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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#endif
22#endif /* __CHECKER__ */
23
24#include <linux/kernel.h>
25#include <linux/init.h>
26#include <linux/export.h>
27#include <linux/sched.h>
28#include <linux/slab.h>
29#include <linux/spinlock.h>
30#include <linux/list.h>
31#include <linux/module.h>
32
33#include <asm/stacktrace.h>
34#include <asm/traps.h>
35#include <asm/unwind.h>
36
37#include "reboot.h"
38
39/* Dummy functions to avoid linker complaints */
40void __aeabi_unwind_cpp_pr0(void)
41{
42};
43EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
44
45void __aeabi_unwind_cpp_pr1(void)
46{
47};
48EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
49
50void __aeabi_unwind_cpp_pr2(void)
51{
52};
53EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
54
55struct 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 unsigned long *lr_addr; /* address of LR value on the stack */
60 /*
61 * 1 : check for stack overflow for each register pop.
62 * 0 : save overhead if there is plenty of stack remaining.
63 */
64 int check_each_pop;
65 int entries; /* number of entries left to interpret */
66 int byte; /* current byte number in the instructions word */
67};
68
69enum regs {
70#ifdef CONFIG_THUMB2_KERNEL
71 FP = 7,
72#else
73 FP = 11,
74#endif
75 SP = 13,
76 LR = 14,
77 PC = 15
78};
79
80extern const struct unwind_idx __start_unwind_idx[];
81static const struct unwind_idx *__origin_unwind_idx;
82extern const struct unwind_idx __stop_unwind_idx[];
83
84static DEFINE_RAW_SPINLOCK(unwind_lock);
85static LIST_HEAD(unwind_tables);
86
87/* Convert a prel31 symbol to an absolute address */
88#define prel31_to_addr(ptr) \
89({ \
90 /* sign-extend to 32 bits */ \
91 long offset = (((long)*(ptr)) << 1) >> 1; \
92 (unsigned long)(ptr) + offset; \
93})
94
95/*
96 * Binary search in the unwind index. The entries are
97 * guaranteed to be sorted in ascending order by the linker.
98 *
99 * start = first entry
100 * origin = first entry with positive offset (or stop if there is no such entry)
101 * stop - 1 = last entry
102 */
103static const struct unwind_idx *search_index(unsigned long addr,
104 const struct unwind_idx *start,
105 const struct unwind_idx *origin,
106 const struct unwind_idx *stop)
107{
108 unsigned long addr_prel31;
109
110 pr_debug("%s(%08lx, %p, %p, %p)\n",
111 __func__, addr, start, origin, stop);
112
113 /*
114 * only search in the section with the matching sign. This way the
115 * prel31 numbers can be compared as unsigned longs.
116 */
117 if (addr < (unsigned long)start)
118 /* negative offsets: [start; origin) */
119 stop = origin;
120 else
121 /* positive offsets: [origin; stop) */
122 start = origin;
123
124 /* prel31 for address relavive to start */
125 addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;
126
127 while (start < stop - 1) {
128 const struct unwind_idx *mid = start + ((stop - start) >> 1);
129
130 /*
131 * As addr_prel31 is relative to start an offset is needed to
132 * make it relative to mid.
133 */
134 if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
135 mid->addr_offset)
136 stop = mid;
137 else {
138 /* keep addr_prel31 relative to start */
139 addr_prel31 -= ((unsigned long)mid -
140 (unsigned long)start);
141 start = mid;
142 }
143 }
144
145 if (likely(start->addr_offset <= addr_prel31))
146 return start;
147 else {
148 pr_warn("unwind: Unknown symbol address %08lx\n", addr);
149 return NULL;
150 }
151}
152
153static const struct unwind_idx *unwind_find_origin(
154 const struct unwind_idx *start, const struct unwind_idx *stop)
155{
156 pr_debug("%s(%p, %p)\n", __func__, start, stop);
157 while (start < stop) {
158 const struct unwind_idx *mid = start + ((stop - start) >> 1);
159
160 if (mid->addr_offset >= 0x40000000)
161 /* negative offset */
162 start = mid + 1;
163 else
164 /* positive offset */
165 stop = mid;
166 }
167 pr_debug("%s -> %p\n", __func__, stop);
168 return stop;
169}
170
171static const struct unwind_idx *unwind_find_idx(unsigned long addr)
172{
173 const struct unwind_idx *idx = NULL;
174 unsigned long flags;
175
176 pr_debug("%s(%08lx)\n", __func__, addr);
177
178 if (core_kernel_text(addr)) {
179 if (unlikely(!__origin_unwind_idx))
180 __origin_unwind_idx =
181 unwind_find_origin(__start_unwind_idx,
182 __stop_unwind_idx);
183
184 /* main unwind table */
185 idx = search_index(addr, __start_unwind_idx,
186 __origin_unwind_idx,
187 __stop_unwind_idx);
188 } else {
189 /* module unwind tables */
190 struct unwind_table *table;
191
192 raw_spin_lock_irqsave(&unwind_lock, flags);
193 list_for_each_entry(table, &unwind_tables, list) {
194 if (addr >= table->begin_addr &&
195 addr < table->end_addr) {
196 idx = search_index(addr, table->start,
197 table->origin,
198 table->stop);
199 /* Move-to-front to exploit common traces */
200 list_move(&table->list, &unwind_tables);
201 break;
202 }
203 }
204 raw_spin_unlock_irqrestore(&unwind_lock, flags);
205 }
206
207 pr_debug("%s: idx = %p\n", __func__, idx);
208 return idx;
209}
210
211static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
212{
213 unsigned long ret;
214
215 if (ctrl->entries <= 0) {
216 pr_warn("unwind: Corrupt unwind table\n");
217 return 0;
218 }
219
220 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
221
222 if (ctrl->byte == 0) {
223 ctrl->insn++;
224 ctrl->entries--;
225 ctrl->byte = 3;
226 } else
227 ctrl->byte--;
228
229 return ret;
230}
231
232/* Before poping a register check whether it is feasible or not */
233static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
234 unsigned long **vsp, unsigned int reg)
235{
236 if (unlikely(ctrl->check_each_pop))
237 if (*vsp >= (unsigned long *)ctrl->sp_high)
238 return -URC_FAILURE;
239
240 /* Use READ_ONCE_NOCHECK here to avoid this memory access
241 * from being tracked by KASAN.
242 */
243 ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp));
244 if (reg == 14)
245 ctrl->lr_addr = *vsp;
246 (*vsp)++;
247 return URC_OK;
248}
249
250/* Helper functions to execute the instructions */
251static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl,
252 unsigned long mask)
253{
254 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
255 int load_sp, reg = 4;
256
257 load_sp = mask & (1 << (13 - 4));
258 while (mask) {
259 if (mask & 1)
260 if (unwind_pop_register(ctrl, &vsp, reg))
261 return -URC_FAILURE;
262 mask >>= 1;
263 reg++;
264 }
265 if (!load_sp) {
266 ctrl->vrs[SP] = (unsigned long)vsp;
267 }
268
269 return URC_OK;
270}
271
272static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl,
273 unsigned long insn)
274{
275 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
276 int reg;
277
278 /* pop R4-R[4+bbb] */
279 for (reg = 4; reg <= 4 + (insn & 7); reg++)
280 if (unwind_pop_register(ctrl, &vsp, reg))
281 return -URC_FAILURE;
282
283 if (insn & 0x8)
284 if (unwind_pop_register(ctrl, &vsp, 14))
285 return -URC_FAILURE;
286
287 ctrl->vrs[SP] = (unsigned long)vsp;
288
289 return URC_OK;
290}
291
292static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
293 unsigned long mask)
294{
295 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
296 int reg = 0;
297
298 /* pop R0-R3 according to mask */
299 while (mask) {
300 if (mask & 1)
301 if (unwind_pop_register(ctrl, &vsp, reg))
302 return -URC_FAILURE;
303 mask >>= 1;
304 reg++;
305 }
306 ctrl->vrs[SP] = (unsigned long)vsp;
307
308 return URC_OK;
309}
310
311static unsigned long unwind_decode_uleb128(struct unwind_ctrl_block *ctrl)
312{
313 unsigned long bytes = 0;
314 unsigned long insn;
315 unsigned long result = 0;
316
317 /*
318 * unwind_get_byte() will advance `ctrl` one instruction at a time, so
319 * loop until we get an instruction byte where bit 7 is not set.
320 *
321 * Note: This decodes a maximum of 4 bytes to output 28 bits data where
322 * max is 0xfffffff: that will cover a vsp increment of 1073742336, hence
323 * it is sufficient for unwinding the stack.
324 */
325 do {
326 insn = unwind_get_byte(ctrl);
327 result |= (insn & 0x7f) << (bytes * 7);
328 bytes++;
329 } while (!!(insn & 0x80) && (bytes != sizeof(result)));
330
331 return result;
332}
333
334/*
335 * Execute the current unwind instruction.
336 */
337static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
338{
339 unsigned long insn = unwind_get_byte(ctrl);
340 int ret = URC_OK;
341
342 pr_debug("%s: insn = %08lx\n", __func__, insn);
343
344 if ((insn & 0xc0) == 0x00)
345 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
346 else if ((insn & 0xc0) == 0x40) {
347 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
348 } else if ((insn & 0xf0) == 0x80) {
349 unsigned long mask;
350
351 insn = (insn << 8) | unwind_get_byte(ctrl);
352 mask = insn & 0x0fff;
353 if (mask == 0) {
354 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n",
355 insn);
356 return -URC_FAILURE;
357 }
358
359 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask);
360 if (ret)
361 goto error;
362 } else if ((insn & 0xf0) == 0x90 &&
363 (insn & 0x0d) != 0x0d) {
364 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
365 } else if ((insn & 0xf0) == 0xa0) {
366 ret = unwind_exec_pop_r4_to_rN(ctrl, insn);
367 if (ret)
368 goto error;
369 } else if (insn == 0xb0) {
370 if (ctrl->vrs[PC] == 0)
371 ctrl->vrs[PC] = ctrl->vrs[LR];
372 /* no further processing */
373 ctrl->entries = 0;
374 } else if (insn == 0xb1) {
375 unsigned long mask = unwind_get_byte(ctrl);
376
377 if (mask == 0 || mask & 0xf0) {
378 pr_warn("unwind: Spare encoding %04lx\n",
379 (insn << 8) | mask);
380 return -URC_FAILURE;
381 }
382
383 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask);
384 if (ret)
385 goto error;
386 } else if (insn == 0xb2) {
387 unsigned long uleb128 = unwind_decode_uleb128(ctrl);
388
389 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
390 } else {
391 pr_warn("unwind: Unhandled instruction %02lx\n", insn);
392 return -URC_FAILURE;
393 }
394
395 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
396 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
397
398error:
399 return ret;
400}
401
402/*
403 * Unwind a single frame starting with *sp for the symbol at *pc. It
404 * updates the *pc and *sp with the new values.
405 */
406int unwind_frame(struct stackframe *frame)
407{
408 const struct unwind_idx *idx;
409 struct unwind_ctrl_block ctrl;
410 unsigned long sp_low;
411
412 /* store the highest address on the stack to avoid crossing it*/
413 sp_low = frame->sp;
414 ctrl.sp_high = ALIGN(sp_low - THREAD_SIZE, THREAD_ALIGN)
415 + THREAD_SIZE;
416
417 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
418 frame->pc, frame->lr, frame->sp);
419
420 idx = unwind_find_idx(frame->pc);
421 if (!idx) {
422 if (frame->pc && kernel_text_address(frame->pc)) {
423 if (in_module_plt(frame->pc) && frame->pc != frame->lr) {
424 /*
425 * Quoting Ard: Veneers only set PC using a
426 * PC+immediate LDR, and so they don't affect
427 * the state of the stack or the register file
428 */
429 frame->pc = frame->lr;
430 return URC_OK;
431 }
432 pr_warn("unwind: Index not found %08lx\n", frame->pc);
433 }
434 return -URC_FAILURE;
435 }
436
437 ctrl.vrs[FP] = frame->fp;
438 ctrl.vrs[SP] = frame->sp;
439 ctrl.vrs[LR] = frame->lr;
440 ctrl.vrs[PC] = 0;
441
442 if (idx->insn == 1)
443 /* can't unwind */
444 return -URC_FAILURE;
445 else if (frame->pc == prel31_to_addr(&idx->addr_offset)) {
446 /*
447 * Unwinding is tricky when we're halfway through the prologue,
448 * since the stack frame that the unwinder expects may not be
449 * fully set up yet. However, one thing we do know for sure is
450 * that if we are unwinding from the very first instruction of
451 * a function, we are still effectively in the stack frame of
452 * the caller, and the unwind info has no relevance yet.
453 */
454 if (frame->pc == frame->lr)
455 return -URC_FAILURE;
456 frame->pc = frame->lr;
457 return URC_OK;
458 } else if ((idx->insn & 0x80000000) == 0)
459 /* prel31 to the unwind table */
460 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
461 else if ((idx->insn & 0xff000000) == 0x80000000)
462 /* only personality routine 0 supported in the index */
463 ctrl.insn = &idx->insn;
464 else {
465 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n",
466 idx->insn, idx);
467 return -URC_FAILURE;
468 }
469
470 /* check the personality routine */
471 if ((*ctrl.insn & 0xff000000) == 0x80000000) {
472 ctrl.byte = 2;
473 ctrl.entries = 1;
474 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
475 ctrl.byte = 1;
476 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
477 } else {
478 pr_warn("unwind: Unsupported personality routine %08lx at %p\n",
479 *ctrl.insn, ctrl.insn);
480 return -URC_FAILURE;
481 }
482
483 ctrl.check_each_pop = 0;
484
485 if (prel31_to_addr(&idx->addr_offset) == (u32)&call_with_stack) {
486 /*
487 * call_with_stack() is the only place where we permit SP to
488 * jump from one stack to another, and since we know it is
489 * guaranteed to happen, set up the SP bounds accordingly.
490 */
491 sp_low = frame->fp;
492 ctrl.sp_high = ALIGN(frame->fp, THREAD_SIZE);
493 }
494
495 while (ctrl.entries > 0) {
496 int urc;
497 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs))
498 ctrl.check_each_pop = 1;
499 urc = unwind_exec_insn(&ctrl);
500 if (urc < 0)
501 return urc;
502 if (ctrl.vrs[SP] < sp_low || ctrl.vrs[SP] > ctrl.sp_high)
503 return -URC_FAILURE;
504 }
505
506 if (ctrl.vrs[PC] == 0)
507 ctrl.vrs[PC] = ctrl.vrs[LR];
508
509 /* check for infinite loop */
510 if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP])
511 return -URC_FAILURE;
512
513 frame->fp = ctrl.vrs[FP];
514 frame->sp = ctrl.vrs[SP];
515 frame->lr = ctrl.vrs[LR];
516 frame->pc = ctrl.vrs[PC];
517 frame->lr_addr = ctrl.lr_addr;
518
519 return URC_OK;
520}
521
522void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
523 const char *loglvl)
524{
525 struct stackframe frame;
526
527 printk("%sCall trace: ", loglvl);
528
529 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
530
531 if (!tsk)
532 tsk = current;
533
534 if (regs) {
535 arm_get_current_stackframe(regs, &frame);
536 /* PC might be corrupted, use LR in that case. */
537 if (!kernel_text_address(regs->ARM_pc))
538 frame.pc = regs->ARM_lr;
539 } else if (tsk == current) {
540 frame.fp = (unsigned long)__builtin_frame_address(0);
541 frame.sp = current_stack_pointer;
542 frame.lr = (unsigned long)__builtin_return_address(0);
543 /* We are saving the stack and execution state at this
544 * point, so we should ensure that frame.pc is within
545 * this block of code.
546 */
547here:
548 frame.pc = (unsigned long)&&here;
549 } else {
550 /* task blocked in __switch_to */
551 frame.fp = thread_saved_fp(tsk);
552 frame.sp = thread_saved_sp(tsk);
553 /*
554 * The function calling __switch_to cannot be a leaf function
555 * so LR is recovered from the stack.
556 */
557 frame.lr = 0;
558 frame.pc = thread_saved_pc(tsk);
559 }
560
561 while (1) {
562 int urc;
563 unsigned long where = frame.pc;
564
565 urc = unwind_frame(&frame);
566 if (urc < 0)
567 break;
568 dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl);
569 }
570}
571
572struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
573 unsigned long text_addr,
574 unsigned long text_size)
575{
576 unsigned long flags;
577 struct unwind_table *tab = kmalloc_obj(*tab);
578
579 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
580 text_addr, text_size);
581
582 if (!tab)
583 return tab;
584
585 tab->start = (const struct unwind_idx *)start;
586 tab->stop = (const struct unwind_idx *)(start + size);
587 tab->origin = unwind_find_origin(tab->start, tab->stop);
588 tab->begin_addr = text_addr;
589 tab->end_addr = text_addr + text_size;
590
591 raw_spin_lock_irqsave(&unwind_lock, flags);
592 list_add_tail(&tab->list, &unwind_tables);
593 raw_spin_unlock_irqrestore(&unwind_lock, flags);
594
595 return tab;
596}
597
598void unwind_table_del(struct unwind_table *tab)
599{
600 unsigned long flags;
601
602 if (!tab)
603 return;
604
605 raw_spin_lock_irqsave(&unwind_lock, flags);
606 list_del(&tab->list);
607 raw_spin_unlock_irqrestore(&unwind_lock, flags);
608
609 kfree(tab);
610}