1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * arch/arm/kernel/unwind.c
4 *
5 * Copyright (C) 2008 ARM Limited
6 *
7 * Stack unwinding support for ARM
8 *
9 * An ARM EABI version of gcc is required to generate the unwind
10 * tables. For information about the structure of the unwind tables,
11 * see "Exception Handling ABI for the ARM Architecture" at:
12 *
13 * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
14 */
15
16 #ifndef __CHECKER__
17 #if !defined (__ARM_EABI__)
18 #warning Your compiler does not have EABI support.
19 #warning ARM unwind is known to compile only with EABI compilers.
20 #warning Change compiler or disable ARM_UNWIND option.
21 #elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2) && !defined(__clang__)
22 #warning Your compiler is too buggy; it is known to not compile ARM unwind support.
23 #warning Change compiler or disable ARM_UNWIND option.
24 #endif
25 #endif /* __CHECKER__ */
26
27 #include <linux/kernel.h>
28 #include <linux/init.h>
29 #include <linux/export.h>
30 #include <linux/sched.h>
31 #include <linux/slab.h>
32 #include <linux/spinlock.h>
33 #include <linux/list.h>
34
35 #include <asm/stacktrace.h>
36 #include <asm/traps.h>
37 #include <asm/unwind.h>
38
39 /* Dummy functions to avoid linker complaints */
__aeabi_unwind_cpp_pr0(void)40 void __aeabi_unwind_cpp_pr0(void)
41 {
42 };
43 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
44
__aeabi_unwind_cpp_pr1(void)45 void __aeabi_unwind_cpp_pr1(void)
46 {
47 };
48 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
49
__aeabi_unwind_cpp_pr2(void)50 void __aeabi_unwind_cpp_pr2(void)
51 {
52 };
53 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
54
55 struct unwind_ctrl_block {
56 unsigned long vrs[16]; /* virtual register set */
57 const unsigned long *insn; /* pointer to the current instructions word */
58 unsigned long sp_high; /* highest value of sp allowed */
59 /*
60 * 1 : check for stack overflow for each register pop.
61 * 0 : save overhead if there is plenty of stack remaining.
62 */
63 int check_each_pop;
64 int entries; /* number of entries left to interpret */
65 int byte; /* current byte number in the instructions word */
66 };
67
68 enum regs {
69 #ifdef CONFIG_THUMB2_KERNEL
70 FP = 7,
71 #else
72 FP = 11,
73 #endif
74 SP = 13,
75 LR = 14,
76 PC = 15
77 };
78
79 extern const struct unwind_idx __start_unwind_idx[];
80 static const struct unwind_idx *__origin_unwind_idx;
81 extern const struct unwind_idx __stop_unwind_idx[];
82
83 static DEFINE_RAW_SPINLOCK(unwind_lock);
84 static LIST_HEAD(unwind_tables);
85
86 /* Convert a prel31 symbol to an absolute address */
87 #define prel31_to_addr(ptr) \
88 ({ \
89 /* sign-extend to 32 bits */ \
90 long offset = (((long)*(ptr)) << 1) >> 1; \
91 (unsigned long)(ptr) + offset; \
92 })
93
94 /*
95 * Binary search in the unwind index. The entries are
96 * guaranteed to be sorted in ascending order by the linker.
97 *
98 * start = first entry
99 * origin = first entry with positive offset (or stop if there is no such entry)
100 * stop - 1 = last entry
101 */
search_index(unsigned long addr,const struct unwind_idx * start,const struct unwind_idx * origin,const struct unwind_idx * stop)102 static const struct unwind_idx *search_index(unsigned long addr,
103 const struct unwind_idx *start,
104 const struct unwind_idx *origin,
105 const struct unwind_idx *stop)
106 {
107 unsigned long addr_prel31;
108
109 pr_debug("%s(%08lx, %p, %p, %p)\n",
110 __func__, addr, start, origin, stop);
111
112 /*
113 * only search in the section with the matching sign. This way the
114 * prel31 numbers can be compared as unsigned longs.
115 */
116 if (addr < (unsigned long)start)
117 /* negative offsets: [start; origin) */
118 stop = origin;
119 else
120 /* positive offsets: [origin; stop) */
121 start = origin;
122
123 /* prel31 for address relavive to start */
124 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;
125
126 while (start < stop - 1) {
127 const struct unwind_idx *mid = start + ((stop - start) >> 1);
128
129 /*
130 * As addr_prel31 is relative to start an offset is needed to
131 * make it relative to mid.
132 */
133 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
134 mid->addr_offset)
135 stop = mid;
136 else {
137 /* keep addr_prel31 relative to start */
138 addr_prel31 -= ((unsigned long)mid -
139 (unsigned long)start);
140 start = mid;
141 }
142 }
143
144 if (likely(start->addr_offset <= addr_prel31))
145 return start;
146 else {
147 pr_warn("unwind: Unknown symbol address %08lx\n", addr);
148 return NULL;
149 }
150 }
151
unwind_find_origin(const struct unwind_idx * start,const struct unwind_idx * stop)152 static const struct unwind_idx *unwind_find_origin(
153 const struct unwind_idx *start, const struct unwind_idx *stop)
154 {
155 pr_debug("%s(%p, %p)\n", __func__, start, stop);
156 while (start < stop) {
157 const struct unwind_idx *mid = start + ((stop - start) >> 1);
158
159 if (mid->addr_offset >= 0x40000000)
160 /* negative offset */
161 start = mid + 1;
162 else
163 /* positive offset */
164 stop = mid;
165 }
166 pr_debug("%s -> %p\n", __func__, stop);
167 return stop;
168 }
169
unwind_find_idx(unsigned long addr)170 static const struct unwind_idx *unwind_find_idx(unsigned long addr)
171 {
172 const struct unwind_idx *idx = NULL;
173 unsigned long flags;
174
175 pr_debug("%s(%08lx)\n", __func__, addr);
176
177 if (core_kernel_text(addr)) {
178 if (unlikely(!__origin_unwind_idx))
179 __origin_unwind_idx =
180 unwind_find_origin(__start_unwind_idx,
181 __stop_unwind_idx);
182
183 /* main unwind table */
184 idx = search_index(addr, __start_unwind_idx,
185 __origin_unwind_idx,
186 __stop_unwind_idx);
187 } else {
188 /* module unwind tables */
189 struct unwind_table *table;
190
191 raw_spin_lock_irqsave(&unwind_lock, flags);
192 list_for_each_entry(table, &unwind_tables, list) {
193 if (addr >= table->begin_addr &&
194 addr < table->end_addr) {
195 idx = search_index(addr, table->start,
196 table->origin,
197 table->stop);
198 /* Move-to-front to exploit common traces */
199 list_move(&table->list, &unwind_tables);
200 break;
201 }
202 }
203 raw_spin_unlock_irqrestore(&unwind_lock, flags);
204 }
205
206 pr_debug("%s: idx = %p\n", __func__, idx);
207 return idx;
208 }
209
unwind_get_byte(struct unwind_ctrl_block * ctrl)210 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
211 {
212 unsigned long ret;
213
214 if (ctrl->entries <= 0) {
215 pr_warn("unwind: Corrupt unwind table\n");
216 return 0;
217 }
218
219 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
220
221 if (ctrl->byte == 0) {
222 ctrl->insn++;
223 ctrl->entries--;
224 ctrl->byte = 3;
225 } else
226 ctrl->byte--;
227
228 return ret;
229 }
230
231 /* 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)232 static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
233 unsigned long **vsp, unsigned int reg)
234 {
235 if (unlikely(ctrl->check_each_pop))
236 if (*vsp >= (unsigned long *)ctrl->sp_high)
237 return -URC_FAILURE;
238
239 /* Use READ_ONCE_NOCHECK here to avoid this memory access
240 * from being tracked by KASAN.
241 */
242 ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp));
243 (*vsp)++;
244 return URC_OK;
245 }
246
247 /* Helper functions to execute the instructions */
unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block * ctrl,unsigned long mask)248 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl,
249 unsigned long mask)
250 {
251 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
252 int load_sp, reg = 4;
253
254 load_sp = mask & (1 << (13 - 4));
255 while (mask) {
256 if (mask & 1)
257 if (unwind_pop_register(ctrl, &vsp, reg))
258 return -URC_FAILURE;
259 mask >>= 1;
260 reg++;
261 }
262 if (!load_sp)
263 ctrl->vrs[SP] = (unsigned long)vsp;
264
265 return URC_OK;
266 }
267
unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block * ctrl,unsigned long insn)268 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl,
269 unsigned long insn)
270 {
271 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
272 int reg;
273
274 /* pop R4-R[4+bbb] */
275 for (reg = 4; reg <= 4 + (insn & 7); reg++)
276 if (unwind_pop_register(ctrl, &vsp, reg))
277 return -URC_FAILURE;
278
279 if (insn & 0x8)
280 if (unwind_pop_register(ctrl, &vsp, 14))
281 return -URC_FAILURE;
282
283 ctrl->vrs[SP] = (unsigned long)vsp;
284
285 return URC_OK;
286 }
287
unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block * ctrl,unsigned long mask)288 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
289 unsigned long mask)
290 {
291 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
292 int reg = 0;
293
294 /* pop R0-R3 according to mask */
295 while (mask) {
296 if (mask & 1)
297 if (unwind_pop_register(ctrl, &vsp, reg))
298 return -URC_FAILURE;
299 mask >>= 1;
300 reg++;
301 }
302 ctrl->vrs[SP] = (unsigned long)vsp;
303
304 return URC_OK;
305 }
306
307 /*
308 * Execute the current unwind instruction.
309 */
unwind_exec_insn(struct unwind_ctrl_block * ctrl)310 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
311 {
312 unsigned long insn = unwind_get_byte(ctrl);
313 int ret = URC_OK;
314
315 pr_debug("%s: insn = %08lx\n", __func__, insn);
316
317 if ((insn & 0xc0) == 0x00)
318 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
319 else if ((insn & 0xc0) == 0x40)
320 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
321 else if ((insn & 0xf0) == 0x80) {
322 unsigned long mask;
323
324 insn = (insn << 8) | unwind_get_byte(ctrl);
325 mask = insn & 0x0fff;
326 if (mask == 0) {
327 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n",
328 insn);
329 return -URC_FAILURE;
330 }
331
332 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask);
333 if (ret)
334 goto error;
335 } else if ((insn & 0xf0) == 0x90 &&
336 (insn & 0x0d) != 0x0d)
337 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
338 else if ((insn & 0xf0) == 0xa0) {
339 ret = unwind_exec_pop_r4_to_rN(ctrl, insn);
340 if (ret)
341 goto error;
342 } else if (insn == 0xb0) {
343 if (ctrl->vrs[PC] == 0)
344 ctrl->vrs[PC] = ctrl->vrs[LR];
345 /* no further processing */
346 ctrl->entries = 0;
347 } else if (insn == 0xb1) {
348 unsigned long mask = unwind_get_byte(ctrl);
349
350 if (mask == 0 || mask & 0xf0) {
351 pr_warn("unwind: Spare encoding %04lx\n",
352 (insn << 8) | mask);
353 return -URC_FAILURE;
354 }
355
356 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask);
357 if (ret)
358 goto error;
359 } else if (insn == 0xb2) {
360 unsigned long uleb128 = unwind_get_byte(ctrl);
361
362 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
363 } else {
364 pr_warn("unwind: Unhandled instruction %02lx\n", insn);
365 return -URC_FAILURE;
366 }
367
368 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
369 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
370
371 error:
372 return ret;
373 }
374
375 /*
376 * Unwind a single frame starting with *sp for the symbol at *pc. It
377 * updates the *pc and *sp with the new values.
378 */
unwind_frame(struct stackframe * frame)379 int unwind_frame(struct stackframe *frame)
380 {
381 unsigned long low;
382 const struct unwind_idx *idx;
383 struct unwind_ctrl_block ctrl;
384
385 /* store the highest address on the stack to avoid crossing it*/
386 low = frame->sp;
387 ctrl.sp_high = ALIGN(low, THREAD_SIZE);
388
389 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
390 frame->pc, frame->lr, frame->sp);
391
392 if (!kernel_text_address(frame->pc))
393 return -URC_FAILURE;
394
395 idx = unwind_find_idx(frame->pc);
396 if (!idx) {
397 pr_warn("unwind: Index not found %08lx\n", frame->pc);
398 return -URC_FAILURE;
399 }
400
401 ctrl.vrs[FP] = frame->fp;
402 ctrl.vrs[SP] = frame->sp;
403 ctrl.vrs[LR] = frame->lr;
404 ctrl.vrs[PC] = 0;
405
406 if (idx->insn == 1)
407 /* can't unwind */
408 return -URC_FAILURE;
409 else if ((idx->insn & 0x80000000) == 0)
410 /* prel31 to the unwind table */
411 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
412 else if ((idx->insn & 0xff000000) == 0x80000000)
413 /* only personality routine 0 supported in the index */
414 ctrl.insn = &idx->insn;
415 else {
416 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n",
417 idx->insn, idx);
418 return -URC_FAILURE;
419 }
420
421 /* check the personality routine */
422 if ((*ctrl.insn & 0xff000000) == 0x80000000) {
423 ctrl.byte = 2;
424 ctrl.entries = 1;
425 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
426 ctrl.byte = 1;
427 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
428 } else {
429 pr_warn("unwind: Unsupported personality routine %08lx at %p\n",
430 *ctrl.insn, ctrl.insn);
431 return -URC_FAILURE;
432 }
433
434 ctrl.check_each_pop = 0;
435
436 while (ctrl.entries > 0) {
437 int urc;
438 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs))
439 ctrl.check_each_pop = 1;
440 urc = unwind_exec_insn(&ctrl);
441 if (urc < 0)
442 return urc;
443 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high)
444 return -URC_FAILURE;
445 }
446
447 if (ctrl.vrs[PC] == 0)
448 ctrl.vrs[PC] = ctrl.vrs[LR];
449
450 /* check for infinite loop */
451 if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP])
452 return -URC_FAILURE;
453
454 frame->fp = ctrl.vrs[FP];
455 frame->sp = ctrl.vrs[SP];
456 frame->lr = ctrl.vrs[LR];
457 frame->pc = ctrl.vrs[PC];
458
459 return URC_OK;
460 }
461
unwind_backtrace(struct pt_regs * regs,struct task_struct * tsk,const char * loglvl)462 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
463 const char *loglvl)
464 {
465 struct stackframe frame;
466
467 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
468
469 if (!tsk)
470 tsk = current;
471
472 if (regs) {
473 arm_get_current_stackframe(regs, &frame);
474 /* PC might be corrupted, use LR in that case. */
475 if (!kernel_text_address(regs->ARM_pc))
476 frame.pc = regs->ARM_lr;
477 } else if (tsk == current) {
478 frame.fp = (unsigned long)__builtin_frame_address(0);
479 frame.sp = current_stack_pointer;
480 frame.lr = (unsigned long)__builtin_return_address(0);
481 frame.pc = (unsigned long)unwind_backtrace;
482 } else {
483 /* task blocked in __switch_to */
484 frame.fp = thread_saved_fp(tsk);
485 frame.sp = thread_saved_sp(tsk);
486 /*
487 * The function calling __switch_to cannot be a leaf function
488 * so LR is recovered from the stack.
489 */
490 frame.lr = 0;
491 frame.pc = thread_saved_pc(tsk);
492 }
493
494 while (1) {
495 int urc;
496 unsigned long where = frame.pc;
497
498 urc = unwind_frame(&frame);
499 if (urc < 0)
500 break;
501 dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl);
502 }
503 }
504
unwind_table_add(unsigned long start,unsigned long size,unsigned long text_addr,unsigned long text_size)505 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
506 unsigned long text_addr,
507 unsigned long text_size)
508 {
509 unsigned long flags;
510 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
511
512 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
513 text_addr, text_size);
514
515 if (!tab)
516 return tab;
517
518 tab->start = (const struct unwind_idx *)start;
519 tab->stop = (const struct unwind_idx *)(start + size);
520 tab->origin = unwind_find_origin(tab->start, tab->stop);
521 tab->begin_addr = text_addr;
522 tab->end_addr = text_addr + text_size;
523
524 raw_spin_lock_irqsave(&unwind_lock, flags);
525 list_add_tail(&tab->list, &unwind_tables);
526 raw_spin_unlock_irqrestore(&unwind_lock, flags);
527
528 return tab;
529 }
530
unwind_table_del(struct unwind_table * tab)531 void unwind_table_del(struct unwind_table *tab)
532 {
533 unsigned long flags;
534
535 if (!tab)
536 return;
537
538 raw_spin_lock_irqsave(&unwind_lock, flags);
539 list_del(&tab->list);
540 raw_spin_unlock_irqrestore(&unwind_lock, flags);
541
542 kfree(tab);
543 }
544