sh: unwinder: Set the flags for DW_CFA_val_offset ops as DWARF_VAL_OFFSET
[linux-2.6.git] / arch / sh / kernel / dwarf.c
1 /*
2  * Copyright (C) 2009 Matt Fleming <matt@console-pimps.org>
3  *
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
6  * for more details.
7  *
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.
11  *
12  * TODO:
13  *      - DWARF64 doesn't work.
14  *      - Registers with DWARF_VAL_OFFSET rules aren't handled properly.
15  */
16
17 /* #define DEBUG */
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 <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>
29
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)
34
35 static struct kmem_cache *dwarf_frame_cachep;
36 static mempool_t *dwarf_frame_pool;
37
38 static struct kmem_cache *dwarf_reg_cachep;
39 static mempool_t *dwarf_reg_pool;
40
41 static LIST_HEAD(dwarf_cie_list);
42 static DEFINE_SPINLOCK(dwarf_cie_lock);
43
44 static LIST_HEAD(dwarf_fde_list);
45 static DEFINE_SPINLOCK(dwarf_fde_lock);
46
47 static struct dwarf_cie *cached_cie;
48
49 /**
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
53  *
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.
57  *
58  *      Return the initialised DWARF reg.
59  */
60 static 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                  * Let's just bomb hard here, we have no way to
70                  * gracefully recover.
71                  */
72                 BUG();
73         }
74
75         reg->number = reg_num;
76         reg->addr = 0;
77         reg->flags = 0;
78
79         list_add(&reg->link, &frame->reg_list);
80
81         return reg;
82 }
83
84 static 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(&reg->link);
90                 mempool_free(reg, dwarf_reg_pool);
91         }
92 }
93
94 /**
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
98  *
99  *      Lookup and return the dwarf reg @reg_num for this frame. Return
100  *      NULL if @reg_num is an register invalid number.
101  */
102 static 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  *      dwarf_read_addr - read dwarf data
117  *      @src: source address of data
118  *      @dst: destination address to store the data to
119  *
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.
125  */
126 static 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  *      dwarf_read_uleb128 - read unsigned LEB128 data
135  *      @addr: the address where the ULEB128 data is stored
136  *      @ret: address to store the result
137  *
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.
142  */
143 static 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  *      dwarf_read_leb128 - read signed LEB128 data
172  *      @addr: the address of the LEB128 encoded data
173  *      @ret: address to store the result
174  *
175  *      Decode signed LEB128 data. The algorithm is taken from Appendix
176  *      C of the DWARF 3 spec. Return the number of bytes read.
177  */
178 static 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         /* The number of bits in a signed integer. */
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  *      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
216  *
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.
220  */
221 static 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                 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                 BUG();
251         }
252
253         return count;
254 }
255
256 /**
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
260  *
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.
264  */
265 static 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          * 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.
278          */
279         if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
280                 /*
281                  * The 64-bit length field immediately follows the
282                  * compulsory 32-bit length field.
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  *      dwarf_lookup_cie - locate the cie
299  *      @cie_ptr: pointer to help with lookup
300  */
301 static 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          * We've cached the last CIE we looked up because chances are
310          * that the FDE wants this CIE.
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         /* Couldn't find the entry in the list. */
325         if (&cie->link == &dwarf_cie_list)
326                 cie = NULL;
327 out:
328         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
329         return cie;
330 }
331
332 /**
333  *      dwarf_lookup_fde - locate the FDE that covers pc
334  *      @pc: the program counter
335  */
336 struct 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         /* Couldn't find the entry in the list. */
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  *      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
370  *
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.
375  */
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,
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                  * Firstly, handle the opcodes that embed their operands
395                  * in the instructions.
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                         /* NOTREACHED */
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                         /* NOTREACHED */
414                 case DW_CFA_restore:
415                         reg = DW_CFA_operand(insn);
416                         continue;
417                         /* NOTREACHED */
418                 }
419
420                 /*
421                  * Secondly, handle the opcodes that don't embed their
422                  * operands in the instruction.
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, &reg);
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, &reg);
450                         current_insn += count;
451                         break;
452                 case DW_CFA_undefined:
453                         count = dwarf_read_uleb128(current_insn, &reg);
454                         current_insn += count;
455                         break;
456                 case DW_CFA_def_cfa:
457                         count = dwarf_read_uleb128(current_insn,
458                                                    &frame->cfa_register);
459                         current_insn += count;
460                         count = dwarf_read_uleb128(current_insn,
461                                                    &frame->cfa_offset);
462                         current_insn += count;
463
464                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
465                         break;
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;
471                         break;
472                 case DW_CFA_def_cfa_offset:
473                         count = dwarf_read_uleb128(current_insn, &offset);
474                         current_insn += count;
475                         frame->cfa_offset = offset;
476                         break;
477                 case DW_CFA_def_cfa_expression:
478                         count = dwarf_read_uleb128(current_insn, &expr_len);
479                         current_insn += count;
480
481                         frame->cfa_expr = current_insn;
482                         frame->cfa_expr_len = expr_len;
483                         current_insn += expr_len;
484
485                         frame->flags |= DWARF_FRAME_CFA_REG_EXP;
486                         break;
487                 case DW_CFA_offset_extended_sf:
488                         count = dwarf_read_uleb128(current_insn, &reg);
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;
495                         regp->addr = offset;
496                         break;
497                 case DW_CFA_val_offset:
498                         count = dwarf_read_uleb128(current_insn, &reg);
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;
504                         regp->addr = offset;
505                         break;
506                 case DW_CFA_GNU_args_size:
507                         count = dwarf_read_uleb128(current_insn, &offset);
508                         current_insn += count;
509                         break;
510                 case DW_CFA_GNU_negative_offset_extended:
511                         count = dwarf_read_uleb128(current_insn, &reg);
512                         current_insn += count;
513                         count = dwarf_read_uleb128(current_insn, &offset);
514                         offset *= cie->data_alignment_factor;
515
516                         regp = dwarf_frame_alloc_reg(frame, reg);
517                         regp->flags |= DWARF_REG_OFFSET;
518                         regp->addr = -offset;
519                         break;
520                 default:
521                         pr_debug("unhandled DWARF instruction 0x%x\n", insn);
522                         break;
523                 }
524         }
525
526         return 0;
527 }
528
529 /**
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
533  *
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.
537  */
538 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
539                                        struct dwarf_frame *prev)
540 {
541         struct dwarf_frame *frame;
542         struct dwarf_cie *cie;
543         struct dwarf_fde *fde;
544         struct dwarf_reg *reg;
545         unsigned long addr;
546
547         /*
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.
551          *
552          * NOTE: the return address is guaranteed to be setup by the
553          * time this function makes its first function call.
554          */
555         if (!pc && !prev)
556                 pc = (unsigned long)current_text_addr();
557
558         frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
559         if (!frame) {
560                 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
561                 BUG();
562         }
563
564         INIT_LIST_HEAD(&frame->reg_list);
565         frame->flags = 0;
566         frame->prev = prev;
567         frame->return_addr = 0;
568
569         fde = dwarf_lookup_fde(pc);
570         if (!fde) {
571                 /*
572                  * This is our normal exit path - the one that stops the
573                  * recursion. There's two reasons why we might exit
574                  * here,
575                  *
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.
581                  *
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
585                  *      warning here.
586                  */
587                 goto bail;
588         }
589
590         cie = dwarf_lookup_cie(fde->cie_pointer);
591
592         frame->pc = fde->initial_location;
593
594         /* CIE initial instructions */
595         dwarf_cfa_execute_insns(cie->initial_instructions,
596                                 cie->instructions_end, cie, fde,
597                                 frame, pc);
598
599         /* FDE instructions */
600         dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
601                                 fde, frame, pc);
602
603         /* Calculate the CFA */
604         switch (frame->flags) {
605         case DWARF_FRAME_CFA_REG_OFFSET:
606                 if (prev) {
607                         reg = dwarf_frame_reg(prev, frame->cfa_register);
608                         BUG_ON(!reg);
609
610                         addr = prev->cfa + reg->addr;
611                         frame->cfa = __raw_readl(addr);
612
613                 } else {
614                         /*
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
619                          * function.
620                          */
621                         frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
622                 }
623
624                 frame->cfa += frame->cfa_offset;
625                 break;
626         default:
627                 BUG();
628         }
629
630         /* If we haven't seen the return address reg, we're screwed. */
631         reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
632         BUG_ON(!reg);
633
634         addr = frame->cfa + reg->addr;
635         frame->return_addr = __raw_readl(addr);
636
637         return frame;
638
639 bail:
640         dwarf_frame_free_regs(frame);
641         mempool_free(frame, dwarf_frame_pool);
642         return NULL;
643 }
644
645 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
646                            unsigned char *end)
647 {
648         struct dwarf_cie *cie;
649         unsigned long flags;
650         int count;
651
652         cie = kzalloc(sizeof(*cie), GFP_KERNEL);
653         if (!cie)
654                 return -ENOMEM;
655
656         cie->length = len;
657
658         /*
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
662          * corresponding FDE.
663          */
664         cie->cie_pointer = (unsigned long)entry;
665
666         cie->version = *(char *)p++;
667         BUG_ON(cie->version != 1);
668
669         cie->augmentation = p;
670         p += strlen(cie->augmentation) + 1;
671
672         count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
673         p += count;
674
675         count = dwarf_read_leb128(p, &cie->data_alignment_factor);
676         p += count;
677
678         /*
679          * Which column in the rule table contains the
680          * return address?
681          */
682         if (cie->version == 1) {
683                 cie->return_address_reg = __raw_readb(p);
684                 p++;
685         } else {
686                 count = dwarf_read_uleb128(p, &cie->return_address_reg);
687                 p += count;
688         }
689
690         if (cie->augmentation[0] == 'z') {
691                 unsigned int length, count;
692                 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
693
694                 count = dwarf_read_uleb128(p, &length);
695                 p += count;
696
697                 BUG_ON((unsigned char *)p > end);
698
699                 cie->initial_instructions = p + length;
700                 cie->augmentation++;
701         }
702
703         while (*cie->augmentation) {
704                 /*
705                  * "L" indicates a byte showing how the
706                  * LSDA pointer is encoded. Skip it.
707                  */
708                 if (*cie->augmentation == 'L') {
709                         p++;
710                         cie->augmentation++;
711                 } else if (*cie->augmentation == 'R') {
712                         /*
713                          * "R" indicates a byte showing
714                          * how FDE addresses are
715                          * encoded.
716                          */
717                         cie->encoding = *(char *)p++;
718                         cie->augmentation++;
719                 } else if (*cie->augmentation == 'P') {
720                         /*
721                          * "R" indicates a personality
722                          * routine in the CIE
723                          * augmentation.
724                          */
725                         BUG();
726                 } else if (*cie->augmentation == 'S') {
727                         BUG();
728                 } else {
729                         /*
730                          * Unknown augmentation. Assume
731                          * 'z' augmentation.
732                          */
733                         p = cie->initial_instructions;
734                         BUG_ON(!p);
735                         break;
736                 }
737         }
738
739         cie->initial_instructions = p;
740         cie->instructions_end = end;
741
742         /* Add to list */
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);
746
747         return 0;
748 }
749
750 static int dwarf_parse_fde(void *entry, u32 entry_type,
751                            void *start, unsigned long len)
752 {
753         struct dwarf_fde *fde;
754         struct dwarf_cie *cie;
755         unsigned long flags;
756         int count;
757         void *p = start;
758
759         fde = kzalloc(sizeof(*fde), GFP_KERNEL);
760         if (!fde)
761                 return -ENOMEM;
762
763         fde->length = len;
764
765         /*
766          * In a .eh_frame section the CIE pointer is the
767          * delta between the address within the FDE
768          */
769         fde->cie_pointer = (unsigned long)(p - entry_type - 4);
770
771         cie = dwarf_lookup_cie(fde->cie_pointer);
772         fde->cie = cie;
773
774         if (cie->encoding)
775                 count = dwarf_read_encoded_value(p, &fde->initial_location,
776                                                  cie->encoding);
777         else
778                 count = dwarf_read_addr(p, &fde->initial_location);
779
780         p += count;
781
782         if (cie->encoding)
783                 count = dwarf_read_encoded_value(p, &fde->address_range,
784                                                  cie->encoding & 0x0f);
785         else
786                 count = dwarf_read_addr(p, &fde->address_range);
787
788         p += count;
789
790         if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
791                 unsigned int length;
792                 count = dwarf_read_uleb128(p, &length);
793                 p += count + length;
794         }
795
796         /* Call frame instructions. */
797         fde->instructions = p;
798         fde->end = start + len;
799
800         /* Add to list. */
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);
804
805         return 0;
806 }
807
808 static void dwarf_unwinder_dump(struct task_struct *task, struct pt_regs *regs,
809                                 unsigned long *sp,
810                                 const struct stacktrace_ops *ops, void *data)
811 {
812         struct dwarf_frame *frame, *_frame;
813         unsigned long return_addr;
814
815         _frame = NULL;
816         return_addr = 0;
817
818         while (1) {
819                 frame = dwarf_unwind_stack(return_addr, _frame);
820
821                 if (_frame) {
822                         dwarf_frame_free_regs(_frame);
823                         mempool_free(_frame, dwarf_frame_pool);
824                 }
825
826                 _frame = frame;
827
828                 if (!frame || !frame->return_addr)
829                         break;
830
831                 return_addr = frame->return_addr;
832                 ops->address(data, return_addr, 1);
833         }
834
835 }
836
837 static struct unwinder dwarf_unwinder = {
838         .name = "dwarf-unwinder",
839         .dump = dwarf_unwinder_dump,
840         .rating = 150,
841 };
842
843 static void dwarf_unwinder_cleanup(void)
844 {
845         struct dwarf_cie *cie;
846         struct dwarf_fde *fde;
847
848         /*
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.
852          */
853         list_for_each_entry(cie, &dwarf_cie_list, link)
854                 kfree(cie);
855
856         list_for_each_entry(fde, &dwarf_fde_list, link)
857                 kfree(fde);
858
859         kmem_cache_destroy(dwarf_reg_cachep);
860         kmem_cache_destroy(dwarf_frame_cachep);
861 }
862
863 /**
864  *      dwarf_unwinder_init - initialise the dwarf unwinder
865  *
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.
871  */
872 static int __init dwarf_unwinder_init(void)
873 {
874         u32 entry_type;
875         void *p, *entry;
876         int count, err;
877         unsigned long len;
878         unsigned int c_entries, f_entries;
879         unsigned char *end;
880         INIT_LIST_HEAD(&dwarf_cie_list);
881         INIT_LIST_HEAD(&dwarf_fde_list);
882
883         c_entries = 0;
884         f_entries = 0;
885         entry = &__start_eh_frame;
886
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);
891
892         dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
893                                           mempool_alloc_slab,
894                                           mempool_free_slab,
895                                           dwarf_frame_cachep);
896
897         dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
898                                          mempool_alloc_slab,
899                                          mempool_free_slab,
900                                          dwarf_reg_cachep);
901
902         while ((char *)entry < __stop_eh_frame) {
903                 p = entry;
904
905                 count = dwarf_entry_len(p, &len);
906                 if (count == 0) {
907                         /*
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.
913                          */
914                         goto out;
915                 } else
916                         p += count;
917
918                 /* initial length does not include itself */
919                 end = p + len;
920
921                 entry_type = get_unaligned((u32 *)p);
922                 p += 4;
923
924                 if (entry_type == DW_EH_FRAME_CIE) {
925                         err = dwarf_parse_cie(entry, p, len, end);
926                         if (err < 0)
927                                 goto out;
928                         else
929                                 c_entries++;
930                 } else {
931                         err = dwarf_parse_fde(entry, entry_type, p, len);
932                         if (err < 0)
933                                 goto out;
934                         else
935                                 f_entries++;
936                 }
937
938                 entry = (char *)entry + len + 4;
939         }
940
941         printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
942                c_entries, f_entries);
943
944         err = unwinder_register(&dwarf_unwinder);
945         if (err)
946                 goto out;
947
948         return 0;
949
950 out:
951         printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
952         dwarf_unwinder_cleanup();
953         return -EINVAL;
954 }
955 early_initcall(dwarf_unwinder_init);