2 * Kernel Probes (KProbes)
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19 * Copyright (C) IBM Corporation, 2002, 2004
21 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
22 * Probes initial implementation (includes suggestions from
24 * 2004-Aug Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
25 * hlists and exceptions notifier as suggested by Andi Kleen.
26 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
27 * interface to access function arguments.
28 * 2004-Sep Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
29 * exceptions notifier to be first on the priority list.
30 * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
31 * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
32 * <prasanna@in.ibm.com> added function-return probes.
34 #include <linux/kprobes.h>
35 #include <linux/spinlock.h>
36 #include <linux/hash.h>
37 #include <linux/init.h>
38 #include <linux/module.h>
39 #include <linux/moduleloader.h>
40 #include <asm/cacheflush.h>
41 #include <asm/errno.h>
42 #include <asm/kdebug.h>
44 #define KPROBE_HASH_BITS 6
45 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
47 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
48 static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
50 unsigned int kprobe_cpu = NR_CPUS;
51 static DEFINE_SPINLOCK(kprobe_lock);
52 static struct kprobe *curr_kprobe;
55 * kprobe->ainsn.insn points to the copy of the instruction to be
56 * single-stepped. x86_64, POWER4 and above have no-exec support and
57 * stepping on the instruction on a vmalloced/kmalloced/data page
58 * is a recipe for disaster
60 #define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
62 struct kprobe_insn_page {
63 struct hlist_node hlist;
64 kprobe_opcode_t *insns; /* Page of instruction slots */
65 char slot_used[INSNS_PER_PAGE];
69 static struct hlist_head kprobe_insn_pages;
72 * get_insn_slot() - Find a slot on an executable page for an instruction.
73 * We allocate an executable page if there's no room on existing ones.
75 kprobe_opcode_t *get_insn_slot(void)
77 struct kprobe_insn_page *kip;
78 struct hlist_node *pos;
80 hlist_for_each(pos, &kprobe_insn_pages) {
81 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
82 if (kip->nused < INSNS_PER_PAGE) {
84 for (i = 0; i < INSNS_PER_PAGE; i++) {
85 if (!kip->slot_used[i]) {
86 kip->slot_used[i] = 1;
88 return kip->insns + (i * MAX_INSN_SIZE);
91 /* Surprise! No unused slots. Fix kip->nused. */
92 kip->nused = INSNS_PER_PAGE;
96 /* All out of space. Need to allocate a new page. Use slot 0.*/
97 kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
103 * Use module_alloc so this page is within +/- 2GB of where the
104 * kernel image and loaded module images reside. This is required
105 * so x86_64 can correctly handle the %rip-relative fixups.
107 kip->insns = module_alloc(PAGE_SIZE);
112 INIT_HLIST_NODE(&kip->hlist);
113 hlist_add_head(&kip->hlist, &kprobe_insn_pages);
114 memset(kip->slot_used, 0, INSNS_PER_PAGE);
115 kip->slot_used[0] = 1;
120 void free_insn_slot(kprobe_opcode_t *slot)
122 struct kprobe_insn_page *kip;
123 struct hlist_node *pos;
125 hlist_for_each(pos, &kprobe_insn_pages) {
126 kip = hlist_entry(pos, struct kprobe_insn_page, hlist);
127 if (kip->insns <= slot &&
128 slot < kip->insns + (INSNS_PER_PAGE * MAX_INSN_SIZE)) {
129 int i = (slot - kip->insns) / MAX_INSN_SIZE;
130 kip->slot_used[i] = 0;
132 if (kip->nused == 0) {
134 * Page is no longer in use. Free it unless
135 * it's the last one. We keep the last one
136 * so as not to have to set it up again the
137 * next time somebody inserts a probe.
139 hlist_del(&kip->hlist);
140 if (hlist_empty(&kprobe_insn_pages)) {
141 INIT_HLIST_NODE(&kip->hlist);
142 hlist_add_head(&kip->hlist,
145 module_free(NULL, kip->insns);
154 /* Locks kprobe: irqs must be disabled */
155 void lock_kprobes(void)
157 spin_lock(&kprobe_lock);
158 kprobe_cpu = smp_processor_id();
161 void unlock_kprobes(void)
163 kprobe_cpu = NR_CPUS;
164 spin_unlock(&kprobe_lock);
167 /* You have to be holding the kprobe_lock */
168 struct kprobe *get_kprobe(void *addr)
170 struct hlist_head *head;
171 struct hlist_node *node;
173 head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
174 hlist_for_each(node, head) {
175 struct kprobe *p = hlist_entry(node, struct kprobe, hlist);
183 * Aggregate handlers for multiple kprobes support - these handlers
184 * take care of invoking the individual kprobe handlers on p->list
186 static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
190 list_for_each_entry(kp, &p->list, list) {
191 if (kp->pre_handler) {
193 if (kp->pre_handler(kp, regs))
201 static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
206 list_for_each_entry(kp, &p->list, list) {
207 if (kp->post_handler) {
209 kp->post_handler(kp, regs, flags);
216 static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
220 * if we faulted "during" the execution of a user specified
221 * probe handler, invoke just that probe's fault handler
223 if (curr_kprobe && curr_kprobe->fault_handler) {
224 if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr))
230 static int aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
232 struct kprobe *kp = curr_kprobe;
233 if (curr_kprobe && kp->break_handler) {
234 if (kp->break_handler(kp, regs)) {
243 struct kprobe trampoline_p = {
244 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
245 .pre_handler = trampoline_probe_handler,
246 .post_handler = trampoline_post_handler
249 struct kretprobe_instance *get_free_rp_inst(struct kretprobe *rp)
251 struct hlist_node *node;
252 struct kretprobe_instance *ri;
253 hlist_for_each_entry(ri, node, &rp->free_instances, uflist)
258 static struct kretprobe_instance *get_used_rp_inst(struct kretprobe *rp)
260 struct hlist_node *node;
261 struct kretprobe_instance *ri;
262 hlist_for_each_entry(ri, node, &rp->used_instances, uflist)
267 struct kretprobe_instance *get_rp_inst(void *sara)
269 struct hlist_head *head;
270 struct hlist_node *node;
271 struct task_struct *tsk;
272 struct kretprobe_instance *ri;
274 tsk = arch_get_kprobe_task(sara);
275 head = &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
276 hlist_for_each_entry(ri, node, head, hlist) {
277 if (ri->stack_addr == sara)
283 void add_rp_inst(struct kretprobe_instance *ri)
285 struct task_struct *tsk;
287 * Remove rp inst off the free list -
288 * Add it back when probed function returns
290 hlist_del(&ri->uflist);
291 tsk = arch_get_kprobe_task(ri->stack_addr);
292 /* Add rp inst onto table */
293 INIT_HLIST_NODE(&ri->hlist);
294 hlist_add_head(&ri->hlist,
295 &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)]);
297 /* Also add this rp inst to the used list. */
298 INIT_HLIST_NODE(&ri->uflist);
299 hlist_add_head(&ri->uflist, &ri->rp->used_instances);
302 void recycle_rp_inst(struct kretprobe_instance *ri)
304 /* remove rp inst off the rprobe_inst_table */
305 hlist_del(&ri->hlist);
307 /* remove rp inst off the used list */
308 hlist_del(&ri->uflist);
309 /* put rp inst back onto the free list */
310 INIT_HLIST_NODE(&ri->uflist);
311 hlist_add_head(&ri->uflist, &ri->rp->free_instances);
317 struct hlist_head * kretprobe_inst_table_head(struct task_struct *tsk)
319 return &kretprobe_inst_table[hash_ptr(tsk, KPROBE_HASH_BITS)];
322 struct kretprobe_instance *get_rp_inst_tsk(struct task_struct *tk)
324 struct task_struct *tsk;
325 struct hlist_head *head;
326 struct hlist_node *node;
327 struct kretprobe_instance *ri;
329 head = &kretprobe_inst_table[hash_ptr(tk, KPROBE_HASH_BITS)];
331 hlist_for_each_entry(ri, node, head, hlist) {
332 tsk = arch_get_kprobe_task(ri->stack_addr);
340 * This function is called from do_exit or do_execv when task tk's stack is
341 * about to be recycled. Recycle any function-return probe instances
342 * associated with this task. These represent probed functions that have
343 * been called but may never return.
345 void kprobe_flush_task(struct task_struct *tk)
347 unsigned long flags = 0;
348 spin_lock_irqsave(&kprobe_lock, flags);
349 arch_kprobe_flush_task(tk);
350 spin_unlock_irqrestore(&kprobe_lock, flags);
354 * This kprobe pre_handler is registered with every kretprobe. When probe
355 * hits it will set up the return probe.
357 static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
359 struct kretprobe *rp = container_of(p, struct kretprobe, kp);
361 /*TODO: consider to only swap the RA after the last pre_handler fired */
362 arch_prepare_kretprobe(rp, regs);
366 static inline void free_rp_inst(struct kretprobe *rp)
368 struct kretprobe_instance *ri;
369 while ((ri = get_free_rp_inst(rp)) != NULL) {
370 hlist_del(&ri->uflist);
376 * Keep all fields in the kprobe consistent
378 static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
380 memcpy(&p->opcode, &old_p->opcode, sizeof(kprobe_opcode_t));
381 memcpy(&p->ainsn, &old_p->ainsn, sizeof(struct arch_specific_insn));
385 * Add the new probe to old_p->list. Fail if this is the
386 * second jprobe at the address - two jprobes can't coexist
388 static int add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
392 if (p->break_handler) {
393 list_for_each_entry(kp, &old_p->list, list) {
394 if (kp->break_handler)
397 list_add_tail(&p->list, &old_p->list);
399 list_add(&p->list, &old_p->list);
404 * Fill in the required fields of the "manager kprobe". Replace the
405 * earlier kprobe in the hlist with the manager kprobe
407 static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
411 ap->pre_handler = aggr_pre_handler;
412 ap->post_handler = aggr_post_handler;
413 ap->fault_handler = aggr_fault_handler;
414 ap->break_handler = aggr_break_handler;
416 INIT_LIST_HEAD(&ap->list);
417 list_add(&p->list, &ap->list);
419 INIT_HLIST_NODE(&ap->hlist);
420 hlist_del(&p->hlist);
421 hlist_add_head(&ap->hlist,
422 &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
426 * This is the second or subsequent kprobe at the address - handle
428 * TODO: Move kcalloc outside the spinlock
430 static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p)
435 if (old_p->pre_handler == aggr_pre_handler) {
436 copy_kprobe(old_p, p);
437 ret = add_new_kprobe(old_p, p);
439 ap = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC);
442 add_aggr_kprobe(ap, old_p);
444 ret = add_new_kprobe(ap, p);
449 /* kprobe removal house-keeping routines */
450 static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags)
452 arch_disarm_kprobe(p);
453 hlist_del(&p->hlist);
454 spin_unlock_irqrestore(&kprobe_lock, flags);
455 arch_remove_kprobe(p);
458 static inline void cleanup_aggr_kprobe(struct kprobe *old_p,
459 struct kprobe *p, unsigned long flags)
462 if (list_empty(&old_p->list)) {
463 cleanup_kprobe(old_p, flags);
466 spin_unlock_irqrestore(&kprobe_lock, flags);
469 int register_kprobe(struct kprobe *p)
472 unsigned long flags = 0;
473 struct kprobe *old_p;
475 if ((ret = arch_prepare_kprobe(p)) != 0) {
478 spin_lock_irqsave(&kprobe_lock, flags);
479 old_p = get_kprobe(p->addr);
482 ret = register_aggr_kprobe(old_p, p);
487 INIT_HLIST_NODE(&p->hlist);
488 hlist_add_head(&p->hlist,
489 &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
494 spin_unlock_irqrestore(&kprobe_lock, flags);
497 arch_remove_kprobe(p);
501 void unregister_kprobe(struct kprobe *p)
504 struct kprobe *old_p;
506 spin_lock_irqsave(&kprobe_lock, flags);
507 old_p = get_kprobe(p->addr);
509 if (old_p->pre_handler == aggr_pre_handler)
510 cleanup_aggr_kprobe(old_p, p, flags);
512 cleanup_kprobe(p, flags);
514 spin_unlock_irqrestore(&kprobe_lock, flags);
517 static struct notifier_block kprobe_exceptions_nb = {
518 .notifier_call = kprobe_exceptions_notify,
519 .priority = 0x7fffffff /* we need to notified first */
522 int register_jprobe(struct jprobe *jp)
524 /* Todo: Verify probepoint is a function entry point */
525 jp->kp.pre_handler = setjmp_pre_handler;
526 jp->kp.break_handler = longjmp_break_handler;
528 return register_kprobe(&jp->kp);
531 void unregister_jprobe(struct jprobe *jp)
533 unregister_kprobe(&jp->kp);
536 #ifdef ARCH_SUPPORTS_KRETPROBES
538 int register_kretprobe(struct kretprobe *rp)
541 struct kretprobe_instance *inst;
544 rp->kp.pre_handler = pre_handler_kretprobe;
546 /* Pre-allocate memory for max kretprobe instances */
547 if (rp->maxactive <= 0) {
548 #ifdef CONFIG_PREEMPT
549 rp->maxactive = max(10, 2 * NR_CPUS);
551 rp->maxactive = NR_CPUS;
554 INIT_HLIST_HEAD(&rp->used_instances);
555 INIT_HLIST_HEAD(&rp->free_instances);
556 for (i = 0; i < rp->maxactive; i++) {
557 inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
562 INIT_HLIST_NODE(&inst->uflist);
563 hlist_add_head(&inst->uflist, &rp->free_instances);
567 /* Establish function entry probe point */
568 if ((ret = register_kprobe(&rp->kp)) != 0)
573 #else /* ARCH_SUPPORTS_KRETPROBES */
575 int register_kretprobe(struct kretprobe *rp)
580 #endif /* ARCH_SUPPORTS_KRETPROBES */
582 void unregister_kretprobe(struct kretprobe *rp)
585 struct kretprobe_instance *ri;
587 unregister_kprobe(&rp->kp);
589 spin_lock_irqsave(&kprobe_lock, flags);
591 while ((ri = get_used_rp_inst(rp)) != NULL) {
593 hlist_del(&ri->uflist);
595 spin_unlock_irqrestore(&kprobe_lock, flags);
598 static int __init init_kprobes(void)
602 /* FIXME allocate the probe table, currently defined statically */
603 /* initialize all list heads */
604 for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
605 INIT_HLIST_HEAD(&kprobe_table[i]);
606 INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
609 err = register_die_notifier(&kprobe_exceptions_nb);
610 /* Register the trampoline probe for return probe */
611 register_kprobe(&trampoline_p);
615 __initcall(init_kprobes);
617 EXPORT_SYMBOL_GPL(register_kprobe);
618 EXPORT_SYMBOL_GPL(unregister_kprobe);
619 EXPORT_SYMBOL_GPL(register_jprobe);
620 EXPORT_SYMBOL_GPL(unregister_jprobe);
621 EXPORT_SYMBOL_GPL(jprobe_return);
622 EXPORT_SYMBOL_GPL(register_kretprobe);
623 EXPORT_SYMBOL_GPL(unregister_kretprobe);