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 <asm/dwarf.h>
24 #include <asm/unwinder.h>
25 #include <asm/sections.h>
26 #include <asm/unaligned.h>
27 #include <asm/dwarf.h>
28 #include <asm/stacktrace.h>
30 /* Reserve enough memory for two stack frames */
31 #define DWARF_FRAME_MIN_REQ 2
32 /* ... with 4 registers per frame. */
33 #define DWARF_REG_MIN_REQ (DWARF_FRAME_MIN_REQ * 4)
35 static struct kmem_cache
*dwarf_frame_cachep
;
36 static mempool_t
*dwarf_frame_pool
;
38 static struct kmem_cache
*dwarf_reg_cachep
;
39 static mempool_t
*dwarf_reg_pool
;
41 static LIST_HEAD(dwarf_cie_list
);
42 static DEFINE_SPINLOCK(dwarf_cie_lock
);
44 static LIST_HEAD(dwarf_fde_list
);
45 static DEFINE_SPINLOCK(dwarf_fde_lock
);
47 static struct dwarf_cie
*cached_cie
;
50 * dwarf_frame_alloc_reg - allocate memory for a DWARF register
51 * @frame: the DWARF frame whose list of registers we insert on
52 * @reg_num: the register number
54 * Allocate space for, and initialise, a dwarf reg from
55 * dwarf_reg_pool and insert it onto the (unsorted) linked-list of
56 * dwarf registers for @frame.
58 * Return the initialised DWARF reg.
60 static struct dwarf_reg
*dwarf_frame_alloc_reg(struct dwarf_frame
*frame
,
63 struct dwarf_reg
*reg
;
65 reg
= mempool_alloc(dwarf_reg_pool
, GFP_ATOMIC
);
67 printk(KERN_WARNING
"Unable to allocate a DWARF register\n");
69 * Let's just bomb hard here, we have no way to
75 reg
->number
= reg_num
;
79 list_add(®
->link
, &frame
->reg_list
);
84 static void dwarf_frame_free_regs(struct dwarf_frame
*frame
)
86 struct dwarf_reg
*reg
, *n
;
88 list_for_each_entry_safe(reg
, n
, &frame
->reg_list
, link
) {
90 mempool_free(reg
, dwarf_reg_pool
);
95 * dwarf_frame_reg - return a DWARF register
96 * @frame: the DWARF frame to search in for @reg_num
97 * @reg_num: the register number to search for
99 * Lookup and return the dwarf reg @reg_num for this frame. Return
100 * NULL if @reg_num is an register invalid number.
102 static struct dwarf_reg
*dwarf_frame_reg(struct dwarf_frame
*frame
,
103 unsigned int reg_num
)
105 struct dwarf_reg
*reg
;
107 list_for_each_entry(reg
, &frame
->reg_list
, link
) {
108 if (reg
->number
== reg_num
)
116 * dwarf_read_addr - read dwarf data
117 * @src: source address of data
118 * @dst: destination address to store the data to
120 * Read 'n' bytes from @src, where 'n' is the size of an address on
121 * the native machine. We return the number of bytes read, which
122 * should always be 'n'. We also have to be careful when reading
123 * from @src and writing to @dst, because they can be arbitrarily
124 * aligned. Return 'n' - the number of bytes read.
126 static inline int dwarf_read_addr(unsigned long *src
, unsigned long *dst
)
128 u32 val
= get_unaligned(src
);
129 put_unaligned(val
, dst
);
130 return sizeof(unsigned long *);
134 * dwarf_read_uleb128 - read unsigned LEB128 data
135 * @addr: the address where the ULEB128 data is stored
136 * @ret: address to store the result
138 * Decode an unsigned LEB128 encoded datum. The algorithm is taken
139 * from Appendix C of the DWARF 3 spec. For information on the
140 * encodings refer to section "7.6 - Variable Length Data". Return
141 * the number of bytes read.
143 static inline unsigned long dwarf_read_uleb128(char *addr
, unsigned int *ret
)
154 byte
= __raw_readb(addr
);
158 result
|= (byte
& 0x7f) << shift
;
171 * dwarf_read_leb128 - read signed LEB128 data
172 * @addr: the address of the LEB128 encoded data
173 * @ret: address to store the result
175 * Decode signed LEB128 data. The algorithm is taken from Appendix
176 * C of the DWARF 3 spec. Return the number of bytes read.
178 static inline unsigned long dwarf_read_leb128(char *addr
, int *ret
)
190 byte
= __raw_readb(addr
);
192 result
|= (byte
& 0x7f) << shift
;
200 /* The number of bits in a signed integer. */
201 num_bits
= 8 * sizeof(result
);
203 if ((shift
< num_bits
) && (byte
& 0x40))
204 result
|= (-1 << shift
);
212 * dwarf_read_encoded_value - return the decoded value at @addr
213 * @addr: the address of the encoded value
214 * @val: where to write the decoded value
215 * @encoding: the encoding with which we can decode @addr
217 * GCC emits encoded address in the .eh_frame FDE entries. Decode
218 * the value at @addr using @encoding. The decoded value is written
219 * to @val and the number of bytes read is returned.
221 static int dwarf_read_encoded_value(char *addr
, unsigned long *val
,
224 unsigned long decoded_addr
= 0;
227 switch (encoding
& 0x70) {
228 case DW_EH_PE_absptr
:
231 decoded_addr
= (unsigned long)addr
;
234 pr_debug("encoding=0x%x\n", (encoding
& 0x70));
238 if ((encoding
& 0x07) == 0x00)
239 encoding
|= DW_EH_PE_udata4
;
241 switch (encoding
& 0x0f) {
242 case DW_EH_PE_sdata4
:
243 case DW_EH_PE_udata4
:
245 decoded_addr
+= get_unaligned((u32
*)addr
);
246 __raw_writel(decoded_addr
, val
);
249 pr_debug("encoding=0x%x\n", encoding
);
257 * dwarf_entry_len - return the length of an FDE or CIE
258 * @addr: the address of the entry
259 * @len: the length of the entry
261 * Read the initial_length field of the entry and store the size of
262 * the entry in @len. We return the number of bytes read. Return a
263 * count of 0 on error.
265 static inline int dwarf_entry_len(char *addr
, unsigned long *len
)
270 initial_len
= get_unaligned((u32
*)addr
);
274 * An initial length field value in the range DW_LEN_EXT_LO -
275 * DW_LEN_EXT_HI indicates an extension, and should not be
276 * interpreted as a length. The only extension that we currently
277 * understand is the use of DWARF64 addresses.
279 if (initial_len
>= DW_EXT_LO
&& initial_len
<= DW_EXT_HI
) {
281 * The 64-bit length field immediately follows the
282 * compulsory 32-bit length field.
284 if (initial_len
== DW_EXT_DWARF64
) {
285 *len
= get_unaligned((u64
*)addr
+ 4);
288 printk(KERN_WARNING
"Unknown DWARF extension\n");
298 * dwarf_lookup_cie - locate the cie
299 * @cie_ptr: pointer to help with lookup
301 static struct dwarf_cie
*dwarf_lookup_cie(unsigned long cie_ptr
)
303 struct dwarf_cie
*cie
;
306 spin_lock_irqsave(&dwarf_cie_lock
, flags
);
309 * We've cached the last CIE we looked up because chances are
310 * that the FDE wants this CIE.
312 if (cached_cie
&& cached_cie
->cie_pointer
== cie_ptr
) {
317 list_for_each_entry(cie
, &dwarf_cie_list
, link
) {
318 if (cie
->cie_pointer
== cie_ptr
) {
324 /* Couldn't find the entry in the list. */
325 if (&cie
->link
== &dwarf_cie_list
)
328 spin_unlock_irqrestore(&dwarf_cie_lock
, flags
);
333 * dwarf_lookup_fde - locate the FDE that covers pc
334 * @pc: the program counter
336 struct dwarf_fde
*dwarf_lookup_fde(unsigned long pc
)
338 struct dwarf_fde
*fde
;
341 spin_lock_irqsave(&dwarf_fde_lock
, flags
);
343 list_for_each_entry(fde
, &dwarf_fde_list
, link
) {
344 unsigned long start
, end
;
346 start
= fde
->initial_location
;
347 end
= fde
->initial_location
+ fde
->address_range
;
349 if (pc
>= start
&& pc
< end
)
353 /* Couldn't find the entry in the list. */
354 if (&fde
->link
== &dwarf_fde_list
)
357 spin_unlock_irqrestore(&dwarf_fde_lock
, flags
);
363 * dwarf_cfa_execute_insns - execute instructions to calculate a CFA
364 * @insn_start: address of the first instruction
365 * @insn_end: address of the last instruction
366 * @cie: the CIE for this function
367 * @fde: the FDE for this function
368 * @frame: the instructions calculate the CFA for this frame
369 * @pc: the program counter of the address we're interested in
371 * Execute the Call Frame instruction sequence starting at
372 * @insn_start and ending at @insn_end. The instructions describe
373 * how to calculate the Canonical Frame Address of a stackframe.
374 * Store the results in @frame.
376 static int dwarf_cfa_execute_insns(unsigned char *insn_start
,
377 unsigned char *insn_end
,
378 struct dwarf_cie
*cie
,
379 struct dwarf_fde
*fde
,
380 struct dwarf_frame
*frame
,
384 unsigned char *current_insn
;
385 unsigned int count
, delta
, reg
, expr_len
, offset
;
386 struct dwarf_reg
*regp
;
388 current_insn
= insn_start
;
390 while (current_insn
< insn_end
&& frame
->pc
<= pc
) {
391 insn
= __raw_readb(current_insn
++);
394 * Firstly, handle the opcodes that embed their operands
395 * in the instructions.
397 switch (DW_CFA_opcode(insn
)) {
398 case DW_CFA_advance_loc
:
399 delta
= DW_CFA_operand(insn
);
400 delta
*= cie
->code_alignment_factor
;
405 reg
= DW_CFA_operand(insn
);
406 count
= dwarf_read_uleb128(current_insn
, &offset
);
407 current_insn
+= count
;
408 offset
*= cie
->data_alignment_factor
;
409 regp
= dwarf_frame_alloc_reg(frame
, reg
);
411 regp
->flags
|= DWARF_REG_OFFSET
;
415 reg
= DW_CFA_operand(insn
);
421 * Secondly, handle the opcodes that don't embed their
422 * operands in the instruction.
427 case DW_CFA_advance_loc1
:
428 delta
= *current_insn
++;
429 frame
->pc
+= delta
* cie
->code_alignment_factor
;
431 case DW_CFA_advance_loc2
:
432 delta
= get_unaligned((u16
*)current_insn
);
434 frame
->pc
+= delta
* cie
->code_alignment_factor
;
436 case DW_CFA_advance_loc4
:
437 delta
= get_unaligned((u32
*)current_insn
);
439 frame
->pc
+= delta
* cie
->code_alignment_factor
;
441 case DW_CFA_offset_extended
:
442 count
= dwarf_read_uleb128(current_insn
, ®
);
443 current_insn
+= count
;
444 count
= dwarf_read_uleb128(current_insn
, &offset
);
445 current_insn
+= count
;
446 offset
*= cie
->data_alignment_factor
;
448 case DW_CFA_restore_extended
:
449 count
= dwarf_read_uleb128(current_insn
, ®
);
450 current_insn
+= count
;
452 case DW_CFA_undefined
:
453 count
= dwarf_read_uleb128(current_insn
, ®
);
454 current_insn
+= count
;
457 count
= dwarf_read_uleb128(current_insn
,
458 &frame
->cfa_register
);
459 current_insn
+= count
;
460 count
= dwarf_read_uleb128(current_insn
,
462 current_insn
+= count
;
464 frame
->flags
|= DWARF_FRAME_CFA_REG_OFFSET
;
466 case DW_CFA_def_cfa_register
:
467 count
= dwarf_read_uleb128(current_insn
,
468 &frame
->cfa_register
);
469 current_insn
+= count
;
470 frame
->flags
|= DWARF_FRAME_CFA_REG_OFFSET
;
472 case DW_CFA_def_cfa_offset
:
473 count
= dwarf_read_uleb128(current_insn
, &offset
);
474 current_insn
+= count
;
475 frame
->cfa_offset
= offset
;
477 case DW_CFA_def_cfa_expression
:
478 count
= dwarf_read_uleb128(current_insn
, &expr_len
);
479 current_insn
+= count
;
481 frame
->cfa_expr
= current_insn
;
482 frame
->cfa_expr_len
= expr_len
;
483 current_insn
+= expr_len
;
485 frame
->flags
|= DWARF_FRAME_CFA_REG_EXP
;
487 case DW_CFA_offset_extended_sf
:
488 count
= dwarf_read_uleb128(current_insn
, ®
);
489 current_insn
+= count
;
490 count
= dwarf_read_leb128(current_insn
, &offset
);
491 current_insn
+= count
;
492 offset
*= cie
->data_alignment_factor
;
493 regp
= dwarf_frame_alloc_reg(frame
, reg
);
494 regp
->flags
|= DWARF_REG_OFFSET
;
497 case DW_CFA_val_offset
:
498 count
= dwarf_read_uleb128(current_insn
, ®
);
499 current_insn
+= count
;
500 count
= dwarf_read_leb128(current_insn
, &offset
);
501 offset
*= cie
->data_alignment_factor
;
502 regp
= dwarf_frame_alloc_reg(frame
, reg
);
503 regp
->flags
|= DWARF_VAL_OFFSET
;
506 case DW_CFA_GNU_args_size
:
507 count
= dwarf_read_uleb128(current_insn
, &offset
);
508 current_insn
+= count
;
510 case DW_CFA_GNU_negative_offset_extended
:
511 count
= dwarf_read_uleb128(current_insn
, ®
);
512 current_insn
+= count
;
513 count
= dwarf_read_uleb128(current_insn
, &offset
);
514 offset
*= cie
->data_alignment_factor
;
516 regp
= dwarf_frame_alloc_reg(frame
, reg
);
517 regp
->flags
|= DWARF_REG_OFFSET
;
518 regp
->addr
= -offset
;
521 pr_debug("unhandled DWARF instruction 0x%x\n", insn
);
530 * dwarf_unwind_stack - recursively unwind the stack
531 * @pc: address of the function to unwind
532 * @prev: struct dwarf_frame of the previous stackframe on the callstack
534 * Return a struct dwarf_frame representing the most recent frame
535 * on the callstack. Each of the lower (older) stack frames are
536 * linked via the "prev" member.
538 struct dwarf_frame
*dwarf_unwind_stack(unsigned long pc
,
539 struct dwarf_frame
*prev
)
541 struct dwarf_frame
*frame
;
542 struct dwarf_cie
*cie
;
543 struct dwarf_fde
*fde
;
544 struct dwarf_reg
*reg
;
548 * If this is the first invocation of this recursive function we
549 * need get the contents of a physical register to get the CFA
550 * in order to begin the virtual unwinding of the stack.
552 * NOTE: the return address is guaranteed to be setup by the
553 * time this function makes its first function call.
556 pc
= (unsigned long)current_text_addr();
558 frame
= mempool_alloc(dwarf_frame_pool
, GFP_ATOMIC
);
560 printk(KERN_ERR
"Unable to allocate a dwarf frame\n");
564 INIT_LIST_HEAD(&frame
->reg_list
);
567 frame
->return_addr
= 0;
569 fde
= dwarf_lookup_fde(pc
);
572 * This is our normal exit path - the one that stops the
573 * recursion. There's two reasons why we might exit
576 * a) pc has no asscociated DWARF frame info and so
577 * we don't know how to unwind this frame. This is
578 * usually the case when we're trying to unwind a
579 * frame that was called from some assembly code
580 * that has no DWARF info, e.g. syscalls.
582 * b) the DEBUG info for pc is bogus. There's
583 * really no way to distinguish this case from the
584 * case above, which sucks because we could print a
590 cie
= dwarf_lookup_cie(fde
->cie_pointer
);
592 frame
->pc
= fde
->initial_location
;
594 /* CIE initial instructions */
595 dwarf_cfa_execute_insns(cie
->initial_instructions
,
596 cie
->instructions_end
, cie
, fde
,
599 /* FDE instructions */
600 dwarf_cfa_execute_insns(fde
->instructions
, fde
->end
, cie
,
603 /* Calculate the CFA */
604 switch (frame
->flags
) {
605 case DWARF_FRAME_CFA_REG_OFFSET
:
607 reg
= dwarf_frame_reg(prev
, frame
->cfa_register
);
610 addr
= prev
->cfa
+ reg
->addr
;
611 frame
->cfa
= __raw_readl(addr
);
615 * Again, this is the first invocation of this
616 * recurisve function. We need to physically
617 * read the contents of a register in order to
618 * get the Canonical Frame Address for this
621 frame
->cfa
= dwarf_read_arch_reg(frame
->cfa_register
);
624 frame
->cfa
+= frame
->cfa_offset
;
630 /* If we haven't seen the return address reg, we're screwed. */
631 reg
= dwarf_frame_reg(frame
, DWARF_ARCH_RA_REG
);
634 addr
= frame
->cfa
+ reg
->addr
;
635 frame
->return_addr
= __raw_readl(addr
);
640 dwarf_frame_free_regs(frame
);
641 mempool_free(frame
, dwarf_frame_pool
);
645 static int dwarf_parse_cie(void *entry
, void *p
, unsigned long len
,
648 struct dwarf_cie
*cie
;
652 cie
= kzalloc(sizeof(*cie
), GFP_KERNEL
);
659 * Record the offset into the .eh_frame section
660 * for this CIE. It allows this CIE to be
661 * quickly and easily looked up from the
664 cie
->cie_pointer
= (unsigned long)entry
;
666 cie
->version
= *(char *)p
++;
667 BUG_ON(cie
->version
!= 1);
669 cie
->augmentation
= p
;
670 p
+= strlen(cie
->augmentation
) + 1;
672 count
= dwarf_read_uleb128(p
, &cie
->code_alignment_factor
);
675 count
= dwarf_read_leb128(p
, &cie
->data_alignment_factor
);
679 * Which column in the rule table contains the
682 if (cie
->version
== 1) {
683 cie
->return_address_reg
= __raw_readb(p
);
686 count
= dwarf_read_uleb128(p
, &cie
->return_address_reg
);
690 if (cie
->augmentation
[0] == 'z') {
691 unsigned int length
, count
;
692 cie
->flags
|= DWARF_CIE_Z_AUGMENTATION
;
694 count
= dwarf_read_uleb128(p
, &length
);
697 BUG_ON((unsigned char *)p
> end
);
699 cie
->initial_instructions
= p
+ length
;
703 while (*cie
->augmentation
) {
705 * "L" indicates a byte showing how the
706 * LSDA pointer is encoded. Skip it.
708 if (*cie
->augmentation
== 'L') {
711 } else if (*cie
->augmentation
== 'R') {
713 * "R" indicates a byte showing
714 * how FDE addresses are
717 cie
->encoding
= *(char *)p
++;
719 } else if (*cie
->augmentation
== 'P') {
721 * "R" indicates a personality
726 } else if (*cie
->augmentation
== 'S') {
730 * Unknown augmentation. Assume
733 p
= cie
->initial_instructions
;
739 cie
->initial_instructions
= p
;
740 cie
->instructions_end
= end
;
743 spin_lock_irqsave(&dwarf_cie_lock
, flags
);
744 list_add_tail(&cie
->link
, &dwarf_cie_list
);
745 spin_unlock_irqrestore(&dwarf_cie_lock
, flags
);
750 static int dwarf_parse_fde(void *entry
, u32 entry_type
,
751 void *start
, unsigned long len
)
753 struct dwarf_fde
*fde
;
754 struct dwarf_cie
*cie
;
759 fde
= kzalloc(sizeof(*fde
), GFP_KERNEL
);
766 * In a .eh_frame section the CIE pointer is the
767 * delta between the address within the FDE
769 fde
->cie_pointer
= (unsigned long)(p
- entry_type
- 4);
771 cie
= dwarf_lookup_cie(fde
->cie_pointer
);
775 count
= dwarf_read_encoded_value(p
, &fde
->initial_location
,
778 count
= dwarf_read_addr(p
, &fde
->initial_location
);
783 count
= dwarf_read_encoded_value(p
, &fde
->address_range
,
784 cie
->encoding
& 0x0f);
786 count
= dwarf_read_addr(p
, &fde
->address_range
);
790 if (fde
->cie
->flags
& DWARF_CIE_Z_AUGMENTATION
) {
792 count
= dwarf_read_uleb128(p
, &length
);
796 /* Call frame instructions. */
797 fde
->instructions
= p
;
798 fde
->end
= start
+ len
;
801 spin_lock_irqsave(&dwarf_fde_lock
, flags
);
802 list_add_tail(&fde
->link
, &dwarf_fde_list
);
803 spin_unlock_irqrestore(&dwarf_fde_lock
, flags
);
808 static void dwarf_unwinder_dump(struct task_struct
*task
, struct pt_regs
*regs
,
810 const struct stacktrace_ops
*ops
, void *data
)
812 struct dwarf_frame
*frame
, *_frame
;
813 unsigned long return_addr
;
819 frame
= dwarf_unwind_stack(return_addr
, _frame
);
822 dwarf_frame_free_regs(_frame
);
823 mempool_free(_frame
, dwarf_frame_pool
);
828 if (!frame
|| !frame
->return_addr
)
831 return_addr
= frame
->return_addr
;
832 ops
->address(data
, return_addr
, 1);
837 static struct unwinder dwarf_unwinder
= {
838 .name
= "dwarf-unwinder",
839 .dump
= dwarf_unwinder_dump
,
843 static void dwarf_unwinder_cleanup(void)
845 struct dwarf_cie
*cie
;
846 struct dwarf_fde
*fde
;
849 * Deallocate all the memory allocated for the DWARF unwinder.
850 * Traverse all the FDE/CIE lists and remove and free all the
851 * memory associated with those data structures.
853 list_for_each_entry(cie
, &dwarf_cie_list
, link
)
856 list_for_each_entry(fde
, &dwarf_fde_list
, link
)
859 kmem_cache_destroy(dwarf_reg_cachep
);
860 kmem_cache_destroy(dwarf_frame_cachep
);
864 * dwarf_unwinder_init - initialise the dwarf unwinder
866 * Build the data structures describing the .dwarf_frame section to
867 * make it easier to lookup CIE and FDE entries. Because the
868 * .eh_frame section is packed as tightly as possible it is not
869 * easy to lookup the FDE for a given PC, so we build a list of FDE
870 * and CIE entries that make it easier.
872 static int __init
dwarf_unwinder_init(void)
878 unsigned int c_entries
, f_entries
;
880 INIT_LIST_HEAD(&dwarf_cie_list
);
881 INIT_LIST_HEAD(&dwarf_fde_list
);
885 entry
= &__start_eh_frame
;
887 dwarf_frame_cachep
= kmem_cache_create("dwarf_frames",
888 sizeof(struct dwarf_frame
), 0, SLAB_PANIC
, NULL
);
889 dwarf_reg_cachep
= kmem_cache_create("dwarf_regs",
890 sizeof(struct dwarf_reg
), 0, SLAB_PANIC
, NULL
);
892 dwarf_frame_pool
= mempool_create(DWARF_FRAME_MIN_REQ
,
897 dwarf_reg_pool
= mempool_create(DWARF_REG_MIN_REQ
,
902 while ((char *)entry
< __stop_eh_frame
) {
905 count
= dwarf_entry_len(p
, &len
);
908 * We read a bogus length field value. There is
909 * nothing we can do here apart from disabling
910 * the DWARF unwinder. We can't even skip this
911 * entry and move to the next one because 'len'
912 * tells us where our next entry is.
918 /* initial length does not include itself */
921 entry_type
= get_unaligned((u32
*)p
);
924 if (entry_type
== DW_EH_FRAME_CIE
) {
925 err
= dwarf_parse_cie(entry
, p
, len
, end
);
931 err
= dwarf_parse_fde(entry
, entry_type
, p
, len
);
938 entry
= (char *)entry
+ len
+ 4;
941 printk(KERN_INFO
"DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
942 c_entries
, f_entries
);
944 err
= unwinder_register(&dwarf_unwinder
);
951 printk(KERN_ERR
"Failed to initialise DWARF unwinder: %d\n", err
);
952 dwarf_unwinder_cleanup();
955 early_initcall(dwarf_unwinder_init
);