2 * Kernel Probes (KProbes)
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 * Copyright (C) IBM Corporation, 2002, 2004
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
23 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
24 * interface to access function arguments.
25 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
29 #include <linux/kprobes.h>
30 #include <linux/ptrace.h>
31 #include <linux/preempt.h>
32 #include <linux/module.h>
33 #include <asm/cacheflush.h>
34 #include <asm/kdebug.h>
35 #include <asm/sstep.h>
36 #include <asm/uaccess.h>
38 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
39 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
41 int __kprobes
arch_prepare_kprobe(struct kprobe
*p
)
44 kprobe_opcode_t insn
= *p
->addr
;
46 if ((unsigned long)p
->addr
& 0x03) {
47 printk("Attempt to register kprobe at an unaligned address\n");
49 } else if (IS_MTMSRD(insn
) || IS_RFID(insn
) || IS_RFI(insn
)) {
50 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
54 /* insn must be on a special executable page on ppc64 */
56 p
->ainsn
.insn
= get_insn_slot();
62 memcpy(p
->ainsn
.insn
, p
->addr
,
63 MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
65 flush_icache_range((unsigned long)p
->ainsn
.insn
,
66 (unsigned long)p
->ainsn
.insn
+ sizeof(kprobe_opcode_t
));
69 p
->ainsn
.boostable
= 0;
73 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
75 *p
->addr
= BREAKPOINT_INSTRUCTION
;
76 flush_icache_range((unsigned long) p
->addr
,
77 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
80 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
83 flush_icache_range((unsigned long) p
->addr
,
84 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
87 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
89 mutex_lock(&kprobe_mutex
);
90 free_insn_slot(p
->ainsn
.insn
, 0);
91 mutex_unlock(&kprobe_mutex
);
94 static void __kprobes
prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
99 * On powerpc we should single step on the original
100 * instruction even if the probed insn is a trap
101 * variant as values in regs could play a part in
102 * if the trap is taken or not
104 regs
->nip
= (unsigned long)p
->ainsn
.insn
;
107 static void __kprobes
save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
109 kcb
->prev_kprobe
.kp
= kprobe_running();
110 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
111 kcb
->prev_kprobe
.saved_msr
= kcb
->kprobe_saved_msr
;
114 static void __kprobes
restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
116 __get_cpu_var(current_kprobe
) = kcb
->prev_kprobe
.kp
;
117 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
118 kcb
->kprobe_saved_msr
= kcb
->prev_kprobe
.saved_msr
;
121 static void __kprobes
set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
122 struct kprobe_ctlblk
*kcb
)
124 __get_cpu_var(current_kprobe
) = p
;
125 kcb
->kprobe_saved_msr
= regs
->msr
;
128 /* Called with kretprobe_lock held */
129 void __kprobes
arch_prepare_kretprobe(struct kretprobe
*rp
,
130 struct pt_regs
*regs
)
132 struct kretprobe_instance
*ri
;
134 if ((ri
= get_free_rp_inst(rp
)) != NULL
) {
137 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->link
;
139 /* Replace the return addr with trampoline addr */
140 regs
->link
= (unsigned long)kretprobe_trampoline
;
147 static int __kprobes
kprobe_handler(struct pt_regs
*regs
)
151 unsigned int *addr
= (unsigned int *)regs
->nip
;
152 struct kprobe_ctlblk
*kcb
;
155 * We don't want to be preempted for the entire
156 * duration of kprobe processing
159 kcb
= get_kprobe_ctlblk();
161 /* Check we're not actually recursing */
162 if (kprobe_running()) {
163 p
= get_kprobe(addr
);
165 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
166 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
168 regs
->msr
&= ~MSR_SE
;
169 regs
->msr
|= kcb
->kprobe_saved_msr
;
172 /* We have reentered the kprobe_handler(), since
173 * another probe was hit while within the handler.
174 * We here save the original kprobes variables and
175 * just single step on the instruction of the new probe
176 * without calling any user handlers.
178 save_previous_kprobe(kcb
);
179 set_current_kprobe(p
, regs
, kcb
);
180 kcb
->kprobe_saved_msr
= regs
->msr
;
181 kprobes_inc_nmissed_count(p
);
182 prepare_singlestep(p
, regs
);
183 kcb
->kprobe_status
= KPROBE_REENTER
;
186 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
187 /* If trap variant, then it belongs not to us */
188 kprobe_opcode_t cur_insn
= *addr
;
189 if (is_trap(cur_insn
))
191 /* The breakpoint instruction was removed by
192 * another cpu right after we hit, no further
193 * handling of this interrupt is appropriate
198 p
= __get_cpu_var(current_kprobe
);
199 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
206 p
= get_kprobe(addr
);
208 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
210 * PowerPC has multiple variants of the "trap"
211 * instruction. If the current instruction is a
212 * trap variant, it could belong to someone else
214 kprobe_opcode_t cur_insn
= *addr
;
215 if (is_trap(cur_insn
))
218 * The breakpoint instruction was removed right
219 * after we hit it. Another cpu has removed
220 * either a probepoint or a debugger breakpoint
221 * at this address. In either case, no further
222 * handling of this interrupt is appropriate.
226 /* Not one of ours: let kernel handle it */
230 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
231 set_current_kprobe(p
, regs
, kcb
);
232 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
233 /* handler has already set things up, so skip ss setup */
237 if (p
->ainsn
.boostable
>= 0) {
238 unsigned int insn
= *p
->ainsn
.insn
;
240 /* regs->nip is also adjusted if emulate_step returns 1 */
241 ret
= emulate_step(regs
, insn
);
244 * Once this instruction has been boosted
245 * successfully, set the boostable flag
247 if (unlikely(p
->ainsn
.boostable
== 0))
248 p
->ainsn
.boostable
= 1;
251 p
->post_handler(p
, regs
, 0);
253 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
254 reset_current_kprobe();
255 preempt_enable_no_resched();
257 } else if (ret
< 0) {
259 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
260 * So, we should never get here... but, its still
261 * good to catch them, just in case...
263 printk("Can't step on instruction %x\n", insn
);
266 /* This instruction can't be boosted */
267 p
->ainsn
.boostable
= -1;
269 prepare_singlestep(p
, regs
);
270 kcb
->kprobe_status
= KPROBE_HIT_SS
;
274 preempt_enable_no_resched();
279 * Function return probe trampoline:
280 * - init_kprobes() establishes a probepoint here
281 * - When the probed function returns, this probe
282 * causes the handlers to fire
284 void kretprobe_trampoline_holder(void)
286 asm volatile(".global kretprobe_trampoline\n"
287 "kretprobe_trampoline:\n"
292 * Called when the probe at kretprobe trampoline is hit
294 int __kprobes
trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
296 struct kretprobe_instance
*ri
= NULL
;
297 struct hlist_head
*head
, empty_rp
;
298 struct hlist_node
*node
, *tmp
;
299 unsigned long flags
, orig_ret_address
= 0;
300 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
302 INIT_HLIST_HEAD(&empty_rp
);
303 spin_lock_irqsave(&kretprobe_lock
, flags
);
304 head
= kretprobe_inst_table_head(current
);
307 * It is possible to have multiple instances associated with a given
308 * task either because an multiple functions in the call path
309 * have a return probe installed on them, and/or more then one return
310 * return probe was registered for a target function.
312 * We can handle this because:
313 * - instances are always inserted at the head of the list
314 * - when multiple return probes are registered for the same
315 * function, the first instance's ret_addr will point to the
316 * real return address, and all the rest will point to
317 * kretprobe_trampoline
319 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
320 if (ri
->task
!= current
)
321 /* another task is sharing our hash bucket */
324 if (ri
->rp
&& ri
->rp
->handler
)
325 ri
->rp
->handler(ri
, regs
);
327 orig_ret_address
= (unsigned long)ri
->ret_addr
;
328 recycle_rp_inst(ri
, &empty_rp
);
330 if (orig_ret_address
!= trampoline_address
)
332 * This is the real return address. Any other
333 * instances associated with this task are for
334 * other calls deeper on the call stack
339 BUG_ON(!orig_ret_address
|| (orig_ret_address
== trampoline_address
));
340 regs
->nip
= orig_ret_address
;
342 reset_current_kprobe();
343 spin_unlock_irqrestore(&kretprobe_lock
, flags
);
344 preempt_enable_no_resched();
346 hlist_for_each_entry_safe(ri
, node
, tmp
, &empty_rp
, hlist
) {
347 hlist_del(&ri
->hlist
);
351 * By returning a non-zero value, we are telling
352 * kprobe_handler() that we don't want the post_handler
353 * to run (and have re-enabled preemption)
359 * Called after single-stepping. p->addr is the address of the
360 * instruction whose first byte has been replaced by the "breakpoint"
361 * instruction. To avoid the SMP problems that can occur when we
362 * temporarily put back the original opcode to single-step, we
363 * single-stepped a copy of the instruction. The address of this
364 * copy is p->ainsn.insn.
366 static void __kprobes
resume_execution(struct kprobe
*p
, struct pt_regs
*regs
)
369 unsigned int insn
= *p
->ainsn
.insn
;
371 regs
->nip
= (unsigned long)p
->addr
;
372 ret
= emulate_step(regs
, insn
);
374 regs
->nip
= (unsigned long)p
->addr
+ 4;
377 static int __kprobes
post_kprobe_handler(struct pt_regs
*regs
)
379 struct kprobe
*cur
= kprobe_running();
380 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
385 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
386 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
387 cur
->post_handler(cur
, regs
, 0);
390 resume_execution(cur
, regs
);
391 regs
->msr
|= kcb
->kprobe_saved_msr
;
393 /*Restore back the original saved kprobes variables and continue. */
394 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
395 restore_previous_kprobe(kcb
);
398 reset_current_kprobe();
400 preempt_enable_no_resched();
403 * if somebody else is singlestepping across a probe point, msr
404 * will have SE set, in which case, continue the remaining processing
405 * of do_debug, as if this is not a probe hit.
407 if (regs
->msr
& MSR_SE
)
413 static int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
415 struct kprobe
*cur
= kprobe_running();
416 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
417 const struct exception_table_entry
*entry
;
419 switch(kcb
->kprobe_status
) {
423 * We are here because the instruction being single
424 * stepped caused a page fault. We reset the current
425 * kprobe and the nip points back to the probe address
426 * and allow the page fault handler to continue as a
429 regs
->nip
= (unsigned long)cur
->addr
;
430 regs
->msr
&= ~MSR_SE
;
431 regs
->msr
|= kcb
->kprobe_saved_msr
;
432 if (kcb
->kprobe_status
== KPROBE_REENTER
)
433 restore_previous_kprobe(kcb
);
435 reset_current_kprobe();
436 preempt_enable_no_resched();
438 case KPROBE_HIT_ACTIVE
:
439 case KPROBE_HIT_SSDONE
:
441 * We increment the nmissed count for accounting,
442 * we can also use npre/npostfault count for accouting
443 * these specific fault cases.
445 kprobes_inc_nmissed_count(cur
);
448 * We come here because instructions in the pre/post
449 * handler caused the page_fault, this could happen
450 * if handler tries to access user space by
451 * copy_from_user(), get_user() etc. Let the
452 * user-specified handler try to fix it first.
454 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
458 * In case the user-specified fault handler returned
459 * zero, try to fix up.
461 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
462 regs
->nip
= entry
->fixup
;
467 * fixup_exception() could not handle it,
468 * Let do_page_fault() fix it.
478 * Wrapper routine to for handling exceptions.
480 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
481 unsigned long val
, void *data
)
483 struct die_args
*args
= (struct die_args
*)data
;
484 int ret
= NOTIFY_DONE
;
486 if (args
->regs
&& user_mode(args
->regs
))
491 if (kprobe_handler(args
->regs
))
495 if (post_kprobe_handler(args
->regs
))
499 /* kprobe_running() needs smp_processor_id() */
501 if (kprobe_running() &&
502 kprobe_fault_handler(args
->regs
, args
->trapnr
))
512 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
514 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
515 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
517 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
519 /* setup return addr to the jprobe handler routine */
521 regs
->nip
= (unsigned long)(((func_descr_t
*)jp
->entry
)->entry
);
522 regs
->gpr
[2] = (unsigned long)(((func_descr_t
*)jp
->entry
)->toc
);
524 regs
->nip
= (unsigned long)jp
->entry
;
530 void __kprobes
jprobe_return(void)
532 asm volatile("trap" ::: "memory");
535 void __kprobes
jprobe_return_end(void)
539 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
541 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
544 * FIXME - we should ideally be validating that we got here 'cos
545 * of the "trap" in jprobe_return() above, before restoring the
548 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
549 preempt_enable_no_resched();
553 static struct kprobe trampoline_p
= {
554 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
555 .pre_handler
= trampoline_probe_handler
558 int __init
arch_init_kprobes(void)
560 return register_kprobe(&trampoline_p
);