include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit...
[linux-3.10.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 <linux/elf.h>
24 #include <linux/ftrace.h>
25 #include <linux/slab.h>
26 #include <asm/dwarf.h>
27 #include <asm/unwinder.h>
28 #include <asm/sections.h>
29 #include <asm/unaligned.h>
30 #include <asm/stacktrace.h>
31
32 /* Reserve enough memory for two stack frames */
33 #define DWARF_FRAME_MIN_REQ     2
34 /* ... with 4 registers per frame. */
35 #define DWARF_REG_MIN_REQ       (DWARF_FRAME_MIN_REQ * 4)
36
37 static struct kmem_cache *dwarf_frame_cachep;
38 static mempool_t *dwarf_frame_pool;
39
40 static struct kmem_cache *dwarf_reg_cachep;
41 static mempool_t *dwarf_reg_pool;
42
43 static struct rb_root cie_root;
44 static DEFINE_SPINLOCK(dwarf_cie_lock);
45
46 static struct rb_root fde_root;
47 static DEFINE_SPINLOCK(dwarf_fde_lock);
48
49 static struct dwarf_cie *cached_cie;
50
51 /**
52  *      dwarf_frame_alloc_reg - allocate memory for a DWARF register
53  *      @frame: the DWARF frame whose list of registers we insert on
54  *      @reg_num: the register number
55  *
56  *      Allocate space for, and initialise, a dwarf reg from
57  *      dwarf_reg_pool and insert it onto the (unsorted) linked-list of
58  *      dwarf registers for @frame.
59  *
60  *      Return the initialised DWARF reg.
61  */
62 static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
63                                                unsigned int reg_num)
64 {
65         struct dwarf_reg *reg;
66
67         reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
68         if (!reg) {
69                 printk(KERN_WARNING "Unable to allocate a DWARF register\n");
70                 /*
71                  * Let's just bomb hard here, we have no way to
72                  * gracefully recover.
73                  */
74                 UNWINDER_BUG();
75         }
76
77         reg->number = reg_num;
78         reg->addr = 0;
79         reg->flags = 0;
80
81         list_add(&reg->link, &frame->reg_list);
82
83         return reg;
84 }
85
86 static void dwarf_frame_free_regs(struct dwarf_frame *frame)
87 {
88         struct dwarf_reg *reg, *n;
89
90         list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
91                 list_del(&reg->link);
92                 mempool_free(reg, dwarf_reg_pool);
93         }
94 }
95
96 /**
97  *      dwarf_frame_reg - return a DWARF register
98  *      @frame: the DWARF frame to search in for @reg_num
99  *      @reg_num: the register number to search for
100  *
101  *      Lookup and return the dwarf reg @reg_num for this frame. Return
102  *      NULL if @reg_num is an register invalid number.
103  */
104 static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
105                                          unsigned int reg_num)
106 {
107         struct dwarf_reg *reg;
108
109         list_for_each_entry(reg, &frame->reg_list, link) {
110                 if (reg->number == reg_num)
111                         return reg;
112         }
113
114         return NULL;
115 }
116
117 /**
118  *      dwarf_read_addr - read dwarf data
119  *      @src: source address of data
120  *      @dst: destination address to store the data to
121  *
122  *      Read 'n' bytes from @src, where 'n' is the size of an address on
123  *      the native machine. We return the number of bytes read, which
124  *      should always be 'n'. We also have to be careful when reading
125  *      from @src and writing to @dst, because they can be arbitrarily
126  *      aligned. Return 'n' - the number of bytes read.
127  */
128 static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
129 {
130         u32 val = get_unaligned(src);
131         put_unaligned(val, dst);
132         return sizeof(unsigned long *);
133 }
134
135 /**
136  *      dwarf_read_uleb128 - read unsigned LEB128 data
137  *      @addr: the address where the ULEB128 data is stored
138  *      @ret: address to store the result
139  *
140  *      Decode an unsigned LEB128 encoded datum. The algorithm is taken
141  *      from Appendix C of the DWARF 3 spec. For information on the
142  *      encodings refer to section "7.6 - Variable Length Data". Return
143  *      the number of bytes read.
144  */
145 static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
146 {
147         unsigned int result;
148         unsigned char byte;
149         int shift, count;
150
151         result = 0;
152         shift = 0;
153         count = 0;
154
155         while (1) {
156                 byte = __raw_readb(addr);
157                 addr++;
158                 count++;
159
160                 result |= (byte & 0x7f) << shift;
161                 shift += 7;
162
163                 if (!(byte & 0x80))
164                         break;
165         }
166
167         *ret = result;
168
169         return count;
170 }
171
172 /**
173  *      dwarf_read_leb128 - read signed LEB128 data
174  *      @addr: the address of the LEB128 encoded data
175  *      @ret: address to store the result
176  *
177  *      Decode signed LEB128 data. The algorithm is taken from Appendix
178  *      C of the DWARF 3 spec. Return the number of bytes read.
179  */
180 static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
181 {
182         unsigned char byte;
183         int result, shift;
184         int num_bits;
185         int count;
186
187         result = 0;
188         shift = 0;
189         count = 0;
190
191         while (1) {
192                 byte = __raw_readb(addr);
193                 addr++;
194                 result |= (byte & 0x7f) << shift;
195                 shift += 7;
196                 count++;
197
198                 if (!(byte & 0x80))
199                         break;
200         }
201
202         /* The number of bits in a signed integer. */
203         num_bits = 8 * sizeof(result);
204
205         if ((shift < num_bits) && (byte & 0x40))
206                 result |= (-1 << shift);
207
208         *ret = result;
209
210         return count;
211 }
212
213 /**
214  *      dwarf_read_encoded_value - return the decoded value at @addr
215  *      @addr: the address of the encoded value
216  *      @val: where to write the decoded value
217  *      @encoding: the encoding with which we can decode @addr
218  *
219  *      GCC emits encoded address in the .eh_frame FDE entries. Decode
220  *      the value at @addr using @encoding. The decoded value is written
221  *      to @val and the number of bytes read is returned.
222  */
223 static int dwarf_read_encoded_value(char *addr, unsigned long *val,
224                                     char encoding)
225 {
226         unsigned long decoded_addr = 0;
227         int count = 0;
228
229         switch (encoding & 0x70) {
230         case DW_EH_PE_absptr:
231                 break;
232         case DW_EH_PE_pcrel:
233                 decoded_addr = (unsigned long)addr;
234                 break;
235         default:
236                 pr_debug("encoding=0x%x\n", (encoding & 0x70));
237                 UNWINDER_BUG();
238         }
239
240         if ((encoding & 0x07) == 0x00)
241                 encoding |= DW_EH_PE_udata4;
242
243         switch (encoding & 0x0f) {
244         case DW_EH_PE_sdata4:
245         case DW_EH_PE_udata4:
246                 count += 4;
247                 decoded_addr += get_unaligned((u32 *)addr);
248                 __raw_writel(decoded_addr, val);
249                 break;
250         default:
251                 pr_debug("encoding=0x%x\n", encoding);
252                 UNWINDER_BUG();
253         }
254
255         return count;
256 }
257
258 /**
259  *      dwarf_entry_len - return the length of an FDE or CIE
260  *      @addr: the address of the entry
261  *      @len: the length of the entry
262  *
263  *      Read the initial_length field of the entry and store the size of
264  *      the entry in @len. We return the number of bytes read. Return a
265  *      count of 0 on error.
266  */
267 static inline int dwarf_entry_len(char *addr, unsigned long *len)
268 {
269         u32 initial_len;
270         int count;
271
272         initial_len = get_unaligned((u32 *)addr);
273         count = 4;
274
275         /*
276          * An initial length field value in the range DW_LEN_EXT_LO -
277          * DW_LEN_EXT_HI indicates an extension, and should not be
278          * interpreted as a length. The only extension that we currently
279          * understand is the use of DWARF64 addresses.
280          */
281         if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
282                 /*
283                  * The 64-bit length field immediately follows the
284                  * compulsory 32-bit length field.
285                  */
286                 if (initial_len == DW_EXT_DWARF64) {
287                         *len = get_unaligned((u64 *)addr + 4);
288                         count = 12;
289                 } else {
290                         printk(KERN_WARNING "Unknown DWARF extension\n");
291                         count = 0;
292                 }
293         } else
294                 *len = initial_len;
295
296         return count;
297 }
298
299 /**
300  *      dwarf_lookup_cie - locate the cie
301  *      @cie_ptr: pointer to help with lookup
302  */
303 static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
304 {
305         struct rb_node **rb_node = &cie_root.rb_node;
306         struct dwarf_cie *cie = NULL;
307         unsigned long flags;
308
309         spin_lock_irqsave(&dwarf_cie_lock, flags);
310
311         /*
312          * We've cached the last CIE we looked up because chances are
313          * that the FDE wants this CIE.
314          */
315         if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
316                 cie = cached_cie;
317                 goto out;
318         }
319
320         while (*rb_node) {
321                 struct dwarf_cie *cie_tmp;
322
323                 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
324                 BUG_ON(!cie_tmp);
325
326                 if (cie_ptr == cie_tmp->cie_pointer) {
327                         cie = cie_tmp;
328                         cached_cie = cie_tmp;
329                         goto out;
330                 } else {
331                         if (cie_ptr < cie_tmp->cie_pointer)
332                                 rb_node = &(*rb_node)->rb_left;
333                         else
334                                 rb_node = &(*rb_node)->rb_right;
335                 }
336         }
337
338 out:
339         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
340         return cie;
341 }
342
343 /**
344  *      dwarf_lookup_fde - locate the FDE that covers pc
345  *      @pc: the program counter
346  */
347 struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
348 {
349         struct rb_node **rb_node = &fde_root.rb_node;
350         struct dwarf_fde *fde = NULL;
351         unsigned long flags;
352
353         spin_lock_irqsave(&dwarf_fde_lock, flags);
354
355         while (*rb_node) {
356                 struct dwarf_fde *fde_tmp;
357                 unsigned long tmp_start, tmp_end;
358
359                 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
360                 BUG_ON(!fde_tmp);
361
362                 tmp_start = fde_tmp->initial_location;
363                 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
364
365                 if (pc < tmp_start) {
366                         rb_node = &(*rb_node)->rb_left;
367                 } else {
368                         if (pc < tmp_end) {
369                                 fde = fde_tmp;
370                                 goto out;
371                         } else
372                                 rb_node = &(*rb_node)->rb_right;
373                 }
374         }
375
376 out:
377         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
378
379         return fde;
380 }
381
382 /**
383  *      dwarf_cfa_execute_insns - execute instructions to calculate a CFA
384  *      @insn_start: address of the first instruction
385  *      @insn_end: address of the last instruction
386  *      @cie: the CIE for this function
387  *      @fde: the FDE for this function
388  *      @frame: the instructions calculate the CFA for this frame
389  *      @pc: the program counter of the address we're interested in
390  *
391  *      Execute the Call Frame instruction sequence starting at
392  *      @insn_start and ending at @insn_end. The instructions describe
393  *      how to calculate the Canonical Frame Address of a stackframe.
394  *      Store the results in @frame.
395  */
396 static int dwarf_cfa_execute_insns(unsigned char *insn_start,
397                                    unsigned char *insn_end,
398                                    struct dwarf_cie *cie,
399                                    struct dwarf_fde *fde,
400                                    struct dwarf_frame *frame,
401                                    unsigned long pc)
402 {
403         unsigned char insn;
404         unsigned char *current_insn;
405         unsigned int count, delta, reg, expr_len, offset;
406         struct dwarf_reg *regp;
407
408         current_insn = insn_start;
409
410         while (current_insn < insn_end && frame->pc <= pc) {
411                 insn = __raw_readb(current_insn++);
412
413                 /*
414                  * Firstly, handle the opcodes that embed their operands
415                  * in the instructions.
416                  */
417                 switch (DW_CFA_opcode(insn)) {
418                 case DW_CFA_advance_loc:
419                         delta = DW_CFA_operand(insn);
420                         delta *= cie->code_alignment_factor;
421                         frame->pc += delta;
422                         continue;
423                         /* NOTREACHED */
424                 case DW_CFA_offset:
425                         reg = DW_CFA_operand(insn);
426                         count = dwarf_read_uleb128(current_insn, &offset);
427                         current_insn += count;
428                         offset *= cie->data_alignment_factor;
429                         regp = dwarf_frame_alloc_reg(frame, reg);
430                         regp->addr = offset;
431                         regp->flags |= DWARF_REG_OFFSET;
432                         continue;
433                         /* NOTREACHED */
434                 case DW_CFA_restore:
435                         reg = DW_CFA_operand(insn);
436                         continue;
437                         /* NOTREACHED */
438                 }
439
440                 /*
441                  * Secondly, handle the opcodes that don't embed their
442                  * operands in the instruction.
443                  */
444                 switch (insn) {
445                 case DW_CFA_nop:
446                         continue;
447                 case DW_CFA_advance_loc1:
448                         delta = *current_insn++;
449                         frame->pc += delta * cie->code_alignment_factor;
450                         break;
451                 case DW_CFA_advance_loc2:
452                         delta = get_unaligned((u16 *)current_insn);
453                         current_insn += 2;
454                         frame->pc += delta * cie->code_alignment_factor;
455                         break;
456                 case DW_CFA_advance_loc4:
457                         delta = get_unaligned((u32 *)current_insn);
458                         current_insn += 4;
459                         frame->pc += delta * cie->code_alignment_factor;
460                         break;
461                 case DW_CFA_offset_extended:
462                         count = dwarf_read_uleb128(current_insn, &reg);
463                         current_insn += count;
464                         count = dwarf_read_uleb128(current_insn, &offset);
465                         current_insn += count;
466                         offset *= cie->data_alignment_factor;
467                         break;
468                 case DW_CFA_restore_extended:
469                         count = dwarf_read_uleb128(current_insn, &reg);
470                         current_insn += count;
471                         break;
472                 case DW_CFA_undefined:
473                         count = dwarf_read_uleb128(current_insn, &reg);
474                         current_insn += count;
475                         regp = dwarf_frame_alloc_reg(frame, reg);
476                         regp->flags |= DWARF_UNDEFINED;
477                         break;
478                 case DW_CFA_def_cfa:
479                         count = dwarf_read_uleb128(current_insn,
480                                                    &frame->cfa_register);
481                         current_insn += count;
482                         count = dwarf_read_uleb128(current_insn,
483                                                    &frame->cfa_offset);
484                         current_insn += count;
485
486                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
487                         break;
488                 case DW_CFA_def_cfa_register:
489                         count = dwarf_read_uleb128(current_insn,
490                                                    &frame->cfa_register);
491                         current_insn += count;
492                         frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
493                         break;
494                 case DW_CFA_def_cfa_offset:
495                         count = dwarf_read_uleb128(current_insn, &offset);
496                         current_insn += count;
497                         frame->cfa_offset = offset;
498                         break;
499                 case DW_CFA_def_cfa_expression:
500                         count = dwarf_read_uleb128(current_insn, &expr_len);
501                         current_insn += count;
502
503                         frame->cfa_expr = current_insn;
504                         frame->cfa_expr_len = expr_len;
505                         current_insn += expr_len;
506
507                         frame->flags |= DWARF_FRAME_CFA_REG_EXP;
508                         break;
509                 case DW_CFA_offset_extended_sf:
510                         count = dwarf_read_uleb128(current_insn, &reg);
511                         current_insn += count;
512                         count = dwarf_read_leb128(current_insn, &offset);
513                         current_insn += count;
514                         offset *= cie->data_alignment_factor;
515                         regp = dwarf_frame_alloc_reg(frame, reg);
516                         regp->flags |= DWARF_REG_OFFSET;
517                         regp->addr = offset;
518                         break;
519                 case DW_CFA_val_offset:
520                         count = dwarf_read_uleb128(current_insn, &reg);
521                         current_insn += count;
522                         count = dwarf_read_leb128(current_insn, &offset);
523                         offset *= cie->data_alignment_factor;
524                         regp = dwarf_frame_alloc_reg(frame, reg);
525                         regp->flags |= DWARF_VAL_OFFSET;
526                         regp->addr = offset;
527                         break;
528                 case DW_CFA_GNU_args_size:
529                         count = dwarf_read_uleb128(current_insn, &offset);
530                         current_insn += count;
531                         break;
532                 case DW_CFA_GNU_negative_offset_extended:
533                         count = dwarf_read_uleb128(current_insn, &reg);
534                         current_insn += count;
535                         count = dwarf_read_uleb128(current_insn, &offset);
536                         offset *= cie->data_alignment_factor;
537
538                         regp = dwarf_frame_alloc_reg(frame, reg);
539                         regp->flags |= DWARF_REG_OFFSET;
540                         regp->addr = -offset;
541                         break;
542                 default:
543                         pr_debug("unhandled DWARF instruction 0x%x\n", insn);
544                         UNWINDER_BUG();
545                         break;
546                 }
547         }
548
549         return 0;
550 }
551
552 /**
553  *      dwarf_free_frame - free the memory allocated for @frame
554  *      @frame: the frame to free
555  */
556 void dwarf_free_frame(struct dwarf_frame *frame)
557 {
558         dwarf_frame_free_regs(frame);
559         mempool_free(frame, dwarf_frame_pool);
560 }
561
562 extern void ret_from_irq(void);
563
564 /**
565  *      dwarf_unwind_stack - unwind the stack
566  *
567  *      @pc: address of the function to unwind
568  *      @prev: struct dwarf_frame of the previous stackframe on the callstack
569  *
570  *      Return a struct dwarf_frame representing the most recent frame
571  *      on the callstack. Each of the lower (older) stack frames are
572  *      linked via the "prev" member.
573  */
574 struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
575                                        struct dwarf_frame *prev)
576 {
577         struct dwarf_frame *frame;
578         struct dwarf_cie *cie;
579         struct dwarf_fde *fde;
580         struct dwarf_reg *reg;
581         unsigned long addr;
582
583         /*
584          * If we're starting at the top of the stack we need get the
585          * contents of a physical register to get the CFA in order to
586          * begin the virtual unwinding of the stack.
587          *
588          * NOTE: the return address is guaranteed to be setup by the
589          * time this function makes its first function call.
590          */
591         if (!pc || !prev)
592                 pc = (unsigned long)current_text_addr();
593
594 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
595         /*
596          * If our stack has been patched by the function graph tracer
597          * then we might see the address of return_to_handler() where we
598          * expected to find the real return address.
599          */
600         if (pc == (unsigned long)&return_to_handler) {
601                 int index = current->curr_ret_stack;
602
603                 /*
604                  * We currently have no way of tracking how many
605                  * return_to_handler()'s we've seen. If there is more
606                  * than one patched return address on our stack,
607                  * complain loudly.
608                  */
609                 WARN_ON(index > 0);
610
611                 pc = current->ret_stack[index].ret;
612         }
613 #endif
614
615         frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
616         if (!frame) {
617                 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
618                 UNWINDER_BUG();
619         }
620
621         INIT_LIST_HEAD(&frame->reg_list);
622         frame->flags = 0;
623         frame->prev = prev;
624         frame->return_addr = 0;
625
626         fde = dwarf_lookup_fde(pc);
627         if (!fde) {
628                 /*
629                  * This is our normal exit path. There are two reasons
630                  * why we might exit here,
631                  *
632                  *      a) pc has no asscociated DWARF frame info and so
633                  *      we don't know how to unwind this frame. This is
634                  *      usually the case when we're trying to unwind a
635                  *      frame that was called from some assembly code
636                  *      that has no DWARF info, e.g. syscalls.
637                  *
638                  *      b) the DEBUG info for pc is bogus. There's
639                  *      really no way to distinguish this case from the
640                  *      case above, which sucks because we could print a
641                  *      warning here.
642                  */
643                 goto bail;
644         }
645
646         cie = dwarf_lookup_cie(fde->cie_pointer);
647
648         frame->pc = fde->initial_location;
649
650         /* CIE initial instructions */
651         dwarf_cfa_execute_insns(cie->initial_instructions,
652                                 cie->instructions_end, cie, fde,
653                                 frame, pc);
654
655         /* FDE instructions */
656         dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
657                                 fde, frame, pc);
658
659         /* Calculate the CFA */
660         switch (frame->flags) {
661         case DWARF_FRAME_CFA_REG_OFFSET:
662                 if (prev) {
663                         reg = dwarf_frame_reg(prev, frame->cfa_register);
664                         UNWINDER_BUG_ON(!reg);
665                         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
666
667                         addr = prev->cfa + reg->addr;
668                         frame->cfa = __raw_readl(addr);
669
670                 } else {
671                         /*
672                          * Again, we're starting from the top of the
673                          * stack. We need to physically read
674                          * the contents of a register in order to get
675                          * the Canonical Frame Address for this
676                          * function.
677                          */
678                         frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
679                 }
680
681                 frame->cfa += frame->cfa_offset;
682                 break;
683         default:
684                 UNWINDER_BUG();
685         }
686
687         reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
688
689         /*
690          * If we haven't seen the return address register or the return
691          * address column is undefined then we must assume that this is
692          * the end of the callstack.
693          */
694         if (!reg || reg->flags == DWARF_UNDEFINED)
695                 goto bail;
696
697         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
698
699         addr = frame->cfa + reg->addr;
700         frame->return_addr = __raw_readl(addr);
701
702         /*
703          * Ah, the joys of unwinding through interrupts.
704          *
705          * Interrupts are tricky - the DWARF info needs to be _really_
706          * accurate and unfortunately I'm seeing a lot of bogus DWARF
707          * info. For example, I've seen interrupts occur in epilogues
708          * just after the frame pointer (r14) had been restored. The
709          * problem was that the DWARF info claimed that the CFA could be
710          * reached by using the value of the frame pointer before it was
711          * restored.
712          *
713          * So until the compiler can be trusted to produce reliable
714          * DWARF info when it really matters, let's stop unwinding once
715          * we've calculated the function that was interrupted.
716          */
717         if (prev && prev->pc == (unsigned long)ret_from_irq)
718                 frame->return_addr = 0;
719
720         return frame;
721
722 bail:
723         dwarf_free_frame(frame);
724         return NULL;
725 }
726
727 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
728                            unsigned char *end, struct module *mod)
729 {
730         struct rb_node **rb_node = &cie_root.rb_node;
731         struct rb_node *parent = *rb_node;
732         struct dwarf_cie *cie;
733         unsigned long flags;
734         int count;
735
736         cie = kzalloc(sizeof(*cie), GFP_KERNEL);
737         if (!cie)
738                 return -ENOMEM;
739
740         cie->length = len;
741
742         /*
743          * Record the offset into the .eh_frame section
744          * for this CIE. It allows this CIE to be
745          * quickly and easily looked up from the
746          * corresponding FDE.
747          */
748         cie->cie_pointer = (unsigned long)entry;
749
750         cie->version = *(char *)p++;
751         UNWINDER_BUG_ON(cie->version != 1);
752
753         cie->augmentation = p;
754         p += strlen(cie->augmentation) + 1;
755
756         count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
757         p += count;
758
759         count = dwarf_read_leb128(p, &cie->data_alignment_factor);
760         p += count;
761
762         /*
763          * Which column in the rule table contains the
764          * return address?
765          */
766         if (cie->version == 1) {
767                 cie->return_address_reg = __raw_readb(p);
768                 p++;
769         } else {
770                 count = dwarf_read_uleb128(p, &cie->return_address_reg);
771                 p += count;
772         }
773
774         if (cie->augmentation[0] == 'z') {
775                 unsigned int length, count;
776                 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
777
778                 count = dwarf_read_uleb128(p, &length);
779                 p += count;
780
781                 UNWINDER_BUG_ON((unsigned char *)p > end);
782
783                 cie->initial_instructions = p + length;
784                 cie->augmentation++;
785         }
786
787         while (*cie->augmentation) {
788                 /*
789                  * "L" indicates a byte showing how the
790                  * LSDA pointer is encoded. Skip it.
791                  */
792                 if (*cie->augmentation == 'L') {
793                         p++;
794                         cie->augmentation++;
795                 } else if (*cie->augmentation == 'R') {
796                         /*
797                          * "R" indicates a byte showing
798                          * how FDE addresses are
799                          * encoded.
800                          */
801                         cie->encoding = *(char *)p++;
802                         cie->augmentation++;
803                 } else if (*cie->augmentation == 'P') {
804                         /*
805                          * "R" indicates a personality
806                          * routine in the CIE
807                          * augmentation.
808                          */
809                         UNWINDER_BUG();
810                 } else if (*cie->augmentation == 'S') {
811                         UNWINDER_BUG();
812                 } else {
813                         /*
814                          * Unknown augmentation. Assume
815                          * 'z' augmentation.
816                          */
817                         p = cie->initial_instructions;
818                         UNWINDER_BUG_ON(!p);
819                         break;
820                 }
821         }
822
823         cie->initial_instructions = p;
824         cie->instructions_end = end;
825
826         /* Add to list */
827         spin_lock_irqsave(&dwarf_cie_lock, flags);
828
829         while (*rb_node) {
830                 struct dwarf_cie *cie_tmp;
831
832                 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
833
834                 parent = *rb_node;
835
836                 if (cie->cie_pointer < cie_tmp->cie_pointer)
837                         rb_node = &parent->rb_left;
838                 else if (cie->cie_pointer >= cie_tmp->cie_pointer)
839                         rb_node = &parent->rb_right;
840                 else
841                         WARN_ON(1);
842         }
843
844         rb_link_node(&cie->node, parent, rb_node);
845         rb_insert_color(&cie->node, &cie_root);
846
847         if (mod != NULL)
848                 list_add_tail(&cie->link, &mod->arch.cie_list);
849
850         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
851
852         return 0;
853 }
854
855 static int dwarf_parse_fde(void *entry, u32 entry_type,
856                            void *start, unsigned long len,
857                            unsigned char *end, struct module *mod)
858 {
859         struct rb_node **rb_node = &fde_root.rb_node;
860         struct rb_node *parent = *rb_node;
861         struct dwarf_fde *fde;
862         struct dwarf_cie *cie;
863         unsigned long flags;
864         int count;
865         void *p = start;
866
867         fde = kzalloc(sizeof(*fde), GFP_KERNEL);
868         if (!fde)
869                 return -ENOMEM;
870
871         fde->length = len;
872
873         /*
874          * In a .eh_frame section the CIE pointer is the
875          * delta between the address within the FDE
876          */
877         fde->cie_pointer = (unsigned long)(p - entry_type - 4);
878
879         cie = dwarf_lookup_cie(fde->cie_pointer);
880         fde->cie = cie;
881
882         if (cie->encoding)
883                 count = dwarf_read_encoded_value(p, &fde->initial_location,
884                                                  cie->encoding);
885         else
886                 count = dwarf_read_addr(p, &fde->initial_location);
887
888         p += count;
889
890         if (cie->encoding)
891                 count = dwarf_read_encoded_value(p, &fde->address_range,
892                                                  cie->encoding & 0x0f);
893         else
894                 count = dwarf_read_addr(p, &fde->address_range);
895
896         p += count;
897
898         if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
899                 unsigned int length;
900                 count = dwarf_read_uleb128(p, &length);
901                 p += count + length;
902         }
903
904         /* Call frame instructions. */
905         fde->instructions = p;
906         fde->end = end;
907
908         /* Add to list. */
909         spin_lock_irqsave(&dwarf_fde_lock, flags);
910
911         while (*rb_node) {
912                 struct dwarf_fde *fde_tmp;
913                 unsigned long tmp_start, tmp_end;
914                 unsigned long start, end;
915
916                 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
917
918                 start = fde->initial_location;
919                 end = fde->initial_location + fde->address_range;
920
921                 tmp_start = fde_tmp->initial_location;
922                 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
923
924                 parent = *rb_node;
925
926                 if (start < tmp_start)
927                         rb_node = &parent->rb_left;
928                 else if (start >= tmp_end)
929                         rb_node = &parent->rb_right;
930                 else
931                         WARN_ON(1);
932         }
933
934         rb_link_node(&fde->node, parent, rb_node);
935         rb_insert_color(&fde->node, &fde_root);
936
937         if (mod != NULL)
938                 list_add_tail(&fde->link, &mod->arch.fde_list);
939
940         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
941
942         return 0;
943 }
944
945 static void dwarf_unwinder_dump(struct task_struct *task,
946                                 struct pt_regs *regs,
947                                 unsigned long *sp,
948                                 const struct stacktrace_ops *ops,
949                                 void *data)
950 {
951         struct dwarf_frame *frame, *_frame;
952         unsigned long return_addr;
953
954         _frame = NULL;
955         return_addr = 0;
956
957         while (1) {
958                 frame = dwarf_unwind_stack(return_addr, _frame);
959
960                 if (_frame)
961                         dwarf_free_frame(_frame);
962
963                 _frame = frame;
964
965                 if (!frame || !frame->return_addr)
966                         break;
967
968                 return_addr = frame->return_addr;
969                 ops->address(data, return_addr, 1);
970         }
971
972         if (frame)
973                 dwarf_free_frame(frame);
974 }
975
976 static struct unwinder dwarf_unwinder = {
977         .name = "dwarf-unwinder",
978         .dump = dwarf_unwinder_dump,
979         .rating = 150,
980 };
981
982 static void dwarf_unwinder_cleanup(void)
983 {
984         struct rb_node **fde_rb_node = &fde_root.rb_node;
985         struct rb_node **cie_rb_node = &cie_root.rb_node;
986
987         /*
988          * Deallocate all the memory allocated for the DWARF unwinder.
989          * Traverse all the FDE/CIE lists and remove and free all the
990          * memory associated with those data structures.
991          */
992         while (*fde_rb_node) {
993                 struct dwarf_fde *fde;
994
995                 fde = rb_entry(*fde_rb_node, struct dwarf_fde, node);
996                 rb_erase(*fde_rb_node, &fde_root);
997                 kfree(fde);
998         }
999
1000         while (*cie_rb_node) {
1001                 struct dwarf_cie *cie;
1002
1003                 cie = rb_entry(*cie_rb_node, struct dwarf_cie, node);
1004                 rb_erase(*cie_rb_node, &cie_root);
1005                 kfree(cie);
1006         }
1007
1008         kmem_cache_destroy(dwarf_reg_cachep);
1009         kmem_cache_destroy(dwarf_frame_cachep);
1010 }
1011
1012 /**
1013  *      dwarf_parse_section - parse DWARF section
1014  *      @eh_frame_start: start address of the .eh_frame section
1015  *      @eh_frame_end: end address of the .eh_frame section
1016  *      @mod: the kernel module containing the .eh_frame section
1017  *
1018  *      Parse the information in a .eh_frame section.
1019  */
1020 static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1021                                struct module *mod)
1022 {
1023         u32 entry_type;
1024         void *p, *entry;
1025         int count, err = 0;
1026         unsigned long len = 0;
1027         unsigned int c_entries, f_entries;
1028         unsigned char *end;
1029
1030         c_entries = 0;
1031         f_entries = 0;
1032         entry = eh_frame_start;
1033
1034         while ((char *)entry < eh_frame_end) {
1035                 p = entry;
1036
1037                 count = dwarf_entry_len(p, &len);
1038                 if (count == 0) {
1039                         /*
1040                          * We read a bogus length field value. There is
1041                          * nothing we can do here apart from disabling
1042                          * the DWARF unwinder. We can't even skip this
1043                          * entry and move to the next one because 'len'
1044                          * tells us where our next entry is.
1045                          */
1046                         err = -EINVAL;
1047                         goto out;
1048                 } else
1049                         p += count;
1050
1051                 /* initial length does not include itself */
1052                 end = p + len;
1053
1054                 entry_type = get_unaligned((u32 *)p);
1055                 p += 4;
1056
1057                 if (entry_type == DW_EH_FRAME_CIE) {
1058                         err = dwarf_parse_cie(entry, p, len, end, mod);
1059                         if (err < 0)
1060                                 goto out;
1061                         else
1062                                 c_entries++;
1063                 } else {
1064                         err = dwarf_parse_fde(entry, entry_type, p, len,
1065                                               end, mod);
1066                         if (err < 0)
1067                                 goto out;
1068                         else
1069                                 f_entries++;
1070                 }
1071
1072                 entry = (char *)entry + len + 4;
1073         }
1074
1075         printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1076                c_entries, f_entries);
1077
1078         return 0;
1079
1080 out:
1081         return err;
1082 }
1083
1084 #ifdef CONFIG_MODULES
1085 int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1086                           struct module *me)
1087 {
1088         unsigned int i, err;
1089         unsigned long start, end;
1090         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
1091
1092         start = end = 0;
1093
1094         for (i = 1; i < hdr->e_shnum; i++) {
1095                 /* Alloc bit cleared means "ignore it." */
1096                 if ((sechdrs[i].sh_flags & SHF_ALLOC)
1097                     && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
1098                         start = sechdrs[i].sh_addr;
1099                         end = start + sechdrs[i].sh_size;
1100                         break;
1101                 }
1102         }
1103
1104         /* Did we find the .eh_frame section? */
1105         if (i != hdr->e_shnum) {
1106                 INIT_LIST_HEAD(&me->arch.cie_list);
1107                 INIT_LIST_HEAD(&me->arch.fde_list);
1108                 err = dwarf_parse_section((char *)start, (char *)end, me);
1109                 if (err) {
1110                         printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1111                                me->name);
1112                         return err;
1113                 }
1114         }
1115
1116         return 0;
1117 }
1118
1119 /**
1120  *      module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1121  *      @mod: the module that is being unloaded
1122  *
1123  *      Remove any FDEs and CIEs from the global lists that came from
1124  *      @mod's .eh_frame section because @mod is being unloaded.
1125  */
1126 void module_dwarf_cleanup(struct module *mod)
1127 {
1128         struct dwarf_fde *fde, *ftmp;
1129         struct dwarf_cie *cie, *ctmp;
1130         unsigned long flags;
1131
1132         spin_lock_irqsave(&dwarf_cie_lock, flags);
1133
1134         list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
1135                 list_del(&cie->link);
1136                 rb_erase(&cie->node, &cie_root);
1137                 kfree(cie);
1138         }
1139
1140         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1141
1142         spin_lock_irqsave(&dwarf_fde_lock, flags);
1143
1144         list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
1145                 list_del(&fde->link);
1146                 rb_erase(&fde->node, &fde_root);
1147                 kfree(fde);
1148         }
1149
1150         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1151 }
1152 #endif /* CONFIG_MODULES */
1153
1154 /**
1155  *      dwarf_unwinder_init - initialise the dwarf unwinder
1156  *
1157  *      Build the data structures describing the .dwarf_frame section to
1158  *      make it easier to lookup CIE and FDE entries. Because the
1159  *      .eh_frame section is packed as tightly as possible it is not
1160  *      easy to lookup the FDE for a given PC, so we build a list of FDE
1161  *      and CIE entries that make it easier.
1162  */
1163 static int __init dwarf_unwinder_init(void)
1164 {
1165         int err;
1166
1167         dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1168                         sizeof(struct dwarf_frame), 0,
1169                         SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1170
1171         dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1172                         sizeof(struct dwarf_reg), 0,
1173                         SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL);
1174
1175         dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ,
1176                                           mempool_alloc_slab,
1177                                           mempool_free_slab,
1178                                           dwarf_frame_cachep);
1179
1180         dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ,
1181                                          mempool_alloc_slab,
1182                                          mempool_free_slab,
1183                                          dwarf_reg_cachep);
1184
1185         err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1186         if (err)
1187                 goto out;
1188
1189         err = unwinder_register(&dwarf_unwinder);
1190         if (err)
1191                 goto out;
1192
1193         return 0;
1194
1195 out:
1196         printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1197         dwarf_unwinder_cleanup();
1198         return -EINVAL;
1199 }
1200 early_initcall(dwarf_unwinder_init);