in the list. */ 289 if (&cie->link == &dwarf_cie_list) 290 cie = NULL; 291 out: 292 spin_unlock_irqrestore(&dwarf_cie_lock, flags); 293 return cie; 294 } 295 296 /** 297 * dwarf_lookup_fde - locate the FDE that covers pc 298 * @pc: the program counter 299 */ 300 struct dwarf_fde *dwarf_lookup_fde(unsigned long pc) 301 { 302 unsigned long flags; 303 struct dwarf_fde *fde, *n; 304 305 spin_lock_irqsave(&dwarf_fde_lock, flags); 306 list_for_each_entry_safe(fde, n, &dwarf_fde_list, link) { 307 unsigned long start, end; 308 309 start = fde->initial_location; 310 end = fde->initial_location + fde->address_range; 311 312 if (pc >= start && pc < end) 313 break; 314 } 315 316 /* Couldn't find the entry in the list. */ 317 if (&fde->link == &dwarf_fde_list) 318 fde = NULL; 319 320 spin_unlock_irqrestore(&dwarf_fde_lock, flags); 321 322 return fde; 323 } 324 325 /** 326 * dwarf_cfa_execute_insns - execute instructions to calculate a CFA 327 * @insn_start: address of the first instruction 328 * @insn_end: address of the last instruction 329 * @cie: the CIE for this function 330 * @fde: the FDE for this function 331 * @frame: the instructions calculate the CFA for this frame 332 * @pc: the program counter of the address we're interested in 333 * @define_ra: keep executing insns until the return addr reg is defined? 334 * 335 * Execute the Call Frame instruction sequence starting at 336 * @insn_start and ending at @insn_end. The instructions describe 337 * how to calculate the Canonical Frame Address of a stackframe. 338 * Store the results in @frame. 339 */ 340 static int dwarf_cfa_execute_insns(unsigned char *insn_start, 341 unsigned char *insn_end, 342 struct dwarf_cie *cie, 343 struct dwarf_fde *fde, 344 struct dwarf_frame *frame, 345 unsigned long pc, 346 bool define_ra) 347 { 348 unsigned char insn; 349 unsigned char *current_insn; 350 unsigned int count, delta, reg, expr_len, offset; 351 bool seen_ra_reg; 352 353 current_insn = insn_start; 354 355 /* 356 * If we're executing instructions for the dwarf_unwind_stack() 357 * FDE we need to keep executing instructions until the value of 358 * DWARF_ARCH_RA_REG is defined. See the comment in 359 * dwarf_unwind_stack() for more details. 360 */ 361 if (define_ra) 362 seen_ra_reg = false; 363 else 364 seen_ra_reg = true; 365 366 while (current_insn < insn_end && (frame->pc <= pc || !seen_ra_reg) ) { 367 insn = __raw_readb(current_insn++); 368 369 if (!seen_ra_reg) { 370 if (frame->num_regs >= DWARF_ARCH_RA_REG && 371 frame->regs[DWARF_ARCH_RA_REG].flags) 372 seen_ra_reg = true; 373 } 374 375 /* 376 * Firstly, handle the opcodes that embed their operands 377 * in the instructions. 378 */ 379 switch (DW_CFA_opcode(insn)) { 380 case DW_CFA_advance_loc: 381 delta = DW_CFA_operand(insn); 382 delta *= cie->code_alignment_factor; 383 frame->pc += delta; 384 continue; 385 /* NOTREACHED */ 386 case DW_CFA_offset: 387 reg = DW_CFA_operand(insn); 388 count = dwarf_read_uleb128(current_insn, &offset); 389 current_insn += count; 390 offset *= cie->data_alignment_factor; 391 dwarf_frame_alloc_regs(frame, reg); 392 frame->regs[reg].addr = offset; 393 frame->regs[reg].flags |= DWARF_REG_OFFSET; 394 continue; 395 /* NOTREACHED */ 396 case DW_CFA_restore: 397 reg = DW_CFA_operand(insn); 398 continue; 399 /* NOTREACHED */ 400 } 401 402 /* 403 * Secondly, handle the opcodes that don't embed their 404 * operands in the instruction. 405 */ 406 switch (insn) { 407 case DW_CFA_nop: 408 continue; 409 case DW_CFA_advance_loc1: 410 delta = *current_insn++; 411 frame->pc += delta * cie->code_alignment_factor; 412 break; 413 case DW_CFA_advance_loc2: 414 delta = get_unaligned((u16 *)current_insn); 415 current_insn += 2; 416 frame->pc += delta * cie->code_alignment_factor; 417 break; 418 case DW_CFA_advance_loc4: 419 delta = get_unaligned((u32 *)current_insn); 420 current_insn += 4; 421 frame->pc += delta * cie->code_alignment_factor; 422 break; 423 case DW_CFA_offset_extended: 424 count = dwarf_read_uleb128(current_insn, ®); 425 current_insn += count; 426 count = dwarf_read_uleb128(current_insn, &offset); 427 current_insn += count; 428 offset *= cie->data_alignment_factor; 429 break; 430 case DW_CFA_restore_extended: 431 count = dwarf_read_uleb128(current_insn, ®); 432 current_insn += count; 433 break; 434 case DW_CFA_undefined: 435 count = dwarf_read_uleb128(current_insn, ®); 436 current_insn += count; 437 break; 438 case DW_CFA_def_cfa: 439 count = dwarf_read_uleb128(current_insn, 440 &frame->cfa_register); 441 current_insn += count; 442 count = dwarf_read_uleb128(current_insn, 443 &frame->cfa_offset); 444 current_insn += count; 445 446 frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; 447 break; 448 case DW_CFA_def_cfa_register: 449 count = dwarf_read_uleb128(current_insn, 450 &frame->cfa_register); 451 current_insn += count; 452 frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; 453 break; 454 case DW_CFA_def_cfa_offset: 455 count = dwarf_read_uleb128(current_insn, &offset); 456 current_insn += count; 457 frame->cfa_offset = offset; 458 break; 459 case DW_CFA_def_cfa_expression: 460 count = dwarf_read_uleb128(current_insn, &expr_len); 461 current_insn += count; 462 463 frame->cfa_expr = current_insn; 464 frame->cfa_expr_len = expr_len; 465 current_insn += expr_len; 466 467 frame->flags |= DWARF_FRAME_CFA_REG_EXP; 468 break; 469 case DW_CFA_offset_extended_sf: 470 count = dwarf_read_uleb128(current_insn, ®); 471 current_insn += count; 472 count = dwarf_read_leb128(current_insn, &offset); 473 current_insn += count; 474 offset *= cie->data_alignment_factor; 475 dwarf_frame_alloc_regs(frame, reg); 476 frame->regs[reg].flags |= DWARF_REG_OFFSET; 477 frame->regs[reg].addr = offset; 478 break; 479 case DW_CFA_val_offset: 480 count = dwarf_read_uleb128(current_insn, ®); 481 current_insn += count; 482 count = dwarf_read_leb128(current_insn, &offset); 483 offset *= cie->data_alignment_factor; 484 frame->regs[reg].flags |= DWARF_REG_OFFSET; 485 frame->regs[reg].addr = offset; 486 break; 487 default: 488 pr_debug("unhandled DWARF instruction 0x%x\n", insn); 489 break; 490 } 491 } 492 493 return 0; 494 } 495 496 /** 497 * dwarf_unwind_stack - recursively unwind the stack 498 * @pc: address of the function to unwind 499 * @prev: struct dwarf_frame of the previous stackframe on the callstack 500 * 501 * Return a struct dwarf_frame representing the most recent frame 502 * on the callstack. Each of the lower (older) stack frames are 503 * linked via the "prev" member. 504 */ 505 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc, 506 struct dwarf_frame *prev) 507 { 508 struct dwarf_frame *frame; 509 struct dwarf_cie *cie; 510 struct dwarf_fde *fde; 511 unsigned long addr; 512 int i, offset; 513 bool define_ra = false; 514 515 /* 516 * If this is the first invocation of this recursive function we 517 * need get the contents of a physical register to get the CFA 518 * in order to begin the virtual unwinding of the stack. 519 * 520 * Setting "define_ra" to true indictates that we want 521 * dwarf_cfa_execute_insns() to continue executing instructions 522 * until we know how to calculate the value of DWARF_ARCH_RA_REG 523 * (which we need in order to kick off the whole unwinding 524 * process). 525 * 526 * NOTE: the return address is guaranteed to be setup by the 527 * time this function makes its first function call. 528 */ 529 if (!pc && !prev) { 530 pc = (unsigned long)&dwarf_unwind_stack; 531 define_ra = true; 532 } 533 534 frame = kzalloc(sizeof(*frame), GFP_ATOMIC); 535 if (!frame) 536 return NULL; 537 538 frame->prev = prev; 539 540 fde = dwarf_lookup_fde(pc); 541 if (!fde) { 542 /* 543 * This is our normal exit path - the one that stops the 544 * recursion. There's two reasons why we might exit 545 * here, 546 * 547 * a) pc has no asscociated DWARF frame info and so 548 * we don't know how to unwind this frame. This is 549 * usually the case when we're trying to unwind a 550 * frame that was called from some assembly code 551 * that has no DWARF info, e.g. syscalls. 552 * 553 * b) the DEBUG info for pc is bogus. There's 554 * really no way to distinguish this case from the 555 * case above, which sucks because we could print a 556 * warning here. 557 */ 558 return NULL; 559 } 560 561 cie = dwarf_lookup_cie(fde->cie_pointer); 562 563 frame->pc = fde->initial_location; 564 565 /* CIE initial instructions */ 566 dwarf_cfa_execute_insns(cie->initial_instructions, 567 cie->instructions_end, cie, fde, 568 frame, pc, false); 569 570 /* FDE instructions */ 571 dwarf_cfa_execute_insns(fde->instructions, fde->end, cie, 572 fde, frame, pc, define_ra); 573 574 /* Calculate the CFA */ 575 switch (frame->flags) { 576 case DWARF_FRAME_CFA_REG_OFFSET: 577 if (prev) { 578 BUG_ON(!prev->regs[frame->cfa_register].flags); 579 580 addr = prev->cfa; 581 addr += prev->regs[frame->cfa_register].addr; 582 frame->cfa = __raw_readl(addr); 583 584 } else { 585 /* 586 * Again, this is the first invocation of this 587 * recurisve function. We need to physically 588 * read the contents of a register in order to 589 * get the Canonical Frame Address for this 590 * function. 591 */ 592 frame->cfa = dwarf_read_arch_reg(frame->cfa_register); 593 } 594 595 frame->cfa += frame->cfa_offset; 596 break; 597 default: 598 BUG(); 599 } 600 601 /* If we haven't seen the return address reg, we're screwed. */ 602 BUG_ON(!frame->regs[DWARF_ARCH_RA_REG].flags); 603 604 for (i = 0; i <= frame->num_regs; i++) { 605 struct dwarf_reg *reg = &frame->regs[i]; 606 607 if (!reg->flags) 608 continue; 609 610 offset = reg->addr; 611 offset += frame->cfa; 612 } 613 614 addr = frame->cfa + frame->regs[DWARF_ARCH_RA_REG].addr; 615 frame->return_addr = __raw_readl(addr); 616 617 frame->next = dwarf_unwind_stack(frame->return_addr, frame); 618 return frame; 619 } 620 621 static int dwarf_parse_cie(void *entry, void *p, unsigned long len, 622 unsigned char *end) 623 { 624 struct dwarf_cie *cie; 625 unsigned long flags; 626 int count; 627 628 cie = kzalloc(sizeof(*cie), GFP_KERNEL); 629 if (!cie) 630 return -ENOMEM; 631 632 cie->length = len; 633 634 /* 635 * Record the offset into the .eh_frame section 636 * for this CIE. It allows this CIE to be 637 * quickly and easily looked up from the 638 * corresponding FDE. 639 */ 640 cie->cie_pointer = (unsigned long)entry; 641 642 cie->version = *(char *)p++; 643 BUG_ON(cie->version != 1); 644 645 cie->augmentation = p; 646 p += strlen(cie->augmentation) + 1; 647 648 count = dwarf_read_uleb128(p, &cie->code_alignment_factor); 649 p += count; 650 651 count = dwarf_read_leb128(p, &cie->data_alignment_factor); 652 p += count; 653 654 /* 655 * Which column in the rule table contains the 656 * return address? 657 */ 658 if (cie->version == 1) { 659 cie->return_address_reg = __raw_readb(p); 660 p++; 661 } else { 662 count = dwarf_read_uleb128(p, &cie->return_address_reg); 663 p += count; 664 } 665 666 if (cie->augmentation[0] == 'z') { 667 unsigned int length, count; 668 cie->flags |= DWARF_CIE_Z_AUGMENTATION; 669 670 count = dwarf_read_uleb128(p, &length); 671 p += count; 672 673 BUG_ON((unsigned char *)p > end); 674 675 cie->initial_instructions = p + length; 676 cie->augmentation++; 677 } 678 679 while (*cie->augmentation) { 680 /* 681 * "L" indicates a byte showing how the 682 * LSDA pointer is encoded. Skip it. 683 */ 684 if (*cie->augmentation == 'L') { 685 p++; 686 cie->augmentation++; 687 } else if (*cie->augmentation == 'R') { 688 /* 689 * "R" indicates a byte showing 690 * how FDE addresses are 691 * encoded. 692 */ 693 cie->encoding = *(char *)p++; 694 cie->augmentation++; 695 } else if (*cie->augmentation == 'P') { 696 /* 697 * "R" indicates a personality 698 * routine in the CIE 699 * augmentation. 700 */ 701 BUG(); 702 } else if (*cie->augmentation == 'S') { 703 BUG(); 704 } else { 705 /* 706 * Unknown augmentation. Assume 707 * 'z' augmentation. 708 */ 709 p = cie->initial_instructions; 710 BUG_ON(!p); 711 break; 712 } 713 } 714 715 cie->initial_instructions = p; 716 cie->instructions_end = end; 717 718 /* Add to list */ 719 spin_lock_irqsave(&dwarf_cie_lock, flags); 720 list_add_tail(&cie->link, &dwarf_cie_list); 721 spin_unlock_irqrestore(&dwarf_cie_lock, flags); 722 723 return 0; 724 } 725 726 static int dwarf_parse_fde(void *entry, u32 entry_type, 727 void *start, unsigned long len) 728 { 729 struct dwarf_fde *fde; 730 struct dwarf_cie *cie; 731 unsigned long flags; 732 int count; 733 void *p = start; 734 735 fde = kzalloc(sizeof(*fde), GFP_KERNEL); 736 if (!fde) 737 return -ENOMEM; 738 739 fde->length = len; 740 741 /* 742 * In a .eh_frame section the CIE pointer is the 743 * delta between the address within the FDE 744 */ 745 fde->cie_pointer = (unsigned long)(p - entry_type - 4); 746 747 cie = dwarf_lookup_cie(fde->cie_pointer); 748 fde->cie = cie; 749 750 if (cie->encoding) 751 count = dwarf_read_encoded_value(p, &fde->initial_location, 752 cie->encoding); 753 else 754 count = dwarf_read_addr(p, &fde->initial_location); 755 756 p += count; 757 758 if (cie->encoding) 759 count = dwarf_read_encoded_value(p, &fde->address_range, 760 cie->encoding & 0x0f); 761 else 762 count = dwarf_read_addr(p, &fde->address_range); 763 764 p += count; 765 766 if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) { 767 unsigned int length; 768 count = dwarf_read_uleb128(p, &length); 769 p += count + length; 770 } 771 772 /* Call frame instructions. */ 773 fde->instructions = p; 774 fde->end = start + len; 775 776 /* Add to list. */ 777 spin_lock_irqsave(&dwarf_fde_lock, flags); 778 list_add_tail(&fde->link, &dwarf_fde_list); 779 spin_unlock_irqrestore(&dwarf_fde_lock, flags); 780 781 return 0; 782 } 783 784 static void dwarf_unwinder_dump(struct task_struct *task, struct pt_regs *regs, 785 unsigned long *sp, 786 const struct stacktrace_ops *ops, void *data) 787 { 788 struct dwarf_frame *frame; 789 790 frame = dwarf_unwind_stack(0, NULL); 791 792 while (frame && frame->return_addr) { 793 ops->address(data, frame->return_addr, 1); 794 frame = frame->next; 795 } 796 } 797 798 static struct unwinder dwarf_unwinder = { 799 .name = "dwarf-unwinder", 800 .dump = dwarf_unwinder_dump, 801 .rating = 150, 802 }; 803 804 static void dwarf_unwinder_cleanup(void) 805 { 806 struct dwarf_cie *cie, *m; 807 struct dwarf_fde *fde, *n; 808 unsigned long flags; 809 810 /* 811 * Deallocate all the memory allocated for the DWARF unwinder. 812 * Traverse all the FDE/CIE lists and remove and free all the 813 * memory associated with those data structures. 814 */ 815 spin_lock_irqsave(&dwarf_cie_lock, flags); 816 list_for_each_entry_safe(cie, m, &dwarf_cie_list, link) 817 kfree(cie); 818 spin_unlock_irqrestore(&dwarf_cie_lock, flags); 819 820 spin_lock_irqsave(&dwarf_fde_lock, flags); 821 list_for_each_entry_safe(fde, n, &dwarf_fde_list, link) 822 kfree(fde); 823 spin_unlock_irqrestore(&dwarf_fde_lock, flags); 824 } 825 826 /** 827 * dwarf_unwinder_init - initialise the dwarf unwinder 828 * 829 * Build the data structures describing the .dwarf_frame section to 830 * make it easier to lookup CIE and FDE entries. Because the 831 * .eh_frame section is packed as tightly as possible it is not 832 * easy to lookup the FDE for a given PC, so we build a list of FDE 833 * and CIE entries that make it easier. 834 */ 835 void dwarf_unwinder_init(void) 836 { 837 u32 entry_type; 838 void *p, *entry; 839 int count, err; 840 unsigned long len; 841 unsigned int c_entries, f_entries; 842 unsigned char *end; 843 INIT_LIST_HEAD(&dwarf_cie_list); 844 INIT_LIST_HEAD(&dwarf_fde_list); 845 846 c_entries = 0; 847 f_entries = 0; 848 entry = &__start_eh_frame; 849 850 while ((char *)entry < __stop_eh_frame) { 851 p = entry; 852 853 count = dwarf_entry_len(p, &len); 854 if (count == 0) { 855 /* 856 * We read a bogus length field value. There is 857 * nothing we can do here apart from disabling 858 * the DWARF unwinder. We can't even skip this 859 * entry and move to the next one because 'len' 860 * tells us where our next entry is. 861 */ 862 goto out; 863 } else 864 p += count; 865 866 /* initial length does not include itself */ 867 end = p + len; 868 869 entry_type = get_unaligned((u32 *)p); 870 p += 4; 871 872 if (entry_type == DW_EH_FRAME_CIE) { 873 err = dwarf_parse_cie(entry, p, len, end); 874 if (err < 0) 875 goto out; 876 else 877 c_entries++; 878 } else { 879 err = dwarf_parse_fde(entry, entry_type, p, len); 880 if (err < 0) 881 goto out; 882 else 883 f_entries++; 884 } 885 886 entry = (char *)entry + len + 4; 887 } 888 889 printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n", 890 c_entries, f_entries); 891 892 err = unwinder_register(&dwarf_unwinder); 893 if (err) 894 goto out; 895 896 return; 897 898 out: 899 printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err); 900 dwarf_unwinder_cleanup(); 901 } 902