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/config.h>
30 #include <linux/kprobes.h>
31 #include <linux/ptrace.h>
32 #include <linux/preempt.h>
33 #include <linux/module.h>
34 #include <asm/cacheflush.h>
35 #include <asm/kdebug.h>
36 #include <asm/sstep.h>
37 #include <asm/uaccess.h>
39 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
40 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
42 int __kprobes
arch_prepare_kprobe(struct kprobe
*p
)
45 kprobe_opcode_t insn
= *p
->addr
;
47 if ((unsigned long)p
->addr
& 0x03) {
48 printk("Attempt to register kprobe at an unaligned address\n");
50 } else if (IS_MTMSRD(insn
) || IS_RFID(insn
)) {
51 printk("Cannot register a kprobe on rfid or mtmsrd\n");
55 /* insn must be on a special executable page on ppc64 */
57 p
->ainsn
.insn
= get_insn_slot();
63 memcpy(p
->ainsn
.insn
, p
->addr
, MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
70 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
72 *p
->addr
= BREAKPOINT_INSTRUCTION
;
73 flush_icache_range((unsigned long) p
->addr
,
74 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
77 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
80 flush_icache_range((unsigned long) p
->addr
,
81 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
84 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
86 mutex_lock(&kprobe_mutex
);
87 free_insn_slot(p
->ainsn
.insn
);
88 mutex_unlock(&kprobe_mutex
);
91 static void __kprobes
prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
93 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
97 /* single step inline if it is a trap variant */
99 regs
->nip
= (unsigned long)p
->addr
;
101 regs
->nip
= (unsigned long)p
->ainsn
.insn
;
104 static void __kprobes
save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
106 kcb
->prev_kprobe
.kp
= kprobe_running();
107 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
108 kcb
->prev_kprobe
.saved_msr
= kcb
->kprobe_saved_msr
;
111 static void __kprobes
restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
113 __get_cpu_var(current_kprobe
) = kcb
->prev_kprobe
.kp
;
114 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
115 kcb
->kprobe_saved_msr
= kcb
->prev_kprobe
.saved_msr
;
118 static void __kprobes
set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
119 struct kprobe_ctlblk
*kcb
)
121 __get_cpu_var(current_kprobe
) = p
;
122 kcb
->kprobe_saved_msr
= regs
->msr
;
125 /* Called with kretprobe_lock held */
126 void __kprobes
arch_prepare_kretprobe(struct kretprobe
*rp
,
127 struct pt_regs
*regs
)
129 struct kretprobe_instance
*ri
;
131 if ((ri
= get_free_rp_inst(rp
)) != NULL
) {
134 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->link
;
136 /* Replace the return addr with trampoline addr */
137 regs
->link
= (unsigned long)kretprobe_trampoline
;
144 static int __kprobes
kprobe_handler(struct pt_regs
*regs
)
148 unsigned int *addr
= (unsigned int *)regs
->nip
;
149 struct kprobe_ctlblk
*kcb
;
152 * We don't want to be preempted for the entire
153 * duration of kprobe processing
156 kcb
= get_kprobe_ctlblk();
158 /* Check we're not actually recursing */
159 if (kprobe_running()) {
160 p
= get_kprobe(addr
);
162 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
163 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
165 regs
->msr
&= ~MSR_SE
;
166 regs
->msr
|= kcb
->kprobe_saved_msr
;
169 /* We have reentered the kprobe_handler(), since
170 * another probe was hit while within the handler.
171 * We here save the original kprobes variables and
172 * just single step on the instruction of the new probe
173 * without calling any user handlers.
175 save_previous_kprobe(kcb
);
176 set_current_kprobe(p
, regs
, kcb
);
177 kcb
->kprobe_saved_msr
= regs
->msr
;
178 kprobes_inc_nmissed_count(p
);
179 prepare_singlestep(p
, regs
);
180 kcb
->kprobe_status
= KPROBE_REENTER
;
183 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
184 /* If trap variant, then it belongs not to us */
185 kprobe_opcode_t cur_insn
= *addr
;
186 if (is_trap(cur_insn
))
188 /* The breakpoint instruction was removed by
189 * another cpu right after we hit, no further
190 * handling of this interrupt is appropriate
195 p
= __get_cpu_var(current_kprobe
);
196 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
203 p
= get_kprobe(addr
);
205 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
207 * PowerPC has multiple variants of the "trap"
208 * instruction. If the current instruction is a
209 * trap variant, it could belong to someone else
211 kprobe_opcode_t cur_insn
= *addr
;
212 if (is_trap(cur_insn
))
215 * The breakpoint instruction was removed right
216 * after we hit it. Another cpu has removed
217 * either a probepoint or a debugger breakpoint
218 * at this address. In either case, no further
219 * handling of this interrupt is appropriate.
223 /* Not one of ours: let kernel handle it */
227 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
228 set_current_kprobe(p
, regs
, kcb
);
229 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
230 /* handler has already set things up, so skip ss setup */
234 prepare_singlestep(p
, regs
);
235 kcb
->kprobe_status
= KPROBE_HIT_SS
;
239 preempt_enable_no_resched();
244 * Function return probe trampoline:
245 * - init_kprobes() establishes a probepoint here
246 * - When the probed function returns, this probe
247 * causes the handlers to fire
249 void kretprobe_trampoline_holder(void)
251 asm volatile(".global kretprobe_trampoline\n"
252 "kretprobe_trampoline:\n"
257 * Called when the probe at kretprobe trampoline is hit
259 int __kprobes
trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
261 struct kretprobe_instance
*ri
= NULL
;
262 struct hlist_head
*head
;
263 struct hlist_node
*node
, *tmp
;
264 unsigned long flags
, orig_ret_address
= 0;
265 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
267 spin_lock_irqsave(&kretprobe_lock
, flags
);
268 head
= kretprobe_inst_table_head(current
);
271 * It is possible to have multiple instances associated with a given
272 * task either because an multiple functions in the call path
273 * have a return probe installed on them, and/or more then one return
274 * return probe was registered for a target function.
276 * We can handle this because:
277 * - instances are always inserted at the head of the list
278 * - when multiple return probes are registered for the same
279 * function, the first instance's ret_addr will point to the
280 * real return address, and all the rest will point to
281 * kretprobe_trampoline
283 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
284 if (ri
->task
!= current
)
285 /* another task is sharing our hash bucket */
288 if (ri
->rp
&& ri
->rp
->handler
)
289 ri
->rp
->handler(ri
, regs
);
291 orig_ret_address
= (unsigned long)ri
->ret_addr
;
294 if (orig_ret_address
!= trampoline_address
)
296 * This is the real return address. Any other
297 * instances associated with this task are for
298 * other calls deeper on the call stack
303 BUG_ON(!orig_ret_address
|| (orig_ret_address
== trampoline_address
));
304 regs
->nip
= orig_ret_address
;
306 reset_current_kprobe();
307 spin_unlock_irqrestore(&kretprobe_lock
, flags
);
308 preempt_enable_no_resched();
311 * By returning a non-zero value, we are telling
312 * kprobe_handler() that we don't want the post_handler
313 * to run (and have re-enabled preemption)
319 * Called after single-stepping. p->addr is the address of the
320 * instruction whose first byte has been replaced by the "breakpoint"
321 * instruction. To avoid the SMP problems that can occur when we
322 * temporarily put back the original opcode to single-step, we
323 * single-stepped a copy of the instruction. The address of this
324 * copy is p->ainsn.insn.
326 static void __kprobes
resume_execution(struct kprobe
*p
, struct pt_regs
*regs
)
329 unsigned int insn
= *p
->ainsn
.insn
;
331 regs
->nip
= (unsigned long)p
->addr
;
332 ret
= emulate_step(regs
, insn
);
334 regs
->nip
= (unsigned long)p
->addr
+ 4;
337 static int __kprobes
post_kprobe_handler(struct pt_regs
*regs
)
339 struct kprobe
*cur
= kprobe_running();
340 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
345 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
346 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
347 cur
->post_handler(cur
, regs
, 0);
350 resume_execution(cur
, regs
);
351 regs
->msr
|= kcb
->kprobe_saved_msr
;
353 /*Restore back the original saved kprobes variables and continue. */
354 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
355 restore_previous_kprobe(kcb
);
358 reset_current_kprobe();
360 preempt_enable_no_resched();
363 * if somebody else is singlestepping across a probe point, msr
364 * will have SE set, in which case, continue the remaining processing
365 * of do_debug, as if this is not a probe hit.
367 if (regs
->msr
& MSR_SE
)
373 static int __kprobes
kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
375 struct kprobe
*cur
= kprobe_running();
376 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
377 const struct exception_table_entry
*entry
;
379 switch(kcb
->kprobe_status
) {
383 * We are here because the instruction being single
384 * stepped caused a page fault. We reset the current
385 * kprobe and the nip points back to the probe address
386 * and allow the page fault handler to continue as a
389 regs
->nip
= (unsigned long)cur
->addr
;
390 regs
->msr
&= ~MSR_SE
;
391 regs
->msr
|= kcb
->kprobe_saved_msr
;
392 if (kcb
->kprobe_status
== KPROBE_REENTER
)
393 restore_previous_kprobe(kcb
);
395 reset_current_kprobe();
396 preempt_enable_no_resched();
398 case KPROBE_HIT_ACTIVE
:
399 case KPROBE_HIT_SSDONE
:
401 * We increment the nmissed count for accounting,
402 * we can also use npre/npostfault count for accouting
403 * these specific fault cases.
405 kprobes_inc_nmissed_count(cur
);
408 * We come here because instructions in the pre/post
409 * handler caused the page_fault, this could happen
410 * if handler tries to access user space by
411 * copy_from_user(), get_user() etc. Let the
412 * user-specified handler try to fix it first.
414 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
418 * In case the user-specified fault handler returned
419 * zero, try to fix up.
421 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
422 regs
->nip
= entry
->fixup
;
427 * fixup_exception() could not handle it,
428 * Let do_page_fault() fix it.
438 * Wrapper routine to for handling exceptions.
440 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
441 unsigned long val
, void *data
)
443 struct die_args
*args
= (struct die_args
*)data
;
444 int ret
= NOTIFY_DONE
;
446 if (args
->regs
&& user_mode(args
->regs
))
451 if (kprobe_handler(args
->regs
))
455 if (post_kprobe_handler(args
->regs
))
459 /* kprobe_running() needs smp_processor_id() */
461 if (kprobe_running() &&
462 kprobe_fault_handler(args
->regs
, args
->trapnr
))
472 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
474 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
475 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
477 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
479 /* setup return addr to the jprobe handler routine */
480 regs
->nip
= (unsigned long)(((func_descr_t
*)jp
->entry
)->entry
);
481 regs
->gpr
[2] = (unsigned long)(((func_descr_t
*)jp
->entry
)->toc
);
486 void __kprobes
jprobe_return(void)
488 asm volatile("trap" ::: "memory");
491 void __kprobes
jprobe_return_end(void)
495 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
497 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
500 * FIXME - we should ideally be validating that we got here 'cos
501 * of the "trap" in jprobe_return() above, before restoring the
504 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
505 preempt_enable_no_resched();
509 static struct kprobe trampoline_p
= {
510 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
511 .pre_handler
= trampoline_probe_handler
514 int __init
arch_init_kprobes(void)
516 return register_kprobe(&trampoline_p
);
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