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 <linux/module.h>
  26 #include <linux/slab.h>
  27 #include <asm/dwarf.h>
  28 #include <asm/unwinder.h>
  29 #include <asm/sections.h>
  30 #include <asm/unaligned.h>
  31 #include <asm/stacktrace.h>
  32
  33 /* Reserve enough memory for two stack frames */
  34 #define DWARF_FRAME_MIN_REQ     2
  35 /* ... with 4 registers per frame. */
  36 #define DWARF_REG_MIN_REQ       (DWARF_FRAME_MIN_REQ * 4)
  37
  38 static struct kmem_cache *dwarf_frame_cachep;
  39 static mempool_t *dwarf_frame_pool;
  40
  41 static struct kmem_cache *dwarf_reg_cachep;
  42 static mempool_t *dwarf_reg_pool;
  43
  44 static struct rb_root cie_root;
  45 static DEFINE_SPINLOCK(dwarf_cie_lock);
  46
  47 static struct rb_root fde_root;
  48 static DEFINE_SPINLOCK(dwarf_fde_lock);
  49
  50 static struct dwarf_cie *cached_cie;
  51
  52 /**
  53  *      dwarf_frame_alloc_reg - allocate memory for a DWARF register
  54  *      @frame: the DWARF frame whose list of registers we insert on
  55  *      @reg_num: the register number
  56  *
  57  *      Allocate space for, and initialise, a dwarf reg from
  58  *      dwarf_reg_pool and insert it onto the (unsorted) linked-list of
  59  *      dwarf registers for @frame.
  60  *
  61  *      Return the initialised DWARF reg.
  62  */
  63 static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
  64                                                unsigned int reg_num)
  65 {
  66         struct dwarf_reg *reg;
  67
  68         reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
  69         if (!reg) {
  70                 printk(KERN_WARNING "Unable to allocate a DWARF register\n");
  71                 /*
  72                  * Let's just bomb hard here, we have no way to
  73                  * gracefully recover.
  74                  */
  75                 UNWINDER_BUG();
  76         }
  77
  78         reg->number = reg_num;
  79         reg->addr = 0;
  80         reg->flags = 0;
  81
  82         list_add(&reg->link, &frame->reg_list);
  83
  84         return reg;
  85 }
  86
  87 static void dwarf_frame_free_regs(struct dwarf_frame *frame)
  88 {
  89         struct dwarf_reg *reg, *n;
  90
  91         list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
  92                 list_del(&reg->link);
  93                 mempool_free(reg, dwarf_reg_pool);
  94         }
  95 }
  96
  97 /**
  98  *      dwarf_frame_reg - return a DWARF register
  99  *      @frame: the DWARF frame to search in for @reg_num
 100  *      @reg_num: the register number to search for
 101  *
 102  *      Lookup and return the dwarf reg @reg_num for this frame. Return
 103  *      NULL if @reg_num is an register invalid number.
 104  */
 105 static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
 106                                          unsigned int reg_num)
 107 {
 108         struct dwarf_reg *reg;
 109
 110         list_for_each_entry(reg, &frame->reg_list, link) {
 111                 if (reg->number == reg_num)
 112                         return reg;
 113         }
 114
 115         return NULL;
 116 }
 117
 118 /**
 119  *      dwarf_read_addr - read dwarf data
 120  *      @src: source address of data
 121  *      @dst: destination address to store the data to
 122  *
 123  *      Read 'n' bytes from @src, where 'n' is the size of an address on
 124  *      the native machine. We return the number of bytes read, which
 125  *      should always be 'n'. We also have to be careful when reading
 126  *      from @src and writing to @dst, because they can be arbitrarily
 127  *      aligned. Return 'n' - the number of bytes read.
 128  */
 129 static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
 130 {
 131         u32 val = get_unaligned(src);
 132         put_unaligned(val, dst);
 133         return sizeof(unsigned long *);
 134 }
 135
 136 /**
 137  *      dwarf_read_uleb128 - read unsigned LEB128 data
 138  *      @addr: the address where the ULEB128 data is stored
 139  *      @ret: address to store the result
 140  *
 141  *      Decode an unsigned LEB128 encoded datum. The algorithm is taken
 142  *      from Appendix C of the DWARF 3 spec. For information on the
 143  *      encodings refer to section "7.6 - Variable Length Data". Return
 144  *      the number of bytes read.
 145  */
 146 static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
 147 {
 148         unsigned int result;
 149         unsigned char byte;
 150         int shift, count;
 151
 152         result = 0;
 153         shift = 0;
 154         count = 0;
 155
 156         while (1) {
 157                 byte = __raw_readb(addr);
 158                 addr++;
 159                 count++;
 160
 161                 result |= (byte & 0x7f) << shift;
 162                 shift += 7;
 163
 164                 if (!(byte & 0x80))
 165                         break;
 166         }
 167
 168         *ret = result;
 169
 170         return count;
 171 }
 172
 173 /**
 174  *      dwarf_read_leb128 - read signed LEB128 data
 175  *      @addr: the address of the LEB128 encoded data
 176  *      @ret: address to store the result
 177  *
 178  *      Decode signed LEB128 data. The algorithm is taken from Appendix
 179  *      C of the DWARF 3 spec. Return the number of bytes read.
 180  */
 181 static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
 182 {
 183         unsigned char byte;
 184         int result, shift;
 185         int num_bits;
 186         int count;
 187
 188         result = 0;
 189         shift = 0;
 190         count = 0;
 191
 192         while (1) {
 193                 byte = __raw_readb(addr);
 194                 addr++;
 195                 result |= (byte & 0x7f) << shift;
 196                 shift += 7;
 197                 count++;
 198
 199                 if (!(byte & 0x80))
 200                         break;
 201         }
 202
 203         /* The number of bits in a signed integer. */
 204         num_bits = 8 * sizeof(result);
 205
 206         if ((shift < num_bits) && (byte & 0x40))
 207                 result |= (-1 << shift);
 208
 209         *ret = result;
 210
 211         return count;
 212 }
 213
 214 /**
 215  *      dwarf_read_encoded_value - return the decoded value at @addr
 216  *      @addr: the address of the encoded value
 217  *      @val: where to write the decoded value
 218  *      @encoding: the encoding with which we can decode @addr
 219  *
 220  *      GCC emits encoded address in the .eh_frame FDE entries. Decode
 221  *      the value at @addr using @encoding. The decoded value is written
 222  *      to @val and the number of bytes read is returned.
 223  */
 224 static int dwarf_read_encoded_value(char *addr, unsigned long *val,
 225                                     char encoding)
 226 {
 227         unsigned long decoded_addr = 0;
 228         int count = 0;
 229
 230         switch (encoding & 0x70) {
 231         case DW_EH_PE_absptr:
 232                 break;
 233         case DW_EH_PE_pcrel:
 234                 decoded_addr = (unsigned long)addr;
 235                 break;
 236         default:
 237                 pr_debug("encoding=0x%x\n", (encoding & 0x70));
 238                 UNWINDER_BUG();
 239         }
 240
 241         if ((encoding & 0x07) == 0x00)
 242                 encoding |= DW_EH_PE_udata4;
 243
 244         switch (encoding & 0x0f) {
 245         case DW_EH_PE_sdata4:
 246         case DW_EH_PE_udata4:
 247                 count += 4;
 248                 decoded_addr += get_unaligned((u32 *)addr);
 249                 __raw_writel(decoded_addr, val);
 250                 break;
 251         default:
 252                 pr_debug("encoding=0x%x\n", encoding);
 253                 UNWINDER_BUG();
 254         }
 255
 256         return count;
 257 }
 258
 259 /**
 260  *      dwarf_entry_len - return the length of an FDE or CIE
 261  *      @addr: the address of the entry
 262  *      @len: the length of the entry
 263  *
 264  *      Read the initial_length field of the entry and store the size of
 265  *      the entry in @len. We return the number of bytes read. Return a
 266  *      count of 0 on error.
 267  */
 268 static inline int dwarf_entry_len(char *addr, unsigned long *len)
 269 {
 270         u32 initial_len;
 271         int count;
 272
 273         initial_len = get_unaligned((u32 *)addr);
 274         count = 4;
 275
 276         /*
 277          * An initial length field value in the range DW_LEN_EXT_LO -
 278          * DW_LEN_EXT_HI indicates an extension, and should not be
 279          * interpreted as a length. The only extension that we currently
 280          * understand is the use of DWARF64 addresses.
 281          */
 282         if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
 283                 /*
 284                  * The 64-bit length field immediately follows the
 285                  * compulsory 32-bit length field.
 286                  */
 287                 if (initial_len == DW_EXT_DWARF64) {
 288                         *len = get_unaligned((u64 *)addr + 4);
 289                         count = 12;
 290                 } else {
 291                         printk(KERN_WARNING "Unknown DWARF extension\n");
 292                         count = 0;
 293                 }
 294         } else
 295                 *len = initial_len;
 296
 297         return count;
 298 }
 299
 300 /**
 301  *      dwarf_lookup_cie - locate the cie
 302  *      @cie_ptr: pointer to help with lookup
 303  */
 304 static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
 305 {
 306         struct rb_node **rb_node = &cie_root.rb_node;
 307         struct dwarf_cie *cie = NULL;
 308         unsigned long flags;
 309
 310         spin_lock_irqsave(&dwarf_cie_lock, flags);
 311
 312         /*
 313          * We've cached the last CIE we looked up because chances are
 314          * that the FDE wants this CIE.
 315          */
 316         if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
 317                 cie = cached_cie;
 318                 goto out;
 319         }
 320
 321         while (*rb_node) {
 322                 struct dwarf_cie *cie_tmp;
 323
 324                 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
 325                 BUG_ON(!cie_tmp);
 326
 327                 if (cie_ptr == cie_tmp->cie_pointer) {
 328                         cie = cie_tmp;
 329                         cached_cie = cie_tmp;
 330                         goto out;
 331                 } else {
 332                         if (cie_ptr < cie_tmp->cie_pointer)
 333                                 rb_node = &(*rb_node)->rb_left;
 334                         else
 335                                 rb_node = &(*rb_node)->rb_right;
 336                 }
 337         }
 338
 339 out:
 340         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 341         return cie;
 342 }
 343
 344 /**
 345  *      dwarf_lookup_fde - locate the FDE that covers pc
 346  *      @pc: the program counter
 347  */
 348 struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
 349 {
 350         struct rb_node **rb_node = &fde_root.rb_node;
 351         struct dwarf_fde *fde = NULL;
 352         unsigned long flags;
 353
 354         spin_lock_irqsave(&dwarf_fde_lock, flags);
 355
 356         while (*rb_node) {
 357                 struct dwarf_fde *fde_tmp;
 358                 unsigned long tmp_start, tmp_end;
 359
 360                 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
 361                 BUG_ON(!fde_tmp);
 362
 363                 tmp_start = fde_tmp->initial_location;
 364                 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
 365
 366                 if (pc < tmp_start) {
 367                         rb_node = &(*rb_node)->rb_left;
 368                 } else {
 369                         if (pc < tmp_end) {
 370                                 fde = fde_tmp;
 371                                 goto out;
 372                         } else
 373                                 rb_node = &(*rb_node)->rb_right;
 374                 }
 375         }
 376
 377 out:
 378         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 379
 380         return fde;
 381 }
 382
 383 /**
 384  *      dwarf_cfa_execute_insns - execute instructions to calculate a CFA
 385  *      @insn_start: address of the first instruction
 386  *      @insn_end: address of the last instruction
 387  *      @cie: the CIE for this function
 388  *      @fde: the FDE for this function
 389  *      @frame: the instructions calculate the CFA for this frame
 390  *      @pc: the program counter of the address we're interested in
 391  *
 392  *      Execute the Call Frame instruction sequence starting at
 393  *      @insn_start and ending at @insn_end. The instructions describe
 394  *      how to calculate the Canonical Frame Address of a stackframe.
 395  *      Store the results in @frame.
 396  */
 397 static int dwarf_cfa_execute_insns(unsigned char *insn_start,
 398                                    unsigned char *insn_end,
 399                                    struct dwarf_cie *cie,
 400                                    struct dwarf_fde *fde,
 401                                    struct dwarf_frame *frame,
 402                                    unsigned long pc)
 403 {
 404         unsigned char insn;
 405         unsigned char *current_insn;
 406         unsigned int count, delta, reg, expr_len, offset;
 407         struct dwarf_reg *regp;
 408
 409         current_insn = insn_start;
 410
 411         while (current_insn < insn_end && frame->pc <= pc) {
 412                 insn = __raw_readb(current_insn++);
 413
 414                 /*
 415                  * Firstly, handle the opcodes that embed their operands
 416                  * in the instructions.
 417                  */
 418                 switch (DW_CFA_opcode(insn)) {
 419                 case DW_CFA_advance_loc:
 420                         delta = DW_CFA_operand(insn);
 421                         delta *= cie->code_alignment_factor;
 422                         frame->pc += delta;
 423                         continue;
 424                         /* NOTREACHED */
 425                 case DW_CFA_offset:
 426                         reg = DW_CFA_operand(insn);
 427                         count = dwarf_read_uleb128(current_insn, &offset);
 428                         current_insn += count;
 429                         offset *= cie->data_alignment_factor;
 430                         regp = dwarf_frame_alloc_reg(frame, reg);
 431                         regp->addr = offset;
 432                         regp->flags |= DWARF_REG_OFFSET;
 433                         continue;
 434                         /* NOTREACHED */
 435                 case DW_CFA_restore:
 436                         reg = DW_CFA_operand(insn);
 437                         continue;
 438                         /* NOTREACHED */
 439                 }
 440
 441                 /*
 442                  * Secondly, handle the opcodes that don't embed their
 443                  * operands in the instruction.
 444                  */
 445                 switch (insn) {
 446                 case DW_CFA_nop:
 447                         continue;
 448                 case DW_CFA_advance_loc1:
 449                         delta = *current_insn++;
 450                         frame->pc += delta * cie->code_alignment_factor;
 451                         break;
 452                 case DW_CFA_advance_loc2:
 453                         delta = get_unaligned((u16 *)current_insn);
 454                         current_insn += 2;
 455                         frame->pc += delta * cie->code_alignment_factor;
 456                         break;
 457                 case DW_CFA_advance_loc4:
 458                         delta = get_unaligned((u32 *)current_insn);
 459                         current_insn += 4;
 460                         frame->pc += delta * cie->code_alignment_factor;
 461                         break;
 462                 case DW_CFA_offset_extended:
 463                         count = dwarf_read_uleb128(current_insn, &reg);
 464                         current_insn += count;
 465                         count = dwarf_read_uleb128(current_insn, &offset);
 466                         current_insn += count;
 467                         offset *= cie->data_alignment_factor;
 468                         break;
 469                 case DW_CFA_restore_extended:
 470                         count = dwarf_read_uleb128(current_insn, &reg);
 471                         current_insn += count;
 472                         break;
 473                 case DW_CFA_undefined:
 474                         count = dwarf_read_uleb128(current_insn, &reg);
 475                         current_insn += count;
 476                         regp = dwarf_frame_alloc_reg(frame, reg);
 477                         regp->flags |= DWARF_UNDEFINED;
 478                         break;
 479                 case DW_CFA_def_cfa:
 480                         count = dwarf_read_uleb128(current_insn,
 481                                                    &frame->cfa_register);
 482                         current_insn += count;
 483                         count = dwarf_read_uleb128(current_insn,
 484                                                    &frame->cfa_offset);
 485                         current_insn += count;
 486
 487                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
 488                         break;
 489                 case DW_CFA_def_cfa_register:
 490                         count = dwarf_read_uleb128(current_insn,
 491                                                    &frame->cfa_register);
 492                         current_insn += count;
 493                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
 494                         break;
 495                 case DW_CFA_def_cfa_offset:
 496                         count = dwarf_read_uleb128(current_insn, &offset);
 497                         current_insn += count;
 498                         frame->cfa_offset = offset;
 499                         break;
 500                 case DW_CFA_def_cfa_expression:
 501                         count = dwarf_read_uleb128(current_insn, &expr_len);
 502                         current_insn += count;
 503
 504                         frame->cfa_expr = current_insn;
 505                         frame->cfa_expr_len = expr_len;
 506                         current_insn += expr_len;
 507
 508                         frame->flags |= DWARF_FRAME_CFA_REG_EXP;
 509                         break;
 510                 case DW_CFA_offset_extended_sf:
 511                         count = dwarf_read_uleb128(current_insn, &reg);
 512                         current_insn += count;
 513                         count = dwarf_read_leb128(current_insn, &offset);
 514                         current_insn += count;
 515                         offset *= cie->data_alignment_factor;
 516                         regp = dwarf_frame_alloc_reg(frame, reg);
 517                         regp->flags |= DWARF_REG_OFFSET;
 518                         regp->addr = offset;
 519                         break;
 520                 case DW_CFA_val_offset:
 521                         count = dwarf_read_uleb128(current_insn, &reg);
 522                         current_insn += count;
 523                         count = dwarf_read_leb128(current_insn, &offset);
 524                         offset *= cie->data_alignment_factor;
 525                         regp = dwarf_frame_alloc_reg(frame, reg);
 526                         regp->flags |= DWARF_VAL_OFFSET;
 527                         regp->addr = offset;
 528                         break;
 529                 case DW_CFA_GNU_args_size:
 530                         count = dwarf_read_uleb128(current_insn, &offset);
 531                         current_insn += count;
 532                         break;
 533                 case DW_CFA_GNU_negative_offset_extended:
 534                         count = dwarf_read_uleb128(current_insn, &reg);
 535                         current_insn += count;
 536                         count = dwarf_read_uleb128(current_insn, &offset);
 537                         offset *= cie->data_alignment_factor;
 538
 539                         regp = dwarf_frame_alloc_reg(frame, reg);
 540                         regp->flags |= DWARF_REG_OFFSET;
 541                         regp->addr = -offset;
 542                         break;
 543                 default:
 544                         pr_debug("unhandled DWARF instruction 0x%x\n", insn);
 545                         UNWINDER_BUG();
 546                         break;
 547                 }
 548         }
 549
 550         return 0;
 551 }
 552
 553 /**
 554  *      dwarf_free_frame - free the memory allocated for @frame
 555  *      @frame: the frame to free
 556  */
 557 void dwarf_free_frame(struct dwarf_frame *frame)
 558 {
 559         dwarf_frame_free_regs(frame);
 560         mempool_free(frame, dwarf_frame_pool);
 561 }
 562
 563 extern void ret_from_irq(void);
 564
 565 /**
 566  *      dwarf_unwind_stack - unwind the stack
 567  *
 568  *      @pc: address of the function to unwind
 569  *      @prev: struct dwarf_frame of the previous stackframe on the callstack
 570  *
 571  *      Return a struct dwarf_frame representing the most recent frame
 572  *      on the callstack. Each of the lower (older) stack frames are
 573  *      linked via the "prev" member.
 574  */
 575 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
 576                                        struct dwarf_frame *prev)
 577 {
 578         struct dwarf_frame *frame;
 579         struct dwarf_cie *cie;
 580         struct dwarf_fde *fde;
 581         struct dwarf_reg *reg;
 582         unsigned long addr;
 583
 584         /*
 585          * If we're starting at the top of the stack we need get the
 586          * contents of a physical register to get the CFA in order to
 587          * begin the virtual unwinding of the stack.
 588          *
 589          * NOTE: the return address is guaranteed to be setup by the
 590          * time this function makes its first function call.
 591          */
 592         if (!pc || !prev)
 593                 pc = (unsigned long)current_text_addr();
 594
 595 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 596         /*
 597          * If our stack has been patched by the function graph tracer
 598          * then we might see the address of return_to_handler() where we
 599          * expected to find the real return address.
 600          */
 601         if (pc == (unsigned long)&return_to_handler) {
 602                 int index = current->curr_ret_stack;
 603
 604                 /*
 605                  * We currently have no way of tracking how many
 606                  * return_to_handler()'s we've seen. If there is more
 607                  * than one patched return address on our stack,
 608                  * complain loudly.
 609                  */
 610                 WARN_ON(index > 0);
 611
 612                 pc = current->ret_stack[index].ret;
 613         }
 614 #endif
 615
 616         frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
 617         if (!frame) {
 618                 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
 619                 UNWINDER_BUG();
 620         }
 621
 622         INIT_LIST_HEAD(&frame->reg_list);
 623         frame->flags = 0;
 624         frame->prev = prev;
 625         frame->return_addr = 0;
 626
 627         fde = dwarf_lookup_fde(pc);
 628         if (!fde) {
 629                 /*
 630                  * This is our normal exit path. There are two reasons
 631                  * why we might exit here,
 632                  *
 633                  *      a) pc has no asscociated DWARF frame info and so
 634                  *      we don't know how to unwind this frame. This is
 635                  *      usually the case when we're trying to unwind a
 636                  *      frame that was called from some assembly code
 637                  *      that has no DWARF info, e.g. syscalls.
 638                  *
 639                  *      b) the DEBUG info for pc is bogus. There's
 640                  *      really no way to distinguish this case from the
 641                  *      case above, which sucks because we could print a
 642                  *      warning here.
 643                  */
 644                 goto bail;
 645         }
 646
 647         cie = dwarf_lookup_cie(fde->cie_pointer);
 648
 649         frame->pc = fde->initial_location;
 650
 651         /* CIE initial instructions */
 652         dwarf_cfa_execute_insns(cie->initial_instructions,
 653                                 cie->instructions_end, cie, fde,
 654                                 frame, pc);
 655
 656         /* FDE instructions */
 657         dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
 658                                 fde, frame, pc);
 659
 660         /* Calculate the CFA */
 661         switch (frame->flags) {
 662         case DWARF_FRAME_CFA_REG_OFFSET:
 663                 if (prev) {
 664                         reg = dwarf_frame_reg(prev, frame->cfa_register);
 665                         UNWINDER_BUG_ON(!reg);
 666                         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 667
 668                         addr = prev->cfa + reg->addr;
 669                         frame->cfa = __raw_readl(addr);
 670
 671                 } else {
 672                         /*
 673                          * Again, we're starting from the top of the
 674                          * stack. We need to physically read
 675                          * the contents of a register in order to get
 676                          * the Canonical Frame Address for this
 677                          * function.
 678                          */
 679                         frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
 680                 }
 681
 682                 frame->cfa += frame->cfa_offset;
 683                 break;
 684         default:
 685                 UNWINDER_BUG();
 686         }
 687
 688         reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
 689
 690         /*
 691          * If we haven't seen the return address register or the return
 692          * address column is undefined then we must assume that this is
 693          * the end of the callstack.
 694          */
 695         if (!reg || reg->flags == DWARF_UNDEFINED)
 696                 goto bail;
 697
 698         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 699
 700         addr = frame->cfa + reg->addr;
 701         frame->return_addr = __raw_readl(addr);
 702
 703         /*
 704          * Ah, the joys of unwinding through interrupts.
 705          *
 706          * Interrupts are tricky - the DWARF info needs to be _really_
 707          * accurate and unfortunately I'm seeing a lot of bogus DWARF
 708          * info. For example, I've seen interrupts occur in epilogues
 709          * just after the frame pointer (r14) had been restored. The
 710          * problem was that the DWARF info claimed that the CFA could be
 711          * reached by using the value of the frame pointer before it was
 712          * restored.
 713          *
 714          * So until the compiler can be trusted to produce reliable
 715          * DWARF info when it really matters, let's stop unwinding once
 716          * we've calculated the function that was interrupted.
 717          */
 718         if (prev && prev->pc == (unsigned long)ret_from_irq)
 719                 frame->return_addr = 0;
 720
 721         return frame;
 722
 723 bail:
 724         dwarf_free_frame(frame);
 725         return NULL;
 726 }
 727
 728 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
 729                            unsigned char *end, struct module *mod)
 730 {
 731         struct rb_node **rb_node = &cie_root.rb_node;
 732         struct rb_node *parent = *rb_node;
 733         struct dwarf_cie *cie;
 734         unsigned long flags;
 735         int count;
 736
 737         cie = kzalloc(sizeof(*cie), GFP_KERNEL);
 738         if (!cie)
 739                 return -ENOMEM;
 740
 741         cie->length = len;
 742
 743         /*
 744          * Record the offset into the .eh_frame section
 745          * for this CIE. It allows this CIE to be
 746          * quickly and easily looked up from the
 747          * corresponding FDE.
 748          */
 749         cie->cie_pointer = (unsigned long)entry;
 750
 751         cie->version = *(char *)p++;
 752         UNWINDER_BUG_ON(cie->version != 1);
 753
 754         cie->augmentation = p;
 755         p += strlen(cie->augmentation) + 1;
 756
 757         count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
 758         p += count;
 759
 760         count = dwarf_read_leb128(p, &cie->data_alignment_factor);
 761         p += count;
 762
 763         /*
 764          * Which column in the rule table contains the
 765          * return address?
 766          */
 767         if (cie->version == 1) {
 768                 cie->return_address_reg = __raw_readb(p);
 769                 p++;
 770         } else {
 771                 count = dwarf_read_uleb128(p, &cie->return_address_reg);
 772                 p += count;
 773         }
 774
 775         if (cie->augmentation[0] == 'z') {
 776                 unsigned int length, count;
 777                 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
 778
 779                 count = dwarf_read_uleb128(p, &length);
 780                 p += count;
 781
 782                 UNWINDER_BUG_ON((unsigned char *)p > end);
 783
 784                 cie->initial_instructions = p + length;
 785                 cie->augmentation++;
 786         }
 787
 788         while (*cie->augmentation) {
 789                 /*
 790                  * "L" indicates a byte showing how the
 791                  * LSDA pointer is encoded. Skip it.
 792                  */
 793                 if (*cie->augmentation == 'L') {
 794                         p++;
 795                         cie->augmentation++;
 796                 } else if (*cie->augmentation == 'R') {
 797                         /*
 798                          * "R" indicates a byte showing
 799                          * how FDE addresses are
 800                          * encoded.
 801                          */
 802                         cie->encoding = *(char *)p++;
 803                         cie->augmentation++;
 804                 } else if (*cie->augmentation == 'P') {
 805                         /*
 806                          * "R" indicates a personality
 807                          * routine in the CIE
 808                          * augmentation.
 809                          */
 810                         UNWINDER_BUG();
 811                 } else if (*cie->augmentation == 'S') {
 812                         UNWINDER_BUG();
 813                 } else {
 814                         /*
 815                          * Unknown augmentation. Assume
 816                          * 'z' augmentation.
 817                          */
 818                         p = cie->initial_instructions;
 819                         UNWINDER_BUG_ON(!p);
 820                         break;
 821                 }
 822         }
 823
 824         cie->initial_instructions = p;
 825         cie->instructions_end = end;
 826
 827         /* Add to list */
 828         spin_lock_irqsave(&dwarf_cie_lock, flags);
 829
 830         while (*rb_node) {
 831                 struct dwarf_cie *cie_tmp;
 832
 833                 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
 834
 835                 parent = *rb_node;
 836
 837                 if (cie->cie_pointer < cie_tmp->cie_pointer)
 838                         rb_node = &parent->rb_left;
 839                 else if (cie->cie_pointer >= cie_tmp->cie_pointer)
 840                         rb_node = &parent->rb_right;
 841                 else
 842                         WARN_ON(1);
 843         }
 844
 845         rb_link_node(&cie->node, parent, rb_node);
 846         rb_insert_color(&cie->node, &cie_root);
 847
 848         if (mod != NULL)
 849                 list_add_tail(&cie->link, &mod->arch.cie_list);
 850
 851         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 852
 853         return 0;
 854 }
 855
 856 static int dwarf_parse_fde(void *entry, u32 entry_type,
 857                            void *start, unsigned long len,
 858                            unsigned char *end, struct module *mod)
 859 {
 860         struct rb_node **rb_node = &fde_root.rb_node;
 861         struct rb_node *parent = *rb_node;
 862         struct dwarf_fde *fde;
 863         struct dwarf_cie *cie;
 864         unsigned long flags;
 865         int count;
 866         void *p = start;
 867
 868         fde = kzalloc(sizeof(*fde), GFP_KERNEL);
 869         if (!fde)
 870                 return -ENOMEM;
 871
 872         fde->length = len;
 873
 874         /*
 875          * In a .eh_frame section the CIE pointer is the
 876          * delta between the address within the FDE
 877          */
 878         fde->cie_pointer = (unsigned long)(p - entry_type - 4);
 879
 880         cie = dwarf_lookup_cie(fde->cie_pointer);
 881         fde->cie = cie;
 882
 883         if (cie->encoding)
 884                 count = dwarf_read_encoded_value(p, &fde->initial_location,
 885                                                  cie->encoding);
 886         else
 887                 count = dwarf_read_addr(p, &fde->initial_location);
 888
 889         p += count;
 890
 891         if (cie->encoding)
 892                 count = dwarf_read_encoded_value(p, &fde->address_range,
 893                                                  cie->encoding & 0x0f);
 894         else
 895                 count = dwarf_read_addr(p, &fde->address_range);
 896
 897         p += count;
 898
 899         if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
 900                 unsigned int length;
 901                 count = dwarf_read_uleb128(p, &length);
 902                 p += count + length;
 903         }
 904
 905         /* Call frame instructions. */
 906         fde->instructions = p;
 907         fde->end = end;
 908
 909         /* Add to list. */
 910         spin_lock_irqsave(&dwarf_fde_lock, flags);
 911
 912         while (*rb_node) {
 913                 struct dwarf_fde *fde_tmp;
 914                 unsigned long tmp_start, tmp_end;
 915                 unsigned long start, end;
 916
 917                 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
 918
 919                 start = fde->initial_location;
 920                 end = fde->initial_location + fde->address_range;
 921
 922                 tmp_start = fde_tmp->initial_location;
 923                 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
 924
 925                 parent = *rb_node;
 926
 927                 if (start < tmp_start)
 928                         rb_node = &parent->rb_left;
 929                 else if (start >= tmp_end)
 930                         rb_node = &parent->rb_right;
 931                 else
 932                         WARN_ON(1);
 933         }
 934
 935         rb_link_node(&fde->node, parent, rb_node);
 936         rb_insert_color(&fde->node, &fde_root);
 937
 938         if (mod != NULL)
 939                 list_add_tail(&fde->link, &mod->arch.fde_list);
 940
 941         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 942
 943         return 0;
 944 }
 945
 946 static void dwarf_unwinder_dump(struct task_struct *task,
 947                                 struct pt_regs *regs,
 948                                 unsigned long *sp,
 949                                 const struct stacktrace_ops *ops,
 950                                 void *data)
 951 {
 952         struct dwarf_frame *frame, *_frame;
 953         unsigned long return_addr;
 954
 955         _frame = NULL;
 956         return_addr = 0;
 957
 958         while (1) {
 959                 frame = dwarf_unwind_stack(return_addr, _frame);
 960
 961                 if (_frame)
 962                         dwarf_free_frame(_frame);
 963
 964                 _frame = frame;
 965
 966                 if (!frame || !frame->return_addr)
 967                         break;
 968
 969                 return_addr = frame->return_addr;
 970                 ops->address(data, return_addr, 1);
 971         }
 972
 973         if (frame)
 974                 dwarf_free_frame(frame);
 975 }
 976
 977 static struct unwinder dwarf_unwinder = {
 978         .name = "dwarf-unwinder",
 979         .dump = dwarf_unwinder_dump,
 980         .rating = 150,
 981 };
 982
 983 static void dwarf_unwinder_cleanup(void)
 984 {
 985         struct rb_node **fde_rb_node = &fde_root.rb_node;
 986         struct rb_node **cie_rb_node = &cie_root.rb_node;
 987
 988         /*
 989          * Deallocate all the memory allocated for the DWARF unwinder.
 990          * Traverse all the FDE/CIE lists and remove and free all the
 991          * memory associated with those data structures.
 992          */
 993         while (*fde_rb_node) {
 994                 struct dwarf_fde *fde;
 995
 996                 fde = rb_entry(*fde_rb_node, struct dwarf_fde, node);
 997                 rb_erase(*fde_rb_node, &fde_root);
 998                 kfree(fde);
 999         }
1000
1001         while (*cie_rb_node) {
1002                 struct dwarf_cie *cie;
1003
1004                 cie = rb_entry(*cie_rb_node, struct dwarf_cie, node);
1005                 rb_erase(*cie_rb_node, &cie_root);
1006                 kfree(cie);
1007         }
1008
1009         kmem_cache_destroy(dwarf_reg_cachep);
1010         kmem_cache_destroy(dwarf_frame_cachep);
1011 }
1012
1013 /**
1014  *      dwarf_parse_section - parse DWARF section
1015  *      @eh_frame_start: start address of the .eh_frame section
1016  *      @eh_frame_end: end address of the .eh_frame section
1017  *      @mod: the kernel module containing the .eh_frame section
1018  *
1019  *      Parse the information in a .eh_frame section.
1020  */
1021 static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1022                                struct module *mod)
1023 {
1024         u32 entry_type;
1025         void *p, *entry;
1026         int count, err = 0;
1027         unsigned long len = 0;
1028         unsigned int c_entries, f_entries;
1029         unsigned char *end;
1030
1031         c_entries = 0;
1032         f_entries = 0;
1033         entry = eh_frame_start;
1034
1035         while ((char *)entry < eh_frame_end) {
1036                 p = entry;
1037
1038                 count = dwarf_entry_len(p, &len);
1039                 if (count == 0) {
1040                         /*
1041                          * We read a bogus length field value. There is
1042                          * nothing we can do here apart from disabling
1043                          * the DWARF unwinder. We can't even skip this
1044                          * entry and move to the next one because 'len'
1045                          * tells us where our next entry is.
1046                          */
1047                         err = -EINVAL;
1048                         goto out;
1049                 } else
1050                         p += count;
1051
1052                 /* initial length does not include itself */
1053                 end = p + len;
1054
1055                 entry_type = get_unaligned((u32 *)p);
1056                 p += 4;
1057
1058                 if (entry_type == DW_EH_FRAME_CIE) {
1059                         err = dwarf_parse_cie(entry, p, len, end, mod);
1060                         if (err < 0)
1061                                 goto out;
1062                         else
1063                                 c_entries++;
1064                 } else {
1065                         err = dwarf_parse_fde(entry, entry_type, p, len,
1066                                               end, mod);
1067                         if (err < 0)
1068                                 goto out;
1069                         else
1070                                 f_entries++;
1071                 }
1072
1073                 entry = (char *)entry + len + 4;
1074         }
1075
1076         printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1077                c_entries, f_entries);
1078
1079         return 0;
1080
1081 out:
1082         return err;
1083 }
1084
1085 #ifdef CONFIG_MODULES
1086 int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1087                           struct module *me)
1088 {
1089         unsigned int i, err;
1090         unsigned long start, end;
1091         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
1092
1093         start = end = 0;
1094
1095         for (i = 1; i < hdr->e_shnum; i++) {
1096                 /* Alloc bit cleared means "ignore it." */
1097                 if ((sechdrs[i].sh_flags & SHF_ALLOC)
1098                     && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
1099                         start = sechdrs[i].sh_addr;
1100                         end = start + sechdrs[i].sh_size;
1101                         break;
1102                 }
1103         }
1104
1105         /* Did we find the .eh_frame section? */
1106         if (i != hdr->e_shnum) {
1107                 INIT_LIST_HEAD(&me->arch.cie_list);
1108                 INIT_LIST_HEAD(&me->arch.fde_list);
1109                 err = dwarf_parse_section((char *)start, (char *)end, me);
1110                 if (err) {
1111                         printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1112                                me->name);
1113                         return err;
1114                 }
1115         }
1116
1117         return 0;
1118 }
1119
1120 /**
1121  *      module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1122  *      @mod: the module that is being unloaded
1123  *
1124  *      Remove any FDEs and CIEs from the global lists that came from
1125  *      @mod's .eh_frame section because @mod is being unloaded.
1126  */
1127 void module_dwarf_cleanup(struct module *mod)
1128 {
1129         struct dwarf_fde *fde, *ftmp;
1130         struct dwarf_cie *cie, *ctmp;
1131         unsigned long flags;
1132
1133         spin_lock_irqsave(&dwarf_cie_lock, flags);
1134
1135         list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
1136                 list_del(&cie->link);
1137                 rb_erase(&cie->node, &cie_root);
1138                 kfree(cie);
1139         }
1140
1141         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1142
1143         spin_lock_irqsave(&dwarf_fde_lock, flags);
1144
1145         list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
1146                 list_del(&fde->link);
1147                 rb_erase(&fde->node, &fde_root);
1148                 kfree(fde);
1149         }
1150
1151         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1152 }
1153 #endif /* CONFIG_MODULES */
1154
1155 /**
1156  *      dwarf_unwinder_init - initialise the dwarf unwinder
1157  *
1158  *      Build the data structures describing the .dwarf_frame section to
1159  *      make it easier to lookup CIE and FDE entries. Because the
1160  *      .eh_frame section is packed as tightly as possible it is not
1161  *      easy to lookup the FDE for a given PC, so we build a list of FDE
1162  *      and CIE entries that make it easier.
1163  */
1164 static int __init dwarf_unwinder_init(void)
1165 {
1166         int err;
1167
1168         dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1169                         sizeof(struct dwarf_frame), 0,
1170                         SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1171
1172         dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1173                         sizeof(struct dwarf_reg), 0,
1174                         SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1175
1176         dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
1177                                           mempool_alloc_slab,
1178                                           mempool_free_slab,
1179                                           dwarf_frame_cachep);
1180
1181         dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
1182                                          mempool_alloc_slab,
1183                                          mempool_free_slab,
1184                                          dwarf_reg_cachep);
1185
1186         err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1187         if (err)
1188                 goto out;
1189
1190         err = unwinder_register(&dwarf_unwinder);
1191         if (err)
1192                 goto out;
1193
1194         return 0;
1195
1196 out:
1197         printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1198         dwarf_unwinder_cleanup();
1199         return -EINVAL;
1200 }
1201 early_initcall(dwarf_unwinder_init);