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
, MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
64 flush_icache_range((unsigned long)p
->ainsn
.insn
,
65 (unsigned long)p
->ainsn
.insn
+ sizeof(kprobe_opcode_t
));
71 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
73 *p
->addr
= BREAKPOINT_INSTRUCTION
;
74 flush_icache_range((unsigned long) p
->addr
,
75 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
78 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
81 flush_icache_range((unsigned long) p
->addr
,
82 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
85 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
87 mutex_lock(&kprobe_mutex
);
88 free_insn_slot(p
->ainsn
.insn
, 0);
89 mutex_unlock(&kprobe_mutex
);
92 static void __kprobes
prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
97 * On powerpc we should single step on the original
98 * instruction even if the probed insn is a trap
99 * variant as values in regs could play a part in
100 * if the trap is taken or not
102 regs
->nip
= (unsigned long)p
->ainsn
.insn
;
105 static void __kprobes
save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
107 kcb
->prev_kprobe
.kp
= kprobe_running();
108 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
109 kcb
->prev_kprobe
.saved_msr
= kcb
->kprobe_saved_msr
;
112 static void __kprobes
restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
114 __get_cpu_var(current_kprobe
) = kcb
->prev_kprobe
.kp
;
115 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
116 kcb
->kprobe_saved_msr
= kcb
->prev_kprobe
.saved_msr
;
119 static void __kprobes
set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
120 struct kprobe_ctlblk
*kcb
)
122 __get_cpu_var(current_kprobe
) = p
;
123 kcb
->kprobe_saved_msr
= regs
->msr
;
126 /* Called with kretprobe_lock held */
127 void __kprobes
arch_prepare_kretprobe(struct kretprobe
*rp
,
128 struct pt_regs
*regs
)
130 struct kretprobe_instance
*ri
;
132 if ((ri
= get_free_rp_inst(rp
)) != NULL
) {
135 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->link
;
137 /* Replace the return addr with trampoline addr */
138 regs
->link
= (unsigned long)kretprobe_trampoline
;
145 static int __kprobes
kprobe_handler(struct pt_regs
*regs
)
149 unsigned int *addr
= (unsigned int *)regs
->nip
;
150 struct kprobe_ctlblk
*kcb
;
153 * We don't want to be preempted for the entire
154 * duration of kprobe processing
157 kcb
= get_kprobe_ctlblk();
159 /* Check we're not actually recursing */
160 if (kprobe_running()) {
161 p
= get_kprobe(addr
);
163 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
164 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
166 regs
->msr
&= ~MSR_SE
;
167 regs
->msr
|= kcb
->kprobe_saved_msr
;
170 /* We have reentered the kprobe_handler(), since
171 * another probe was hit while within the handler.
172 * We here save the original kprobes variables and
173 * just single step on the instruction of the new probe
174 * without calling any user handlers.
176 save_previous_kprobe(kcb
);
177 set_current_kprobe(p
, regs
, kcb
);
178 kcb
->kprobe_saved_msr
= regs
->msr
;
179 kprobes_inc_nmissed_count(p
);
180 prepare_singlestep(p
, regs
);
181 kcb
->kprobe_status
= KPROBE_REENTER
;
184 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
185 /* If trap variant, then it belongs not to us */
186 kprobe_opcode_t cur_insn
= *addr
;
187 if (is_trap(cur_insn
))
189 /* The breakpoint instruction was removed by
190 * another cpu right after we hit, no further
191 * handling of this interrupt is appropriate
196 p
= __get_cpu_var(current_kprobe
);
197 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
204 p
= get_kprobe(addr
);
206 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
208 * PowerPC has multiple variants of the "trap"
209 * instruction. If the current instruction is a
210 * trap variant, it could belong to someone else
212 kprobe_opcode_t cur_insn
= *addr
;
213 if (is_trap(cur_insn
))
216 * The breakpoint instruction was removed right
217 * after we hit it. Another cpu has removed
218 * either a probepoint or a debugger breakpoint
219 * at this address. In either case, no further
220 * handling of this interrupt is appropriate.
224 /* Not one of ours: let kernel handle it */
228 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
229 set_current_kprobe(p
, regs
, kcb
);
230 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
231 /* handler has already set things up, so skip ss setup */
235 prepare_singlestep(p
, regs
);
236 kcb
->kprobe_status
= KPROBE_HIT_SS
;
240 preempt_enable_no_resched();
245 * Function return probe trampoline:
246 * - init_kprobes() establishes a probepoint here
247 * - When the probed function returns, this probe
248 * causes the handlers to fire
250 void kretprobe_trampoline_holder(void)
252 asm volatile(".global kretprobe_trampoline\n"
253 "kretprobe_trampoline:\n"
258 * Called when the probe at kretprobe trampoline is hit
260 int __kprobes
trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
262 struct kretprobe_instance
*ri
= NULL
;
263 struct hlist_head
*head
, empty_rp
;
264 struct hlist_node
*node
, *tmp
;
265 unsigned long flags
, orig_ret_address
= 0;
266 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
268 INIT_HLIST_HEAD(&empty_rp
);
269 spin_lock_irqsave(&kretprobe_lock
, flags
);
270 head
= kretprobe_inst_table_head(current
);
273 * It is possible to have multiple instances associated with a given
274 * task either because an multiple functions in the call path
275 * have a return probe installed on them, and/or more then one return
276 * return probe was registered for a target function.
278 * We can handle this because:
279 * - instances are always inserted at the head of the list
280 * - when multiple return probes are registered for the same
281 * function, the first instance's ret_addr will point to the
282 * real return address, and all the rest will point to
283 * kretprobe_trampoline
285 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
286 if (ri
->task
!= current
)
287 /* another task is sharing our hash bucket */
290 if (ri
->rp
&& ri
->rp
->handler
)
291 ri
->rp
->handler(ri
, regs
);
293 orig_ret_address
= (unsigned long)ri
->ret_addr
;
294 recycle_rp_inst(ri
, &empty_rp
);
296 if (orig_ret_address
!= trampoline_address
)
298 * This is the real return address. Any other
299 * instances associated with this task are for
300 * other calls deeper on the call stack
305 BUG_ON(!orig_ret_address
|| (orig_ret_address
== trampoline_address
));
306 regs
->nip
= orig_ret_address
;
308 reset_current_kprobe();
309 spin_unlock_irqrestore(&kretprobe_lock
, flags
);
310 preempt_enable_no_resched();
312 hlist_for_each_entry_safe(ri
, node
, tmp
, &empty_rp
, hlist
) {
313 hlist_del(&ri
->hlist
);
317 * By returning a non-zero value, we are telling
318 * kprobe_handler() that we don't want the post_handler
319 * to run (and have re-enabled preemption)
325 * Called after single-stepping. p->addr is the address of the
326 * instruction whose first byte has been replaced by the "breakpoint"
327 * instruction. To avoid the SMP problems that can occur when we
328 * temporarily put back the original opcode to single-step, we
329 * single-stepped a copy of the instruction. The address of this
330 * copy is p->ainsn.insn.
332 static void __kprobes
resume_execution(struct kprobe
*p
, struct pt_regs
*regs
)
335 unsigned int insn
= *p
->ainsn
.insn
;
337 regs
->nip
= (unsigned long)p
->addr
;
338 ret
= emulate_step(regs
, insn
);
340 regs
->nip
= (unsigned long)p
->addr
+ 4;
343 static int __kprobes
post_kprobe_handler(struct pt_regs
*regs
)
345 struct kprobe
*cur
= kprobe_running();
346 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
351 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
352 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
353 cur
->post_handler(cur
, regs
, 0);
356 resume_execution(cur
, regs
);
357 regs
->msr
|= kcb
->kprobe_saved_msr
;
359 /*Restore back the original saved kprobes variables and continue. */
360 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
361 restore_previous_kprobe(kcb
);
364 reset_current_kprobe();
366 preempt_enable_no_resched();
369 * if somebody else is singlestepping across a probe point, msr
370 * will have SE set, in which case, continue the remaining processing
371 * of do_debug, as if this is not a probe hit.
373 if (regs
->msr
& MSR_SE
)
379 static int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
381 struct kprobe
*cur
= kprobe_running();
382 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
383 const struct exception_table_entry
*entry
;
385 switch(kcb
->kprobe_status
) {
389 * We are here because the instruction being single
390 * stepped caused a page fault. We reset the current
391 * kprobe and the nip points back to the probe address
392 * and allow the page fault handler to continue as a
395 regs
->nip
= (unsigned long)cur
->addr
;
396 regs
->msr
&= ~MSR_SE
;
397 regs
->msr
|= kcb
->kprobe_saved_msr
;
398 if (kcb
->kprobe_status
== KPROBE_REENTER
)
399 restore_previous_kprobe(kcb
);
401 reset_current_kprobe();
402 preempt_enable_no_resched();
404 case KPROBE_HIT_ACTIVE
:
405 case KPROBE_HIT_SSDONE
:
407 * We increment the nmissed count for accounting,
408 * we can also use npre/npostfault count for accouting
409 * these specific fault cases.
411 kprobes_inc_nmissed_count(cur
);
414 * We come here because instructions in the pre/post
415 * handler caused the page_fault, this could happen
416 * if handler tries to access user space by
417 * copy_from_user(), get_user() etc. Let the
418 * user-specified handler try to fix it first.
420 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
424 * In case the user-specified fault handler returned
425 * zero, try to fix up.
427 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
428 regs
->nip
= entry
->fixup
;
433 * fixup_exception() could not handle it,
434 * Let do_page_fault() fix it.
444 * Wrapper routine to for handling exceptions.
446 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
447 unsigned long val
, void *data
)
449 struct die_args
*args
= (struct die_args
*)data
;
450 int ret
= NOTIFY_DONE
;
452 if (args
->regs
&& user_mode(args
->regs
))
457 if (kprobe_handler(args
->regs
))
461 if (post_kprobe_handler(args
->regs
))
465 /* kprobe_running() needs smp_processor_id() */
467 if (kprobe_running() &&
468 kprobe_fault_handler(args
->regs
, args
->trapnr
))
478 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
480 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
481 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
483 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
485 /* setup return addr to the jprobe handler routine */
487 regs
->nip
= (unsigned long)(((func_descr_t
*)jp
->entry
)->entry
);
488 regs
->gpr
[2] = (unsigned long)(((func_descr_t
*)jp
->entry
)->toc
);
490 regs
->nip
= (unsigned long)jp
->entry
;
496 void __kprobes
jprobe_return(void)
498 asm volatile("trap" ::: "memory");
501 void __kprobes
jprobe_return_end(void)
505 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
507 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
510 * FIXME - we should ideally be validating that we got here 'cos
511 * of the "trap" in jprobe_return() above, before restoring the
514 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
515 preempt_enable_no_resched();
519 static struct kprobe trampoline_p
= {
520 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
521 .pre_handler
= trampoline_probe_handler
524 int __init
arch_init_kprobes(void)
526 return register_kprobe(&trampoline_p
);