2 * Copyright (C) 2009 Matt Fleming <matt@console-pimps.org>
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
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.
13 * - DWARF64 doesn't work.
14 * - Registers with DWARF_VAL_OFFSET rules aren't handled properly.
18 #include <linux/kernel.h>
20 #include <linux/list.h>
21 #include <linux/mempool.h>
23 #include <linux/elf.h>
24 #include <linux/ftrace.h>
25 #include <asm/dwarf.h>
26 #include <asm/unwinder.h>
27 #include <asm/sections.h>
28 #include <asm/unaligned.h>
29 #include <asm/stacktrace.h>
31 /* Reserve enough memory for two stack frames */
32 #define DWARF_FRAME_MIN_REQ 2
33 /* ... with 4 registers per frame. */
34 #define DWARF_REG_MIN_REQ (DWARF_FRAME_MIN_REQ * 4)
36 static struct kmem_cache *dwarf_frame_cachep;
37 static mempool_t *dwarf_frame_pool;
39 static struct kmem_cache *dwarf_reg_cachep;
40 static mempool_t *dwarf_reg_pool;
42 static struct rb_root cie_root;
43 static DEFINE_SPINLOCK(dwarf_cie_lock);
45 static struct rb_root fde_root;
46 static DEFINE_SPINLOCK(dwarf_fde_lock);
48 static struct dwarf_cie *cached_cie;
51 * dwarf_frame_alloc_reg - allocate memory for a DWARF register
52 * @frame: the DWARF frame whose list of registers we insert on
53 * @reg_num: the register number
55 * Allocate space for, and initialise, a dwarf reg from
56 * dwarf_reg_pool and insert it onto the (unsorted) linked-list of
57 * dwarf registers for @frame.
59 * Return the initialised DWARF reg.
61 static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
64 struct dwarf_reg *reg;
66 reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
68 printk(KERN_WARNING "Unable to allocate a DWARF register\n");
70 * Let's just bomb hard here, we have no way to
76 reg->number = reg_num;
80 list_add(®->link, &frame->reg_list);
85 static void dwarf_frame_free_regs(struct dwarf_frame *frame)
87 struct dwarf_reg *reg, *n;
89 list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
91 mempool_free(reg, dwarf_reg_pool);
96 * dwarf_frame_reg - return a DWARF register
97 * @frame: the DWARF frame to search in for @reg_num
98 * @reg_num: the register number to search for
100 * Lookup and return the dwarf reg @reg_num for this frame. Return
101 * NULL if @reg_num is an register invalid number.
103 static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
104 unsigned int reg_num)
106 struct dwarf_reg *reg;
108 list_for_each_entry(reg, &frame->reg_list, link) {
109 if (reg->number == reg_num)
117 * dwarf_read_addr - read dwarf data
118 * @src: source address of data
119 * @dst: destination address to store the data to
121 * Read 'n' bytes from @src, where 'n' is the size of an address on
122 * the native machine. We return the number of bytes read, which
123 * should always be 'n'. We also have to be careful when reading
124 * from @src and writing to @dst, because they can be arbitrarily
125 * aligned. Return 'n' - the number of bytes read.
127 static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
129 u32 val = get_unaligned(src);
130 put_unaligned(val, dst);
131 return sizeof(unsigned long *);
135 * dwarf_read_uleb128 - read unsigned LEB128 data
136 * @addr: the address where the ULEB128 data is stored
137 * @ret: address to store the result
139 * Decode an unsigned LEB128 encoded datum. The algorithm is taken
140 * from Appendix C of the DWARF 3 spec. For information on the
141 * encodings refer to section "7.6 - Variable Length Data". Return
142 * the number of bytes read.
144 static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
155 byte = __raw_readb(addr);
159 result |= (byte & 0x7f) << shift;
172 * dwarf_read_leb128 - read signed LEB128 data
173 * @addr: the address of the LEB128 encoded data
174 * @ret: address to store the result
176 * Decode signed LEB128 data. The algorithm is taken from Appendix
177 * C of the DWARF 3 spec. Return the number of bytes read.
179 static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
191 byte = __raw_readb(addr);
193 result |= (byte & 0x7f) << shift;
201 /* The number of bits in a signed integer. */
202 num_bits = 8 * sizeof(result);
204 if ((shift < num_bits) && (byte & 0x40))
205 result |= (-1 << shift);
213 * dwarf_read_encoded_value - return the decoded value at @addr
214 * @addr: the address of the encoded value
215 * @val: where to write the decoded value
216 * @encoding: the encoding with which we can decode @addr
218 * GCC emits encoded address in the .eh_frame FDE entries. Decode
219 * the value at @addr using @encoding. The decoded value is written
220 * to @val and the number of bytes read is returned.
222 static int dwarf_read_encoded_value(char *addr, unsigned long *val,
225 unsigned long decoded_addr = 0;
228 switch (encoding & 0x70) {
229 case DW_EH_PE_absptr:
232 decoded_addr = (unsigned long)addr;
235 pr_debug("encoding=0x%x\n", (encoding & 0x70));
239 if ((encoding & 0x07) == 0x00)
240 encoding |= DW_EH_PE_udata4;
242 switch (encoding & 0x0f) {
243 case DW_EH_PE_sdata4:
244 case DW_EH_PE_udata4:
246 decoded_addr += get_unaligned((u32 *)addr);
247 __raw_writel(decoded_addr, val);
250 pr_debug("encoding=0x%x\n", encoding);
258 * dwarf_entry_len - return the length of an FDE or CIE
259 * @addr: the address of the entry
260 * @len: the length of the entry
262 * Read the initial_length field of the entry and store the size of
263 * the entry in @len. We return the number of bytes read. Return a
264 * count of 0 on error.
266 static inline int dwarf_entry_len(char *addr, unsigned long *len)
271 initial_len = get_unaligned((u32 *)addr);
275 * An initial length field value in the range DW_LEN_EXT_LO -
276 * DW_LEN_EXT_HI indicates an extension, and should not be
277 * interpreted as a length. The only extension that we currently
278 * understand is the use of DWARF64 addresses.
280 if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
282 * The 64-bit length field immediately follows the
283 * compulsory 32-bit length field.
285 if (initial_len == DW_EXT_DWARF64) {
286 *len = get_unaligned((u64 *)addr + 4);
289 printk(KERN_WARNING "Unknown DWARF extension\n");
299 * dwarf_lookup_cie - locate the cie
300 * @cie_ptr: pointer to help with lookup
302 static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
304 struct rb_node **rb_node = &cie_root.rb_node;
305 struct dwarf_cie *cie = NULL;
308 spin_lock_irqsave(&dwarf_cie_lock, flags);
311 * We've cached the last CIE we looked up because chances are
312 * that the FDE wants this CIE.
314 if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
320 struct dwarf_cie *cie_tmp;
322 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
325 if (cie_ptr == cie_tmp->cie_pointer) {
327 cached_cie = cie_tmp;
330 if (cie_ptr < cie_tmp->cie_pointer)
331 rb_node = &(*rb_node)->rb_left;
333 rb_node = &(*rb_node)->rb_right;
338 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
343 * dwarf_lookup_fde - locate the FDE that covers pc
344 * @pc: the program counter
346 struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
348 struct rb_node **rb_node = &fde_root.rb_node;
349 struct dwarf_fde *fde = NULL;
352 spin_lock_irqsave(&dwarf_fde_lock, flags);
355 struct dwarf_fde *fde_tmp;
356 unsigned long tmp_start, tmp_end;
358 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
361 tmp_start = fde_tmp->initial_location;
362 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
364 if (pc < tmp_start) {
365 rb_node = &(*rb_node)->rb_left;
371 rb_node = &(*rb_node)->rb_right;
376 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
382 * dwarf_cfa_execute_insns - execute instructions to calculate a CFA
383 * @insn_start: address of the first instruction
384 * @insn_end: address of the last instruction
385 * @cie: the CIE for this function
386 * @fde: the FDE for this function
387 * @frame: the instructions calculate the CFA for this frame
388 * @pc: the program counter of the address we're interested in
390 * Execute the Call Frame instruction sequence starting at
391 * @insn_start and ending at @insn_end. The instructions describe
392 * how to calculate the Canonical Frame Address of a stackframe.
393 * Store the results in @frame.
395 static int dwarf_cfa_execute_insns(unsigned char *insn_start,
396 unsigned char *insn_end,
397 struct dwarf_cie *cie,
398 struct dwarf_fde *fde,
399 struct dwarf_frame *frame,
403 unsigned char *current_insn;
404 unsigned int count, delta, reg, expr_len, offset;
405 struct dwarf_reg *regp;
407 current_insn = insn_start;
409 while (current_insn < insn_end && frame->pc <= pc) {
410 insn = __raw_readb(current_insn++);
413 * Firstly, handle the opcodes that embed their operands
414 * in the instructions.
416 switch (DW_CFA_opcode(insn)) {
417 case DW_CFA_advance_loc:
418 delta = DW_CFA_operand(insn);
419 delta *= cie->code_alignment_factor;
424 reg = DW_CFA_operand(insn);
425 count = dwarf_read_uleb128(current_insn, &offset);
426 current_insn += count;
427 offset *= cie->data_alignment_factor;
428 regp = dwarf_frame_alloc_reg(frame, reg);
430 regp->flags |= DWARF_REG_OFFSET;
434 reg = DW_CFA_operand(insn);
440 * Secondly, handle the opcodes that don't embed their
441 * operands in the instruction.
446 case DW_CFA_advance_loc1:
447 delta = *current_insn++;
448 frame->pc += delta * cie->code_alignment_factor;
450 case DW_CFA_advance_loc2:
451 delta = get_unaligned((u16 *)current_insn);
453 frame->pc += delta * cie->code_alignment_factor;
455 case DW_CFA_advance_loc4:
456 delta = get_unaligned((u32 *)current_insn);
458 frame->pc += delta * cie->code_alignment_factor;
460 case DW_CFA_offset_extended:
461 count = dwarf_read_uleb128(current_insn, ®);
462 current_insn += count;
463 count = dwarf_read_uleb128(current_insn, &offset);
464 current_insn += count;
465 offset *= cie->data_alignment_factor;
467 case DW_CFA_restore_extended:
468 count = dwarf_read_uleb128(current_insn, ®);
469 current_insn += count;
471 case DW_CFA_undefined:
472 count = dwarf_read_uleb128(current_insn, ®);
473 current_insn += count;
474 regp = dwarf_frame_alloc_reg(frame, reg);
475 regp->flags |= DWARF_UNDEFINED;
478 count = dwarf_read_uleb128(current_insn,
479 &frame->cfa_register);
480 current_insn += count;
481 count = dwarf_read_uleb128(current_insn,
483 current_insn += count;
485 frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
487 case DW_CFA_def_cfa_register:
488 count = dwarf_read_uleb128(current_insn,
489 &frame->cfa_register);
490 current_insn += count;
491 frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
493 case DW_CFA_def_cfa_offset:
494 count = dwarf_read_uleb128(current_insn, &offset);
495 current_insn += count;
496 frame->cfa_offset = offset;
498 case DW_CFA_def_cfa_expression:
499 count = dwarf_read_uleb128(current_insn, &expr_len);
500 current_insn += count;
502 frame->cfa_expr = current_insn;
503 frame->cfa_expr_len = expr_len;
504 current_insn += expr_len;
506 frame->flags |= DWARF_FRAME_CFA_REG_EXP;
508 case DW_CFA_offset_extended_sf:
509 count = dwarf_read_uleb128(current_insn, ®);
510 current_insn += count;
511 count = dwarf_read_leb128(current_insn, &offset);
512 current_insn += count;
513 offset *= cie->data_alignment_factor;
514 regp = dwarf_frame_alloc_reg(frame, reg);
515 regp->flags |= DWARF_REG_OFFSET;
518 case DW_CFA_val_offset:
519 count = dwarf_read_uleb128(current_insn, ®);
520 current_insn += count;
521 count = dwarf_read_leb128(current_insn, &offset);
522 offset *= cie->data_alignment_factor;
523 regp = dwarf_frame_alloc_reg(frame, reg);
524 regp->flags |= DWARF_VAL_OFFSET;
527 case DW_CFA_GNU_args_size:
528 count = dwarf_read_uleb128(current_insn, &offset);
529 current_insn += count;
531 case DW_CFA_GNU_negative_offset_extended:
532 count = dwarf_read_uleb128(current_insn, ®);
533 current_insn += count;
534 count = dwarf_read_uleb128(current_insn, &offset);
535 offset *= cie->data_alignment_factor;
537 regp = dwarf_frame_alloc_reg(frame, reg);
538 regp->flags |= DWARF_REG_OFFSET;
539 regp->addr = -offset;
542 pr_debug("unhandled DWARF instruction 0x%x\n", insn);
552 * dwarf_free_frame - free the memory allocated for @frame
553 * @frame: the frame to free
555 void dwarf_free_frame(struct dwarf_frame *frame)
557 dwarf_frame_free_regs(frame);
558 mempool_free(frame, dwarf_frame_pool);
561 extern void ret_from_irq(void);
564 * dwarf_unwind_stack - unwind the stack
566 * @pc: address of the function to unwind
567 * @prev: struct dwarf_frame of the previous stackframe on the callstack
569 * Return a struct dwarf_frame representing the most recent frame
570 * on the callstack. Each of the lower (older) stack frames are
571 * linked via the "prev" member.
573 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
574 struct dwarf_frame *prev)
576 struct dwarf_frame *frame;
577 struct dwarf_cie *cie;
578 struct dwarf_fde *fde;
579 struct dwarf_reg *reg;
583 * If we're starting at the top of the stack we need get the
584 * contents of a physical register to get the CFA in order to
585 * begin the virtual unwinding of the stack.
587 * NOTE: the return address is guaranteed to be setup by the
588 * time this function makes its first function call.
591 pc = (unsigned long)current_text_addr();
593 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
595 * If our stack has been patched by the function graph tracer
596 * then we might see the address of return_to_handler() where we
597 * expected to find the real return address.
599 if (pc == (unsigned long)&return_to_handler) {
600 int index = current->curr_ret_stack;
603 * We currently have no way of tracking how many
604 * return_to_handler()'s we've seen. If there is more
605 * than one patched return address on our stack,
610 pc = current->ret_stack[index].ret;
614 frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
616 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
620 INIT_LIST_HEAD(&frame->reg_list);
623 frame->return_addr = 0;
625 fde = dwarf_lookup_fde(pc);
628 * This is our normal exit path. There are two reasons
629 * why we might exit here,
631 * a) pc has no asscociated DWARF frame info and so
632 * we don't know how to unwind this frame. This is
633 * usually the case when we're trying to unwind a
634 * frame that was called from some assembly code
635 * that has no DWARF info, e.g. syscalls.
637 * b) the DEBUG info for pc is bogus. There's
638 * really no way to distinguish this case from the
639 * case above, which sucks because we could print a
645 cie = dwarf_lookup_cie(fde->cie_pointer);
647 frame->pc = fde->initial_location;
649 /* CIE initial instructions */
650 dwarf_cfa_execute_insns(cie->initial_instructions,
651 cie->instructions_end, cie, fde,
654 /* FDE instructions */
655 dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
658 /* Calculate the CFA */
659 switch (frame->flags) {
660 case DWARF_FRAME_CFA_REG_OFFSET:
662 reg = dwarf_frame_reg(prev, frame->cfa_register);
663 UNWINDER_BUG_ON(!reg);
664 UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
666 addr = prev->cfa + reg->addr;
667 frame->cfa = __raw_readl(addr);
671 * Again, we're starting from the top of the
672 * stack. We need to physically read
673 * the contents of a register in order to get
674 * the Canonical Frame Address for this
677 frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
680 frame->cfa += frame->cfa_offset;
686 reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
689 * If we haven't seen the return address register or the return
690 * address column is undefined then we must assume that this is
691 * the end of the callstack.
693 if (!reg || reg->flags == DWARF_UNDEFINED)
696 UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
698 addr = frame->cfa + reg->addr;
699 frame->return_addr = __raw_readl(addr);
702 * Ah, the joys of unwinding through interrupts.
704 * Interrupts are tricky - the DWARF info needs to be _really_
705 * accurate and unfortunately I'm seeing a lot of bogus DWARF
706 * info. For example, I've seen interrupts occur in epilogues
707 * just after the frame pointer (r14) had been restored. The
708 * problem was that the DWARF info claimed that the CFA could be
709 * reached by using the value of the frame pointer before it was
712 * So until the compiler can be trusted to produce reliable
713 * DWARF info when it really matters, let's stop unwinding once
714 * we've calculated the function that was interrupted.
716 if (prev && prev->pc == (unsigned long)ret_from_irq)
717 frame->return_addr = 0;
722 dwarf_free_frame(frame);
726 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
727 unsigned char *end, struct module *mod)
729 struct rb_node **rb_node = &cie_root.rb_node;
730 struct rb_node *parent = *rb_node;
731 struct dwarf_cie *cie;
735 cie = kzalloc(sizeof(*cie), GFP_KERNEL);
742 * Record the offset into the .eh_frame section
743 * for this CIE. It allows this CIE to be
744 * quickly and easily looked up from the
747 cie->cie_pointer = (unsigned long)entry;
749 cie->version = *(char *)p++;
750 UNWINDER_BUG_ON(cie->version != 1);
752 cie->augmentation = p;
753 p += strlen(cie->augmentation) + 1;
755 count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
758 count = dwarf_read_leb128(p, &cie->data_alignment_factor);
762 * Which column in the rule table contains the
765 if (cie->version == 1) {
766 cie->return_address_reg = __raw_readb(p);
769 count = dwarf_read_uleb128(p, &cie->return_address_reg);
773 if (cie->augmentation[0] == 'z') {
774 unsigned int length, count;
775 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
777 count = dwarf_read_uleb128(p, &length);
780 UNWINDER_BUG_ON((unsigned char *)p > end);
782 cie->initial_instructions = p + length;
786 while (*cie->augmentation) {
788 * "L" indicates a byte showing how the
789 * LSDA pointer is encoded. Skip it.
791 if (*cie->augmentation == 'L') {
794 } else if (*cie->augmentation == 'R') {
796 * "R" indicates a byte showing
797 * how FDE addresses are
800 cie->encoding = *(char *)p++;
802 } else if (*cie->augmentation == 'P') {
804 * "R" indicates a personality
809 } else if (*cie->augmentation == 'S') {
813 * Unknown augmentation. Assume
816 p = cie->initial_instructions;
822 cie->initial_instructions = p;
823 cie->instructions_end = end;
826 spin_lock_irqsave(&dwarf_cie_lock, flags);
829 struct dwarf_cie *cie_tmp;
831 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
835 if (cie->cie_pointer < cie_tmp->cie_pointer)
836 rb_node = &parent->rb_left;
837 else if (cie->cie_pointer >= cie_tmp->cie_pointer)
838 rb_node = &parent->rb_right;
843 rb_link_node(&cie->node, parent, rb_node);
844 rb_insert_color(&cie->node, &cie_root);
847 list_add_tail(&cie->link, &mod->arch.cie_list);
849 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
854 static int dwarf_parse_fde(void *entry, u32 entry_type,
855 void *start, unsigned long len,
856 unsigned char *end, struct module *mod)
858 struct rb_node **rb_node = &fde_root.rb_node;
859 struct rb_node *parent = *rb_node;
860 struct dwarf_fde *fde;
861 struct dwarf_cie *cie;
866 fde = kzalloc(sizeof(*fde), GFP_KERNEL);
873 * In a .eh_frame section the CIE pointer is the
874 * delta between the address within the FDE
876 fde->cie_pointer = (unsigned long)(p - entry_type - 4);
878 cie = dwarf_lookup_cie(fde->cie_pointer);
882 count = dwarf_read_encoded_value(p, &fde->initial_location,
885 count = dwarf_read_addr(p, &fde->initial_location);
890 count = dwarf_read_encoded_value(p, &fde->address_range,
891 cie->encoding & 0x0f);
893 count = dwarf_read_addr(p, &fde->address_range);
897 if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
899 count = dwarf_read_uleb128(p, &length);
903 /* Call frame instructions. */
904 fde->instructions = p;
908 spin_lock_irqsave(&dwarf_fde_lock, flags);
911 struct dwarf_fde *fde_tmp;
912 unsigned long tmp_start, tmp_end;
913 unsigned long start, end;
915 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
917 start = fde->initial_location;
918 end = fde->initial_location + fde->address_range;
920 tmp_start = fde_tmp->initial_location;
921 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
925 if (start < tmp_start)
926 rb_node = &parent->rb_left;
927 else if (start >= tmp_end)
928 rb_node = &parent->rb_right;
933 rb_link_node(&fde->node, parent, rb_node);
934 rb_insert_color(&fde->node, &fde_root);
937 list_add_tail(&fde->link, &mod->arch.fde_list);
939 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
944 static void dwarf_unwinder_dump(struct task_struct *task,
945 struct pt_regs *regs,
947 const struct stacktrace_ops *ops,
950 struct dwarf_frame *frame, *_frame;
951 unsigned long return_addr;
957 frame = dwarf_unwind_stack(return_addr, _frame);
960 dwarf_free_frame(_frame);
964 if (!frame || !frame->return_addr)
967 return_addr = frame->return_addr;
968 ops->address(data, return_addr, 1);
972 dwarf_free_frame(frame);
975 static struct unwinder dwarf_unwinder = {
976 .name = "dwarf-unwinder",
977 .dump = dwarf_unwinder_dump,
981 static void dwarf_unwinder_cleanup(void)
983 struct rb_node **fde_rb_node = &fde_root.rb_node;
984 struct rb_node **cie_rb_node = &cie_root.rb_node;
987 * Deallocate all the memory allocated for the DWARF unwinder.
988 * Traverse all the FDE/CIE lists and remove and free all the
989 * memory associated with those data structures.
991 while (*fde_rb_node) {
992 struct dwarf_fde *fde;
994 fde = rb_entry(*fde_rb_node, struct dwarf_fde, node);
995 rb_erase(*fde_rb_node, &fde_root);
999 while (*cie_rb_node) {
1000 struct dwarf_cie *cie;
1002 cie = rb_entry(*cie_rb_node, struct dwarf_cie, node);
1003 rb_erase(*cie_rb_node, &cie_root);
1007 kmem_cache_destroy(dwarf_reg_cachep);
1008 kmem_cache_destroy(dwarf_frame_cachep);
1012 * dwarf_parse_section - parse DWARF section
1013 * @eh_frame_start: start address of the .eh_frame section
1014 * @eh_frame_end: end address of the .eh_frame section
1015 * @mod: the kernel module containing the .eh_frame section
1017 * Parse the information in a .eh_frame section.
1019 static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1025 unsigned long len = 0;
1026 unsigned int c_entries, f_entries;
1031 entry = eh_frame_start;
1033 while ((char *)entry < eh_frame_end) {
1036 count = dwarf_entry_len(p, &len);
1039 * We read a bogus length field value. There is
1040 * nothing we can do here apart from disabling
1041 * the DWARF unwinder. We can't even skip this
1042 * entry and move to the next one because 'len'
1043 * tells us where our next entry is.
1050 /* initial length does not include itself */
1053 entry_type = get_unaligned((u32 *)p);
1056 if (entry_type == DW_EH_FRAME_CIE) {
1057 err = dwarf_parse_cie(entry, p, len, end, mod);
1063 err = dwarf_parse_fde(entry, entry_type, p, len,
1071 entry = (char *)entry + len + 4;
1074 printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1075 c_entries, f_entries);
1083 #ifdef CONFIG_MODULES
1084 int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1087 unsigned int i, err;
1088 unsigned long start, end;
1089 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
1093 for (i = 1; i < hdr->e_shnum; i++) {
1094 /* Alloc bit cleared means "ignore it." */
1095 if ((sechdrs[i].sh_flags & SHF_ALLOC)
1096 && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
1097 start = sechdrs[i].sh_addr;
1098 end = start + sechdrs[i].sh_size;
1103 /* Did we find the .eh_frame section? */
1104 if (i != hdr->e_shnum) {
1105 INIT_LIST_HEAD(&me->arch.cie_list);
1106 INIT_LIST_HEAD(&me->arch.fde_list);
1107 err = dwarf_parse_section((char *)start, (char *)end, me);
1109 printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1119 * module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1120 * @mod: the module that is being unloaded
1122 * Remove any FDEs and CIEs from the global lists that came from
1123 * @mod's .eh_frame section because @mod is being unloaded.
1125 void module_dwarf_cleanup(struct module *mod)
1127 struct dwarf_fde *fde, *ftmp;
1128 struct dwarf_cie *cie, *ctmp;
1129 unsigned long flags;
1131 spin_lock_irqsave(&dwarf_cie_lock, flags);
1133 list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
1134 list_del(&cie->link);
1135 rb_erase(&cie->node, &cie_root);
1139 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1141 spin_lock_irqsave(&dwarf_fde_lock, flags);
1143 list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
1144 list_del(&fde->link);
1145 rb_erase(&fde->node, &fde_root);
1149 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1151 #endif /* CONFIG_MODULES */
1154 * dwarf_unwinder_init - initialise the dwarf unwinder
1156 * Build the data structures describing the .dwarf_frame section to
1157 * make it easier to lookup CIE and FDE entries. Because the
1158 * .eh_frame section is packed as tightly as possible it is not
1159 * easy to lookup the FDE for a given PC, so we build a list of FDE
1160 * and CIE entries that make it easier.
1162 static int __init dwarf_unwinder_init(void)
1166 dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1167 sizeof(struct dwarf_frame), 0,
1168 SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1170 dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1171 sizeof(struct dwarf_reg), 0,
1172 SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1174 dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
1177 dwarf_frame_cachep);
1179 dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
1184 err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1188 err = unwinder_register(&dwarf_unwinder);
1195 printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1196 dwarf_unwinder_cleanup();
1199 early_initcall(dwarf_unwinder_init);