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