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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 | 22 | #include <linux/mm.h> |
5a3abba7 | 23 | #include <linux/elf.h> |
60339fad | 24 | #include <linux/ftrace.h> |
bd353861 MF |
25 | #include <asm/dwarf.h> |
26 | #include <asm/unwinder.h> | |
27 | #include <asm/sections.h> | |
3497447f | 28 | #include <asm/unaligned.h> |
bd353861 MF |
29 | #include <asm/stacktrace.h> |
30 | ||
fb3f3e7f MF |
31 | /* Reserve enough memory for two stack frames */ |
32 | #define DWARF_FRAME_MIN_REQ 2 | |
33 | /* ... with 4 registers per frame. */ | |
34 | #define DWARF_REG_MIN_REQ (DWARF_FRAME_MIN_REQ * 4) | |
35 | ||
36 | static struct kmem_cache *dwarf_frame_cachep; | |
37 | static mempool_t *dwarf_frame_pool; | |
38 | ||
39 | static struct kmem_cache *dwarf_reg_cachep; | |
40 | static mempool_t *dwarf_reg_pool; | |
41 | ||
bd353861 | 42 | static LIST_HEAD(dwarf_cie_list); |
97f361e2 | 43 | static DEFINE_SPINLOCK(dwarf_cie_lock); |
bd353861 MF |
44 | |
45 | static LIST_HEAD(dwarf_fde_list); | |
97f361e2 | 46 | static DEFINE_SPINLOCK(dwarf_fde_lock); |
bd353861 MF |
47 | |
48 | static struct dwarf_cie *cached_cie; | |
49 | ||
fb3f3e7f MF |
50 | /** |
51 | * dwarf_frame_alloc_reg - allocate memory for a DWARF register | |
52 | * @frame: the DWARF frame whose list of registers we insert on | |
53 | * @reg_num: the register number | |
54 | * | |
55 | * Allocate space for, and initialise, a dwarf reg from | |
56 | * dwarf_reg_pool and insert it onto the (unsorted) linked-list of | |
57 | * dwarf registers for @frame. | |
bd353861 | 58 | * |
fb3f3e7f | 59 | * Return the initialised DWARF reg. |
bd353861 | 60 | */ |
fb3f3e7f MF |
61 | static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame, |
62 | unsigned int reg_num) | |
bd353861 | 63 | { |
fb3f3e7f | 64 | struct dwarf_reg *reg; |
bd353861 | 65 | |
fb3f3e7f MF |
66 | reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC); |
67 | if (!reg) { | |
68 | printk(KERN_WARNING "Unable to allocate a DWARF register\n"); | |
bd353861 MF |
69 | /* |
70 | * Let's just bomb hard here, we have no way to | |
71 | * gracefully recover. | |
72 | */ | |
b344e24a | 73 | UNWINDER_BUG(); |
bd353861 MF |
74 | } |
75 | ||
fb3f3e7f MF |
76 | reg->number = reg_num; |
77 | reg->addr = 0; | |
78 | reg->flags = 0; | |
79 | ||
80 | list_add(®->link, &frame->reg_list); | |
81 | ||
82 | return reg; | |
83 | } | |
84 | ||
85 | static void dwarf_frame_free_regs(struct dwarf_frame *frame) | |
86 | { | |
87 | struct dwarf_reg *reg, *n; | |
88 | ||
89 | list_for_each_entry_safe(reg, n, &frame->reg_list, link) { | |
90 | list_del(®->link); | |
91 | mempool_free(reg, dwarf_reg_pool); | |
92 | } | |
93 | } | |
94 | ||
95 | /** | |
96 | * dwarf_frame_reg - return a DWARF register | |
97 | * @frame: the DWARF frame to search in for @reg_num | |
98 | * @reg_num: the register number to search for | |
99 | * | |
100 | * Lookup and return the dwarf reg @reg_num for this frame. Return | |
101 | * NULL if @reg_num is an register invalid number. | |
102 | */ | |
103 | static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame, | |
104 | unsigned int reg_num) | |
105 | { | |
106 | struct dwarf_reg *reg; | |
107 | ||
108 | list_for_each_entry(reg, &frame->reg_list, link) { | |
109 | if (reg->number == reg_num) | |
110 | return reg; | |
bd353861 MF |
111 | } |
112 | ||
fb3f3e7f | 113 | return NULL; |
bd353861 MF |
114 | } |
115 | ||
116 | /** | |
117 | * dwarf_read_addr - read dwarf data | |
118 | * @src: source address of data | |
119 | * @dst: destination address to store the data to | |
120 | * | |
121 | * Read 'n' bytes from @src, where 'n' is the size of an address on | |
122 | * the native machine. We return the number of bytes read, which | |
123 | * should always be 'n'. We also have to be careful when reading | |
124 | * from @src and writing to @dst, because they can be arbitrarily | |
125 | * aligned. Return 'n' - the number of bytes read. | |
126 | */ | |
3497447f | 127 | static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst) |
bd353861 | 128 | { |
bf43a160 PM |
129 | u32 val = get_unaligned(src); |
130 | put_unaligned(val, dst); | |
bd353861 MF |
131 | return sizeof(unsigned long *); |
132 | } | |
133 | ||
134 | /** | |
135 | * dwarf_read_uleb128 - read unsigned LEB128 data | |
136 | * @addr: the address where the ULEB128 data is stored | |
137 | * @ret: address to store the result | |
138 | * | |
139 | * Decode an unsigned LEB128 encoded datum. The algorithm is taken | |
140 | * from Appendix C of the DWARF 3 spec. For information on the | |
141 | * encodings refer to section "7.6 - Variable Length Data". Return | |
142 | * the number of bytes read. | |
143 | */ | |
144 | static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret) | |
145 | { | |
146 | unsigned int result; | |
147 | unsigned char byte; | |
148 | int shift, count; | |
149 | ||
150 | result = 0; | |
151 | shift = 0; | |
152 | count = 0; | |
153 | ||
154 | while (1) { | |
155 | byte = __raw_readb(addr); | |
156 | addr++; | |
157 | count++; | |
158 | ||
159 | result |= (byte & 0x7f) << shift; | |
160 | shift += 7; | |
161 | ||
162 | if (!(byte & 0x80)) | |
163 | break; | |
164 | } | |
165 | ||
166 | *ret = result; | |
167 | ||
168 | return count; | |
169 | } | |
170 | ||
171 | /** | |
172 | * dwarf_read_leb128 - read signed LEB128 data | |
173 | * @addr: the address of the LEB128 encoded data | |
174 | * @ret: address to store the result | |
175 | * | |
176 | * Decode signed LEB128 data. The algorithm is taken from Appendix | |
177 | * C of the DWARF 3 spec. Return the number of bytes read. | |
178 | */ | |
179 | static inline unsigned long dwarf_read_leb128(char *addr, int *ret) | |
180 | { | |
181 | unsigned char byte; | |
182 | int result, shift; | |
183 | int num_bits; | |
184 | int count; | |
185 | ||
186 | result = 0; | |
187 | shift = 0; | |
188 | count = 0; | |
189 | ||
190 | while (1) { | |
191 | byte = __raw_readb(addr); | |
192 | addr++; | |
193 | result |= (byte & 0x7f) << shift; | |
194 | shift += 7; | |
195 | count++; | |
196 | ||
197 | if (!(byte & 0x80)) | |
198 | break; | |
199 | } | |
200 | ||
201 | /* The number of bits in a signed integer. */ | |
202 | num_bits = 8 * sizeof(result); | |
203 | ||
204 | if ((shift < num_bits) && (byte & 0x40)) | |
205 | result |= (-1 << shift); | |
206 | ||
207 | *ret = result; | |
208 | ||
209 | return count; | |
210 | } | |
211 | ||
212 | /** | |
213 | * dwarf_read_encoded_value - return the decoded value at @addr | |
214 | * @addr: the address of the encoded value | |
215 | * @val: where to write the decoded value | |
216 | * @encoding: the encoding with which we can decode @addr | |
217 | * | |
218 | * GCC emits encoded address in the .eh_frame FDE entries. Decode | |
219 | * the value at @addr using @encoding. The decoded value is written | |
220 | * to @val and the number of bytes read is returned. | |
221 | */ | |
222 | static int dwarf_read_encoded_value(char *addr, unsigned long *val, | |
223 | char encoding) | |
224 | { | |
225 | unsigned long decoded_addr = 0; | |
226 | int count = 0; | |
227 | ||
228 | switch (encoding & 0x70) { | |
229 | case DW_EH_PE_absptr: | |
230 | break; | |
231 | case DW_EH_PE_pcrel: | |
232 | decoded_addr = (unsigned long)addr; | |
233 | break; | |
234 | default: | |
235 | pr_debug("encoding=0x%x\n", (encoding & 0x70)); | |
b344e24a | 236 | UNWINDER_BUG(); |
bd353861 MF |
237 | } |
238 | ||
239 | if ((encoding & 0x07) == 0x00) | |
240 | encoding |= DW_EH_PE_udata4; | |
241 | ||
242 | switch (encoding & 0x0f) { | |
243 | case DW_EH_PE_sdata4: | |
244 | case DW_EH_PE_udata4: | |
245 | count += 4; | |
3497447f | 246 | decoded_addr += get_unaligned((u32 *)addr); |
bd353861 MF |
247 | __raw_writel(decoded_addr, val); |
248 | break; | |
249 | default: | |
250 | pr_debug("encoding=0x%x\n", encoding); | |
b344e24a | 251 | UNWINDER_BUG(); |
bd353861 MF |
252 | } |
253 | ||
254 | return count; | |
255 | } | |
256 | ||
257 | /** | |
258 | * dwarf_entry_len - return the length of an FDE or CIE | |
259 | * @addr: the address of the entry | |
260 | * @len: the length of the entry | |
261 | * | |
262 | * Read the initial_length field of the entry and store the size of | |
263 | * the entry in @len. We return the number of bytes read. Return a | |
264 | * count of 0 on error. | |
265 | */ | |
266 | static inline int dwarf_entry_len(char *addr, unsigned long *len) | |
267 | { | |
268 | u32 initial_len; | |
269 | int count; | |
270 | ||
3497447f | 271 | initial_len = get_unaligned((u32 *)addr); |
bd353861 MF |
272 | count = 4; |
273 | ||
274 | /* | |
275 | * An initial length field value in the range DW_LEN_EXT_LO - | |
276 | * DW_LEN_EXT_HI indicates an extension, and should not be | |
277 | * interpreted as a length. The only extension that we currently | |
278 | * understand is the use of DWARF64 addresses. | |
279 | */ | |
280 | if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) { | |
281 | /* | |
282 | * The 64-bit length field immediately follows the | |
283 | * compulsory 32-bit length field. | |
284 | */ | |
285 | if (initial_len == DW_EXT_DWARF64) { | |
3497447f | 286 | *len = get_unaligned((u64 *)addr + 4); |
bd353861 MF |
287 | count = 12; |
288 | } else { | |
289 | printk(KERN_WARNING "Unknown DWARF extension\n"); | |
290 | count = 0; | |
291 | } | |
292 | } else | |
293 | *len = initial_len; | |
294 | ||
295 | return count; | |
296 | } | |
297 | ||
298 | /** | |
299 | * dwarf_lookup_cie - locate the cie | |
300 | * @cie_ptr: pointer to help with lookup | |
301 | */ | |
302 | static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr) | |
303 | { | |
97f361e2 | 304 | struct dwarf_cie *cie; |
bd353861 MF |
305 | unsigned long flags; |
306 | ||
307 | spin_lock_irqsave(&dwarf_cie_lock, flags); | |
308 | ||
309 | /* | |
310 | * We've cached the last CIE we looked up because chances are | |
311 | * that the FDE wants this CIE. | |
312 | */ | |
313 | if (cached_cie && cached_cie->cie_pointer == cie_ptr) { | |
314 | cie = cached_cie; | |
315 | goto out; | |
316 | } | |
317 | ||
97f361e2 | 318 | list_for_each_entry(cie, &dwarf_cie_list, link) { |
bd353861 MF |
319 | if (cie->cie_pointer == cie_ptr) { |
320 | cached_cie = cie; | |
321 | break; | |
322 | } | |
323 | } | |
324 | ||
325 | /* Couldn't find the entry in the list. */ | |
326 | if (&cie->link == &dwarf_cie_list) | |
327 | cie = NULL; | |
328 | out: | |
329 | spin_unlock_irqrestore(&dwarf_cie_lock, flags); | |
330 | return cie; | |
331 | } | |
332 | ||
333 | /** | |
334 | * dwarf_lookup_fde - locate the FDE that covers pc | |
335 | * @pc: the program counter | |
336 | */ | |
337 | struct dwarf_fde *dwarf_lookup_fde(unsigned long pc) | |
338 | { | |
97f361e2 | 339 | struct dwarf_fde *fde; |
bd353861 | 340 | unsigned long flags; |
bd353861 MF |
341 | |
342 | spin_lock_irqsave(&dwarf_fde_lock, flags); | |
97f361e2 PM |
343 | |
344 | list_for_each_entry(fde, &dwarf_fde_list, link) { | |
bd353861 MF |
345 | unsigned long start, end; |
346 | ||
347 | start = fde->initial_location; | |
348 | end = fde->initial_location + fde->address_range; | |
349 | ||
350 | if (pc >= start && pc < end) | |
351 | break; | |
352 | } | |
353 | ||
354 | /* Couldn't find the entry in the list. */ | |
355 | if (&fde->link == &dwarf_fde_list) | |
356 | fde = NULL; | |
357 | ||
358 | spin_unlock_irqrestore(&dwarf_fde_lock, flags); | |
359 | ||
360 | return fde; | |
361 | } | |
362 | ||
363 | /** | |
364 | * dwarf_cfa_execute_insns - execute instructions to calculate a CFA | |
365 | * @insn_start: address of the first instruction | |
366 | * @insn_end: address of the last instruction | |
367 | * @cie: the CIE for this function | |
368 | * @fde: the FDE for this function | |
369 | * @frame: the instructions calculate the CFA for this frame | |
370 | * @pc: the program counter of the address we're interested in | |
371 | * | |
372 | * Execute the Call Frame instruction sequence starting at | |
373 | * @insn_start and ending at @insn_end. The instructions describe | |
374 | * how to calculate the Canonical Frame Address of a stackframe. | |
375 | * Store the results in @frame. | |
376 | */ | |
377 | static int dwarf_cfa_execute_insns(unsigned char *insn_start, | |
378 | unsigned char *insn_end, | |
379 | struct dwarf_cie *cie, | |
380 | struct dwarf_fde *fde, | |
381 | struct dwarf_frame *frame, | |
b955873b | 382 | unsigned long pc) |
bd353861 MF |
383 | { |
384 | unsigned char insn; | |
385 | unsigned char *current_insn; | |
386 | unsigned int count, delta, reg, expr_len, offset; | |
fb3f3e7f | 387 | struct dwarf_reg *regp; |
bd353861 MF |
388 | |
389 | current_insn = insn_start; | |
390 | ||
b955873b | 391 | while (current_insn < insn_end && frame->pc <= pc) { |
bd353861 MF |
392 | insn = __raw_readb(current_insn++); |
393 | ||
394 | /* | |
395 | * Firstly, handle the opcodes that embed their operands | |
396 | * in the instructions. | |
397 | */ | |
398 | switch (DW_CFA_opcode(insn)) { | |
399 | case DW_CFA_advance_loc: | |
400 | delta = DW_CFA_operand(insn); | |
401 | delta *= cie->code_alignment_factor; | |
402 | frame->pc += delta; | |
403 | continue; | |
404 | /* NOTREACHED */ | |
405 | case DW_CFA_offset: | |
406 | reg = DW_CFA_operand(insn); | |
407 | count = dwarf_read_uleb128(current_insn, &offset); | |
408 | current_insn += count; | |
409 | offset *= cie->data_alignment_factor; | |
fb3f3e7f MF |
410 | regp = dwarf_frame_alloc_reg(frame, reg); |
411 | regp->addr = offset; | |
412 | regp->flags |= DWARF_REG_OFFSET; | |
bd353861 MF |
413 | continue; |
414 | /* NOTREACHED */ | |
415 | case DW_CFA_restore: | |
416 | reg = DW_CFA_operand(insn); | |
417 | continue; | |
418 | /* NOTREACHED */ | |
419 | } | |
420 | ||
421 | /* | |
422 | * Secondly, handle the opcodes that don't embed their | |
423 | * operands in the instruction. | |
424 | */ | |
425 | switch (insn) { | |
426 | case DW_CFA_nop: | |
427 | continue; | |
428 | case DW_CFA_advance_loc1: | |
429 | delta = *current_insn++; | |
430 | frame->pc += delta * cie->code_alignment_factor; | |
431 | break; | |
432 | case DW_CFA_advance_loc2: | |
3497447f | 433 | delta = get_unaligned((u16 *)current_insn); |
bd353861 MF |
434 | current_insn += 2; |
435 | frame->pc += delta * cie->code_alignment_factor; | |
436 | break; | |
437 | case DW_CFA_advance_loc4: | |
3497447f | 438 | delta = get_unaligned((u32 *)current_insn); |
bd353861 MF |
439 | current_insn += 4; |
440 | frame->pc += delta * cie->code_alignment_factor; | |
441 | break; | |
442 | case DW_CFA_offset_extended: | |
443 | count = dwarf_read_uleb128(current_insn, ®); | |
444 | current_insn += count; | |
445 | count = dwarf_read_uleb128(current_insn, &offset); | |
446 | current_insn += count; | |
447 | offset *= cie->data_alignment_factor; | |
448 | break; | |
449 | case DW_CFA_restore_extended: | |
450 | count = dwarf_read_uleb128(current_insn, ®); | |
451 | current_insn += count; | |
452 | break; | |
453 | case DW_CFA_undefined: | |
454 | count = dwarf_read_uleb128(current_insn, ®); | |
455 | current_insn += count; | |
5580e904 MF |
456 | regp = dwarf_frame_alloc_reg(frame, reg); |
457 | regp->flags |= DWARF_UNDEFINED; | |
bd353861 MF |
458 | break; |
459 | case DW_CFA_def_cfa: | |
460 | count = dwarf_read_uleb128(current_insn, | |
461 | &frame->cfa_register); | |
462 | current_insn += count; | |
463 | count = dwarf_read_uleb128(current_insn, | |
464 | &frame->cfa_offset); | |
465 | current_insn += count; | |
466 | ||
467 | frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; | |
468 | break; | |
469 | case DW_CFA_def_cfa_register: | |
470 | count = dwarf_read_uleb128(current_insn, | |
471 | &frame->cfa_register); | |
472 | current_insn += count; | |
473 | frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; | |
474 | break; | |
475 | case DW_CFA_def_cfa_offset: | |
476 | count = dwarf_read_uleb128(current_insn, &offset); | |
477 | current_insn += count; | |
478 | frame->cfa_offset = offset; | |
479 | break; | |
480 | case DW_CFA_def_cfa_expression: | |
481 | count = dwarf_read_uleb128(current_insn, &expr_len); | |
482 | current_insn += count; | |
483 | ||
484 | frame->cfa_expr = current_insn; | |
485 | frame->cfa_expr_len = expr_len; | |
486 | current_insn += expr_len; | |
487 | ||
488 | frame->flags |= DWARF_FRAME_CFA_REG_EXP; | |
489 | break; | |
490 | case DW_CFA_offset_extended_sf: | |
491 | count = dwarf_read_uleb128(current_insn, ®); | |
492 | current_insn += count; | |
493 | count = dwarf_read_leb128(current_insn, &offset); | |
494 | current_insn += count; | |
495 | offset *= cie->data_alignment_factor; | |
fb3f3e7f MF |
496 | regp = dwarf_frame_alloc_reg(frame, reg); |
497 | regp->flags |= DWARF_REG_OFFSET; | |
498 | regp->addr = offset; | |
bd353861 MF |
499 | break; |
500 | case DW_CFA_val_offset: | |
501 | count = dwarf_read_uleb128(current_insn, ®); | |
502 | current_insn += count; | |
503 | count = dwarf_read_leb128(current_insn, &offset); | |
504 | offset *= cie->data_alignment_factor; | |
fb3f3e7f | 505 | regp = dwarf_frame_alloc_reg(frame, reg); |
97efbbd5 | 506 | regp->flags |= DWARF_VAL_OFFSET; |
fb3f3e7f | 507 | regp->addr = offset; |
bd353861 | 508 | break; |
cd7246f0 MF |
509 | case DW_CFA_GNU_args_size: |
510 | count = dwarf_read_uleb128(current_insn, &offset); | |
511 | current_insn += count; | |
512 | break; | |
513 | case DW_CFA_GNU_negative_offset_extended: | |
514 | count = dwarf_read_uleb128(current_insn, ®); | |
515 | current_insn += count; | |
516 | count = dwarf_read_uleb128(current_insn, &offset); | |
517 | offset *= cie->data_alignment_factor; | |
fb3f3e7f MF |
518 | |
519 | regp = dwarf_frame_alloc_reg(frame, reg); | |
520 | regp->flags |= DWARF_REG_OFFSET; | |
521 | regp->addr = -offset; | |
cd7246f0 | 522 | break; |
bd353861 MF |
523 | default: |
524 | pr_debug("unhandled DWARF instruction 0x%x\n", insn); | |
b344e24a | 525 | UNWINDER_BUG(); |
bd353861 MF |
526 | break; |
527 | } | |
528 | } | |
529 | ||
530 | return 0; | |
531 | } | |
532 | ||
533 | /** | |
ed4fe7f4 MF |
534 | * dwarf_free_frame - free the memory allocated for @frame |
535 | * @frame: the frame to free | |
536 | */ | |
537 | void dwarf_free_frame(struct dwarf_frame *frame) | |
538 | { | |
539 | dwarf_frame_free_regs(frame); | |
540 | mempool_free(frame, dwarf_frame_pool); | |
541 | } | |
542 | ||
944a3438 MF |
543 | extern void ret_from_irq(void); |
544 | ||
bd353861 | 545 | /** |
c2d474d6 MF |
546 | * dwarf_unwind_stack - unwind the stack |
547 | * | |
bd353861 MF |
548 | * @pc: address of the function to unwind |
549 | * @prev: struct dwarf_frame of the previous stackframe on the callstack | |
550 | * | |
551 | * Return a struct dwarf_frame representing the most recent frame | |
552 | * on the callstack. Each of the lower (older) stack frames are | |
553 | * linked via the "prev" member. | |
554 | */ | |
b344e24a MF |
555 | struct dwarf_frame * dwarf_unwind_stack(unsigned long pc, |
556 | struct dwarf_frame *prev) | |
bd353861 MF |
557 | { |
558 | struct dwarf_frame *frame; | |
559 | struct dwarf_cie *cie; | |
560 | struct dwarf_fde *fde; | |
fb3f3e7f | 561 | struct dwarf_reg *reg; |
bd353861 | 562 | unsigned long addr; |
bd353861 MF |
563 | |
564 | /* | |
c2d474d6 MF |
565 | * If we're starting at the top of the stack we need get the |
566 | * contents of a physical register to get the CFA in order to | |
567 | * begin the virtual unwinding of the stack. | |
bd353861 | 568 | * |
f8264667 MF |
569 | * NOTE: the return address is guaranteed to be setup by the |
570 | * time this function makes its first function call. | |
bd353861 | 571 | */ |
421b5411 | 572 | if (!pc || !prev) |
b955873b | 573 | pc = (unsigned long)current_text_addr(); |
bd353861 | 574 | |
60339fad MF |
575 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
576 | /* | |
577 | * If our stack has been patched by the function graph tracer | |
578 | * then we might see the address of return_to_handler() where we | |
579 | * expected to find the real return address. | |
580 | */ | |
581 | if (pc == (unsigned long)&return_to_handler) { | |
582 | int index = current->curr_ret_stack; | |
583 | ||
584 | /* | |
585 | * We currently have no way of tracking how many | |
586 | * return_to_handler()'s we've seen. If there is more | |
587 | * than one patched return address on our stack, | |
588 | * complain loudly. | |
589 | */ | |
590 | WARN_ON(index > 0); | |
591 | ||
592 | pc = current->ret_stack[index].ret; | |
593 | } | |
594 | #endif | |
595 | ||
fb3f3e7f MF |
596 | frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC); |
597 | if (!frame) { | |
598 | printk(KERN_ERR "Unable to allocate a dwarf frame\n"); | |
b344e24a | 599 | UNWINDER_BUG(); |
fb3f3e7f | 600 | } |
bd353861 | 601 | |
fb3f3e7f MF |
602 | INIT_LIST_HEAD(&frame->reg_list); |
603 | frame->flags = 0; | |
bd353861 | 604 | frame->prev = prev; |
fb3f3e7f | 605 | frame->return_addr = 0; |
bd353861 MF |
606 | |
607 | fde = dwarf_lookup_fde(pc); | |
608 | if (!fde) { | |
609 | /* | |
c2d474d6 MF |
610 | * This is our normal exit path. There are two reasons |
611 | * why we might exit here, | |
bd353861 MF |
612 | * |
613 | * a) pc has no asscociated DWARF frame info and so | |
614 | * we don't know how to unwind this frame. This is | |
615 | * usually the case when we're trying to unwind a | |
616 | * frame that was called from some assembly code | |
617 | * that has no DWARF info, e.g. syscalls. | |
618 | * | |
619 | * b) the DEBUG info for pc is bogus. There's | |
620 | * really no way to distinguish this case from the | |
621 | * case above, which sucks because we could print a | |
622 | * warning here. | |
623 | */ | |
fb3f3e7f | 624 | goto bail; |
bd353861 MF |
625 | } |
626 | ||
627 | cie = dwarf_lookup_cie(fde->cie_pointer); | |
628 | ||
629 | frame->pc = fde->initial_location; | |
630 | ||
631 | /* CIE initial instructions */ | |
632 | dwarf_cfa_execute_insns(cie->initial_instructions, | |
f8264667 | 633 | cie->instructions_end, cie, fde, |
b955873b | 634 | frame, pc); |
bd353861 MF |
635 | |
636 | /* FDE instructions */ | |
637 | dwarf_cfa_execute_insns(fde->instructions, fde->end, cie, | |
b955873b | 638 | fde, frame, pc); |
bd353861 MF |
639 | |
640 | /* Calculate the CFA */ | |
641 | switch (frame->flags) { | |
642 | case DWARF_FRAME_CFA_REG_OFFSET: | |
643 | if (prev) { | |
fb3f3e7f | 644 | reg = dwarf_frame_reg(prev, frame->cfa_register); |
b344e24a MF |
645 | UNWINDER_BUG_ON(!reg); |
646 | UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET); | |
bd353861 | 647 | |
fb3f3e7f | 648 | addr = prev->cfa + reg->addr; |
bd353861 MF |
649 | frame->cfa = __raw_readl(addr); |
650 | ||
651 | } else { | |
652 | /* | |
c2d474d6 MF |
653 | * Again, we're starting from the top of the |
654 | * stack. We need to physically read | |
655 | * the contents of a register in order to get | |
656 | * the Canonical Frame Address for this | |
bd353861 MF |
657 | * function. |
658 | */ | |
659 | frame->cfa = dwarf_read_arch_reg(frame->cfa_register); | |
660 | } | |
661 | ||
662 | frame->cfa += frame->cfa_offset; | |
663 | break; | |
664 | default: | |
b344e24a | 665 | UNWINDER_BUG(); |
bd353861 MF |
666 | } |
667 | ||
fb3f3e7f | 668 | reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG); |
5580e904 MF |
669 | |
670 | /* | |
671 | * If we haven't seen the return address register or the return | |
672 | * address column is undefined then we must assume that this is | |
673 | * the end of the callstack. | |
674 | */ | |
675 | if (!reg || reg->flags == DWARF_UNDEFINED) | |
676 | goto bail; | |
677 | ||
b344e24a | 678 | UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET); |
bd353861 | 679 | |
fb3f3e7f | 680 | addr = frame->cfa + reg->addr; |
bd353861 MF |
681 | frame->return_addr = __raw_readl(addr); |
682 | ||
944a3438 MF |
683 | /* |
684 | * Ah, the joys of unwinding through interrupts. | |
685 | * | |
686 | * Interrupts are tricky - the DWARF info needs to be _really_ | |
687 | * accurate and unfortunately I'm seeing a lot of bogus DWARF | |
688 | * info. For example, I've seen interrupts occur in epilogues | |
689 | * just after the frame pointer (r14) had been restored. The | |
690 | * problem was that the DWARF info claimed that the CFA could be | |
691 | * reached by using the value of the frame pointer before it was | |
692 | * restored. | |
693 | * | |
694 | * So until the compiler can be trusted to produce reliable | |
695 | * DWARF info when it really matters, let's stop unwinding once | |
696 | * we've calculated the function that was interrupted. | |
697 | */ | |
698 | if (prev && prev->pc == (unsigned long)ret_from_irq) | |
699 | frame->return_addr = 0; | |
700 | ||
bd353861 | 701 | return frame; |
fb3f3e7f MF |
702 | |
703 | bail: | |
ed4fe7f4 | 704 | dwarf_free_frame(frame); |
fb3f3e7f | 705 | return NULL; |
bd353861 MF |
706 | } |
707 | ||
708 | static int dwarf_parse_cie(void *entry, void *p, unsigned long len, | |
a6a2f2ad | 709 | unsigned char *end, struct module *mod) |
bd353861 MF |
710 | { |
711 | struct dwarf_cie *cie; | |
712 | unsigned long flags; | |
713 | int count; | |
714 | ||
715 | cie = kzalloc(sizeof(*cie), GFP_KERNEL); | |
716 | if (!cie) | |
717 | return -ENOMEM; | |
718 | ||
719 | cie->length = len; | |
720 | ||
721 | /* | |
722 | * Record the offset into the .eh_frame section | |
723 | * for this CIE. It allows this CIE to be | |
724 | * quickly and easily looked up from the | |
725 | * corresponding FDE. | |
726 | */ | |
727 | cie->cie_pointer = (unsigned long)entry; | |
728 | ||
729 | cie->version = *(char *)p++; | |
b344e24a | 730 | UNWINDER_BUG_ON(cie->version != 1); |
bd353861 MF |
731 | |
732 | cie->augmentation = p; | |
733 | p += strlen(cie->augmentation) + 1; | |
734 | ||
735 | count = dwarf_read_uleb128(p, &cie->code_alignment_factor); | |
736 | p += count; | |
737 | ||
738 | count = dwarf_read_leb128(p, &cie->data_alignment_factor); | |
739 | p += count; | |
740 | ||
741 | /* | |
742 | * Which column in the rule table contains the | |
743 | * return address? | |
744 | */ | |
745 | if (cie->version == 1) { | |
746 | cie->return_address_reg = __raw_readb(p); | |
747 | p++; | |
748 | } else { | |
749 | count = dwarf_read_uleb128(p, &cie->return_address_reg); | |
750 | p += count; | |
751 | } | |
752 | ||
753 | if (cie->augmentation[0] == 'z') { | |
754 | unsigned int length, count; | |
755 | cie->flags |= DWARF_CIE_Z_AUGMENTATION; | |
756 | ||
757 | count = dwarf_read_uleb128(p, &length); | |
758 | p += count; | |
759 | ||
b344e24a | 760 | UNWINDER_BUG_ON((unsigned char *)p > end); |
bd353861 MF |
761 | |
762 | cie->initial_instructions = p + length; | |
763 | cie->augmentation++; | |
764 | } | |
765 | ||
766 | while (*cie->augmentation) { | |
767 | /* | |
768 | * "L" indicates a byte showing how the | |
769 | * LSDA pointer is encoded. Skip it. | |
770 | */ | |
771 | if (*cie->augmentation == 'L') { | |
772 | p++; | |
773 | cie->augmentation++; | |
774 | } else if (*cie->augmentation == 'R') { | |
775 | /* | |
776 | * "R" indicates a byte showing | |
777 | * how FDE addresses are | |
778 | * encoded. | |
779 | */ | |
780 | cie->encoding = *(char *)p++; | |
781 | cie->augmentation++; | |
782 | } else if (*cie->augmentation == 'P') { | |
783 | /* | |
784 | * "R" indicates a personality | |
785 | * routine in the CIE | |
786 | * augmentation. | |
787 | */ | |
b344e24a | 788 | UNWINDER_BUG(); |
bd353861 | 789 | } else if (*cie->augmentation == 'S') { |
b344e24a | 790 | UNWINDER_BUG(); |
bd353861 MF |
791 | } else { |
792 | /* | |
793 | * Unknown augmentation. Assume | |
794 | * 'z' augmentation. | |
795 | */ | |
796 | p = cie->initial_instructions; | |
b344e24a | 797 | UNWINDER_BUG_ON(!p); |
bd353861 MF |
798 | break; |
799 | } | |
800 | } | |
801 | ||
802 | cie->initial_instructions = p; | |
803 | cie->instructions_end = end; | |
804 | ||
a6a2f2ad MF |
805 | cie->mod = mod; |
806 | ||
bd353861 MF |
807 | /* Add to list */ |
808 | spin_lock_irqsave(&dwarf_cie_lock, flags); | |
809 | list_add_tail(&cie->link, &dwarf_cie_list); | |
810 | spin_unlock_irqrestore(&dwarf_cie_lock, flags); | |
811 | ||
812 | return 0; | |
813 | } | |
814 | ||
815 | static int dwarf_parse_fde(void *entry, u32 entry_type, | |
5480675d | 816 | void *start, unsigned long len, |
a6a2f2ad | 817 | unsigned char *end, struct module *mod) |
bd353861 MF |
818 | { |
819 | struct dwarf_fde *fde; | |
820 | struct dwarf_cie *cie; | |
821 | unsigned long flags; | |
822 | int count; | |
823 | void *p = start; | |
824 | ||
825 | fde = kzalloc(sizeof(*fde), GFP_KERNEL); | |
826 | if (!fde) | |
827 | return -ENOMEM; | |
828 | ||
829 | fde->length = len; | |
830 | ||
831 | /* | |
832 | * In a .eh_frame section the CIE pointer is the | |
833 | * delta between the address within the FDE | |
834 | */ | |
835 | fde->cie_pointer = (unsigned long)(p - entry_type - 4); | |
836 | ||
837 | cie = dwarf_lookup_cie(fde->cie_pointer); | |
838 | fde->cie = cie; | |
839 | ||
840 | if (cie->encoding) | |
841 | count = dwarf_read_encoded_value(p, &fde->initial_location, | |
842 | cie->encoding); | |
843 | else | |
844 | count = dwarf_read_addr(p, &fde->initial_location); | |
845 | ||
846 | p += count; | |
847 | ||
848 | if (cie->encoding) | |
849 | count = dwarf_read_encoded_value(p, &fde->address_range, | |
850 | cie->encoding & 0x0f); | |
851 | else | |
852 | count = dwarf_read_addr(p, &fde->address_range); | |
853 | ||
854 | p += count; | |
855 | ||
856 | if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) { | |
857 | unsigned int length; | |
858 | count = dwarf_read_uleb128(p, &length); | |
859 | p += count + length; | |
860 | } | |
861 | ||
862 | /* Call frame instructions. */ | |
863 | fde->instructions = p; | |
5480675d | 864 | fde->end = end; |
bd353861 | 865 | |
a6a2f2ad MF |
866 | fde->mod = mod; |
867 | ||
bd353861 MF |
868 | /* Add to list. */ |
869 | spin_lock_irqsave(&dwarf_fde_lock, flags); | |
870 | list_add_tail(&fde->link, &dwarf_fde_list); | |
871 | spin_unlock_irqrestore(&dwarf_fde_lock, flags); | |
872 | ||
873 | return 0; | |
874 | } | |
875 | ||
b344e24a MF |
876 | static void dwarf_unwinder_dump(struct task_struct *task, |
877 | struct pt_regs *regs, | |
bd353861 | 878 | unsigned long *sp, |
b344e24a MF |
879 | const struct stacktrace_ops *ops, |
880 | void *data) | |
bd353861 | 881 | { |
fb3f3e7f MF |
882 | struct dwarf_frame *frame, *_frame; |
883 | unsigned long return_addr; | |
884 | ||
885 | _frame = NULL; | |
886 | return_addr = 0; | |
bd353861 | 887 | |
fb3f3e7f MF |
888 | while (1) { |
889 | frame = dwarf_unwind_stack(return_addr, _frame); | |
890 | ||
ed4fe7f4 MF |
891 | if (_frame) |
892 | dwarf_free_frame(_frame); | |
fb3f3e7f MF |
893 | |
894 | _frame = frame; | |
895 | ||
896 | if (!frame || !frame->return_addr) | |
897 | break; | |
bd353861 | 898 | |
fb3f3e7f MF |
899 | return_addr = frame->return_addr; |
900 | ops->address(data, return_addr, 1); | |
bd353861 | 901 | } |
ed4fe7f4 MF |
902 | |
903 | if (frame) | |
904 | dwarf_free_frame(frame); | |
bd353861 MF |
905 | } |
906 | ||
907 | static struct unwinder dwarf_unwinder = { | |
908 | .name = "dwarf-unwinder", | |
909 | .dump = dwarf_unwinder_dump, | |
910 | .rating = 150, | |
911 | }; | |
912 | ||
913 | static void dwarf_unwinder_cleanup(void) | |
914 | { | |
00b3e0a2 MS |
915 | struct dwarf_cie *cie, *cie_tmp; |
916 | struct dwarf_fde *fde, *fde_tmp; | |
bd353861 MF |
917 | |
918 | /* | |
919 | * Deallocate all the memory allocated for the DWARF unwinder. | |
920 | * Traverse all the FDE/CIE lists and remove and free all the | |
921 | * memory associated with those data structures. | |
922 | */ | |
00b3e0a2 | 923 | list_for_each_entry_safe(cie, cie_tmp, &dwarf_cie_list, link) |
bd353861 | 924 | kfree(cie); |
bd353861 | 925 | |
00b3e0a2 | 926 | list_for_each_entry_safe(fde, fde_tmp, &dwarf_fde_list, link) |
bd353861 | 927 | kfree(fde); |
fb3f3e7f MF |
928 | |
929 | kmem_cache_destroy(dwarf_reg_cachep); | |
930 | kmem_cache_destroy(dwarf_frame_cachep); | |
bd353861 MF |
931 | } |
932 | ||
933 | /** | |
a6a2f2ad MF |
934 | * dwarf_parse_section - parse DWARF section |
935 | * @eh_frame_start: start address of the .eh_frame section | |
936 | * @eh_frame_end: end address of the .eh_frame section | |
937 | * @mod: the kernel module containing the .eh_frame section | |
bd353861 | 938 | * |
a6a2f2ad | 939 | * Parse the information in a .eh_frame section. |
bd353861 | 940 | */ |
5a3abba7 PM |
941 | static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end, |
942 | struct module *mod) | |
bd353861 MF |
943 | { |
944 | u32 entry_type; | |
945 | void *p, *entry; | |
2f6dafc5 | 946 | int count, err = 0; |
eca28e37 | 947 | unsigned long len = 0; |
bd353861 MF |
948 | unsigned int c_entries, f_entries; |
949 | unsigned char *end; | |
bd353861 MF |
950 | |
951 | c_entries = 0; | |
952 | f_entries = 0; | |
a6a2f2ad | 953 | entry = eh_frame_start; |
fb3f3e7f | 954 | |
a6a2f2ad | 955 | while ((char *)entry < eh_frame_end) { |
bd353861 MF |
956 | p = entry; |
957 | ||
958 | count = dwarf_entry_len(p, &len); | |
959 | if (count == 0) { | |
960 | /* | |
961 | * We read a bogus length field value. There is | |
962 | * nothing we can do here apart from disabling | |
963 | * the DWARF unwinder. We can't even skip this | |
964 | * entry and move to the next one because 'len' | |
965 | * tells us where our next entry is. | |
966 | */ | |
a6a2f2ad | 967 | err = -EINVAL; |
bd353861 MF |
968 | goto out; |
969 | } else | |
970 | p += count; | |
971 | ||
972 | /* initial length does not include itself */ | |
973 | end = p + len; | |
974 | ||
3497447f | 975 | entry_type = get_unaligned((u32 *)p); |
bd353861 MF |
976 | p += 4; |
977 | ||
978 | if (entry_type == DW_EH_FRAME_CIE) { | |
a6a2f2ad | 979 | err = dwarf_parse_cie(entry, p, len, end, mod); |
bd353861 MF |
980 | if (err < 0) |
981 | goto out; | |
982 | else | |
983 | c_entries++; | |
984 | } else { | |
a6a2f2ad MF |
985 | err = dwarf_parse_fde(entry, entry_type, p, len, |
986 | end, mod); | |
bd353861 MF |
987 | if (err < 0) |
988 | goto out; | |
989 | else | |
990 | f_entries++; | |
991 | } | |
992 | ||
993 | entry = (char *)entry + len + 4; | |
994 | } | |
995 | ||
996 | printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n", | |
997 | c_entries, f_entries); | |
998 | ||
a6a2f2ad MF |
999 | return 0; |
1000 | ||
1001 | out: | |
1002 | return err; | |
1003 | } | |
1004 | ||
5a3abba7 PM |
1005 | #ifdef CONFIG_MODULES |
1006 | int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, | |
1007 | struct module *me) | |
1008 | { | |
1009 | unsigned int i, err; | |
1010 | unsigned long start, end; | |
1011 | char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; | |
1012 | ||
1013 | start = end = 0; | |
1014 | ||
1015 | for (i = 1; i < hdr->e_shnum; i++) { | |
1016 | /* Alloc bit cleared means "ignore it." */ | |
1017 | if ((sechdrs[i].sh_flags & SHF_ALLOC) | |
1018 | && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) { | |
1019 | start = sechdrs[i].sh_addr; | |
1020 | end = start + sechdrs[i].sh_size; | |
1021 | break; | |
1022 | } | |
1023 | } | |
1024 | ||
1025 | /* Did we find the .eh_frame section? */ | |
1026 | if (i != hdr->e_shnum) { | |
1027 | err = dwarf_parse_section((char *)start, (char *)end, me); | |
1028 | if (err) { | |
1029 | printk(KERN_WARNING "%s: failed to parse DWARF info\n", | |
1030 | me->name); | |
1031 | return err; | |
1032 | } | |
1033 | } | |
1034 | ||
1035 | return 0; | |
1036 | } | |
1037 | ||
a6a2f2ad | 1038 | /** |
5a3abba7 | 1039 | * module_dwarf_cleanup - remove FDE/CIEs associated with @mod |
a6a2f2ad MF |
1040 | * @mod: the module that is being unloaded |
1041 | * | |
1042 | * Remove any FDEs and CIEs from the global lists that came from | |
1043 | * @mod's .eh_frame section because @mod is being unloaded. | |
1044 | */ | |
5a3abba7 | 1045 | void module_dwarf_cleanup(struct module *mod) |
a6a2f2ad MF |
1046 | { |
1047 | struct dwarf_fde *fde; | |
1048 | struct dwarf_cie *cie; | |
1049 | unsigned long flags; | |
1050 | ||
1051 | spin_lock_irqsave(&dwarf_cie_lock, flags); | |
1052 | ||
1053 | again_cie: | |
1054 | list_for_each_entry(cie, &dwarf_cie_list, link) { | |
1055 | if (cie->mod == mod) | |
1056 | break; | |
1057 | } | |
1058 | ||
1059 | if (&cie->link != &dwarf_cie_list) { | |
1060 | list_del(&cie->link); | |
1061 | kfree(cie); | |
1062 | goto again_cie; | |
1063 | } | |
1064 | ||
1065 | spin_unlock_irqrestore(&dwarf_cie_lock, flags); | |
1066 | ||
1067 | spin_lock_irqsave(&dwarf_fde_lock, flags); | |
1068 | ||
1069 | again_fde: | |
1070 | list_for_each_entry(fde, &dwarf_fde_list, link) { | |
1071 | if (fde->mod == mod) | |
1072 | break; | |
1073 | } | |
1074 | ||
1075 | if (&fde->link != &dwarf_fde_list) { | |
1076 | list_del(&fde->link); | |
1077 | kfree(fde); | |
1078 | goto again_fde; | |
1079 | } | |
1080 | ||
1081 | spin_unlock_irqrestore(&dwarf_fde_lock, flags); | |
1082 | } | |
5a3abba7 | 1083 | #endif /* CONFIG_MODULES */ |
a6a2f2ad MF |
1084 | |
1085 | /** | |
1086 | * dwarf_unwinder_init - initialise the dwarf unwinder | |
1087 | * | |
1088 | * Build the data structures describing the .dwarf_frame section to | |
1089 | * make it easier to lookup CIE and FDE entries. Because the | |
1090 | * .eh_frame section is packed as tightly as possible it is not | |
1091 | * easy to lookup the FDE for a given PC, so we build a list of FDE | |
1092 | * and CIE entries that make it easier. | |
1093 | */ | |
1094 | static int __init dwarf_unwinder_init(void) | |
1095 | { | |
1096 | int err; | |
1097 | INIT_LIST_HEAD(&dwarf_cie_list); | |
1098 | INIT_LIST_HEAD(&dwarf_fde_list); | |
1099 | ||
1100 | dwarf_frame_cachep = kmem_cache_create("dwarf_frames", | |
8ec006c5 PM |
1101 | sizeof(struct dwarf_frame), 0, |
1102 | SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL); | |
1103 | ||
a6a2f2ad | 1104 | dwarf_reg_cachep = kmem_cache_create("dwarf_regs", |
8ec006c5 PM |
1105 | sizeof(struct dwarf_reg), 0, |
1106 | SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL); | |
a6a2f2ad MF |
1107 | |
1108 | dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ, | |
1109 | mempool_alloc_slab, | |
1110 | mempool_free_slab, | |
1111 | dwarf_frame_cachep); | |
1112 | ||
1113 | dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ, | |
1114 | mempool_alloc_slab, | |
1115 | mempool_free_slab, | |
1116 | dwarf_reg_cachep); | |
1117 | ||
1118 | err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL); | |
1119 | if (err) | |
1120 | goto out; | |
1121 | ||
bd353861 MF |
1122 | err = unwinder_register(&dwarf_unwinder); |
1123 | if (err) | |
1124 | goto out; | |
1125 | ||
97f361e2 | 1126 | return 0; |
bd353861 MF |
1127 | |
1128 | out: | |
1129 | printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err); | |
1130 | dwarf_unwinder_cleanup(); | |
97f361e2 | 1131 | return -EINVAL; |
bd353861 | 1132 | } |
97f361e2 | 1133 | early_initcall(dwarf_unwinder_init); |