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  *      - Registers with DWARF_VAL_OFFSET rules aren't handled properly.
  15  */
  16
  17 /* #define DEBUG */
  18 #include <linux/kernel.h>
  19 #include <linux/io.h>
  20 #include <linux/list.h>
  21 #include <linux/mempool.h>
  22 #include <linux/mm.h>
  23 #include <linux/elf.h>
  24 #include <linux/ftrace.h>
  25 #include <asm/dwarf.h>
  26 #include <asm/unwinder.h>
  27 #include <asm/sections.h>
  28 #include <asm/unaligned.h>
  29 #include <asm/stacktrace.h>
  30
  31 /* Reserve enough memory for two stack frames */
  32 #define DWARF_FRAME_MIN_REQ     2
  33 /* ... with 4 registers per frame. */
  34 #define DWARF_REG_MIN_REQ       (DWARF_FRAME_MIN_REQ * 4)
  35
  36 static struct kmem_cache *dwarf_frame_cachep;
  37 static mempool_t *dwarf_frame_pool;
  38
  39 static struct kmem_cache *dwarf_reg_cachep;
  40 static mempool_t *dwarf_reg_pool;
  41
  42 static struct rb_root cie_root;
  43 static DEFINE_SPINLOCK(dwarf_cie_lock);
  44
  45 static struct rb_root fde_root;
  46 static DEFINE_SPINLOCK(dwarf_fde_lock);
  47
  48 static struct dwarf_cie *cached_cie;
  49
  50 /**
  51  *      dwarf_frame_alloc_reg - allocate memory for a DWARF register
  52  *      @frame: the DWARF frame whose list of registers we insert on
  53  *      @reg_num: the register number
  54  *
  55  *      Allocate space for, and initialise, a dwarf reg from
  56  *      dwarf_reg_pool and insert it onto the (unsorted) linked-list of
  57  *      dwarf registers for @frame.
  58  *
  59  *      Return the initialised DWARF reg.
  60  */
  61 static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
  62                                                unsigned int reg_num)
  63 {
  64         struct dwarf_reg *reg;
  65
  66         reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
  67         if (!reg) {
  68                 printk(KERN_WARNING "Unable to allocate a DWARF register\n");
  69                 /*
  70                  * Let's just bomb hard here, we have no way to
  71                  * gracefully recover.
  72                  */
  73                 UNWINDER_BUG();
  74         }
  75
  76         reg->number = reg_num;
  77         reg->addr = 0;
  78         reg->flags = 0;
  79
  80         list_add(&reg->link, &frame->reg_list);
  81
  82         return reg;
  83 }
  84
  85 static void dwarf_frame_free_regs(struct dwarf_frame *frame)
  86 {
  87         struct dwarf_reg *reg, *n;
  88
  89         list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
  90                 list_del(&reg->link);
  91                 mempool_free(reg, dwarf_reg_pool);
  92         }
  93 }
  94
  95 /**
  96  *      dwarf_frame_reg - return a DWARF register
  97  *      @frame: the DWARF frame to search in for @reg_num
  98  *      @reg_num: the register number to search for
  99  *
 100  *      Lookup and return the dwarf reg @reg_num for this frame. Return
 101  *      NULL if @reg_num is an register invalid number.
 102  */
 103 static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
 104                                          unsigned int reg_num)
 105 {
 106         struct dwarf_reg *reg;
 107
 108         list_for_each_entry(reg, &frame->reg_list, link) {
 109                 if (reg->number == reg_num)
 110                         return reg;
 111         }
 112
 113         return NULL;
 114 }
 115
 116 /**
 117  *      dwarf_read_addr - read dwarf data
 118  *      @src: source address of data
 119  *      @dst: destination address to store the data to
 120  *
 121  *      Read 'n' bytes from @src, where 'n' is the size of an address on
 122  *      the native machine. We return the number of bytes read, which
 123  *      should always be 'n'. We also have to be careful when reading
 124  *      from @src and writing to @dst, because they can be arbitrarily
 125  *      aligned. Return 'n' - the number of bytes read.
 126  */
 127 static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
 128 {
 129         u32 val = get_unaligned(src);
 130         put_unaligned(val, dst);
 131         return sizeof(unsigned long *);
 132 }
 133
 134 /**
 135  *      dwarf_read_uleb128 - read unsigned LEB128 data
 136  *      @addr: the address where the ULEB128 data is stored
 137  *      @ret: address to store the result
 138  *
 139  *      Decode an unsigned LEB128 encoded datum. The algorithm is taken
 140  *      from Appendix C of the DWARF 3 spec. For information on the
 141  *      encodings refer to section "7.6 - Variable Length Data". Return
 142  *      the number of bytes read.
 143  */
 144 static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
 145 {
 146         unsigned int result;
 147         unsigned char byte;
 148         int shift, count;
 149
 150         result = 0;
 151         shift = 0;
 152         count = 0;
 153
 154         while (1) {
 155                 byte = __raw_readb(addr);
 156                 addr++;
 157                 count++;
 158
 159                 result |= (byte & 0x7f) << shift;
 160                 shift += 7;
 161
 162                 if (!(byte & 0x80))
 163                         break;
 164         }
 165
 166         *ret = result;
 167
 168         return count;
 169 }
 170
 171 /**
 172  *      dwarf_read_leb128 - read signed LEB128 data
 173  *      @addr: the address of the LEB128 encoded data
 174  *      @ret: address to store the result
 175  *
 176  *      Decode signed LEB128 data. The algorithm is taken from Appendix
 177  *      C of the DWARF 3 spec. Return the number of bytes read.
 178  */
 179 static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
 180 {
 181         unsigned char byte;
 182         int result, shift;
 183         int num_bits;
 184         int count;
 185
 186         result = 0;
 187         shift = 0;
 188         count = 0;
 189
 190         while (1) {
 191                 byte = __raw_readb(addr);
 192                 addr++;
 193                 result |= (byte & 0x7f) << shift;
 194                 shift += 7;
 195                 count++;
 196
 197                 if (!(byte & 0x80))
 198                         break;
 199         }
 200
 201         /* The number of bits in a signed integer. */
 202         num_bits = 8 * sizeof(result);
 203
 204         if ((shift < num_bits) && (byte & 0x40))
 205                 result |= (-1 << shift);
 206
 207         *ret = result;
 208
 209         return count;
 210 }
 211
 212 /**
 213  *      dwarf_read_encoded_value - return the decoded value at @addr
 214  *      @addr: the address of the encoded value
 215  *      @val: where to write the decoded value
 216  *      @encoding: the encoding with which we can decode @addr
 217  *
 218  *      GCC emits encoded address in the .eh_frame FDE entries. Decode
 219  *      the value at @addr using @encoding. The decoded value is written
 220  *      to @val and the number of bytes read is returned.
 221  */
 222 static int dwarf_read_encoded_value(char *addr, unsigned long *val,
 223                                     char encoding)
 224 {
 225         unsigned long decoded_addr = 0;
 226         int count = 0;
 227
 228         switch (encoding & 0x70) {
 229         case DW_EH_PE_absptr:
 230                 break;
 231         case DW_EH_PE_pcrel:
 232                 decoded_addr = (unsigned long)addr;
 233                 break;
 234         default:
 235                 pr_debug("encoding=0x%x\n", (encoding & 0x70));
 236                 UNWINDER_BUG();
 237         }
 238
 239         if ((encoding & 0x07) == 0x00)
 240                 encoding |= DW_EH_PE_udata4;
 241
 242         switch (encoding & 0x0f) {
 243         case DW_EH_PE_sdata4:
 244         case DW_EH_PE_udata4:
 245                 count += 4;
 246                 decoded_addr += get_unaligned((u32 *)addr);
 247                 __raw_writel(decoded_addr, val);
 248                 break;
 249         default:
 250                 pr_debug("encoding=0x%x\n", encoding);
 251                 UNWINDER_BUG();
 252         }
 253
 254         return count;
 255 }
 256
 257 /**
 258  *      dwarf_entry_len - return the length of an FDE or CIE
 259  *      @addr: the address of the entry
 260  *      @len: the length of the entry
 261  *
 262  *      Read the initial_length field of the entry and store the size of
 263  *      the entry in @len. We return the number of bytes read. Return a
 264  *      count of 0 on error.
 265  */
 266 static inline int dwarf_entry_len(char *addr, unsigned long *len)
 267 {
 268         u32 initial_len;
 269         int count;
 270
 271         initial_len = get_unaligned((u32 *)addr);
 272         count = 4;
 273
 274         /*
 275          * An initial length field value in the range DW_LEN_EXT_LO -
 276          * DW_LEN_EXT_HI indicates an extension, and should not be
 277          * interpreted as a length. The only extension that we currently
 278          * understand is the use of DWARF64 addresses.
 279          */
 280         if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
 281                 /*
 282                  * The 64-bit length field immediately follows the
 283                  * compulsory 32-bit length field.
 284                  */
 285                 if (initial_len == DW_EXT_DWARF64) {
 286                         *len = get_unaligned((u64 *)addr + 4);
 287                         count = 12;
 288                 } else {
 289                         printk(KERN_WARNING "Unknown DWARF extension\n");
 290                         count = 0;
 291                 }
 292         } else
 293                 *len = initial_len;
 294
 295         return count;
 296 }
 297
 298 /**
 299  *      dwarf_lookup_cie - locate the cie
 300  *      @cie_ptr: pointer to help with lookup
 301  */
 302 static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
 303 {
 304         struct rb_node **rb_node = &cie_root.rb_node;
 305         struct dwarf_cie *cie = NULL;
 306         unsigned long flags;
 307
 308         spin_lock_irqsave(&dwarf_cie_lock, flags);
 309
 310         /*
 311          * We've cached the last CIE we looked up because chances are
 312          * that the FDE wants this CIE.
 313          */
 314         if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
 315                 cie = cached_cie;
 316                 goto out;
 317         }
 318
 319         while (*rb_node) {
 320                 struct dwarf_cie *cie_tmp;
 321
 322                 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
 323                 BUG_ON(!cie_tmp);
 324
 325                 if (cie_ptr == cie_tmp->cie_pointer) {
 326                         cie = cie_tmp;
 327                         cached_cie = cie_tmp;
 328                         goto out;
 329                 } else {
 330                         if (cie_ptr < cie_tmp->cie_pointer)
 331                                 rb_node = &(*rb_node)->rb_left;
 332                         else
 333                                 rb_node = &(*rb_node)->rb_right;
 334                 }
 335         }
 336
 337 out:
 338         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 339         return cie;
 340 }
 341
 342 /**
 343  *      dwarf_lookup_fde - locate the FDE that covers pc
 344  *      @pc: the program counter
 345  */
 346 struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
 347 {
 348         struct rb_node **rb_node = &fde_root.rb_node;
 349         struct dwarf_fde *fde = NULL;
 350         unsigned long flags;
 351
 352         spin_lock_irqsave(&dwarf_fde_lock, flags);
 353
 354         while (*rb_node) {
 355                 struct dwarf_fde *fde_tmp;
 356                 unsigned long tmp_start, tmp_end;
 357
 358                 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
 359                 BUG_ON(!fde_tmp);
 360
 361                 tmp_start = fde_tmp->initial_location;
 362                 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
 363
 364                 if (pc < tmp_start) {
 365                         rb_node = &(*rb_node)->rb_left;
 366                 } else {
 367                         if (pc < tmp_end) {
 368                                 fde = fde_tmp;
 369                                 goto out;
 370                         } else
 371                                 rb_node = &(*rb_node)->rb_right;
 372                 }
 373         }
 374
 375 out:
 376         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 377
 378         return fde;
 379 }
 380
 381 /**
 382  *      dwarf_cfa_execute_insns - execute instructions to calculate a CFA
 383  *      @insn_start: address of the first instruction
 384  *      @insn_end: address of the last instruction
 385  *      @cie: the CIE for this function
 386  *      @fde: the FDE for this function
 387  *      @frame: the instructions calculate the CFA for this frame
 388  *      @pc: the program counter of the address we're interested in
 389  *
 390  *      Execute the Call Frame instruction sequence starting at
 391  *      @insn_start and ending at @insn_end. The instructions describe
 392  *      how to calculate the Canonical Frame Address of a stackframe.
 393  *      Store the results in @frame.
 394  */
 395 static int dwarf_cfa_execute_insns(unsigned char *insn_start,
 396                                    unsigned char *insn_end,
 397                                    struct dwarf_cie *cie,
 398                                    struct dwarf_fde *fde,
 399                                    struct dwarf_frame *frame,
 400                                    unsigned long pc)
 401 {
 402         unsigned char insn;
 403         unsigned char *current_insn;
 404         unsigned int count, delta, reg, expr_len, offset;
 405         struct dwarf_reg *regp;
 406
 407         current_insn = insn_start;
 408
 409         while (current_insn < insn_end && frame->pc <= pc) {
 410                 insn = __raw_readb(current_insn++);
 411
 412                 /*
 413                  * Firstly, handle the opcodes that embed their operands
 414                  * in the instructions.
 415                  */
 416                 switch (DW_CFA_opcode(insn)) {
 417                 case DW_CFA_advance_loc:
 418                         delta = DW_CFA_operand(insn);
 419                         delta *= cie->code_alignment_factor;
 420                         frame->pc += delta;
 421                         continue;
 422                         /* NOTREACHED */
 423                 case DW_CFA_offset:
 424                         reg = DW_CFA_operand(insn);
 425                         count = dwarf_read_uleb128(current_insn, &offset);
 426                         current_insn += count;
 427                         offset *= cie->data_alignment_factor;
 428                         regp = dwarf_frame_alloc_reg(frame, reg);
 429                         regp->addr = offset;
 430                         regp->flags |= DWARF_REG_OFFSET;
 431                         continue;
 432                         /* NOTREACHED */
 433                 case DW_CFA_restore:
 434                         reg = DW_CFA_operand(insn);
 435                         continue;
 436                         /* NOTREACHED */
 437                 }
 438
 439                 /*
 440                  * Secondly, handle the opcodes that don't embed their
 441                  * operands in the instruction.
 442                  */
 443                 switch (insn) {
 444                 case DW_CFA_nop:
 445                         continue;
 446                 case DW_CFA_advance_loc1:
 447                         delta = *current_insn++;
 448                         frame->pc += delta * cie->code_alignment_factor;
 449                         break;
 450                 case DW_CFA_advance_loc2:
 451                         delta = get_unaligned((u16 *)current_insn);
 452                         current_insn += 2;
 453                         frame->pc += delta * cie->code_alignment_factor;
 454                         break;
 455                 case DW_CFA_advance_loc4:
 456                         delta = get_unaligned((u32 *)current_insn);
 457                         current_insn += 4;
 458                         frame->pc += delta * cie->code_alignment_factor;
 459                         break;
 460                 case DW_CFA_offset_extended:
 461                         count = dwarf_read_uleb128(current_insn, &reg);
 462                         current_insn += count;
 463                         count = dwarf_read_uleb128(current_insn, &offset);
 464                         current_insn += count;
 465                         offset *= cie->data_alignment_factor;
 466                         break;
 467                 case DW_CFA_restore_extended:
 468                         count = dwarf_read_uleb128(current_insn, &reg);
 469                         current_insn += count;
 470                         break;
 471                 case DW_CFA_undefined:
 472                         count = dwarf_read_uleb128(current_insn, &reg);
 473                         current_insn += count;
 474                         regp = dwarf_frame_alloc_reg(frame, reg);
 475                         regp->flags |= DWARF_UNDEFINED;
 476                         break;
 477                 case DW_CFA_def_cfa:
 478                         count = dwarf_read_uleb128(current_insn,
 479                                                    &frame->cfa_register);
 480                         current_insn += count;
 481                         count = dwarf_read_uleb128(current_insn,
 482                                                    &frame->cfa_offset);
 483                         current_insn += count;
 484
 485                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
 486                         break;
 487                 case DW_CFA_def_cfa_register:
 488                         count = dwarf_read_uleb128(current_insn,
 489                                                    &frame->cfa_register);
 490                         current_insn += count;
 491                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
 492                         break;
 493                 case DW_CFA_def_cfa_offset:
 494                         count = dwarf_read_uleb128(current_insn, &offset);
 495                         current_insn += count;
 496                         frame->cfa_offset = offset;
 497                         break;
 498                 case DW_CFA_def_cfa_expression:
 499                         count = dwarf_read_uleb128(current_insn, &expr_len);
 500                         current_insn += count;
 501
 502                         frame->cfa_expr = current_insn;
 503                         frame->cfa_expr_len = expr_len;
 504                         current_insn += expr_len;
 505
 506                         frame->flags |= DWARF_FRAME_CFA_REG_EXP;
 507                         break;
 508                 case DW_CFA_offset_extended_sf:
 509                         count = dwarf_read_uleb128(current_insn, &reg);
 510                         current_insn += count;
 511                         count = dwarf_read_leb128(current_insn, &offset);
 512                         current_insn += count;
 513                         offset *= cie->data_alignment_factor;
 514                         regp = dwarf_frame_alloc_reg(frame, reg);
 515                         regp->flags |= DWARF_REG_OFFSET;
 516                         regp->addr = offset;
 517                         break;
 518                 case DW_CFA_val_offset:
 519                         count = dwarf_read_uleb128(current_insn, &reg);
 520                         current_insn += count;
 521                         count = dwarf_read_leb128(current_insn, &offset);
 522                         offset *= cie->data_alignment_factor;
 523                         regp = dwarf_frame_alloc_reg(frame, reg);
 524                         regp->flags |= DWARF_VAL_OFFSET;
 525                         regp->addr = offset;
 526                         break;
 527                 case DW_CFA_GNU_args_size:
 528                         count = dwarf_read_uleb128(current_insn, &offset);
 529                         current_insn += count;
 530                         break;
 531                 case DW_CFA_GNU_negative_offset_extended:
 532                         count = dwarf_read_uleb128(current_insn, &reg);
 533                         current_insn += count;
 534                         count = dwarf_read_uleb128(current_insn, &offset);
 535                         offset *= cie->data_alignment_factor;
 536
 537                         regp = dwarf_frame_alloc_reg(frame, reg);
 538                         regp->flags |= DWARF_REG_OFFSET;
 539                         regp->addr = -offset;
 540                         break;
 541                 default:
 542                         pr_debug("unhandled DWARF instruction 0x%x\n", insn);
 543                         UNWINDER_BUG();
 544                         break;
 545                 }
 546         }
 547
 548         return 0;
 549 }
 550
 551 /**
 552  *      dwarf_free_frame - free the memory allocated for @frame
 553  *      @frame: the frame to free
 554  */
 555 void dwarf_free_frame(struct dwarf_frame *frame)
 556 {
 557         dwarf_frame_free_regs(frame);
 558         mempool_free(frame, dwarf_frame_pool);
 559 }
 560
 561 extern void ret_from_irq(void);
 562
 563 /**
 564  *      dwarf_unwind_stack - unwind the stack
 565  *
 566  *      @pc: address of the function to unwind
 567  *      @prev: struct dwarf_frame of the previous stackframe on the callstack
 568  *
 569  *      Return a struct dwarf_frame representing the most recent frame
 570  *      on the callstack. Each of the lower (older) stack frames are
 571  *      linked via the "prev" member.
 572  */
 573 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
 574                                        struct dwarf_frame *prev)
 575 {
 576         struct dwarf_frame *frame;
 577         struct dwarf_cie *cie;
 578         struct dwarf_fde *fde;
 579         struct dwarf_reg *reg;
 580         unsigned long addr;
 581
 582         /*
 583          * If we're starting at the top of the stack we need get the
 584          * contents of a physical register to get the CFA in order to
 585          * begin the virtual unwinding of the stack.
 586          *
 587          * NOTE: the return address is guaranteed to be setup by the
 588          * time this function makes its first function call.
 589          */
 590         if (!pc || !prev)
 591                 pc = (unsigned long)current_text_addr();
 592
 593 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 594         /*
 595          * If our stack has been patched by the function graph tracer
 596          * then we might see the address of return_to_handler() where we
 597          * expected to find the real return address.
 598          */
 599         if (pc == (unsigned long)&return_to_handler) {
 600                 int index = current->curr_ret_stack;
 601
 602                 /*
 603                  * We currently have no way of tracking how many
 604                  * return_to_handler()'s we've seen. If there is more
 605                  * than one patched return address on our stack,
 606                  * complain loudly.
 607                  */
 608                 WARN_ON(index > 0);
 609
 610                 pc = current->ret_stack[index].ret;
 611         }
 612 #endif
 613
 614         frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
 615         if (!frame) {
 616                 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
 617                 UNWINDER_BUG();
 618         }
 619
 620         INIT_LIST_HEAD(&frame->reg_list);
 621         frame->flags = 0;
 622         frame->prev = prev;
 623         frame->return_addr = 0;
 624
 625         fde = dwarf_lookup_fde(pc);
 626         if (!fde) {
 627                 /*
 628                  * This is our normal exit path. There are two reasons
 629                  * why we might exit here,
 630                  *
 631                  *      a) pc has no asscociated DWARF frame info and so
 632                  *      we don't know how to unwind this frame. This is
 633                  *      usually the case when we're trying to unwind a
 634                  *      frame that was called from some assembly code
 635                  *      that has no DWARF info, e.g. syscalls.
 636                  *
 637                  *      b) the DEBUG info for pc is bogus. There's
 638                  *      really no way to distinguish this case from the
 639                  *      case above, which sucks because we could print a
 640                  *      warning here.
 641                  */
 642                 goto bail;
 643         }
 644
 645         cie = dwarf_lookup_cie(fde->cie_pointer);
 646
 647         frame->pc = fde->initial_location;
 648
 649         /* CIE initial instructions */
 650         dwarf_cfa_execute_insns(cie->initial_instructions,
 651                                 cie->instructions_end, cie, fde,
 652                                 frame, pc);
 653
 654         /* FDE instructions */
 655         dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
 656                                 fde, frame, pc);
 657
 658         /* Calculate the CFA */
 659         switch (frame->flags) {
 660         case DWARF_FRAME_CFA_REG_OFFSET:
 661                 if (prev) {
 662                         reg = dwarf_frame_reg(prev, frame->cfa_register);
 663                         UNWINDER_BUG_ON(!reg);
 664                         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 665
 666                         addr = prev->cfa + reg->addr;
 667                         frame->cfa = __raw_readl(addr);
 668
 669                 } else {
 670                         /*
 671                          * Again, we're starting from the top of the
 672                          * stack. We need to physically read
 673                          * the contents of a register in order to get
 674                          * the Canonical Frame Address for this
 675                          * function.
 676                          */
 677                         frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
 678                 }
 679
 680                 frame->cfa += frame->cfa_offset;
 681                 break;
 682         default:
 683                 UNWINDER_BUG();
 684         }
 685
 686         reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
 687
 688         /*
 689          * If we haven't seen the return address register or the return
 690          * address column is undefined then we must assume that this is
 691          * the end of the callstack.
 692          */
 693         if (!reg || reg->flags == DWARF_UNDEFINED)
 694                 goto bail;
 695
 696         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 697
 698         addr = frame->cfa + reg->addr;
 699         frame->return_addr = __raw_readl(addr);
 700
 701         /*
 702          * Ah, the joys of unwinding through interrupts.
 703          *
 704          * Interrupts are tricky - the DWARF info needs to be _really_
 705          * accurate and unfortunately I'm seeing a lot of bogus DWARF
 706          * info. For example, I've seen interrupts occur in epilogues
 707          * just after the frame pointer (r14) had been restored. The
 708          * problem was that the DWARF info claimed that the CFA could be
 709          * reached by using the value of the frame pointer before it was
 710          * restored.
 711          *
 712          * So until the compiler can be trusted to produce reliable
 713          * DWARF info when it really matters, let's stop unwinding once
 714          * we've calculated the function that was interrupted.
 715          */
 716         if (prev && prev->pc == (unsigned long)ret_from_irq)
 717                 frame->return_addr = 0;
 718
 719         return frame;
 720
 721 bail:
 722         dwarf_free_frame(frame);
 723         return NULL;
 724 }
 725
 726 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
 727                            unsigned char *end, struct module *mod)
 728 {
 729         struct rb_node **rb_node = &cie_root.rb_node;
 730         struct rb_node *parent = *rb_node;
 731         struct dwarf_cie *cie;
 732         unsigned long flags;
 733         int count;
 734
 735         cie = kzalloc(sizeof(*cie), GFP_KERNEL);
 736         if (!cie)
 737                 return -ENOMEM;
 738
 739         cie->length = len;
 740
 741         /*
 742          * Record the offset into the .eh_frame section
 743          * for this CIE. It allows this CIE to be
 744          * quickly and easily looked up from the
 745          * corresponding FDE.
 746          */
 747         cie->cie_pointer = (unsigned long)entry;
 748
 749         cie->version = *(char *)p++;
 750         UNWINDER_BUG_ON(cie->version != 1);
 751
 752         cie->augmentation = p;
 753         p += strlen(cie->augmentation) + 1;
 754
 755         count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
 756         p += count;
 757
 758         count = dwarf_read_leb128(p, &cie->data_alignment_factor);
 759         p += count;
 760
 761         /*
 762          * Which column in the rule table contains the
 763          * return address?
 764          */
 765         if (cie->version == 1) {
 766                 cie->return_address_reg = __raw_readb(p);
 767                 p++;
 768         } else {
 769                 count = dwarf_read_uleb128(p, &cie->return_address_reg);
 770                 p += count;
 771         }
 772
 773         if (cie->augmentation[0] == 'z') {
 774                 unsigned int length, count;
 775                 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
 776
 777                 count = dwarf_read_uleb128(p, &length);
 778                 p += count;
 779
 780                 UNWINDER_BUG_ON((unsigned char *)p > end);
 781
 782                 cie->initial_instructions = p + length;
 783                 cie->augmentation++;
 784         }
 785
 786         while (*cie->augmentation) {
 787                 /*
 788                  * "L" indicates a byte showing how the
 789                  * LSDA pointer is encoded. Skip it.
 790                  */
 791                 if (*cie->augmentation == 'L') {
 792                         p++;
 793                         cie->augmentation++;
 794                 } else if (*cie->augmentation == 'R') {
 795                         /*
 796                          * "R" indicates a byte showing
 797                          * how FDE addresses are
 798                          * encoded.
 799                          */
 800                         cie->encoding = *(char *)p++;
 801                         cie->augmentation++;
 802                 } else if (*cie->augmentation == 'P') {
 803                         /*
 804                          * "R" indicates a personality
 805                          * routine in the CIE
 806                          * augmentation.
 807                          */
 808                         UNWINDER_BUG();
 809                 } else if (*cie->augmentation == 'S') {
 810                         UNWINDER_BUG();
 811                 } else {
 812                         /*
 813                          * Unknown augmentation. Assume
 814                          * 'z' augmentation.
 815                          */
 816                         p = cie->initial_instructions;
 817                         UNWINDER_BUG_ON(!p);
 818                         break;
 819                 }
 820         }
 821
 822         cie->initial_instructions = p;
 823         cie->instructions_end = end;
 824
 825         /* Add to list */
 826         spin_lock_irqsave(&dwarf_cie_lock, flags);
 827
 828         while (*rb_node) {
 829                 struct dwarf_cie *cie_tmp;
 830
 831                 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
 832
 833                 parent = *rb_node;
 834
 835                 if (cie->cie_pointer < cie_tmp->cie_pointer)
 836                         rb_node = &parent->rb_left;
 837                 else if (cie->cie_pointer >= cie_tmp->cie_pointer)
 838                         rb_node = &parent->rb_right;
 839                 else
 840                         WARN_ON(1);
 841         }
 842
 843         rb_link_node(&cie->node, parent, rb_node);
 844         rb_insert_color(&cie->node, &cie_root);
 845
 846         if (mod != NULL)
 847                 list_add_tail(&cie->link, &mod->arch.cie_list);
 848
 849         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 850
 851         return 0;
 852 }
 853
 854 static int dwarf_parse_fde(void *entry, u32 entry_type,
 855                            void *start, unsigned long len,
 856                            unsigned char *end, struct module *mod)
 857 {
 858         struct rb_node **rb_node = &fde_root.rb_node;
 859         struct rb_node *parent = *rb_node;
 860         struct dwarf_fde *fde;
 861         struct dwarf_cie *cie;
 862         unsigned long flags;
 863         int count;
 864         void *p = start;
 865
 866         fde = kzalloc(sizeof(*fde), GFP_KERNEL);
 867         if (!fde)
 868                 return -ENOMEM;
 869
 870         fde->length = len;
 871
 872         /*
 873          * In a .eh_frame section the CIE pointer is the
 874          * delta between the address within the FDE
 875          */
 876         fde->cie_pointer = (unsigned long)(p - entry_type - 4);
 877
 878         cie = dwarf_lookup_cie(fde->cie_pointer);
 879         fde->cie = cie;
 880
 881         if (cie->encoding)
 882                 count = dwarf_read_encoded_value(p, &fde->initial_location,
 883                                                  cie->encoding);
 884         else
 885                 count = dwarf_read_addr(p, &fde->initial_location);
 886
 887         p += count;
 888
 889         if (cie->encoding)
 890                 count = dwarf_read_encoded_value(p, &fde->address_range,
 891                                                  cie->encoding & 0x0f);
 892         else
 893                 count = dwarf_read_addr(p, &fde->address_range);
 894
 895         p += count;
 896
 897         if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
 898                 unsigned int length;
 899                 count = dwarf_read_uleb128(p, &length);
 900                 p += count + length;
 901         }
 902
 903         /* Call frame instructions. */
 904         fde->instructions = p;
 905         fde->end = end;
 906
 907         /* Add to list. */
 908         spin_lock_irqsave(&dwarf_fde_lock, flags);
 909
 910         while (*rb_node) {
 911                 struct dwarf_fde *fde_tmp;
 912                 unsigned long tmp_start, tmp_end;
 913                 unsigned long start, end;
 914
 915                 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
 916
 917                 start = fde->initial_location;
 918                 end = fde->initial_location + fde->address_range;
 919
 920                 tmp_start = fde_tmp->initial_location;
 921                 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
 922
 923                 parent = *rb_node;
 924
 925                 if (start < tmp_start)
 926                         rb_node = &parent->rb_left;
 927                 else if (start >= tmp_end)
 928                         rb_node = &parent->rb_right;
 929                 else
 930                         WARN_ON(1);
 931         }
 932
 933         rb_link_node(&fde->node, parent, rb_node);
 934         rb_insert_color(&fde->node, &fde_root);
 935
 936         if (mod != NULL)
 937                 list_add_tail(&fde->link, &mod->arch.fde_list);
 938
 939         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 940
 941         return 0;
 942 }
 943
 944 static void dwarf_unwinder_dump(struct task_struct *task,
 945                                 struct pt_regs *regs,
 946                                 unsigned long *sp,
 947                                 const struct stacktrace_ops *ops,
 948                                 void *data)
 949 {
 950         struct dwarf_frame *frame, *_frame;
 951         unsigned long return_addr;
 952
 953         _frame = NULL;
 954         return_addr = 0;
 955
 956         while (1) {
 957                 frame = dwarf_unwind_stack(return_addr, _frame);
 958
 959                 if (_frame)
 960                         dwarf_free_frame(_frame);
 961
 962                 _frame = frame;
 963
 964                 if (!frame || !frame->return_addr)
 965                         break;
 966
 967                 return_addr = frame->return_addr;
 968                 ops->address(data, return_addr, 1);
 969         }
 970
 971         if (frame)
 972                 dwarf_free_frame(frame);
 973 }
 974
 975 static struct unwinder dwarf_unwinder = {
 976         .name = "dwarf-unwinder",
 977         .dump = dwarf_unwinder_dump,
 978         .rating = 150,
 979 };
 980
 981 static void dwarf_unwinder_cleanup(void)
 982 {
 983         struct rb_node **fde_rb_node = &fde_root.rb_node;
 984         struct rb_node **cie_rb_node = &cie_root.rb_node;
 985
 986         /*
 987          * Deallocate all the memory allocated for the DWARF unwinder.
 988          * Traverse all the FDE/CIE lists and remove and free all the
 989          * memory associated with those data structures.
 990          */
 991         while (*fde_rb_node) {
 992                 struct dwarf_fde *fde;
 993
 994                 fde = rb_entry(*fde_rb_node, struct dwarf_fde, node);
 995                 rb_erase(*fde_rb_node, &fde_root);
 996                 kfree(fde);
 997         }
 998
 999         while (*cie_rb_node) {
1000                 struct dwarf_cie *cie;
1001
1002                 cie = rb_entry(*cie_rb_node, struct dwarf_cie, node);
1003                 rb_erase(*cie_rb_node, &cie_root);
1004                 kfree(cie);
1005         }
1006
1007         kmem_cache_destroy(dwarf_reg_cachep);
1008         kmem_cache_destroy(dwarf_frame_cachep);
1009 }
1010
1011 /**
1012  *      dwarf_parse_section - parse DWARF section
1013  *      @eh_frame_start: start address of the .eh_frame section
1014  *      @eh_frame_end: end address of the .eh_frame section
1015  *      @mod: the kernel module containing the .eh_frame section
1016  *
1017  *      Parse the information in a .eh_frame section.
1018  */
1019 static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1020                                struct module *mod)
1021 {
1022         u32 entry_type;
1023         void *p, *entry;
1024         int count, err = 0;
1025         unsigned long len = 0;
1026         unsigned int c_entries, f_entries;
1027         unsigned char *end;
1028
1029         c_entries = 0;
1030         f_entries = 0;
1031         entry = eh_frame_start;
1032
1033         while ((char *)entry < eh_frame_end) {
1034                 p = entry;
1035
1036                 count = dwarf_entry_len(p, &len);
1037                 if (count == 0) {
1038                         /*
1039                          * We read a bogus length field value. There is
1040                          * nothing we can do here apart from disabling
1041                          * the DWARF unwinder. We can't even skip this
1042                          * entry and move to the next one because 'len'
1043                          * tells us where our next entry is.
1044                          */
1045                         err = -EINVAL;
1046                         goto out;
1047                 } else
1048                         p += count;
1049
1050                 /* initial length does not include itself */
1051                 end = p + len;
1052
1053                 entry_type = get_unaligned((u32 *)p);
1054                 p += 4;
1055
1056                 if (entry_type == DW_EH_FRAME_CIE) {
1057                         err = dwarf_parse_cie(entry, p, len, end, mod);
1058                         if (err < 0)
1059                                 goto out;
1060                         else
1061                                 c_entries++;
1062                 } else {
1063                         err = dwarf_parse_fde(entry, entry_type, p, len,
1064                                               end, mod);
1065                         if (err < 0)
1066                                 goto out;
1067                         else
1068                                 f_entries++;
1069                 }
1070
1071                 entry = (char *)entry + len + 4;
1072         }
1073
1074         printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1075                c_entries, f_entries);
1076
1077         return 0;
1078
1079 out:
1080         return err;
1081 }
1082
1083 #ifdef CONFIG_MODULES
1084 int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1085                           struct module *me)
1086 {
1087         unsigned int i, err;
1088         unsigned long start, end;
1089         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
1090
1091         start = end = 0;
1092
1093         for (i = 1; i < hdr->e_shnum; i++) {
1094                 /* Alloc bit cleared means "ignore it." */
1095                 if ((sechdrs[i].sh_flags & SHF_ALLOC)
1096                     && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
1097                         start = sechdrs[i].sh_addr;
1098                         end = start + sechdrs[i].sh_size;
1099                         break;
1100                 }
1101         }
1102
1103         /* Did we find the .eh_frame section? */
1104         if (i != hdr->e_shnum) {
1105                 INIT_LIST_HEAD(&me->arch.cie_list);
1106                 INIT_LIST_HEAD(&me->arch.fde_list);
1107                 err = dwarf_parse_section((char *)start, (char *)end, me);
1108                 if (err) {
1109                         printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1110                                me->name);
1111                         return err;
1112                 }
1113         }
1114
1115         return 0;
1116 }
1117
1118 /**
1119  *      module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1120  *      @mod: the module that is being unloaded
1121  *
1122  *      Remove any FDEs and CIEs from the global lists that came from
1123  *      @mod's .eh_frame section because @mod is being unloaded.
1124  */
1125 void module_dwarf_cleanup(struct module *mod)
1126 {
1127         struct dwarf_fde *fde, *ftmp;
1128         struct dwarf_cie *cie, *ctmp;
1129         unsigned long flags;
1130
1131         spin_lock_irqsave(&dwarf_cie_lock, flags);
1132
1133         list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
1134                 list_del(&cie->link);
1135                 rb_erase(&cie->node, &cie_root);
1136                 kfree(cie);
1137         }
1138
1139         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1140
1141         spin_lock_irqsave(&dwarf_fde_lock, flags);
1142
1143         list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
1144                 list_del(&fde->link);
1145                 rb_erase(&fde->node, &fde_root);
1146                 kfree(fde);
1147         }
1148
1149         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1150 }
1151 #endif /* CONFIG_MODULES */
1152
1153 /**
1154  *      dwarf_unwinder_init - initialise the dwarf unwinder
1155  *
1156  *      Build the data structures describing the .dwarf_frame section to
1157  *      make it easier to lookup CIE and FDE entries. Because the
1158  *      .eh_frame section is packed as tightly as possible it is not
1159  *      easy to lookup the FDE for a given PC, so we build a list of FDE
1160  *      and CIE entries that make it easier.
1161  */
1162 static int __init dwarf_unwinder_init(void)
1163 {
1164         int err;
1165
1166         dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1167                         sizeof(struct dwarf_frame), 0,
1168                         SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1169
1170         dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1171                         sizeof(struct dwarf_reg), 0,
1172                         SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1173
1174         dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
1175                                           mempool_alloc_slab,
1176                                           mempool_free_slab,
1177                                           dwarf_frame_cachep);
1178
1179         dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
1180                                          mempool_alloc_slab,
1181                                          mempool_free_slab,
1182                                          dwarf_reg_cachep);
1183
1184         err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1185         if (err)
1186                 goto out;
1187
1188         err = unwinder_register(&dwarf_unwinder);
1189         if (err)
1190                 goto out;
1191
1192         return 0;
1193
1194 out:
1195         printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1196         dwarf_unwinder_cleanup();
1197         return -EINVAL;
1198 }
1199 early_initcall(dwarf_unwinder_init);