1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18#include <linux/kernel.h>
19#include <linux/io.h>
20#include <linux/list.h>
21#include <linux/mempool.h>
22#include <linux/mm.h>
23#include <linux/ftrace.h>
24#include <asm/dwarf.h>
25#include <asm/unwinder.h>
26#include <asm/sections.h>
27#include <asm/unaligned.h>
28#include <asm/stacktrace.h>
29
30
31#define DWARF_FRAME_MIN_REQ 2
32
33#define DWARF_REG_MIN_REQ (DWARF_FRAME_MIN_REQ * 4)
34
35static struct kmem_cache *dwarf_frame_cachep;
36static mempool_t *dwarf_frame_pool;
37
38static struct kmem_cache *dwarf_reg_cachep;
39static mempool_t *dwarf_reg_pool;
40
41static LIST_HEAD(dwarf_cie_list);
42static DEFINE_SPINLOCK(dwarf_cie_lock);
43
44static LIST_HEAD(dwarf_fde_list);
45static DEFINE_SPINLOCK(dwarf_fde_lock);
46
47static struct dwarf_cie *cached_cie;
48
49
50
51
52
53
54
55
56
57
58
59
60static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
61 unsigned int reg_num)
62{
63 struct dwarf_reg *reg;
64
65 reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
66 if (!reg) {
67 printk(KERN_WARNING "Unable to allocate a DWARF register\n");
68
69
70
71
72 UNWINDER_BUG();
73 }
74
75 reg->number = reg_num;
76 reg->addr = 0;
77 reg->flags = 0;
78
79 list_add(®->link, &frame->reg_list);
80
81 return reg;
82}
83
84static void dwarf_frame_free_regs(struct dwarf_frame *frame)
85{
86 struct dwarf_reg *reg, *n;
87
88 list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
89 list_del(®->link);
90 mempool_free(reg, dwarf_reg_pool);
91 }
92}
93
94
95
96
97
98
99
100
101
102static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
103 unsigned int reg_num)
104{
105 struct dwarf_reg *reg;
106
107 list_for_each_entry(reg, &frame->reg_list, link) {
108 if (reg->number == reg_num)
109 return reg;
110 }
111
112 return NULL;
113}
114
115
116
117
118
119
120
121
122
123
124
125
126static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
127{
128 u32 val = get_unaligned(src);
129 put_unaligned(val, dst);
130 return sizeof(unsigned long *);
131}
132
133
134
135
136
137
138
139
140
141
142
143static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
144{
145 unsigned int result;
146 unsigned char byte;
147 int shift, count;
148
149 result = 0;
150 shift = 0;
151 count = 0;
152
153 while (1) {
154 byte = __raw_readb(addr);
155 addr++;
156 count++;
157
158 result |= (byte & 0x7f) << shift;
159 shift += 7;
160
161 if (!(byte & 0x80))
162 break;
163 }
164
165 *ret = result;
166
167 return count;
168}
169
170
171
172
173
174
175
176
177
178static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
179{
180 unsigned char byte;
181 int result, shift;
182 int num_bits;
183 int count;
184
185 result = 0;
186 shift = 0;
187 count = 0;
188
189 while (1) {
190 byte = __raw_readb(addr);
191 addr++;
192 result |= (byte & 0x7f) << shift;
193 shift += 7;
194 count++;
195
196 if (!(byte & 0x80))
197 break;
198 }
199
200
201 num_bits = 8 * sizeof(result);
202
203 if ((shift < num_bits) && (byte & 0x40))
204 result |= (-1 << shift);
205
206 *ret = result;
207
208 return count;
209}
210
211
212
213
214
215
216
217
218
219
220
221static int dwarf_read_encoded_value(char *addr, unsigned long *val,
222 char encoding)
223{
224 unsigned long decoded_addr = 0;
225 int count = 0;
226
227 switch (encoding & 0x70) {
228 case DW_EH_PE_absptr:
229 break;
230 case DW_EH_PE_pcrel:
231 decoded_addr = (unsigned long)addr;
232 break;
233 default:
234 pr_debug("encoding=0x%x\n", (encoding & 0x70));
235 UNWINDER_BUG();
236 }
237
238 if ((encoding & 0x07) == 0x00)
239 encoding |= DW_EH_PE_udata4;
240
241 switch (encoding & 0x0f) {
242 case DW_EH_PE_sdata4:
243 case DW_EH_PE_udata4:
244 count += 4;
245 decoded_addr += get_unaligned((u32 *)addr);
246 __raw_writel(decoded_addr, val);
247 break;
248 default:
249 pr_debug("encoding=0x%x\n", encoding);
250 UNWINDER_BUG();
251 }
252
253 return count;
254}
255
256
257
258
259
260
261
262
263
264
265static inline int dwarf_entry_len(char *addr, unsigned long *len)
266{
267 u32 initial_len;
268 int count;
269
270 initial_len = get_unaligned((u32 *)addr);
271 count = 4;
272
273
274
275
276
277
278
279 if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
280
281
282
283
284 if (initial_len == DW_EXT_DWARF64) {
285 *len = get_unaligned((u64 *)addr + 4);
286 count = 12;
287 } else {
288 printk(KERN_WARNING "Unknown DWARF extension\n");
289 count = 0;
290 }
291 } else
292 *len = initial_len;
293
294 return count;
295}
296
297
298
299
300
301static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
302{
303 struct dwarf_cie *cie;
304 unsigned long flags;
305
306 spin_lock_irqsave(&dwarf_cie_lock, flags);
307
308
309
310
311
312 if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
313 cie = cached_cie;
314 goto out;
315 }
316
317 list_for_each_entry(cie, &dwarf_cie_list, link) {
318 if (cie->cie_pointer == cie_ptr) {
319 cached_cie = cie;
320 break;
321 }
322 }
323
324
325 if (&cie->link == &dwarf_cie_list)
326 cie = NULL;
327out:
328 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
329 return cie;
330}
331
332
333
334
335
336struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
337{
338 struct dwarf_fde *fde;
339 unsigned long flags;
340
341 spin_lock_irqsave(&dwarf_fde_lock, flags);
342
343 list_for_each_entry(fde, &dwarf_fde_list, link) {
344 unsigned long start, end;
345
346 start = fde->initial_location;
347 end = fde->initial_location + fde->address_range;
348
349 if (pc >= start && pc < end)
350 break;
351 }
352
353
354 if (&fde->link == &dwarf_fde_list)
355 fde = NULL;
356
357 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
358
359 return fde;
360}
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376static 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,
381 unsigned long pc)
382{
383 unsigned char insn;
384 unsigned char *current_insn;
385 unsigned int count, delta, reg, expr_len, offset;
386 struct dwarf_reg *regp;
387
388 current_insn = insn_start;
389
390 while (current_insn < insn_end && frame->pc <= pc) {
391 insn = __raw_readb(current_insn++);
392
393
394
395
396
397 switch (DW_CFA_opcode(insn)) {
398 case DW_CFA_advance_loc:
399 delta = DW_CFA_operand(insn);
400 delta *= cie->code_alignment_factor;
401 frame->pc += delta;
402 continue;
403
404 case DW_CFA_offset:
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);
410 regp->addr = offset;
411 regp->flags |= DWARF_REG_OFFSET;
412 continue;
413
414 case DW_CFA_restore:
415 reg = DW_CFA_operand(insn);
416 continue;
417
418 }
419
420
421
422
423
424 switch (insn) {
425 case DW_CFA_nop:
426 continue;
427 case DW_CFA_advance_loc1:
428 delta = *current_insn++;
429 frame->pc += delta * cie->code_alignment_factor;
430 break;
431 case DW_CFA_advance_loc2:
432 delta = get_unaligned((u16 *)current_insn);
433 current_insn += 2;
434 frame->pc += delta * cie->code_alignment_factor;
435 break;
436 case DW_CFA_advance_loc4:
437 delta = get_unaligned((u32 *)current_insn);
438 current_insn += 4;
439 frame->pc += delta * cie->code_alignment_factor;
440 break;
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;
447 break;
448 case DW_CFA_restore_extended:
449 count = dwarf_read_uleb128(current_insn, ®);
450 current_insn += count;
451 break;
452 case DW_CFA_undefined:
453 count = dwarf_read_uleb128(current_insn, ®);
454 current_insn += count;
455 regp = dwarf_frame_alloc_reg(frame, reg);
456 regp->flags |= DWARF_UNDEFINED;
457 break;
458 case DW_CFA_def_cfa:
459 count = dwarf_read_uleb128(current_insn,
460 &frame->cfa_register);
461 current_insn += count;
462 count = dwarf_read_uleb128(current_insn,
463 &frame->cfa_offset);
464 current_insn += count;
465
466 frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
467 break;
468 case DW_CFA_def_cfa_register:
469 count = dwarf_read_uleb128(current_insn,
470 &frame->cfa_register);
471 current_insn += count;
472 frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
473 break;
474 case DW_CFA_def_cfa_offset:
475 count = dwarf_read_uleb128(current_insn, &offset);
476 current_insn += count;
477 frame->cfa_offset = offset;
478 break;
479 case DW_CFA_def_cfa_expression:
480 count = dwarf_read_uleb128(current_insn, &expr_len);
481 current_insn += count;
482
483 frame->cfa_expr = current_insn;
484 frame->cfa_expr_len = expr_len;
485 current_insn += expr_len;
486
487 frame->flags |= DWARF_FRAME_CFA_REG_EXP;
488 break;
489 case DW_CFA_offset_extended_sf:
490 count = dwarf_read_uleb128(current_insn, ®);
491 current_insn += count;
492 count = dwarf_read_leb128(current_insn, &offset);
493 current_insn += count;
494 offset *= cie->data_alignment_factor;
495 regp = dwarf_frame_alloc_reg(frame, reg);
496 regp->flags |= DWARF_REG_OFFSET;
497 regp->addr = offset;
498 break;
499 case DW_CFA_val_offset:
500 count = dwarf_read_uleb128(current_insn, ®);
501 current_insn += count;
502 count = dwarf_read_leb128(current_insn, &offset);
503 offset *= cie->data_alignment_factor;
504 regp = dwarf_frame_alloc_reg(frame, reg);
505 regp->flags |= DWARF_VAL_OFFSET;
506 regp->addr = offset;
507 break;
508 case DW_CFA_GNU_args_size:
509 count = dwarf_read_uleb128(current_insn, &offset);
510 current_insn += count;
511 break;
512 case DW_CFA_GNU_negative_offset_extended:
513 count = dwarf_read_uleb128(current_insn, ®);
514 current_insn += count;
515 count = dwarf_read_uleb128(current_insn, &offset);
516 offset *= cie->data_alignment_factor;
517
518 regp = dwarf_frame_alloc_reg(frame, reg);
519 regp->flags |= DWARF_REG_OFFSET;
520 regp->addr = -offset;
521 break;
522 default:
523 pr_debug("unhandled DWARF instruction 0x%x\n", insn);
524 UNWINDER_BUG();
525 break;
526 }
527 }
528
529 return 0;
530}
531
532
533
534
535
536
537
538
539
540
541struct dwarf_frame * dwarf_unwind_stack(unsigned long pc,
542 struct dwarf_frame *prev)
543{
544 struct dwarf_frame *frame;
545 struct dwarf_cie *cie;
546 struct dwarf_fde *fde;
547 struct dwarf_reg *reg;
548 unsigned long addr;
549
550
551
552
553
554
555
556
557
558 if (!pc || !prev)
559 pc = (unsigned long)current_text_addr();
560
561#ifdef CONFIG_FUNCTION_GRAPH_TRACER
562
563
564
565
566
567 if (pc == (unsigned long)&return_to_handler) {
568 int index = current->curr_ret_stack;
569
570
571
572
573
574
575
576 WARN_ON(index > 0);
577
578 pc = current->ret_stack[index].ret;
579 }
580#endif
581
582 frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
583 if (!frame) {
584 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
585 UNWINDER_BUG();
586 }
587
588 INIT_LIST_HEAD(&frame->reg_list);
589 frame->flags = 0;
590 frame->prev = prev;
591 frame->return_addr = 0;
592
593 fde = dwarf_lookup_fde(pc);
594 if (!fde) {
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611 goto bail;
612 }
613
614 cie = dwarf_lookup_cie(fde->cie_pointer);
615
616 frame->pc = fde->initial_location;
617
618
619 dwarf_cfa_execute_insns(cie->initial_instructions,
620 cie->instructions_end, cie, fde,
621 frame, pc);
622
623
624 dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
625 fde, frame, pc);
626
627
628 switch (frame->flags) {
629 case DWARF_FRAME_CFA_REG_OFFSET:
630 if (prev) {
631 reg = dwarf_frame_reg(prev, frame->cfa_register);
632 UNWINDER_BUG_ON(!reg);
633 UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
634
635 addr = prev->cfa + reg->addr;
636 frame->cfa = __raw_readl(addr);
637
638 } else {
639
640
641
642
643
644
645
646 frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
647 }
648
649 frame->cfa += frame->cfa_offset;
650 break;
651 default:
652 UNWINDER_BUG();
653 }
654
655 reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
656
657
658
659
660
661
662 if (!reg || reg->flags == DWARF_UNDEFINED)
663 goto bail;
664
665 UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
666
667 addr = frame->cfa + reg->addr;
668 frame->return_addr = __raw_readl(addr);
669
670 return frame;
671
672bail:
673 dwarf_frame_free_regs(frame);
674 mempool_free(frame, dwarf_frame_pool);
675 return NULL;
676}
677
678static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
679 unsigned char *end)
680{
681 struct dwarf_cie *cie;
682 unsigned long flags;
683 int count;
684
685 cie = kzalloc(sizeof(*cie), GFP_KERNEL);
686 if (!cie)
687 return -ENOMEM;
688
689 cie->length = len;
690
691
692
693
694
695
696
697 cie->cie_pointer = (unsigned long)entry;
698
699 cie->version = *(char *)p++;
700 UNWINDER_BUG_ON(cie->version != 1);
701
702 cie->augmentation = p;
703 p += strlen(cie->augmentation) + 1;
704
705 count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
706 p += count;
707
708 count = dwarf_read_leb128(p, &cie->data_alignment_factor);
709 p += count;
710
711
712
713
714
715 if (cie->version == 1) {
716 cie->return_address_reg = __raw_readb(p);
717 p++;
718 } else {
719 count = dwarf_read_uleb128(p, &cie->return_address_reg);
720 p += count;
721 }
722
723 if (cie->augmentation[0] == 'z') {
724 unsigned int length, count;
725 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
726
727 count = dwarf_read_uleb128(p, &length);
728 p += count;
729
730 UNWINDER_BUG_ON((unsigned char *)p > end);
731
732 cie->initial_instructions = p + length;
733 cie->augmentation++;
734 }
735
736 while (*cie->augmentation) {
737
738
739
740
741 if (*cie->augmentation == 'L') {
742 p++;
743 cie->augmentation++;
744 } else if (*cie->augmentation == 'R') {
745
746
747
748
749
750 cie->encoding = *(char *)p++;
751 cie->augmentation++;
752 } else if (*cie->augmentation == 'P') {
753
754
755
756
757
758 UNWINDER_BUG();
759 } else if (*cie->augmentation == 'S') {
760 UNWINDER_BUG();
761 } else {
762
763
764
765
766 p = cie->initial_instructions;
767 UNWINDER_BUG_ON(!p);
768 break;
769 }
770 }
771
772 cie->initial_instructions = p;
773 cie->instructions_end = end;
774
775
776 spin_lock_irqsave(&dwarf_cie_lock, flags);
777 list_add_tail(&cie->link, &dwarf_cie_list);
778 spin_unlock_irqrestore(&dwarf_cie_lock, flags);
779
780 return 0;
781}
782
783static int dwarf_parse_fde(void *entry, u32 entry_type,
784 void *start, unsigned long len,
785 unsigned char *end)
786{
787 struct dwarf_fde *fde;
788 struct dwarf_cie *cie;
789 unsigned long flags;
790 int count;
791 void *p = start;
792
793 fde = kzalloc(sizeof(*fde), GFP_KERNEL);
794 if (!fde)
795 return -ENOMEM;
796
797 fde->length = len;
798
799
800
801
802
803 fde->cie_pointer = (unsigned long)(p - entry_type - 4);
804
805 cie = dwarf_lookup_cie(fde->cie_pointer);
806 fde->cie = cie;
807
808 if (cie->encoding)
809 count = dwarf_read_encoded_value(p, &fde->initial_location,
810 cie->encoding);
811 else
812 count = dwarf_read_addr(p, &fde->initial_location);
813
814 p += count;
815
816 if (cie->encoding)
817 count = dwarf_read_encoded_value(p, &fde->address_range,
818 cie->encoding & 0x0f);
819 else
820 count = dwarf_read_addr(p, &fde->address_range);
821
822 p += count;
823
824 if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
825 unsigned int length;
826 count = dwarf_read_uleb128(p, &length);
827 p += count + length;
828 }
829
830
831 fde->instructions = p;
832 fde->end = end;
833
834
835 spin_lock_irqsave(&dwarf_fde_lock, flags);
836 list_add_tail(&fde->link, &dwarf_fde_list);
837 spin_unlock_irqrestore(&dwarf_fde_lock, flags);
838
839 return 0;
840}
841
842static void dwarf_unwinder_dump(struct task_struct *task,
843 struct pt_regs *regs,
844 unsigned long *sp,
845 const struct stacktrace_ops *ops,
846 void *data)
847{
848 struct dwarf_frame *frame, *_frame;
849 unsigned long return_addr;
850
851 _frame = NULL;
852 return_addr = 0;
853
854 while (1) {
855 frame = dwarf_unwind_stack(return_addr, _frame);
856
857 if (_frame) {
858 dwarf_frame_free_regs(_frame);
859 mempool_free(_frame, dwarf_frame_pool);
860 }
861
862 _frame = frame;
863
864 if (!frame || !frame->return_addr)
865 break;
866
867 return_addr = frame->return_addr;
868 ops->address(data, return_addr, 1);
869 }
870}
871
872static struct unwinder dwarf_unwinder = {
873 .name = "dwarf-unwinder",
874 .dump = dwarf_unwinder_dump,
875 .rating = 150,
876};
877
878static void dwarf_unwinder_cleanup(void)
879{
880 struct dwarf_cie *cie;
881 struct dwarf_fde *fde;
882
883
884
885
886
887
888 list_for_each_entry(cie, &dwarf_cie_list, link)
889 kfree(cie);
890
891 list_for_each_entry(fde, &dwarf_fde_list, link)
892 kfree(fde);
893
894 kmem_cache_destroy(dwarf_reg_cachep);
895 kmem_cache_destroy(dwarf_frame_cachep);
896}
897
898
899
900
901
902
903
904
905
906
907static int __init dwarf_unwinder_init(void)
908{
909 u32 entry_type;
910 void *p, *entry;
911 int count, err = 0;
912 unsigned long len;
913 unsigned int c_entries, f_entries;
914 unsigned char *end;
915 INIT_LIST_HEAD(&dwarf_cie_list);
916 INIT_LIST_HEAD(&dwarf_fde_list);
917
918 c_entries = 0;
919 f_entries = 0;
920 entry = &__start_eh_frame;
921
922 dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
923 sizeof(struct dwarf_frame), 0,
924 SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
925
926 dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
927 sizeof(struct dwarf_reg), 0,
928 SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
929
930 dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
931 mempool_alloc_slab,
932 mempool_free_slab,
933 dwarf_frame_cachep);
934
935 dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
936 mempool_alloc_slab,
937 mempool_free_slab,
938 dwarf_reg_cachep);
939
940 while ((char *)entry < __stop_eh_frame) {
941 p = entry;
942
943 count = dwarf_entry_len(p, &len);
944 if (count == 0) {
945
946
947
948
949
950
951
952 goto out;
953 } else
954 p += count;
955
956
957 end = p + len;
958
959 entry_type = get_unaligned((u32 *)p);
960 p += 4;
961
962 if (entry_type == DW_EH_FRAME_CIE) {
963 err = dwarf_parse_cie(entry, p, len, end);
964 if (err < 0)
965 goto out;
966 else
967 c_entries++;
968 } else {
969 err = dwarf_parse_fde(entry, entry_type, p, len, end);
970 if (err < 0)
971 goto out;
972 else
973 f_entries++;
974 }
975
976 entry = (char *)entry + len + 4;
977 }
978
979 printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
980 c_entries, f_entries);
981
982 err = unwinder_register(&dwarf_unwinder);
983 if (err)
984 goto out;
985
986 return 0;
987
988out:
989 printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
990 dwarf_unwinder_cleanup();
991 return -EINVAL;
992}
993early_initcall(dwarf_unwinder_init);
994