Pileus Git - ~andy/linux/blob - arch/sh/kernel/dwarf.c

   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, &reg);
 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, &reg);
 432                         current_insn += count;
 433                         break;
 434                 case DW_CFA_undefined:
 435                         count = dwarf_read_uleb128(current_insn, &reg);
 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->cfa_offset = 0;
 453                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
 454                         break;
 455                 case DW_CFA_def_cfa_offset:
 456                         count = dwarf_read_uleb128(current_insn, &offset);
 457                         current_insn += count;
 458                         frame->cfa_offset = offset;
 459                         break;
 460                 case DW_CFA_def_cfa_expression:
 461                         count = dwarf_read_uleb128(current_insn, &expr_len);
 462                         current_insn += count;
 463
 464                         frame->cfa_expr = current_insn;
 465                         frame->cfa_expr_len = expr_len;
 466                         current_insn += expr_len;
 467
 468                         frame->flags |= DWARF_FRAME_CFA_REG_EXP;
 469                         break;
 470                 case DW_CFA_offset_extended_sf:
 471                         count = dwarf_read_uleb128(current_insn, &reg);
 472                         current_insn += count;
 473                         count = dwarf_read_leb128(current_insn, &offset);
 474                         current_insn += count;
 475                         offset *= cie->data_alignment_factor;
 476                         dwarf_frame_alloc_regs(frame, reg);
 477                         frame->regs[reg].flags |= DWARF_REG_OFFSET;
 478                         frame->regs[reg].addr = offset;
 479                         break;
 480                 case DW_CFA_val_offset:
 481                         count = dwarf_read_uleb128(current_insn, &reg);
 482                         current_insn += count;
 483                         count = dwarf_read_leb128(current_insn, &offset);
 484                         offset *= cie->data_alignment_factor;
 485                         frame->regs[reg].flags |= DWARF_REG_OFFSET;
 486                         frame->regs[reg].addr = offset;
 487                         break;
 488                 default:
 489                         pr_debug("unhandled DWARF instruction 0x%x\n", insn);
 490                         break;
 491                 }
 492         }
 493
 494         return 0;
 495 }
 496
 497 /**
 498  *      dwarf_unwind_stack - recursively unwind the stack
 499  *      @pc: address of the function to unwind
 500  *      @prev: struct dwarf_frame of the previous stackframe on the callstack
 501  *
 502  *      Return a struct dwarf_frame representing the most recent frame
 503  *      on the callstack. Each of the lower (older) stack frames are
 504  *      linked via the "prev" member.
 505  */
 506 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
 507                                        struct dwarf_frame *prev)
 508 {
 509         struct dwarf_frame *frame;
 510         struct dwarf_cie *cie;
 511         struct dwarf_fde *fde;
 512         unsigned long addr;
 513         int i, offset;
 514         bool define_ra = false;
 515
 516         /*
 517          * If this is the first invocation of this recursive function we
 518          * need get the contents of a physical register to get the CFA
 519          * in order to begin the virtual unwinding of the stack.
 520          *
 521          * Setting "define_ra" to true indictates that we want
 522          * dwarf_cfa_execute_insns() to continue executing instructions
 523          * until we know how to calculate the value of DWARF_ARCH_RA_REG
 524          * (which we need in order to kick off the whole unwinding
 525          * process).
 526          *
 527          * NOTE: the return address is guaranteed to be setup by the
 528          * time this function makes its first function call.
 529          */
 530         if (!pc && !prev) {
 531                 pc = (unsigned long)&dwarf_unwind_stack;
 532                 define_ra = true;
 533         }
 534
 535         frame = kzalloc(sizeof(*frame), GFP_ATOMIC);
 536         if (!frame)
 537                 return NULL;
 538
 539         frame->prev = prev;
 540
 541         fde = dwarf_lookup_fde(pc);
 542         if (!fde) {
 543                 /*
 544                  * This is our normal exit path - the one that stops the
 545                  * recursion. There's two reasons why we might exit
 546                  * here,
 547                  *
 548                  *      a) pc has no asscociated DWARF frame info and so
 549                  *      we don't know how to unwind this frame. This is
 550                  *      usually the case when we're trying to unwind a
 551                  *      frame that was called from some assembly code
 552                  *      that has no DWARF info, e.g. syscalls.
 553                  *
 554                  *      b) the DEBUG info for pc is bogus. There's
 555                  *      really no way to distinguish this case from the
 556                  *      case above, which sucks because we could print a
 557                  *      warning here.
 558                  */
 559                 return NULL;
 560         }
 561
 562         cie = dwarf_lookup_cie(fde->cie_pointer);
 563
 564         frame->pc = fde->initial_location;
 565
 566         /* CIE initial instructions */
 567         dwarf_cfa_execute_insns(cie->initial_instructions,
 568                                 cie->instructions_end, cie, fde,
 569                                 frame, pc, false);
 570
 571         /* FDE instructions */
 572         dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
 573                                 fde, frame, pc, define_ra);
 574
 575         /* Calculate the CFA */
 576         switch (frame->flags) {
 577         case DWARF_FRAME_CFA_REG_OFFSET:
 578                 if (prev) {
 579                         BUG_ON(!prev->regs[frame->cfa_register].flags);
 580
 581                         addr = prev->cfa;
 582                         addr += prev->regs[frame->cfa_register].addr;
 583                         frame->cfa = __raw_readl(addr);
 584
 585                 } else {
 586                         /*
 587                          * Again, this is the first invocation of this
 588                          * recurisve function. We need to physically
 589                          * read the contents of a register in order to
 590                          * get the Canonical Frame Address for this
 591                          * function.
 592                          */
 593                         frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
 594                 }
 595
 596                 frame->cfa += frame->cfa_offset;
 597                 break;
 598         default:
 599                 BUG();
 600         }
 601
 602         /* If we haven't seen the return address reg, we're screwed. */
 603         BUG_ON(!frame->regs[DWARF_ARCH_RA_REG].flags);
 604
 605         for (i = 0; i <= frame->num_regs; i++) {
 606                 struct dwarf_reg *reg = &frame->regs[i];
 607
 608                 if (!reg->flags)
 609                         continue;
 610
 611                 offset = reg->addr;
 612                 offset += frame->cfa;
 613         }
 614
 615         addr = frame->cfa + frame->regs[DWARF_ARCH_RA_REG].addr;
 616         frame->return_addr = __raw_readl(addr);
 617
 618         frame->next = dwarf_unwind_stack(frame->return_addr, frame);
 619         return frame;
 620 }
 621
 622 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
 623                            unsigned char *end)
 624 {
 625         struct dwarf_cie *cie;
 626         unsigned long flags;
 627         int count;
 628
 629         cie = kzalloc(sizeof(*cie), GFP_KERNEL);
 630         if (!cie)
 631                 return -ENOMEM;
 632
 633         cie->length = len;
 634
 635         /*
 636          * Record the offset into the .eh_frame section
 637          * for this CIE. It allows this CIE to be
 638          * quickly and easily looked up from the
 639          * corresponding FDE.
 640          */
 641         cie->cie_pointer = (unsigned long)entry;
 642
 643         cie->version = *(char *)p++;
 644         BUG_ON(cie->version != 1);
 645
 646         cie->augmentation = p;
 647         p += strlen(cie->augmentation) + 1;
 648
 649         count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
 650         p += count;
 651
 652         count = dwarf_read_leb128(p, &cie->data_alignment_factor);
 653         p += count;
 654
 655         /*
 656          * Which column in the rule table contains the
 657          * return address?
 658          */
 659         if (cie->version == 1) {
 660                 cie->return_address_reg = __raw_readb(p);
 661                 p++;
 662         } else {
 663                 count = dwarf_read_uleb128(p, &cie->return_address_reg);
 664                 p += count;
 665         }
 666
 667         if (cie->augmentation[0] == 'z') {
 668                 unsigned int length, count;
 669                 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
 670
 671                 count = dwarf_read_uleb128(p, &length);
 672                 p += count;
 673
 674                 BUG_ON((unsigned char *)p > end);
 675
 676                 cie->initial_instructions = p + length;
 677                 cie->augmentation++;
 678         }
 679
 680         while (*cie->augmentation) {
 681                 /*
 682                  * "L" indicates a byte showing how the
 683                  * LSDA pointer is encoded. Skip it.
 684                  */
 685                 if (*cie->augmentation == 'L') {
 686                         p++;
 687                         cie->augmentation++;
 688                 } else if (*cie->augmentation == 'R') {
 689                         /*
 690                          * "R" indicates a byte showing
 691                          * how FDE addresses are
 692                          * encoded.
 693                          */
 694                         cie->encoding = *(char *)p++;
 695                         cie->augmentation++;
 696                 } else if (*cie->augmentation == 'P') {
 697                         /*
 698                          * "R" indicates a personality
 699                          * routine in the CIE
 700                          * augmentation.
 701                          */
 702                         BUG();
 703                 } else if (*cie->augmentation == 'S') {
 704                         BUG();
 705                 } else {
 706                         /*
 707                          * Unknown augmentation. Assume
 708                          * 'z' augmentation.
 709                          */
 710                         p = cie->initial_instructions;
 711                         BUG_ON(!p);
 712                         break;
 713                 }
 714         }
 715
 716         cie->initial_instructions = p;
 717         cie->instructions_end = end;
 718
 719         /* Add to list */
 720         spin_lock_irqsave(&dwarf_cie_lock, flags);
 721         list_add_tail(&cie->link, &dwarf_cie_list);
 722         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 723
 724         return 0;
 725 }
 726
 727 static int dwarf_parse_fde(void *entry, u32 entry_type,
 728                            void *start, unsigned long len)
 729 {
 730         struct dwarf_fde *fde;
 731         struct dwarf_cie *cie;
 732         unsigned long flags;
 733         int count;
 734         void *p = start;
 735
 736         fde = kzalloc(sizeof(*fde), GFP_KERNEL);
 737         if (!fde)
 738                 return -ENOMEM;
 739
 740         fde->length = len;
 741
 742         /*
 743          * In a .eh_frame section the CIE pointer is the
 744          * delta between the address within the FDE
 745          */
 746         fde->cie_pointer = (unsigned long)(p - entry_type - 4);
 747
 748         cie = dwarf_lookup_cie(fde->cie_pointer);
 749         fde->cie = cie;
 750
 751         if (cie->encoding)
 752                 count = dwarf_read_encoded_value(p, &fde->initial_location,
 753                                                  cie->encoding);
 754         else
 755                 count = dwarf_read_addr(p, &fde->initial_location);
 756
 757         p += count;
 758
 759         if (cie->encoding)
 760                 count = dwarf_read_encoded_value(p, &fde->address_range,
 761                                                  cie->encoding & 0x0f);
 762         else
 763                 count = dwarf_read_addr(p, &fde->address_range);
 764
 765         p += count;
 766
 767         if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
 768                 unsigned int length;
 769                 count = dwarf_read_uleb128(p, &length);
 770                 p += count + length;
 771         }
 772
 773         /* Call frame instructions. */
 774         fde->instructions = p;
 775         fde->end = start + len;
 776
 777         /* Add to list. */
 778         spin_lock_irqsave(&dwarf_fde_lock, flags);
 779         list_add_tail(&fde->link, &dwarf_fde_list);
 780         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 781
 782         return 0;
 783 }
 784
 785 static void dwarf_unwinder_dump(struct task_struct *task, struct pt_regs *regs,
 786                                 unsigned long *sp,
 787                                 const struct stacktrace_ops *ops, void *data)
 788 {
 789         struct dwarf_frame *frame;
 790
 791         frame = dwarf_unwind_stack(0, NULL);
 792
 793         while (frame && frame->return_addr) {
 794                 ops->address(data, frame->return_addr, 1);
 795                 frame = frame->next;
 796         }
 797 }
 798
 799 static struct unwinder dwarf_unwinder = {
 800         .name = "dwarf-unwinder",
 801         .dump = dwarf_unwinder_dump,
 802         .rating = 150,
 803 };
 804
 805 static void dwarf_unwinder_cleanup(void)
 806 {
 807         struct dwarf_cie *cie, *m;
 808         struct dwarf_fde *fde, *n;
 809         unsigned long flags;
 810
 811         /*
 812          * Deallocate all the memory allocated for the DWARF unwinder.
 813          * Traverse all the FDE/CIE lists and remove and free all the
 814          * memory associated with those data structures.
 815          */
 816         spin_lock_irqsave(&dwarf_cie_lock, flags);
 817         list_for_each_entry_safe(cie, m, &dwarf_cie_list, link)
 818                 kfree(cie);
 819         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 820
 821         spin_lock_irqsave(&dwarf_fde_lock, flags);
 822         list_for_each_entry_safe(fde, n, &dwarf_fde_list, link)
 823                 kfree(fde);
 824         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 825 }
 826
 827 /**
 828  *      dwarf_unwinder_init - initialise the dwarf unwinder
 829  *
 830  *      Build the data structures describing the .dwarf_frame section to
 831  *      make it easier to lookup CIE and FDE entries. Because the
 832  *      .eh_frame section is packed as tightly as possible it is not
 833  *      easy to lookup the FDE for a given PC, so we build a list of FDE
 834  *      and CIE entries that make it easier.
 835  */
 836 void dwarf_unwinder_init(void)
 837 {
 838         u32 entry_type;
 839         void *p, *entry;
 840         int count, err;
 841         unsigned long len;
 842         unsigned int c_entries, f_entries;
 843         unsigned char *end;
 844         INIT_LIST_HEAD(&dwarf_cie_list);
 845         INIT_LIST_HEAD(&dwarf_fde_list);
 846
 847         c_entries = 0;
 848         f_entries = 0;
 849         entry = &__start_eh_frame;
 850
 851         while ((char *)entry < __stop_eh_frame) {
 852                 p = entry;
 853
 854                 count = dwarf_entry_len(p, &len);
 855                 if (count == 0) {
 856                         /*
 857                          * We read a bogus length field value. There is
 858                          * nothing we can do here apart from disabling
 859                          * the DWARF unwinder. We can't even skip this
 860                          * entry and move to the next one because 'len'
 861                          * tells us where our next entry is.
 862                          */
 863                         goto out;
 864                 } else
 865                         p += count;
 866
 867                 /* initial length does not include itself */
 868                 end = p + len;
 869
 870                 entry_type = get_unaligned((u32 *)p);
 871                 p += 4;
 872
 873                 if (entry_type == DW_EH_FRAME_CIE) {
 874                         err = dwarf_parse_cie(entry, p, len, end);
 875                         if (err < 0)
 876                                 goto out;
 877                         else
 878                                 c_entries++;
 879                 } else {
 880                         err = dwarf_parse_fde(entry, entry_type, p, len);
 881                         if (err < 0)
 882                                 goto out;
 883                         else
 884                                 f_entries++;
 885                 }
 886
 887                 entry = (char *)entry + len + 4;
 888         }
 889
 890         printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
 891                c_entries, f_entries);
 892
 893         err = unwinder_register(&dwarf_unwinder);
 894         if (err)
 895                 goto out;
 896
 897         return;
 898
 899 out:
 900         printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
 901         dwarf_unwinder_cleanup();
 902 }