1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright (C) IBM Corporation, 2002, 2004
6 *
7 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
8 * Probes initial implementation (includes suggestions from
9 * Rusty Russell).
10 * 2004-Aug Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
11 * hlists and exceptions notifier as suggested by Andi Kleen.
12 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
13 * interface to access function arguments.
14 * 2004-Sep Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
15 * exceptions notifier to be first on the priority list.
16 * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
17 * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
18 * <prasanna@in.ibm.com> added function-return probes.
19 */
20
21 #define pr_fmt(fmt) "kprobes: " fmt
22
23 #include <linux/kprobes.h>
24 #include <linux/hash.h>
25 #include <linux/init.h>
26 #include <linux/slab.h>
27 #include <linux/stddef.h>
28 #include <linux/export.h>
29 #include <linux/moduleloader.h>
30 #include <linux/kallsyms.h>
31 #include <linux/freezer.h>
32 #include <linux/seq_file.h>
33 #include <linux/debugfs.h>
34 #include <linux/sysctl.h>
35 #include <linux/kdebug.h>
36 #include <linux/memory.h>
37 #include <linux/ftrace.h>
38 #include <linux/cpu.h>
39 #include <linux/jump_label.h>
40 #include <linux/static_call.h>
41 #include <linux/perf_event.h>
42
43 #include <asm/sections.h>
44 #include <asm/cacheflush.h>
45 #include <asm/errno.h>
46 #include <linux/uaccess.h>
47
48 #define KPROBE_HASH_BITS 6
49 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
50
51 #if !defined(CONFIG_OPTPROBES) || !defined(CONFIG_SYSCTL)
52 #define kprobe_sysctls_init() do { } while (0)
53 #endif
54
55 static int kprobes_initialized;
56 /* kprobe_table can be accessed by
57 * - Normal hlist traversal and RCU add/del under 'kprobe_mutex' is held.
58 * Or
59 * - RCU hlist traversal under disabling preempt (breakpoint handlers)
60 */
61 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
62
63 /* NOTE: change this value only with 'kprobe_mutex' held */
64 static bool kprobes_all_disarmed;
65
66 /* This protects 'kprobe_table' and 'optimizing_list' */
67 static DEFINE_MUTEX(kprobe_mutex);
68 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance);
69
kprobe_lookup_name(const char * name,unsigned int __unused)70 kprobe_opcode_t * __weak kprobe_lookup_name(const char *name,
71 unsigned int __unused)
72 {
73 return ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
74 }
75
76 /*
77 * Blacklist -- list of 'struct kprobe_blacklist_entry' to store info where
78 * kprobes can not probe.
79 */
80 static LIST_HEAD(kprobe_blacklist);
81
82 #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
83 /*
84 * 'kprobe::ainsn.insn' points to the copy of the instruction to be
85 * single-stepped. x86_64, POWER4 and above have no-exec support and
86 * stepping on the instruction on a vmalloced/kmalloced/data page
87 * is a recipe for disaster
88 */
89 struct kprobe_insn_page {
90 struct list_head list;
91 kprobe_opcode_t *insns; /* Page of instruction slots */
92 struct kprobe_insn_cache *cache;
93 int nused;
94 int ngarbage;
95 char slot_used[];
96 };
97
98 #define KPROBE_INSN_PAGE_SIZE(slots) \
99 (offsetof(struct kprobe_insn_page, slot_used) + \
100 (sizeof(char) * (slots)))
101
slots_per_page(struct kprobe_insn_cache * c)102 static int slots_per_page(struct kprobe_insn_cache *c)
103 {
104 return PAGE_SIZE/(c->insn_size * sizeof(kprobe_opcode_t));
105 }
106
107 enum kprobe_slot_state {
108 SLOT_CLEAN = 0,
109 SLOT_DIRTY = 1,
110 SLOT_USED = 2,
111 };
112
alloc_insn_page(void)113 void __weak *alloc_insn_page(void)
114 {
115 /*
116 * Use module_alloc() so this page is within +/- 2GB of where the
117 * kernel image and loaded module images reside. This is required
118 * for most of the architectures.
119 * (e.g. x86-64 needs this to handle the %rip-relative fixups.)
120 */
121 return module_alloc(PAGE_SIZE);
122 }
123
free_insn_page(void * page)124 static void free_insn_page(void *page)
125 {
126 module_memfree(page);
127 }
128
129 struct kprobe_insn_cache kprobe_insn_slots = {
130 .mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex),
131 .alloc = alloc_insn_page,
132 .free = free_insn_page,
133 .sym = KPROBE_INSN_PAGE_SYM,
134 .pages = LIST_HEAD_INIT(kprobe_insn_slots.pages),
135 .insn_size = MAX_INSN_SIZE,
136 .nr_garbage = 0,
137 };
138 static int collect_garbage_slots(struct kprobe_insn_cache *c);
139
140 /**
141 * __get_insn_slot() - Find a slot on an executable page for an instruction.
142 * We allocate an executable page if there's no room on existing ones.
143 */
__get_insn_slot(struct kprobe_insn_cache * c)144 kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
145 {
146 struct kprobe_insn_page *kip;
147 kprobe_opcode_t *slot = NULL;
148
149 /* Since the slot array is not protected by rcu, we need a mutex */
150 mutex_lock(&c->mutex);
151 retry:
152 rcu_read_lock();
153 list_for_each_entry_rcu(kip, &c->pages, list) {
154 if (kip->nused < slots_per_page(c)) {
155 int i;
156
157 for (i = 0; i < slots_per_page(c); i++) {
158 if (kip->slot_used[i] == SLOT_CLEAN) {
159 kip->slot_used[i] = SLOT_USED;
160 kip->nused++;
161 slot = kip->insns + (i * c->insn_size);
162 rcu_read_unlock();
163 goto out;
164 }
165 }
166 /* kip->nused is broken. Fix it. */
167 kip->nused = slots_per_page(c);
168 WARN_ON(1);
169 }
170 }
171 rcu_read_unlock();
172
173 /* If there are any garbage slots, collect it and try again. */
174 if (c->nr_garbage && collect_garbage_slots(c) == 0)
175 goto retry;
176
177 /* All out of space. Need to allocate a new page. */
178 kip = kmalloc(KPROBE_INSN_PAGE_SIZE(slots_per_page(c)), GFP_KERNEL);
179 if (!kip)
180 goto out;
181
182 kip->insns = c->alloc();
183 if (!kip->insns) {
184 kfree(kip);
185 goto out;
186 }
187 INIT_LIST_HEAD(&kip->list);
188 memset(kip->slot_used, SLOT_CLEAN, slots_per_page(c));
189 kip->slot_used[0] = SLOT_USED;
190 kip->nused = 1;
191 kip->ngarbage = 0;
192 kip->cache = c;
193 list_add_rcu(&kip->list, &c->pages);
194 slot = kip->insns;
195
196 /* Record the perf ksymbol register event after adding the page */
197 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL, (unsigned long)kip->insns,
198 PAGE_SIZE, false, c->sym);
199 out:
200 mutex_unlock(&c->mutex);
201 return slot;
202 }
203
204 /* Return true if all garbages are collected, otherwise false. */
collect_one_slot(struct kprobe_insn_page * kip,int idx)205 static bool collect_one_slot(struct kprobe_insn_page *kip, int idx)
206 {
207 kip->slot_used[idx] = SLOT_CLEAN;
208 kip->nused--;
209 if (kip->nused == 0) {
210 /*
211 * Page is no longer in use. Free it unless
212 * it's the last one. We keep the last one
213 * so as not to have to set it up again the
214 * next time somebody inserts a probe.
215 */
216 if (!list_is_singular(&kip->list)) {
217 /*
218 * Record perf ksymbol unregister event before removing
219 * the page.
220 */
221 perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL,
222 (unsigned long)kip->insns, PAGE_SIZE, true,
223 kip->cache->sym);
224 list_del_rcu(&kip->list);
225 synchronize_rcu();
226 kip->cache->free(kip->insns);
227 kfree(kip);
228 }
229 return true;
230 }
231 return false;
232 }
233
collect_garbage_slots(struct kprobe_insn_cache * c)234 static int collect_garbage_slots(struct kprobe_insn_cache *c)
235 {
236 struct kprobe_insn_page *kip, *next;
237
238 /* Ensure no-one is interrupted on the garbages */
239 synchronize_rcu();
240
241 list_for_each_entry_safe(kip, next, &c->pages, list) {
242 int i;
243
244 if (kip->ngarbage == 0)
245 continue;
246 kip->ngarbage = 0; /* we will collect all garbages */
247 for (i = 0; i < slots_per_page(c); i++) {
248 if (kip->slot_used[i] == SLOT_DIRTY && collect_one_slot(kip, i))
249 break;
250 }
251 }
252 c->nr_garbage = 0;
253 return 0;
254 }
255
__free_insn_slot(struct kprobe_insn_cache * c,kprobe_opcode_t * slot,int dirty)256 void __free_insn_slot(struct kprobe_insn_cache *c,
257 kprobe_opcode_t *slot, int dirty)
258 {
259 struct kprobe_insn_page *kip;
260 long idx;
261
262 mutex_lock(&c->mutex);
263 rcu_read_lock();
264 list_for_each_entry_rcu(kip, &c->pages, list) {
265 idx = ((long)slot - (long)kip->insns) /
266 (c->insn_size * sizeof(kprobe_opcode_t));
267 if (idx >= 0 && idx < slots_per_page(c))
268 goto out;
269 }
270 /* Could not find this slot. */
271 WARN_ON(1);
272 kip = NULL;
273 out:
274 rcu_read_unlock();
275 /* Mark and sweep: this may sleep */
276 if (kip) {
277 /* Check double free */
278 WARN_ON(kip->slot_used[idx] != SLOT_USED);
279 if (dirty) {
280 kip->slot_used[idx] = SLOT_DIRTY;
281 kip->ngarbage++;
282 if (++c->nr_garbage > slots_per_page(c))
283 collect_garbage_slots(c);
284 } else {
285 collect_one_slot(kip, idx);
286 }
287 }
288 mutex_unlock(&c->mutex);
289 }
290
291 /*
292 * Check given address is on the page of kprobe instruction slots.
293 * This will be used for checking whether the address on a stack
294 * is on a text area or not.
295 */
__is_insn_slot_addr(struct kprobe_insn_cache * c,unsigned long addr)296 bool __is_insn_slot_addr(struct kprobe_insn_cache *c, unsigned long addr)
297 {
298 struct kprobe_insn_page *kip;
299 bool ret = false;
300
301 rcu_read_lock();
302 list_for_each_entry_rcu(kip, &c->pages, list) {
303 if (addr >= (unsigned long)kip->insns &&
304 addr < (unsigned long)kip->insns + PAGE_SIZE) {
305 ret = true;
306 break;
307 }
308 }
309 rcu_read_unlock();
310
311 return ret;
312 }
313
kprobe_cache_get_kallsym(struct kprobe_insn_cache * c,unsigned int * symnum,unsigned long * value,char * type,char * sym)314 int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int *symnum,
315 unsigned long *value, char *type, char *sym)
316 {
317 struct kprobe_insn_page *kip;
318 int ret = -ERANGE;
319
320 rcu_read_lock();
321 list_for_each_entry_rcu(kip, &c->pages, list) {
322 if ((*symnum)--)
323 continue;
324 strscpy(sym, c->sym, KSYM_NAME_LEN);
325 *type = 't';
326 *value = (unsigned long)kip->insns;
327 ret = 0;
328 break;
329 }
330 rcu_read_unlock();
331
332 return ret;
333 }
334
335 #ifdef CONFIG_OPTPROBES
alloc_optinsn_page(void)336 void __weak *alloc_optinsn_page(void)
337 {
338 return alloc_insn_page();
339 }
340
free_optinsn_page(void * page)341 void __weak free_optinsn_page(void *page)
342 {
343 free_insn_page(page);
344 }
345
346 /* For optimized_kprobe buffer */
347 struct kprobe_insn_cache kprobe_optinsn_slots = {
348 .mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
349 .alloc = alloc_optinsn_page,
350 .free = free_optinsn_page,
351 .sym = KPROBE_OPTINSN_PAGE_SYM,
352 .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
353 /* .insn_size is initialized later */
354 .nr_garbage = 0,
355 };
356 #endif
357 #endif
358
359 /* We have preemption disabled.. so it is safe to use __ versions */
set_kprobe_instance(struct kprobe * kp)360 static inline void set_kprobe_instance(struct kprobe *kp)
361 {
362 __this_cpu_write(kprobe_instance, kp);
363 }
364
reset_kprobe_instance(void)365 static inline void reset_kprobe_instance(void)
366 {
367 __this_cpu_write(kprobe_instance, NULL);
368 }
369
370 /*
371 * This routine is called either:
372 * - under the 'kprobe_mutex' - during kprobe_[un]register().
373 * OR
374 * - with preemption disabled - from architecture specific code.
375 */
get_kprobe(void * addr)376 struct kprobe *get_kprobe(void *addr)
377 {
378 struct hlist_head *head;
379 struct kprobe *p;
380
381 head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
382 hlist_for_each_entry_rcu(p, head, hlist,
383 lockdep_is_held(&kprobe_mutex)) {
384 if (p->addr == addr)
385 return p;
386 }
387
388 return NULL;
389 }
390 NOKPROBE_SYMBOL(get_kprobe);
391
392 static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs);
393
394 /* Return true if 'p' is an aggregator */
kprobe_aggrprobe(struct kprobe * p)395 static inline bool kprobe_aggrprobe(struct kprobe *p)
396 {
397 return p->pre_handler == aggr_pre_handler;
398 }
399
400 /* Return true if 'p' is unused */
kprobe_unused(struct kprobe * p)401 static inline bool kprobe_unused(struct kprobe *p)
402 {
403 return kprobe_aggrprobe(p) && kprobe_disabled(p) &&
404 list_empty(&p->list);
405 }
406
407 /* Keep all fields in the kprobe consistent. */
copy_kprobe(struct kprobe * ap,struct kprobe * p)408 static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p)
409 {
410 memcpy(&p->opcode, &ap->opcode, sizeof(kprobe_opcode_t));
411 memcpy(&p->ainsn, &ap->ainsn, sizeof(struct arch_specific_insn));
412 }
413
414 #ifdef CONFIG_OPTPROBES
415 /* NOTE: This is protected by 'kprobe_mutex'. */
416 static bool kprobes_allow_optimization;
417
418 /*
419 * Call all 'kprobe::pre_handler' on the list, but ignores its return value.
420 * This must be called from arch-dep optimized caller.
421 */
opt_pre_handler(struct kprobe * p,struct pt_regs * regs)422 void opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
423 {
424 struct kprobe *kp;
425
426 list_for_each_entry_rcu(kp, &p->list, list) {
427 if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
428 set_kprobe_instance(kp);
429 kp->pre_handler(kp, regs);
430 }
431 reset_kprobe_instance();
432 }
433 }
434 NOKPROBE_SYMBOL(opt_pre_handler);
435
436 /* Free optimized instructions and optimized_kprobe */
free_aggr_kprobe(struct kprobe * p)437 static void free_aggr_kprobe(struct kprobe *p)
438 {
439 struct optimized_kprobe *op;
440
441 op = container_of(p, struct optimized_kprobe, kp);
442 arch_remove_optimized_kprobe(op);
443 arch_remove_kprobe(p);
444 kfree(op);
445 }
446
447 /* Return true if the kprobe is ready for optimization. */
kprobe_optready(struct kprobe * p)448 static inline int kprobe_optready(struct kprobe *p)
449 {
450 struct optimized_kprobe *op;
451
452 if (kprobe_aggrprobe(p)) {
453 op = container_of(p, struct optimized_kprobe, kp);
454 return arch_prepared_optinsn(&op->optinsn);
455 }
456
457 return 0;
458 }
459
460 /* Return true if the kprobe is disarmed. Note: p must be on hash list */
kprobe_disarmed(struct kprobe * p)461 static inline bool kprobe_disarmed(struct kprobe *p)
462 {
463 struct optimized_kprobe *op;
464
465 /* If kprobe is not aggr/opt probe, just return kprobe is disabled */
466 if (!kprobe_aggrprobe(p))
467 return kprobe_disabled(p);
468
469 op = container_of(p, struct optimized_kprobe, kp);
470
471 return kprobe_disabled(p) && list_empty(&op->list);
472 }
473
474 /* Return true if the probe is queued on (un)optimizing lists */
kprobe_queued(struct kprobe * p)475 static bool kprobe_queued(struct kprobe *p)
476 {
477 struct optimized_kprobe *op;
478
479 if (kprobe_aggrprobe(p)) {
480 op = container_of(p, struct optimized_kprobe, kp);
481 if (!list_empty(&op->list))
482 return true;
483 }
484 return false;
485 }
486
487 /*
488 * Return an optimized kprobe whose optimizing code replaces
489 * instructions including 'addr' (exclude breakpoint).
490 */
get_optimized_kprobe(kprobe_opcode_t * addr)491 static struct kprobe *get_optimized_kprobe(kprobe_opcode_t *addr)
492 {
493 int i;
494 struct kprobe *p = NULL;
495 struct optimized_kprobe *op;
496
497 /* Don't check i == 0, since that is a breakpoint case. */
498 for (i = 1; !p && i < MAX_OPTIMIZED_LENGTH / sizeof(kprobe_opcode_t); i++)
499 p = get_kprobe(addr - i);
500
501 if (p && kprobe_optready(p)) {
502 op = container_of(p, struct optimized_kprobe, kp);
503 if (arch_within_optimized_kprobe(op, addr))
504 return p;
505 }
506
507 return NULL;
508 }
509
510 /* Optimization staging list, protected by 'kprobe_mutex' */
511 static LIST_HEAD(optimizing_list);
512 static LIST_HEAD(unoptimizing_list);
513 static LIST_HEAD(freeing_list);
514
515 static void kprobe_optimizer(struct work_struct *work);
516 static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
517 #define OPTIMIZE_DELAY 5
518
519 /*
520 * Optimize (replace a breakpoint with a jump) kprobes listed on
521 * 'optimizing_list'.
522 */
do_optimize_kprobes(void)523 static void do_optimize_kprobes(void)
524 {
525 lockdep_assert_held(&text_mutex);
526 /*
527 * The optimization/unoptimization refers 'online_cpus' via
528 * stop_machine() and cpu-hotplug modifies the 'online_cpus'.
529 * And same time, 'text_mutex' will be held in cpu-hotplug and here.
530 * This combination can cause a deadlock (cpu-hotplug tries to lock
531 * 'text_mutex' but stop_machine() can not be done because
532 * the 'online_cpus' has been changed)
533 * To avoid this deadlock, caller must have locked cpu-hotplug
534 * for preventing cpu-hotplug outside of 'text_mutex' locking.
535 */
536 lockdep_assert_cpus_held();
537
538 /* Optimization never be done when disarmed */
539 if (kprobes_all_disarmed || !kprobes_allow_optimization ||
540 list_empty(&optimizing_list))
541 return;
542
543 arch_optimize_kprobes(&optimizing_list);
544 }
545
546 /*
547 * Unoptimize (replace a jump with a breakpoint and remove the breakpoint
548 * if need) kprobes listed on 'unoptimizing_list'.
549 */
do_unoptimize_kprobes(void)550 static void do_unoptimize_kprobes(void)
551 {
552 struct optimized_kprobe *op, *tmp;
553
554 lockdep_assert_held(&text_mutex);
555 /* See comment in do_optimize_kprobes() */
556 lockdep_assert_cpus_held();
557
558 /* Unoptimization must be done anytime */
559 if (list_empty(&unoptimizing_list))
560 return;
561
562 arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
563 /* Loop on 'freeing_list' for disarming */
564 list_for_each_entry_safe(op, tmp, &freeing_list, list) {
565 /* Switching from detour code to origin */
566 op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
567 /* Disarm probes if marked disabled */
568 if (kprobe_disabled(&op->kp))
569 arch_disarm_kprobe(&op->kp);
570 if (kprobe_unused(&op->kp)) {
571 /*
572 * Remove unused probes from hash list. After waiting
573 * for synchronization, these probes are reclaimed.
574 * (reclaiming is done by do_free_cleaned_kprobes().)
575 */
576 hlist_del_rcu(&op->kp.hlist);
577 } else
578 list_del_init(&op->list);
579 }
580 }
581
582 /* Reclaim all kprobes on the 'freeing_list' */
do_free_cleaned_kprobes(void)583 static void do_free_cleaned_kprobes(void)
584 {
585 struct optimized_kprobe *op, *tmp;
586
587 list_for_each_entry_safe(op, tmp, &freeing_list, list) {
588 list_del_init(&op->list);
589 if (WARN_ON_ONCE(!kprobe_unused(&op->kp))) {
590 /*
591 * This must not happen, but if there is a kprobe
592 * still in use, keep it on kprobes hash list.
593 */
594 continue;
595 }
596 free_aggr_kprobe(&op->kp);
597 }
598 }
599
600 /* Start optimizer after OPTIMIZE_DELAY passed */
kick_kprobe_optimizer(void)601 static void kick_kprobe_optimizer(void)
602 {
603 schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
604 }
605
606 /* Kprobe jump optimizer */
kprobe_optimizer(struct work_struct * work)607 static void kprobe_optimizer(struct work_struct *work)
608 {
609 mutex_lock(&kprobe_mutex);
610 cpus_read_lock();
611 mutex_lock(&text_mutex);
612
613 /*
614 * Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed)
615 * kprobes before waiting for quiesence period.
616 */
617 do_unoptimize_kprobes();
618
619 /*
620 * Step 2: Wait for quiesence period to ensure all potentially
621 * preempted tasks to have normally scheduled. Because optprobe
622 * may modify multiple instructions, there is a chance that Nth
623 * instruction is preempted. In that case, such tasks can return
624 * to 2nd-Nth byte of jump instruction. This wait is for avoiding it.
625 * Note that on non-preemptive kernel, this is transparently converted
626 * to synchronoze_sched() to wait for all interrupts to have completed.
627 */
628 synchronize_rcu_tasks();
629
630 /* Step 3: Optimize kprobes after quiesence period */
631 do_optimize_kprobes();
632
633 /* Step 4: Free cleaned kprobes after quiesence period */
634 do_free_cleaned_kprobes();
635
636 mutex_unlock(&text_mutex);
637 cpus_read_unlock();
638
639 /* Step 5: Kick optimizer again if needed */
640 if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
641 kick_kprobe_optimizer();
642
643 mutex_unlock(&kprobe_mutex);
644 }
645
646 /* Wait for completing optimization and unoptimization */
wait_for_kprobe_optimizer(void)647 void wait_for_kprobe_optimizer(void)
648 {
649 mutex_lock(&kprobe_mutex);
650
651 while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
652 mutex_unlock(&kprobe_mutex);
653
654 /* This will also make 'optimizing_work' execute immmediately */
655 flush_delayed_work(&optimizing_work);
656 /* 'optimizing_work' might not have been queued yet, relax */
657 cpu_relax();
658
659 mutex_lock(&kprobe_mutex);
660 }
661
662 mutex_unlock(&kprobe_mutex);
663 }
664
optprobe_queued_unopt(struct optimized_kprobe * op)665 static bool optprobe_queued_unopt(struct optimized_kprobe *op)
666 {
667 struct optimized_kprobe *_op;
668
669 list_for_each_entry(_op, &unoptimizing_list, list) {
670 if (op == _op)
671 return true;
672 }
673
674 return false;
675 }
676
677 /* Optimize kprobe if p is ready to be optimized */
optimize_kprobe(struct kprobe * p)678 static void optimize_kprobe(struct kprobe *p)
679 {
680 struct optimized_kprobe *op;
681
682 /* Check if the kprobe is disabled or not ready for optimization. */
683 if (!kprobe_optready(p) || !kprobes_allow_optimization ||
684 (kprobe_disabled(p) || kprobes_all_disarmed))
685 return;
686
687 /* kprobes with 'post_handler' can not be optimized */
688 if (p->post_handler)
689 return;
690
691 op = container_of(p, struct optimized_kprobe, kp);
692
693 /* Check there is no other kprobes at the optimized instructions */
694 if (arch_check_optimized_kprobe(op) < 0)
695 return;
696
697 /* Check if it is already optimized. */
698 if (op->kp.flags & KPROBE_FLAG_OPTIMIZED) {
699 if (optprobe_queued_unopt(op)) {
700 /* This is under unoptimizing. Just dequeue the probe */
701 list_del_init(&op->list);
702 }
703 return;
704 }
705 op->kp.flags |= KPROBE_FLAG_OPTIMIZED;
706
707 /*
708 * On the 'unoptimizing_list' and 'optimizing_list',
709 * 'op' must have OPTIMIZED flag
710 */
711 if (WARN_ON_ONCE(!list_empty(&op->list)))
712 return;
713
714 list_add(&op->list, &optimizing_list);
715 kick_kprobe_optimizer();
716 }
717
718 /* Short cut to direct unoptimizing */
force_unoptimize_kprobe(struct optimized_kprobe * op)719 static void force_unoptimize_kprobe(struct optimized_kprobe *op)
720 {
721 lockdep_assert_cpus_held();
722 arch_unoptimize_kprobe(op);
723 op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
724 }
725
726 /* Unoptimize a kprobe if p is optimized */
unoptimize_kprobe(struct kprobe * p,bool force)727 static void unoptimize_kprobe(struct kprobe *p, bool force)
728 {
729 struct optimized_kprobe *op;
730
731 if (!kprobe_aggrprobe(p) || kprobe_disarmed(p))
732 return; /* This is not an optprobe nor optimized */
733
734 op = container_of(p, struct optimized_kprobe, kp);
735 if (!kprobe_optimized(p))
736 return;
737
738 if (!list_empty(&op->list)) {
739 if (optprobe_queued_unopt(op)) {
740 /* Queued in unoptimizing queue */
741 if (force) {
742 /*
743 * Forcibly unoptimize the kprobe here, and queue it
744 * in the freeing list for release afterwards.
745 */
746 force_unoptimize_kprobe(op);
747 list_move(&op->list, &freeing_list);
748 }
749 } else {
750 /* Dequeue from the optimizing queue */
751 list_del_init(&op->list);
752 op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
753 }
754 return;
755 }
756
757 /* Optimized kprobe case */
758 if (force) {
759 /* Forcibly update the code: this is a special case */
760 force_unoptimize_kprobe(op);
761 } else {
762 list_add(&op->list, &unoptimizing_list);
763 kick_kprobe_optimizer();
764 }
765 }
766
767 /* Cancel unoptimizing for reusing */
reuse_unused_kprobe(struct kprobe * ap)768 static int reuse_unused_kprobe(struct kprobe *ap)
769 {
770 struct optimized_kprobe *op;
771
772 /*
773 * Unused kprobe MUST be on the way of delayed unoptimizing (means
774 * there is still a relative jump) and disabled.
775 */
776 op = container_of(ap, struct optimized_kprobe, kp);
777 WARN_ON_ONCE(list_empty(&op->list));
778 /* Enable the probe again */
779 ap->flags &= ~KPROBE_FLAG_DISABLED;
780 /* Optimize it again. (remove from 'op->list') */
781 if (!kprobe_optready(ap))
782 return -EINVAL;
783
784 optimize_kprobe(ap);
785 return 0;
786 }
787
788 /* Remove optimized instructions */
kill_optimized_kprobe(struct kprobe * p)789 static void kill_optimized_kprobe(struct kprobe *p)
790 {
791 struct optimized_kprobe *op;
792
793 op = container_of(p, struct optimized_kprobe, kp);
794 if (!list_empty(&op->list))
795 /* Dequeue from the (un)optimization queue */
796 list_del_init(&op->list);
797 op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
798
799 if (kprobe_unused(p)) {
800 /* Enqueue if it is unused */
801 list_add(&op->list, &freeing_list);
802 /*
803 * Remove unused probes from the hash list. After waiting
804 * for synchronization, this probe is reclaimed.
805 * (reclaiming is done by do_free_cleaned_kprobes().)
806 */
807 hlist_del_rcu(&op->kp.hlist);
808 }
809
810 /* Don't touch the code, because it is already freed. */
811 arch_remove_optimized_kprobe(op);
812 }
813
814 static inline
__prepare_optimized_kprobe(struct optimized_kprobe * op,struct kprobe * p)815 void __prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
816 {
817 if (!kprobe_ftrace(p))
818 arch_prepare_optimized_kprobe(op, p);
819 }
820
821 /* Try to prepare optimized instructions */
prepare_optimized_kprobe(struct kprobe * p)822 static void prepare_optimized_kprobe(struct kprobe *p)
823 {
824 struct optimized_kprobe *op;
825
826 op = container_of(p, struct optimized_kprobe, kp);
827 __prepare_optimized_kprobe(op, p);
828 }
829
830 /* Allocate new optimized_kprobe and try to prepare optimized instructions. */
alloc_aggr_kprobe(struct kprobe * p)831 static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
832 {
833 struct optimized_kprobe *op;
834
835 op = kzalloc(sizeof(struct optimized_kprobe), GFP_KERNEL);
836 if (!op)
837 return NULL;
838
839 INIT_LIST_HEAD(&op->list);
840 op->kp.addr = p->addr;
841 __prepare_optimized_kprobe(op, p);
842
843 return &op->kp;
844 }
845
846 static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p);
847
848 /*
849 * Prepare an optimized_kprobe and optimize it.
850 * NOTE: 'p' must be a normal registered kprobe.
851 */
try_to_optimize_kprobe(struct kprobe * p)852 static void try_to_optimize_kprobe(struct kprobe *p)
853 {
854 struct kprobe *ap;
855 struct optimized_kprobe *op;
856
857 /* Impossible to optimize ftrace-based kprobe. */
858 if (kprobe_ftrace(p))
859 return;
860
861 /* For preparing optimization, jump_label_text_reserved() is called. */
862 cpus_read_lock();
863 jump_label_lock();
864 mutex_lock(&text_mutex);
865
866 ap = alloc_aggr_kprobe(p);
867 if (!ap)
868 goto out;
869
870 op = container_of(ap, struct optimized_kprobe, kp);
871 if (!arch_prepared_optinsn(&op->optinsn)) {
872 /* If failed to setup optimizing, fallback to kprobe. */
873 arch_remove_optimized_kprobe(op);
874 kfree(op);
875 goto out;
876 }
877
878 init_aggr_kprobe(ap, p);
879 optimize_kprobe(ap); /* This just kicks optimizer thread. */
880
881 out:
882 mutex_unlock(&text_mutex);
883 jump_label_unlock();
884 cpus_read_unlock();
885 }
886
optimize_all_kprobes(void)887 static void optimize_all_kprobes(void)
888 {
889 struct hlist_head *head;
890 struct kprobe *p;
891 unsigned int i;
892
893 mutex_lock(&kprobe_mutex);
894 /* If optimization is already allowed, just return. */
895 if (kprobes_allow_optimization)
896 goto out;
897
898 cpus_read_lock();
899 kprobes_allow_optimization = true;
900 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
901 head = &kprobe_table[i];
902 hlist_for_each_entry(p, head, hlist)
903 if (!kprobe_disabled(p))
904 optimize_kprobe(p);
905 }
906 cpus_read_unlock();
907 pr_info("kprobe jump-optimization is enabled. All kprobes are optimized if possible.\n");
908 out:
909 mutex_unlock(&kprobe_mutex);
910 }
911
912 #ifdef CONFIG_SYSCTL
unoptimize_all_kprobes(void)913 static void unoptimize_all_kprobes(void)
914 {
915 struct hlist_head *head;
916 struct kprobe *p;
917 unsigned int i;
918
919 mutex_lock(&kprobe_mutex);
920 /* If optimization is already prohibited, just return. */
921 if (!kprobes_allow_optimization) {
922 mutex_unlock(&kprobe_mutex);
923 return;
924 }
925
926 cpus_read_lock();
927 kprobes_allow_optimization = false;
928 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
929 head = &kprobe_table[i];
930 hlist_for_each_entry(p, head, hlist) {
931 if (!kprobe_disabled(p))
932 unoptimize_kprobe(p, false);
933 }
934 }
935 cpus_read_unlock();
936 mutex_unlock(&kprobe_mutex);
937
938 /* Wait for unoptimizing completion. */
939 wait_for_kprobe_optimizer();
940 pr_info("kprobe jump-optimization is disabled. All kprobes are based on software breakpoint.\n");
941 }
942
943 static DEFINE_MUTEX(kprobe_sysctl_mutex);
944 static int sysctl_kprobes_optimization;
proc_kprobes_optimization_handler(struct ctl_table * table,int write,void * buffer,size_t * length,loff_t * ppos)945 static int proc_kprobes_optimization_handler(struct ctl_table *table,
946 int write, void *buffer,
947 size_t *length, loff_t *ppos)
948 {
949 int ret;
950
951 mutex_lock(&kprobe_sysctl_mutex);
952 sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;
953 ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
954
955 if (sysctl_kprobes_optimization)
956 optimize_all_kprobes();
957 else
958 unoptimize_all_kprobes();
959 mutex_unlock(&kprobe_sysctl_mutex);
960
961 return ret;
962 }
963
964 static struct ctl_table kprobe_sysctls[] = {
965 {
966 .procname = "kprobes-optimization",
967 .data = &sysctl_kprobes_optimization,
968 .maxlen = sizeof(int),
969 .mode = 0644,
970 .proc_handler = proc_kprobes_optimization_handler,
971 .extra1 = SYSCTL_ZERO,
972 .extra2 = SYSCTL_ONE,
973 },
974 {}
975 };
976
kprobe_sysctls_init(void)977 static void __init kprobe_sysctls_init(void)
978 {
979 register_sysctl_init("debug", kprobe_sysctls);
980 }
981 #endif /* CONFIG_SYSCTL */
982
983 /* Put a breakpoint for a probe. */
__arm_kprobe(struct kprobe * p)984 static void __arm_kprobe(struct kprobe *p)
985 {
986 struct kprobe *_p;
987
988 lockdep_assert_held(&text_mutex);
989
990 /* Find the overlapping optimized kprobes. */
991 _p = get_optimized_kprobe(p->addr);
992 if (unlikely(_p))
993 /* Fallback to unoptimized kprobe */
994 unoptimize_kprobe(_p, true);
995
996 arch_arm_kprobe(p);
997 optimize_kprobe(p); /* Try to optimize (add kprobe to a list) */
998 }
999
1000 /* Remove the breakpoint of a probe. */
__disarm_kprobe(struct kprobe * p,bool reopt)1001 static void __disarm_kprobe(struct kprobe *p, bool reopt)
1002 {
1003 struct kprobe *_p;
1004
1005 lockdep_assert_held(&text_mutex);
1006
1007 /* Try to unoptimize */
1008 unoptimize_kprobe(p, kprobes_all_disarmed);
1009
1010 if (!kprobe_queued(p)) {
1011 arch_disarm_kprobe(p);
1012 /* If another kprobe was blocked, re-optimize it. */
1013 _p = get_optimized_kprobe(p->addr);
1014 if (unlikely(_p) && reopt)
1015 optimize_kprobe(_p);
1016 }
1017 /*
1018 * TODO: Since unoptimization and real disarming will be done by
1019 * the worker thread, we can not check whether another probe are
1020 * unoptimized because of this probe here. It should be re-optimized
1021 * by the worker thread.
1022 */
1023 }
1024
1025 #else /* !CONFIG_OPTPROBES */
1026
1027 #define optimize_kprobe(p) do {} while (0)
1028 #define unoptimize_kprobe(p, f) do {} while (0)
1029 #define kill_optimized_kprobe(p) do {} while (0)
1030 #define prepare_optimized_kprobe(p) do {} while (0)
1031 #define try_to_optimize_kprobe(p) do {} while (0)
1032 #define __arm_kprobe(p) arch_arm_kprobe(p)
1033 #define __disarm_kprobe(p, o) arch_disarm_kprobe(p)
1034 #define kprobe_disarmed(p) kprobe_disabled(p)
1035 #define wait_for_kprobe_optimizer() do {} while (0)
1036
reuse_unused_kprobe(struct kprobe * ap)1037 static int reuse_unused_kprobe(struct kprobe *ap)
1038 {
1039 /*
1040 * If the optimized kprobe is NOT supported, the aggr kprobe is
1041 * released at the same time that the last aggregated kprobe is
1042 * unregistered.
1043 * Thus there should be no chance to reuse unused kprobe.
1044 */
1045 WARN_ON_ONCE(1);
1046 return -EINVAL;
1047 }
1048
free_aggr_kprobe(struct kprobe * p)1049 static void free_aggr_kprobe(struct kprobe *p)
1050 {
1051 arch_remove_kprobe(p);
1052 kfree(p);
1053 }
1054
alloc_aggr_kprobe(struct kprobe * p)1055 static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
1056 {
1057 return kzalloc(sizeof(struct kprobe), GFP_KERNEL);
1058 }
1059 #endif /* CONFIG_OPTPROBES */
1060
1061 #ifdef CONFIG_KPROBES_ON_FTRACE
1062 static struct ftrace_ops kprobe_ftrace_ops __read_mostly = {
1063 .func = kprobe_ftrace_handler,
1064 .flags = FTRACE_OPS_FL_SAVE_REGS,
1065 };
1066
1067 static struct ftrace_ops kprobe_ipmodify_ops __read_mostly = {
1068 .func = kprobe_ftrace_handler,
1069 .flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY,
1070 };
1071
1072 static int kprobe_ipmodify_enabled;
1073 static int kprobe_ftrace_enabled;
1074
__arm_kprobe_ftrace(struct kprobe * p,struct ftrace_ops * ops,int * cnt)1075 static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
1076 int *cnt)
1077 {
1078 int ret = 0;
1079
1080 lockdep_assert_held(&kprobe_mutex);
1081
1082 ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 0, 0);
1083 if (WARN_ONCE(ret < 0, "Failed to arm kprobe-ftrace at %pS (error %d)\n", p->addr, ret))
1084 return ret;
1085
1086 if (*cnt == 0) {
1087 ret = register_ftrace_function(ops);
1088 if (WARN(ret < 0, "Failed to register kprobe-ftrace (error %d)\n", ret))
1089 goto err_ftrace;
1090 }
1091
1092 (*cnt)++;
1093 return ret;
1094
1095 err_ftrace:
1096 /*
1097 * At this point, sinec ops is not registered, we should be sefe from
1098 * registering empty filter.
1099 */
1100 ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);
1101 return ret;
1102 }
1103
arm_kprobe_ftrace(struct kprobe * p)1104 static int arm_kprobe_ftrace(struct kprobe *p)
1105 {
1106 bool ipmodify = (p->post_handler != NULL);
1107
1108 return __arm_kprobe_ftrace(p,
1109 ipmodify ? &kprobe_ipmodify_ops : &kprobe_ftrace_ops,
1110 ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);
1111 }
1112
__disarm_kprobe_ftrace(struct kprobe * p,struct ftrace_ops * ops,int * cnt)1113 static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
1114 int *cnt)
1115 {
1116 int ret = 0;
1117
1118 lockdep_assert_held(&kprobe_mutex);
1119
1120 if (*cnt == 1) {
1121 ret = unregister_ftrace_function(ops);
1122 if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (error %d)\n", ret))
1123 return ret;
1124 }
1125
1126 (*cnt)--;
1127
1128 ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);
1129 WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (error %d)\n",
1130 p->addr, ret);
1131 return ret;
1132 }
1133
disarm_kprobe_ftrace(struct kprobe * p)1134 static int disarm_kprobe_ftrace(struct kprobe *p)
1135 {
1136 bool ipmodify = (p->post_handler != NULL);
1137
1138 return __disarm_kprobe_ftrace(p,
1139 ipmodify ? &kprobe_ipmodify_ops : &kprobe_ftrace_ops,
1140 ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);
1141 }
1142 #else /* !CONFIG_KPROBES_ON_FTRACE */
arm_kprobe_ftrace(struct kprobe * p)1143 static inline int arm_kprobe_ftrace(struct kprobe *p)
1144 {
1145 return -ENODEV;
1146 }
1147
disarm_kprobe_ftrace(struct kprobe * p)1148 static inline int disarm_kprobe_ftrace(struct kprobe *p)
1149 {
1150 return -ENODEV;
1151 }
1152 #endif
1153
prepare_kprobe(struct kprobe * p)1154 static int prepare_kprobe(struct kprobe *p)
1155 {
1156 /* Must ensure p->addr is really on ftrace */
1157 if (kprobe_ftrace(p))
1158 return arch_prepare_kprobe_ftrace(p);
1159
1160 return arch_prepare_kprobe(p);
1161 }
1162
arm_kprobe(struct kprobe * kp)1163 static int arm_kprobe(struct kprobe *kp)
1164 {
1165 if (unlikely(kprobe_ftrace(kp)))
1166 return arm_kprobe_ftrace(kp);
1167
1168 cpus_read_lock();
1169 mutex_lock(&text_mutex);
1170 __arm_kprobe(kp);
1171 mutex_unlock(&text_mutex);
1172 cpus_read_unlock();
1173
1174 return 0;
1175 }
1176
disarm_kprobe(struct kprobe * kp,bool reopt)1177 static int disarm_kprobe(struct kprobe *kp, bool reopt)
1178 {
1179 if (unlikely(kprobe_ftrace(kp)))
1180 return disarm_kprobe_ftrace(kp);
1181
1182 cpus_read_lock();
1183 mutex_lock(&text_mutex);
1184 __disarm_kprobe(kp, reopt);
1185 mutex_unlock(&text_mutex);
1186 cpus_read_unlock();
1187
1188 return 0;
1189 }
1190
1191 /*
1192 * Aggregate handlers for multiple kprobes support - these handlers
1193 * take care of invoking the individual kprobe handlers on p->list
1194 */
aggr_pre_handler(struct kprobe * p,struct pt_regs * regs)1195 static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
1196 {
1197 struct kprobe *kp;
1198
1199 list_for_each_entry_rcu(kp, &p->list, list) {
1200 if (kp->pre_handler && likely(!kprobe_disabled(kp))) {
1201 set_kprobe_instance(kp);
1202 if (kp->pre_handler(kp, regs))
1203 return 1;
1204 }
1205 reset_kprobe_instance();
1206 }
1207 return 0;
1208 }
1209 NOKPROBE_SYMBOL(aggr_pre_handler);
1210
aggr_post_handler(struct kprobe * p,struct pt_regs * regs,unsigned long flags)1211 static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
1212 unsigned long flags)
1213 {
1214 struct kprobe *kp;
1215
1216 list_for_each_entry_rcu(kp, &p->list, list) {
1217 if (kp->post_handler && likely(!kprobe_disabled(kp))) {
1218 set_kprobe_instance(kp);
1219 kp->post_handler(kp, regs, flags);
1220 reset_kprobe_instance();
1221 }
1222 }
1223 }
1224 NOKPROBE_SYMBOL(aggr_post_handler);
1225
1226 /* Walks the list and increments 'nmissed' if 'p' has child probes. */
kprobes_inc_nmissed_count(struct kprobe * p)1227 void kprobes_inc_nmissed_count(struct kprobe *p)
1228 {
1229 struct kprobe *kp;
1230
1231 if (!kprobe_aggrprobe(p)) {
1232 p->nmissed++;
1233 } else {
1234 list_for_each_entry_rcu(kp, &p->list, list)
1235 kp->nmissed++;
1236 }
1237 }
1238 NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);
1239
1240 static struct kprobe kprobe_busy = {
1241 .addr = (void *) get_kprobe,
1242 };
1243
kprobe_busy_begin(void)1244 void kprobe_busy_begin(void)
1245 {
1246 struct kprobe_ctlblk *kcb;
1247
1248 preempt_disable();
1249 __this_cpu_write(current_kprobe, &kprobe_busy);
1250 kcb = get_kprobe_ctlblk();
1251 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
1252 }
1253
kprobe_busy_end(void)1254 void kprobe_busy_end(void)
1255 {
1256 __this_cpu_write(current_kprobe, NULL);
1257 preempt_enable();
1258 }
1259
1260 /* Add the new probe to 'ap->list'. */
add_new_kprobe(struct kprobe * ap,struct kprobe * p)1261 static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
1262 {
1263 if (p->post_handler)
1264 unoptimize_kprobe(ap, true); /* Fall back to normal kprobe */
1265
1266 list_add_rcu(&p->list, &ap->list);
1267 if (p->post_handler && !ap->post_handler)
1268 ap->post_handler = aggr_post_handler;
1269
1270 return 0;
1271 }
1272
1273 /*
1274 * Fill in the required fields of the aggregator kprobe. Replace the
1275 * earlier kprobe in the hlist with the aggregator kprobe.
1276 */
init_aggr_kprobe(struct kprobe * ap,struct kprobe * p)1277 static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
1278 {
1279 /* Copy the insn slot of 'p' to 'ap'. */
1280 copy_kprobe(p, ap);
1281 flush_insn_slot(ap);
1282 ap->addr = p->addr;
1283 ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
1284 ap->pre_handler = aggr_pre_handler;
1285 /* We don't care the kprobe which has gone. */
1286 if (p->post_handler && !kprobe_gone(p))
1287 ap->post_handler = aggr_post_handler;
1288
1289 INIT_LIST_HEAD(&ap->list);
1290 INIT_HLIST_NODE(&ap->hlist);
1291
1292 list_add_rcu(&p->list, &ap->list);
1293 hlist_replace_rcu(&p->hlist, &ap->hlist);
1294 }
1295
1296 /*
1297 * This registers the second or subsequent kprobe at the same address.
1298 */
register_aggr_kprobe(struct kprobe * orig_p,struct kprobe * p)1299 static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
1300 {
1301 int ret = 0;
1302 struct kprobe *ap = orig_p;
1303
1304 cpus_read_lock();
1305
1306 /* For preparing optimization, jump_label_text_reserved() is called */
1307 jump_label_lock();
1308 mutex_lock(&text_mutex);
1309
1310 if (!kprobe_aggrprobe(orig_p)) {
1311 /* If 'orig_p' is not an 'aggr_kprobe', create new one. */
1312 ap = alloc_aggr_kprobe(orig_p);
1313 if (!ap) {
1314 ret = -ENOMEM;
1315 goto out;
1316 }
1317 init_aggr_kprobe(ap, orig_p);
1318 } else if (kprobe_unused(ap)) {
1319 /* This probe is going to die. Rescue it */
1320 ret = reuse_unused_kprobe(ap);
1321 if (ret)
1322 goto out;
1323 }
1324
1325 if (kprobe_gone(ap)) {
1326 /*
1327 * Attempting to insert new probe at the same location that
1328 * had a probe in the module vaddr area which already
1329 * freed. So, the instruction slot has already been
1330 * released. We need a new slot for the new probe.
1331 */
1332 ret = arch_prepare_kprobe(ap);
1333 if (ret)
1334 /*
1335 * Even if fail to allocate new slot, don't need to
1336 * free the 'ap'. It will be used next time, or
1337 * freed by unregister_kprobe().
1338 */
1339 goto out;
1340
1341 /* Prepare optimized instructions if possible. */
1342 prepare_optimized_kprobe(ap);
1343
1344 /*
1345 * Clear gone flag to prevent allocating new slot again, and
1346 * set disabled flag because it is not armed yet.
1347 */
1348 ap->flags = (ap->flags & ~KPROBE_FLAG_GONE)
1349 | KPROBE_FLAG_DISABLED;
1350 }
1351
1352 /* Copy the insn slot of 'p' to 'ap'. */
1353 copy_kprobe(ap, p);
1354 ret = add_new_kprobe(ap, p);
1355
1356 out:
1357 mutex_unlock(&text_mutex);
1358 jump_label_unlock();
1359 cpus_read_unlock();
1360
1361 if (ret == 0 && kprobe_disabled(ap) && !kprobe_disabled(p)) {
1362 ap->flags &= ~KPROBE_FLAG_DISABLED;
1363 if (!kprobes_all_disarmed) {
1364 /* Arm the breakpoint again. */
1365 ret = arm_kprobe(ap);
1366 if (ret) {
1367 ap->flags |= KPROBE_FLAG_DISABLED;
1368 list_del_rcu(&p->list);
1369 synchronize_rcu();
1370 }
1371 }
1372 }
1373 return ret;
1374 }
1375
arch_within_kprobe_blacklist(unsigned long addr)1376 bool __weak arch_within_kprobe_blacklist(unsigned long addr)
1377 {
1378 /* The '__kprobes' functions and entry code must not be probed. */
1379 return addr >= (unsigned long)__kprobes_text_start &&
1380 addr < (unsigned long)__kprobes_text_end;
1381 }
1382
__within_kprobe_blacklist(unsigned long addr)1383 static bool __within_kprobe_blacklist(unsigned long addr)
1384 {
1385 struct kprobe_blacklist_entry *ent;
1386
1387 if (arch_within_kprobe_blacklist(addr))
1388 return true;
1389 /*
1390 * If 'kprobe_blacklist' is defined, check the address and
1391 * reject any probe registration in the prohibited area.
1392 */
1393 list_for_each_entry(ent, &kprobe_blacklist, list) {
1394 if (addr >= ent->start_addr && addr < ent->end_addr)
1395 return true;
1396 }
1397 return false;
1398 }
1399
within_kprobe_blacklist(unsigned long addr)1400 bool within_kprobe_blacklist(unsigned long addr)
1401 {
1402 char symname[KSYM_NAME_LEN], *p;
1403
1404 if (__within_kprobe_blacklist(addr))
1405 return true;
1406
1407 /* Check if the address is on a suffixed-symbol */
1408 if (!lookup_symbol_name(addr, symname)) {
1409 p = strchr(symname, '.');
1410 if (!p)
1411 return false;
1412 *p = '\0';
1413 addr = (unsigned long)kprobe_lookup_name(symname, 0);
1414 if (addr)
1415 return __within_kprobe_blacklist(addr);
1416 }
1417 return false;
1418 }
1419
1420 /*
1421 * arch_adjust_kprobe_addr - adjust the address
1422 * @addr: symbol base address
1423 * @offset: offset within the symbol
1424 * @on_func_entry: was this @addr+@offset on the function entry
1425 *
1426 * Typically returns @addr + @offset, except for special cases where the
1427 * function might be prefixed by a CFI landing pad, in that case any offset
1428 * inside the landing pad is mapped to the first 'real' instruction of the
1429 * symbol.
1430 *
1431 * Specifically, for things like IBT/BTI, skip the resp. ENDBR/BTI.C
1432 * instruction at +0.
1433 */
arch_adjust_kprobe_addr(unsigned long addr,unsigned long offset,bool * on_func_entry)1434 kprobe_opcode_t *__weak arch_adjust_kprobe_addr(unsigned long addr,
1435 unsigned long offset,
1436 bool *on_func_entry)
1437 {
1438 *on_func_entry = !offset;
1439 return (kprobe_opcode_t *)(addr + offset);
1440 }
1441
1442 /*
1443 * If 'symbol_name' is specified, look it up and add the 'offset'
1444 * to it. This way, we can specify a relative address to a symbol.
1445 * This returns encoded errors if it fails to look up symbol or invalid
1446 * combination of parameters.
1447 */
1448 static kprobe_opcode_t *
_kprobe_addr(kprobe_opcode_t * addr,const char * symbol_name,unsigned long offset,bool * on_func_entry)1449 _kprobe_addr(kprobe_opcode_t *addr, const char *symbol_name,
1450 unsigned long offset, bool *on_func_entry)
1451 {
1452 if ((symbol_name && addr) || (!symbol_name && !addr))
1453 goto invalid;
1454
1455 if (symbol_name) {
1456 /*
1457 * Input: @sym + @offset
1458 * Output: @addr + @offset
1459 *
1460 * NOTE: kprobe_lookup_name() does *NOT* fold the offset
1461 * argument into it's output!
1462 */
1463 addr = kprobe_lookup_name(symbol_name, offset);
1464 if (!addr)
1465 return ERR_PTR(-ENOENT);
1466 }
1467
1468 /*
1469 * So here we have @addr + @offset, displace it into a new
1470 * @addr' + @offset' where @addr' is the symbol start address.
1471 */
1472 addr = (void *)addr + offset;
1473 if (!kallsyms_lookup_size_offset((unsigned long)addr, NULL, &offset))
1474 return ERR_PTR(-ENOENT);
1475 addr = (void *)addr - offset;
1476
1477 /*
1478 * Then ask the architecture to re-combine them, taking care of
1479 * magical function entry details while telling us if this was indeed
1480 * at the start of the function.
1481 */
1482 addr = arch_adjust_kprobe_addr((unsigned long)addr, offset, on_func_entry);
1483 if (addr)
1484 return addr;
1485
1486 invalid:
1487 return ERR_PTR(-EINVAL);
1488 }
1489
kprobe_addr(struct kprobe * p)1490 static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
1491 {
1492 bool on_func_entry;
1493 return _kprobe_addr(p->addr, p->symbol_name, p->offset, &on_func_entry);
1494 }
1495
1496 /*
1497 * Check the 'p' is valid and return the aggregator kprobe
1498 * at the same address.
1499 */
__get_valid_kprobe(struct kprobe * p)1500 static struct kprobe *__get_valid_kprobe(struct kprobe *p)
1501 {
1502 struct kprobe *ap, *list_p;
1503
1504 lockdep_assert_held(&kprobe_mutex);
1505
1506 ap = get_kprobe(p->addr);
1507 if (unlikely(!ap))
1508 return NULL;
1509
1510 if (p != ap) {
1511 list_for_each_entry(list_p, &ap->list, list)
1512 if (list_p == p)
1513 /* kprobe p is a valid probe */
1514 goto valid;
1515 return NULL;
1516 }
1517 valid:
1518 return ap;
1519 }
1520
1521 /*
1522 * Warn and return error if the kprobe is being re-registered since
1523 * there must be a software bug.
1524 */
warn_kprobe_rereg(struct kprobe * p)1525 static inline int warn_kprobe_rereg(struct kprobe *p)
1526 {
1527 int ret = 0;
1528
1529 mutex_lock(&kprobe_mutex);
1530 if (WARN_ON_ONCE(__get_valid_kprobe(p)))
1531 ret = -EINVAL;
1532 mutex_unlock(&kprobe_mutex);
1533
1534 return ret;
1535 }
1536
check_ftrace_location(struct kprobe * p)1537 static int check_ftrace_location(struct kprobe *p)
1538 {
1539 unsigned long addr = (unsigned long)p->addr;
1540
1541 if (ftrace_location(addr) == addr) {
1542 #ifdef CONFIG_KPROBES_ON_FTRACE
1543 p->flags |= KPROBE_FLAG_FTRACE;
1544 #else /* !CONFIG_KPROBES_ON_FTRACE */
1545 return -EINVAL;
1546 #endif
1547 }
1548 return 0;
1549 }
1550
check_kprobe_address_safe(struct kprobe * p,struct module ** probed_mod)1551 static int check_kprobe_address_safe(struct kprobe *p,
1552 struct module **probed_mod)
1553 {
1554 int ret;
1555
1556 ret = check_ftrace_location(p);
1557 if (ret)
1558 return ret;
1559 jump_label_lock();
1560 preempt_disable();
1561
1562 /* Ensure it is not in reserved area nor out of text */
1563 if (!(core_kernel_text((unsigned long) p->addr) ||
1564 is_module_text_address((unsigned long) p->addr)) ||
1565 in_gate_area_no_mm((unsigned long) p->addr) ||
1566 within_kprobe_blacklist((unsigned long) p->addr) ||
1567 jump_label_text_reserved(p->addr, p->addr) ||
1568 static_call_text_reserved(p->addr, p->addr) ||
1569 find_bug((unsigned long)p->addr)) {
1570 ret = -EINVAL;
1571 goto out;
1572 }
1573
1574 /* Check if 'p' is probing a module. */
1575 *probed_mod = __module_text_address((unsigned long) p->addr);
1576 if (*probed_mod) {
1577 /*
1578 * We must hold a refcount of the probed module while updating
1579 * its code to prohibit unexpected unloading.
1580 */
1581 if (unlikely(!try_module_get(*probed_mod))) {
1582 ret = -ENOENT;
1583 goto out;
1584 }
1585
1586 /*
1587 * If the module freed '.init.text', we couldn't insert
1588 * kprobes in there.
1589 */
1590 if (within_module_init((unsigned long)p->addr, *probed_mod) &&
1591 (*probed_mod)->state != MODULE_STATE_COMING) {
1592 module_put(*probed_mod);
1593 *probed_mod = NULL;
1594 ret = -ENOENT;
1595 }
1596 }
1597 out:
1598 preempt_enable();
1599 jump_label_unlock();
1600
1601 return ret;
1602 }
1603
register_kprobe(struct kprobe * p)1604 int register_kprobe(struct kprobe *p)
1605 {
1606 int ret;
1607 struct kprobe *old_p;
1608 struct module *probed_mod;
1609 kprobe_opcode_t *addr;
1610
1611 /* Adjust probe address from symbol */
1612 addr = kprobe_addr(p);
1613 if (IS_ERR(addr))
1614 return PTR_ERR(addr);
1615 p->addr = addr;
1616
1617 ret = warn_kprobe_rereg(p);
1618 if (ret)
1619 return ret;
1620
1621 /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
1622 p->flags &= KPROBE_FLAG_DISABLED;
1623 p->nmissed = 0;
1624 INIT_LIST_HEAD(&p->list);
1625
1626 ret = check_kprobe_address_safe(p, &probed_mod);
1627 if (ret)
1628 return ret;
1629
1630 mutex_lock(&kprobe_mutex);
1631
1632 old_p = get_kprobe(p->addr);
1633 if (old_p) {
1634 /* Since this may unoptimize 'old_p', locking 'text_mutex'. */
1635 ret = register_aggr_kprobe(old_p, p);
1636 goto out;
1637 }
1638
1639 cpus_read_lock();
1640 /* Prevent text modification */
1641 mutex_lock(&text_mutex);
1642 ret = prepare_kprobe(p);
1643 mutex_unlock(&text_mutex);
1644 cpus_read_unlock();
1645 if (ret)
1646 goto out;
1647
1648 INIT_HLIST_NODE(&p->hlist);
1649 hlist_add_head_rcu(&p->hlist,
1650 &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
1651
1652 if (!kprobes_all_disarmed && !kprobe_disabled(p)) {
1653 ret = arm_kprobe(p);
1654 if (ret) {
1655 hlist_del_rcu(&p->hlist);
1656 synchronize_rcu();
1657 goto out;
1658 }
1659 }
1660
1661 /* Try to optimize kprobe */
1662 try_to_optimize_kprobe(p);
1663 out:
1664 mutex_unlock(&kprobe_mutex);
1665
1666 if (probed_mod)
1667 module_put(probed_mod);
1668
1669 return ret;
1670 }
1671 EXPORT_SYMBOL_GPL(register_kprobe);
1672
1673 /* Check if all probes on the 'ap' are disabled. */
aggr_kprobe_disabled(struct kprobe * ap)1674 static bool aggr_kprobe_disabled(struct kprobe *ap)
1675 {
1676 struct kprobe *kp;
1677
1678 lockdep_assert_held(&kprobe_mutex);
1679
1680 list_for_each_entry(kp, &ap->list, list)
1681 if (!kprobe_disabled(kp))
1682 /*
1683 * Since there is an active probe on the list,
1684 * we can't disable this 'ap'.
1685 */
1686 return false;
1687
1688 return true;
1689 }
1690
__disable_kprobe(struct kprobe * p)1691 static struct kprobe *__disable_kprobe(struct kprobe *p)
1692 {
1693 struct kprobe *orig_p;
1694 int ret;
1695
1696 lockdep_assert_held(&kprobe_mutex);
1697
1698 /* Get an original kprobe for return */
1699 orig_p = __get_valid_kprobe(p);
1700 if (unlikely(orig_p == NULL))
1701 return ERR_PTR(-EINVAL);
1702
1703 if (!kprobe_disabled(p)) {
1704 /* Disable probe if it is a child probe */
1705 if (p != orig_p)
1706 p->flags |= KPROBE_FLAG_DISABLED;
1707
1708 /* Try to disarm and disable this/parent probe */
1709 if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
1710 /*
1711 * Don't be lazy here. Even if 'kprobes_all_disarmed'
1712 * is false, 'orig_p' might not have been armed yet.
1713 * Note arm_all_kprobes() __tries__ to arm all kprobes
1714 * on the best effort basis.
1715 */
1716 if (!kprobes_all_disarmed && !kprobe_disabled(orig_p)) {
1717 ret = disarm_kprobe(orig_p, true);
1718 if (ret) {
1719 p->flags &= ~KPROBE_FLAG_DISABLED;
1720 return ERR_PTR(ret);
1721 }
1722 }
1723 orig_p->flags |= KPROBE_FLAG_DISABLED;
1724 }
1725 }
1726
1727 return orig_p;
1728 }
1729
1730 /*
1731 * Unregister a kprobe without a scheduler synchronization.
1732 */
__unregister_kprobe_top(struct kprobe * p)1733 static int __unregister_kprobe_top(struct kprobe *p)
1734 {
1735 struct kprobe *ap, *list_p;
1736
1737 /* Disable kprobe. This will disarm it if needed. */
1738 ap = __disable_kprobe(p);
1739 if (IS_ERR(ap))
1740 return PTR_ERR(ap);
1741
1742 if (ap == p)
1743 /*
1744 * This probe is an independent(and non-optimized) kprobe
1745 * (not an aggrprobe). Remove from the hash list.
1746 */
1747 goto disarmed;
1748
1749 /* Following process expects this probe is an aggrprobe */
1750 WARN_ON(!kprobe_aggrprobe(ap));
1751
1752 if (list_is_singular(&ap->list) && kprobe_disarmed(ap))
1753 /*
1754 * !disarmed could be happen if the probe is under delayed
1755 * unoptimizing.
1756 */
1757 goto disarmed;
1758 else {
1759 /* If disabling probe has special handlers, update aggrprobe */
1760 if (p->post_handler && !kprobe_gone(p)) {
1761 list_for_each_entry(list_p, &ap->list, list) {
1762 if ((list_p != p) && (list_p->post_handler))
1763 goto noclean;
1764 }
1765 ap->post_handler = NULL;
1766 }
1767 noclean:
1768 /*
1769 * Remove from the aggrprobe: this path will do nothing in
1770 * __unregister_kprobe_bottom().
1771 */
1772 list_del_rcu(&p->list);
1773 if (!kprobe_disabled(ap) && !kprobes_all_disarmed)
1774 /*
1775 * Try to optimize this probe again, because post
1776 * handler may have been changed.
1777 */
1778 optimize_kprobe(ap);
1779 }
1780 return 0;
1781
1782 disarmed:
1783 hlist_del_rcu(&ap->hlist);
1784 return 0;
1785 }
1786
__unregister_kprobe_bottom(struct kprobe * p)1787 static void __unregister_kprobe_bottom(struct kprobe *p)
1788 {
1789 struct kprobe *ap;
1790
1791 if (list_empty(&p->list))
1792 /* This is an independent kprobe */
1793 arch_remove_kprobe(p);
1794 else if (list_is_singular(&p->list)) {
1795 /* This is the last child of an aggrprobe */
1796 ap = list_entry(p->list.next, struct kprobe, list);
1797 list_del(&p->list);
1798 free_aggr_kprobe(ap);
1799 }
1800 /* Otherwise, do nothing. */
1801 }
1802
register_kprobes(struct kprobe ** kps,int num)1803 int register_kprobes(struct kprobe **kps, int num)
1804 {
1805 int i, ret = 0;
1806
1807 if (num <= 0)
1808 return -EINVAL;
1809 for (i = 0; i < num; i++) {
1810 ret = register_kprobe(kps[i]);
1811 if (ret < 0) {
1812 if (i > 0)
1813 unregister_kprobes(kps, i);
1814 break;
1815 }
1816 }
1817 return ret;
1818 }
1819 EXPORT_SYMBOL_GPL(register_kprobes);
1820
unregister_kprobe(struct kprobe * p)1821 void unregister_kprobe(struct kprobe *p)
1822 {
1823 unregister_kprobes(&p, 1);
1824 }
1825 EXPORT_SYMBOL_GPL(unregister_kprobe);
1826
unregister_kprobes(struct kprobe ** kps,int num)1827 void unregister_kprobes(struct kprobe **kps, int num)
1828 {
1829 int i;
1830
1831 if (num <= 0)
1832 return;
1833 mutex_lock(&kprobe_mutex);
1834 for (i = 0; i < num; i++)
1835 if (__unregister_kprobe_top(kps[i]) < 0)
1836 kps[i]->addr = NULL;
1837 mutex_unlock(&kprobe_mutex);
1838
1839 synchronize_rcu();
1840 for (i = 0; i < num; i++)
1841 if (kps[i]->addr)
1842 __unregister_kprobe_bottom(kps[i]);
1843 }
1844 EXPORT_SYMBOL_GPL(unregister_kprobes);
1845
kprobe_exceptions_notify(struct notifier_block * self,unsigned long val,void * data)1846 int __weak kprobe_exceptions_notify(struct notifier_block *self,
1847 unsigned long val, void *data)
1848 {
1849 return NOTIFY_DONE;
1850 }
1851 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
1852
1853 static struct notifier_block kprobe_exceptions_nb = {
1854 .notifier_call = kprobe_exceptions_notify,
1855 .priority = 0x7fffffff /* we need to be notified first */
1856 };
1857
1858 #ifdef CONFIG_KRETPROBES
1859
1860 #if !defined(CONFIG_KRETPROBE_ON_RETHOOK)
free_rp_inst_rcu(struct rcu_head * head)1861 static void free_rp_inst_rcu(struct rcu_head *head)
1862 {
1863 struct kretprobe_instance *ri = container_of(head, struct kretprobe_instance, rcu);
1864
1865 if (refcount_dec_and_test(&ri->rph->ref))
1866 kfree(ri->rph);
1867 kfree(ri);
1868 }
1869 NOKPROBE_SYMBOL(free_rp_inst_rcu);
1870
recycle_rp_inst(struct kretprobe_instance * ri)1871 static void recycle_rp_inst(struct kretprobe_instance *ri)
1872 {
1873 struct kretprobe *rp = get_kretprobe(ri);
1874
1875 if (likely(rp))
1876 freelist_add(&ri->freelist, &rp->freelist);
1877 else
1878 call_rcu(&ri->rcu, free_rp_inst_rcu);
1879 }
1880 NOKPROBE_SYMBOL(recycle_rp_inst);
1881
1882 /*
1883 * This function is called from delayed_put_task_struct() when a task is
1884 * dead and cleaned up to recycle any kretprobe instances associated with
1885 * this task. These left over instances represent probed functions that
1886 * have been called but will never return.
1887 */
kprobe_flush_task(struct task_struct * tk)1888 void kprobe_flush_task(struct task_struct *tk)
1889 {
1890 struct kretprobe_instance *ri;
1891 struct llist_node *node;
1892
1893 /* Early boot, not yet initialized. */
1894 if (unlikely(!kprobes_initialized))
1895 return;
1896
1897 kprobe_busy_begin();
1898
1899 node = __llist_del_all(&tk->kretprobe_instances);
1900 while (node) {
1901 ri = container_of(node, struct kretprobe_instance, llist);
1902 node = node->next;
1903
1904 recycle_rp_inst(ri);
1905 }
1906
1907 kprobe_busy_end();
1908 }
1909 NOKPROBE_SYMBOL(kprobe_flush_task);
1910
free_rp_inst(struct kretprobe * rp)1911 static inline void free_rp_inst(struct kretprobe *rp)
1912 {
1913 struct kretprobe_instance *ri;
1914 struct freelist_node *node;
1915 int count = 0;
1916
1917 node = rp->freelist.head;
1918 while (node) {
1919 ri = container_of(node, struct kretprobe_instance, freelist);
1920 node = node->next;
1921
1922 kfree(ri);
1923 count++;
1924 }
1925
1926 if (refcount_sub_and_test(count, &rp->rph->ref)) {
1927 kfree(rp->rph);
1928 rp->rph = NULL;
1929 }
1930 }
1931
1932 /* This assumes the 'tsk' is the current task or the is not running. */
__kretprobe_find_ret_addr(struct task_struct * tsk,struct llist_node ** cur)1933 static kprobe_opcode_t *__kretprobe_find_ret_addr(struct task_struct *tsk,
1934 struct llist_node **cur)
1935 {
1936 struct kretprobe_instance *ri = NULL;
1937 struct llist_node *node = *cur;
1938
1939 if (!node)
1940 node = tsk->kretprobe_instances.first;
1941 else
1942 node = node->next;
1943
1944 while (node) {
1945 ri = container_of(node, struct kretprobe_instance, llist);
1946 if (ri->ret_addr != kretprobe_trampoline_addr()) {
1947 *cur = node;
1948 return ri->ret_addr;
1949 }
1950 node = node->next;
1951 }
1952 return NULL;
1953 }
1954 NOKPROBE_SYMBOL(__kretprobe_find_ret_addr);
1955
1956 /**
1957 * kretprobe_find_ret_addr -- Find correct return address modified by kretprobe
1958 * @tsk: Target task
1959 * @fp: A frame pointer
1960 * @cur: a storage of the loop cursor llist_node pointer for next call
1961 *
1962 * Find the correct return address modified by a kretprobe on @tsk in unsigned
1963 * long type. If it finds the return address, this returns that address value,
1964 * or this returns 0.
1965 * The @tsk must be 'current' or a task which is not running. @fp is a hint
1966 * to get the currect return address - which is compared with the
1967 * kretprobe_instance::fp field. The @cur is a loop cursor for searching the
1968 * kretprobe return addresses on the @tsk. The '*@cur' should be NULL at the
1969 * first call, but '@cur' itself must NOT NULL.
1970 */
kretprobe_find_ret_addr(struct task_struct * tsk,void * fp,struct llist_node ** cur)1971 unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp,
1972 struct llist_node **cur)
1973 {
1974 struct kretprobe_instance *ri = NULL;
1975 kprobe_opcode_t *ret;
1976
1977 if (WARN_ON_ONCE(!cur))
1978 return 0;
1979
1980 do {
1981 ret = __kretprobe_find_ret_addr(tsk, cur);
1982 if (!ret)
1983 break;
1984 ri = container_of(*cur, struct kretprobe_instance, llist);
1985 } while (ri->fp != fp);
1986
1987 return (unsigned long)ret;
1988 }
1989 NOKPROBE_SYMBOL(kretprobe_find_ret_addr);
1990
arch_kretprobe_fixup_return(struct pt_regs * regs,kprobe_opcode_t * correct_ret_addr)1991 void __weak arch_kretprobe_fixup_return(struct pt_regs *regs,
1992 kprobe_opcode_t *correct_ret_addr)
1993 {
1994 /*
1995 * Do nothing by default. Please fill this to update the fake return
1996 * address on the stack with the correct one on each arch if possible.
1997 */
1998 }
1999
__kretprobe_trampoline_handler(struct pt_regs * regs,void * frame_pointer)2000 unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
2001 void *frame_pointer)
2002 {
2003 kprobe_opcode_t *correct_ret_addr = NULL;
2004 struct kretprobe_instance *ri = NULL;
2005 struct llist_node *first, *node = NULL;
2006 struct kretprobe *rp;
2007
2008 /* Find correct address and all nodes for this frame. */
2009 correct_ret_addr = __kretprobe_find_ret_addr(current, &node);
2010 if (!correct_ret_addr) {
2011 pr_err("kretprobe: Return address not found, not execute handler. Maybe there is a bug in the kernel.\n");
2012 BUG_ON(1);
2013 }
2014
2015 /*
2016 * Set the return address as the instruction pointer, because if the
2017 * user handler calls stack_trace_save_regs() with this 'regs',
2018 * the stack trace will start from the instruction pointer.
2019 */
2020 instruction_pointer_set(regs, (unsigned long)correct_ret_addr);
2021
2022 /* Run the user handler of the nodes. */
2023 first = current->kretprobe_instances.first;
2024 while (first) {
2025 ri = container_of(first, struct kretprobe_instance, llist);
2026
2027 if (WARN_ON_ONCE(ri->fp != frame_pointer))
2028 break;
2029
2030 rp = get_kretprobe(ri);
2031 if (rp && rp->handler) {
2032 struct kprobe *prev = kprobe_running();
2033
2034 __this_cpu_write(current_kprobe, &rp->kp);
2035 ri->ret_addr = correct_ret_addr;
2036 rp->handler(ri, regs);
2037 __this_cpu_write(current_kprobe, prev);
2038 }
2039 if (first == node)
2040 break;
2041
2042 first = first->next;
2043 }
2044
2045 arch_kretprobe_fixup_return(regs, correct_ret_addr);
2046
2047 /* Unlink all nodes for this frame. */
2048 first = current->kretprobe_instances.first;
2049 current->kretprobe_instances.first = node->next;
2050 node->next = NULL;
2051
2052 /* Recycle free instances. */
2053 while (first) {
2054 ri = container_of(first, struct kretprobe_instance, llist);
2055 first = first->next;
2056
2057 recycle_rp_inst(ri);
2058 }
2059
2060 return (unsigned long)correct_ret_addr;
2061 }
NOKPROBE_SYMBOL(__kretprobe_trampoline_handler)2062 NOKPROBE_SYMBOL(__kretprobe_trampoline_handler)
2063
2064 /*
2065 * This kprobe pre_handler is registered with every kretprobe. When probe
2066 * hits it will set up the return probe.
2067 */
2068 static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
2069 {
2070 struct kretprobe *rp = container_of(p, struct kretprobe, kp);
2071 struct kretprobe_instance *ri;
2072 struct freelist_node *fn;
2073
2074 fn = freelist_try_get(&rp->freelist);
2075 if (!fn) {
2076 rp->nmissed++;
2077 return 0;
2078 }
2079
2080 ri = container_of(fn, struct kretprobe_instance, freelist);
2081
2082 if (rp->entry_handler && rp->entry_handler(ri, regs)) {
2083 freelist_add(&ri->freelist, &rp->freelist);
2084 return 0;
2085 }
2086
2087 arch_prepare_kretprobe(ri, regs);
2088
2089 __llist_add(&ri->llist, ¤t->kretprobe_instances);
2090
2091 return 0;
2092 }
2093 NOKPROBE_SYMBOL(pre_handler_kretprobe);
2094 #else /* CONFIG_KRETPROBE_ON_RETHOOK */
2095 /*
2096 * This kprobe pre_handler is registered with every kretprobe. When probe
2097 * hits it will set up the return probe.
2098 */
pre_handler_kretprobe(struct kprobe * p,struct pt_regs * regs)2099 static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
2100 {
2101 struct kretprobe *rp = container_of(p, struct kretprobe, kp);
2102 struct kretprobe_instance *ri;
2103 struct rethook_node *rhn;
2104
2105 rhn = rethook_try_get(rp->rh);
2106 if (!rhn) {
2107 rp->nmissed++;
2108 return 0;
2109 }
2110
2111 ri = container_of(rhn, struct kretprobe_instance, node);
2112
2113 if (rp->entry_handler && rp->entry_handler(ri, regs))
2114 rethook_recycle(rhn);
2115 else
2116 rethook_hook(rhn, regs, kprobe_ftrace(p));
2117
2118 return 0;
2119 }
2120 NOKPROBE_SYMBOL(pre_handler_kretprobe);
2121
kretprobe_rethook_handler(struct rethook_node * rh,void * data,struct pt_regs * regs)2122 static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
2123 struct pt_regs *regs)
2124 {
2125 struct kretprobe *rp = (struct kretprobe *)data;
2126 struct kretprobe_instance *ri;
2127 struct kprobe_ctlblk *kcb;
2128
2129 /* The data must NOT be null. This means rethook data structure is broken. */
2130 if (WARN_ON_ONCE(!data) || !rp->handler)
2131 return;
2132
2133 __this_cpu_write(current_kprobe, &rp->kp);
2134 kcb = get_kprobe_ctlblk();
2135 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
2136
2137 ri = container_of(rh, struct kretprobe_instance, node);
2138 rp->handler(ri, regs);
2139
2140 __this_cpu_write(current_kprobe, NULL);
2141 }
2142 NOKPROBE_SYMBOL(kretprobe_rethook_handler);
2143
2144 #endif /* !CONFIG_KRETPROBE_ON_RETHOOK */
2145
2146 /**
2147 * kprobe_on_func_entry() -- check whether given address is function entry
2148 * @addr: Target address
2149 * @sym: Target symbol name
2150 * @offset: The offset from the symbol or the address
2151 *
2152 * This checks whether the given @addr+@offset or @sym+@offset is on the
2153 * function entry address or not.
2154 * This returns 0 if it is the function entry, or -EINVAL if it is not.
2155 * And also it returns -ENOENT if it fails the symbol or address lookup.
2156 * Caller must pass @addr or @sym (either one must be NULL), or this
2157 * returns -EINVAL.
2158 */
kprobe_on_func_entry(kprobe_opcode_t * addr,const char * sym,unsigned long offset)2159 int kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
2160 {
2161 bool on_func_entry;
2162 kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset, &on_func_entry);
2163
2164 if (IS_ERR(kp_addr))
2165 return PTR_ERR(kp_addr);
2166
2167 if (!on_func_entry)
2168 return -EINVAL;
2169
2170 return 0;
2171 }
2172
register_kretprobe(struct kretprobe * rp)2173 int register_kretprobe(struct kretprobe *rp)
2174 {
2175 int ret;
2176 struct kretprobe_instance *inst;
2177 int i;
2178 void *addr;
2179
2180 ret = kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset);
2181 if (ret)
2182 return ret;
2183
2184 /* If only 'rp->kp.addr' is specified, check reregistering kprobes */
2185 if (rp->kp.addr && warn_kprobe_rereg(&rp->kp))
2186 return -EINVAL;
2187
2188 if (kretprobe_blacklist_size) {
2189 addr = kprobe_addr(&rp->kp);
2190 if (IS_ERR(addr))
2191 return PTR_ERR(addr);
2192
2193 for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
2194 if (kretprobe_blacklist[i].addr == addr)
2195 return -EINVAL;
2196 }
2197 }
2198
2199 if (rp->data_size > KRETPROBE_MAX_DATA_SIZE)
2200 return -E2BIG;
2201
2202 rp->kp.pre_handler = pre_handler_kretprobe;
2203 rp->kp.post_handler = NULL;
2204
2205 /* Pre-allocate memory for max kretprobe instances */
2206 if (rp->maxactive <= 0) {
2207 #ifdef CONFIG_PREEMPTION
2208 rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
2209 #else
2210 rp->maxactive = num_possible_cpus();
2211 #endif
2212 }
2213 #ifdef CONFIG_KRETPROBE_ON_RETHOOK
2214 rp->rh = rethook_alloc((void *)rp, kretprobe_rethook_handler);
2215 if (!rp->rh)
2216 return -ENOMEM;
2217
2218 for (i = 0; i < rp->maxactive; i++) {
2219 inst = kzalloc(sizeof(struct kretprobe_instance) +
2220 rp->data_size, GFP_KERNEL);
2221 if (inst == NULL) {
2222 rethook_free(rp->rh);
2223 rp->rh = NULL;
2224 return -ENOMEM;
2225 }
2226 rethook_add_node(rp->rh, &inst->node);
2227 }
2228 rp->nmissed = 0;
2229 /* Establish function entry probe point */
2230 ret = register_kprobe(&rp->kp);
2231 if (ret != 0) {
2232 rethook_free(rp->rh);
2233 rp->rh = NULL;
2234 }
2235 #else /* !CONFIG_KRETPROBE_ON_RETHOOK */
2236 rp->freelist.head = NULL;
2237 rp->rph = kzalloc(sizeof(struct kretprobe_holder), GFP_KERNEL);
2238 if (!rp->rph)
2239 return -ENOMEM;
2240
2241 rp->rph->rp = rp;
2242 for (i = 0; i < rp->maxactive; i++) {
2243 inst = kzalloc(sizeof(struct kretprobe_instance) +
2244 rp->data_size, GFP_KERNEL);
2245 if (inst == NULL) {
2246 refcount_set(&rp->rph->ref, i);
2247 free_rp_inst(rp);
2248 return -ENOMEM;
2249 }
2250 inst->rph = rp->rph;
2251 freelist_add(&inst->freelist, &rp->freelist);
2252 }
2253 refcount_set(&rp->rph->ref, i);
2254
2255 rp->nmissed = 0;
2256 /* Establish function entry probe point */
2257 ret = register_kprobe(&rp->kp);
2258 if (ret != 0)
2259 free_rp_inst(rp);
2260 #endif
2261 return ret;
2262 }
2263 EXPORT_SYMBOL_GPL(register_kretprobe);
2264
register_kretprobes(struct kretprobe ** rps,int num)2265 int register_kretprobes(struct kretprobe **rps, int num)
2266 {
2267 int ret = 0, i;
2268
2269 if (num <= 0)
2270 return -EINVAL;
2271 for (i = 0; i < num; i++) {
2272 ret = register_kretprobe(rps[i]);
2273 if (ret < 0) {
2274 if (i > 0)
2275 unregister_kretprobes(rps, i);
2276 break;
2277 }
2278 }
2279 return ret;
2280 }
2281 EXPORT_SYMBOL_GPL(register_kretprobes);
2282
unregister_kretprobe(struct kretprobe * rp)2283 void unregister_kretprobe(struct kretprobe *rp)
2284 {
2285 unregister_kretprobes(&rp, 1);
2286 }
2287 EXPORT_SYMBOL_GPL(unregister_kretprobe);
2288
unregister_kretprobes(struct kretprobe ** rps,int num)2289 void unregister_kretprobes(struct kretprobe **rps, int num)
2290 {
2291 int i;
2292
2293 if (num <= 0)
2294 return;
2295 mutex_lock(&kprobe_mutex);
2296 for (i = 0; i < num; i++) {
2297 if (__unregister_kprobe_top(&rps[i]->kp) < 0)
2298 rps[i]->kp.addr = NULL;
2299 #ifdef CONFIG_KRETPROBE_ON_RETHOOK
2300 rethook_free(rps[i]->rh);
2301 #else
2302 rps[i]->rph->rp = NULL;
2303 #endif
2304 }
2305 mutex_unlock(&kprobe_mutex);
2306
2307 synchronize_rcu();
2308 for (i = 0; i < num; i++) {
2309 if (rps[i]->kp.addr) {
2310 __unregister_kprobe_bottom(&rps[i]->kp);
2311 #ifndef CONFIG_KRETPROBE_ON_RETHOOK
2312 free_rp_inst(rps[i]);
2313 #endif
2314 }
2315 }
2316 }
2317 EXPORT_SYMBOL_GPL(unregister_kretprobes);
2318
2319 #else /* CONFIG_KRETPROBES */
register_kretprobe(struct kretprobe * rp)2320 int register_kretprobe(struct kretprobe *rp)
2321 {
2322 return -EOPNOTSUPP;
2323 }
2324 EXPORT_SYMBOL_GPL(register_kretprobe);
2325
register_kretprobes(struct kretprobe ** rps,int num)2326 int register_kretprobes(struct kretprobe **rps, int num)
2327 {
2328 return -EOPNOTSUPP;
2329 }
2330 EXPORT_SYMBOL_GPL(register_kretprobes);
2331
unregister_kretprobe(struct kretprobe * rp)2332 void unregister_kretprobe(struct kretprobe *rp)
2333 {
2334 }
2335 EXPORT_SYMBOL_GPL(unregister_kretprobe);
2336
unregister_kretprobes(struct kretprobe ** rps,int num)2337 void unregister_kretprobes(struct kretprobe **rps, int num)
2338 {
2339 }
2340 EXPORT_SYMBOL_GPL(unregister_kretprobes);
2341
pre_handler_kretprobe(struct kprobe * p,struct pt_regs * regs)2342 static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
2343 {
2344 return 0;
2345 }
2346 NOKPROBE_SYMBOL(pre_handler_kretprobe);
2347
2348 #endif /* CONFIG_KRETPROBES */
2349
2350 /* Set the kprobe gone and remove its instruction buffer. */
kill_kprobe(struct kprobe * p)2351 static void kill_kprobe(struct kprobe *p)
2352 {
2353 struct kprobe *kp;
2354
2355 lockdep_assert_held(&kprobe_mutex);
2356
2357 p->flags |= KPROBE_FLAG_GONE;
2358 if (kprobe_aggrprobe(p)) {
2359 /*
2360 * If this is an aggr_kprobe, we have to list all the
2361 * chained probes and mark them GONE.
2362 */
2363 list_for_each_entry(kp, &p->list, list)
2364 kp->flags |= KPROBE_FLAG_GONE;
2365 p->post_handler = NULL;
2366 kill_optimized_kprobe(p);
2367 }
2368 /*
2369 * Here, we can remove insn_slot safely, because no thread calls
2370 * the original probed function (which will be freed soon) any more.
2371 */
2372 arch_remove_kprobe(p);
2373
2374 /*
2375 * The module is going away. We should disarm the kprobe which
2376 * is using ftrace, because ftrace framework is still available at
2377 * 'MODULE_STATE_GOING' notification.
2378 */
2379 if (kprobe_ftrace(p) && !kprobe_disabled(p) && !kprobes_all_disarmed)
2380 disarm_kprobe_ftrace(p);
2381 }
2382
2383 /* Disable one kprobe */
disable_kprobe(struct kprobe * kp)2384 int disable_kprobe(struct kprobe *kp)
2385 {
2386 int ret = 0;
2387 struct kprobe *p;
2388
2389 mutex_lock(&kprobe_mutex);
2390
2391 /* Disable this kprobe */
2392 p = __disable_kprobe(kp);
2393 if (IS_ERR(p))
2394 ret = PTR_ERR(p);
2395
2396 mutex_unlock(&kprobe_mutex);
2397 return ret;
2398 }
2399 EXPORT_SYMBOL_GPL(disable_kprobe);
2400
2401 /* Enable one kprobe */
enable_kprobe(struct kprobe * kp)2402 int enable_kprobe(struct kprobe *kp)
2403 {
2404 int ret = 0;
2405 struct kprobe *p;
2406
2407 mutex_lock(&kprobe_mutex);
2408
2409 /* Check whether specified probe is valid. */
2410 p = __get_valid_kprobe(kp);
2411 if (unlikely(p == NULL)) {
2412 ret = -EINVAL;
2413 goto out;
2414 }
2415
2416 if (kprobe_gone(kp)) {
2417 /* This kprobe has gone, we couldn't enable it. */
2418 ret = -EINVAL;
2419 goto out;
2420 }
2421
2422 if (p != kp)
2423 kp->flags &= ~KPROBE_FLAG_DISABLED;
2424
2425 if (!kprobes_all_disarmed && kprobe_disabled(p)) {
2426 p->flags &= ~KPROBE_FLAG_DISABLED;
2427 ret = arm_kprobe(p);
2428 if (ret)
2429 p->flags |= KPROBE_FLAG_DISABLED;
2430 }
2431 out:
2432 mutex_unlock(&kprobe_mutex);
2433 return ret;
2434 }
2435 EXPORT_SYMBOL_GPL(enable_kprobe);
2436
2437 /* Caller must NOT call this in usual path. This is only for critical case */
dump_kprobe(struct kprobe * kp)2438 void dump_kprobe(struct kprobe *kp)
2439 {
2440 pr_err("Dump kprobe:\n.symbol_name = %s, .offset = %x, .addr = %pS\n",
2441 kp->symbol_name, kp->offset, kp->addr);
2442 }
2443 NOKPROBE_SYMBOL(dump_kprobe);
2444
kprobe_add_ksym_blacklist(unsigned long entry)2445 int kprobe_add_ksym_blacklist(unsigned long entry)
2446 {
2447 struct kprobe_blacklist_entry *ent;
2448 unsigned long offset = 0, size = 0;
2449
2450 if (!kernel_text_address(entry) ||
2451 !kallsyms_lookup_size_offset(entry, &size, &offset))
2452 return -EINVAL;
2453
2454 ent = kmalloc(sizeof(*ent), GFP_KERNEL);
2455 if (!ent)
2456 return -ENOMEM;
2457 ent->start_addr = entry;
2458 ent->end_addr = entry + size;
2459 INIT_LIST_HEAD(&ent->list);
2460 list_add_tail(&ent->list, &kprobe_blacklist);
2461
2462 return (int)size;
2463 }
2464
2465 /* Add all symbols in given area into kprobe blacklist */
kprobe_add_area_blacklist(unsigned long start,unsigned long end)2466 int kprobe_add_area_blacklist(unsigned long start, unsigned long end)
2467 {
2468 unsigned long entry;
2469 int ret = 0;
2470
2471 for (entry = start; entry < end; entry += ret) {
2472 ret = kprobe_add_ksym_blacklist(entry);
2473 if (ret < 0)
2474 return ret;
2475 if (ret == 0) /* In case of alias symbol */
2476 ret = 1;
2477 }
2478 return 0;
2479 }
2480
2481 /* Remove all symbols in given area from kprobe blacklist */
kprobe_remove_area_blacklist(unsigned long start,unsigned long end)2482 static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
2483 {
2484 struct kprobe_blacklist_entry *ent, *n;
2485
2486 list_for_each_entry_safe(ent, n, &kprobe_blacklist, list) {
2487 if (ent->start_addr < start || ent->start_addr >= end)
2488 continue;
2489 list_del(&ent->list);
2490 kfree(ent);
2491 }
2492 }
2493
kprobe_remove_ksym_blacklist(unsigned long entry)2494 static void kprobe_remove_ksym_blacklist(unsigned long entry)
2495 {
2496 kprobe_remove_area_blacklist(entry, entry + 1);
2497 }
2498
arch_kprobe_get_kallsym(unsigned int * symnum,unsigned long * value,char * type,char * sym)2499 int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value,
2500 char *type, char *sym)
2501 {
2502 return -ERANGE;
2503 }
2504
kprobe_get_kallsym(unsigned int symnum,unsigned long * value,char * type,char * sym)2505 int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
2506 char *sym)
2507 {
2508 #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
2509 if (!kprobe_cache_get_kallsym(&kprobe_insn_slots, &symnum, value, type, sym))
2510 return 0;
2511 #ifdef CONFIG_OPTPROBES
2512 if (!kprobe_cache_get_kallsym(&kprobe_optinsn_slots, &symnum, value, type, sym))
2513 return 0;
2514 #endif
2515 #endif
2516 if (!arch_kprobe_get_kallsym(&symnum, value, type, sym))
2517 return 0;
2518 return -ERANGE;
2519 }
2520
arch_populate_kprobe_blacklist(void)2521 int __init __weak arch_populate_kprobe_blacklist(void)
2522 {
2523 return 0;
2524 }
2525
2526 /*
2527 * Lookup and populate the kprobe_blacklist.
2528 *
2529 * Unlike the kretprobe blacklist, we'll need to determine
2530 * the range of addresses that belong to the said functions,
2531 * since a kprobe need not necessarily be at the beginning
2532 * of a function.
2533 */
populate_kprobe_blacklist(unsigned long * start,unsigned long * end)2534 static int __init populate_kprobe_blacklist(unsigned long *start,
2535 unsigned long *end)
2536 {
2537 unsigned long entry;
2538 unsigned long *iter;
2539 int ret;
2540
2541 for (iter = start; iter < end; iter++) {
2542 entry = (unsigned long)dereference_symbol_descriptor((void *)*iter);
2543 ret = kprobe_add_ksym_blacklist(entry);
2544 if (ret == -EINVAL)
2545 continue;
2546 if (ret < 0)
2547 return ret;
2548 }
2549
2550 /* Symbols in '__kprobes_text' are blacklisted */
2551 ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
2552 (unsigned long)__kprobes_text_end);
2553 if (ret)
2554 return ret;
2555
2556 /* Symbols in 'noinstr' section are blacklisted */
2557 ret = kprobe_add_area_blacklist((unsigned long)__noinstr_text_start,
2558 (unsigned long)__noinstr_text_end);
2559
2560 return ret ? : arch_populate_kprobe_blacklist();
2561 }
2562
add_module_kprobe_blacklist(struct module * mod)2563 static void add_module_kprobe_blacklist(struct module *mod)
2564 {
2565 unsigned long start, end;
2566 int i;
2567
2568 if (mod->kprobe_blacklist) {
2569 for (i = 0; i < mod->num_kprobe_blacklist; i++)
2570 kprobe_add_ksym_blacklist(mod->kprobe_blacklist[i]);
2571 }
2572
2573 start = (unsigned long)mod->kprobes_text_start;
2574 if (start) {
2575 end = start + mod->kprobes_text_size;
2576 kprobe_add_area_blacklist(start, end);
2577 }
2578
2579 start = (unsigned long)mod->noinstr_text_start;
2580 if (start) {
2581 end = start + mod->noinstr_text_size;
2582 kprobe_add_area_blacklist(start, end);
2583 }
2584 }
2585
remove_module_kprobe_blacklist(struct module * mod)2586 static void remove_module_kprobe_blacklist(struct module *mod)
2587 {
2588 unsigned long start, end;
2589 int i;
2590
2591 if (mod->kprobe_blacklist) {
2592 for (i = 0; i < mod->num_kprobe_blacklist; i++)
2593 kprobe_remove_ksym_blacklist(mod->kprobe_blacklist[i]);
2594 }
2595
2596 start = (unsigned long)mod->kprobes_text_start;
2597 if (start) {
2598 end = start + mod->kprobes_text_size;
2599 kprobe_remove_area_blacklist(start, end);
2600 }
2601
2602 start = (unsigned long)mod->noinstr_text_start;
2603 if (start) {
2604 end = start + mod->noinstr_text_size;
2605 kprobe_remove_area_blacklist(start, end);
2606 }
2607 }
2608
2609 /* Module notifier call back, checking kprobes on the module */
kprobes_module_callback(struct notifier_block * nb,unsigned long val,void * data)2610 static int kprobes_module_callback(struct notifier_block *nb,
2611 unsigned long val, void *data)
2612 {
2613 struct module *mod = data;
2614 struct hlist_head *head;
2615 struct kprobe *p;
2616 unsigned int i;
2617 int checkcore = (val == MODULE_STATE_GOING);
2618
2619 if (val == MODULE_STATE_COMING) {
2620 mutex_lock(&kprobe_mutex);
2621 add_module_kprobe_blacklist(mod);
2622 mutex_unlock(&kprobe_mutex);
2623 }
2624 if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
2625 return NOTIFY_DONE;
2626
2627 /*
2628 * When 'MODULE_STATE_GOING' was notified, both of module '.text' and
2629 * '.init.text' sections would be freed. When 'MODULE_STATE_LIVE' was
2630 * notified, only '.init.text' section would be freed. We need to
2631 * disable kprobes which have been inserted in the sections.
2632 */
2633 mutex_lock(&kprobe_mutex);
2634 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2635 head = &kprobe_table[i];
2636 hlist_for_each_entry(p, head, hlist)
2637 if (within_module_init((unsigned long)p->addr, mod) ||
2638 (checkcore &&
2639 within_module_core((unsigned long)p->addr, mod))) {
2640 /*
2641 * The vaddr this probe is installed will soon
2642 * be vfreed buy not synced to disk. Hence,
2643 * disarming the breakpoint isn't needed.
2644 *
2645 * Note, this will also move any optimized probes
2646 * that are pending to be removed from their
2647 * corresponding lists to the 'freeing_list' and
2648 * will not be touched by the delayed
2649 * kprobe_optimizer() work handler.
2650 */
2651 kill_kprobe(p);
2652 }
2653 }
2654 if (val == MODULE_STATE_GOING)
2655 remove_module_kprobe_blacklist(mod);
2656 mutex_unlock(&kprobe_mutex);
2657 return NOTIFY_DONE;
2658 }
2659
2660 static struct notifier_block kprobe_module_nb = {
2661 .notifier_call = kprobes_module_callback,
2662 .priority = 0
2663 };
2664
kprobe_free_init_mem(void)2665 void kprobe_free_init_mem(void)
2666 {
2667 void *start = (void *)(&__init_begin);
2668 void *end = (void *)(&__init_end);
2669 struct hlist_head *head;
2670 struct kprobe *p;
2671 int i;
2672
2673 mutex_lock(&kprobe_mutex);
2674
2675 /* Kill all kprobes on initmem because the target code has been freed. */
2676 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2677 head = &kprobe_table[i];
2678 hlist_for_each_entry(p, head, hlist) {
2679 if (start <= (void *)p->addr && (void *)p->addr < end)
2680 kill_kprobe(p);
2681 }
2682 }
2683
2684 mutex_unlock(&kprobe_mutex);
2685 }
2686
init_kprobes(void)2687 static int __init init_kprobes(void)
2688 {
2689 int i, err = 0;
2690
2691 /* FIXME allocate the probe table, currently defined statically */
2692 /* initialize all list heads */
2693 for (i = 0; i < KPROBE_TABLE_SIZE; i++)
2694 INIT_HLIST_HEAD(&kprobe_table[i]);
2695
2696 err = populate_kprobe_blacklist(__start_kprobe_blacklist,
2697 __stop_kprobe_blacklist);
2698 if (err)
2699 pr_err("Failed to populate blacklist (error %d), kprobes not restricted, be careful using them!\n", err);
2700
2701 if (kretprobe_blacklist_size) {
2702 /* lookup the function address from its name */
2703 for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
2704 kretprobe_blacklist[i].addr =
2705 kprobe_lookup_name(kretprobe_blacklist[i].name, 0);
2706 if (!kretprobe_blacklist[i].addr)
2707 pr_err("Failed to lookup symbol '%s' for kretprobe blacklist. Maybe the target function is removed or renamed.\n",
2708 kretprobe_blacklist[i].name);
2709 }
2710 }
2711
2712 /* By default, kprobes are armed */
2713 kprobes_all_disarmed = false;
2714
2715 #if defined(CONFIG_OPTPROBES) && defined(__ARCH_WANT_KPROBES_INSN_SLOT)
2716 /* Init 'kprobe_optinsn_slots' for allocation */
2717 kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
2718 #endif
2719
2720 err = arch_init_kprobes();
2721 if (!err)
2722 err = register_die_notifier(&kprobe_exceptions_nb);
2723 if (!err)
2724 err = register_module_notifier(&kprobe_module_nb);
2725
2726 kprobes_initialized = (err == 0);
2727 kprobe_sysctls_init();
2728 return err;
2729 }
2730 early_initcall(init_kprobes);
2731
2732 #if defined(CONFIG_OPTPROBES)
init_optprobes(void)2733 static int __init init_optprobes(void)
2734 {
2735 /*
2736 * Enable kprobe optimization - this kicks the optimizer which
2737 * depends on synchronize_rcu_tasks() and ksoftirqd, that is
2738 * not spawned in early initcall. So delay the optimization.
2739 */
2740 optimize_all_kprobes();
2741
2742 return 0;
2743 }
2744 subsys_initcall(init_optprobes);
2745 #endif
2746
2747 #ifdef CONFIG_DEBUG_FS
report_probe(struct seq_file * pi,struct kprobe * p,const char * sym,int offset,char * modname,struct kprobe * pp)2748 static void report_probe(struct seq_file *pi, struct kprobe *p,
2749 const char *sym, int offset, char *modname, struct kprobe *pp)
2750 {
2751 char *kprobe_type;
2752 void *addr = p->addr;
2753
2754 if (p->pre_handler == pre_handler_kretprobe)
2755 kprobe_type = "r";
2756 else
2757 kprobe_type = "k";
2758
2759 if (!kallsyms_show_value(pi->file->f_cred))
2760 addr = NULL;
2761
2762 if (sym)
2763 seq_printf(pi, "%px %s %s+0x%x %s ",
2764 addr, kprobe_type, sym, offset,
2765 (modname ? modname : " "));
2766 else /* try to use %pS */
2767 seq_printf(pi, "%px %s %pS ",
2768 addr, kprobe_type, p->addr);
2769
2770 if (!pp)
2771 pp = p;
2772 seq_printf(pi, "%s%s%s%s\n",
2773 (kprobe_gone(p) ? "[GONE]" : ""),
2774 ((kprobe_disabled(p) && !kprobe_gone(p)) ? "[DISABLED]" : ""),
2775 (kprobe_optimized(pp) ? "[OPTIMIZED]" : ""),
2776 (kprobe_ftrace(pp) ? "[FTRACE]" : ""));
2777 }
2778
kprobe_seq_start(struct seq_file * f,loff_t * pos)2779 static void *kprobe_seq_start(struct seq_file *f, loff_t *pos)
2780 {
2781 return (*pos < KPROBE_TABLE_SIZE) ? pos : NULL;
2782 }
2783
kprobe_seq_next(struct seq_file * f,void * v,loff_t * pos)2784 static void *kprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
2785 {
2786 (*pos)++;
2787 if (*pos >= KPROBE_TABLE_SIZE)
2788 return NULL;
2789 return pos;
2790 }
2791
kprobe_seq_stop(struct seq_file * f,void * v)2792 static void kprobe_seq_stop(struct seq_file *f, void *v)
2793 {
2794 /* Nothing to do */
2795 }
2796
show_kprobe_addr(struct seq_file * pi,void * v)2797 static int show_kprobe_addr(struct seq_file *pi, void *v)
2798 {
2799 struct hlist_head *head;
2800 struct kprobe *p, *kp;
2801 const char *sym = NULL;
2802 unsigned int i = *(loff_t *) v;
2803 unsigned long offset = 0;
2804 char *modname, namebuf[KSYM_NAME_LEN];
2805
2806 head = &kprobe_table[i];
2807 preempt_disable();
2808 hlist_for_each_entry_rcu(p, head, hlist) {
2809 sym = kallsyms_lookup((unsigned long)p->addr, NULL,
2810 &offset, &modname, namebuf);
2811 if (kprobe_aggrprobe(p)) {
2812 list_for_each_entry_rcu(kp, &p->list, list)
2813 report_probe(pi, kp, sym, offset, modname, p);
2814 } else
2815 report_probe(pi, p, sym, offset, modname, NULL);
2816 }
2817 preempt_enable();
2818 return 0;
2819 }
2820
2821 static const struct seq_operations kprobes_sops = {
2822 .start = kprobe_seq_start,
2823 .next = kprobe_seq_next,
2824 .stop = kprobe_seq_stop,
2825 .show = show_kprobe_addr
2826 };
2827
2828 DEFINE_SEQ_ATTRIBUTE(kprobes);
2829
2830 /* kprobes/blacklist -- shows which functions can not be probed */
kprobe_blacklist_seq_start(struct seq_file * m,loff_t * pos)2831 static void *kprobe_blacklist_seq_start(struct seq_file *m, loff_t *pos)
2832 {
2833 mutex_lock(&kprobe_mutex);
2834 return seq_list_start(&kprobe_blacklist, *pos);
2835 }
2836
kprobe_blacklist_seq_next(struct seq_file * m,void * v,loff_t * pos)2837 static void *kprobe_blacklist_seq_next(struct seq_file *m, void *v, loff_t *pos)
2838 {
2839 return seq_list_next(v, &kprobe_blacklist, pos);
2840 }
2841
kprobe_blacklist_seq_show(struct seq_file * m,void * v)2842 static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
2843 {
2844 struct kprobe_blacklist_entry *ent =
2845 list_entry(v, struct kprobe_blacklist_entry, list);
2846
2847 /*
2848 * If '/proc/kallsyms' is not showing kernel address, we won't
2849 * show them here either.
2850 */
2851 if (!kallsyms_show_value(m->file->f_cred))
2852 seq_printf(m, "0x%px-0x%px\t%ps\n", NULL, NULL,
2853 (void *)ent->start_addr);
2854 else
2855 seq_printf(m, "0x%px-0x%px\t%ps\n", (void *)ent->start_addr,
2856 (void *)ent->end_addr, (void *)ent->start_addr);
2857 return 0;
2858 }
2859
kprobe_blacklist_seq_stop(struct seq_file * f,void * v)2860 static void kprobe_blacklist_seq_stop(struct seq_file *f, void *v)
2861 {
2862 mutex_unlock(&kprobe_mutex);
2863 }
2864
2865 static const struct seq_operations kprobe_blacklist_sops = {
2866 .start = kprobe_blacklist_seq_start,
2867 .next = kprobe_blacklist_seq_next,
2868 .stop = kprobe_blacklist_seq_stop,
2869 .show = kprobe_blacklist_seq_show,
2870 };
2871 DEFINE_SEQ_ATTRIBUTE(kprobe_blacklist);
2872
arm_all_kprobes(void)2873 static int arm_all_kprobes(void)
2874 {
2875 struct hlist_head *head;
2876 struct kprobe *p;
2877 unsigned int i, total = 0, errors = 0;
2878 int err, ret = 0;
2879
2880 mutex_lock(&kprobe_mutex);
2881
2882 /* If kprobes are armed, just return */
2883 if (!kprobes_all_disarmed)
2884 goto already_enabled;
2885
2886 /*
2887 * optimize_kprobe() called by arm_kprobe() checks
2888 * kprobes_all_disarmed, so set kprobes_all_disarmed before
2889 * arm_kprobe.
2890 */
2891 kprobes_all_disarmed = false;
2892 /* Arming kprobes doesn't optimize kprobe itself */
2893 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2894 head = &kprobe_table[i];
2895 /* Arm all kprobes on a best-effort basis */
2896 hlist_for_each_entry(p, head, hlist) {
2897 if (!kprobe_disabled(p)) {
2898 err = arm_kprobe(p);
2899 if (err) {
2900 errors++;
2901 ret = err;
2902 }
2903 total++;
2904 }
2905 }
2906 }
2907
2908 if (errors)
2909 pr_warn("Kprobes globally enabled, but failed to enable %d out of %d probes. Please check which kprobes are kept disabled via debugfs.\n",
2910 errors, total);
2911 else
2912 pr_info("Kprobes globally enabled\n");
2913
2914 already_enabled:
2915 mutex_unlock(&kprobe_mutex);
2916 return ret;
2917 }
2918
disarm_all_kprobes(void)2919 static int disarm_all_kprobes(void)
2920 {
2921 struct hlist_head *head;
2922 struct kprobe *p;
2923 unsigned int i, total = 0, errors = 0;
2924 int err, ret = 0;
2925
2926 mutex_lock(&kprobe_mutex);
2927
2928 /* If kprobes are already disarmed, just return */
2929 if (kprobes_all_disarmed) {
2930 mutex_unlock(&kprobe_mutex);
2931 return 0;
2932 }
2933
2934 kprobes_all_disarmed = true;
2935
2936 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
2937 head = &kprobe_table[i];
2938 /* Disarm all kprobes on a best-effort basis */
2939 hlist_for_each_entry(p, head, hlist) {
2940 if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p)) {
2941 err = disarm_kprobe(p, false);
2942 if (err) {
2943 errors++;
2944 ret = err;
2945 }
2946 total++;
2947 }
2948 }
2949 }
2950
2951 if (errors)
2952 pr_warn("Kprobes globally disabled, but failed to disable %d out of %d probes. Please check which kprobes are kept enabled via debugfs.\n",
2953 errors, total);
2954 else
2955 pr_info("Kprobes globally disabled\n");
2956
2957 mutex_unlock(&kprobe_mutex);
2958
2959 /* Wait for disarming all kprobes by optimizer */
2960 wait_for_kprobe_optimizer();
2961
2962 return ret;
2963 }
2964
2965 /*
2966 * XXX: The debugfs bool file interface doesn't allow for callbacks
2967 * when the bool state is switched. We can reuse that facility when
2968 * available
2969 */
read_enabled_file_bool(struct file * file,char __user * user_buf,size_t count,loff_t * ppos)2970 static ssize_t read_enabled_file_bool(struct file *file,
2971 char __user *user_buf, size_t count, loff_t *ppos)
2972 {
2973 char buf[3];
2974
2975 if (!kprobes_all_disarmed)
2976 buf[0] = '1';
2977 else
2978 buf[0] = '0';
2979 buf[1] = '\n';
2980 buf[2] = 0x00;
2981 return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
2982 }
2983
write_enabled_file_bool(struct file * file,const char __user * user_buf,size_t count,loff_t * ppos)2984 static ssize_t write_enabled_file_bool(struct file *file,
2985 const char __user *user_buf, size_t count, loff_t *ppos)
2986 {
2987 bool enable;
2988 int ret;
2989
2990 ret = kstrtobool_from_user(user_buf, count, &enable);
2991 if (ret)
2992 return ret;
2993
2994 ret = enable ? arm_all_kprobes() : disarm_all_kprobes();
2995 if (ret)
2996 return ret;
2997
2998 return count;
2999 }
3000
3001 static const struct file_operations fops_kp = {
3002 .read = read_enabled_file_bool,
3003 .write = write_enabled_file_bool,
3004 .llseek = default_llseek,
3005 };
3006
debugfs_kprobe_init(void)3007 static int __init debugfs_kprobe_init(void)
3008 {
3009 struct dentry *dir;
3010
3011 dir = debugfs_create_dir("kprobes", NULL);
3012
3013 debugfs_create_file("list", 0400, dir, NULL, &kprobes_fops);
3014
3015 debugfs_create_file("enabled", 0600, dir, NULL, &fops_kp);
3016
3017 debugfs_create_file("blacklist", 0400, dir, NULL,
3018 &kprobe_blacklist_fops);
3019
3020 return 0;
3021 }
3022
3023 late_initcall(debugfs_kprobe_init);
3024 #endif /* CONFIG_DEBUG_FS */
3025