2
* Copyright (C) 2009 Matt Fleming <matt@console-pimps.org>
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* 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
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* This is an implementation of a DWARF unwinder. Its main purpose is
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* for generating stacktrace information. Based on the DWARF 3
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* specification from http://www.dwarfstd.org.
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* - DWARF64 doesn't work.
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* - Registers with DWARF_VAL_OFFSET rules aren't handled properly.
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#include <linux/kernel.h>
20
#include <linux/list.h>
21
#include <linux/mempool.h>
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#include <linux/elf.h>
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#include <linux/ftrace.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <asm/dwarf.h>
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#include <asm/unwinder.h>
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#include <asm/sections.h>
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#include <asm/unaligned.h>
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#include <asm/stacktrace.h>
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/* Reserve enough memory for two stack frames */
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#define DWARF_FRAME_MIN_REQ 2
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/* ... with 4 registers per frame. */
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#define DWARF_REG_MIN_REQ (DWARF_FRAME_MIN_REQ * 4)
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static struct kmem_cache *dwarf_frame_cachep;
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static mempool_t *dwarf_frame_pool;
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static struct kmem_cache *dwarf_reg_cachep;
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static mempool_t *dwarf_reg_pool;
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static struct rb_root cie_root;
45
static DEFINE_SPINLOCK(dwarf_cie_lock);
47
static struct rb_root fde_root;
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static DEFINE_SPINLOCK(dwarf_fde_lock);
50
static struct dwarf_cie *cached_cie;
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static unsigned int dwarf_unwinder_ready;
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* dwarf_frame_alloc_reg - allocate memory for a DWARF register
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* @frame: the DWARF frame whose list of registers we insert on
57
* @reg_num: the register number
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* Allocate space for, and initialise, a dwarf reg from
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* dwarf_reg_pool and insert it onto the (unsorted) linked-list of
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* dwarf registers for @frame.
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* Return the initialised DWARF reg.
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static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
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struct dwarf_reg *reg;
70
reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
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printk(KERN_WARNING "Unable to allocate a DWARF register\n");
74
* Let's just bomb hard here, we have no way to
80
reg->number = reg_num;
84
list_add(®->link, &frame->reg_list);
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static void dwarf_frame_free_regs(struct dwarf_frame *frame)
91
struct dwarf_reg *reg, *n;
93
list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
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mempool_free(reg, dwarf_reg_pool);
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* dwarf_frame_reg - return a DWARF register
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* @frame: the DWARF frame to search in for @reg_num
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* @reg_num: the register number to search for
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* Lookup and return the dwarf reg @reg_num for this frame. Return
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* NULL if @reg_num is an register invalid number.
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static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
108
unsigned int reg_num)
110
struct dwarf_reg *reg;
112
list_for_each_entry(reg, &frame->reg_list, link) {
113
if (reg->number == reg_num)
121
* dwarf_read_addr - read dwarf data
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* @src: source address of data
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* @dst: destination address to store the data to
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.
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static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
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u32 val = get_unaligned(src);
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put_unaligned(val, dst);
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return sizeof(unsigned long *);
139
* dwarf_read_uleb128 - read unsigned LEB128 data
140
* @addr: the address where the ULEB128 data is stored
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* @ret: address to store the result
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.
148
static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
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byte = __raw_readb(addr);
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result |= (byte & 0x7f) << shift;
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* dwarf_read_leb128 - read signed LEB128 data
177
* @addr: the address of the LEB128 encoded data
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* @ret: address to store the result
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* Decode signed LEB128 data. The algorithm is taken from Appendix
181
* C of the DWARF 3 spec. Return the number of bytes read.
183
static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
195
byte = __raw_readb(addr);
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result |= (byte & 0x7f) << shift;
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/* The number of bits in a signed integer. */
206
num_bits = 8 * sizeof(result);
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if ((shift < num_bits) && (byte & 0x40))
209
result |= (-1 << shift);
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* dwarf_read_encoded_value - return the decoded value at @addr
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* @addr: the address of the encoded value
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* @val: where to write the decoded value
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* @encoding: the encoding with which we can decode @addr
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* 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.
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static int dwarf_read_encoded_value(char *addr, unsigned long *val,
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unsigned long decoded_addr = 0;
232
switch (encoding & 0x70) {
233
case DW_EH_PE_absptr:
236
decoded_addr = (unsigned long)addr;
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pr_debug("encoding=0x%x\n", (encoding & 0x70));
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if ((encoding & 0x07) == 0x00)
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encoding |= DW_EH_PE_udata4;
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switch (encoding & 0x0f) {
247
case DW_EH_PE_sdata4:
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case DW_EH_PE_udata4:
250
decoded_addr += get_unaligned((u32 *)addr);
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__raw_writel(decoded_addr, val);
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pr_debug("encoding=0x%x\n", encoding);
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
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.
270
static inline int dwarf_entry_len(char *addr, unsigned long *len)
275
initial_len = get_unaligned((u32 *)addr);
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.
284
if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
286
* The 64-bit length field immediately follows the
287
* compulsory 32-bit length field.
289
if (initial_len == DW_EXT_DWARF64) {
290
*len = get_unaligned((u64 *)addr + 4);
293
printk(KERN_WARNING "Unknown DWARF extension\n");
303
* dwarf_lookup_cie - locate the cie
304
* @cie_ptr: pointer to help with lookup
306
static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
308
struct rb_node **rb_node = &cie_root.rb_node;
309
struct dwarf_cie *cie = NULL;
312
spin_lock_irqsave(&dwarf_cie_lock, flags);
315
* We've cached the last CIE we looked up because chances are
316
* that the FDE wants this CIE.
318
if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
324
struct dwarf_cie *cie_tmp;
326
cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
329
if (cie_ptr == cie_tmp->cie_pointer) {
331
cached_cie = cie_tmp;
334
if (cie_ptr < cie_tmp->cie_pointer)
335
rb_node = &(*rb_node)->rb_left;
337
rb_node = &(*rb_node)->rb_right;
342
spin_unlock_irqrestore(&dwarf_cie_lock, flags);
347
* dwarf_lookup_fde - locate the FDE that covers pc
348
* @pc: the program counter
350
struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
352
struct rb_node **rb_node = &fde_root.rb_node;
353
struct dwarf_fde *fde = NULL;
356
spin_lock_irqsave(&dwarf_fde_lock, flags);
359
struct dwarf_fde *fde_tmp;
360
unsigned long tmp_start, tmp_end;
362
fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
365
tmp_start = fde_tmp->initial_location;
366
tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
368
if (pc < tmp_start) {
369
rb_node = &(*rb_node)->rb_left;
375
rb_node = &(*rb_node)->rb_right;
380
spin_unlock_irqrestore(&dwarf_fde_lock, flags);
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
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.
399
static 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,
407
unsigned char *current_insn;
408
unsigned int count, delta, reg, expr_len, offset;
409
struct dwarf_reg *regp;
411
current_insn = insn_start;
413
while (current_insn < insn_end && frame->pc <= pc) {
414
insn = __raw_readb(current_insn++);
417
* Firstly, handle the opcodes that embed their operands
418
* in the instructions.
420
switch (DW_CFA_opcode(insn)) {
421
case DW_CFA_advance_loc:
422
delta = DW_CFA_operand(insn);
423
delta *= cie->code_alignment_factor;
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);
434
regp->flags |= DWARF_REG_OFFSET;
438
reg = DW_CFA_operand(insn);
444
* Secondly, handle the opcodes that don't embed their
445
* operands in the instruction.
450
case DW_CFA_advance_loc1:
451
delta = *current_insn++;
452
frame->pc += delta * cie->code_alignment_factor;
454
case DW_CFA_advance_loc2:
455
delta = get_unaligned((u16 *)current_insn);
457
frame->pc += delta * cie->code_alignment_factor;
459
case DW_CFA_advance_loc4:
460
delta = get_unaligned((u32 *)current_insn);
462
frame->pc += delta * cie->code_alignment_factor;
464
case DW_CFA_offset_extended:
465
count = dwarf_read_uleb128(current_insn, ®);
466
current_insn += count;
467
count = dwarf_read_uleb128(current_insn, &offset);
468
current_insn += count;
469
offset *= cie->data_alignment_factor;
471
case DW_CFA_restore_extended:
472
count = dwarf_read_uleb128(current_insn, ®);
473
current_insn += count;
475
case DW_CFA_undefined:
476
count = dwarf_read_uleb128(current_insn, ®);
477
current_insn += count;
478
regp = dwarf_frame_alloc_reg(frame, reg);
479
regp->flags |= DWARF_UNDEFINED;
482
count = dwarf_read_uleb128(current_insn,
483
&frame->cfa_register);
484
current_insn += count;
485
count = dwarf_read_uleb128(current_insn,
487
current_insn += count;
489
frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
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;
497
case DW_CFA_def_cfa_offset:
498
count = dwarf_read_uleb128(current_insn, &offset);
499
current_insn += count;
500
frame->cfa_offset = offset;
502
case DW_CFA_def_cfa_expression:
503
count = dwarf_read_uleb128(current_insn, &expr_len);
504
current_insn += count;
506
frame->cfa_expr = current_insn;
507
frame->cfa_expr_len = expr_len;
508
current_insn += expr_len;
510
frame->flags |= DWARF_FRAME_CFA_REG_EXP;
512
case DW_CFA_offset_extended_sf:
513
count = dwarf_read_uleb128(current_insn, ®);
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;
522
case DW_CFA_val_offset:
523
count = dwarf_read_uleb128(current_insn, ®);
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;
531
case DW_CFA_GNU_args_size:
532
count = dwarf_read_uleb128(current_insn, &offset);
533
current_insn += count;
535
case DW_CFA_GNU_negative_offset_extended:
536
count = dwarf_read_uleb128(current_insn, ®);
537
current_insn += count;
538
count = dwarf_read_uleb128(current_insn, &offset);
539
offset *= cie->data_alignment_factor;
541
regp = dwarf_frame_alloc_reg(frame, reg);
542
regp->flags |= DWARF_REG_OFFSET;
543
regp->addr = -offset;
546
pr_debug("unhandled DWARF instruction 0x%x\n", insn);
556
* dwarf_free_frame - free the memory allocated for @frame
557
* @frame: the frame to free
559
void dwarf_free_frame(struct dwarf_frame *frame)
561
dwarf_frame_free_regs(frame);
562
mempool_free(frame, dwarf_frame_pool);
565
extern void ret_from_irq(void);
568
* dwarf_unwind_stack - unwind the stack
570
* @pc: address of the function to unwind
571
* @prev: struct dwarf_frame of the previous stackframe on the callstack
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.
577
struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
578
struct dwarf_frame *prev)
580
struct dwarf_frame *frame;
581
struct dwarf_cie *cie;
582
struct dwarf_fde *fde;
583
struct dwarf_reg *reg;
587
* If we've been called in to before initialization has
588
* completed, bail out immediately.
590
if (!dwarf_unwinder_ready)
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.
598
* NOTE: the return address is guaranteed to be setup by the
599
* time this function makes its first function call.
602
pc = (unsigned long)current_text_addr();
604
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.
610
if (pc == (unsigned long)&return_to_handler) {
611
int index = current->curr_ret_stack;
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,
621
pc = current->ret_stack[index].ret;
625
frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
627
printk(KERN_ERR "Unable to allocate a dwarf frame\n");
631
INIT_LIST_HEAD(&frame->reg_list);
634
frame->return_addr = 0;
636
fde = dwarf_lookup_fde(pc);
639
* This is our normal exit path. There are two reasons
640
* why we might exit here,
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.
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
656
cie = dwarf_lookup_cie(fde->cie_pointer);
658
frame->pc = fde->initial_location;
660
/* CIE initial instructions */
661
dwarf_cfa_execute_insns(cie->initial_instructions,
662
cie->instructions_end, cie, fde,
665
/* FDE instructions */
666
dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
669
/* Calculate the CFA */
670
switch (frame->flags) {
671
case DWARF_FRAME_CFA_REG_OFFSET:
673
reg = dwarf_frame_reg(prev, frame->cfa_register);
674
UNWINDER_BUG_ON(!reg);
675
UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
677
addr = prev->cfa + reg->addr;
678
frame->cfa = __raw_readl(addr);
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
688
frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
691
frame->cfa += frame->cfa_offset;
697
reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
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.
704
if (!reg || reg->flags == DWARF_UNDEFINED)
707
UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
709
addr = frame->cfa + reg->addr;
710
frame->return_addr = __raw_readl(addr);
713
* Ah, the joys of unwinding through interrupts.
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
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.
727
if (prev && prev->pc == (unsigned long)ret_from_irq)
728
frame->return_addr = 0;
733
dwarf_free_frame(frame);
737
static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
738
unsigned char *end, struct module *mod)
740
struct rb_node **rb_node = &cie_root.rb_node;
741
struct rb_node *parent = *rb_node;
742
struct dwarf_cie *cie;
746
cie = kzalloc(sizeof(*cie), GFP_KERNEL);
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
758
cie->cie_pointer = (unsigned long)entry;
760
cie->version = *(char *)p++;
761
UNWINDER_BUG_ON(cie->version != 1);
763
cie->augmentation = p;
764
p += strlen(cie->augmentation) + 1;
766
count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
769
count = dwarf_read_leb128(p, &cie->data_alignment_factor);
773
* Which column in the rule table contains the
776
if (cie->version == 1) {
777
cie->return_address_reg = __raw_readb(p);
780
count = dwarf_read_uleb128(p, &cie->return_address_reg);
784
if (cie->augmentation[0] == 'z') {
785
unsigned int length, count;
786
cie->flags |= DWARF_CIE_Z_AUGMENTATION;
788
count = dwarf_read_uleb128(p, &length);
791
UNWINDER_BUG_ON((unsigned char *)p > end);
793
cie->initial_instructions = p + length;
797
while (*cie->augmentation) {
799
* "L" indicates a byte showing how the
800
* LSDA pointer is encoded. Skip it.
802
if (*cie->augmentation == 'L') {
805
} else if (*cie->augmentation == 'R') {
807
* "R" indicates a byte showing
808
* how FDE addresses are
811
cie->encoding = *(char *)p++;
813
} else if (*cie->augmentation == 'P') {
815
* "R" indicates a personality
820
} else if (*cie->augmentation == 'S') {
824
* Unknown augmentation. Assume
827
p = cie->initial_instructions;
833
cie->initial_instructions = p;
834
cie->instructions_end = end;
837
spin_lock_irqsave(&dwarf_cie_lock, flags);
840
struct dwarf_cie *cie_tmp;
842
cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
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;
854
rb_link_node(&cie->node, parent, rb_node);
855
rb_insert_color(&cie->node, &cie_root);
857
#ifdef CONFIG_MODULES
859
list_add_tail(&cie->link, &mod->arch.cie_list);
862
spin_unlock_irqrestore(&dwarf_cie_lock, flags);
867
static int dwarf_parse_fde(void *entry, u32 entry_type,
868
void *start, unsigned long len,
869
unsigned char *end, struct module *mod)
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;
879
fde = kzalloc(sizeof(*fde), GFP_KERNEL);
886
* In a .eh_frame section the CIE pointer is the
887
* delta between the address within the FDE
889
fde->cie_pointer = (unsigned long)(p - entry_type - 4);
891
cie = dwarf_lookup_cie(fde->cie_pointer);
895
count = dwarf_read_encoded_value(p, &fde->initial_location,
898
count = dwarf_read_addr(p, &fde->initial_location);
903
count = dwarf_read_encoded_value(p, &fde->address_range,
904
cie->encoding & 0x0f);
906
count = dwarf_read_addr(p, &fde->address_range);
910
if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
912
count = dwarf_read_uleb128(p, &length);
916
/* Call frame instructions. */
917
fde->instructions = p;
921
spin_lock_irqsave(&dwarf_fde_lock, flags);
924
struct dwarf_fde *fde_tmp;
925
unsigned long tmp_start, tmp_end;
926
unsigned long start, end;
928
fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
930
start = fde->initial_location;
931
end = fde->initial_location + fde->address_range;
933
tmp_start = fde_tmp->initial_location;
934
tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
938
if (start < tmp_start)
939
rb_node = &parent->rb_left;
940
else if (start >= tmp_end)
941
rb_node = &parent->rb_right;
946
rb_link_node(&fde->node, parent, rb_node);
947
rb_insert_color(&fde->node, &fde_root);
949
#ifdef CONFIG_MODULES
951
list_add_tail(&fde->link, &mod->arch.fde_list);
954
spin_unlock_irqrestore(&dwarf_fde_lock, flags);
959
static void dwarf_unwinder_dump(struct task_struct *task,
960
struct pt_regs *regs,
962
const struct stacktrace_ops *ops,
965
struct dwarf_frame *frame, *_frame;
966
unsigned long return_addr;
972
frame = dwarf_unwind_stack(return_addr, _frame);
975
dwarf_free_frame(_frame);
979
if (!frame || !frame->return_addr)
982
return_addr = frame->return_addr;
983
ops->address(data, return_addr, 1);
987
dwarf_free_frame(frame);
990
static struct unwinder dwarf_unwinder = {
991
.name = "dwarf-unwinder",
992
.dump = dwarf_unwinder_dump,
996
static void dwarf_unwinder_cleanup(void)
998
struct rb_node **fde_rb_node = &fde_root.rb_node;
999
struct rb_node **cie_rb_node = &cie_root.rb_node;
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.
1006
while (*fde_rb_node) {
1007
struct dwarf_fde *fde;
1009
fde = rb_entry(*fde_rb_node, struct dwarf_fde, node);
1010
rb_erase(*fde_rb_node, &fde_root);
1014
while (*cie_rb_node) {
1015
struct dwarf_cie *cie;
1017
cie = rb_entry(*cie_rb_node, struct dwarf_cie, node);
1018
rb_erase(*cie_rb_node, &cie_root);
1022
kmem_cache_destroy(dwarf_reg_cachep);
1023
kmem_cache_destroy(dwarf_frame_cachep);
1027
* dwarf_parse_section - parse DWARF section
1028
* @eh_frame_start: start address of the .eh_frame section
1029
* @eh_frame_end: end address of the .eh_frame section
1030
* @mod: the kernel module containing the .eh_frame section
1032
* Parse the information in a .eh_frame section.
1034
static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1040
unsigned long len = 0;
1041
unsigned int c_entries, f_entries;
1046
entry = eh_frame_start;
1048
while ((char *)entry < eh_frame_end) {
1051
count = dwarf_entry_len(p, &len);
1054
* We read a bogus length field value. There is
1055
* nothing we can do here apart from disabling
1056
* the DWARF unwinder. We can't even skip this
1057
* entry and move to the next one because 'len'
1058
* tells us where our next entry is.
1065
/* initial length does not include itself */
1068
entry_type = get_unaligned((u32 *)p);
1071
if (entry_type == DW_EH_FRAME_CIE) {
1072
err = dwarf_parse_cie(entry, p, len, end, mod);
1078
err = dwarf_parse_fde(entry, entry_type, p, len,
1086
entry = (char *)entry + len + 4;
1089
printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1090
c_entries, f_entries);
1098
#ifdef CONFIG_MODULES
1099
int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1102
unsigned int i, err;
1103
unsigned long start, end;
1104
char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
1108
for (i = 1; i < hdr->e_shnum; i++) {
1109
/* Alloc bit cleared means "ignore it." */
1110
if ((sechdrs[i].sh_flags & SHF_ALLOC)
1111
&& !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
1112
start = sechdrs[i].sh_addr;
1113
end = start + sechdrs[i].sh_size;
1118
/* Did we find the .eh_frame section? */
1119
if (i != hdr->e_shnum) {
1120
INIT_LIST_HEAD(&me->arch.cie_list);
1121
INIT_LIST_HEAD(&me->arch.fde_list);
1122
err = dwarf_parse_section((char *)start, (char *)end, me);
1124
printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1134
* module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1135
* @mod: the module that is being unloaded
1137
* Remove any FDEs and CIEs from the global lists that came from
1138
* @mod's .eh_frame section because @mod is being unloaded.
1140
void module_dwarf_cleanup(struct module *mod)
1142
struct dwarf_fde *fde, *ftmp;
1143
struct dwarf_cie *cie, *ctmp;
1144
unsigned long flags;
1146
spin_lock_irqsave(&dwarf_cie_lock, flags);
1148
list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
1149
list_del(&cie->link);
1150
rb_erase(&cie->node, &cie_root);
1154
spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1156
spin_lock_irqsave(&dwarf_fde_lock, flags);
1158
list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
1159
list_del(&fde->link);
1160
rb_erase(&fde->node, &fde_root);
1164
spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1166
#endif /* CONFIG_MODULES */
1169
* dwarf_unwinder_init - initialise the dwarf unwinder
1171
* Build the data structures describing the .dwarf_frame section to
1172
* make it easier to lookup CIE and FDE entries. Because the
1173
* .eh_frame section is packed as tightly as possible it is not
1174
* easy to lookup the FDE for a given PC, so we build a list of FDE
1175
* and CIE entries that make it easier.
1177
static int __init dwarf_unwinder_init(void)
1181
dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1182
sizeof(struct dwarf_frame), 0,
1183
SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1185
dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1186
sizeof(struct dwarf_reg), 0,
1187
SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1189
dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
1192
dwarf_frame_cachep);
1193
if (!dwarf_frame_pool)
1196
dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
1200
if (!dwarf_reg_pool)
1203
err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1207
err = unwinder_register(&dwarf_unwinder);
1211
dwarf_unwinder_ready = 1;
1216
printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1217
dwarf_unwinder_cleanup();
1220
early_initcall(dwarf_unwinder_init);