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TOMOYO Linux Cross Reference
Linux/arch/x86/kernel/unwind_orc.c

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  1 #include <linux/module.h>
  2 #include <linux/sort.h>
  3 #include <asm/ptrace.h>
  4 #include <asm/stacktrace.h>
  5 #include <asm/unwind.h>
  6 #include <asm/orc_types.h>
  7 #include <asm/orc_lookup.h>
  8 
  9 #define orc_warn(fmt, ...) \
 10         printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__)
 11 
 12 extern int __start_orc_unwind_ip[];
 13 extern int __stop_orc_unwind_ip[];
 14 extern struct orc_entry __start_orc_unwind[];
 15 extern struct orc_entry __stop_orc_unwind[];
 16 
 17 static DEFINE_MUTEX(sort_mutex);
 18 int *cur_orc_ip_table = __start_orc_unwind_ip;
 19 struct orc_entry *cur_orc_table = __start_orc_unwind;
 20 
 21 unsigned int lookup_num_blocks;
 22 bool orc_init;
 23 
 24 static inline unsigned long orc_ip(const int *ip)
 25 {
 26         return (unsigned long)ip + *ip;
 27 }
 28 
 29 static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
 30                                     unsigned int num_entries, unsigned long ip)
 31 {
 32         int *first = ip_table;
 33         int *last = ip_table + num_entries - 1;
 34         int *mid = first, *found = first;
 35 
 36         if (!num_entries)
 37                 return NULL;
 38 
 39         /*
 40          * Do a binary range search to find the rightmost duplicate of a given
 41          * starting address.  Some entries are section terminators which are
 42          * "weak" entries for ensuring there are no gaps.  They should be
 43          * ignored when they conflict with a real entry.
 44          */
 45         while (first <= last) {
 46                 mid = first + ((last - first) / 2);
 47 
 48                 if (orc_ip(mid) <= ip) {
 49                         found = mid;
 50                         first = mid + 1;
 51                 } else
 52                         last = mid - 1;
 53         }
 54 
 55         return u_table + (found - ip_table);
 56 }
 57 
 58 #ifdef CONFIG_MODULES
 59 static struct orc_entry *orc_module_find(unsigned long ip)
 60 {
 61         struct module *mod;
 62 
 63         mod = __module_address(ip);
 64         if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip)
 65                 return NULL;
 66         return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind,
 67                           mod->arch.num_orcs, ip);
 68 }
 69 #else
 70 static struct orc_entry *orc_module_find(unsigned long ip)
 71 {
 72         return NULL;
 73 }
 74 #endif
 75 
 76 #ifdef CONFIG_DYNAMIC_FTRACE
 77 static struct orc_entry *orc_find(unsigned long ip);
 78 
 79 /*
 80  * Ftrace dynamic trampolines do not have orc entries of their own.
 81  * But they are copies of the ftrace entries that are static and
 82  * defined in ftrace_*.S, which do have orc entries.
 83  *
 84  * If the undwinder comes across a ftrace trampoline, then find the
 85  * ftrace function that was used to create it, and use that ftrace
 86  * function's orc entrie, as the placement of the return code in
 87  * the stack will be identical.
 88  */
 89 static struct orc_entry *orc_ftrace_find(unsigned long ip)
 90 {
 91         struct ftrace_ops *ops;
 92         unsigned long caller;
 93 
 94         ops = ftrace_ops_trampoline(ip);
 95         if (!ops)
 96                 return NULL;
 97 
 98         if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
 99                 caller = (unsigned long)ftrace_regs_call;
100         else
101                 caller = (unsigned long)ftrace_call;
102 
103         /* Prevent unlikely recursion */
104         if (ip == caller)
105                 return NULL;
106 
107         return orc_find(caller);
108 }
109 #else
110 static struct orc_entry *orc_ftrace_find(unsigned long ip)
111 {
112         return NULL;
113 }
114 #endif
115 
116 /*
117  * If we crash with IP==0, the last successfully executed instruction
118  * was probably an indirect function call with a NULL function pointer,
119  * and we don't have unwind information for NULL.
120  * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function
121  * pointer into its parent and then continue normally from there.
122  */
123 static struct orc_entry null_orc_entry = {
124         .sp_offset = sizeof(long),
125         .sp_reg = ORC_REG_SP,
126         .bp_reg = ORC_REG_UNDEFINED,
127         .type = ORC_TYPE_CALL
128 };
129 
130 static struct orc_entry *orc_find(unsigned long ip)
131 {
132         static struct orc_entry *orc;
133 
134         if (!orc_init)
135                 return NULL;
136 
137         if (ip == 0)
138                 return &null_orc_entry;
139 
140         /* For non-init vmlinux addresses, use the fast lookup table: */
141         if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
142                 unsigned int idx, start, stop;
143 
144                 idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;
145 
146                 if (unlikely((idx >= lookup_num_blocks-1))) {
147                         orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n",
148                                  idx, lookup_num_blocks, (void *)ip);
149                         return NULL;
150                 }
151 
152                 start = orc_lookup[idx];
153                 stop = orc_lookup[idx + 1] + 1;
154 
155                 if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
156                              (__start_orc_unwind + stop > __stop_orc_unwind))) {
157                         orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n",
158                                  idx, lookup_num_blocks, start, stop, (void *)ip);
159                         return NULL;
160                 }
161 
162                 return __orc_find(__start_orc_unwind_ip + start,
163                                   __start_orc_unwind + start, stop - start, ip);
164         }
165 
166         /* vmlinux .init slow lookup: */
167         if (init_kernel_text(ip))
168                 return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
169                                   __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);
170 
171         /* Module lookup: */
172         orc = orc_module_find(ip);
173         if (orc)
174                 return orc;
175 
176         return orc_ftrace_find(ip);
177 }
178 
179 static void orc_sort_swap(void *_a, void *_b, int size)
180 {
181         struct orc_entry *orc_a, *orc_b;
182         struct orc_entry orc_tmp;
183         int *a = _a, *b = _b, tmp;
184         int delta = _b - _a;
185 
186         /* Swap the .orc_unwind_ip entries: */
187         tmp = *a;
188         *a = *b + delta;
189         *b = tmp - delta;
190 
191         /* Swap the corresponding .orc_unwind entries: */
192         orc_a = cur_orc_table + (a - cur_orc_ip_table);
193         orc_b = cur_orc_table + (b - cur_orc_ip_table);
194         orc_tmp = *orc_a;
195         *orc_a = *orc_b;
196         *orc_b = orc_tmp;
197 }
198 
199 static int orc_sort_cmp(const void *_a, const void *_b)
200 {
201         struct orc_entry *orc_a;
202         const int *a = _a, *b = _b;
203         unsigned long a_val = orc_ip(a);
204         unsigned long b_val = orc_ip(b);
205 
206         if (a_val > b_val)
207                 return 1;
208         if (a_val < b_val)
209                 return -1;
210 
211         /*
212          * The "weak" section terminator entries need to always be on the left
213          * to ensure the lookup code skips them in favor of real entries.
214          * These terminator entries exist to handle any gaps created by
215          * whitelisted .o files which didn't get objtool generation.
216          */
217         orc_a = cur_orc_table + (a - cur_orc_ip_table);
218         return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
219 }
220 
221 #ifdef CONFIG_MODULES
222 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
223                         void *_orc, size_t orc_size)
224 {
225         int *orc_ip = _orc_ip;
226         struct orc_entry *orc = _orc;
227         unsigned int num_entries = orc_ip_size / sizeof(int);
228 
229         WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
230                      orc_size % sizeof(*orc) != 0 ||
231                      num_entries != orc_size / sizeof(*orc));
232 
233         /*
234          * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
235          * associate an .orc_unwind_ip table entry with its corresponding
236          * .orc_unwind entry so they can both be swapped.
237          */
238         mutex_lock(&sort_mutex);
239         cur_orc_ip_table = orc_ip;
240         cur_orc_table = orc;
241         sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
242         mutex_unlock(&sort_mutex);
243 
244         mod->arch.orc_unwind_ip = orc_ip;
245         mod->arch.orc_unwind = orc;
246         mod->arch.num_orcs = num_entries;
247 }
248 #endif
249 
250 void __init unwind_init(void)
251 {
252         size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
253         size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
254         size_t num_entries = orc_ip_size / sizeof(int);
255         struct orc_entry *orc;
256         int i;
257 
258         if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
259             orc_size % sizeof(struct orc_entry) != 0 ||
260             num_entries != orc_size / sizeof(struct orc_entry)) {
261                 orc_warn("WARNING: Bad or missing .orc_unwind table.  Disabling unwinder.\n");
262                 return;
263         }
264 
265         /* Sort the .orc_unwind and .orc_unwind_ip tables: */
266         sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp,
267              orc_sort_swap);
268 
269         /* Initialize the fast lookup table: */
270         lookup_num_blocks = orc_lookup_end - orc_lookup;
271         for (i = 0; i < lookup_num_blocks-1; i++) {
272                 orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
273                                  num_entries,
274                                  LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
275                 if (!orc) {
276                         orc_warn("WARNING: Corrupt .orc_unwind table.  Disabling unwinder.\n");
277                         return;
278                 }
279 
280                 orc_lookup[i] = orc - __start_orc_unwind;
281         }
282 
283         /* Initialize the ending block: */
284         orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries,
285                          LOOKUP_STOP_IP);
286         if (!orc) {
287                 orc_warn("WARNING: Corrupt .orc_unwind table.  Disabling unwinder.\n");
288                 return;
289         }
290         orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;
291 
292         orc_init = true;
293 }
294 
295 unsigned long unwind_get_return_address(struct unwind_state *state)
296 {
297         if (unwind_done(state))
298                 return 0;
299 
300         return __kernel_text_address(state->ip) ? state->ip : 0;
301 }
302 EXPORT_SYMBOL_GPL(unwind_get_return_address);
303 
304 unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
305 {
306         if (unwind_done(state))
307                 return NULL;
308 
309         if (state->regs)
310                 return &state->regs->ip;
311 
312         if (state->sp)
313                 return (unsigned long *)state->sp - 1;
314 
315         return NULL;
316 }
317 
318 static bool stack_access_ok(struct unwind_state *state, unsigned long _addr,
319                             size_t len)
320 {
321         struct stack_info *info = &state->stack_info;
322         void *addr = (void *)_addr;
323 
324         if (!on_stack(info, addr, len) &&
325             (get_stack_info(addr, state->task, info, &state->stack_mask)))
326                 return false;
327 
328         return true;
329 }
330 
331 static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
332                             unsigned long *val)
333 {
334         if (!stack_access_ok(state, addr, sizeof(long)))
335                 return false;
336 
337         *val = READ_ONCE_NOCHECK(*(unsigned long *)addr);
338         return true;
339 }
340 
341 static bool deref_stack_regs(struct unwind_state *state, unsigned long addr,
342                              unsigned long *ip, unsigned long *sp)
343 {
344         struct pt_regs *regs = (struct pt_regs *)addr;
345 
346         /* x86-32 support will be more complicated due to the &regs->sp hack */
347         BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_32));
348 
349         if (!stack_access_ok(state, addr, sizeof(struct pt_regs)))
350                 return false;
351 
352         *ip = regs->ip;
353         *sp = regs->sp;
354         return true;
355 }
356 
357 static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr,
358                                   unsigned long *ip, unsigned long *sp)
359 {
360         struct pt_regs *regs = (void *)addr - IRET_FRAME_OFFSET;
361 
362         if (!stack_access_ok(state, addr, IRET_FRAME_SIZE))
363                 return false;
364 
365         *ip = regs->ip;
366         *sp = regs->sp;
367         return true;
368 }
369 
370 bool unwind_next_frame(struct unwind_state *state)
371 {
372         unsigned long ip_p, sp, orig_ip = state->ip, prev_sp = state->sp;
373         enum stack_type prev_type = state->stack_info.type;
374         struct orc_entry *orc;
375         bool indirect = false;
376 
377         if (unwind_done(state))
378                 return false;
379 
380         /* Don't let modules unload while we're reading their ORC data. */
381         preempt_disable();
382 
383         /* End-of-stack check for user tasks: */
384         if (state->regs && user_mode(state->regs))
385                 goto the_end;
386 
387         /*
388          * Find the orc_entry associated with the text address.
389          *
390          * Decrement call return addresses by one so they work for sibling
391          * calls and calls to noreturn functions.
392          */
393         orc = orc_find(state->signal ? state->ip : state->ip - 1);
394         if (!orc)
395                 goto err;
396 
397         /* End-of-stack check for kernel threads: */
398         if (orc->sp_reg == ORC_REG_UNDEFINED) {
399                 if (!orc->end)
400                         goto err;
401 
402                 goto the_end;
403         }
404 
405         /* Find the previous frame's stack: */
406         switch (orc->sp_reg) {
407         case ORC_REG_SP:
408                 sp = state->sp + orc->sp_offset;
409                 break;
410 
411         case ORC_REG_BP:
412                 sp = state->bp + orc->sp_offset;
413                 break;
414 
415         case ORC_REG_SP_INDIRECT:
416                 sp = state->sp + orc->sp_offset;
417                 indirect = true;
418                 break;
419 
420         case ORC_REG_BP_INDIRECT:
421                 sp = state->bp + orc->sp_offset;
422                 indirect = true;
423                 break;
424 
425         case ORC_REG_R10:
426                 if (!state->regs || !state->full_regs) {
427                         orc_warn("missing regs for base reg R10 at ip %pB\n",
428                                  (void *)state->ip);
429                         goto err;
430                 }
431                 sp = state->regs->r10;
432                 break;
433 
434         case ORC_REG_R13:
435                 if (!state->regs || !state->full_regs) {
436                         orc_warn("missing regs for base reg R13 at ip %pB\n",
437                                  (void *)state->ip);
438                         goto err;
439                 }
440                 sp = state->regs->r13;
441                 break;
442 
443         case ORC_REG_DI:
444                 if (!state->regs || !state->full_regs) {
445                         orc_warn("missing regs for base reg DI at ip %pB\n",
446                                  (void *)state->ip);
447                         goto err;
448                 }
449                 sp = state->regs->di;
450                 break;
451 
452         case ORC_REG_DX:
453                 if (!state->regs || !state->full_regs) {
454                         orc_warn("missing regs for base reg DX at ip %pB\n",
455                                  (void *)state->ip);
456                         goto err;
457                 }
458                 sp = state->regs->dx;
459                 break;
460 
461         default:
462                 orc_warn("unknown SP base reg %d for ip %pB\n",
463                          orc->sp_reg, (void *)state->ip);
464                 goto err;
465         }
466 
467         if (indirect) {
468                 if (!deref_stack_reg(state, sp, &sp))
469                         goto err;
470         }
471 
472         /* Find IP, SP and possibly regs: */
473         switch (orc->type) {
474         case ORC_TYPE_CALL:
475                 ip_p = sp - sizeof(long);
476 
477                 if (!deref_stack_reg(state, ip_p, &state->ip))
478                         goto err;
479 
480                 state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
481                                                   state->ip, (void *)ip_p);
482 
483                 state->sp = sp;
484                 state->regs = NULL;
485                 state->signal = false;
486                 break;
487 
488         case ORC_TYPE_REGS:
489                 if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
490                         orc_warn("can't dereference registers at %p for ip %pB\n",
491                                  (void *)sp, (void *)orig_ip);
492                         goto err;
493                 }
494 
495                 state->regs = (struct pt_regs *)sp;
496                 state->full_regs = true;
497                 state->signal = true;
498                 break;
499 
500         case ORC_TYPE_REGS_IRET:
501                 if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
502                         orc_warn("can't dereference iret registers at %p for ip %pB\n",
503                                  (void *)sp, (void *)orig_ip);
504                         goto err;
505                 }
506 
507                 state->regs = (void *)sp - IRET_FRAME_OFFSET;
508                 state->full_regs = false;
509                 state->signal = true;
510                 break;
511 
512         default:
513                 orc_warn("unknown .orc_unwind entry type %d for ip %pB\n",
514                          orc->type, (void *)orig_ip);
515                 break;
516         }
517 
518         /* Find BP: */
519         switch (orc->bp_reg) {
520         case ORC_REG_UNDEFINED:
521                 if (state->regs && state->full_regs)
522                         state->bp = state->regs->bp;
523                 break;
524 
525         case ORC_REG_PREV_SP:
526                 if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))
527                         goto err;
528                 break;
529 
530         case ORC_REG_BP:
531                 if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))
532                         goto err;
533                 break;
534 
535         default:
536                 orc_warn("unknown BP base reg %d for ip %pB\n",
537                          orc->bp_reg, (void *)orig_ip);
538                 goto err;
539         }
540 
541         /* Prevent a recursive loop due to bad ORC data: */
542         if (state->stack_info.type == prev_type &&
543             on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
544             state->sp <= prev_sp) {
545                 orc_warn("stack going in the wrong direction? ip=%pB\n",
546                          (void *)orig_ip);
547                 goto err;
548         }
549 
550         preempt_enable();
551         return true;
552 
553 err:
554         state->error = true;
555 
556 the_end:
557         preempt_enable();
558         state->stack_info.type = STACK_TYPE_UNKNOWN;
559         return false;
560 }
561 EXPORT_SYMBOL_GPL(unwind_next_frame);
562 
563 void __unwind_start(struct unwind_state *state, struct task_struct *task,
564                     struct pt_regs *regs, unsigned long *first_frame)
565 {
566         memset(state, 0, sizeof(*state));
567         state->task = task;
568 
569         /*
570          * Refuse to unwind the stack of a task while it's executing on another
571          * CPU.  This check is racy, but that's ok: the unwinder has other
572          * checks to prevent it from going off the rails.
573          */
574         if (task_on_another_cpu(task))
575                 goto done;
576 
577         if (regs) {
578                 if (user_mode(regs))
579                         goto done;
580 
581                 state->ip = regs->ip;
582                 state->sp = kernel_stack_pointer(regs);
583                 state->bp = regs->bp;
584                 state->regs = regs;
585                 state->full_regs = true;
586                 state->signal = true;
587 
588         } else if (task == current) {
589                 asm volatile("lea (%%rip), %0\n\t"
590                              "mov %%rsp, %1\n\t"
591                              "mov %%rbp, %2\n\t"
592                              : "=r" (state->ip), "=r" (state->sp),
593                                "=r" (state->bp));
594 
595         } else {
596                 struct inactive_task_frame *frame = (void *)task->thread.sp;
597 
598                 state->sp = task->thread.sp;
599                 state->bp = READ_ONCE_NOCHECK(frame->bp);
600                 state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
601         }
602 
603         if (get_stack_info((unsigned long *)state->sp, state->task,
604                            &state->stack_info, &state->stack_mask)) {
605                 /*
606                  * We weren't on a valid stack.  It's possible that
607                  * we overflowed a valid stack into a guard page.
608                  * See if the next page up is valid so that we can
609                  * generate some kind of backtrace if this happens.
610                  */
611                 void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
612                 if (get_stack_info(next_page, state->task, &state->stack_info,
613                                    &state->stack_mask))
614                         return;
615         }
616 
617         /*
618          * The caller can provide the address of the first frame directly
619          * (first_frame) or indirectly (regs->sp) to indicate which stack frame
620          * to start unwinding at.  Skip ahead until we reach it.
621          */
622 
623         /* When starting from regs, skip the regs frame: */
624         if (regs) {
625                 unwind_next_frame(state);
626                 return;
627         }
628 
629         /* Otherwise, skip ahead to the user-specified starting frame: */
630         while (!unwind_done(state) &&
631                (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
632                         state->sp <= (unsigned long)first_frame))
633                 unwind_next_frame(state);
634 
635         return;
636 
637 done:
638         state->stack_info.type = STACK_TYPE_UNKNOWN;
639         return;
640 }
641 EXPORT_SYMBOL_GPL(__unwind_start);
642 

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