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/slab.h>
39 #include <linux/module.h>
40 #include <linux/moduleloader.h>
41 #include <asm-generic/sections.h>
42 #include <asm/cacheflush.h>
43 #include <asm/errno.h>
44 #include <asm/kdebug.h>
46 #define KPROBE_HASH_BITS 6
47 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
49 static struct hlist_head kprobe_table
[KPROBE_TABLE_SIZE
];
50 static struct hlist_head kretprobe_inst_table
[KPROBE_TABLE_SIZE
];
52 unsigned int kprobe_cpu
= NR_CPUS
;
53 static DEFINE_SPINLOCK(kprobe_lock
);
54 static struct kprobe
*curr_kprobe
;
57 * kprobe->ainsn.insn points to the copy of the instruction to be
58 * single-stepped. x86_64, POWER4 and above have no-exec support and
59 * stepping on the instruction on a vmalloced/kmalloced/data page
60 * is a recipe for disaster
62 #define INSNS_PER_PAGE (PAGE_SIZE/(MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
64 struct kprobe_insn_page
{
65 struct hlist_node hlist
;
66 kprobe_opcode_t
*insns
; /* Page of instruction slots */
67 char slot_used
[INSNS_PER_PAGE
];
71 static struct hlist_head kprobe_insn_pages
;
74 * get_insn_slot() - Find a slot on an executable page for an instruction.
75 * We allocate an executable page if there's no room on existing ones.
77 kprobe_opcode_t __kprobes
*get_insn_slot(void)
79 struct kprobe_insn_page
*kip
;
80 struct hlist_node
*pos
;
82 hlist_for_each(pos
, &kprobe_insn_pages
) {
83 kip
= hlist_entry(pos
, struct kprobe_insn_page
, hlist
);
84 if (kip
->nused
< INSNS_PER_PAGE
) {
86 for (i
= 0; i
< INSNS_PER_PAGE
; i
++) {
87 if (!kip
->slot_used
[i
]) {
88 kip
->slot_used
[i
] = 1;
90 return kip
->insns
+ (i
* MAX_INSN_SIZE
);
93 /* Surprise! No unused slots. Fix kip->nused. */
94 kip
->nused
= INSNS_PER_PAGE
;
98 /* All out of space. Need to allocate a new page. Use slot 0.*/
99 kip
= kmalloc(sizeof(struct kprobe_insn_page
), GFP_KERNEL
);
105 * Use module_alloc so this page is within +/- 2GB of where the
106 * kernel image and loaded module images reside. This is required
107 * so x86_64 can correctly handle the %rip-relative fixups.
109 kip
->insns
= module_alloc(PAGE_SIZE
);
114 INIT_HLIST_NODE(&kip
->hlist
);
115 hlist_add_head(&kip
->hlist
, &kprobe_insn_pages
);
116 memset(kip
->slot_used
, 0, INSNS_PER_PAGE
);
117 kip
->slot_used
[0] = 1;
122 void __kprobes
free_insn_slot(kprobe_opcode_t
*slot
)
124 struct kprobe_insn_page
*kip
;
125 struct hlist_node
*pos
;
127 hlist_for_each(pos
, &kprobe_insn_pages
) {
128 kip
= hlist_entry(pos
, struct kprobe_insn_page
, hlist
);
129 if (kip
->insns
<= slot
&&
130 slot
< kip
->insns
+ (INSNS_PER_PAGE
* MAX_INSN_SIZE
)) {
131 int i
= (slot
- kip
->insns
) / MAX_INSN_SIZE
;
132 kip
->slot_used
[i
] = 0;
134 if (kip
->nused
== 0) {
136 * Page is no longer in use. Free it unless
137 * it's the last one. We keep the last one
138 * so as not to have to set it up again the
139 * next time somebody inserts a probe.
141 hlist_del(&kip
->hlist
);
142 if (hlist_empty(&kprobe_insn_pages
)) {
143 INIT_HLIST_NODE(&kip
->hlist
);
144 hlist_add_head(&kip
->hlist
,
147 module_free(NULL
, kip
->insns
);
156 /* Locks kprobe: irqs must be disabled */
157 void __kprobes
lock_kprobes(void)
159 unsigned long flags
= 0;
161 /* Avoiding local interrupts to happen right after we take the kprobe_lock
162 * and before we get a chance to update kprobe_cpu, this to prevent
163 * deadlock when we have a kprobe on ISR routine and a kprobe on task
166 local_irq_save(flags
);
168 spin_lock(&kprobe_lock
);
169 kprobe_cpu
= smp_processor_id();
171 local_irq_restore(flags
);
174 void __kprobes
unlock_kprobes(void)
176 unsigned long flags
= 0;
178 /* Avoiding local interrupts to happen right after we update
179 * kprobe_cpu and before we get a a chance to release kprobe_lock,
180 * this to prevent deadlock when we have a kprobe on ISR routine and
181 * a kprobe on task routine
183 local_irq_save(flags
);
185 kprobe_cpu
= NR_CPUS
;
186 spin_unlock(&kprobe_lock
);
188 local_irq_restore(flags
);
191 /* You have to be holding the kprobe_lock */
192 struct kprobe __kprobes
*get_kprobe(void *addr
)
194 struct hlist_head
*head
;
195 struct hlist_node
*node
;
197 head
= &kprobe_table
[hash_ptr(addr
, KPROBE_HASH_BITS
)];
198 hlist_for_each(node
, head
) {
199 struct kprobe
*p
= hlist_entry(node
, struct kprobe
, hlist
);
207 * Aggregate handlers for multiple kprobes support - these handlers
208 * take care of invoking the individual kprobe handlers on p->list
210 static int __kprobes
aggr_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
214 list_for_each_entry(kp
, &p
->list
, list
) {
215 if (kp
->pre_handler
) {
217 if (kp
->pre_handler(kp
, regs
))
225 static void __kprobes
aggr_post_handler(struct kprobe
*p
, struct pt_regs
*regs
,
230 list_for_each_entry(kp
, &p
->list
, list
) {
231 if (kp
->post_handler
) {
233 kp
->post_handler(kp
, regs
, flags
);
240 static int __kprobes
aggr_fault_handler(struct kprobe
*p
, struct pt_regs
*regs
,
244 * if we faulted "during" the execution of a user specified
245 * probe handler, invoke just that probe's fault handler
247 if (curr_kprobe
&& curr_kprobe
->fault_handler
) {
248 if (curr_kprobe
->fault_handler(curr_kprobe
, regs
, trapnr
))
254 static int __kprobes
aggr_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
256 struct kprobe
*kp
= curr_kprobe
;
257 if (curr_kprobe
&& kp
->break_handler
) {
258 if (kp
->break_handler(kp
, regs
)) {
267 struct kretprobe_instance __kprobes
*get_free_rp_inst(struct kretprobe
*rp
)
269 struct hlist_node
*node
;
270 struct kretprobe_instance
*ri
;
271 hlist_for_each_entry(ri
, node
, &rp
->free_instances
, uflist
)
276 static struct kretprobe_instance __kprobes
*get_used_rp_inst(struct kretprobe
279 struct hlist_node
*node
;
280 struct kretprobe_instance
*ri
;
281 hlist_for_each_entry(ri
, node
, &rp
->used_instances
, uflist
)
286 void __kprobes
add_rp_inst(struct kretprobe_instance
*ri
)
289 * Remove rp inst off the free list -
290 * Add it back when probed function returns
292 hlist_del(&ri
->uflist
);
294 /* Add rp inst onto table */
295 INIT_HLIST_NODE(&ri
->hlist
);
296 hlist_add_head(&ri
->hlist
,
297 &kretprobe_inst_table
[hash_ptr(ri
->task
, KPROBE_HASH_BITS
)]);
299 /* Also add this rp inst to the used list. */
300 INIT_HLIST_NODE(&ri
->uflist
);
301 hlist_add_head(&ri
->uflist
, &ri
->rp
->used_instances
);
304 void __kprobes
recycle_rp_inst(struct kretprobe_instance
*ri
)
306 /* remove rp inst off the rprobe_inst_table */
307 hlist_del(&ri
->hlist
);
309 /* remove rp inst off the used list */
310 hlist_del(&ri
->uflist
);
311 /* put rp inst back onto the free list */
312 INIT_HLIST_NODE(&ri
->uflist
);
313 hlist_add_head(&ri
->uflist
, &ri
->rp
->free_instances
);
319 struct hlist_head __kprobes
*kretprobe_inst_table_head(struct task_struct
*tsk
)
321 return &kretprobe_inst_table
[hash_ptr(tsk
, KPROBE_HASH_BITS
)];
325 * This function is called from exit_thread or flush_thread when task tk's
326 * stack is being recycled so that we can recycle any function-return probe
327 * instances associated with this task. These left over instances represent
328 * probed functions that have been called but will never return.
330 void __kprobes
kprobe_flush_task(struct task_struct
*tk
)
332 struct kretprobe_instance
*ri
;
333 struct hlist_head
*head
;
334 struct hlist_node
*node
, *tmp
;
335 unsigned long flags
= 0;
337 spin_lock_irqsave(&kprobe_lock
, flags
);
338 head
= kretprobe_inst_table_head(current
);
339 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
343 spin_unlock_irqrestore(&kprobe_lock
, flags
);
347 * This kprobe pre_handler is registered with every kretprobe. When probe
348 * hits it will set up the return probe.
350 static int __kprobes
pre_handler_kretprobe(struct kprobe
*p
,
351 struct pt_regs
*regs
)
353 struct kretprobe
*rp
= container_of(p
, struct kretprobe
, kp
);
355 /*TODO: consider to only swap the RA after the last pre_handler fired */
356 arch_prepare_kretprobe(rp
, regs
);
360 static inline void free_rp_inst(struct kretprobe
*rp
)
362 struct kretprobe_instance
*ri
;
363 while ((ri
= get_free_rp_inst(rp
)) != NULL
) {
364 hlist_del(&ri
->uflist
);
370 * Keep all fields in the kprobe consistent
372 static inline void copy_kprobe(struct kprobe
*old_p
, struct kprobe
*p
)
374 memcpy(&p
->opcode
, &old_p
->opcode
, sizeof(kprobe_opcode_t
));
375 memcpy(&p
->ainsn
, &old_p
->ainsn
, sizeof(struct arch_specific_insn
));
379 * Add the new probe to old_p->list. Fail if this is the
380 * second jprobe at the address - two jprobes can't coexist
382 static int __kprobes
add_new_kprobe(struct kprobe
*old_p
, struct kprobe
*p
)
386 if (p
->break_handler
) {
387 list_for_each_entry(kp
, &old_p
->list
, list
) {
388 if (kp
->break_handler
)
391 list_add_tail(&p
->list
, &old_p
->list
);
393 list_add(&p
->list
, &old_p
->list
);
398 * Fill in the required fields of the "manager kprobe". Replace the
399 * earlier kprobe in the hlist with the manager kprobe
401 static inline void add_aggr_kprobe(struct kprobe
*ap
, struct kprobe
*p
)
405 ap
->pre_handler
= aggr_pre_handler
;
406 ap
->post_handler
= aggr_post_handler
;
407 ap
->fault_handler
= aggr_fault_handler
;
408 ap
->break_handler
= aggr_break_handler
;
410 INIT_LIST_HEAD(&ap
->list
);
411 list_add(&p
->list
, &ap
->list
);
413 INIT_HLIST_NODE(&ap
->hlist
);
414 hlist_del(&p
->hlist
);
415 hlist_add_head(&ap
->hlist
,
416 &kprobe_table
[hash_ptr(ap
->addr
, KPROBE_HASH_BITS
)]);
420 * This is the second or subsequent kprobe at the address - handle
422 * TODO: Move kcalloc outside the spinlock
424 static int __kprobes
register_aggr_kprobe(struct kprobe
*old_p
,
430 if (old_p
->pre_handler
== aggr_pre_handler
) {
431 copy_kprobe(old_p
, p
);
432 ret
= add_new_kprobe(old_p
, p
);
434 ap
= kcalloc(1, sizeof(struct kprobe
), GFP_ATOMIC
);
437 add_aggr_kprobe(ap
, old_p
);
439 ret
= add_new_kprobe(ap
, p
);
444 /* kprobe removal house-keeping routines */
445 static inline void cleanup_kprobe(struct kprobe
*p
, unsigned long flags
)
447 arch_disarm_kprobe(p
);
448 hlist_del(&p
->hlist
);
449 spin_unlock_irqrestore(&kprobe_lock
, flags
);
450 arch_remove_kprobe(p
);
453 static inline void cleanup_aggr_kprobe(struct kprobe
*old_p
,
454 struct kprobe
*p
, unsigned long flags
)
457 if (list_empty(&old_p
->list
)) {
458 cleanup_kprobe(old_p
, flags
);
461 spin_unlock_irqrestore(&kprobe_lock
, flags
);
464 static int __kprobes
in_kprobes_functions(unsigned long addr
)
466 if (addr
>= (unsigned long)__kprobes_text_start
467 && addr
< (unsigned long)__kprobes_text_end
)
472 int __kprobes
register_kprobe(struct kprobe
*p
)
475 unsigned long flags
= 0;
476 struct kprobe
*old_p
;
478 if ((ret
= in_kprobes_functions((unsigned long) p
->addr
)) != 0)
480 if ((ret
= arch_prepare_kprobe(p
)) != 0)
483 spin_lock_irqsave(&kprobe_lock
, flags
);
484 old_p
= get_kprobe(p
->addr
);
487 ret
= register_aggr_kprobe(old_p
, p
);
492 INIT_HLIST_NODE(&p
->hlist
);
493 hlist_add_head(&p
->hlist
,
494 &kprobe_table
[hash_ptr(p
->addr
, KPROBE_HASH_BITS
)]);
499 spin_unlock_irqrestore(&kprobe_lock
, flags
);
502 arch_remove_kprobe(p
);
506 void __kprobes
unregister_kprobe(struct kprobe
*p
)
509 struct kprobe
*old_p
;
511 spin_lock_irqsave(&kprobe_lock
, flags
);
512 old_p
= get_kprobe(p
->addr
);
514 if (old_p
->pre_handler
== aggr_pre_handler
)
515 cleanup_aggr_kprobe(old_p
, p
, flags
);
517 cleanup_kprobe(p
, flags
);
519 spin_unlock_irqrestore(&kprobe_lock
, flags
);
522 static struct notifier_block kprobe_exceptions_nb
= {
523 .notifier_call
= kprobe_exceptions_notify
,
524 .priority
= 0x7fffffff /* we need to notified first */
527 int __kprobes
register_jprobe(struct jprobe
*jp
)
529 /* Todo: Verify probepoint is a function entry point */
530 jp
->kp
.pre_handler
= setjmp_pre_handler
;
531 jp
->kp
.break_handler
= longjmp_break_handler
;
533 return register_kprobe(&jp
->kp
);
536 void __kprobes
unregister_jprobe(struct jprobe
*jp
)
538 unregister_kprobe(&jp
->kp
);
541 #ifdef ARCH_SUPPORTS_KRETPROBES
543 int __kprobes
register_kretprobe(struct kretprobe
*rp
)
546 struct kretprobe_instance
*inst
;
549 rp
->kp
.pre_handler
= pre_handler_kretprobe
;
551 /* Pre-allocate memory for max kretprobe instances */
552 if (rp
->maxactive
<= 0) {
553 #ifdef CONFIG_PREEMPT
554 rp
->maxactive
= max(10, 2 * NR_CPUS
);
556 rp
->maxactive
= NR_CPUS
;
559 INIT_HLIST_HEAD(&rp
->used_instances
);
560 INIT_HLIST_HEAD(&rp
->free_instances
);
561 for (i
= 0; i
< rp
->maxactive
; i
++) {
562 inst
= kmalloc(sizeof(struct kretprobe_instance
), GFP_KERNEL
);
567 INIT_HLIST_NODE(&inst
->uflist
);
568 hlist_add_head(&inst
->uflist
, &rp
->free_instances
);
572 /* Establish function entry probe point */
573 if ((ret
= register_kprobe(&rp
->kp
)) != 0)
578 #else /* ARCH_SUPPORTS_KRETPROBES */
580 int __kprobes
register_kretprobe(struct kretprobe
*rp
)
585 #endif /* ARCH_SUPPORTS_KRETPROBES */
587 void __kprobes
unregister_kretprobe(struct kretprobe
*rp
)
590 struct kretprobe_instance
*ri
;
592 unregister_kprobe(&rp
->kp
);
594 spin_lock_irqsave(&kprobe_lock
, flags
);
596 while ((ri
= get_used_rp_inst(rp
)) != NULL
) {
598 hlist_del(&ri
->uflist
);
600 spin_unlock_irqrestore(&kprobe_lock
, flags
);
603 static int __init
init_kprobes(void)
607 /* FIXME allocate the probe table, currently defined statically */
608 /* initialize all list heads */
609 for (i
= 0; i
< KPROBE_TABLE_SIZE
; i
++) {
610 INIT_HLIST_HEAD(&kprobe_table
[i
]);
611 INIT_HLIST_HEAD(&kretprobe_inst_table
[i
]);
614 err
= arch_init_kprobes();
616 err
= register_die_notifier(&kprobe_exceptions_nb
);
621 __initcall(init_kprobes
);
623 EXPORT_SYMBOL_GPL(register_kprobe
);
624 EXPORT_SYMBOL_GPL(unregister_kprobe
);
625 EXPORT_SYMBOL_GPL(register_jprobe
);
626 EXPORT_SYMBOL_GPL(unregister_jprobe
);
627 EXPORT_SYMBOL_GPL(jprobe_return
);
628 EXPORT_SYMBOL_GPL(register_kretprobe
);
629 EXPORT_SYMBOL_GPL(unregister_kretprobe
);