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/extable.h>
33 #include <linux/kdebug.h>
34 #include <linux/slab.h>
35 #include <asm/code-patching.h>
36 #include <asm/cacheflush.h>
37 #include <asm/sstep.h>
38 #include <asm/uaccess.h>
40 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
41 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
43 struct kretprobe_blackpoint kretprobe_blacklist
[] = {{NULL
, NULL
}};
45 int __kprobes
arch_prepare_kprobe(struct kprobe
*p
)
48 kprobe_opcode_t insn
= *p
->addr
;
50 if ((unsigned long)p
->addr
& 0x03) {
51 printk("Attempt to register kprobe at an unaligned address\n");
53 } else if (IS_MTMSRD(insn
) || IS_RFID(insn
) || IS_RFI(insn
)) {
54 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
58 /* insn must be on a special executable page on ppc64. This is
59 * not explicitly required on ppc32 (right now), but it doesn't hurt */
61 p
->ainsn
.insn
= get_insn_slot();
67 memcpy(p
->ainsn
.insn
, p
->addr
,
68 MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
70 flush_icache_range((unsigned long)p
->ainsn
.insn
,
71 (unsigned long)p
->ainsn
.insn
+ sizeof(kprobe_opcode_t
));
74 p
->ainsn
.boostable
= 0;
78 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
80 *p
->addr
= BREAKPOINT_INSTRUCTION
;
81 flush_icache_range((unsigned long) p
->addr
,
82 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
85 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
88 flush_icache_range((unsigned long) p
->addr
,
89 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
92 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
95 free_insn_slot(p
->ainsn
.insn
, 0);
100 static void __kprobes
prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
102 enable_single_step(regs
);
105 * On powerpc we should single step on the original
106 * instruction even if the probed insn is a trap
107 * variant as values in regs could play a part in
108 * if the trap is taken or not
110 regs
->nip
= (unsigned long)p
->ainsn
.insn
;
113 static void __kprobes
save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
115 kcb
->prev_kprobe
.kp
= kprobe_running();
116 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
117 kcb
->prev_kprobe
.saved_msr
= kcb
->kprobe_saved_msr
;
120 static void __kprobes
restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
122 __this_cpu_write(current_kprobe
, kcb
->prev_kprobe
.kp
);
123 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
124 kcb
->kprobe_saved_msr
= kcb
->prev_kprobe
.saved_msr
;
127 static void __kprobes
set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
128 struct kprobe_ctlblk
*kcb
)
130 __this_cpu_write(current_kprobe
, p
);
131 kcb
->kprobe_saved_msr
= regs
->msr
;
134 void __kprobes
arch_prepare_kretprobe(struct kretprobe_instance
*ri
,
135 struct pt_regs
*regs
)
137 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->link
;
139 /* Replace the return addr with trampoline addr */
140 regs
->link
= (unsigned long)kretprobe_trampoline
;
143 int __kprobes
kprobe_handler(struct pt_regs
*regs
)
147 unsigned int *addr
= (unsigned int *)regs
->nip
;
148 struct kprobe_ctlblk
*kcb
;
154 * We don't want to be preempted for the entire
155 * duration of kprobe processing
158 kcb
= get_kprobe_ctlblk();
160 /* Check we're not actually recursing */
161 if (kprobe_running()) {
162 p
= get_kprobe(addr
);
164 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
165 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
167 /* Turn off 'trace' bits */
168 regs
->msr
&= ~MSR_SINGLESTEP
;
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
= __this_cpu_read(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 asm(".global kretprobe_trampoline\n"
285 ".type kretprobe_trampoline, @function\n"
286 "kretprobe_trampoline:\n"
288 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
291 * Called when the probe at kretprobe trampoline is hit
293 static int __kprobes
trampoline_probe_handler(struct kprobe
*p
,
294 struct pt_regs
*regs
)
296 struct kretprobe_instance
*ri
= NULL
;
297 struct hlist_head
*head
, empty_rp
;
298 struct hlist_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 kretprobe_hash_lock(current
, &head
, &flags
);
306 * It is possible to have multiple instances associated with a given
307 * task either because an multiple functions in the call path
308 * have a return probe installed on them, and/or more than one return
309 * return probe was registered for a target function.
311 * We can handle this because:
312 * - instances are always inserted at the head of the list
313 * - when multiple return probes are registered for the same
314 * function, the first instance's ret_addr will point to the
315 * real return address, and all the rest will point to
316 * kretprobe_trampoline
318 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
319 if (ri
->task
!= current
)
320 /* another task is sharing our hash bucket */
323 if (ri
->rp
&& ri
->rp
->handler
)
324 ri
->rp
->handler(ri
, regs
);
326 orig_ret_address
= (unsigned long)ri
->ret_addr
;
327 recycle_rp_inst(ri
, &empty_rp
);
329 if (orig_ret_address
!= trampoline_address
)
331 * This is the real return address. Any other
332 * instances associated with this task are for
333 * other calls deeper on the call stack
338 kretprobe_assert(ri
, orig_ret_address
, trampoline_address
);
339 regs
->nip
= orig_ret_address
;
341 reset_current_kprobe();
342 kretprobe_hash_unlock(current
, &flags
);
343 preempt_enable_no_resched();
345 hlist_for_each_entry_safe(ri
, tmp
, &empty_rp
, hlist
) {
346 hlist_del(&ri
->hlist
);
350 * By returning a non-zero value, we are telling
351 * kprobe_handler() that we don't want the post_handler
352 * to run (and have re-enabled preemption)
358 * Called after single-stepping. p->addr is the address of the
359 * instruction whose first byte has been replaced by the "breakpoint"
360 * instruction. To avoid the SMP problems that can occur when we
361 * temporarily put back the original opcode to single-step, we
362 * single-stepped a copy of the instruction. The address of this
363 * copy is p->ainsn.insn.
365 int __kprobes
kprobe_post_handler(struct pt_regs
*regs
)
367 struct kprobe
*cur
= kprobe_running();
368 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
370 if (!cur
|| user_mode(regs
))
373 /* make sure we got here for instruction we have a kprobe on */
374 if (((unsigned long)cur
->ainsn
.insn
+ 4) != regs
->nip
)
377 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
378 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
379 cur
->post_handler(cur
, regs
, 0);
382 /* Adjust nip to after the single-stepped instruction */
383 regs
->nip
= (unsigned long)cur
->addr
+ 4;
384 regs
->msr
|= kcb
->kprobe_saved_msr
;
386 /*Restore back the original saved kprobes variables and continue. */
387 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
388 restore_previous_kprobe(kcb
);
391 reset_current_kprobe();
393 preempt_enable_no_resched();
396 * if somebody else is singlestepping across a probe point, msr
397 * will have DE/SE set, in which case, continue the remaining processing
398 * of do_debug, as if this is not a probe hit.
400 if (regs
->msr
& MSR_SINGLESTEP
)
406 int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
408 struct kprobe
*cur
= kprobe_running();
409 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
410 const struct exception_table_entry
*entry
;
412 switch(kcb
->kprobe_status
) {
416 * We are here because the instruction being single
417 * stepped caused a page fault. We reset the current
418 * kprobe and the nip points back to the probe address
419 * and allow the page fault handler to continue as a
422 regs
->nip
= (unsigned long)cur
->addr
;
423 regs
->msr
&= ~MSR_SINGLESTEP
; /* Turn off 'trace' bits */
424 regs
->msr
|= kcb
->kprobe_saved_msr
;
425 if (kcb
->kprobe_status
== KPROBE_REENTER
)
426 restore_previous_kprobe(kcb
);
428 reset_current_kprobe();
429 preempt_enable_no_resched();
431 case KPROBE_HIT_ACTIVE
:
432 case KPROBE_HIT_SSDONE
:
434 * We increment the nmissed count for accounting,
435 * we can also use npre/npostfault count for accounting
436 * these specific fault cases.
438 kprobes_inc_nmissed_count(cur
);
441 * We come here because instructions in the pre/post
442 * handler caused the page_fault, this could happen
443 * if handler tries to access user space by
444 * copy_from_user(), get_user() etc. Let the
445 * user-specified handler try to fix it first.
447 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
451 * In case the user-specified fault handler returned
452 * zero, try to fix up.
454 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
455 regs
->nip
= extable_fixup(entry
);
460 * fixup_exception() could not handle it,
461 * Let do_page_fault() fix it.
471 * Wrapper routine to for handling exceptions.
473 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
474 unsigned long val
, void *data
)
479 unsigned long arch_deref_entry_point(void *entry
)
481 return ppc_global_function_entry(entry
);
484 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
486 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
487 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
489 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
491 /* setup return addr to the jprobe handler routine */
492 regs
->nip
= arch_deref_entry_point(jp
->entry
);
493 #ifdef PPC64_ELF_ABI_v2
494 regs
->gpr
[12] = (unsigned long)jp
->entry
;
495 #elif defined(PPC64_ELF_ABI_v1)
496 regs
->gpr
[2] = (unsigned long)(((func_descr_t
*)jp
->entry
)->toc
);
502 void __used __kprobes
jprobe_return(void)
504 asm volatile("trap" ::: "memory");
507 static void __used __kprobes
jprobe_return_end(void)
511 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
513 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
516 * FIXME - we should ideally be validating that we got here 'cos
517 * of the "trap" in jprobe_return() above, before restoring the
520 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
521 preempt_enable_no_resched();
525 static struct kprobe trampoline_p
= {
526 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
527 .pre_handler
= trampoline_probe_handler
530 int __init
arch_init_kprobes(void)
532 return register_kprobe(&trampoline_p
);
535 int __kprobes
arch_trampoline_kprobe(struct kprobe
*p
)
537 if (p
->addr
== (kprobe_opcode_t
*)&kretprobe_trampoline
)