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)
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 int entries; /* number of entries left to interpret */
72 int byte; /* current byte number in the instructions word */
73 };
74
75 enum regs {
76 #ifdef CONFIG_THUMB2_KERNEL
77 FP = 7,
78 #else
79 FP = 11,
80 #endif
81 SP = 13,
82 LR = 14,
83 PC = 15
84 };
85
86 extern const struct unwind_idx __start_unwind_idx[];
87 static const struct unwind_idx *__origin_unwind_idx;
88 extern const struct unwind_idx __stop_unwind_idx[];
89
90 static DEFINE_SPINLOCK(unwind_lock);
91 static LIST_HEAD(unwind_tables);
92
93 /* Convert a prel31 symbol to an absolute address */
94 #define prel31_to_addr(ptr) \
95 ({ \
96 /* sign-extend to 32 bits */ \
97 long offset = (((long)*(ptr)) << 1) >> 1; \
98 (unsigned long)(ptr) + offset; \
99 })
100
101 /*
102 * Binary search in the unwind index. The entries are
103 * guaranteed to be sorted in ascending order by the linker.
104 *
105 * start = first entry
106 * origin = first entry with positive offset (or stop if there is no such entry)
107 * stop - 1 = last entry
108 */
search_index(unsigned long addr,const struct unwind_idx * start,const struct unwind_idx * origin,const struct unwind_idx * stop)109 static const struct unwind_idx *search_index(unsigned long addr,
110 const struct unwind_idx *start,
111 const struct unwind_idx *origin,
112 const struct unwind_idx *stop)
113 {
114 unsigned long addr_prel31;
115
116 pr_debug("%s(%08lx, %p, %p, %p)\n",
117 __func__, addr, start, origin, stop);
118
119 /*
120 * only search in the section with the matching sign. This way the
121 * prel31 numbers can be compared as unsigned longs.
122 */
123 if (addr < (unsigned long)start)
124 /* negative offsets: [start; origin) */
125 stop = origin;
126 else
127 /* positive offsets: [origin; stop) */
128 start = origin;
129
130 /* prel31 for address relavive to start */
131 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;
132
133 while (start < stop - 1) {
134 const struct unwind_idx *mid = start + ((stop - start) >> 1);
135
136 /*
137 * As addr_prel31 is relative to start an offset is needed to
138 * make it relative to mid.
139 */
140 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
141 mid->addr_offset)
142 stop = mid;
143 else {
144 /* keep addr_prel31 relative to start */
145 addr_prel31 -= ((unsigned long)mid -
146 (unsigned long)start);
147 start = mid;
148 }
149 }
150
151 if (likely(start->addr_offset <= addr_prel31))
152 return start;
153 else {
154 pr_warning("unwind: Unknown symbol address %08lx\n", addr);
155 return NULL;
156 }
157 }
158
unwind_find_origin(const struct unwind_idx * start,const struct unwind_idx * stop)159 static const struct unwind_idx *unwind_find_origin(
160 const struct unwind_idx *start, const struct unwind_idx *stop)
161 {
162 pr_debug("%s(%p, %p)\n", __func__, start, stop);
163 while (start < stop) {
164 const struct unwind_idx *mid = start + ((stop - start) >> 1);
165
166 if (mid->addr_offset >= 0x40000000)
167 /* negative offset */
168 start = mid + 1;
169 else
170 /* positive offset */
171 stop = mid;
172 }
173 pr_debug("%s -> %p\n", __func__, stop);
174 return stop;
175 }
176
unwind_find_idx(unsigned long addr)177 static const struct unwind_idx *unwind_find_idx(unsigned long addr)
178 {
179 const struct unwind_idx *idx = NULL;
180 unsigned long flags;
181
182 pr_debug("%s(%08lx)\n", __func__, addr);
183
184 if (core_kernel_text(addr)) {
185 if (unlikely(!__origin_unwind_idx))
186 __origin_unwind_idx =
187 unwind_find_origin(__start_unwind_idx,
188 __stop_unwind_idx);
189
190 /* main unwind table */
191 idx = search_index(addr, __start_unwind_idx,
192 __origin_unwind_idx,
193 __stop_unwind_idx);
194 } else {
195 /* module unwind tables */
196 struct unwind_table *table;
197
198 spin_lock_irqsave(&unwind_lock, flags);
199 list_for_each_entry(table, &unwind_tables, list) {
200 if (addr >= table->begin_addr &&
201 addr < table->end_addr) {
202 idx = search_index(addr, table->start,
203 table->origin,
204 table->stop);
205 /* Move-to-front to exploit common traces */
206 list_move(&table->list, &unwind_tables);
207 break;
208 }
209 }
210 spin_unlock_irqrestore(&unwind_lock, flags);
211 }
212
213 pr_debug("%s: idx = %p\n", __func__, idx);
214 return idx;
215 }
216
unwind_get_byte(struct unwind_ctrl_block * ctrl)217 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
218 {
219 unsigned long ret;
220
221 if (ctrl->entries <= 0) {
222 pr_warning("unwind: Corrupt unwind table\n");
223 return 0;
224 }
225
226 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
227
228 if (ctrl->byte == 0) {
229 ctrl->insn++;
230 ctrl->entries--;
231 ctrl->byte = 3;
232 } else
233 ctrl->byte--;
234
235 return ret;
236 }
237
238 /*
239 * Execute the current unwind instruction.
240 */
unwind_exec_insn(struct unwind_ctrl_block * ctrl)241 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
242 {
243 unsigned long insn = unwind_get_byte(ctrl);
244
245 pr_debug("%s: insn = %08lx\n", __func__, insn);
246
247 if ((insn & 0xc0) == 0x00)
248 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
249 else if ((insn & 0xc0) == 0x40)
250 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
251 else if ((insn & 0xf0) == 0x80) {
252 unsigned long mask;
253 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
254 int load_sp, reg = 4;
255
256 insn = (insn << 8) | unwind_get_byte(ctrl);
257 mask = insn & 0x0fff;
258 if (mask == 0) {
259 pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
260 insn);
261 return -URC_FAILURE;
262 }
263
264 /* pop R4-R15 according to mask */
265 load_sp = mask & (1 << (13 - 4));
266 while (mask) {
267 if (mask & 1)
268 ctrl->vrs[reg] = *vsp++;
269 mask >>= 1;
270 reg++;
271 }
272 if (!load_sp)
273 ctrl->vrs[SP] = (unsigned long)vsp;
274 } else if ((insn & 0xf0) == 0x90 &&
275 (insn & 0x0d) != 0x0d)
276 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
277 else if ((insn & 0xf0) == 0xa0) {
278 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
279 int reg;
280
281 /* pop R4-R[4+bbb] */
282 for (reg = 4; reg <= 4 + (insn & 7); reg++)
283 ctrl->vrs[reg] = *vsp++;
284 if (insn & 0x80)
285 ctrl->vrs[14] = *vsp++;
286 ctrl->vrs[SP] = (unsigned long)vsp;
287 } else if (insn == 0xb0) {
288 if (ctrl->vrs[PC] == 0)
289 ctrl->vrs[PC] = ctrl->vrs[LR];
290 /* no further processing */
291 ctrl->entries = 0;
292 } else if (insn == 0xb1) {
293 unsigned long mask = unwind_get_byte(ctrl);
294 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
295 int reg = 0;
296
297 if (mask == 0 || mask & 0xf0) {
298 pr_warning("unwind: Spare encoding %04lx\n",
299 (insn << 8) | mask);
300 return -URC_FAILURE;
301 }
302
303 /* pop R0-R3 according to mask */
304 while (mask) {
305 if (mask & 1)
306 ctrl->vrs[reg] = *vsp++;
307 mask >>= 1;
308 reg++;
309 }
310 ctrl->vrs[SP] = (unsigned long)vsp;
311 } else if (insn == 0xb2) {
312 unsigned long uleb128 = unwind_get_byte(ctrl);
313
314 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
315 } else {
316 pr_warning("unwind: Unhandled instruction %02lx\n", insn);
317 return -URC_FAILURE;
318 }
319
320 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
321 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
322
323 return URC_OK;
324 }
325
326 /*
327 * Unwind a single frame starting with *sp for the symbol at *pc. It
328 * updates the *pc and *sp with the new values.
329 */
unwind_frame(struct stackframe * frame)330 int unwind_frame(struct stackframe *frame)
331 {
332 unsigned long high, low;
333 const struct unwind_idx *idx;
334 struct unwind_ctrl_block ctrl;
335
336 /* only go to a higher address on the stack */
337 low = frame->sp;
338 high = ALIGN(low, THREAD_SIZE);
339
340 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
341 frame->pc, frame->lr, frame->sp);
342
343 if (!kernel_text_address(frame->pc))
344 return -URC_FAILURE;
345
346 idx = unwind_find_idx(frame->pc);
347 if (!idx) {
348 pr_warning("unwind: Index not found %08lx\n", frame->pc);
349 return -URC_FAILURE;
350 }
351
352 ctrl.vrs[FP] = frame->fp;
353 ctrl.vrs[SP] = frame->sp;
354 ctrl.vrs[LR] = frame->lr;
355 ctrl.vrs[PC] = 0;
356
357 if (idx->insn == 1)
358 /* can't unwind */
359 return -URC_FAILURE;
360 else if ((idx->insn & 0x80000000) == 0)
361 /* prel31 to the unwind table */
362 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
363 else if ((idx->insn & 0xff000000) == 0x80000000)
364 /* only personality routine 0 supported in the index */
365 ctrl.insn = &idx->insn;
366 else {
367 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n",
368 idx->insn, idx);
369 return -URC_FAILURE;
370 }
371
372 /* check the personality routine */
373 if ((*ctrl.insn & 0xff000000) == 0x80000000) {
374 ctrl.byte = 2;
375 ctrl.entries = 1;
376 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
377 ctrl.byte = 1;
378 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
379 } else {
380 pr_warning("unwind: Unsupported personality routine %08lx at %p\n",
381 *ctrl.insn, ctrl.insn);
382 return -URC_FAILURE;
383 }
384
385 while (ctrl.entries > 0) {
386 int urc = unwind_exec_insn(&ctrl);
387 if (urc < 0)
388 return urc;
389 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
390 return -URC_FAILURE;
391 }
392
393 if (ctrl.vrs[PC] == 0)
394 ctrl.vrs[PC] = ctrl.vrs[LR];
395
396 /* check for infinite loop */
397 if (frame->pc == ctrl.vrs[PC])
398 return -URC_FAILURE;
399
400 frame->fp = ctrl.vrs[FP];
401 frame->sp = ctrl.vrs[SP];
402 frame->lr = ctrl.vrs[LR];
403 frame->pc = ctrl.vrs[PC];
404
405 return URC_OK;
406 }
407
unwind_backtrace(struct pt_regs * regs,struct task_struct * tsk)408 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
409 {
410 struct stackframe frame;
411 register unsigned long current_sp asm ("sp");
412
413 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
414
415 if (!tsk)
416 tsk = current;
417
418 if (regs) {
419 frame.fp = regs->ARM_fp;
420 frame.sp = regs->ARM_sp;
421 frame.lr = regs->ARM_lr;
422 /* PC might be corrupted, use LR in that case. */
423 frame.pc = kernel_text_address(regs->ARM_pc)
424 ? regs->ARM_pc : regs->ARM_lr;
425 } else if (tsk == current) {
426 frame.fp = (unsigned long)__builtin_frame_address(0);
427 frame.sp = current_sp;
428 frame.lr = (unsigned long)__builtin_return_address(0);
429 frame.pc = (unsigned long)unwind_backtrace;
430 } else {
431 /* task blocked in __switch_to */
432 frame.fp = thread_saved_fp(tsk);
433 frame.sp = thread_saved_sp(tsk);
434 /*
435 * The function calling __switch_to cannot be a leaf function
436 * so LR is recovered from the stack.
437 */
438 frame.lr = 0;
439 frame.pc = thread_saved_pc(tsk);
440 }
441
442 while (1) {
443 int urc;
444 unsigned long where = frame.pc;
445
446 urc = unwind_frame(&frame);
447 if (urc < 0)
448 break;
449 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
450 }
451 }
452
unwind_table_add(unsigned long start,unsigned long size,unsigned long text_addr,unsigned long text_size)453 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
454 unsigned long text_addr,
455 unsigned long text_size)
456 {
457 unsigned long flags;
458 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
459
460 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
461 text_addr, text_size);
462
463 if (!tab)
464 return tab;
465
466 tab->start = (const struct unwind_idx *)start;
467 tab->stop = (const struct unwind_idx *)(start + size);
468 tab->origin = unwind_find_origin(tab->start, tab->stop);
469 tab->begin_addr = text_addr;
470 tab->end_addr = text_addr + text_size;
471
472 spin_lock_irqsave(&unwind_lock, flags);
473 list_add_tail(&tab->list, &unwind_tables);
474 spin_unlock_irqrestore(&unwind_lock, flags);
475
476 return tab;
477 }
478
unwind_table_del(struct unwind_table * tab)479 void unwind_table_del(struct unwind_table *tab)
480 {
481 unsigned long flags;
482
483 if (!tab)
484 return;
485
486 spin_lock_irqsave(&unwind_lock, flags);
487 list_del(&tab->list);
488 spin_unlock_irqrestore(&unwind_lock, flags);
489
490 kfree(tab);
491 }
492