sh: unwinder: Convert frame allocations to GFP_ATOMIC.
[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  */
15
16 /* #define DEBUG */
17 #include <linux/kernel.h>
18 #include <linux/io.h>
19 #include <linux/list.h>
20 #include <linux/mm.h>
21 #include <asm/dwarf.h>
22 #include <asm/unwinder.h>
23 #include <asm/sections.h>
24 #include <asm/unaligned.h>
25 #include <asm/dwarf.h>
26 #include <asm/stacktrace.h>
27
28 static LIST_HEAD(dwarf_cie_list);
29 DEFINE_SPINLOCK(dwarf_cie_lock);
30
31 static LIST_HEAD(dwarf_fde_list);
32 DEFINE_SPINLOCK(dwarf_fde_lock);
33
34 static struct dwarf_cie *cached_cie;
35
36 /*
37  * Figure out whether we need to allocate some dwarf registers. If dwarf
38  * registers have already been allocated then we may need to realloc
39  * them. "reg" is a register number that we need to be able to access
40  * after this call.
41  *
42  * Register numbers start at zero, therefore we need to allocate space
43  * for "reg" + 1 registers.
44  */
45 static void dwarf_frame_alloc_regs(struct dwarf_frame *frame,
46                                    unsigned int reg)
47 {
48         struct dwarf_reg *regs;
49         unsigned int num_regs = reg + 1;
50         size_t new_size;
51         size_t old_size;
52
53         new_size = num_regs * sizeof(*regs);
54         old_size = frame->num_regs * sizeof(*regs);
55
56         /* Fast path: don't allocate any regs if we've already got enough. */
57         if (frame->num_regs >= num_regs)
58                 return;
59
60         regs = kzalloc(new_size, GFP_ATOMIC);
61         if (!regs) {
62                 printk(KERN_WARNING "Unable to allocate DWARF registers\n");
63                 /*
64                  * Let's just bomb hard here, we have no way to
65                  * gracefully recover.
66                  */
67                 BUG();
68         }
69
70         if (frame->regs) {
71                 memcpy(regs, frame->regs, old_size);
72                 kfree(frame->regs);
73         }
74
75         frame->regs = regs;
76         frame->num_regs = num_regs;
77 }
78
79 /**
80  *      dwarf_read_addr - read dwarf data
81  *      @src: source address of data
82  *      @dst: destination address to store the data to
83  *
84  *      Read 'n' bytes from @src, where 'n' is the size of an address on
85  *      the native machine. We return the number of bytes read, which
86  *      should always be 'n'. We also have to be careful when reading
87  *      from @src and writing to @dst, because they can be arbitrarily
88  *      aligned. Return 'n' - the number of bytes read.
89  */
90 static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
91 {
92         u32 val = get_unaligned(src);
93         put_unaligned(val, dst);
94         return sizeof(unsigned long *);
95 }
96
97 /**
98  *      dwarf_read_uleb128 - read unsigned LEB128 data
99  *      @addr: the address where the ULEB128 data is stored
100  *      @ret: address to store the result
101  *
102  *      Decode an unsigned LEB128 encoded datum. The algorithm is taken
103  *      from Appendix C of the DWARF 3 spec. For information on the
104  *      encodings refer to section "7.6 - Variable Length Data". Return
105  *      the number of bytes read.
106  */
107 static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
108 {
109         unsigned int result;
110         unsigned char byte;
111         int shift, count;
112
113         result = 0;
114         shift = 0;
115         count = 0;
116
117         while (1) {
118                 byte = __raw_readb(addr);
119                 addr++;
120                 count++;
121
122                 result |= (byte & 0x7f) << shift;
123                 shift += 7;
124
125                 if (!(byte & 0x80))
126                         break;
127         }
128
129         *ret = result;
130
131         return count;
132 }
133
134 /**
135  *      dwarf_read_leb128 - read signed LEB128 data
136  *      @addr: the address of the LEB128 encoded data
137  *      @ret: address to store the result
138  *
139  *      Decode signed LEB128 data. The algorithm is taken from Appendix
140  *      C of the DWARF 3 spec. Return the number of bytes read.
141  */
142 static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
143 {
144         unsigned char byte;
145         int result, shift;
146         int num_bits;
147         int count;
148
149         result = 0;
150         shift = 0;
151         count = 0;
152
153         while (1) {
154                 byte = __raw_readb(addr);
155                 addr++;
156                 result |= (byte & 0x7f) << shift;
157                 shift += 7;
158                 count++;
159
160                 if (!(byte & 0x80))
161                         break;
162         }
163
164         /* The number of bits in a signed integer. */
165         num_bits = 8 * sizeof(result);
166
167         if ((shift < num_bits) && (byte & 0x40))
168                 result |= (-1 << shift);
169
170         *ret = result;
171
172         return count;
173 }
174
175 /**
176  *      dwarf_read_encoded_value - return the decoded value at @addr
177  *      @addr: the address of the encoded value
178  *      @val: where to write the decoded value
179  *      @encoding: the encoding with which we can decode @addr
180  *
181  *      GCC emits encoded address in the .eh_frame FDE entries. Decode
182  *      the value at @addr using @encoding. The decoded value is written
183  *      to @val and the number of bytes read is returned.
184  */
185 static int dwarf_read_encoded_value(char *addr, unsigned long *val,
186                                     char encoding)
187 {
188         unsigned long decoded_addr = 0;
189         int count = 0;
190
191         switch (encoding & 0x70) {
192         case DW_EH_PE_absptr:
193                 break;
194         case DW_EH_PE_pcrel:
195                 decoded_addr = (unsigned long)addr;
196                 break;
197         default:
198                 pr_debug("encoding=0x%x\n", (encoding & 0x70));
199                 BUG();
200         }
201
202         if ((encoding & 0x07) == 0x00)
203                 encoding |= DW_EH_PE_udata4;
204
205         switch (encoding & 0x0f) {
206         case DW_EH_PE_sdata4:
207         case DW_EH_PE_udata4:
208                 count += 4;
209                 decoded_addr += get_unaligned((u32 *)addr);
210                 __raw_writel(decoded_addr, val);
211                 break;
212         default:
213                 pr_debug("encoding=0x%x\n", encoding);
214                 BUG();
215         }
216
217         return count;
218 }
219
220 /**
221  *      dwarf_entry_len - return the length of an FDE or CIE
222  *      @addr: the address of the entry
223  *      @len: the length of the entry
224  *
225  *      Read the initial_length field of the entry and store the size of
226  *      the entry in @len. We return the number of bytes read. Return a
227  *      count of 0 on error.
228  */
229 static inline int dwarf_entry_len(char *addr, unsigned long *len)
230 {
231         u32 initial_len;
232         int count;
233
234         initial_len = get_unaligned((u32 *)addr);
235         count = 4;
236
237         /*
238          * An initial length field value in the range DW_LEN_EXT_LO -
239          * DW_LEN_EXT_HI indicates an extension, and should not be
240          * interpreted as a length. The only extension that we currently
241          * understand is the use of DWARF64 addresses.
242          */
243         if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
244                 /*
245                  * The 64-bit length field immediately follows the
246                  * compulsory 32-bit length field.
247                  */
248                 if (initial_len == DW_EXT_DWARF64) {
249                         *len = get_unaligned((u64 *)addr + 4);
250                         count = 12;
251                 } else {
252                         printk(KERN_WARNING "Unknown DWARF extension\n");
253                         count = 0;
254                 }
255         } else
256                 *len = initial_len;
257
258         return count;
259 }
260
261 /**
262  *      dwarf_lookup_cie - locate the cie
263  *      @cie_ptr: pointer to help with lookup
264  */
265 static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
266 {
267         struct dwarf_cie *cie, *n;
268         unsigned long flags;
269
270         spin_lock_irqsave(&dwarf_cie_lock, flags);
271
272         /*
273          * We've cached the last CIE we looked up because chances are
274          * that the FDE wants this CIE.
275          */
276         if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
277                 cie = cached_cie;
278                 goto out;
279         }
280
281         list_for_each_entry_safe(cie, n, &dwarf_cie_list, link) {
282                 if (cie->cie_pointer == cie_ptr) {
283                         cached_cie = cie;
284                         break;
285                 }
286         }
287
288         /* Couldn't find the entry in the list. */
289         if (&cie->link == &dwarf_cie_list)
290                 cie = NULL;
291 out:
292         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
293         return cie;
294 }
295
296 /**
297  *      dwarf_lookup_fde - locate the FDE that covers pc
298  *      @pc: the program counter
299  */
300 struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
301 {
302         unsigned long flags;
303         struct dwarf_fde *fde, *n;
304
305         spin_lock_irqsave(&dwarf_fde_lock, flags);
306         list_for_each_entry_safe(fde, n, &dwarf_fde_list, link) {
307                 unsigned long start, end;
308
309                 start = fde->initial_location;
310                 end = fde->initial_location + fde->address_range;
311
312                 if (pc >= start && pc < end)
313                         break;
314         }
315
316         /* Couldn't find the entry in the list. */
317         if (&fde->link == &dwarf_fde_list)
318                 fde = NULL;
319
320         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
321
322         return fde;
323 }
324
325 /**
326  *      dwarf_cfa_execute_insns - execute instructions to calculate a CFA
327  *      @insn_start: address of the first instruction
328  *      @insn_end: address of the last instruction
329  *      @cie: the CIE for this function
330  *      @fde: the FDE for this function
331  *      @frame: the instructions calculate the CFA for this frame
332  *      @pc: the program counter of the address we're interested in
333  *      @define_ra: keep executing insns until the return addr reg is defined?
334  *
335  *      Execute the Call Frame instruction sequence starting at
336  *      @insn_start and ending at @insn_end. The instructions describe
337  *      how to calculate the Canonical Frame Address of a stackframe.
338  *      Store the results in @frame.
339  */
340 static int dwarf_cfa_execute_insns(unsigned char *insn_start,
341                                    unsigned char *insn_end,
342                                    struct dwarf_cie *cie,
343                                    struct dwarf_fde *fde,
344                                    struct dwarf_frame *frame,
345                                    unsigned long pc,
346                                    bool define_ra)
347 {
348         unsigned char insn;
349         unsigned char *current_insn;
350         unsigned int count, delta, reg, expr_len, offset;
351         bool seen_ra_reg;
352
353         current_insn = insn_start;
354
355         /*
356          * If we're executing instructions for the dwarf_unwind_stack()
357          * FDE we need to keep executing instructions until the value of
358          * DWARF_ARCH_RA_REG is defined. See the comment in
359          * dwarf_unwind_stack() for more details.
360          */
361         if (define_ra)
362                 seen_ra_reg = false;
363         else
364                 seen_ra_reg = true;
365
366         while (current_insn < insn_end && (frame->pc <= pc || !seen_ra_reg) ) {
367                 insn = __raw_readb(current_insn++);
368
369                 if (!seen_ra_reg) {
370                         if (frame->num_regs >= DWARF_ARCH_RA_REG &&
371                             frame->regs[DWARF_ARCH_RA_REG].flags)
372                                 seen_ra_reg = true;
373                 }
374
375                 /*
376                  * Firstly, handle the opcodes that embed their operands
377                  * in the instructions.
378                  */
379                 switch (DW_CFA_opcode(insn)) {
380                 case DW_CFA_advance_loc:
381                         delta = DW_CFA_operand(insn);
382                         delta *= cie->code_alignment_factor;
383                         frame->pc += delta;
384                         continue;
385                         /* NOTREACHED */
386                 case DW_CFA_offset:
387                         reg = DW_CFA_operand(insn);
388                         count = dwarf_read_uleb128(current_insn, &offset);
389                         current_insn += count;
390                         offset *= cie->data_alignment_factor;
391                         dwarf_frame_alloc_regs(frame, reg);
392                         frame->regs[reg].addr = offset;
393                         frame->regs[reg].flags |= DWARF_REG_OFFSET;
394                         continue;
395                         /* NOTREACHED */
396                 case DW_CFA_restore:
397                         reg = DW_CFA_operand(insn);
398                         continue;
399                         /* NOTREACHED */
400                 }
401
402                 /*
403                  * Secondly, handle the opcodes that don't embed their
404                  * operands in the instruction.
405                  */
406                 switch (insn) {
407                 case DW_CFA_nop:
408                         continue;
409                 case DW_CFA_advance_loc1:
410                         delta = *current_insn++;
411                         frame->pc += delta * cie->code_alignment_factor;
412                         break;
413                 case DW_CFA_advance_loc2:
414                         delta = get_unaligned((u16 *)current_insn);
415                         current_insn += 2;
416                         frame->pc += delta * cie->code_alignment_factor;
417                         break;
418                 case DW_CFA_advance_loc4:
419                         delta = get_unaligned((u32 *)current_insn);
420                         current_insn += 4;
421                         frame->pc += delta * cie->code_alignment_factor;
422                         break;
423                 case DW_CFA_offset_extended:
424                         count = dwarf_read_uleb128(current_insn, &reg);
425                         current_insn += count;
426                         count = dwarf_read_uleb128(current_insn, &offset);
427                         current_insn += count;
428                         offset *= cie->data_alignment_factor;
429                         break;
430                 case DW_CFA_restore_extended:
431                         count = dwarf_read_uleb128(current_insn, &reg);
432                         current_insn += count;
433                         break;
434                 case DW_CFA_undefined:
435                         count = dwarf_read_uleb128(current_insn, &reg);
436                         current_insn += count;
437                         break;
438                 case DW_CFA_def_cfa:
439                         count = dwarf_read_uleb128(current_insn,
440                                                    &frame->cfa_register);
441                         current_insn += count;
442                         count = dwarf_read_uleb128(current_insn,
443                                                    &frame->cfa_offset);
444                         current_insn += count;
445
446                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
447                         break;
448                 case DW_CFA_def_cfa_register:
449                         count = dwarf_read_uleb128(current_insn,
450                                                    &frame->cfa_register);
451                         current_insn += count;
452                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
453                         break;
454                 case DW_CFA_def_cfa_offset:
455                         count = dwarf_read_uleb128(current_insn, &offset);
456                         current_insn += count;
457                         frame->cfa_offset = offset;
458                         break;
459                 case DW_CFA_def_cfa_expression:
460                         count = dwarf_read_uleb128(current_insn, &expr_len);
461                         current_insn += count;
462
463                         frame->cfa_expr = current_insn;
464                         frame->cfa_expr_len = expr_len;
465                         current_insn += expr_len;
466
467                         frame->flags |= DWARF_FRAME_CFA_REG_EXP;
468                         break;
469                 case DW_CFA_offset_extended_sf:
470                         count = dwarf_read_uleb128(current_insn, &reg);
471                         current_insn += count;
472                         count = dwarf_read_leb128(current_insn, &offset);
473                         current_insn += count;
474                         offset *= cie->data_alignment_factor;
475                         dwarf_frame_alloc_regs(frame, reg);
476                         frame->regs[reg].flags |= DWARF_REG_OFFSET;
477                         frame->regs[reg].addr = offset;
478                         break;
479                 case DW_CFA_val_offset:
480                         count = dwarf_read_uleb128(current_insn, &reg);
481                         current_insn += count;
482                         count = dwarf_read_leb128(current_insn, &offset);
483                         offset *= cie->data_alignment_factor;
484                         frame->regs[reg].flags |= DWARF_REG_OFFSET;
485                         frame->regs[reg].addr = offset;
486                         break;
487                 default:
488                         pr_debug("unhandled DWARF instruction 0x%x\n", insn);
489                         break;
490                 }
491         }
492
493         return 0;
494 }
495
496 /**
497  *      dwarf_unwind_stack - recursively unwind the stack
498  *      @pc: address of the function to unwind
499  *      @prev: struct dwarf_frame of the previous stackframe on the callstack
500  *
501  *      Return a struct dwarf_frame representing the most recent frame
502  *      on the callstack. Each of the lower (older) stack frames are
503  *      linked via the "prev" member.
504  */
505 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
506                                        struct dwarf_frame *prev)
507 {
508         struct dwarf_frame *frame;
509         struct dwarf_cie *cie;
510         struct dwarf_fde *fde;
511         unsigned long addr;
512         int i, offset;
513         bool define_ra = false;
514
515         /*
516          * If this is the first invocation of this recursive function we
517          * need get the contents of a physical register to get the CFA
518          * in order to begin the virtual unwinding of the stack.
519          *
520          * Setting "define_ra" to true indictates that we want
521          * dwarf_cfa_execute_insns() to continue executing instructions
522          * until we know how to calculate the value of DWARF_ARCH_RA_REG
523          * (which we need in order to kick off the whole unwinding
524          * process).
525          *
526          * NOTE: the return address is guaranteed to be setup by the
527          * time this function makes its first function call.
528          */
529         if (!pc && !prev) {
530                 pc = (unsigned long)&dwarf_unwind_stack;
531                 define_ra = true;
532         }
533
534         frame = kzalloc(sizeof(*frame), GFP_ATOMIC);
535         if (!frame)
536                 return NULL;
537
538         frame->prev = prev;
539
540         fde = dwarf_lookup_fde(pc);
541         if (!fde) {
542                 /*
543                  * This is our normal exit path - the one that stops the
544                  * recursion. There's two reasons why we might exit
545                  * here,
546                  *
547                  *      a) pc has no asscociated DWARF frame info and so
548                  *      we don't know how to unwind this frame. This is
549                  *      usually the case when we're trying to unwind a
550                  *      frame that was called from some assembly code
551                  *      that has no DWARF info, e.g. syscalls.
552                  *
553                  *      b) the DEBUG info for pc is bogus. There's
554                  *      really no way to distinguish this case from the
555                  *      case above, which sucks because we could print a
556                  *      warning here.
557                  */
558                 return NULL;
559         }
560
561         cie = dwarf_lookup_cie(fde->cie_pointer);
562
563         frame->pc = fde->initial_location;
564
565         /* CIE initial instructions */
566         dwarf_cfa_execute_insns(cie->initial_instructions,
567                                 cie->instructions_end, cie, fde,
568                                 frame, pc, false);
569
570         /* FDE instructions */
571         dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
572                                 fde, frame, pc, define_ra);
573
574         /* Calculate the CFA */
575         switch (frame->flags) {
576         case DWARF_FRAME_CFA_REG_OFFSET:
577                 if (prev) {
578                         BUG_ON(!prev->regs[frame->cfa_register].flags);
579
580                         addr = prev->cfa;
581                         addr += prev->regs[frame->cfa_register].addr;
582                         frame->cfa = __raw_readl(addr);
583
584                 } else {
585                         /*
586                          * Again, this is the first invocation of this
587                          * recurisve function. We need to physically
588                          * read the contents of a register in order to
589                          * get the Canonical Frame Address for this
590                          * function.
591                          */
592                         frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
593                 }
594
595                 frame->cfa += frame->cfa_offset;
596                 break;
597         default:
598                 BUG();
599         }
600
601         /* If we haven't seen the return address reg, we're screwed. */
602         BUG_ON(!frame->regs[DWARF_ARCH_RA_REG].flags);
603
604         for (i = 0; i <= frame->num_regs; i++) {
605                 struct dwarf_reg *reg = &frame->regs[i];
606
607                 if (!reg->flags)
608                         continue;
609
610                 offset = reg->addr;
611                 offset += frame->cfa;
612         }
613
614         addr = frame->cfa + frame->regs[DWARF_ARCH_RA_REG].addr;
615         frame->return_addr = __raw_readl(addr);
616
617         frame->next = dwarf_unwind_stack(frame->return_addr, frame);
618         return frame;
619 }
620
621 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
622                            unsigned char *end)
623 {
624         struct dwarf_cie *cie;
625         unsigned long flags;
626         int count;
627
628         cie = kzalloc(sizeof(*cie), GFP_KERNEL);
629         if (!cie)
630                 return -ENOMEM;
631
632         cie->length = len;
633
634         /*
635          * Record the offset into the .eh_frame section
636          * for this CIE. It allows this CIE to be
637          * quickly and easily looked up from the
638          * corresponding FDE.
639          */
640         cie->cie_pointer = (unsigned long)entry;
641
642         cie->version = *(char *)p++;
643         BUG_ON(cie->version != 1);
644
645         cie->augmentation = p;
646         p += strlen(cie->augmentation) + 1;
647
648         count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
649         p += count;
650
651         count = dwarf_read_leb128(p, &cie->data_alignment_factor);
652         p += count;
653
654         /*
655          * Which column in the rule table contains the
656          * return address?
657          */
658         if (cie->version == 1) {
659                 cie->return_address_reg = __raw_readb(p);
660                 p++;
661         } else {
662                 count = dwarf_read_uleb128(p, &cie->return_address_reg);
663                 p += count;
664         }
665
666         if (cie->augmentation[0] == 'z') {
667                 unsigned int length, count;
668                 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
669
670                 count = dwarf_read_uleb128(p, &length);
671                 p += count;
672
673                 BUG_ON((unsigned char *)p > end);
674
675                 cie->initial_instructions = p + length;
676                 cie->augmentation++;
677         }
678
679         while (*cie->augmentation) {
680                 /*
681                  * "L" indicates a byte showing how the
682                  * LSDA pointer is encoded. Skip it.
683                  */
684                 if (*cie->augmentation == 'L') {
685                         p++;
686                         cie->augmentation++;
687                 } else if (*cie->augmentation == 'R') {
688                         /*
689                          * "R" indicates a byte showing
690                          * how FDE addresses are
691                          * encoded.
692                          */
693                         cie->encoding = *(char *)p++;
694                         cie->augmentation++;
695                 } else if (*cie->augmentation == 'P') {
696                         /*
697                          * "R" indicates a personality
698                          * routine in the CIE
699                          * augmentation.
700                          */
701                         BUG();
702                 } else if (*cie->augmentation == 'S') {
703                         BUG();
704                 } else {
705                         /*
706                          * Unknown augmentation. Assume
707                          * 'z' augmentation.
708                          */
709                         p = cie->initial_instructions;
710                         BUG_ON(!p);
711                         break;
712                 }
713         }
714
715         cie->initial_instructions = p;
716         cie->instructions_end = end;
717
718         /* Add to list */
719         spin_lock_irqsave(&dwarf_cie_lock, flags);
720         list_add_tail(&cie->link, &dwarf_cie_list);
721         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
722
723         return 0;
724 }
725
726 static int dwarf_parse_fde(void *entry, u32 entry_type,
727                            void *start, unsigned long len)
728 {
729         struct dwarf_fde *fde;
730         struct dwarf_cie *cie;
731         unsigned long flags;
732         int count;
733         void *p = start;
734
735         fde = kzalloc(sizeof(*fde), GFP_KERNEL);
736         if (!fde)
737                 return -ENOMEM;
738
739         fde->length = len;
740
741         /*
742          * In a .eh_frame section the CIE pointer is the
743          * delta between the address within the FDE
744          */
745         fde->cie_pointer = (unsigned long)(p - entry_type - 4);
746
747         cie = dwarf_lookup_cie(fde->cie_pointer);
748         fde->cie = cie;
749
750         if (cie->encoding)
751                 count = dwarf_read_encoded_value(p, &fde->initial_location,
752                                                  cie->encoding);
753         else
754                 count = dwarf_read_addr(p, &fde->initial_location);
755
756         p += count;
757
758         if (cie->encoding)
759                 count = dwarf_read_encoded_value(p, &fde->address_range,
760                                                  cie->encoding & 0x0f);
761         else
762                 count = dwarf_read_addr(p, &fde->address_range);
763
764         p += count;
765
766         if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
767                 unsigned int length;
768                 count = dwarf_read_uleb128(p, &length);
769                 p += count + length;
770         }
771
772         /* Call frame instructions. */
773         fde->instructions = p;
774         fde->end = start + len;
775
776         /* Add to list. */
777         spin_lock_irqsave(&dwarf_fde_lock, flags);
778         list_add_tail(&fde->link, &dwarf_fde_list);
779         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
780
781         return 0;
782 }
783
784 static void dwarf_unwinder_dump(struct task_struct *task, struct pt_regs *regs,
785                                 unsigned long *sp,
786                                 const struct stacktrace_ops *ops, void *data)
787 {
788         struct dwarf_frame *frame;
789
790         frame = dwarf_unwind_stack(0, NULL);
791
792         while (frame && frame->return_addr) {
793                 ops->address(data, frame->return_addr, 1);
794                 frame = frame->next;
795         }
796 }
797
798 static struct unwinder dwarf_unwinder = {
799         .name = "dwarf-unwinder",
800         .dump = dwarf_unwinder_dump,
801         .rating = 150,
802 };
803
804 static void dwarf_unwinder_cleanup(void)
805 {
806         struct dwarf_cie *cie, *m;
807         struct dwarf_fde *fde, *n;
808         unsigned long flags;
809
810         /*
811          * Deallocate all the memory allocated for the DWARF unwinder.
812          * Traverse all the FDE/CIE lists and remove and free all the
813          * memory associated with those data structures.
814          */
815         spin_lock_irqsave(&dwarf_cie_lock, flags);
816         list_for_each_entry_safe(cie, m, &dwarf_cie_list, link)
817                 kfree(cie);
818         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
819
820         spin_lock_irqsave(&dwarf_fde_lock, flags);
821         list_for_each_entry_safe(fde, n, &dwarf_fde_list, link)
822                 kfree(fde);
823         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
824 }
825
826 /**
827  *      dwarf_unwinder_init - initialise the dwarf unwinder
828  *
829  *      Build the data structures describing the .dwarf_frame section to
830  *      make it easier to lookup CIE and FDE entries. Because the
831  *      .eh_frame section is packed as tightly as possible it is not
832  *      easy to lookup the FDE for a given PC, so we build a list of FDE
833  *      and CIE entries that make it easier.
834  */
835 void dwarf_unwinder_init(void)
836 {
837         u32 entry_type;
838         void *p, *entry;
839         int count, err;
840         unsigned long len;
841         unsigned int c_entries, f_entries;
842         unsigned char *end;
843         INIT_LIST_HEAD(&dwarf_cie_list);
844         INIT_LIST_HEAD(&dwarf_fde_list);
845
846         c_entries = 0;
847         f_entries = 0;
848         entry = &__start_eh_frame;
849
850         while ((char *)entry < __stop_eh_frame) {
851                 p = entry;
852
853                 count = dwarf_entry_len(p, &len);
854                 if (count == 0) {
855                         /*
856                          * We read a bogus length field value. There is
857                          * nothing we can do here apart from disabling
858                          * the DWARF unwinder. We can't even skip this
859                          * entry and move to the next one because 'len'
860                          * tells us where our next entry is.
861                          */
862                         goto out;
863                 } else
864                         p += count;
865
866                 /* initial length does not include itself */
867                 end = p + len;
868
869                 entry_type = get_unaligned((u32 *)p);
870                 p += 4;
871
872                 if (entry_type == DW_EH_FRAME_CIE) {
873                         err = dwarf_parse_cie(entry, p, len, end);
874                         if (err < 0)
875                                 goto out;
876                         else
877                                 c_entries++;
878                 } else {
879                         err = dwarf_parse_fde(entry, entry_type, p, len);
880                         if (err < 0)
881                                 goto out;
882                         else
883                                 f_entries++;
884                 }
885
886                 entry = (char *)entry + len + 4;
887         }
888
889         printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
890                c_entries, f_entries);
891
892         err = unwinder_register(&dwarf_unwinder);
893         if (err)
894                 goto out;
895
896         return;
897
898 out:
899         printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
900         dwarf_unwinder_cleanup();
901 }