1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/objtool.h>
3 #include <linux/module.h>
4 #include <linux/sort.h>
5 #include <asm/exception.h>
6 #include <asm/orc_header.h>
7 #include <asm/orc_lookup.h>
8 #include <asm/orc_types.h>
9 #include <asm/ptrace.h>
10 #include <asm/setup.h>
11 #include <asm/stacktrace.h>
12 #include <asm/tlb.h>
13 #include <asm/unwind.h>
14
15 ORC_HEADER;
16
17 #define orc_warn(fmt, ...) \
18 printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
19
20 extern int __start_orc_unwind_ip[];
21 extern int __stop_orc_unwind_ip[];
22 extern struct orc_entry __start_orc_unwind[];
23 extern struct orc_entry __stop_orc_unwind[];
24
25 static bool orc_init __ro_after_init;
26 static unsigned int lookup_num_blocks __ro_after_init;
27
28 /* Fake frame pointer entry -- used as a fallback for generated code */
29 static struct orc_entry orc_fp_entry = {
30 .sp_reg = ORC_REG_FP,
31 .sp_offset = 16,
32 .fp_reg = ORC_REG_PREV_SP,
33 .fp_offset = -16,
34 .ra_reg = ORC_REG_PREV_SP,
35 .ra_offset = -8,
36 .type = ORC_TYPE_CALL
37 };
38
39 /*
40 * If we crash with IP==0, the last successfully executed instruction
41 * was probably an indirect function call with a NULL function pointer,
42 * and we don't have unwind information for NULL.
43 * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function
44 * pointer into its parent and then continue normally from there.
45 */
46 static struct orc_entry orc_null_entry = {
47 .sp_reg = ORC_REG_SP,
48 .sp_offset = sizeof(long),
49 .fp_reg = ORC_REG_UNDEFINED,
50 .type = ORC_TYPE_CALL
51 };
52
53 static inline unsigned long orc_ip(const int *ip)
54 {
55 return (unsigned long)ip + *ip;
56 }
57
58 static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
59 unsigned int num_entries, unsigned long ip)
60 {
61 int *first = ip_table;
62 int *mid = first, *found = first;
63 int *last = ip_table + num_entries - 1;
64
65 if (!num_entries)
66 return NULL;
67
68 /*
69 * Do a binary range search to find the rightmost duplicate of a given
70 * starting address. Some entries are section terminators which are
71 * "weak" entries for ensuring there are no gaps. They should be
72 * ignored when they conflict with a real entry.
73 */
74 while (first <= last) {
75 mid = first + ((last - first) / 2);
76
77 if (orc_ip(mid) <= ip) {
78 found = mid;
79 first = mid + 1;
80 } else
81 last = mid - 1;
82 }
83
84 return u_table + (found - ip_table);
85 }
86
87 #ifdef CONFIG_MODULES
88 static struct orc_entry *orc_module_find(unsigned long ip)
89 {
90 struct module *mod;
91
92 mod = __module_address(ip);
93 if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip)
94 return NULL;
95
96 return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind, mod->arch.num_orcs, ip);
97 }
98 #else
99 static struct orc_entry *orc_module_find(unsigned long ip)
100 {
101 return NULL;
102 }
103 #endif
104
105 #ifdef CONFIG_DYNAMIC_FTRACE
106 static struct orc_entry *orc_find(unsigned long ip);
107
108 /*
109 * Ftrace dynamic trampolines do not have orc entries of their own.
110 * But they are copies of the ftrace entries that are static and
111 * defined in ftrace_*.S, which do have orc entries.
112 *
113 * If the unwinder comes across a ftrace trampoline, then find the
114 * ftrace function that was used to create it, and use that ftrace
115 * function's orc entry, as the placement of the return code in
116 * the stack will be identical.
117 */
118 static struct orc_entry *orc_ftrace_find(unsigned long ip)
119 {
120 struct ftrace_ops *ops;
121 unsigned long tramp_addr, offset;
122
123 ops = ftrace_ops_trampoline(ip);
124 if (!ops)
125 return NULL;
126
127 /* Set tramp_addr to the start of the code copied by the trampoline */
128 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
129 tramp_addr = (unsigned long)ftrace_regs_caller;
130 else
131 tramp_addr = (unsigned long)ftrace_caller;
132
133 /* Now place tramp_addr to the location within the trampoline ip is at */
134 offset = ip - ops->trampoline;
135 tramp_addr += offset;
136
137 /* Prevent unlikely recursion */
138 if (ip == tramp_addr)
139 return NULL;
140
141 return orc_find(tramp_addr);
142 }
143 #else
144 static struct orc_entry *orc_ftrace_find(unsigned long ip)
145 {
146 return NULL;
147 }
148 #endif
149
150 static struct orc_entry *orc_find(unsigned long ip)
151 {
152 static struct orc_entry *orc;
153
154 if (ip == 0)
155 return &orc_null_entry;
156
157 /* For non-init vmlinux addresses, use the fast lookup table: */
158 if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
159 unsigned int idx, start, stop;
160
161 idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;
162
163 if (unlikely((idx >= lookup_num_blocks-1))) {
164 orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n",
165 idx, lookup_num_blocks, (void *)ip);
166 return NULL;
167 }
168
169 start = orc_lookup[idx];
170 stop = orc_lookup[idx + 1] + 1;
171
172 if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
173 (__start_orc_unwind + stop > __stop_orc_unwind))) {
174 orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n",
175 idx, lookup_num_blocks, start, stop, (void *)ip);
176 return NULL;
177 }
178
179 return __orc_find(__start_orc_unwind_ip + start,
180 __start_orc_unwind + start, stop - start, ip);
181 }
182
183 /* vmlinux .init slow lookup: */
184 if (is_kernel_inittext(ip))
185 return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
186 __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);
187
188 /* Module lookup: */
189 orc = orc_module_find(ip);
190 if (orc)
191 return orc;
192
193 return orc_ftrace_find(ip);
194 }
195
196 #ifdef CONFIG_MODULES
197
198 static DEFINE_MUTEX(sort_mutex);
199 static int *cur_orc_ip_table = __start_orc_unwind_ip;
200 static struct orc_entry *cur_orc_table = __start_orc_unwind;
201
202 static void orc_sort_swap(void *_a, void *_b, int size)
203 {
204 int delta = _b - _a;
205 int *a = _a, *b = _b, tmp;
206 struct orc_entry *orc_a, *orc_b;
207
208 /* Swap the .orc_unwind_ip entries: */
209 tmp = *a;
210 *a = *b + delta;
211 *b = tmp - delta;
212
213 /* Swap the corresponding .orc_unwind entries: */
214 orc_a = cur_orc_table + (a - cur_orc_ip_table);
215 orc_b = cur_orc_table + (b - cur_orc_ip_table);
216 swap(*orc_a, *orc_b);
217 }
218
219 static int orc_sort_cmp(const void *_a, const void *_b)
220 {
221 const int *a = _a, *b = _b;
222 unsigned long a_val = orc_ip(a);
223 unsigned long b_val = orc_ip(b);
224 struct orc_entry *orc_a;
225
226 if (a_val > b_val)
227 return 1;
228 if (a_val < b_val)
229 return -1;
230
231 /*
232 * The "weak" section terminator entries need to always be first
233 * to ensure the lookup code skips them in favor of real entries.
234 * These terminator entries exist to handle any gaps created by
235 * whitelisted .o files which didn't get objtool generation.
236 */
237 orc_a = cur_orc_table + (a - cur_orc_ip_table);
238
239 return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
240 }
241
242 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
243 void *_orc, size_t orc_size)
244 {
245 int *orc_ip = _orc_ip;
246 struct orc_entry *orc = _orc;
247 unsigned int num_entries = orc_ip_size / sizeof(int);
248
249 WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
250 orc_size % sizeof(*orc) != 0 ||
251 num_entries != orc_size / sizeof(*orc));
252
253 /*
254 * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
255 * associate an .orc_unwind_ip table entry with its corresponding
256 * .orc_unwind entry so they can both be swapped.
257 */
258 mutex_lock(&sort_mutex);
259 cur_orc_ip_table = orc_ip;
260 cur_orc_table = orc;
261 sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
262 mutex_unlock(&sort_mutex);
263
264 mod->arch.orc_unwind_ip = orc_ip;
265 mod->arch.orc_unwind = orc;
266 mod->arch.num_orcs = num_entries;
267 }
268 #endif
269
270 void __init unwind_init(void)
271 {
272 int i;
273 size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
274 size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
275 size_t num_entries = orc_ip_size / sizeof(int);
276 struct orc_entry *orc;
277
278 if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
279 orc_size % sizeof(struct orc_entry) != 0 ||
280 num_entries != orc_size / sizeof(struct orc_entry)) {
281 orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n");
282 return;
283 }
284
285 /*
286 * Note, the orc_unwind and orc_unwind_ip tables were already
287 * sorted at build time via the 'sorttable' tool.
288 * It's ready for binary search straight away, no need to sort it.
289 */
290
291 /* Initialize the fast lookup table: */
292 lookup_num_blocks = orc_lookup_end - orc_lookup;
293 for (i = 0; i < lookup_num_blocks-1; i++) {
294 orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
295 num_entries, LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
296 if (!orc) {
297 orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
298 return;
299 }
300
301 orc_lookup[i] = orc - __start_orc_unwind;
302 }
303
304 /* Initialize the ending block: */
305 orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries, LOOKUP_STOP_IP);
306 if (!orc) {
307 orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n");
308 return;
309 }
310 orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;
311
312 orc_init = true;
313 }
314
315 static inline bool on_stack(struct stack_info *info, unsigned long addr, size_t len)
316 {
317 unsigned long begin = info->begin;
318 unsigned long end = info->end;
319
320 return (info->type != STACK_TYPE_UNKNOWN &&
321 addr >= begin && addr < end && addr + len > begin && addr + len <= end);
322 }
323
324 static bool stack_access_ok(struct unwind_state *state, unsigned long addr, size_t len)
325 {
326 struct stack_info *info = &state->stack_info;
327
328 if (on_stack(info, addr, len))
329 return true;
330
331 return !get_stack_info(addr, state->task, info) && on_stack(info, addr, len);
332 }
333
334 unsigned long unwind_get_return_address(struct unwind_state *state)
335 {
336 return __unwind_get_return_address(state);
337 }
338 EXPORT_SYMBOL_GPL(unwind_get_return_address);
339
340 void unwind_start(struct unwind_state *state, struct task_struct *task,
341 struct pt_regs *regs)
342 {
343 __unwind_start(state, task, regs);
344 state->type = UNWINDER_ORC;
345 if (!unwind_done(state) && !__kernel_text_address(state->pc))
346 unwind_next_frame(state);
347 }
348 EXPORT_SYMBOL_GPL(unwind_start);
349
350 static bool is_entry_func(unsigned long addr)
351 {
352 extern u32 kernel_entry;
353 extern u32 kernel_entry_end;
354
355 return addr >= (unsigned long)&kernel_entry && addr < (unsigned long)&kernel_entry_end;
356 }
357
358 static inline unsigned long bt_address(unsigned long ra)
359 {
360 extern unsigned long eentry;
361
362 if (__kernel_text_address(ra))
363 return ra;
364
365 if (__module_text_address(ra))
366 return ra;
367
368 if (ra >= eentry && ra < eentry + EXCCODE_INT_END * VECSIZE) {
369 unsigned long func;
370 unsigned long type = (ra - eentry) / VECSIZE;
371 unsigned long offset = (ra - eentry) % VECSIZE;
372
373 switch (type) {
374 case 0 ... EXCCODE_INT_START - 1:
375 func = (unsigned long)exception_table[type];
376 break;
377 case EXCCODE_INT_START ... EXCCODE_INT_END:
378 func = (unsigned long)handle_vint;
379 break;
380 default:
381 func = (unsigned long)handle_reserved;
382 break;
383 }
384
385 return func + offset;
386 }
387
388 return ra;
389 }
390
391 bool unwind_next_frame(struct unwind_state *state)
392 {
393 unsigned long *p, pc;
394 struct pt_regs *regs;
395 struct orc_entry *orc;
396 struct stack_info *info = &state->stack_info;
397
398 if (unwind_done(state))
399 return false;
400
401 /* Don't let modules unload while we're reading their ORC data. */
402 preempt_disable();
403
404 if (is_entry_func(state->pc))
405 goto end;
406
407 orc = orc_find(state->pc);
408 if (!orc) {
409 /*
410 * As a fallback, try to assume this code uses a frame pointer.
411 * This is useful for generated code, like BPF, which ORC
412 * doesn't know about. This is just a guess, so the rest of
413 * the unwind is no longer considered reliable.
414 */
415 orc = &orc_fp_entry;
416 state->error = true;
417 } else {
418 if (orc->type == ORC_TYPE_UNDEFINED)
419 goto err;
420
421 if (orc->type == ORC_TYPE_END_OF_STACK)
422 goto end;
423 }
424
425 switch (orc->sp_reg) {
426 case ORC_REG_SP:
427 if (info->type == STACK_TYPE_IRQ && state->sp == info->end)
428 orc->type = ORC_TYPE_REGS;
429 else
430 state->sp = state->sp + orc->sp_offset;
431 break;
432 case ORC_REG_FP:
433 state->sp = state->fp;
434 break;
435 default:
436 orc_warn("unknown SP base reg %d at %pB\n", orc->sp_reg, (void *)state->pc);
437 goto err;
438 }
439
440 switch (orc->fp_reg) {
441 case ORC_REG_PREV_SP:
442 p = (unsigned long *)(state->sp + orc->fp_offset);
443 if (!stack_access_ok(state, (unsigned long)p, sizeof(unsigned long)))
444 goto err;
445
446 state->fp = *p;
447 break;
448 case ORC_REG_UNDEFINED:
449 /* Nothing. */
450 break;
451 default:
452 orc_warn("unknown FP base reg %d at %pB\n", orc->fp_reg, (void *)state->pc);
453 goto err;
454 }
455
456 switch (orc->type) {
457 case ORC_TYPE_CALL:
458 if (orc->ra_reg == ORC_REG_PREV_SP) {
459 p = (unsigned long *)(state->sp + orc->ra_offset);
460 if (!stack_access_ok(state, (unsigned long)p, sizeof(unsigned long)))
461 goto err;
462
463 pc = unwind_graph_addr(state, *p, state->sp);
464 pc -= LOONGARCH_INSN_SIZE;
465 } else if (orc->ra_reg == ORC_REG_UNDEFINED) {
466 if (!state->ra || state->ra == state->pc)
467 goto err;
468
469 pc = unwind_graph_addr(state, state->ra, state->sp);
470 pc -= LOONGARCH_INSN_SIZE;
471 state->ra = 0;
472 } else {
473 orc_warn("unknown ra base reg %d at %pB\n", orc->ra_reg, (void *)state->pc);
474 goto err;
475 }
476 break;
477 case ORC_TYPE_REGS:
478 if (info->type == STACK_TYPE_IRQ && state->sp == info->end)
479 regs = (struct pt_regs *)info->next_sp;
480 else
481 regs = (struct pt_regs *)state->sp;
482
483 if (!stack_access_ok(state, (unsigned long)regs, sizeof(*regs)))
484 goto err;
485
486 if ((info->end == (unsigned long)regs + sizeof(*regs)) &&
487 !regs->regs[3] && !regs->regs[1])
488 goto end;
489
490 if (user_mode(regs))
491 goto end;
492
493 pc = regs->csr_era;
494 if (!__kernel_text_address(pc))
495 goto err;
496
497 state->sp = regs->regs[3];
498 state->ra = regs->regs[1];
499 state->fp = regs->regs[22];
500 get_stack_info(state->sp, state->task, info);
501
502 break;
503 default:
504 orc_warn("unknown .orc_unwind entry type %d at %pB\n", orc->type, (void *)state->pc);
505 goto err;
506 }
507
508 state->pc = bt_address(pc);
509 if (!state->pc) {
510 pr_err("cannot find unwind pc at %pK\n", (void *)pc);
511 goto err;
512 }
513
514 if (!__kernel_text_address(state->pc))
515 goto err;
516
517 preempt_enable();
518 return true;
519
520 err:
521 state->error = true;
522
523 end:
524 preempt_enable();
525 state->stack_info.type = STACK_TYPE_UNKNOWN;
526 return false;
527 }
528 EXPORT_SYMBOL_GPL(unwind_next_frame);
529
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