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 <linux/kdebug.h>
34 #include <asm/cacheflush.h>
35 #include <asm/sstep.h>
36 #include <asm/uaccess.h>
37 #include <asm/system.h>
40 #define MSR_SINGLESTEP (MSR_DE)
42 #define MSR_SINGLESTEP (MSR_SE)
45 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
46 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
48 struct kretprobe_blackpoint kretprobe_blacklist
[] = {{NULL
, NULL
}};
50 int __kprobes
arch_prepare_kprobe(struct kprobe
*p
)
53 kprobe_opcode_t insn
= *p
->addr
;
55 if ((unsigned long)p
->addr
& 0x03) {
56 printk("Attempt to register kprobe at an unaligned address\n");
58 } else if (IS_MTMSRD(insn
) || IS_RFID(insn
) || IS_RFI(insn
)) {
59 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
63 /* insn must be on a special executable page on ppc64. This is
64 * not explicitly required on ppc32 (right now), but it doesn't hurt */
66 p
->ainsn
.insn
= get_insn_slot();
72 memcpy(p
->ainsn
.insn
, p
->addr
,
73 MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
75 flush_icache_range((unsigned long)p
->ainsn
.insn
,
76 (unsigned long)p
->ainsn
.insn
+ sizeof(kprobe_opcode_t
));
79 p
->ainsn
.boostable
= 0;
83 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
85 *p
->addr
= BREAKPOINT_INSTRUCTION
;
86 flush_icache_range((unsigned long) p
->addr
,
87 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
90 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
93 flush_icache_range((unsigned long) p
->addr
,
94 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
97 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
99 mutex_lock(&kprobe_mutex
);
100 free_insn_slot(p
->ainsn
.insn
, 0);
101 mutex_unlock(&kprobe_mutex
);
104 static void __kprobes
prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
106 /* We turn off async exceptions to ensure that the single step will
107 * be for the instruction we have the kprobe on, if we dont its
108 * possible we'd get the single step reported for an exception handler
109 * like Decrementer or External Interrupt */
110 regs
->msr
&= ~MSR_EE
;
111 regs
->msr
|= MSR_SINGLESTEP
;
113 regs
->msr
&= ~MSR_CE
;
114 mtspr(SPRN_DBCR0
, mfspr(SPRN_DBCR0
) | DBCR0_IC
| DBCR0_IDM
);
118 * On powerpc we should single step on the original
119 * instruction even if the probed insn is a trap
120 * variant as values in regs could play a part in
121 * if the trap is taken or not
123 regs
->nip
= (unsigned long)p
->ainsn
.insn
;
126 static void __kprobes
save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
128 kcb
->prev_kprobe
.kp
= kprobe_running();
129 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
130 kcb
->prev_kprobe
.saved_msr
= kcb
->kprobe_saved_msr
;
133 static void __kprobes
restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
135 __get_cpu_var(current_kprobe
) = kcb
->prev_kprobe
.kp
;
136 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
137 kcb
->kprobe_saved_msr
= kcb
->prev_kprobe
.saved_msr
;
140 static void __kprobes
set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
141 struct kprobe_ctlblk
*kcb
)
143 __get_cpu_var(current_kprobe
) = p
;
144 kcb
->kprobe_saved_msr
= regs
->msr
;
147 void __kprobes
arch_prepare_kretprobe(struct kretprobe_instance
*ri
,
148 struct pt_regs
*regs
)
150 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->link
;
152 /* Replace the return addr with trampoline addr */
153 regs
->link
= (unsigned long)kretprobe_trampoline
;
156 static int __kprobes
kprobe_handler(struct pt_regs
*regs
)
160 unsigned int *addr
= (unsigned int *)regs
->nip
;
161 struct kprobe_ctlblk
*kcb
;
164 * We don't want to be preempted for the entire
165 * duration of kprobe processing
168 kcb
= get_kprobe_ctlblk();
170 /* Check we're not actually recursing */
171 if (kprobe_running()) {
172 p
= get_kprobe(addr
);
174 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
175 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
177 /* Turn off 'trace' bits */
178 regs
->msr
&= ~MSR_SINGLESTEP
;
179 regs
->msr
|= kcb
->kprobe_saved_msr
;
182 /* We have reentered the kprobe_handler(), since
183 * another probe was hit while within the handler.
184 * We here save the original kprobes variables and
185 * just single step on the instruction of the new probe
186 * without calling any user handlers.
188 save_previous_kprobe(kcb
);
189 set_current_kprobe(p
, regs
, kcb
);
190 kcb
->kprobe_saved_msr
= regs
->msr
;
191 kprobes_inc_nmissed_count(p
);
192 prepare_singlestep(p
, regs
);
193 kcb
->kprobe_status
= KPROBE_REENTER
;
196 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
197 /* If trap variant, then it belongs not to us */
198 kprobe_opcode_t cur_insn
= *addr
;
199 if (is_trap(cur_insn
))
201 /* The breakpoint instruction was removed by
202 * another cpu right after we hit, no further
203 * handling of this interrupt is appropriate
208 p
= __get_cpu_var(current_kprobe
);
209 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
216 p
= get_kprobe(addr
);
218 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
220 * PowerPC has multiple variants of the "trap"
221 * instruction. If the current instruction is a
222 * trap variant, it could belong to someone else
224 kprobe_opcode_t cur_insn
= *addr
;
225 if (is_trap(cur_insn
))
228 * The breakpoint instruction was removed right
229 * after we hit it. Another cpu has removed
230 * either a probepoint or a debugger breakpoint
231 * at this address. In either case, no further
232 * handling of this interrupt is appropriate.
236 /* Not one of ours: let kernel handle it */
240 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
241 set_current_kprobe(p
, regs
, kcb
);
242 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
243 /* handler has already set things up, so skip ss setup */
247 if (p
->ainsn
.boostable
>= 0) {
248 unsigned int insn
= *p
->ainsn
.insn
;
250 /* regs->nip is also adjusted if emulate_step returns 1 */
251 ret
= emulate_step(regs
, insn
);
254 * Once this instruction has been boosted
255 * successfully, set the boostable flag
257 if (unlikely(p
->ainsn
.boostable
== 0))
258 p
->ainsn
.boostable
= 1;
261 p
->post_handler(p
, regs
, 0);
263 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
264 reset_current_kprobe();
265 preempt_enable_no_resched();
267 } else if (ret
< 0) {
269 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
270 * So, we should never get here... but, its still
271 * good to catch them, just in case...
273 printk("Can't step on instruction %x\n", insn
);
276 /* This instruction can't be boosted */
277 p
->ainsn
.boostable
= -1;
279 prepare_singlestep(p
, regs
);
280 kcb
->kprobe_status
= KPROBE_HIT_SS
;
284 preempt_enable_no_resched();
289 * Function return probe trampoline:
290 * - init_kprobes() establishes a probepoint here
291 * - When the probed function returns, this probe
292 * causes the handlers to fire
294 static void __used
kretprobe_trampoline_holder(void)
296 asm volatile(".global kretprobe_trampoline\n"
297 "kretprobe_trampoline:\n"
302 * Called when the probe at kretprobe trampoline is hit
304 static int __kprobes
trampoline_probe_handler(struct kprobe
*p
,
305 struct pt_regs
*regs
)
307 struct kretprobe_instance
*ri
= NULL
;
308 struct hlist_head
*head
, empty_rp
;
309 struct hlist_node
*node
, *tmp
;
310 unsigned long flags
, orig_ret_address
= 0;
311 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
313 INIT_HLIST_HEAD(&empty_rp
);
314 kretprobe_hash_lock(current
, &head
, &flags
);
317 * It is possible to have multiple instances associated with a given
318 * task either because an multiple functions in the call path
319 * have a return probe installed on them, and/or more then one return
320 * return probe was registered for a target function.
322 * We can handle this because:
323 * - instances are always inserted at the head of the list
324 * - when multiple return probes are registered for the same
325 * function, the first instance's ret_addr will point to the
326 * real return address, and all the rest will point to
327 * kretprobe_trampoline
329 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
330 if (ri
->task
!= current
)
331 /* another task is sharing our hash bucket */
334 if (ri
->rp
&& ri
->rp
->handler
)
335 ri
->rp
->handler(ri
, regs
);
337 orig_ret_address
= (unsigned long)ri
->ret_addr
;
338 recycle_rp_inst(ri
, &empty_rp
);
340 if (orig_ret_address
!= trampoline_address
)
342 * This is the real return address. Any other
343 * instances associated with this task are for
344 * other calls deeper on the call stack
349 kretprobe_assert(ri
, orig_ret_address
, trampoline_address
);
350 regs
->nip
= orig_ret_address
;
352 reset_current_kprobe();
353 kretprobe_hash_unlock(current
, &flags
);
354 preempt_enable_no_resched();
356 hlist_for_each_entry_safe(ri
, node
, tmp
, &empty_rp
, hlist
) {
357 hlist_del(&ri
->hlist
);
361 * By returning a non-zero value, we are telling
362 * kprobe_handler() that we don't want the post_handler
363 * to run (and have re-enabled preemption)
369 * Called after single-stepping. p->addr is the address of the
370 * instruction whose first byte has been replaced by the "breakpoint"
371 * instruction. To avoid the SMP problems that can occur when we
372 * temporarily put back the original opcode to single-step, we
373 * single-stepped a copy of the instruction. The address of this
374 * copy is p->ainsn.insn.
376 static void __kprobes
resume_execution(struct kprobe
*p
, struct pt_regs
*regs
)
379 unsigned int insn
= *p
->ainsn
.insn
;
381 regs
->nip
= (unsigned long)p
->addr
;
382 ret
= emulate_step(regs
, insn
);
384 regs
->nip
= (unsigned long)p
->addr
+ 4;
387 static int __kprobes
post_kprobe_handler(struct pt_regs
*regs
)
389 struct kprobe
*cur
= kprobe_running();
390 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
395 /* make sure we got here for instruction we have a kprobe on */
396 if (((unsigned long)cur
->ainsn
.insn
+ 4) != regs
->nip
)
399 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
400 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
401 cur
->post_handler(cur
, regs
, 0);
404 resume_execution(cur
, regs
);
405 regs
->msr
|= kcb
->kprobe_saved_msr
;
407 /*Restore back the original saved kprobes variables and continue. */
408 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
409 restore_previous_kprobe(kcb
);
412 reset_current_kprobe();
414 preempt_enable_no_resched();
417 * if somebody else is singlestepping across a probe point, msr
418 * will have DE/SE set, in which case, continue the remaining processing
419 * of do_debug, as if this is not a probe hit.
421 if (regs
->msr
& MSR_SINGLESTEP
)
427 int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
429 struct kprobe
*cur
= kprobe_running();
430 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
431 const struct exception_table_entry
*entry
;
433 switch(kcb
->kprobe_status
) {
437 * We are here because the instruction being single
438 * stepped caused a page fault. We reset the current
439 * kprobe and the nip points back to the probe address
440 * and allow the page fault handler to continue as a
443 regs
->nip
= (unsigned long)cur
->addr
;
444 regs
->msr
&= ~MSR_SINGLESTEP
; /* Turn off 'trace' bits */
445 regs
->msr
|= kcb
->kprobe_saved_msr
;
446 if (kcb
->kprobe_status
== KPROBE_REENTER
)
447 restore_previous_kprobe(kcb
);
449 reset_current_kprobe();
450 preempt_enable_no_resched();
452 case KPROBE_HIT_ACTIVE
:
453 case KPROBE_HIT_SSDONE
:
455 * We increment the nmissed count for accounting,
456 * we can also use npre/npostfault count for accouting
457 * these specific fault cases.
459 kprobes_inc_nmissed_count(cur
);
462 * We come here because instructions in the pre/post
463 * handler caused the page_fault, this could happen
464 * if handler tries to access user space by
465 * copy_from_user(), get_user() etc. Let the
466 * user-specified handler try to fix it first.
468 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
472 * In case the user-specified fault handler returned
473 * zero, try to fix up.
475 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
476 regs
->nip
= entry
->fixup
;
481 * fixup_exception() could not handle it,
482 * Let do_page_fault() fix it.
492 * Wrapper routine to for handling exceptions.
494 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
495 unsigned long val
, void *data
)
497 struct die_args
*args
= (struct die_args
*)data
;
498 int ret
= NOTIFY_DONE
;
500 if (args
->regs
&& user_mode(args
->regs
))
505 if (kprobe_handler(args
->regs
))
509 if (post_kprobe_handler(args
->regs
))
519 unsigned long arch_deref_entry_point(void *entry
)
521 return ((func_descr_t
*)entry
)->entry
;
525 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
527 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
528 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
530 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
532 /* setup return addr to the jprobe handler routine */
533 regs
->nip
= arch_deref_entry_point(jp
->entry
);
535 regs
->gpr
[2] = (unsigned long)(((func_descr_t
*)jp
->entry
)->toc
);
541 void __used __kprobes
jprobe_return(void)
543 asm volatile("trap" ::: "memory");
546 static void __used __kprobes
jprobe_return_end(void)
550 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
552 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
555 * FIXME - we should ideally be validating that we got here 'cos
556 * of the "trap" in jprobe_return() above, before restoring the
559 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
560 preempt_enable_no_resched();
564 static struct kprobe trampoline_p
= {
565 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
566 .pre_handler
= trampoline_probe_handler
569 int __init
arch_init_kprobes(void)
571 return register_kprobe(&trampoline_p
);
574 int __kprobes
arch_trampoline_kprobe(struct kprobe
*p
)
576 if (p
->addr
== (kprobe_opcode_t
*)&kretprobe_trampoline
)