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
32 #include <asm/stacktrace.h>
33 #include <asm/traps.h>
34 #include <asm/unwind.h>
35
36 #include "reboot.h"
37
38 /* Dummy functions to avoid linker complaints */
__aeabi_unwind_cpp_pr0(void)39 void __aeabi_unwind_cpp_pr0(void)
40 {
41 };
42 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
43
__aeabi_unwind_cpp_pr1(void)44 void __aeabi_unwind_cpp_pr1(void)
45 {
46 };
47 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
48
__aeabi_unwind_cpp_pr2(void)49 void __aeabi_unwind_cpp_pr2(void)
50 {
51 };
52 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
53
54 struct unwind_ctrl_block {
55 unsigned long vrs[16]; /* virtual register set */
56 const unsigned long *insn; /* pointer to the current instructions word */
57 unsigned long sp_high; /* highest value of sp allowed */
58 unsigned long *lr_addr; /* address of LR value on the stack */
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 if (reg == 14)
244 ctrl->lr_addr = *vsp;
245 (*vsp)++;
246 return URC_OK;
247 }
248
249 /* Helper functions to execute the instructions */
unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block * ctrl,unsigned long mask)250 static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl,
251 unsigned long mask)
252 {
253 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
254 int load_sp, reg = 4;
255
256 load_sp = mask & (1 << (13 - 4));
257 while (mask) {
258 if (mask & 1)
259 if (unwind_pop_register(ctrl, &vsp, reg))
260 return -URC_FAILURE;
261 mask >>= 1;
262 reg++;
263 }
264 if (!load_sp) {
265 ctrl->vrs[SP] = (unsigned long)vsp;
266 }
267
268 return URC_OK;
269 }
270
unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block * ctrl,unsigned long insn)271 static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl,
272 unsigned long insn)
273 {
274 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
275 int reg;
276
277 /* pop R4-R[4+bbb] */
278 for (reg = 4; reg <= 4 + (insn & 7); reg++)
279 if (unwind_pop_register(ctrl, &vsp, reg))
280 return -URC_FAILURE;
281
282 if (insn & 0x8)
283 if (unwind_pop_register(ctrl, &vsp, 14))
284 return -URC_FAILURE;
285
286 ctrl->vrs[SP] = (unsigned long)vsp;
287
288 return URC_OK;
289 }
290
unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block * ctrl,unsigned long mask)291 static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
292 unsigned long mask)
293 {
294 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
295 int reg = 0;
296
297 /* pop R0-R3 according to mask */
298 while (mask) {
299 if (mask & 1)
300 if (unwind_pop_register(ctrl, &vsp, reg))
301 return -URC_FAILURE;
302 mask >>= 1;
303 reg++;
304 }
305 ctrl->vrs[SP] = (unsigned long)vsp;
306
307 return URC_OK;
308 }
309
310 /*
311 * Execute the current unwind instruction.
312 */
unwind_exec_insn(struct unwind_ctrl_block * ctrl)313 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
314 {
315 unsigned long insn = unwind_get_byte(ctrl);
316 int ret = URC_OK;
317
318 pr_debug("%s: insn = %08lx\n", __func__, insn);
319
320 if ((insn & 0xc0) == 0x00)
321 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
322 else if ((insn & 0xc0) == 0x40) {
323 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
324 } else if ((insn & 0xf0) == 0x80) {
325 unsigned long mask;
326
327 insn = (insn << 8) | unwind_get_byte(ctrl);
328 mask = insn & 0x0fff;
329 if (mask == 0) {
330 pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n",
331 insn);
332 return -URC_FAILURE;
333 }
334
335 ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask);
336 if (ret)
337 goto error;
338 } else if ((insn & 0xf0) == 0x90 &&
339 (insn & 0x0d) != 0x0d) {
340 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
341 } else if ((insn & 0xf0) == 0xa0) {
342 ret = unwind_exec_pop_r4_to_rN(ctrl, insn);
343 if (ret)
344 goto error;
345 } else if (insn == 0xb0) {
346 if (ctrl->vrs[PC] == 0)
347 ctrl->vrs[PC] = ctrl->vrs[LR];
348 /* no further processing */
349 ctrl->entries = 0;
350 } else if (insn == 0xb1) {
351 unsigned long mask = unwind_get_byte(ctrl);
352
353 if (mask == 0 || mask & 0xf0) {
354 pr_warn("unwind: Spare encoding %04lx\n",
355 (insn << 8) | mask);
356 return -URC_FAILURE;
357 }
358
359 ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask);
360 if (ret)
361 goto error;
362 } else if (insn == 0xb2) {
363 unsigned long uleb128 = unwind_get_byte(ctrl);
364
365 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
366 } else {
367 pr_warn("unwind: Unhandled instruction %02lx\n", insn);
368 return -URC_FAILURE;
369 }
370
371 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
372 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
373
374 error:
375 return ret;
376 }
377
378 /*
379 * Unwind a single frame starting with *sp for the symbol at *pc. It
380 * updates the *pc and *sp with the new values.
381 */
unwind_frame(struct stackframe * frame)382 int unwind_frame(struct stackframe *frame)
383 {
384 const struct unwind_idx *idx;
385 struct unwind_ctrl_block ctrl;
386 unsigned long sp_low;
387
388 /* store the highest address on the stack to avoid crossing it*/
389 sp_low = frame->sp;
390 ctrl.sp_high = ALIGN(sp_low - THREAD_SIZE, THREAD_ALIGN)
391 + THREAD_SIZE;
392
393 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
394 frame->pc, frame->lr, frame->sp);
395
396 idx = unwind_find_idx(frame->pc);
397 if (!idx) {
398 if (frame->pc && kernel_text_address(frame->pc))
399 pr_warn("unwind: Index not found %08lx\n", frame->pc);
400 return -URC_FAILURE;
401 }
402
403 ctrl.vrs[FP] = frame->fp;
404 ctrl.vrs[SP] = frame->sp;
405 ctrl.vrs[LR] = frame->lr;
406 ctrl.vrs[PC] = 0;
407
408 if (idx->insn == 1)
409 /* can't unwind */
410 return -URC_FAILURE;
411 else if (frame->pc == prel31_to_addr(&idx->addr_offset)) {
412 /*
413 * Unwinding is tricky when we're halfway through the prologue,
414 * since the stack frame that the unwinder expects may not be
415 * fully set up yet. However, one thing we do know for sure is
416 * that if we are unwinding from the very first instruction of
417 * a function, we are still effectively in the stack frame of
418 * the caller, and the unwind info has no relevance yet.
419 */
420 if (frame->pc == frame->lr)
421 return -URC_FAILURE;
422 frame->pc = frame->lr;
423 return URC_OK;
424 } else if ((idx->insn & 0x80000000) == 0)
425 /* prel31 to the unwind table */
426 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
427 else if ((idx->insn & 0xff000000) == 0x80000000)
428 /* only personality routine 0 supported in the index */
429 ctrl.insn = &idx->insn;
430 else {
431 pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n",
432 idx->insn, idx);
433 return -URC_FAILURE;
434 }
435
436 /* check the personality routine */
437 if ((*ctrl.insn & 0xff000000) == 0x80000000) {
438 ctrl.byte = 2;
439 ctrl.entries = 1;
440 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
441 ctrl.byte = 1;
442 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
443 } else {
444 pr_warn("unwind: Unsupported personality routine %08lx at %p\n",
445 *ctrl.insn, ctrl.insn);
446 return -URC_FAILURE;
447 }
448
449 ctrl.check_each_pop = 0;
450
451 if (prel31_to_addr(&idx->addr_offset) == (u32)&call_with_stack) {
452 /*
453 * call_with_stack() is the only place where we permit SP to
454 * jump from one stack to another, and since we know it is
455 * guaranteed to happen, set up the SP bounds accordingly.
456 */
457 sp_low = frame->fp;
458 ctrl.sp_high = ALIGN(frame->fp, THREAD_SIZE);
459 }
460
461 while (ctrl.entries > 0) {
462 int urc;
463 if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs))
464 ctrl.check_each_pop = 1;
465 urc = unwind_exec_insn(&ctrl);
466 if (urc < 0)
467 return urc;
468 if (ctrl.vrs[SP] < sp_low || ctrl.vrs[SP] > ctrl.sp_high)
469 return -URC_FAILURE;
470 }
471
472 if (ctrl.vrs[PC] == 0)
473 ctrl.vrs[PC] = ctrl.vrs[LR];
474
475 /* check for infinite loop */
476 if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP])
477 return -URC_FAILURE;
478
479 frame->fp = ctrl.vrs[FP];
480 frame->sp = ctrl.vrs[SP];
481 frame->lr = ctrl.vrs[LR];
482 frame->pc = ctrl.vrs[PC];
483 frame->lr_addr = ctrl.lr_addr;
484
485 return URC_OK;
486 }
487
unwind_backtrace(struct pt_regs * regs,struct task_struct * tsk,const char * loglvl)488 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
489 const char *loglvl)
490 {
491 struct stackframe frame;
492
493 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
494
495 if (!tsk)
496 tsk = current;
497
498 if (regs) {
499 arm_get_current_stackframe(regs, &frame);
500 /* PC might be corrupted, use LR in that case. */
501 if (!kernel_text_address(regs->ARM_pc))
502 frame.pc = regs->ARM_lr;
503 } else if (tsk == current) {
504 frame.fp = (unsigned long)__builtin_frame_address(0);
505 frame.sp = current_stack_pointer;
506 frame.lr = (unsigned long)__builtin_return_address(0);
507 /* We are saving the stack and execution state at this
508 * point, so we should ensure that frame.pc is within
509 * this block of code.
510 */
511 here:
512 frame.pc = (unsigned long)&&here;
513 } else {
514 /* task blocked in __switch_to */
515 frame.fp = thread_saved_fp(tsk);
516 frame.sp = thread_saved_sp(tsk);
517 /*
518 * The function calling __switch_to cannot be a leaf function
519 * so LR is recovered from the stack.
520 */
521 frame.lr = 0;
522 frame.pc = thread_saved_pc(tsk);
523 }
524
525 while (1) {
526 int urc;
527 unsigned long where = frame.pc;
528
529 urc = unwind_frame(&frame);
530 if (urc < 0)
531 break;
532 dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl);
533 }
534 }
535
unwind_table_add(unsigned long start,unsigned long size,unsigned long text_addr,unsigned long text_size)536 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
537 unsigned long text_addr,
538 unsigned long text_size)
539 {
540 unsigned long flags;
541 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
542
543 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
544 text_addr, text_size);
545
546 if (!tab)
547 return tab;
548
549 tab->start = (const struct unwind_idx *)start;
550 tab->stop = (const struct unwind_idx *)(start + size);
551 tab->origin = unwind_find_origin(tab->start, tab->stop);
552 tab->begin_addr = text_addr;
553 tab->end_addr = text_addr + text_size;
554
555 raw_spin_lock_irqsave(&unwind_lock, flags);
556 list_add_tail(&tab->list, &unwind_tables);
557 raw_spin_unlock_irqrestore(&unwind_lock, flags);
558
559 return tab;
560 }
561
unwind_table_del(struct unwind_table * tab)562 void unwind_table_del(struct unwind_table *tab)
563 {
564 unsigned long flags;
565
566 if (!tab)
567 return;
568
569 raw_spin_lock_irqsave(&unwind_lock, flags);
570 list_del(&tab->list);
571 raw_spin_unlock_irqrestore(&unwind_lock, flags);
572
573 kfree(tab);
574 }
575