1 /*
2 * arch/arm/kernel/unwind.c
3 *
4 * Copyright (C) 2008 ARM Limited
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 *
19 *
20 * Stack unwinding support for ARM
21 *
22 * An ARM EABI version of gcc is required to generate the unwind
23 * tables. For information about the structure of the unwind tables,
24 * see "Exception Handling ABI for the ARM Architecture" at:
25 *
26 * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
27 */
28
29 #ifndef __CHECKER__
30 #if !defined (__ARM_EABI__)
31 #warning Your compiler does not have EABI support.
32 #warning ARM unwind is known to compile only with EABI compilers.
33 #warning Change compiler or disable ARM_UNWIND option.
34 #elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2) && !defined(__clang__)
35 #warning Your compiler is too buggy; it is known to not compile ARM unwind support.
36 #warning Change compiler or disable ARM_UNWIND option.
37 #endif
38 #endif /* __CHECKER__ */
39
40 #include <linux/kernel.h>
41 #include <linux/init.h>
42 #include <linux/export.h>
43 #include <linux/sched.h>
44 #include <linux/slab.h>
45 #include <linux/spinlock.h>
46 #include <linux/list.h>
47
48 #include <asm/stacktrace.h>
49 #include <asm/traps.h>
50 #include <asm/unwind.h>
51
52 /* Dummy functions to avoid linker complaints */
__aeabi_unwind_cpp_pr0(void)53 void __aeabi_unwind_cpp_pr0(void)
54 {
55 };
56 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
57
__aeabi_unwind_cpp_pr1(void)58 void __aeabi_unwind_cpp_pr1(void)
59 {
60 };
61 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
62
__aeabi_unwind_cpp_pr2(void)63 void __aeabi_unwind_cpp_pr2(void)
64 {
65 };
66 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
67
68 struct unwind_ctrl_block {
69 unsigned long vrs[16]; /* virtual register set */
70 const unsigned long *insn; /* pointer to the current instructions word */
71 unsigned long sp_high; /* highest value of sp allowed */
72 /*
73 * 1 : check for stack overflow for each register pop.
74 * 0 : save overhead if there is plenty of stack remaining.
75 */
76 int check_each_pop;
77 int entries; /* number of entries left to interpret */
78 int byte; /* current byte number in the instructions word */
79 };
80
81 enum regs {
82 #ifdef CONFIG_THUMB2_KERNEL
83 FP = 7,
84 #else
85 FP = 11,
86 #endif
87 SP = 13,
88 LR = 14,
89 PC = 15
90 };
91
92 extern const struct unwind_idx __start_unwind_idx[];
93 static const struct unwind_idx *__origin_unwind_idx;
94 extern const struct unwind_idx __stop_unwind_idx[];
95
96 static DEFINE_SPINLOCK(unwind_lock);
97 static LIST_HEAD(unwind_tables);
98
99 /* Convert a prel31 symbol to an absolute address */
100 #define prel31_to_addr(ptr) \
101 ({ \
102 /* sign-extend to 32 bits */ \
103 long offset = (((long)*(ptr)) << 1) >> 1; \
104 (unsigned long)(ptr) + offset; \
105 })
106
107 /*
108 * Binary search in the unwind index. The entries are
109 * guaranteed to be sorted in ascending order by the linker.
110 *
111 * start = first entry
112 * origin = first entry with positive offset (or stop if there is no such entry)
113 * stop - 1 = last entry
114 */
search_index(unsigned long addr,const struct unwind_idx * start,const struct unwind_idx * origin,const struct unwind_idx * stop)115 static const struct unwind_idx *search_index(unsigned long addr,
116 const struct unwind_idx *start,
117 const struct unwind_idx *origin,
118 const struct unwind_idx *stop)
119 {
120 unsigned long addr_prel31;
121
122 pr_debug("%s(%08lx, %p, %p, %p)\n",
123 __func__, addr, start, origin, stop);
124
125 /*
126 * only search in the section with the matching sign. This way the
127 * prel31 numbers can be compared as unsigned longs.
128 */
129 if (addr < (unsigned long)start)
130 /* negative offsets: [start; origin) */
131 stop = origin;
132 else
133 /* positive offsets: [origin; stop) */
134 start = origin;
135
136 /* prel31 for address relavive to start */
137 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;
138
139 while (start < stop - 1) {
140 const struct unwind_idx *mid = start + ((stop - start) >> 1);
141
142 /*
143 * As addr_prel31 is relative to start an offset is needed to
144 * make it relative to mid.
145 */
146 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
147 mid->addr_offset)
148 stop = mid;
149 else {
150 /* keep addr_prel31 relative to start */
151 addr_prel31 -= ((unsigned long)mid -
152 (unsigned long)start);
153 start = mid;
154 }
155 }
156
157 if (likely(start->addr_offset <= addr_prel31))
158 return start;
159 else {
160 pr_warn("unwind: Unknown symbol address %08lx\n", addr);
161 return NULL;
162 }
163 }
164
unwind_find_origin(const struct unwind_idx * start,const struct unwind_idx * stop)165 static const struct unwind_idx *unwind_find_origin(
166 const struct unwind_idx *start, const struct unwind_idx *stop)
167 {
168 pr_debug("%s(%p, %p)\n", __func__, start, stop);
169 while (start < stop) {
170 const struct unwind_idx *mid = start + ((stop - start) >> 1);
171
172 if (mid->addr_offset >= 0x40000000)
173 /* negative offset */
174 start = mid + 1;
175 else
176 /* positive offset */
177 stop = mid;
178 }
179 pr_debug("%s -> %p\n", __func__, stop);
180 return stop;
181 }
182
unwind_find_idx(unsigned long addr)183 static const struct unwind_idx *unwind_find_idx(unsigned long addr)
184 {
185 const struct unwind_idx *idx = NULL;
186 unsigned long flags;
187
188 pr_debug("%s(%08lx)\n", __func__, addr);
189
190 if (core_kernel_text(addr)) {
191 if (unlikely(!__origin_unwind_idx))
192 __origin_unwind_idx =
193 unwind_find_origin(__start_unwind_idx,
194 __stop_unwind_idx);
195
196 /* main unwind table */
197 idx = search_index(addr, __start_unwind_idx,
198 __origin_unwind_idx,
199 __stop_unwind_idx);
200 } else {
201 /* module unwind tables */
202 struct unwind_table *table;
203
204 spin_lock_irqsave(&unwind_lock, flags);
205 list_for_each_entry(table, &unwind_tables, list) {
206 if (addr >= table->begin_addr &&
207 addr < table->end_addr) {
208 idx = search_index(addr, table->start,
209 table->origin,
210 table->stop);
211 /* Move-to-front to exploit common traces */
212 list_move(&table->list, &unwind_tables);
213 break;
214 }
215 }
216 spin_unlock_irqrestore(&unwind_lock, flags);
217 }
218
219 pr_debug("%s: idx = %p\n", __func__, idx);
220 return idx;
221 }
222
unwind_get_byte(struct unwind_ctrl_block * ctrl)223 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
224 {
225 unsigned long ret;
226
227 if (ctrl->entries <= 0) {
228 pr_warn("unwind: Corrupt unwind table\n");
229 return 0;
230 }
231
232 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
233
234 if (ctrl->byte == 0) {
235 ctrl->insn++;
236 ctrl->entries--;
237 ctrl->byte = 3;
238 } else
239 ctrl->byte--;
240
241 return ret;
242 }
243
244 /* Before poping a register check whether it is feasible or not */
unwind_pop_register(struct unwind_ctrl_block * ctrl,unsigned long ** vsp,unsigned int reg)245 static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
246 unsigned long **vsp, unsigned int reg)
247 {
248 if (unlikely(ctrl->check_each_pop))
249 if (*vsp >= (unsigned long *)ctrl->sp_high)
250 return -URC_FAILURE;
251
252 ctrl->vrs[reg] = *(*vsp)++;
253 return URC_OK;
254 }
255
256 /* Helper functions to execute the instructions */
unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block * ctrl,unsigned long mask)257 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl,
258 unsigned long mask)
259 {
260 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
261 int load_sp, reg = 4;
262
263 load_sp = mask & (1 << (13 - 4));
264 while (mask) {
265 if (mask & 1)
266 if (unwind_pop_register(ctrl, &vsp, reg))
267 return -URC_FAILURE;
268 mask >>= 1;
269 reg++;
270 }
271 if (!load_sp)
272 ctrl->vrs[SP] = (unsigned long)vsp;
273
274 return URC_OK;
275 }
276
unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block * ctrl,unsigned long insn)277 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl,
278 unsigned long insn)
279 {
280 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
281 int reg;
282
283 /* pop R4-R[4+bbb] */
284 for (reg = 4; reg <= 4 + (insn & 7); reg++)
285 if (unwind_pop_register(ctrl, &vsp, reg))
286 return -URC_FAILURE;
287
288 if (insn & 0x8)
289 if (unwind_pop_register(ctrl, &vsp, 14))
290 return -URC_FAILURE;
291
292 ctrl->vrs[SP] = (unsigned long)vsp;
293
294 return URC_OK;
295 }
296
unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block * ctrl,unsigned long mask)297 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
298 unsigned long mask)
299 {
300 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
301 int reg = 0;
302
303 /* pop R0-R3 according to mask */
304 while (mask) {
305 if (mask & 1)
306 if (unwind_pop_register(ctrl, &vsp, reg))
307 return -URC_FAILURE;
308 mask >>= 1;
309 reg++;
310 }
311 ctrl->vrs[SP] = (unsigned long)vsp;
312
313 return URC_OK;
314 }
315
316 /*
317 * Execute the current unwind instruction.
318 */
unwind_exec_insn(struct unwind_ctrl_block * ctrl)319 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
320 {
321 unsigned long insn = unwind_get_byte(ctrl);
322 int ret = URC_OK;
323
324 pr_debug("%s: insn = %08lx\n", __func__, insn);
325
326 if ((insn & 0xc0) == 0x00)
327 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
328 else if ((insn & 0xc0) == 0x40)
329 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
330 else if ((insn & 0xf0) == 0x80) {
331 unsigned long mask;
332
333 insn = (insn << 8) | unwind_get_byte(ctrl);
334 mask = insn & 0x0fff;
335 if (mask == 0) {
336 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n",
337 insn);
338 return -URC_FAILURE;
339 }
340
341 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask);
342 if (ret)
343 goto error;
344 } else if ((insn & 0xf0) == 0x90 &&
345 (insn & 0x0d) != 0x0d)
346 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
347 else if ((insn & 0xf0) == 0xa0) {
348 ret = unwind_exec_pop_r4_to_rN(ctrl, insn);
349 if (ret)
350 goto error;
351 } else if (insn == 0xb0) {
352 if (ctrl->vrs[PC] == 0)
353 ctrl->vrs[PC] = ctrl->vrs[LR];
354 /* no further processing */
355 ctrl->entries = 0;
356 } else if (insn == 0xb1) {
357 unsigned long mask = unwind_get_byte(ctrl);
358
359 if (mask == 0 || mask & 0xf0) {
360 pr_warn("unwind: Spare encoding %04lx\n",
361 (insn << 8) | mask);
362 return -URC_FAILURE;
363 }
364
365 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask);
366 if (ret)
367 goto error;
368 } else if (insn == 0xb2) {
369 unsigned long uleb128 = unwind_get_byte(ctrl);
370
371 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
372 } else {
373 pr_warn("unwind: Unhandled instruction %02lx\n", insn);
374 return -URC_FAILURE;
375 }
376
377 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
378 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
379
380 error:
381 return ret;
382 }
383
384 /*
385 * Unwind a single frame starting with *sp for the symbol at *pc. It
386 * updates the *pc and *sp with the new values.
387 */
unwind_frame(struct stackframe * frame)388 int unwind_frame(struct stackframe *frame)
389 {
390 unsigned long low;
391 const struct unwind_idx *idx;
392 struct unwind_ctrl_block ctrl;
393
394 /* store the highest address on the stack to avoid crossing it*/
395 low = frame->sp;
396 ctrl.sp_high = ALIGN(low, THREAD_SIZE);
397
398 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
399 frame->pc, frame->lr, frame->sp);
400
401 if (!kernel_text_address(frame->pc))
402 return -URC_FAILURE;
403
404 idx = unwind_find_idx(frame->pc);
405 if (!idx) {
406 pr_warn("unwind: Index not found %08lx\n", frame->pc);
407 return -URC_FAILURE;
408 }
409
410 ctrl.vrs[FP] = frame->fp;
411 ctrl.vrs[SP] = frame->sp;
412 ctrl.vrs[LR] = frame->lr;
413 ctrl.vrs[PC] = 0;
414
415 if (idx->insn == 1)
416 /* can't unwind */
417 return -URC_FAILURE;
418 else if ((idx->insn & 0x80000000) == 0)
419 /* prel31 to the unwind table */
420 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
421 else if ((idx->insn & 0xff000000) == 0x80000000)
422 /* only personality routine 0 supported in the index */
423 ctrl.insn = &idx->insn;
424 else {
425 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n",
426 idx->insn, idx);
427 return -URC_FAILURE;
428 }
429
430 /* check the personality routine */
431 if ((*ctrl.insn & 0xff000000) == 0x80000000) {
432 ctrl.byte = 2;
433 ctrl.entries = 1;
434 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
435 ctrl.byte = 1;
436 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
437 } else {
438 pr_warn("unwind: Unsupported personality routine %08lx at %p\n",
439 *ctrl.insn, ctrl.insn);
440 return -URC_FAILURE;
441 }
442
443 ctrl.check_each_pop = 0;
444
445 while (ctrl.entries > 0) {
446 int urc;
447 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs))
448 ctrl.check_each_pop = 1;
449 urc = unwind_exec_insn(&ctrl);
450 if (urc < 0)
451 return urc;
452 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high)
453 return -URC_FAILURE;
454 }
455
456 if (ctrl.vrs[PC] == 0)
457 ctrl.vrs[PC] = ctrl.vrs[LR];
458
459 /* check for infinite loop */
460 if (frame->pc == ctrl.vrs[PC])
461 return -URC_FAILURE;
462
463 frame->fp = ctrl.vrs[FP];
464 frame->sp = ctrl.vrs[SP];
465 frame->lr = ctrl.vrs[LR];
466 frame->pc = ctrl.vrs[PC];
467
468 return URC_OK;
469 }
470
unwind_backtrace(struct pt_regs * regs,struct task_struct * tsk)471 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
472 {
473 struct stackframe frame;
474
475 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
476
477 if (!tsk)
478 tsk = current;
479
480 if (regs) {
481 arm_get_current_stackframe(regs, &frame);
482 /* PC might be corrupted, use LR in that case. */
483 if (!kernel_text_address(regs->ARM_pc))
484 frame.pc = regs->ARM_lr;
485 } else if (tsk == current) {
486 frame.fp = (unsigned long)__builtin_frame_address(0);
487 frame.sp = current_stack_pointer;
488 frame.lr = (unsigned long)__builtin_return_address(0);
489 frame.pc = (unsigned long)unwind_backtrace;
490 } else {
491 /* task blocked in __switch_to */
492 frame.fp = thread_saved_fp(tsk);
493 frame.sp = thread_saved_sp(tsk);
494 /*
495 * The function calling __switch_to cannot be a leaf function
496 * so LR is recovered from the stack.
497 */
498 frame.lr = 0;
499 frame.pc = thread_saved_pc(tsk);
500 }
501
502 while (1) {
503 int urc;
504 unsigned long where = frame.pc;
505
506 urc = unwind_frame(&frame);
507 if (urc < 0)
508 break;
509 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
510 }
511 }
512
unwind_table_add(unsigned long start,unsigned long size,unsigned long text_addr,unsigned long text_size)513 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
514 unsigned long text_addr,
515 unsigned long text_size)
516 {
517 unsigned long flags;
518 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
519
520 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
521 text_addr, text_size);
522
523 if (!tab)
524 return tab;
525
526 tab->start = (const struct unwind_idx *)start;
527 tab->stop = (const struct unwind_idx *)(start + size);
528 tab->origin = unwind_find_origin(tab->start, tab->stop);
529 tab->begin_addr = text_addr;
530 tab->end_addr = text_addr + text_size;
531
532 spin_lock_irqsave(&unwind_lock, flags);
533 list_add_tail(&tab->list, &unwind_tables);
534 spin_unlock_irqrestore(&unwind_lock, flags);
535
536 return tab;
537 }
538
unwind_table_del(struct unwind_table * tab)539 void unwind_table_del(struct unwind_table *tab)
540 {
541 unsigned long flags;
542
543 if (!tab)
544 return;
545
546 spin_lock_irqsave(&unwind_lock, flags);
547 list_del(&tab->list);
548 spin_unlock_irqrestore(&unwind_lock, flags);
549
550 kfree(tab);
551 }
552
