~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/arch/sh/kernel/dwarf.c

Version: ~ [ linux-5.12-rc7 ] ~ [ linux-5.11.13 ] ~ [ linux-5.10.29 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.111 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.186 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.230 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.266 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.266 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2009 Matt Fleming <matt@console-pimps.org>
  4  *
  5  * This is an implementation of a DWARF unwinder. Its main purpose is
  6  * for generating stacktrace information. Based on the DWARF 3
  7  * specification from http://www.dwarfstd.org.
  8  *
  9  * TODO:
 10  *      - DWARF64 doesn't work.
 11  *      - Registers with DWARF_VAL_OFFSET rules aren't handled properly.
 12  */
 13 
 14 /* #define DEBUG */
 15 #include <linux/kernel.h>
 16 #include <linux/io.h>
 17 #include <linux/list.h>
 18 #include <linux/mempool.h>
 19 #include <linux/mm.h>
 20 #include <linux/elf.h>
 21 #include <linux/ftrace.h>
 22 #include <linux/module.h>
 23 #include <linux/slab.h>
 24 #include <asm/dwarf.h>
 25 #include <asm/unwinder.h>
 26 #include <asm/sections.h>
 27 #include <asm/unaligned.h>
 28 #include <asm/stacktrace.h>
 29 
 30 /* 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 struct rb_root cie_root;
 42 static DEFINE_SPINLOCK(dwarf_cie_lock);
 43 
 44 static struct rb_root fde_root;
 45 static DEFINE_SPINLOCK(dwarf_fde_lock);
 46 
 47 static struct dwarf_cie *cached_cie;
 48 
 49 static unsigned int dwarf_unwinder_ready;
 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've been called in to before initialization has
585          * completed, bail out immediately.
586          */
587         if (!dwarf_unwinder_ready)
588                 return NULL;
589 
590         /*
591          * If we're starting at the top of the stack we need get the
592          * contents of a physical register to get the CFA in order to
593          * begin the virtual unwinding of the stack.
594          *
595          * NOTE: the return address is guaranteed to be setup by the
596          * time this function makes its first function call.
597          */
598         if (!pc || !prev)
599                 pc = _THIS_IP_;
600 
601 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
602         /*
603          * If our stack has been patched by the function graph tracer
604          * then we might see the address of return_to_handler() where we
605          * expected to find the real return address.
606          */
607         if (pc == (unsigned long)&return_to_handler) {
608                 struct ftrace_ret_stack *ret_stack;
609 
610                 ret_stack = ftrace_graph_get_ret_stack(current, 0);
611                 if (ret_stack)
612                         pc = ret_stack->ret;
613                 /*
614                  * We currently have no way of tracking how many
615                  * return_to_handler()'s we've seen. If there is more
616                  * than one patched return address on our stack,
617                  * complain loudly.
618                  */
619                 WARN_ON(ftrace_graph_get_ret_stack(current, 1));
620         }
621 #endif
622 
623         frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
624         if (!frame) {
625                 printk(KERN_ERR "Unable to allocate a dwarf frame\n");
626                 UNWINDER_BUG();
627         }
628 
629         INIT_LIST_HEAD(&frame->reg_list);
630         frame->flags = 0;
631         frame->prev = prev;
632         frame->return_addr = 0;
633 
634         fde = dwarf_lookup_fde(pc);
635         if (!fde) {
636                 /*
637                  * This is our normal exit path. There are two reasons
638                  * why we might exit here,
639                  *
640                  *      a) pc has no asscociated DWARF frame info and so
641                  *      we don't know how to unwind this frame. This is
642                  *      usually the case when we're trying to unwind a
643                  *      frame that was called from some assembly code
644                  *      that has no DWARF info, e.g. syscalls.
645                  *
646                  *      b) the DEBUG info for pc is bogus. There's
647                  *      really no way to distinguish this case from the
648                  *      case above, which sucks because we could print a
649                  *      warning here.
650                  */
651                 goto bail;
652         }
653 
654         cie = dwarf_lookup_cie(fde->cie_pointer);
655 
656         frame->pc = fde->initial_location;
657 
658         /* CIE initial instructions */
659         dwarf_cfa_execute_insns(cie->initial_instructions,
660                                 cie->instructions_end, cie, fde,
661                                 frame, pc);
662 
663         /* FDE instructions */
664         dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
665                                 fde, frame, pc);
666 
667         /* Calculate the CFA */
668         switch (frame->flags) {
669         case DWARF_FRAME_CFA_REG_OFFSET:
670                 if (prev) {
671                         reg = dwarf_frame_reg(prev, frame->cfa_register);
672                         UNWINDER_BUG_ON(!reg);
673                         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
674 
675                         addr = prev->cfa + reg->addr;
676                         frame->cfa = __raw_readl(addr);
677 
678                 } else {
679                         /*
680                          * Again, we're starting from the top of the
681                          * stack. We need to physically read
682                          * the contents of a register in order to get
683                          * the Canonical Frame Address for this
684                          * function.
685                          */
686                         frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
687                 }
688 
689                 frame->cfa += frame->cfa_offset;
690                 break;
691         default:
692                 UNWINDER_BUG();
693         }
694 
695         reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
696 
697         /*
698          * If we haven't seen the return address register or the return
699          * address column is undefined then we must assume that this is
700          * the end of the callstack.
701          */
702         if (!reg || reg->flags == DWARF_UNDEFINED)
703                 goto bail;
704 
705         UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
706 
707         addr = frame->cfa + reg->addr;
708         frame->return_addr = __raw_readl(addr);
709 
710         /*
711          * Ah, the joys of unwinding through interrupts.
712          *
713          * Interrupts are tricky - the DWARF info needs to be _really_
714          * accurate and unfortunately I'm seeing a lot of bogus DWARF
715          * info. For example, I've seen interrupts occur in epilogues
716          * just after the frame pointer (r14) had been restored. The
717          * problem was that the DWARF info claimed that the CFA could be
718          * reached by using the value of the frame pointer before it was
719          * restored.
720          *
721          * So until the compiler can be trusted to produce reliable
722          * DWARF info when it really matters, let's stop unwinding once
723          * we've calculated the function that was interrupted.
724          */
725         if (prev && prev->pc == (unsigned long)ret_from_irq)
726                 frame->return_addr = 0;
727 
728         return frame;
729 
730 bail:
731         dwarf_free_frame(frame);
732         return NULL;
733 }
734 
735 static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
736                            unsigned char *end, struct module *mod)
737 {
738         struct rb_node **rb_node = &cie_root.rb_node;
739         struct rb_node *parent = *rb_node;
740         struct dwarf_cie *cie;
741         unsigned long flags;
742         int count;
743 
744         cie = kzalloc(sizeof(*cie), GFP_KERNEL);
745         if (!cie)
746                 return -ENOMEM;
747 
748         cie->length = len;
749 
750         /*
751          * Record the offset into the .eh_frame section
752          * for this CIE. It allows this CIE to be
753          * quickly and easily looked up from the
754          * corresponding FDE.
755          */
756         cie->cie_pointer = (unsigned long)entry;
757 
758         cie->version = *(char *)p++;
759         UNWINDER_BUG_ON(cie->version != 1);
760 
761         cie->augmentation = p;
762         p += strlen(cie->augmentation) + 1;
763 
764         count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
765         p += count;
766 
767         count = dwarf_read_leb128(p, &cie->data_alignment_factor);
768         p += count;
769 
770         /*
771          * Which column in the rule table contains the
772          * return address?
773          */
774         if (cie->version == 1) {
775                 cie->return_address_reg = __raw_readb(p);
776                 p++;
777         } else {
778                 count = dwarf_read_uleb128(p, &cie->return_address_reg);
779                 p += count;
780         }
781 
782         if (cie->augmentation[0] == 'z') {
783                 unsigned int length, count;
784                 cie->flags |= DWARF_CIE_Z_AUGMENTATION;
785 
786                 count = dwarf_read_uleb128(p, &length);
787                 p += count;
788 
789                 UNWINDER_BUG_ON((unsigned char *)p > end);
790 
791                 cie->initial_instructions = p + length;
792                 cie->augmentation++;
793         }
794 
795         while (*cie->augmentation) {
796                 /*
797                  * "L" indicates a byte showing how the
798                  * LSDA pointer is encoded. Skip it.
799                  */
800                 if (*cie->augmentation == 'L') {
801                         p++;
802                         cie->augmentation++;
803                 } else if (*cie->augmentation == 'R') {
804                         /*
805                          * "R" indicates a byte showing
806                          * how FDE addresses are
807                          * encoded.
808                          */
809                         cie->encoding = *(char *)p++;
810                         cie->augmentation++;
811                 } else if (*cie->augmentation == 'P') {
812                         /*
813                          * "R" indicates a personality
814                          * routine in the CIE
815                          * augmentation.
816                          */
817                         UNWINDER_BUG();
818                 } else if (*cie->augmentation == 'S') {
819                         UNWINDER_BUG();
820                 } else {
821                         /*
822                          * Unknown augmentation. Assume
823                          * 'z' augmentation.
824                          */
825                         p = cie->initial_instructions;
826                         UNWINDER_BUG_ON(!p);
827                         break;
828                 }
829         }
830 
831         cie->initial_instructions = p;
832         cie->instructions_end = end;
833 
834         /* Add to list */
835         spin_lock_irqsave(&dwarf_cie_lock, flags);
836 
837         while (*rb_node) {
838                 struct dwarf_cie *cie_tmp;
839 
840                 cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
841 
842                 parent = *rb_node;
843 
844                 if (cie->cie_pointer < cie_tmp->cie_pointer)
845                         rb_node = &parent->rb_left;
846                 else if (cie->cie_pointer >= cie_tmp->cie_pointer)
847                         rb_node = &parent->rb_right;
848                 else
849                         WARN_ON(1);
850         }
851 
852         rb_link_node(&cie->node, parent, rb_node);
853         rb_insert_color(&cie->node, &cie_root);
854 
855 #ifdef CONFIG_MODULES
856         if (mod != NULL)
857                 list_add_tail(&cie->link, &mod->arch.cie_list);
858 #endif
859 
860         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
861 
862         return 0;
863 }
864 
865 static int dwarf_parse_fde(void *entry, u32 entry_type,
866                            void *start, unsigned long len,
867                            unsigned char *end, struct module *mod)
868 {
869         struct rb_node **rb_node = &fde_root.rb_node;
870         struct rb_node *parent = *rb_node;
871         struct dwarf_fde *fde;
872         struct dwarf_cie *cie;
873         unsigned long flags;
874         int count;
875         void *p = start;
876 
877         fde = kzalloc(sizeof(*fde), GFP_KERNEL);
878         if (!fde)
879                 return -ENOMEM;
880 
881         fde->length = len;
882 
883         /*
884          * In a .eh_frame section the CIE pointer is the
885          * delta between the address within the FDE
886          */
887         fde->cie_pointer = (unsigned long)(p - entry_type - 4);
888 
889         cie = dwarf_lookup_cie(fde->cie_pointer);
890         fde->cie = cie;
891 
892         if (cie->encoding)
893                 count = dwarf_read_encoded_value(p, &fde->initial_location,
894                                                  cie->encoding);
895         else
896                 count = dwarf_read_addr(p, &fde->initial_location);
897 
898         p += count;
899 
900         if (cie->encoding)
901                 count = dwarf_read_encoded_value(p, &fde->address_range,
902                                                  cie->encoding & 0x0f);
903         else
904                 count = dwarf_read_addr(p, &fde->address_range);
905 
906         p += count;
907 
908         if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
909                 unsigned int length;
910                 count = dwarf_read_uleb128(p, &length);
911                 p += count + length;
912         }
913 
914         /* Call frame instructions. */
915         fde->instructions = p;
916         fde->end = end;
917 
918         /* Add to list. */
919         spin_lock_irqsave(&dwarf_fde_lock, flags);
920 
921         while (*rb_node) {
922                 struct dwarf_fde *fde_tmp;
923                 unsigned long tmp_start, tmp_end;
924                 unsigned long start, end;
925 
926                 fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
927 
928                 start = fde->initial_location;
929                 end = fde->initial_location + fde->address_range;
930 
931                 tmp_start = fde_tmp->initial_location;
932                 tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
933 
934                 parent = *rb_node;
935 
936                 if (start < tmp_start)
937                         rb_node = &parent->rb_left;
938                 else if (start >= tmp_end)
939                         rb_node = &parent->rb_right;
940                 else
941                         WARN_ON(1);
942         }
943 
944         rb_link_node(&fde->node, parent, rb_node);
945         rb_insert_color(&fde->node, &fde_root);
946 
947 #ifdef CONFIG_MODULES
948         if (mod != NULL)
949                 list_add_tail(&fde->link, &mod->arch.fde_list);
950 #endif
951 
952         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
953 
954         return 0;
955 }
956 
957 static void dwarf_unwinder_dump(struct task_struct *task,
958                                 struct pt_regs *regs,
959                                 unsigned long *sp,
960                                 const struct stacktrace_ops *ops,
961                                 void *data)
962 {
963         struct dwarf_frame *frame, *_frame;
964         unsigned long return_addr;
965 
966         _frame = NULL;
967         return_addr = 0;
968 
969         while (1) {
970                 frame = dwarf_unwind_stack(return_addr, _frame);
971 
972                 if (_frame)
973                         dwarf_free_frame(_frame);
974 
975                 _frame = frame;
976 
977                 if (!frame || !frame->return_addr)
978                         break;
979 
980                 return_addr = frame->return_addr;
981                 ops->address(data, return_addr, 1);
982         }
983 
984         if (frame)
985                 dwarf_free_frame(frame);
986 }
987 
988 static struct unwinder dwarf_unwinder = {
989         .name = "dwarf-unwinder",
990         .dump = dwarf_unwinder_dump,
991         .rating = 150,
992 };
993 
994 static void __init dwarf_unwinder_cleanup(void)
995 {
996         struct dwarf_fde *fde, *next_fde;
997         struct dwarf_cie *cie, *next_cie;
998 
999         /*
1000          * Deallocate all the memory allocated for the DWARF unwinder.
1001          * Traverse all the FDE/CIE lists and remove and free all the
1002          * memory associated with those data structures.
1003          */
1004         rbtree_postorder_for_each_entry_safe(fde, next_fde, &fde_root, node)
1005                 kfree(fde);
1006 
1007         rbtree_postorder_for_each_entry_safe(cie, next_cie, &cie_root, node)
1008                 kfree(cie);
1009 
1010         mempool_destroy(dwarf_reg_pool);
1011         mempool_destroy(dwarf_frame_pool);
1012         kmem_cache_destroy(dwarf_reg_cachep);
1013         kmem_cache_destroy(dwarf_frame_cachep);
1014 }
1015 
1016 /**
1017  *      dwarf_parse_section - parse DWARF section
1018  *      @eh_frame_start: start address of the .eh_frame section
1019  *      @eh_frame_end: end address of the .eh_frame section
1020  *      @mod: the kernel module containing the .eh_frame section
1021  *
1022  *      Parse the information in a .eh_frame section.
1023  */
1024 static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
1025                                struct module *mod)
1026 {
1027         u32 entry_type;
1028         void *p, *entry;
1029         int count, err = 0;
1030         unsigned long len = 0;
1031         unsigned int c_entries, f_entries;
1032         unsigned char *end;
1033 
1034         c_entries = 0;
1035         f_entries = 0;
1036         entry = eh_frame_start;
1037 
1038         while ((char *)entry < eh_frame_end) {
1039                 p = entry;
1040 
1041                 count = dwarf_entry_len(p, &len);
1042                 if (count == 0) {
1043                         /*
1044                          * We read a bogus length field value. There is
1045                          * nothing we can do here apart from disabling
1046                          * the DWARF unwinder. We can't even skip this
1047                          * entry and move to the next one because 'len'
1048                          * tells us where our next entry is.
1049                          */
1050                         err = -EINVAL;
1051                         goto out;
1052                 } else
1053                         p += count;
1054 
1055                 /* initial length does not include itself */
1056                 end = p + len;
1057 
1058                 entry_type = get_unaligned((u32 *)p);
1059                 p += 4;
1060 
1061                 if (entry_type == DW_EH_FRAME_CIE) {
1062                         err = dwarf_parse_cie(entry, p, len, end, mod);
1063                         if (err < 0)
1064                                 goto out;
1065                         else
1066                                 c_entries++;
1067                 } else {
1068                         err = dwarf_parse_fde(entry, entry_type, p, len,
1069                                               end, mod);
1070                         if (err < 0)
1071                                 goto out;
1072                         else
1073                                 f_entries++;
1074                 }
1075 
1076                 entry = (char *)entry + len + 4;
1077         }
1078 
1079         printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
1080                c_entries, f_entries);
1081 
1082         return 0;
1083 
1084 out:
1085         return err;
1086 }
1087 
1088 #ifdef CONFIG_MODULES
1089 int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
1090                           struct module *me)
1091 {
1092         unsigned int i, err;
1093         unsigned long start, end;
1094         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
1095 
1096         start = end = 0;
1097 
1098         for (i = 1; i < hdr->e_shnum; i++) {
1099                 /* Alloc bit cleared means "ignore it." */
1100                 if ((sechdrs[i].sh_flags & SHF_ALLOC)
1101                     && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
1102                         start = sechdrs[i].sh_addr;
1103                         end = start + sechdrs[i].sh_size;
1104                         break;
1105                 }
1106         }
1107 
1108         /* Did we find the .eh_frame section? */
1109         if (i != hdr->e_shnum) {
1110                 INIT_LIST_HEAD(&me->arch.cie_list);
1111                 INIT_LIST_HEAD(&me->arch.fde_list);
1112                 err = dwarf_parse_section((char *)start, (char *)end, me);
1113                 if (err) {
1114                         printk(KERN_WARNING "%s: failed to parse DWARF info\n",
1115                                me->name);
1116                         return err;
1117                 }
1118         }
1119 
1120         return 0;
1121 }
1122 
1123 /**
1124  *      module_dwarf_cleanup - remove FDE/CIEs associated with @mod
1125  *      @mod: the module that is being unloaded
1126  *
1127  *      Remove any FDEs and CIEs from the global lists that came from
1128  *      @mod's .eh_frame section because @mod is being unloaded.
1129  */
1130 void module_dwarf_cleanup(struct module *mod)
1131 {
1132         struct dwarf_fde *fde, *ftmp;
1133         struct dwarf_cie *cie, *ctmp;
1134         unsigned long flags;
1135 
1136         spin_lock_irqsave(&dwarf_cie_lock, flags);
1137 
1138         list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
1139                 list_del(&cie->link);
1140                 rb_erase(&cie->node, &cie_root);
1141                 kfree(cie);
1142         }
1143 
1144         spin_unlock_irqrestore(&dwarf_cie_lock, flags);
1145 
1146         spin_lock_irqsave(&dwarf_fde_lock, flags);
1147 
1148         list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
1149                 list_del(&fde->link);
1150                 rb_erase(&fde->node, &fde_root);
1151                 kfree(fde);
1152         }
1153 
1154         spin_unlock_irqrestore(&dwarf_fde_lock, flags);
1155 }
1156 #endif /* CONFIG_MODULES */
1157 
1158 /**
1159  *      dwarf_unwinder_init - initialise the dwarf unwinder
1160  *
1161  *      Build the data structures describing the .dwarf_frame section to
1162  *      make it easier to lookup CIE and FDE entries. Because the
1163  *      .eh_frame section is packed as tightly as possible it is not
1164  *      easy to lookup the FDE for a given PC, so we build a list of FDE
1165  *      and CIE entries that make it easier.
1166  */
1167 static int __init dwarf_unwinder_init(void)
1168 {
1169         int err = -ENOMEM;
1170 
1171         dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
1172                         sizeof(struct dwarf_frame), 0,
1173                         SLAB_PANIC | SLAB_HWCACHE_ALIGN, NULL);
1174 
1175         dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
1176                         sizeof(struct dwarf_reg), 0,
1177                         SLAB_PANIC | SLAB_HWCACHE_ALIGN, NULL);
1178 
1179         dwarf_frame_pool = mempool_create_slab_pool(DWARF_FRAME_MIN_REQ,
1180                                                     dwarf_frame_cachep);
1181         if (!dwarf_frame_pool)
1182                 goto out;
1183 
1184         dwarf_reg_pool = mempool_create_slab_pool(DWARF_REG_MIN_REQ,
1185                                                   dwarf_reg_cachep);
1186         if (!dwarf_reg_pool)
1187                 goto out;
1188 
1189         err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
1190         if (err)
1191                 goto out;
1192 
1193         err = unwinder_register(&dwarf_unwinder);
1194         if (err)
1195                 goto out;
1196 
1197         dwarf_unwinder_ready = 1;
1198 
1199         return 0;
1200 
1201 out:
1202         printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
1203         dwarf_unwinder_cleanup();
1204         return err;
1205 }
1206 early_initcall(dwarf_unwinder_init);
1207 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp