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, 2006
20 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
23 #include <linux/kprobes.h>
24 #include <linux/ptrace.h>
25 #include <linux/preempt.h>
26 #include <linux/stop_machine.h>
27 #include <asm/cacheflush.h>
28 #include <asm/kdebug.h>
29 #include <asm/sections.h>
30 #include <asm/uaccess.h>
31 #include <linux/module.h>
33 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
34 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
36 int __kprobes
arch_prepare_kprobe(struct kprobe
*p
)
38 /* Make sure the probe isn't going on a difficult instruction */
39 if (is_prohibited_opcode((kprobe_opcode_t
*) p
->addr
))
42 if ((unsigned long)p
->addr
& 0x01) {
43 printk("Attempt to register kprobe at an unaligned address\n");
47 /* Use the get_insn_slot() facility for correctness */
48 if (!(p
->ainsn
.insn
= get_insn_slot()))
51 memcpy(p
->ainsn
.insn
, p
->addr
, MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
53 get_instruction_type(&p
->ainsn
);
58 int __kprobes
is_prohibited_opcode(kprobe_opcode_t
*instruction
)
60 switch (*(__u8
*) instruction
) {
61 case 0x0c: /* bassm */
67 switch (*(__u16
*) instruction
) {
69 case 0xb25a: /* bsa */
70 case 0xb240: /* bakr */
71 case 0xb258: /* bsg */
79 void __kprobes
get_instruction_type(struct arch_specific_insn
*ainsn
)
81 /* default fixup method */
82 ainsn
->fixup
= FIXUP_PSW_NORMAL
;
85 ainsn
->reg
= (*ainsn
->insn
& 0xf0) >> 4;
87 /* save the instruction length (pop 5-5) in bytes */
88 switch (*(__u8
*) (ainsn
->insn
) >> 4) {
101 switch (*(__u8
*) ainsn
->insn
) {
102 case 0x05: /* balr */
103 case 0x0d: /* basr */
104 ainsn
->fixup
= FIXUP_RETURN_REGISTER
;
105 /* if r2 = 0, no branch will be taken */
106 if ((*ainsn
->insn
& 0x0f) == 0)
107 ainsn
->fixup
|= FIXUP_BRANCH_NOT_TAKEN
;
109 case 0x06: /* bctr */
111 ainsn
->fixup
= FIXUP_BRANCH_NOT_TAKEN
;
115 ainsn
->fixup
= FIXUP_RETURN_REGISTER
;
120 case 0x87: /* bxle */
121 ainsn
->fixup
= FIXUP_BRANCH_NOT_TAKEN
;
123 case 0x82: /* lpsw */
124 ainsn
->fixup
= FIXUP_NOT_REQUIRED
;
126 case 0xb2: /* lpswe */
127 if (*(((__u8
*) ainsn
->insn
) + 1) == 0xb2) {
128 ainsn
->fixup
= FIXUP_NOT_REQUIRED
;
131 case 0xa7: /* bras */
132 if ((*ainsn
->insn
& 0x0f) == 0x05) {
133 ainsn
->fixup
|= FIXUP_RETURN_REGISTER
;
137 if ((*ainsn
->insn
& 0x0f) == 0x00 /* larl */
138 || (*ainsn
->insn
& 0x0f) == 0x05) /* brasl */
139 ainsn
->fixup
|= FIXUP_RETURN_REGISTER
;
142 if (*(((__u8
*) ainsn
->insn
) + 5 ) == 0x44 || /* bxhg */
143 *(((__u8
*) ainsn
->insn
) + 5) == 0x45) {/* bxleg */
144 ainsn
->fixup
= FIXUP_BRANCH_NOT_TAKEN
;
147 case 0xe3: /* bctg */
148 if (*(((__u8
*) ainsn
->insn
) + 5) == 0x46) {
149 ainsn
->fixup
= FIXUP_BRANCH_NOT_TAKEN
;
155 static int __kprobes
swap_instruction(void *aref
)
157 struct ins_replace_args
*args
= aref
;
161 "0: mvc 0(2,%2),0(%3)\n"
165 : "+d" (err
), "=m" (*args
->ptr
)
166 : "a" (args
->ptr
), "a" (&args
->new), "m" (args
->new));
170 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
172 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
173 unsigned long status
= kcb
->kprobe_status
;
174 struct ins_replace_args args
;
177 args
.old
= p
->opcode
;
178 args
.new = BREAKPOINT_INSTRUCTION
;
180 kcb
->kprobe_status
= KPROBE_SWAP_INST
;
181 stop_machine_run(swap_instruction
, &args
, NR_CPUS
);
182 kcb
->kprobe_status
= status
;
185 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
187 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
188 unsigned long status
= kcb
->kprobe_status
;
189 struct ins_replace_args args
;
192 args
.old
= BREAKPOINT_INSTRUCTION
;
193 args
.new = p
->opcode
;
195 kcb
->kprobe_status
= KPROBE_SWAP_INST
;
196 stop_machine_run(swap_instruction
, &args
, NR_CPUS
);
197 kcb
->kprobe_status
= status
;
200 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
202 mutex_lock(&kprobe_mutex
);
203 free_insn_slot(p
->ainsn
.insn
, 0);
204 mutex_unlock(&kprobe_mutex
);
207 static void __kprobes
prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
209 per_cr_bits kprobe_per_regs
[1];
211 memset(kprobe_per_regs
, 0, sizeof(per_cr_bits
));
212 regs
->psw
.addr
= (unsigned long)p
->ainsn
.insn
| PSW_ADDR_AMODE
;
214 /* Set up the per control reg info, will pass to lctl */
215 kprobe_per_regs
[0].em_instruction_fetch
= 1;
216 kprobe_per_regs
[0].starting_addr
= (unsigned long)p
->ainsn
.insn
;
217 kprobe_per_regs
[0].ending_addr
= (unsigned long)p
->ainsn
.insn
+ 1;
219 /* Set the PER control regs, turns on single step for this address */
220 __ctl_load(kprobe_per_regs
, 9, 11);
221 regs
->psw
.mask
|= PSW_MASK_PER
;
222 regs
->psw
.mask
&= ~(PSW_MASK_IO
| PSW_MASK_EXT
| PSW_MASK_MCHECK
);
225 static void __kprobes
save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
227 kcb
->prev_kprobe
.kp
= kprobe_running();
228 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
229 kcb
->prev_kprobe
.kprobe_saved_imask
= kcb
->kprobe_saved_imask
;
230 memcpy(kcb
->prev_kprobe
.kprobe_saved_ctl
, kcb
->kprobe_saved_ctl
,
231 sizeof(kcb
->kprobe_saved_ctl
));
234 static void __kprobes
restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
236 __get_cpu_var(current_kprobe
) = kcb
->prev_kprobe
.kp
;
237 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
238 kcb
->kprobe_saved_imask
= kcb
->prev_kprobe
.kprobe_saved_imask
;
239 memcpy(kcb
->kprobe_saved_ctl
, kcb
->prev_kprobe
.kprobe_saved_ctl
,
240 sizeof(kcb
->kprobe_saved_ctl
));
243 static void __kprobes
set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
244 struct kprobe_ctlblk
*kcb
)
246 __get_cpu_var(current_kprobe
) = p
;
247 /* Save the interrupt and per flags */
248 kcb
->kprobe_saved_imask
= regs
->psw
.mask
&
249 (PSW_MASK_PER
| PSW_MASK_IO
| PSW_MASK_EXT
| PSW_MASK_MCHECK
);
250 /* Save the control regs that govern PER */
251 __ctl_store(kcb
->kprobe_saved_ctl
, 9, 11);
254 /* Called with kretprobe_lock held */
255 void __kprobes
arch_prepare_kretprobe(struct kretprobe
*rp
,
256 struct pt_regs
*regs
)
258 struct kretprobe_instance
*ri
;
260 if ((ri
= get_free_rp_inst(rp
)) != NULL
) {
263 ri
->ret_addr
= (kprobe_opcode_t
*) regs
->gprs
[14];
265 /* Replace the return addr with trampoline addr */
266 regs
->gprs
[14] = (unsigned long)&kretprobe_trampoline
;
274 static int __kprobes
kprobe_handler(struct pt_regs
*regs
)
278 unsigned long *addr
= (unsigned long *)
279 ((regs
->psw
.addr
& PSW_ADDR_INSN
) - 2);
280 struct kprobe_ctlblk
*kcb
;
283 * We don't want to be preempted for the entire
284 * duration of kprobe processing
287 kcb
= get_kprobe_ctlblk();
289 /* Check we're not actually recursing */
290 if (kprobe_running()) {
291 p
= get_kprobe(addr
);
293 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
294 *p
->ainsn
.insn
== BREAKPOINT_INSTRUCTION
) {
295 regs
->psw
.mask
&= ~PSW_MASK_PER
;
296 regs
->psw
.mask
|= kcb
->kprobe_saved_imask
;
299 /* We have reentered the kprobe_handler(), since
300 * another probe was hit while within the handler.
301 * We here save the original kprobes variables and
302 * just single step on the instruction of the new probe
303 * without calling any user handlers.
305 save_previous_kprobe(kcb
);
306 set_current_kprobe(p
, regs
, kcb
);
307 kprobes_inc_nmissed_count(p
);
308 prepare_singlestep(p
, regs
);
309 kcb
->kprobe_status
= KPROBE_REENTER
;
312 p
= __get_cpu_var(current_kprobe
);
313 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
320 p
= get_kprobe(addr
);
322 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
324 * The breakpoint instruction was removed right
325 * after we hit it. Another cpu has removed
326 * either a probepoint or a debugger breakpoint
327 * at this address. In either case, no further
328 * handling of this interrupt is appropriate.
333 /* Not one of ours: let kernel handle it */
337 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
338 set_current_kprobe(p
, regs
, kcb
);
339 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
340 /* handler has already set things up, so skip ss setup */
344 prepare_singlestep(p
, regs
);
345 kcb
->kprobe_status
= KPROBE_HIT_SS
;
349 preempt_enable_no_resched();
354 * Function return probe trampoline:
355 * - init_kprobes() establishes a probepoint here
356 * - When the probed function returns, this probe
357 * causes the handlers to fire
359 void __kprobes
kretprobe_trampoline_holder(void)
361 asm volatile(".global kretprobe_trampoline\n"
362 "kretprobe_trampoline: bcr 0,0\n");
366 * Called when the probe at kretprobe trampoline is hit
368 int __kprobes
trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
370 struct kretprobe_instance
*ri
= NULL
;
371 struct hlist_head
*head
, empty_rp
;
372 struct hlist_node
*node
, *tmp
;
373 unsigned long flags
, orig_ret_address
= 0;
374 unsigned long trampoline_address
= (unsigned long)&kretprobe_trampoline
;
376 INIT_HLIST_HEAD(&empty_rp
);
377 spin_lock_irqsave(&kretprobe_lock
, flags
);
378 head
= kretprobe_inst_table_head(current
);
381 * It is possible to have multiple instances associated with a given
382 * task either because an multiple functions in the call path
383 * have a return probe installed on them, and/or more then one return
384 * return probe was registered for a target function.
386 * We can handle this because:
387 * - instances are always inserted at the head of the list
388 * - when multiple return probes are registered for the same
389 * function, the first instance's ret_addr will point to the
390 * real return address, and all the rest will point to
391 * kretprobe_trampoline
393 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
394 if (ri
->task
!= current
)
395 /* another task is sharing our hash bucket */
398 if (ri
->rp
&& ri
->rp
->handler
)
399 ri
->rp
->handler(ri
, regs
);
401 orig_ret_address
= (unsigned long)ri
->ret_addr
;
402 recycle_rp_inst(ri
, &empty_rp
);
404 if (orig_ret_address
!= trampoline_address
) {
406 * This is the real return address. Any other
407 * instances associated with this task are for
408 * other calls deeper on the call stack
413 BUG_ON(!orig_ret_address
|| (orig_ret_address
== trampoline_address
));
414 regs
->psw
.addr
= orig_ret_address
| PSW_ADDR_AMODE
;
416 reset_current_kprobe();
417 spin_unlock_irqrestore(&kretprobe_lock
, flags
);
418 preempt_enable_no_resched();
420 hlist_for_each_entry_safe(ri
, node
, tmp
, &empty_rp
, hlist
) {
421 hlist_del(&ri
->hlist
);
425 * By returning a non-zero value, we are telling
426 * kprobe_handler() that we don't want the post_handler
427 * to run (and have re-enabled preemption)
433 * Called after single-stepping. p->addr is the address of the
434 * instruction whose first byte has been replaced by the "breakpoint"
435 * instruction. To avoid the SMP problems that can occur when we
436 * temporarily put back the original opcode to single-step, we
437 * single-stepped a copy of the instruction. The address of this
438 * copy is p->ainsn.insn.
440 static void __kprobes
resume_execution(struct kprobe
*p
, struct pt_regs
*regs
)
442 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
444 regs
->psw
.addr
&= PSW_ADDR_INSN
;
446 if (p
->ainsn
.fixup
& FIXUP_PSW_NORMAL
)
447 regs
->psw
.addr
= (unsigned long)p
->addr
+
448 ((unsigned long)regs
->psw
.addr
-
449 (unsigned long)p
->ainsn
.insn
);
451 if (p
->ainsn
.fixup
& FIXUP_BRANCH_NOT_TAKEN
)
452 if ((unsigned long)regs
->psw
.addr
-
453 (unsigned long)p
->ainsn
.insn
== p
->ainsn
.ilen
)
454 regs
->psw
.addr
= (unsigned long)p
->addr
+ p
->ainsn
.ilen
;
456 if (p
->ainsn
.fixup
& FIXUP_RETURN_REGISTER
)
457 regs
->gprs
[p
->ainsn
.reg
] = ((unsigned long)p
->addr
+
458 (regs
->gprs
[p
->ainsn
.reg
] -
459 (unsigned long)p
->ainsn
.insn
))
462 regs
->psw
.addr
|= PSW_ADDR_AMODE
;
463 /* turn off PER mode */
464 regs
->psw
.mask
&= ~PSW_MASK_PER
;
465 /* Restore the original per control regs */
466 __ctl_load(kcb
->kprobe_saved_ctl
, 9, 11);
467 regs
->psw
.mask
|= kcb
->kprobe_saved_imask
;
470 static int __kprobes
post_kprobe_handler(struct pt_regs
*regs
)
472 struct kprobe
*cur
= kprobe_running();
473 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
478 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
479 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
480 cur
->post_handler(cur
, regs
, 0);
483 resume_execution(cur
, regs
);
485 /*Restore back the original saved kprobes variables and continue. */
486 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
487 restore_previous_kprobe(kcb
);
490 reset_current_kprobe();
492 preempt_enable_no_resched();
495 * if somebody else is singlestepping across a probe point, psw mask
496 * will have PER set, in which case, continue the remaining processing
497 * of do_single_step, as if this is not a probe hit.
499 if (regs
->psw
.mask
& PSW_MASK_PER
) {
506 static int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
508 struct kprobe
*cur
= kprobe_running();
509 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
510 const struct exception_table_entry
*entry
;
512 switch(kcb
->kprobe_status
) {
513 case KPROBE_SWAP_INST
:
514 /* We are here because the instruction replacement failed */
519 * We are here because the instruction being single
520 * stepped caused a page fault. We reset the current
521 * kprobe and the nip points back to the probe address
522 * and allow the page fault handler to continue as a
525 regs
->psw
.addr
= (unsigned long)cur
->addr
| PSW_ADDR_AMODE
;
526 regs
->psw
.mask
&= ~PSW_MASK_PER
;
527 regs
->psw
.mask
|= kcb
->kprobe_saved_imask
;
528 if (kcb
->kprobe_status
== KPROBE_REENTER
)
529 restore_previous_kprobe(kcb
);
531 reset_current_kprobe();
532 preempt_enable_no_resched();
534 case KPROBE_HIT_ACTIVE
:
535 case KPROBE_HIT_SSDONE
:
537 * We increment the nmissed count for accounting,
538 * we can also use npre/npostfault count for accouting
539 * these specific fault cases.
541 kprobes_inc_nmissed_count(cur
);
544 * We come here because instructions in the pre/post
545 * handler caused the page_fault, this could happen
546 * if handler tries to access user space by
547 * copy_from_user(), get_user() etc. Let the
548 * user-specified handler try to fix it first.
550 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
554 * In case the user-specified fault handler returned
555 * zero, try to fix up.
557 entry
= search_exception_tables(regs
->psw
.addr
& PSW_ADDR_INSN
);
559 regs
->psw
.addr
= entry
->fixup
| PSW_ADDR_AMODE
;
564 * fixup_exception() could not handle it,
565 * Let do_page_fault() fix it.
575 * Wrapper routine to for handling exceptions.
577 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
578 unsigned long val
, void *data
)
580 struct die_args
*args
= (struct die_args
*)data
;
581 int ret
= NOTIFY_DONE
;
585 if (kprobe_handler(args
->regs
))
589 if (post_kprobe_handler(args
->regs
))
594 /* kprobe_running() needs smp_processor_id() */
596 if (kprobe_running() &&
597 kprobe_fault_handler(args
->regs
, args
->trapnr
))
607 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
609 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
611 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
613 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
615 /* setup return addr to the jprobe handler routine */
616 regs
->psw
.addr
= (unsigned long)(jp
->entry
) | PSW_ADDR_AMODE
;
618 /* r14 is the function return address */
619 kcb
->jprobe_saved_r14
= (unsigned long)regs
->gprs
[14];
620 /* r15 is the stack pointer */
621 kcb
->jprobe_saved_r15
= (unsigned long)regs
->gprs
[15];
622 addr
= (unsigned long)kcb
->jprobe_saved_r15
;
624 memcpy(kcb
->jprobes_stack
, (kprobe_opcode_t
*) addr
,
625 MIN_STACK_SIZE(addr
));
629 void __kprobes
jprobe_return(void)
631 asm volatile(".word 0x0002");
634 void __kprobes
jprobe_return_end(void)
636 asm volatile("bcr 0,0");
639 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
641 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
642 unsigned long stack_addr
= (unsigned long)(kcb
->jprobe_saved_r15
);
644 /* Put the regs back */
645 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
646 /* put the stack back */
647 memcpy((kprobe_opcode_t
*) stack_addr
, kcb
->jprobes_stack
,
648 MIN_STACK_SIZE(stack_addr
));
649 preempt_enable_no_resched();
653 static struct kprobe trampoline_p
= {
654 .addr
= (kprobe_opcode_t
*) & kretprobe_trampoline
,
655 .pre_handler
= trampoline_probe_handler
658 int __init
arch_init_kprobes(void)
660 return register_kprobe(&trampoline_p
);