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 <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>
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)
38 static struct kmem_cache *dwarf_frame_cachep;
39 static mempool_t *dwarf_frame_pool;
41 static struct kmem_cache *dwarf_reg_cachep;
42 static mempool_t *dwarf_reg_pool;
44 static struct rb_root cie_root;
45 static DEFINE_SPINLOCK(dwarf_cie_lock);
47 static struct rb_root fde_root;
48 static DEFINE_SPINLOCK(dwarf_fde_lock);
50 static struct dwarf_cie *cached_cie;
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
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.
61 * Return the initialised DWARF reg.
63 static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
66 struct dwarf_reg *reg;
68 reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
70 printk(KERN_WARNING "Unable to allocate a DWARF register\n");
72 * Let's just bomb hard here, we have no way to
78 reg->number = reg_num;
82 list_add(®->link, &frame->reg_list);
87 static void dwarf_frame_free_regs(struct dwarf_frame *frame)
89 struct dwarf_reg *reg, *n;
91 list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
93 mempool_free(reg, dwarf_reg_pool);
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
102 * Lookup and return the dwarf reg @reg_num for this frame. Return
103 * NULL if @reg_num is an register invalid number.
105 static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
106 unsigned int reg_num)
108 struct dwarf_reg *reg;
110 list_for_each_entry(reg, &frame->reg_list, link) {
111 if (reg->number == reg_num)
119 * dwarf_read_addr - read dwarf data
120 * @src: source address of data
121 * @dst: destination address to store the data to
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.
129 static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
131 u32 val = get_unaligned(src);
132 put_unaligned(val, dst);
133 return sizeof(unsigned long *);
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
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.
146 static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
157 byte = __raw_readb(addr);
161 result |= (byte & 0x7f) << shift;
174 * dwarf_read_leb128 - read signed LEB128 data
175 * @addr: the address of the LEB128 encoded data
176 * @ret: address to store the result
178 * Decode signed LEB128 data. The algorithm is taken from Appendix
179 * C of the DWARF 3 spec. Return the number of bytes read.
181 static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
193 byte = __raw_readb(addr);
195 result |= (byte & 0x7f) << shift;
203 /* The number of bits in a signed integer. */
204 num_bits = 8 * sizeof(result);
206 if ((shift < num_bits) && (byte & 0x40))
207 result |= (-1 << shift);
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
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.
224 static int dwarf_read_encoded_value(char *addr, unsigned long *val,
227 unsigned long decoded_addr = 0;
230 switch (encoding & 0x70) {
231 case DW_EH_PE_absptr:
234 decoded_addr = (unsigned long)addr;
237 pr_debug("encoding=0x%x\n", (encoding & 0x70));
241 if ((encoding & 0x07) == 0x00)
242 encoding |= DW_EH_PE_udata4;
244 switch (encoding & 0x0f) {
245 case DW_EH_PE_sdata4:
246 case DW_EH_PE_udata4:
248 decoded_addr += get_unaligned((u32 *)addr);
249 __raw_writel(decoded_addr, val);
252 pr_debug("encoding=0x%x\n", encoding);
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
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.
268 static inline int dwarf_entry_len(char *addr, unsigned long *len)
273 initial_len = get_unaligned((u32 *)addr);
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.
282 if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
284 * The 64-bit length field immediately follows the
285 * compulsory 32-bit length field.
287 if (initial_len == DW_EXT_DWARF64) {
288 *len = get_unaligned((u64 *)addr + 4);
291 printk(KERN_WARNING "Unknown DWARF extension\n");
301 * dwarf_lookup_cie - locate the cie
302 * @cie_ptr: pointer to help with lookup
304 static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
306 struct rb_node **rb_node = &cie_root.rb_node;
307 struct dwarf_cie *cie = NULL;
310 spin_lock_irqsave(&dwarf_cie_lock, flags);
313 * We've cached the last CIE we looked up because chances are
314 * that the FDE wants this CIE.
316 if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
322 struct dwarf_cie *cie_tmp;
324 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
327 if (cie_ptr == cie_tmp->cie_pointer) {
329 cached_cie = cie_tmp;
332 if (cie_ptr < cie_tmp->cie_pointer)
333 rb_node = &(*rb_node)->rb_left;
335 rb_node = &(*rb_node)->rb_right;
340 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
345 * dwarf_lookup_fde - locate the FDE that covers pc
346 * @pc: the program counter
348 struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
350 struct rb_node **rb_node = &fde_root.rb_node;
351 struct dwarf_fde *fde = NULL;
354 spin_lock_irqsave(&dwarf_fde_lock, flags);
357 struct dwarf_fde *fde_tmp;
358 unsigned long tmp_start, tmp_end;
360 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
363 tmp_start = fde_tmp->initial_location;
364 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
366 if (pc < tmp_start) {
367 rb_node = &(*rb_node)->rb_left;
373 rb_node = &(*rb_node)->rb_right;
378 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
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
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.
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,
405 unsigned char *current_insn;
406 unsigned int count, delta, reg, expr_len, offset;
407 struct dwarf_reg *regp;
409 current_insn = insn_start;
411 while (current_insn < insn_end && frame->pc <= pc) {
412 insn = __raw_readb(current_insn++);
415 * Firstly, handle the opcodes that embed their operands
416 * in the instructions.
418 switch (DW_CFA_opcode(insn)) {
419 case DW_CFA_advance_loc:
420 delta = DW_CFA_operand(insn);
421 delta *= cie->code_alignment_factor;
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);
432 regp->flags |= DWARF_REG_OFFSET;
436 reg = DW_CFA_operand(insn);
442 * Secondly, handle the opcodes that don't embed their
443 * operands in the instruction.
448 case DW_CFA_advance_loc1:
449 delta = *current_insn++;
450 frame->pc += delta * cie->code_alignment_factor;
452 case DW_CFA_advance_loc2:
453 delta = get_unaligned((u16 *)current_insn);
455 frame->pc += delta * cie->code_alignment_factor;
457 case DW_CFA_advance_loc4:
458 delta = get_unaligned((u32 *)current_insn);
460 frame->pc += delta * cie->code_alignment_factor;
462 case DW_CFA_offset_extended:
463 count = dwarf_read_uleb128(current_insn, ®);
464 current_insn += count;
465 count = dwarf_read_uleb128(current_insn, &offset);
466 current_insn += count;
467 offset *= cie->data_alignment_factor;
469 case DW_CFA_restore_extended:
470 count = dwarf_read_uleb128(current_insn, ®);
471 current_insn += count;
473 case DW_CFA_undefined:
474 count = dwarf_read_uleb128(current_insn, ®);
475 current_insn += count;
476 regp = dwarf_frame_alloc_reg(frame, reg);
477 regp->flags |= DWARF_UNDEFINED;
480 count = dwarf_read_uleb128(current_insn,
481 &frame->cfa_register);
482 current_insn += count;
483 count = dwarf_read_uleb128(current_insn,
485 current_insn += count;
487 frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
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;
495 case DW_CFA_def_cfa_offset:
496 count = dwarf_read_uleb128(current_insn, &offset);
497 current_insn += count;
498 frame->cfa_offset = offset;
500 case DW_CFA_def_cfa_expression:
501 count = dwarf_read_uleb128(current_insn, &expr_len);
502 current_insn += count;
504 frame->cfa_expr = current_insn;
505 frame->cfa_expr_len = expr_len;
506 current_insn += expr_len;
508 frame->flags |= DWARF_FRAME_CFA_REG_EXP;
510 case DW_CFA_offset_extended_sf:
511 count = dwarf_read_uleb128(current_insn, ®);
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;
520 case DW_CFA_val_offset:
521 count = dwarf_read_uleb128(current_insn, ®);
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;
529 case DW_CFA_GNU_args_size:
530 count = dwarf_read_uleb128(current_insn, &offset);
531 current_insn += count;
533 case DW_CFA_GNU_negative_offset_extended:
534 count = dwarf_read_uleb128(current_insn, ®);
535 current_insn += count;
536 count = dwarf_read_uleb128(current_insn, &offset);
537 offset *= cie->data_alignment_factor;
539 regp = dwarf_frame_alloc_reg(frame, reg);
540 regp->flags |= DWARF_REG_OFFSET;
541 regp->addr = -offset;
544 pr_debug("unhandled DWARF instruction 0x%x\n", insn);
554 * dwarf_free_frame - free the memory allocated for @frame
555 * @frame: the frame to free
557 void dwarf_free_frame(struct dwarf_frame *frame)
559 dwarf_frame_free_regs(frame);
560 mempool_free(frame, dwarf_frame_pool);
563 extern void ret_from_irq(void);
566 * dwarf_unwind_stack - unwind the stack
568 * @pc: address of the function to unwind
569 * @prev: struct dwarf_frame of the previous stackframe on the callstack
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.
575 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
576 struct dwarf_frame *prev)
578 struct dwarf_frame *frame;
579 struct dwarf_cie *cie;
580 struct dwarf_fde *fde;
581 struct dwarf_reg *reg;
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.
589 * NOTE: the return address is guaranteed to be setup by the
590 * time this function makes its first function call.
593 pc = (unsigned long)current_text_addr();
595 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.
601 if (pc == (unsigned long)&return_to_handler) {
602 int index = current->curr_ret_stack;
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,
612 pc = current->ret_stack[index].ret;
616 frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
618 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
622 INIT_LIST_HEAD(&frame->reg_list);
625 frame->return_addr = 0;
627 fde = dwarf_lookup_fde(pc);
630 * This is our normal exit path. There are two reasons
631 * why we might exit here,
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.
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
647 cie = dwarf_lookup_cie(fde->cie_pointer);
649 frame->pc = fde->initial_location;
651 /* CIE initial instructions */
652 dwarf_cfa_execute_insns(cie->initial_instructions,
653 cie->instructions_end, cie, fde,
656 /* FDE instructions */
657 dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
660 /* Calculate the CFA */
661 switch (frame->flags) {
662 case DWARF_FRAME_CFA_REG_OFFSET:
664 reg = dwarf_frame_reg(prev, frame->cfa_register);
665 UNWINDER_BUG_ON(!reg);
666 UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
668 addr = prev->cfa + reg->addr;
669 frame->cfa = __raw_readl(addr);
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
679 frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
682 frame->cfa += frame->cfa_offset;
688 reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
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.
695 if (!reg || reg->flags == DWARF_UNDEFINED)
698 UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
700 addr = frame->cfa + reg->addr;
701 frame->return_addr = __raw_readl(addr);
704 * Ah, the joys of unwinding through interrupts.
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
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.
718 if (prev && prev->pc == (unsigned long)ret_from_irq)
719 frame->return_addr = 0;
724 dwarf_free_frame(frame);
728 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
729 unsigned char *end, struct module *mod)
731 struct rb_node **rb_node = &cie_root.rb_node;
732 struct rb_node *parent = *rb_node;
733 struct dwarf_cie *cie;
737 cie = kzalloc(sizeof(*cie), GFP_KERNEL);
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
749 cie->cie_pointer = (unsigned long)entry;
751 cie->version = *(char *)p++;
752 UNWINDER_BUG_ON(cie->version != 1);
754 cie->augmentation = p;
755 p += strlen(cie->augmentation) + 1;
757 count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
760 count = dwarf_read_leb128(p, &cie->data_alignment_factor);
764 * Which column in the rule table contains the
767 if (cie->version == 1) {
768 cie->return_address_reg = __raw_readb(p);
771 count = dwarf_read_uleb128(p, &cie->return_address_reg);
775 if (cie->augmentation[0] == 'z') {
776 unsigned int length, count;
777 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
779 count = dwarf_read_uleb128(p, &length);
782 UNWINDER_BUG_ON((unsigned char *)p > end);
784 cie->initial_instructions = p + length;
788 while (*cie->augmentation) {
790 * "L" indicates a byte showing how the
791 * LSDA pointer is encoded. Skip it.
793 if (*cie->augmentation == 'L') {
796 } else if (*cie->augmentation == 'R') {
798 * "R" indicates a byte showing
799 * how FDE addresses are
802 cie->encoding = *(char *)p++;
804 } else if (*cie->augmentation == 'P') {
806 * "R" indicates a personality
811 } else if (*cie->augmentation == 'S') {
815 * Unknown augmentation. Assume
818 p = cie->initial_instructions;
824 cie->initial_instructions = p;
825 cie->instructions_end = end;
828 spin_lock_irqsave(&dwarf_cie_lock, flags);
831 struct dwarf_cie *cie_tmp;
833 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
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;
845 rb_link_node(&cie->node, parent, rb_node);
846 rb_insert_color(&cie->node, &cie_root);
849 list_add_tail(&cie->link, &mod->arch.cie_list);
851 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
856 static int dwarf_parse_fde(void *entry, u32 entry_type,
857 void *start, unsigned long len,
858 unsigned char *end, struct module *mod)
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;
868 fde = kzalloc(sizeof(*fde), GFP_KERNEL);
875 * In a .eh_frame section the CIE pointer is the
876 * delta between the address within the FDE
878 fde->cie_pointer = (unsigned long)(p - entry_type - 4);
880 cie = dwarf_lookup_cie(fde->cie_pointer);
884 count = dwarf_read_encoded_value(p, &fde->initial_location,
887 count = dwarf_read_addr(p, &fde->initial_location);
892 count = dwarf_read_encoded_value(p, &fde->address_range,
893 cie->encoding & 0x0f);
895 count = dwarf_read_addr(p, &fde->address_range);
899 if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
901 count = dwarf_read_uleb128(p, &length);
905 /* Call frame instructions. */
906 fde->instructions = p;
910 spin_lock_irqsave(&dwarf_fde_lock, flags);
913 struct dwarf_fde *fde_tmp;
914 unsigned long tmp_start, tmp_end;
915 unsigned long start, end;
917 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
919 start = fde->initial_location;
920 end = fde->initial_location + fde->address_range;
922 tmp_start = fde_tmp->initial_location;
923 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
927 if (start < tmp_start)
928 rb_node = &parent->rb_left;
929 else if (start >= tmp_end)
930 rb_node = &parent->rb_right;
935 rb_link_node(&fde->node, parent, rb_node);
936 rb_insert_color(&fde->node, &fde_root);
939 list_add_tail(&fde->link, &mod->arch.fde_list);
941 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
946 static void dwarf_unwinder_dump(struct task_struct *task,
947 struct pt_regs *regs,
949 const struct stacktrace_ops *ops,
952 struct dwarf_frame *frame, *_frame;
953 unsigned long return_addr;
959 frame = dwarf_unwind_stack(return_addr, _frame);
962 dwarf_free_frame(_frame);
966 if (!frame || !frame->return_addr)
969 return_addr = frame->return_addr;
970 ops->address(data, return_addr, 1);
974 dwarf_free_frame(frame);
977 static struct unwinder dwarf_unwinder = {
978 .name = "dwarf-unwinder",
979 .dump = dwarf_unwinder_dump,
983 static void dwarf_unwinder_cleanup(void)
985 struct rb_node **fde_rb_node = &fde_root.rb_node;
986 struct rb_node **cie_rb_node = &cie_root.rb_node;
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.
993 while (*fde_rb_node) {
994 struct dwarf_fde *fde;
996 fde = rb_entry(*fde_rb_node, struct dwarf_fde, node);
997 rb_erase(*fde_rb_node, &fde_root);
1001 while (*cie_rb_node) {
1002 struct dwarf_cie *cie;
1004 cie = rb_entry(*cie_rb_node, struct dwarf_cie, node);
1005 rb_erase(*cie_rb_node, &cie_root);
1009 kmem_cache_destroy(dwarf_reg_cachep);
1010 kmem_cache_destroy(dwarf_frame_cachep);
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
1019 * Parse the information in a .eh_frame section.
1021 static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1027 unsigned long len = 0;
1028 unsigned int c_entries, f_entries;
1033 entry = eh_frame_start;
1035 while ((char *)entry < eh_frame_end) {
1038 count = dwarf_entry_len(p, &len);
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.
1052 /* initial length does not include itself */
1055 entry_type = get_unaligned((u32 *)p);
1058 if (entry_type == DW_EH_FRAME_CIE) {
1059 err = dwarf_parse_cie(entry, p, len, end, mod);
1065 err = dwarf_parse_fde(entry, entry_type, p, len,
1073 entry = (char *)entry + len + 4;
1076 printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1077 c_entries, f_entries);
1085 #ifdef CONFIG_MODULES
1086 int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1089 unsigned int i, err;
1090 unsigned long start, end;
1091 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
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;
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);
1111 printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1121 * module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1122 * @mod: the module that is being unloaded
1124 * Remove any FDEs and CIEs from the global lists that came from
1125 * @mod's .eh_frame section because @mod is being unloaded.
1127 void module_dwarf_cleanup(struct module *mod)
1129 struct dwarf_fde *fde, *ftmp;
1130 struct dwarf_cie *cie, *ctmp;
1131 unsigned long flags;
1133 spin_lock_irqsave(&dwarf_cie_lock, flags);
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);
1141 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1143 spin_lock_irqsave(&dwarf_fde_lock, flags);
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);
1151 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1153 #endif /* CONFIG_MODULES */
1156 * dwarf_unwinder_init - initialise the dwarf unwinder
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.
1164 static int __init dwarf_unwinder_init(void)
1168 dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1169 sizeof(struct dwarf_frame), 0,
1170 SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1172 dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1173 sizeof(struct dwarf_reg), 0,
1174 SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1176 dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
1179 dwarf_frame_cachep);
1181 dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
1186 err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1190 err = unwinder_register(&dwarf_unwinder);
1197 printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1198 dwarf_unwinder_cleanup();
1201 early_initcall(dwarf_unwinder_init);