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bd353861 MF |
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. | |
97efbbd5 | 14 | * - Registers with DWARF_VAL_OFFSET rules aren't handled properly. |
bd353861 MF |
15 | */ |
16 | ||
17 | /* #define DEBUG */ | |
18 | #include <linux/kernel.h> | |
19 | #include <linux/io.h> | |
20 | #include <linux/list.h> | |
fb3f3e7f | 21 | #include <linux/mempool.h> |
bd353861 MF |
22 | #include <linux/mm.h> |
23 | #include <asm/dwarf.h> | |
24 | #include <asm/unwinder.h> | |
25 | #include <asm/sections.h> | |
3497447f | 26 | #include <asm/unaligned.h> |
bd353861 MF |
27 | #include <asm/dwarf.h> |
28 | #include <asm/stacktrace.h> | |
29 | ||
fb3f3e7f MF |
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 | ||
bd353861 | 41 | static LIST_HEAD(dwarf_cie_list); |
97f361e2 | 42 | static DEFINE_SPINLOCK(dwarf_cie_lock); |
bd353861 MF |
43 | |
44 | static LIST_HEAD(dwarf_fde_list); | |
97f361e2 | 45 | static DEFINE_SPINLOCK(dwarf_fde_lock); |
bd353861 MF |
46 | |
47 | static struct dwarf_cie *cached_cie; | |
48 | ||
fb3f3e7f MF |
49 | /** |
50 | * dwarf_frame_alloc_reg - allocate memory for a DWARF register | |
51 | * @frame: the DWARF frame whose list of registers we insert on | |
52 | * @reg_num: the register number | |
53 | * | |
54 | * Allocate space for, and initialise, a dwarf reg from | |
55 | * dwarf_reg_pool and insert it onto the (unsorted) linked-list of | |
56 | * dwarf registers for @frame. | |
bd353861 | 57 | * |
fb3f3e7f | 58 | * Return the initialised DWARF reg. |
bd353861 | 59 | */ |
fb3f3e7f MF |
60 | static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame, |
61 | unsigned int reg_num) | |
bd353861 | 62 | { |
fb3f3e7f | 63 | struct dwarf_reg *reg; |
bd353861 | 64 | |
fb3f3e7f MF |
65 | reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC); |
66 | if (!reg) { | |
67 | printk(KERN_WARNING "Unable to allocate a DWARF register\n"); | |
bd353861 MF |
68 | /* |
69 | * Let's just bomb hard here, we have no way to | |
70 | * gracefully recover. | |
71 | */ | |
72 | BUG(); | |
73 | } | |
74 | ||
fb3f3e7f MF |
75 | reg->number = reg_num; |
76 | reg->addr = 0; | |
77 | reg->flags = 0; | |
78 | ||
79 | list_add(®->link, &frame->reg_list); | |
80 | ||
81 | return reg; | |
82 | } | |
83 | ||
84 | static void dwarf_frame_free_regs(struct dwarf_frame *frame) | |
85 | { | |
86 | struct dwarf_reg *reg, *n; | |
87 | ||
88 | list_for_each_entry_safe(reg, n, &frame->reg_list, link) { | |
89 | list_del(®->link); | |
90 | mempool_free(reg, dwarf_reg_pool); | |
91 | } | |
92 | } | |
93 | ||
94 | /** | |
95 | * dwarf_frame_reg - return a DWARF register | |
96 | * @frame: the DWARF frame to search in for @reg_num | |
97 | * @reg_num: the register number to search for | |
98 | * | |
99 | * Lookup and return the dwarf reg @reg_num for this frame. Return | |
100 | * NULL if @reg_num is an register invalid number. | |
101 | */ | |
102 | static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame, | |
103 | unsigned int reg_num) | |
104 | { | |
105 | struct dwarf_reg *reg; | |
106 | ||
107 | list_for_each_entry(reg, &frame->reg_list, link) { | |
108 | if (reg->number == reg_num) | |
109 | return reg; | |
bd353861 MF |
110 | } |
111 | ||
fb3f3e7f | 112 | return NULL; |
bd353861 MF |
113 | } |
114 | ||
115 | /** | |
116 | * dwarf_read_addr - read dwarf data | |
117 | * @src: source address of data | |
118 | * @dst: destination address to store the data to | |
119 | * | |
120 | * Read 'n' bytes from @src, where 'n' is the size of an address on | |
121 | * the native machine. We return the number of bytes read, which | |
122 | * should always be 'n'. We also have to be careful when reading | |
123 | * from @src and writing to @dst, because they can be arbitrarily | |
124 | * aligned. Return 'n' - the number of bytes read. | |
125 | */ | |
3497447f | 126 | static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst) |
bd353861 | 127 | { |
bf43a160 PM |
128 | u32 val = get_unaligned(src); |
129 | put_unaligned(val, dst); | |
bd353861 MF |
130 | return sizeof(unsigned long *); |
131 | } | |
132 | ||
133 | /** | |
134 | * dwarf_read_uleb128 - read unsigned LEB128 data | |
135 | * @addr: the address where the ULEB128 data is stored | |
136 | * @ret: address to store the result | |
137 | * | |
138 | * Decode an unsigned LEB128 encoded datum. The algorithm is taken | |
139 | * from Appendix C of the DWARF 3 spec. For information on the | |
140 | * encodings refer to section "7.6 - Variable Length Data". Return | |
141 | * the number of bytes read. | |
142 | */ | |
143 | static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret) | |
144 | { | |
145 | unsigned int result; | |
146 | unsigned char byte; | |
147 | int shift, count; | |
148 | ||
149 | result = 0; | |
150 | shift = 0; | |
151 | count = 0; | |
152 | ||
153 | while (1) { | |
154 | byte = __raw_readb(addr); | |
155 | addr++; | |
156 | count++; | |
157 | ||
158 | result |= (byte & 0x7f) << shift; | |
159 | shift += 7; | |
160 | ||
161 | if (!(byte & 0x80)) | |
162 | break; | |
163 | } | |
164 | ||
165 | *ret = result; | |
166 | ||
167 | return count; | |
168 | } | |
169 | ||
170 | /** | |
171 | * dwarf_read_leb128 - read signed LEB128 data | |
172 | * @addr: the address of the LEB128 encoded data | |
173 | * @ret: address to store the result | |
174 | * | |
175 | * Decode signed LEB128 data. The algorithm is taken from Appendix | |
176 | * C of the DWARF 3 spec. Return the number of bytes read. | |
177 | */ | |
178 | static inline unsigned long dwarf_read_leb128(char *addr, int *ret) | |
179 | { | |
180 | unsigned char byte; | |
181 | int result, shift; | |
182 | int num_bits; | |
183 | int count; | |
184 | ||
185 | result = 0; | |
186 | shift = 0; | |
187 | count = 0; | |
188 | ||
189 | while (1) { | |
190 | byte = __raw_readb(addr); | |
191 | addr++; | |
192 | result |= (byte & 0x7f) << shift; | |
193 | shift += 7; | |
194 | count++; | |
195 | ||
196 | if (!(byte & 0x80)) | |
197 | break; | |
198 | } | |
199 | ||
200 | /* The number of bits in a signed integer. */ | |
201 | num_bits = 8 * sizeof(result); | |
202 | ||
203 | if ((shift < num_bits) && (byte & 0x40)) | |
204 | result |= (-1 << shift); | |
205 | ||
206 | *ret = result; | |
207 | ||
208 | return count; | |
209 | } | |
210 | ||
211 | /** | |
212 | * dwarf_read_encoded_value - return the decoded value at @addr | |
213 | * @addr: the address of the encoded value | |
214 | * @val: where to write the decoded value | |
215 | * @encoding: the encoding with which we can decode @addr | |
216 | * | |
217 | * GCC emits encoded address in the .eh_frame FDE entries. Decode | |
218 | * the value at @addr using @encoding. The decoded value is written | |
219 | * to @val and the number of bytes read is returned. | |
220 | */ | |
221 | static int dwarf_read_encoded_value(char *addr, unsigned long *val, | |
222 | char encoding) | |
223 | { | |
224 | unsigned long decoded_addr = 0; | |
225 | int count = 0; | |
226 | ||
227 | switch (encoding & 0x70) { | |
228 | case DW_EH_PE_absptr: | |
229 | break; | |
230 | case DW_EH_PE_pcrel: | |
231 | decoded_addr = (unsigned long)addr; | |
232 | break; | |
233 | default: | |
234 | pr_debug("encoding=0x%x\n", (encoding & 0x70)); | |
235 | BUG(); | |
236 | } | |
237 | ||
238 | if ((encoding & 0x07) == 0x00) | |
239 | encoding |= DW_EH_PE_udata4; | |
240 | ||
241 | switch (encoding & 0x0f) { | |
242 | case DW_EH_PE_sdata4: | |
243 | case DW_EH_PE_udata4: | |
244 | count += 4; | |
3497447f | 245 | decoded_addr += get_unaligned((u32 *)addr); |
bd353861 MF |
246 | __raw_writel(decoded_addr, val); |
247 | break; | |
248 | default: | |
249 | pr_debug("encoding=0x%x\n", encoding); | |
250 | BUG(); | |
251 | } | |
252 | ||
253 | return count; | |
254 | } | |
255 | ||
256 | /** | |
257 | * dwarf_entry_len - return the length of an FDE or CIE | |
258 | * @addr: the address of the entry | |
259 | * @len: the length of the entry | |
260 | * | |
261 | * Read the initial_length field of the entry and store the size of | |
262 | * the entry in @len. We return the number of bytes read. Return a | |
263 | * count of 0 on error. | |
264 | */ | |
265 | static inline int dwarf_entry_len(char *addr, unsigned long *len) | |
266 | { | |
267 | u32 initial_len; | |
268 | int count; | |
269 | ||
3497447f | 270 | initial_len = get_unaligned((u32 *)addr); |
bd353861 MF |
271 | count = 4; |
272 | ||
273 | /* | |
274 | * An initial length field value in the range DW_LEN_EXT_LO - | |
275 | * DW_LEN_EXT_HI indicates an extension, and should not be | |
276 | * interpreted as a length. The only extension that we currently | |
277 | * understand is the use of DWARF64 addresses. | |
278 | */ | |
279 | if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) { | |
280 | /* | |
281 | * The 64-bit length field immediately follows the | |
282 | * compulsory 32-bit length field. | |
283 | */ | |
284 | if (initial_len == DW_EXT_DWARF64) { | |
3497447f | 285 | *len = get_unaligned((u64 *)addr + 4); |
bd353861 MF |
286 | count = 12; |
287 | } else { | |
288 | printk(KERN_WARNING "Unknown DWARF extension\n"); | |
289 | count = 0; | |
290 | } | |
291 | } else | |
292 | *len = initial_len; | |
293 | ||
294 | return count; | |
295 | } | |
296 | ||
297 | /** | |
298 | * dwarf_lookup_cie - locate the cie | |
299 | * @cie_ptr: pointer to help with lookup | |
300 | */ | |
301 | static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr) | |
302 | { | |
97f361e2 | 303 | struct dwarf_cie *cie; |
bd353861 MF |
304 | unsigned long flags; |
305 | ||
306 | spin_lock_irqsave(&dwarf_cie_lock, flags); | |
307 | ||
308 | /* | |
309 | * We've cached the last CIE we looked up because chances are | |
310 | * that the FDE wants this CIE. | |
311 | */ | |
312 | if (cached_cie && cached_cie->cie_pointer == cie_ptr) { | |
313 | cie = cached_cie; | |
314 | goto out; | |
315 | } | |
316 | ||
97f361e2 | 317 | list_for_each_entry(cie, &dwarf_cie_list, link) { |
bd353861 MF |
318 | if (cie->cie_pointer == cie_ptr) { |
319 | cached_cie = cie; | |
320 | break; | |
321 | } | |
322 | } | |
323 | ||
324 | /* Couldn't find the entry in the list. */ | |
325 | if (&cie->link == &dwarf_cie_list) | |
326 | cie = NULL; | |
327 | out: | |
328 | spin_unlock_irqrestore(&dwarf_cie_lock, flags); | |
329 | return cie; | |
330 | } | |
331 | ||
332 | /** | |
333 | * dwarf_lookup_fde - locate the FDE that covers pc | |
334 | * @pc: the program counter | |
335 | */ | |
336 | struct dwarf_fde *dwarf_lookup_fde(unsigned long pc) | |
337 | { | |
97f361e2 | 338 | struct dwarf_fde *fde; |
bd353861 | 339 | unsigned long flags; |
bd353861 MF |
340 | |
341 | spin_lock_irqsave(&dwarf_fde_lock, flags); | |
97f361e2 PM |
342 | |
343 | list_for_each_entry(fde, &dwarf_fde_list, link) { | |
bd353861 MF |
344 | unsigned long start, end; |
345 | ||
346 | start = fde->initial_location; | |
347 | end = fde->initial_location + fde->address_range; | |
348 | ||
349 | if (pc >= start && pc < end) | |
350 | break; | |
351 | } | |
352 | ||
353 | /* Couldn't find the entry in the list. */ | |
354 | if (&fde->link == &dwarf_fde_list) | |
355 | fde = NULL; | |
356 | ||
357 | spin_unlock_irqrestore(&dwarf_fde_lock, flags); | |
358 | ||
359 | return fde; | |
360 | } | |
361 | ||
362 | /** | |
363 | * dwarf_cfa_execute_insns - execute instructions to calculate a CFA | |
364 | * @insn_start: address of the first instruction | |
365 | * @insn_end: address of the last instruction | |
366 | * @cie: the CIE for this function | |
367 | * @fde: the FDE for this function | |
368 | * @frame: the instructions calculate the CFA for this frame | |
369 | * @pc: the program counter of the address we're interested in | |
370 | * | |
371 | * Execute the Call Frame instruction sequence starting at | |
372 | * @insn_start and ending at @insn_end. The instructions describe | |
373 | * how to calculate the Canonical Frame Address of a stackframe. | |
374 | * Store the results in @frame. | |
375 | */ | |
376 | static int dwarf_cfa_execute_insns(unsigned char *insn_start, | |
377 | unsigned char *insn_end, | |
378 | struct dwarf_cie *cie, | |
379 | struct dwarf_fde *fde, | |
380 | struct dwarf_frame *frame, | |
b955873b | 381 | unsigned long pc) |
bd353861 MF |
382 | { |
383 | unsigned char insn; | |
384 | unsigned char *current_insn; | |
385 | unsigned int count, delta, reg, expr_len, offset; | |
fb3f3e7f | 386 | struct dwarf_reg *regp; |
bd353861 MF |
387 | |
388 | current_insn = insn_start; | |
389 | ||
b955873b | 390 | while (current_insn < insn_end && frame->pc <= pc) { |
bd353861 MF |
391 | insn = __raw_readb(current_insn++); |
392 | ||
393 | /* | |
394 | * Firstly, handle the opcodes that embed their operands | |
395 | * in the instructions. | |
396 | */ | |
397 | switch (DW_CFA_opcode(insn)) { | |
398 | case DW_CFA_advance_loc: | |
399 | delta = DW_CFA_operand(insn); | |
400 | delta *= cie->code_alignment_factor; | |
401 | frame->pc += delta; | |
402 | continue; | |
403 | /* NOTREACHED */ | |
404 | case DW_CFA_offset: | |
405 | reg = DW_CFA_operand(insn); | |
406 | count = dwarf_read_uleb128(current_insn, &offset); | |
407 | current_insn += count; | |
408 | offset *= cie->data_alignment_factor; | |
fb3f3e7f MF |
409 | regp = dwarf_frame_alloc_reg(frame, reg); |
410 | regp->addr = offset; | |
411 | regp->flags |= DWARF_REG_OFFSET; | |
bd353861 MF |
412 | continue; |
413 | /* NOTREACHED */ | |
414 | case DW_CFA_restore: | |
415 | reg = DW_CFA_operand(insn); | |
416 | continue; | |
417 | /* NOTREACHED */ | |
418 | } | |
419 | ||
420 | /* | |
421 | * Secondly, handle the opcodes that don't embed their | |
422 | * operands in the instruction. | |
423 | */ | |
424 | switch (insn) { | |
425 | case DW_CFA_nop: | |
426 | continue; | |
427 | case DW_CFA_advance_loc1: | |
428 | delta = *current_insn++; | |
429 | frame->pc += delta * cie->code_alignment_factor; | |
430 | break; | |
431 | case DW_CFA_advance_loc2: | |
3497447f | 432 | delta = get_unaligned((u16 *)current_insn); |
bd353861 MF |
433 | current_insn += 2; |
434 | frame->pc += delta * cie->code_alignment_factor; | |
435 | break; | |
436 | case DW_CFA_advance_loc4: | |
3497447f | 437 | delta = get_unaligned((u32 *)current_insn); |
bd353861 MF |
438 | current_insn += 4; |
439 | frame->pc += delta * cie->code_alignment_factor; | |
440 | break; | |
441 | case DW_CFA_offset_extended: | |
442 | count = dwarf_read_uleb128(current_insn, ®); | |
443 | current_insn += count; | |
444 | count = dwarf_read_uleb128(current_insn, &offset); | |
445 | current_insn += count; | |
446 | offset *= cie->data_alignment_factor; | |
447 | break; | |
448 | case DW_CFA_restore_extended: | |
449 | count = dwarf_read_uleb128(current_insn, ®); | |
450 | current_insn += count; | |
451 | break; | |
452 | case DW_CFA_undefined: | |
453 | count = dwarf_read_uleb128(current_insn, ®); | |
454 | current_insn += count; | |
455 | break; | |
456 | case DW_CFA_def_cfa: | |
457 | count = dwarf_read_uleb128(current_insn, | |
458 | &frame->cfa_register); | |
459 | current_insn += count; | |
460 | count = dwarf_read_uleb128(current_insn, | |
461 | &frame->cfa_offset); | |
462 | current_insn += count; | |
463 | ||
464 | frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; | |
465 | break; | |
466 | case DW_CFA_def_cfa_register: | |
467 | count = dwarf_read_uleb128(current_insn, | |
468 | &frame->cfa_register); | |
469 | current_insn += count; | |
470 | frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; | |
471 | break; | |
472 | case DW_CFA_def_cfa_offset: | |
473 | count = dwarf_read_uleb128(current_insn, &offset); | |
474 | current_insn += count; | |
475 | frame->cfa_offset = offset; | |
476 | break; | |
477 | case DW_CFA_def_cfa_expression: | |
478 | count = dwarf_read_uleb128(current_insn, &expr_len); | |
479 | current_insn += count; | |
480 | ||
481 | frame->cfa_expr = current_insn; | |
482 | frame->cfa_expr_len = expr_len; | |
483 | current_insn += expr_len; | |
484 | ||
485 | frame->flags |= DWARF_FRAME_CFA_REG_EXP; | |
486 | break; | |
487 | case DW_CFA_offset_extended_sf: | |
488 | count = dwarf_read_uleb128(current_insn, ®); | |
489 | current_insn += count; | |
490 | count = dwarf_read_leb128(current_insn, &offset); | |
491 | current_insn += count; | |
492 | offset *= cie->data_alignment_factor; | |
fb3f3e7f MF |
493 | regp = dwarf_frame_alloc_reg(frame, reg); |
494 | regp->flags |= DWARF_REG_OFFSET; | |
495 | regp->addr = offset; | |
bd353861 MF |
496 | break; |
497 | case DW_CFA_val_offset: | |
498 | count = dwarf_read_uleb128(current_insn, ®); | |
499 | current_insn += count; | |
500 | count = dwarf_read_leb128(current_insn, &offset); | |
501 | offset *= cie->data_alignment_factor; | |
fb3f3e7f | 502 | regp = dwarf_frame_alloc_reg(frame, reg); |
97efbbd5 | 503 | regp->flags |= DWARF_VAL_OFFSET; |
fb3f3e7f | 504 | regp->addr = offset; |
bd353861 | 505 | break; |
cd7246f0 MF |
506 | case DW_CFA_GNU_args_size: |
507 | count = dwarf_read_uleb128(current_insn, &offset); | |
508 | current_insn += count; | |
509 | break; | |
510 | case DW_CFA_GNU_negative_offset_extended: | |
511 | count = dwarf_read_uleb128(current_insn, ®); | |
512 | current_insn += count; | |
513 | count = dwarf_read_uleb128(current_insn, &offset); | |
514 | offset *= cie->data_alignment_factor; | |
fb3f3e7f MF |
515 | |
516 | regp = dwarf_frame_alloc_reg(frame, reg); | |
517 | regp->flags |= DWARF_REG_OFFSET; | |
518 | regp->addr = -offset; | |
cd7246f0 | 519 | break; |
bd353861 MF |
520 | default: |
521 | pr_debug("unhandled DWARF instruction 0x%x\n", insn); | |
522 | break; | |
523 | } | |
524 | } | |
525 | ||
526 | return 0; | |
527 | } | |
528 | ||
529 | /** | |
530 | * dwarf_unwind_stack - recursively unwind the stack | |
531 | * @pc: address of the function to unwind | |
532 | * @prev: struct dwarf_frame of the previous stackframe on the callstack | |
533 | * | |
534 | * Return a struct dwarf_frame representing the most recent frame | |
535 | * on the callstack. Each of the lower (older) stack frames are | |
536 | * linked via the "prev" member. | |
537 | */ | |
538 | struct dwarf_frame *dwarf_unwind_stack(unsigned long pc, | |
539 | struct dwarf_frame *prev) | |
540 | { | |
541 | struct dwarf_frame *frame; | |
542 | struct dwarf_cie *cie; | |
543 | struct dwarf_fde *fde; | |
fb3f3e7f | 544 | struct dwarf_reg *reg; |
bd353861 | 545 | unsigned long addr; |
bd353861 MF |
546 | |
547 | /* | |
548 | * If this is the first invocation of this recursive function we | |
549 | * need get the contents of a physical register to get the CFA | |
550 | * in order to begin the virtual unwinding of the stack. | |
551 | * | |
f8264667 MF |
552 | * NOTE: the return address is guaranteed to be setup by the |
553 | * time this function makes its first function call. | |
bd353861 | 554 | */ |
b955873b MF |
555 | if (!pc && !prev) |
556 | pc = (unsigned long)current_text_addr(); | |
bd353861 | 557 | |
fb3f3e7f MF |
558 | frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC); |
559 | if (!frame) { | |
560 | printk(KERN_ERR "Unable to allocate a dwarf frame\n"); | |
561 | BUG(); | |
562 | } | |
bd353861 | 563 | |
fb3f3e7f MF |
564 | INIT_LIST_HEAD(&frame->reg_list); |
565 | frame->flags = 0; | |
bd353861 | 566 | frame->prev = prev; |
fb3f3e7f | 567 | frame->return_addr = 0; |
bd353861 MF |
568 | |
569 | fde = dwarf_lookup_fde(pc); | |
570 | if (!fde) { | |
571 | /* | |
572 | * This is our normal exit path - the one that stops the | |
573 | * recursion. There's two reasons why we might exit | |
574 | * here, | |
575 | * | |
576 | * a) pc has no asscociated DWARF frame info and so | |
577 | * we don't know how to unwind this frame. This is | |
578 | * usually the case when we're trying to unwind a | |
579 | * frame that was called from some assembly code | |
580 | * that has no DWARF info, e.g. syscalls. | |
581 | * | |
582 | * b) the DEBUG info for pc is bogus. There's | |
583 | * really no way to distinguish this case from the | |
584 | * case above, which sucks because we could print a | |
585 | * warning here. | |
586 | */ | |
fb3f3e7f | 587 | goto bail; |
bd353861 MF |
588 | } |
589 | ||
590 | cie = dwarf_lookup_cie(fde->cie_pointer); | |
591 | ||
592 | frame->pc = fde->initial_location; | |
593 | ||
594 | /* CIE initial instructions */ | |
595 | dwarf_cfa_execute_insns(cie->initial_instructions, | |
f8264667 | 596 | cie->instructions_end, cie, fde, |
b955873b | 597 | frame, pc); |
bd353861 MF |
598 | |
599 | /* FDE instructions */ | |
600 | dwarf_cfa_execute_insns(fde->instructions, fde->end, cie, | |
b955873b | 601 | fde, frame, pc); |
bd353861 MF |
602 | |
603 | /* Calculate the CFA */ | |
604 | switch (frame->flags) { | |
605 | case DWARF_FRAME_CFA_REG_OFFSET: | |
606 | if (prev) { | |
fb3f3e7f MF |
607 | reg = dwarf_frame_reg(prev, frame->cfa_register); |
608 | BUG_ON(!reg); | |
bd353861 | 609 | |
fb3f3e7f | 610 | addr = prev->cfa + reg->addr; |
bd353861 MF |
611 | frame->cfa = __raw_readl(addr); |
612 | ||
613 | } else { | |
614 | /* | |
615 | * Again, this is the first invocation of this | |
616 | * recurisve function. We need to physically | |
617 | * read the contents of a register in order to | |
618 | * get the Canonical Frame Address for this | |
619 | * function. | |
620 | */ | |
621 | frame->cfa = dwarf_read_arch_reg(frame->cfa_register); | |
622 | } | |
623 | ||
624 | frame->cfa += frame->cfa_offset; | |
625 | break; | |
626 | default: | |
627 | BUG(); | |
628 | } | |
629 | ||
630 | /* If we haven't seen the return address reg, we're screwed. */ | |
fb3f3e7f MF |
631 | reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG); |
632 | BUG_ON(!reg); | |
bd353861 | 633 | |
fb3f3e7f | 634 | addr = frame->cfa + reg->addr; |
bd353861 MF |
635 | frame->return_addr = __raw_readl(addr); |
636 | ||
bd353861 | 637 | return frame; |
fb3f3e7f MF |
638 | |
639 | bail: | |
640 | dwarf_frame_free_regs(frame); | |
641 | mempool_free(frame, dwarf_frame_pool); | |
642 | return NULL; | |
bd353861 MF |
643 | } |
644 | ||
645 | static int dwarf_parse_cie(void *entry, void *p, unsigned long len, | |
646 | unsigned char *end) | |
647 | { | |
648 | struct dwarf_cie *cie; | |
649 | unsigned long flags; | |
650 | int count; | |
651 | ||
652 | cie = kzalloc(sizeof(*cie), GFP_KERNEL); | |
653 | if (!cie) | |
654 | return -ENOMEM; | |
655 | ||
656 | cie->length = len; | |
657 | ||
658 | /* | |
659 | * Record the offset into the .eh_frame section | |
660 | * for this CIE. It allows this CIE to be | |
661 | * quickly and easily looked up from the | |
662 | * corresponding FDE. | |
663 | */ | |
664 | cie->cie_pointer = (unsigned long)entry; | |
665 | ||
666 | cie->version = *(char *)p++; | |
667 | BUG_ON(cie->version != 1); | |
668 | ||
669 | cie->augmentation = p; | |
670 | p += strlen(cie->augmentation) + 1; | |
671 | ||
672 | count = dwarf_read_uleb128(p, &cie->code_alignment_factor); | |
673 | p += count; | |
674 | ||
675 | count = dwarf_read_leb128(p, &cie->data_alignment_factor); | |
676 | p += count; | |
677 | ||
678 | /* | |
679 | * Which column in the rule table contains the | |
680 | * return address? | |
681 | */ | |
682 | if (cie->version == 1) { | |
683 | cie->return_address_reg = __raw_readb(p); | |
684 | p++; | |
685 | } else { | |
686 | count = dwarf_read_uleb128(p, &cie->return_address_reg); | |
687 | p += count; | |
688 | } | |
689 | ||
690 | if (cie->augmentation[0] == 'z') { | |
691 | unsigned int length, count; | |
692 | cie->flags |= DWARF_CIE_Z_AUGMENTATION; | |
693 | ||
694 | count = dwarf_read_uleb128(p, &length); | |
695 | p += count; | |
696 | ||
697 | BUG_ON((unsigned char *)p > end); | |
698 | ||
699 | cie->initial_instructions = p + length; | |
700 | cie->augmentation++; | |
701 | } | |
702 | ||
703 | while (*cie->augmentation) { | |
704 | /* | |
705 | * "L" indicates a byte showing how the | |
706 | * LSDA pointer is encoded. Skip it. | |
707 | */ | |
708 | if (*cie->augmentation == 'L') { | |
709 | p++; | |
710 | cie->augmentation++; | |
711 | } else if (*cie->augmentation == 'R') { | |
712 | /* | |
713 | * "R" indicates a byte showing | |
714 | * how FDE addresses are | |
715 | * encoded. | |
716 | */ | |
717 | cie->encoding = *(char *)p++; | |
718 | cie->augmentation++; | |
719 | } else if (*cie->augmentation == 'P') { | |
720 | /* | |
721 | * "R" indicates a personality | |
722 | * routine in the CIE | |
723 | * augmentation. | |
724 | */ | |
725 | BUG(); | |
726 | } else if (*cie->augmentation == 'S') { | |
727 | BUG(); | |
728 | } else { | |
729 | /* | |
730 | * Unknown augmentation. Assume | |
731 | * 'z' augmentation. | |
732 | */ | |
733 | p = cie->initial_instructions; | |
734 | BUG_ON(!p); | |
735 | break; | |
736 | } | |
737 | } | |
738 | ||
739 | cie->initial_instructions = p; | |
740 | cie->instructions_end = end; | |
741 | ||
742 | /* Add to list */ | |
743 | spin_lock_irqsave(&dwarf_cie_lock, flags); | |
744 | list_add_tail(&cie->link, &dwarf_cie_list); | |
745 | spin_unlock_irqrestore(&dwarf_cie_lock, flags); | |
746 | ||
747 | return 0; | |
748 | } | |
749 | ||
750 | static int dwarf_parse_fde(void *entry, u32 entry_type, | |
751 | void *start, unsigned long len) | |
752 | { | |
753 | struct dwarf_fde *fde; | |
754 | struct dwarf_cie *cie; | |
755 | unsigned long flags; | |
756 | int count; | |
757 | void *p = start; | |
758 | ||
759 | fde = kzalloc(sizeof(*fde), GFP_KERNEL); | |
760 | if (!fde) | |
761 | return -ENOMEM; | |
762 | ||
763 | fde->length = len; | |
764 | ||
765 | /* | |
766 | * In a .eh_frame section the CIE pointer is the | |
767 | * delta between the address within the FDE | |
768 | */ | |
769 | fde->cie_pointer = (unsigned long)(p - entry_type - 4); | |
770 | ||
771 | cie = dwarf_lookup_cie(fde->cie_pointer); | |
772 | fde->cie = cie; | |
773 | ||
774 | if (cie->encoding) | |
775 | count = dwarf_read_encoded_value(p, &fde->initial_location, | |
776 | cie->encoding); | |
777 | else | |
778 | count = dwarf_read_addr(p, &fde->initial_location); | |
779 | ||
780 | p += count; | |
781 | ||
782 | if (cie->encoding) | |
783 | count = dwarf_read_encoded_value(p, &fde->address_range, | |
784 | cie->encoding & 0x0f); | |
785 | else | |
786 | count = dwarf_read_addr(p, &fde->address_range); | |
787 | ||
788 | p += count; | |
789 | ||
790 | if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) { | |
791 | unsigned int length; | |
792 | count = dwarf_read_uleb128(p, &length); | |
793 | p += count + length; | |
794 | } | |
795 | ||
796 | /* Call frame instructions. */ | |
797 | fde->instructions = p; | |
798 | fde->end = start + len; | |
799 | ||
800 | /* Add to list. */ | |
801 | spin_lock_irqsave(&dwarf_fde_lock, flags); | |
802 | list_add_tail(&fde->link, &dwarf_fde_list); | |
803 | spin_unlock_irqrestore(&dwarf_fde_lock, flags); | |
804 | ||
805 | return 0; | |
806 | } | |
807 | ||
808 | static void dwarf_unwinder_dump(struct task_struct *task, struct pt_regs *regs, | |
809 | unsigned long *sp, | |
810 | const struct stacktrace_ops *ops, void *data) | |
811 | { | |
fb3f3e7f MF |
812 | struct dwarf_frame *frame, *_frame; |
813 | unsigned long return_addr; | |
814 | ||
815 | _frame = NULL; | |
816 | return_addr = 0; | |
bd353861 | 817 | |
fb3f3e7f MF |
818 | while (1) { |
819 | frame = dwarf_unwind_stack(return_addr, _frame); | |
820 | ||
821 | if (_frame) { | |
822 | dwarf_frame_free_regs(_frame); | |
823 | mempool_free(_frame, dwarf_frame_pool); | |
824 | } | |
825 | ||
826 | _frame = frame; | |
827 | ||
828 | if (!frame || !frame->return_addr) | |
829 | break; | |
bd353861 | 830 | |
fb3f3e7f MF |
831 | return_addr = frame->return_addr; |
832 | ops->address(data, return_addr, 1); | |
bd353861 | 833 | } |
fb3f3e7f | 834 | |
bd353861 MF |
835 | } |
836 | ||
837 | static struct unwinder dwarf_unwinder = { | |
838 | .name = "dwarf-unwinder", | |
839 | .dump = dwarf_unwinder_dump, | |
840 | .rating = 150, | |
841 | }; | |
842 | ||
843 | static void dwarf_unwinder_cleanup(void) | |
844 | { | |
97f361e2 PM |
845 | struct dwarf_cie *cie; |
846 | struct dwarf_fde *fde; | |
bd353861 MF |
847 | |
848 | /* | |
849 | * Deallocate all the memory allocated for the DWARF unwinder. | |
850 | * Traverse all the FDE/CIE lists and remove and free all the | |
851 | * memory associated with those data structures. | |
852 | */ | |
97f361e2 | 853 | list_for_each_entry(cie, &dwarf_cie_list, link) |
bd353861 | 854 | kfree(cie); |
bd353861 | 855 | |
97f361e2 | 856 | list_for_each_entry(fde, &dwarf_fde_list, link) |
bd353861 | 857 | kfree(fde); |
fb3f3e7f MF |
858 | |
859 | kmem_cache_destroy(dwarf_reg_cachep); | |
860 | kmem_cache_destroy(dwarf_frame_cachep); | |
bd353861 MF |
861 | } |
862 | ||
863 | /** | |
864 | * dwarf_unwinder_init - initialise the dwarf unwinder | |
865 | * | |
866 | * Build the data structures describing the .dwarf_frame section to | |
867 | * make it easier to lookup CIE and FDE entries. Because the | |
868 | * .eh_frame section is packed as tightly as possible it is not | |
869 | * easy to lookup the FDE for a given PC, so we build a list of FDE | |
870 | * and CIE entries that make it easier. | |
871 | */ | |
97f361e2 | 872 | static int __init dwarf_unwinder_init(void) |
bd353861 MF |
873 | { |
874 | u32 entry_type; | |
875 | void *p, *entry; | |
876 | int count, err; | |
877 | unsigned long len; | |
878 | unsigned int c_entries, f_entries; | |
879 | unsigned char *end; | |
880 | INIT_LIST_HEAD(&dwarf_cie_list); | |
881 | INIT_LIST_HEAD(&dwarf_fde_list); | |
882 | ||
883 | c_entries = 0; | |
884 | f_entries = 0; | |
885 | entry = &__start_eh_frame; | |
886 | ||
fb3f3e7f MF |
887 | dwarf_frame_cachep = kmem_cache_create("dwarf_frames", |
888 | sizeof(struct dwarf_frame), 0, SLAB_PANIC, NULL); | |
889 | dwarf_reg_cachep = kmem_cache_create("dwarf_regs", | |
890 | sizeof(struct dwarf_reg), 0, SLAB_PANIC, NULL); | |
891 | ||
892 | dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ, | |
893 | mempool_alloc_slab, | |
894 | mempool_free_slab, | |
895 | dwarf_frame_cachep); | |
896 | ||
897 | dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ, | |
898 | mempool_alloc_slab, | |
899 | mempool_free_slab, | |
900 | dwarf_reg_cachep); | |
901 | ||
bd353861 MF |
902 | while ((char *)entry < __stop_eh_frame) { |
903 | p = entry; | |
904 | ||
905 | count = dwarf_entry_len(p, &len); | |
906 | if (count == 0) { | |
907 | /* | |
908 | * We read a bogus length field value. There is | |
909 | * nothing we can do here apart from disabling | |
910 | * the DWARF unwinder. We can't even skip this | |
911 | * entry and move to the next one because 'len' | |
912 | * tells us where our next entry is. | |
913 | */ | |
914 | goto out; | |
915 | } else | |
916 | p += count; | |
917 | ||
918 | /* initial length does not include itself */ | |
919 | end = p + len; | |
920 | ||
3497447f | 921 | entry_type = get_unaligned((u32 *)p); |
bd353861 MF |
922 | p += 4; |
923 | ||
924 | if (entry_type == DW_EH_FRAME_CIE) { | |
925 | err = dwarf_parse_cie(entry, p, len, end); | |
926 | if (err < 0) | |
927 | goto out; | |
928 | else | |
929 | c_entries++; | |
930 | } else { | |
931 | err = dwarf_parse_fde(entry, entry_type, p, len); | |
932 | if (err < 0) | |
933 | goto out; | |
934 | else | |
935 | f_entries++; | |
936 | } | |
937 | ||
938 | entry = (char *)entry + len + 4; | |
939 | } | |
940 | ||
941 | printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n", | |
942 | c_entries, f_entries); | |
943 | ||
944 | err = unwinder_register(&dwarf_unwinder); | |
945 | if (err) | |
946 | goto out; | |
947 | ||
97f361e2 | 948 | return 0; |
bd353861 MF |
949 | |
950 | out: | |
951 | printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err); | |
952 | dwarf_unwinder_cleanup(); | |
97f361e2 | 953 | return -EINVAL; |
bd353861 | 954 | } |
97f361e2 | 955 | early_initcall(dwarf_unwinder_init); |