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/arch/sh/kernel/dwarf.c

https://gitlab.com/teobaluta/opw
C | 1210 lines | 731 code | 186 blank | 293 comment | 111 complexity | 16bd7af685a89c69045bcfcb05b6baf2 MD5 | raw file
   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
  38static struct kmem_cache *dwarf_frame_cachep;
  39static mempool_t *dwarf_frame_pool;
  40
  41static struct kmem_cache *dwarf_reg_cachep;
  42static mempool_t *dwarf_reg_pool;
  43
  44static struct rb_root cie_root;
  45static DEFINE_SPINLOCK(dwarf_cie_lock);
  46
  47static struct rb_root fde_root;
  48static DEFINE_SPINLOCK(dwarf_fde_lock);
  49
  50static struct dwarf_cie *cached_cie;
  51
  52static unsigned int dwarf_unwinder_ready;
  53
  54/**
  55 *	dwarf_frame_alloc_reg - allocate memory for a DWARF register
  56 *	@frame: the DWARF frame whose list of registers we insert on
  57 *	@reg_num: the register number
  58 *
  59 *	Allocate space for, and initialise, a dwarf reg from
  60 *	dwarf_reg_pool and insert it onto the (unsorted) linked-list of
  61 *	dwarf registers for @frame.
  62 *
  63 *	Return the initialised DWARF reg.
  64 */
  65static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
  66					       unsigned int reg_num)
  67{
  68	struct dwarf_reg *reg;
  69
  70	reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
  71	if (!reg) {
  72		printk(KERN_WARNING "Unable to allocate a DWARF register\n");
  73		/*
  74		 * Let's just bomb hard here, we have no way to
  75		 * gracefully recover.
  76		 */
  77		UNWINDER_BUG();
  78	}
  79
  80	reg->number = reg_num;
  81	reg->addr = 0;
  82	reg->flags = 0;
  83
  84	list_add(&reg->link, &frame->reg_list);
  85
  86	return reg;
  87}
  88
  89static void dwarf_frame_free_regs(struct dwarf_frame *frame)
  90{
  91	struct dwarf_reg *reg, *n;
  92
  93	list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
  94		list_del(&reg->link);
  95		mempool_free(reg, dwarf_reg_pool);
  96	}
  97}
  98
  99/**
 100 *	dwarf_frame_reg - return a DWARF register
 101 *	@frame: the DWARF frame to search in for @reg_num
 102 *	@reg_num: the register number to search for
 103 *
 104 *	Lookup and return the dwarf reg @reg_num for this frame. Return
 105 *	NULL if @reg_num is an register invalid number.
 106 */
 107static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
 108					 unsigned int reg_num)
 109{
 110	struct dwarf_reg *reg;
 111
 112	list_for_each_entry(reg, &frame->reg_list, link) {
 113		if (reg->number == reg_num)
 114			return reg;
 115	}
 116
 117	return NULL;
 118}
 119
 120/**
 121 *	dwarf_read_addr - read dwarf data
 122 *	@src: source address of data
 123 *	@dst: destination address to store the data to
 124 *
 125 *	Read 'n' bytes from @src, where 'n' is the size of an address on
 126 *	the native machine. We return the number of bytes read, which
 127 *	should always be 'n'. We also have to be careful when reading
 128 *	from @src and writing to @dst, because they can be arbitrarily
 129 *	aligned. Return 'n' - the number of bytes read.
 130 */
 131static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
 132{
 133	u32 val = get_unaligned(src);
 134	put_unaligned(val, dst);
 135	return sizeof(unsigned long *);
 136}
 137
 138/**
 139 *	dwarf_read_uleb128 - read unsigned LEB128 data
 140 *	@addr: the address where the ULEB128 data is stored
 141 *	@ret: address to store the result
 142 *
 143 *	Decode an unsigned LEB128 encoded datum. The algorithm is taken
 144 *	from Appendix C of the DWARF 3 spec. For information on the
 145 *	encodings refer to section "7.6 - Variable Length Data". Return
 146 *	the number of bytes read.
 147 */
 148static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
 149{
 150	unsigned int result;
 151	unsigned char byte;
 152	int shift, count;
 153
 154	result = 0;
 155	shift = 0;
 156	count = 0;
 157
 158	while (1) {
 159		byte = __raw_readb(addr);
 160		addr++;
 161		count++;
 162
 163		result |= (byte & 0x7f) << shift;
 164		shift += 7;
 165
 166		if (!(byte & 0x80))
 167			break;
 168	}
 169
 170	*ret = result;
 171
 172	return count;
 173}
 174
 175/**
 176 *	dwarf_read_leb128 - read signed LEB128 data
 177 *	@addr: the address of the LEB128 encoded data
 178 *	@ret: address to store the result
 179 *
 180 *	Decode signed LEB128 data. The algorithm is taken from Appendix
 181 *	C of the DWARF 3 spec. Return the number of bytes read.
 182 */
 183static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
 184{
 185	unsigned char byte;
 186	int result, shift;
 187	int num_bits;
 188	int count;
 189
 190	result = 0;
 191	shift = 0;
 192	count = 0;
 193
 194	while (1) {
 195		byte = __raw_readb(addr);
 196		addr++;
 197		result |= (byte & 0x7f) << shift;
 198		shift += 7;
 199		count++;
 200
 201		if (!(byte & 0x80))
 202			break;
 203	}
 204
 205	/* The number of bits in a signed integer. */
 206	num_bits = 8 * sizeof(result);
 207
 208	if ((shift < num_bits) && (byte & 0x40))
 209		result |= (-1 << shift);
 210
 211	*ret = result;
 212
 213	return count;
 214}
 215
 216/**
 217 *	dwarf_read_encoded_value - return the decoded value at @addr
 218 *	@addr: the address of the encoded value
 219 *	@val: where to write the decoded value
 220 *	@encoding: the encoding with which we can decode @addr
 221 *
 222 *	GCC emits encoded address in the .eh_frame FDE entries. Decode
 223 *	the value at @addr using @encoding. The decoded value is written
 224 *	to @val and the number of bytes read is returned.
 225 */
 226static int dwarf_read_encoded_value(char *addr, unsigned long *val,
 227				    char encoding)
 228{
 229	unsigned long decoded_addr = 0;
 230	int count = 0;
 231
 232	switch (encoding & 0x70) {
 233	case DW_EH_PE_absptr:
 234		break;
 235	case DW_EH_PE_pcrel:
 236		decoded_addr = (unsigned long)addr;
 237		break;
 238	default:
 239		pr_debug("encoding=0x%x\n", (encoding & 0x70));
 240		UNWINDER_BUG();
 241	}
 242
 243	if ((encoding & 0x07) == 0x00)
 244		encoding |= DW_EH_PE_udata4;
 245
 246	switch (encoding & 0x0f) {
 247	case DW_EH_PE_sdata4:
 248	case DW_EH_PE_udata4:
 249		count += 4;
 250		decoded_addr += get_unaligned((u32 *)addr);
 251		__raw_writel(decoded_addr, val);
 252		break;
 253	default:
 254		pr_debug("encoding=0x%x\n", encoding);
 255		UNWINDER_BUG();
 256	}
 257
 258	return count;
 259}
 260
 261/**
 262 *	dwarf_entry_len - return the length of an FDE or CIE
 263 *	@addr: the address of the entry
 264 *	@len: the length of the entry
 265 *
 266 *	Read the initial_length field of the entry and store the size of
 267 *	the entry in @len. We return the number of bytes read. Return a
 268 *	count of 0 on error.
 269 */
 270static inline int dwarf_entry_len(char *addr, unsigned long *len)
 271{
 272	u32 initial_len;
 273	int count;
 274
 275	initial_len = get_unaligned((u32 *)addr);
 276	count = 4;
 277
 278	/*
 279	 * An initial length field value in the range DW_LEN_EXT_LO -
 280	 * DW_LEN_EXT_HI indicates an extension, and should not be
 281	 * interpreted as a length. The only extension that we currently
 282	 * understand is the use of DWARF64 addresses.
 283	 */
 284	if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
 285		/*
 286		 * The 64-bit length field immediately follows the
 287		 * compulsory 32-bit length field.
 288		 */
 289		if (initial_len == DW_EXT_DWARF64) {
 290			*len = get_unaligned((u64 *)addr + 4);
 291			count = 12;
 292		} else {
 293			printk(KERN_WARNING "Unknown DWARF extension\n");
 294			count = 0;
 295		}
 296	} else
 297		*len = initial_len;
 298
 299	return count;
 300}
 301
 302/**
 303 *	dwarf_lookup_cie - locate the cie
 304 *	@cie_ptr: pointer to help with lookup
 305 */
 306static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
 307{
 308	struct rb_node **rb_node = &cie_root.rb_node;
 309	struct dwarf_cie *cie = NULL;
 310	unsigned long flags;
 311
 312	spin_lock_irqsave(&dwarf_cie_lock, flags);
 313
 314	/*
 315	 * We've cached the last CIE we looked up because chances are
 316	 * that the FDE wants this CIE.
 317	 */
 318	if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
 319		cie = cached_cie;
 320		goto out;
 321	}
 322
 323	while (*rb_node) {
 324		struct dwarf_cie *cie_tmp;
 325
 326		cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
 327		BUG_ON(!cie_tmp);
 328
 329		if (cie_ptr == cie_tmp->cie_pointer) {
 330			cie = cie_tmp;
 331			cached_cie = cie_tmp;
 332			goto out;
 333		} else {
 334			if (cie_ptr < cie_tmp->cie_pointer)
 335				rb_node = &(*rb_node)->rb_left;
 336			else
 337				rb_node = &(*rb_node)->rb_right;
 338		}
 339	}
 340
 341out:
 342	spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 343	return cie;
 344}
 345
 346/**
 347 *	dwarf_lookup_fde - locate the FDE that covers pc
 348 *	@pc: the program counter
 349 */
 350struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
 351{
 352	struct rb_node **rb_node = &fde_root.rb_node;
 353	struct dwarf_fde *fde = NULL;
 354	unsigned long flags;
 355
 356	spin_lock_irqsave(&dwarf_fde_lock, flags);
 357
 358	while (*rb_node) {
 359		struct dwarf_fde *fde_tmp;
 360		unsigned long tmp_start, tmp_end;
 361
 362		fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
 363		BUG_ON(!fde_tmp);
 364
 365		tmp_start = fde_tmp->initial_location;
 366		tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
 367
 368		if (pc < tmp_start) {
 369			rb_node = &(*rb_node)->rb_left;
 370		} else {
 371			if (pc < tmp_end) {
 372				fde = fde_tmp;
 373				goto out;
 374			} else
 375				rb_node = &(*rb_node)->rb_right;
 376		}
 377	}
 378
 379out:
 380	spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 381
 382	return fde;
 383}
 384
 385/**
 386 *	dwarf_cfa_execute_insns - execute instructions to calculate a CFA
 387 *	@insn_start: address of the first instruction
 388 *	@insn_end: address of the last instruction
 389 *	@cie: the CIE for this function
 390 *	@fde: the FDE for this function
 391 *	@frame: the instructions calculate the CFA for this frame
 392 *	@pc: the program counter of the address we're interested in
 393 *
 394 *	Execute the Call Frame instruction sequence starting at
 395 *	@insn_start and ending at @insn_end. The instructions describe
 396 *	how to calculate the Canonical Frame Address of a stackframe.
 397 *	Store the results in @frame.
 398 */
 399static int dwarf_cfa_execute_insns(unsigned char *insn_start,
 400				   unsigned char *insn_end,
 401				   struct dwarf_cie *cie,
 402				   struct dwarf_fde *fde,
 403				   struct dwarf_frame *frame,
 404				   unsigned long pc)
 405{
 406	unsigned char insn;
 407	unsigned char *current_insn;
 408	unsigned int count, delta, reg, expr_len, offset;
 409	struct dwarf_reg *regp;
 410
 411	current_insn = insn_start;
 412
 413	while (current_insn < insn_end && frame->pc <= pc) {
 414		insn = __raw_readb(current_insn++);
 415
 416		/*
 417		 * Firstly, handle the opcodes that embed their operands
 418		 * in the instructions.
 419		 */
 420		switch (DW_CFA_opcode(insn)) {
 421		case DW_CFA_advance_loc:
 422			delta = DW_CFA_operand(insn);
 423			delta *= cie->code_alignment_factor;
 424			frame->pc += delta;
 425			continue;
 426			/* NOTREACHED */
 427		case DW_CFA_offset:
 428			reg = DW_CFA_operand(insn);
 429			count = dwarf_read_uleb128(current_insn, &offset);
 430			current_insn += count;
 431			offset *= cie->data_alignment_factor;
 432			regp = dwarf_frame_alloc_reg(frame, reg);
 433			regp->addr = offset;
 434			regp->flags |= DWARF_REG_OFFSET;
 435			continue;
 436			/* NOTREACHED */
 437		case DW_CFA_restore:
 438			reg = DW_CFA_operand(insn);
 439			continue;
 440			/* NOTREACHED */
 441		}
 442
 443		/*
 444		 * Secondly, handle the opcodes that don't embed their
 445		 * operands in the instruction.
 446		 */
 447		switch (insn) {
 448		case DW_CFA_nop:
 449			continue;
 450		case DW_CFA_advance_loc1:
 451			delta = *current_insn++;
 452			frame->pc += delta * cie->code_alignment_factor;
 453			break;
 454		case DW_CFA_advance_loc2:
 455			delta = get_unaligned((u16 *)current_insn);
 456			current_insn += 2;
 457			frame->pc += delta * cie->code_alignment_factor;
 458			break;
 459		case DW_CFA_advance_loc4:
 460			delta = get_unaligned((u32 *)current_insn);
 461			current_insn += 4;
 462			frame->pc += delta * cie->code_alignment_factor;
 463			break;
 464		case DW_CFA_offset_extended:
 465			count = dwarf_read_uleb128(current_insn, &reg);
 466			current_insn += count;
 467			count = dwarf_read_uleb128(current_insn, &offset);
 468			current_insn += count;
 469			offset *= cie->data_alignment_factor;
 470			break;
 471		case DW_CFA_restore_extended:
 472			count = dwarf_read_uleb128(current_insn, &reg);
 473			current_insn += count;
 474			break;
 475		case DW_CFA_undefined:
 476			count = dwarf_read_uleb128(current_insn, &reg);
 477			current_insn += count;
 478			regp = dwarf_frame_alloc_reg(frame, reg);
 479			regp->flags |= DWARF_UNDEFINED;
 480			break;
 481		case DW_CFA_def_cfa:
 482			count = dwarf_read_uleb128(current_insn,
 483						   &frame->cfa_register);
 484			current_insn += count;
 485			count = dwarf_read_uleb128(current_insn,
 486						   &frame->cfa_offset);
 487			current_insn += count;
 488
 489			frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
 490			break;
 491		case DW_CFA_def_cfa_register:
 492			count = dwarf_read_uleb128(current_insn,
 493						   &frame->cfa_register);
 494			current_insn += count;
 495			frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
 496			break;
 497		case DW_CFA_def_cfa_offset:
 498			count = dwarf_read_uleb128(current_insn, &offset);
 499			current_insn += count;
 500			frame->cfa_offset = offset;
 501			break;
 502		case DW_CFA_def_cfa_expression:
 503			count = dwarf_read_uleb128(current_insn, &expr_len);
 504			current_insn += count;
 505
 506			frame->cfa_expr = current_insn;
 507			frame->cfa_expr_len = expr_len;
 508			current_insn += expr_len;
 509
 510			frame->flags |= DWARF_FRAME_CFA_REG_EXP;
 511			break;
 512		case DW_CFA_offset_extended_sf:
 513			count = dwarf_read_uleb128(current_insn, &reg);
 514			current_insn += count;
 515			count = dwarf_read_leb128(current_insn, &offset);
 516			current_insn += count;
 517			offset *= cie->data_alignment_factor;
 518			regp = dwarf_frame_alloc_reg(frame, reg);
 519			regp->flags |= DWARF_REG_OFFSET;
 520			regp->addr = offset;
 521			break;
 522		case DW_CFA_val_offset:
 523			count = dwarf_read_uleb128(current_insn, &reg);
 524			current_insn += count;
 525			count = dwarf_read_leb128(current_insn, &offset);
 526			offset *= cie->data_alignment_factor;
 527			regp = dwarf_frame_alloc_reg(frame, reg);
 528			regp->flags |= DWARF_VAL_OFFSET;
 529			regp->addr = offset;
 530			break;
 531		case DW_CFA_GNU_args_size:
 532			count = dwarf_read_uleb128(current_insn, &offset);
 533			current_insn += count;
 534			break;
 535		case DW_CFA_GNU_negative_offset_extended:
 536			count = dwarf_read_uleb128(current_insn, &reg);
 537			current_insn += count;
 538			count = dwarf_read_uleb128(current_insn, &offset);
 539			offset *= cie->data_alignment_factor;
 540
 541			regp = dwarf_frame_alloc_reg(frame, reg);
 542			regp->flags |= DWARF_REG_OFFSET;
 543			regp->addr = -offset;
 544			break;
 545		default:
 546			pr_debug("unhandled DWARF instruction 0x%x\n", insn);
 547			UNWINDER_BUG();
 548			break;
 549		}
 550	}
 551
 552	return 0;
 553}
 554
 555/**
 556 *	dwarf_free_frame - free the memory allocated for @frame
 557 *	@frame: the frame to free
 558 */
 559void dwarf_free_frame(struct dwarf_frame *frame)
 560{
 561	dwarf_frame_free_regs(frame);
 562	mempool_free(frame, dwarf_frame_pool);
 563}
 564
 565extern void ret_from_irq(void);
 566
 567/**
 568 *	dwarf_unwind_stack - unwind the stack
 569 *
 570 *	@pc: address of the function to unwind
 571 *	@prev: struct dwarf_frame of the previous stackframe on the callstack
 572 *
 573 *	Return a struct dwarf_frame representing the most recent frame
 574 *	on the callstack. Each of the lower (older) stack frames are
 575 *	linked via the "prev" member.
 576 */
 577struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
 578				       struct dwarf_frame *prev)
 579{
 580	struct dwarf_frame *frame;
 581	struct dwarf_cie *cie;
 582	struct dwarf_fde *fde;
 583	struct dwarf_reg *reg;
 584	unsigned long addr;
 585
 586	/*
 587	 * If we've been called in to before initialization has
 588	 * completed, bail out immediately.
 589	 */
 590	if (!dwarf_unwinder_ready)
 591		return NULL;
 592
 593	/*
 594	 * If we're starting at the top of the stack we need get the
 595	 * contents of a physical register to get the CFA in order to
 596	 * begin the virtual unwinding of the stack.
 597	 *
 598	 * NOTE: the return address is guaranteed to be setup by the
 599	 * time this function makes its first function call.
 600	 */
 601	if (!pc || !prev)
 602		pc = (unsigned long)current_text_addr();
 603
 604#ifdef CONFIG_FUNCTION_GRAPH_TRACER
 605	/*
 606	 * If our stack has been patched by the function graph tracer
 607	 * then we might see the address of return_to_handler() where we
 608	 * expected to find the real return address.
 609	 */
 610	if (pc == (unsigned long)&return_to_handler) {
 611		int index = current->curr_ret_stack;
 612
 613		/*
 614		 * We currently have no way of tracking how many
 615		 * return_to_handler()'s we've seen. If there is more
 616		 * than one patched return address on our stack,
 617		 * complain loudly.
 618		 */
 619		WARN_ON(index > 0);
 620
 621		pc = current->ret_stack[index].ret;
 622	}
 623#endif
 624
 625	frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
 626	if (!frame) {
 627		printk(KERN_ERR "Unable to allocate a dwarf frame\n");
 628		UNWINDER_BUG();
 629	}
 630
 631	INIT_LIST_HEAD(&frame->reg_list);
 632	frame->flags = 0;
 633	frame->prev = prev;
 634	frame->return_addr = 0;
 635
 636	fde = dwarf_lookup_fde(pc);
 637	if (!fde) {
 638		/*
 639		 * This is our normal exit path. There are two reasons
 640		 * why we might exit here,
 641		 *
 642		 *	a) pc has no asscociated DWARF frame info and so
 643		 *	we don't know how to unwind this frame. This is
 644		 *	usually the case when we're trying to unwind a
 645		 *	frame that was called from some assembly code
 646		 *	that has no DWARF info, e.g. syscalls.
 647		 *
 648		 *	b) the DEBUG info for pc is bogus. There's
 649		 *	really no way to distinguish this case from the
 650		 *	case above, which sucks because we could print a
 651		 *	warning here.
 652		 */
 653		goto bail;
 654	}
 655
 656	cie = dwarf_lookup_cie(fde->cie_pointer);
 657
 658	frame->pc = fde->initial_location;
 659
 660	/* CIE initial instructions */
 661	dwarf_cfa_execute_insns(cie->initial_instructions,
 662				cie->instructions_end, cie, fde,
 663				frame, pc);
 664
 665	/* FDE instructions */
 666	dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
 667				fde, frame, pc);
 668
 669	/* Calculate the CFA */
 670	switch (frame->flags) {
 671	case DWARF_FRAME_CFA_REG_OFFSET:
 672		if (prev) {
 673			reg = dwarf_frame_reg(prev, frame->cfa_register);
 674			UNWINDER_BUG_ON(!reg);
 675			UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 676
 677			addr = prev->cfa + reg->addr;
 678			frame->cfa = __raw_readl(addr);
 679
 680		} else {
 681			/*
 682			 * Again, we're starting from the top of the
 683			 * stack. We need to physically read
 684			 * the contents of a register in order to get
 685			 * the Canonical Frame Address for this
 686			 * function.
 687			 */
 688			frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
 689		}
 690
 691		frame->cfa += frame->cfa_offset;
 692		break;
 693	default:
 694		UNWINDER_BUG();
 695	}
 696
 697	reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
 698
 699	/*
 700	 * If we haven't seen the return address register or the return
 701	 * address column is undefined then we must assume that this is
 702	 * the end of the callstack.
 703	 */
 704	if (!reg || reg->flags == DWARF_UNDEFINED)
 705		goto bail;
 706
 707	UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
 708
 709	addr = frame->cfa + reg->addr;
 710	frame->return_addr = __raw_readl(addr);
 711
 712	/*
 713	 * Ah, the joys of unwinding through interrupts.
 714	 *
 715	 * Interrupts are tricky - the DWARF info needs to be _really_
 716	 * accurate and unfortunately I'm seeing a lot of bogus DWARF
 717	 * info. For example, I've seen interrupts occur in epilogues
 718	 * just after the frame pointer (r14) had been restored. The
 719	 * problem was that the DWARF info claimed that the CFA could be
 720	 * reached by using the value of the frame pointer before it was
 721	 * restored.
 722	 *
 723	 * So until the compiler can be trusted to produce reliable
 724	 * DWARF info when it really matters, let's stop unwinding once
 725	 * we've calculated the function that was interrupted.
 726	 */
 727	if (prev && prev->pc == (unsigned long)ret_from_irq)
 728		frame->return_addr = 0;
 729
 730	return frame;
 731
 732bail:
 733	dwarf_free_frame(frame);
 734	return NULL;
 735}
 736
 737static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
 738			   unsigned char *end, struct module *mod)
 739{
 740	struct rb_node **rb_node = &cie_root.rb_node;
 741	struct rb_node *parent = *rb_node;
 742	struct dwarf_cie *cie;
 743	unsigned long flags;
 744	int count;
 745
 746	cie = kzalloc(sizeof(*cie), GFP_KERNEL);
 747	if (!cie)
 748		return -ENOMEM;
 749
 750	cie->length = len;
 751
 752	/*
 753	 * Record the offset into the .eh_frame section
 754	 * for this CIE. It allows this CIE to be
 755	 * quickly and easily looked up from the
 756	 * corresponding FDE.
 757	 */
 758	cie->cie_pointer = (unsigned long)entry;
 759
 760	cie->version = *(char *)p++;
 761	UNWINDER_BUG_ON(cie->version != 1);
 762
 763	cie->augmentation = p;
 764	p += strlen(cie->augmentation) + 1;
 765
 766	count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
 767	p += count;
 768
 769	count = dwarf_read_leb128(p, &cie->data_alignment_factor);
 770	p += count;
 771
 772	/*
 773	 * Which column in the rule table contains the
 774	 * return address?
 775	 */
 776	if (cie->version == 1) {
 777		cie->return_address_reg = __raw_readb(p);
 778		p++;
 779	} else {
 780		count = dwarf_read_uleb128(p, &cie->return_address_reg);
 781		p += count;
 782	}
 783
 784	if (cie->augmentation[0] == 'z') {
 785		unsigned int length, count;
 786		cie->flags |= DWARF_CIE_Z_AUGMENTATION;
 787
 788		count = dwarf_read_uleb128(p, &length);
 789		p += count;
 790
 791		UNWINDER_BUG_ON((unsigned char *)p > end);
 792
 793		cie->initial_instructions = p + length;
 794		cie->augmentation++;
 795	}
 796
 797	while (*cie->augmentation) {
 798		/*
 799		 * "L" indicates a byte showing how the
 800		 * LSDA pointer is encoded. Skip it.
 801		 */
 802		if (*cie->augmentation == 'L') {
 803			p++;
 804			cie->augmentation++;
 805		} else if (*cie->augmentation == 'R') {
 806			/*
 807			 * "R" indicates a byte showing
 808			 * how FDE addresses are
 809			 * encoded.
 810			 */
 811			cie->encoding = *(char *)p++;
 812			cie->augmentation++;
 813		} else if (*cie->augmentation == 'P') {
 814			/*
 815			 * "R" indicates a personality
 816			 * routine in the CIE
 817			 * augmentation.
 818			 */
 819			UNWINDER_BUG();
 820		} else if (*cie->augmentation == 'S') {
 821			UNWINDER_BUG();
 822		} else {
 823			/*
 824			 * Unknown augmentation. Assume
 825			 * 'z' augmentation.
 826			 */
 827			p = cie->initial_instructions;
 828			UNWINDER_BUG_ON(!p);
 829			break;
 830		}
 831	}
 832
 833	cie->initial_instructions = p;
 834	cie->instructions_end = end;
 835
 836	/* Add to list */
 837	spin_lock_irqsave(&dwarf_cie_lock, flags);
 838
 839	while (*rb_node) {
 840		struct dwarf_cie *cie_tmp;
 841
 842		cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
 843
 844		parent = *rb_node;
 845
 846		if (cie->cie_pointer < cie_tmp->cie_pointer)
 847			rb_node = &parent->rb_left;
 848		else if (cie->cie_pointer >= cie_tmp->cie_pointer)
 849			rb_node = &parent->rb_right;
 850		else
 851			WARN_ON(1);
 852	}
 853
 854	rb_link_node(&cie->node, parent, rb_node);
 855	rb_insert_color(&cie->node, &cie_root);
 856
 857#ifdef CONFIG_MODULES
 858	if (mod != NULL)
 859		list_add_tail(&cie->link, &mod->arch.cie_list);
 860#endif
 861
 862	spin_unlock_irqrestore(&dwarf_cie_lock, flags);
 863
 864	return 0;
 865}
 866
 867static int dwarf_parse_fde(void *entry, u32 entry_type,
 868			   void *start, unsigned long len,
 869			   unsigned char *end, struct module *mod)
 870{
 871	struct rb_node **rb_node = &fde_root.rb_node;
 872	struct rb_node *parent = *rb_node;
 873	struct dwarf_fde *fde;
 874	struct dwarf_cie *cie;
 875	unsigned long flags;
 876	int count;
 877	void *p = start;
 878
 879	fde = kzalloc(sizeof(*fde), GFP_KERNEL);
 880	if (!fde)
 881		return -ENOMEM;
 882
 883	fde->length = len;
 884
 885	/*
 886	 * In a .eh_frame section the CIE pointer is the
 887	 * delta between the address within the FDE
 888	 */
 889	fde->cie_pointer = (unsigned long)(p - entry_type - 4);
 890
 891	cie = dwarf_lookup_cie(fde->cie_pointer);
 892	fde->cie = cie;
 893
 894	if (cie->encoding)
 895		count = dwarf_read_encoded_value(p, &fde->initial_location,
 896						 cie->encoding);
 897	else
 898		count = dwarf_read_addr(p, &fde->initial_location);
 899
 900	p += count;
 901
 902	if (cie->encoding)
 903		count = dwarf_read_encoded_value(p, &fde->address_range,
 904						 cie->encoding & 0x0f);
 905	else
 906		count = dwarf_read_addr(p, &fde->address_range);
 907
 908	p += count;
 909
 910	if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
 911		unsigned int length;
 912		count = dwarf_read_uleb128(p, &length);
 913		p += count + length;
 914	}
 915
 916	/* Call frame instructions. */
 917	fde->instructions = p;
 918	fde->end = end;
 919
 920	/* Add to list. */
 921	spin_lock_irqsave(&dwarf_fde_lock, flags);
 922
 923	while (*rb_node) {
 924		struct dwarf_fde *fde_tmp;
 925		unsigned long tmp_start, tmp_end;
 926		unsigned long start, end;
 927
 928		fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
 929
 930		start = fde->initial_location;
 931		end = fde->initial_location + fde->address_range;
 932
 933		tmp_start = fde_tmp->initial_location;
 934		tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
 935
 936		parent = *rb_node;
 937
 938		if (start < tmp_start)
 939			rb_node = &parent->rb_left;
 940		else if (start >= tmp_end)
 941			rb_node = &parent->rb_right;
 942		else
 943			WARN_ON(1);
 944	}
 945
 946	rb_link_node(&fde->node, parent, rb_node);
 947	rb_insert_color(&fde->node, &fde_root);
 948
 949#ifdef CONFIG_MODULES
 950	if (mod != NULL)
 951		list_add_tail(&fde->link, &mod->arch.fde_list);
 952#endif
 953
 954	spin_unlock_irqrestore(&dwarf_fde_lock, flags);
 955
 956	return 0;
 957}
 958
 959static void dwarf_unwinder_dump(struct task_struct *task,
 960				struct pt_regs *regs,
 961				unsigned long *sp,
 962				const struct stacktrace_ops *ops,
 963				void *data)
 964{
 965	struct dwarf_frame *frame, *_frame;
 966	unsigned long return_addr;
 967
 968	_frame = NULL;
 969	return_addr = 0;
 970
 971	while (1) {
 972		frame = dwarf_unwind_stack(return_addr, _frame);
 973
 974		if (_frame)
 975			dwarf_free_frame(_frame);
 976
 977		_frame = frame;
 978
 979		if (!frame || !frame->return_addr)
 980			break;
 981
 982		return_addr = frame->return_addr;
 983		ops->address(data, return_addr, 1);
 984	}
 985
 986	if (frame)
 987		dwarf_free_frame(frame);
 988}
 989
 990static struct unwinder dwarf_unwinder = {
 991	.name = "dwarf-unwinder",
 992	.dump = dwarf_unwinder_dump,
 993	.rating = 150,
 994};
 995
 996static void dwarf_unwinder_cleanup(void)
 997{
 998	struct dwarf_fde *fde, *next_fde;
 999	struct dwarf_cie *cie, *next_cie;
1000
1001	/*
1002	 * Deallocate all the memory allocated for the DWARF unwinder.
1003	 * Traverse all the FDE/CIE lists and remove and free all the
1004	 * memory associated with those data structures.
1005	 */
1006	rbtree_postorder_for_each_entry_safe(fde, next_fde, &fde_root, node)
1007		kfree(fde);
1008
1009	rbtree_postorder_for_each_entry_safe(cie, next_cie, &cie_root, node)
1010		kfree(cie);
1011
1012	kmem_cache_destroy(dwarf_reg_cachep);
1013	kmem_cache_destroy(dwarf_frame_cachep);
1014}
1015
1016/**
1017 *	dwarf_parse_section - parse DWARF section
1018 *	@eh_frame_start: start address of the .eh_frame section
1019 *	@eh_frame_end: end address of the .eh_frame section
1020 *	@mod: the kernel module containing the .eh_frame section
1021 *
1022 *	Parse the information in a .eh_frame section.
1023 */
1024static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1025			       struct module *mod)
1026{
1027	u32 entry_type;
1028	void *p, *entry;
1029	int count, err = 0;
1030	unsigned long len = 0;
1031	unsigned int c_entries, f_entries;
1032	unsigned char *end;
1033
1034	c_entries = 0;
1035	f_entries = 0;
1036	entry = eh_frame_start;
1037
1038	while ((char *)entry < eh_frame_end) {
1039		p = entry;
1040
1041		count = dwarf_entry_len(p, &len);
1042		if (count == 0) {
1043			/*
1044			 * We read a bogus length field value. There is
1045			 * nothing we can do here apart from disabling
1046			 * the DWARF unwinder. We can't even skip this
1047			 * entry and move to the next one because 'len'
1048			 * tells us where our next entry is.
1049			 */
1050			err = -EINVAL;
1051			goto out;
1052		} else
1053			p += count;
1054
1055		/* initial length does not include itself */
1056		end = p + len;
1057
1058		entry_type = get_unaligned((u32 *)p);
1059		p += 4;
1060
1061		if (entry_type == DW_EH_FRAME_CIE) {
1062			err = dwarf_parse_cie(entry, p, len, end, mod);
1063			if (err < 0)
1064				goto out;
1065			else
1066				c_entries++;
1067		} else {
1068			err = dwarf_parse_fde(entry, entry_type, p, len,
1069					      end, mod);
1070			if (err < 0)
1071				goto out;
1072			else
1073				f_entries++;
1074		}
1075
1076		entry = (char *)entry + len + 4;
1077	}
1078
1079	printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1080	       c_entries, f_entries);
1081
1082	return 0;
1083
1084out:
1085	return err;
1086}
1087
1088#ifdef CONFIG_MODULES
1089int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1090			  struct module *me)
1091{
1092	unsigned int i, err;
1093	unsigned long start, end;
1094	char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
1095
1096	start = end = 0;
1097
1098	for (i = 1; i < hdr->e_shnum; i++) {
1099		/* Alloc bit cleared means "ignore it." */
1100		if ((sechdrs[i].sh_flags & SHF_ALLOC)
1101		    && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
1102			start = sechdrs[i].sh_addr;
1103			end = start + sechdrs[i].sh_size;
1104			break;
1105		}
1106	}
1107
1108	/* Did we find the .eh_frame section? */
1109	if (i != hdr->e_shnum) {
1110		INIT_LIST_HEAD(&me->arch.cie_list);
1111		INIT_LIST_HEAD(&me->arch.fde_list);
1112		err = dwarf_parse_section((char *)start, (char *)end, me);
1113		if (err) {
1114			printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1115			       me->name);
1116			return err;
1117		}
1118	}
1119
1120	return 0;
1121}
1122
1123/**
1124 *	module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1125 *	@mod: the module that is being unloaded
1126 *
1127 *	Remove any FDEs and CIEs from the global lists that came from
1128 *	@mod's .eh_frame section because @mod is being unloaded.
1129 */
1130void module_dwarf_cleanup(struct module *mod)
1131{
1132	struct dwarf_fde *fde, *ftmp;
1133	struct dwarf_cie *cie, *ctmp;
1134	unsigned long flags;
1135
1136	spin_lock_irqsave(&dwarf_cie_lock, flags);
1137
1138	list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
1139		list_del(&cie->link);
1140		rb_erase(&cie->node, &cie_root);
1141		kfree(cie);
1142	}
1143
1144	spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1145
1146	spin_lock_irqsave(&dwarf_fde_lock, flags);
1147
1148	list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
1149		list_del(&fde->link);
1150		rb_erase(&fde->node, &fde_root);
1151		kfree(fde);
1152	}
1153
1154	spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1155}
1156#endif /* CONFIG_MODULES */
1157
1158/**
1159 *	dwarf_unwinder_init - initialise the dwarf unwinder
1160 *
1161 *	Build the data structures describing the .dwarf_frame section to
1162 *	make it easier to lookup CIE and FDE entries. Because the
1163 *	.eh_frame section is packed as tightly as possible it is not
1164 *	easy to lookup the FDE for a given PC, so we build a list of FDE
1165 *	and CIE entries that make it easier.
1166 */
1167static int __init dwarf_unwinder_init(void)
1168{
1169	int err = -ENOMEM;
1170
1171	dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1172			sizeof(struct dwarf_frame), 0,
1173			SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1174
1175	dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1176			sizeof(struct dwarf_reg), 0,
1177			SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1178
1179	dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
1180					  mempool_alloc_slab,
1181					  mempool_free_slab,
1182					  dwarf_frame_cachep);
1183	if (!dwarf_frame_pool)
1184		goto out;
1185
1186	dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
1187					 mempool_alloc_slab,
1188					 mempool_free_slab,
1189					 dwarf_reg_cachep);
1190	if (!dwarf_reg_pool)
1191		goto out;
1192
1193	err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1194	if (err)
1195		goto out;
1196
1197	err = unwinder_register(&dwarf_unwinder);
1198	if (err)
1199		goto out;
1200
1201	dwarf_unwinder_ready = 1;
1202
1203	return 0;
1204
1205out:
1206	printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1207	dwarf_unwinder_cleanup();
1208	return err;
1209}
1210early_initcall(dwarf_unwinder_init);