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/sections.h>
39 #include <linux/uaccess.h>
41 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
42 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
44 struct kretprobe_blackpoint kretprobe_blacklist
[] = {{NULL
, NULL
}};
46 int is_current_kprobe_addr(unsigned long addr
)
48 struct kprobe
*p
= kprobe_running();
49 return (p
&& (unsigned long)p
->addr
== addr
) ? 1 : 0;
52 bool arch_within_kprobe_blacklist(unsigned long addr
)
54 return (addr
>= (unsigned long)__kprobes_text_start
&&
55 addr
< (unsigned long)__kprobes_text_end
) ||
56 (addr
>= (unsigned long)_stext
&&
57 addr
< (unsigned long)__head_end
);
60 kprobe_opcode_t
*kprobe_lookup_name(const char *name
, unsigned int offset
)
62 kprobe_opcode_t
*addr
;
64 #ifdef PPC64_ELF_ABI_v2
65 /* PPC64 ABIv2 needs local entry point */
66 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(name
);
67 if (addr
&& !offset
) {
68 #ifdef CONFIG_KPROBES_ON_FTRACE
71 * Per livepatch.h, ftrace location is always within the first
72 * 16 bytes of a function on powerpc with -mprofile-kernel.
74 faddr
= ftrace_location_range((unsigned long)addr
,
75 (unsigned long)addr
+ 16);
77 addr
= (kprobe_opcode_t
*)faddr
;
80 addr
= (kprobe_opcode_t
*)ppc_function_entry(addr
);
82 #elif defined(PPC64_ELF_ABI_v1)
84 * 64bit powerpc ABIv1 uses function descriptors:
85 * - Check for the dot variant of the symbol first.
86 * - If that fails, try looking up the symbol provided.
88 * This ensures we always get to the actual symbol and not
91 * Also handle <module:symbol> format.
93 char dot_name
[MODULE_NAME_LEN
+ 1 + KSYM_NAME_LEN
];
95 bool dot_appended
= false;
96 if ((modsym
= strchr(name
, ':')) != NULL
) {
98 if (*modsym
!= '\0' && *modsym
!= '.') {
99 /* Convert to <module:.symbol> */
100 strncpy(dot_name
, name
, modsym
- name
);
101 dot_name
[modsym
- name
] = '.';
102 dot_name
[modsym
- name
+ 1] = '\0';
103 strncat(dot_name
, modsym
,
104 sizeof(dot_name
) - (modsym
- name
) - 2);
108 strncat(dot_name
, name
, sizeof(dot_name
) - 1);
110 } else if (name
[0] != '.') {
113 strncat(dot_name
, name
, KSYM_NAME_LEN
- 2);
117 strncat(dot_name
, name
, KSYM_NAME_LEN
- 1);
119 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(dot_name
);
120 if (!addr
&& dot_appended
) {
121 /* Let's try the original non-dot symbol lookup */
122 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(name
);
125 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(name
);
131 int arch_prepare_kprobe(struct kprobe
*p
)
134 kprobe_opcode_t insn
= *p
->addr
;
136 if ((unsigned long)p
->addr
& 0x03) {
137 printk("Attempt to register kprobe at an unaligned address\n");
139 } else if (IS_MTMSRD(insn
) || IS_RFID(insn
) || IS_RFI(insn
)) {
140 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
144 /* insn must be on a special executable page on ppc64. This is
145 * not explicitly required on ppc32 (right now), but it doesn't hurt */
147 p
->ainsn
.insn
= get_insn_slot();
153 memcpy(p
->ainsn
.insn
, p
->addr
,
154 MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
155 p
->opcode
= *p
->addr
;
156 flush_icache_range((unsigned long)p
->ainsn
.insn
,
157 (unsigned long)p
->ainsn
.insn
+ sizeof(kprobe_opcode_t
));
160 p
->ainsn
.boostable
= 0;
163 NOKPROBE_SYMBOL(arch_prepare_kprobe
);
165 void arch_arm_kprobe(struct kprobe
*p
)
167 *p
->addr
= BREAKPOINT_INSTRUCTION
;
168 flush_icache_range((unsigned long) p
->addr
,
169 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
171 NOKPROBE_SYMBOL(arch_arm_kprobe
);
173 void arch_disarm_kprobe(struct kprobe
*p
)
175 *p
->addr
= p
->opcode
;
176 flush_icache_range((unsigned long) p
->addr
,
177 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
179 NOKPROBE_SYMBOL(arch_disarm_kprobe
);
181 void arch_remove_kprobe(struct kprobe
*p
)
184 free_insn_slot(p
->ainsn
.insn
, 0);
185 p
->ainsn
.insn
= NULL
;
188 NOKPROBE_SYMBOL(arch_remove_kprobe
);
190 static nokprobe_inline
void prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
192 enable_single_step(regs
);
195 * On powerpc we should single step on the original
196 * instruction even if the probed insn is a trap
197 * variant as values in regs could play a part in
198 * if the trap is taken or not
200 regs
->nip
= (unsigned long)p
->ainsn
.insn
;
203 static nokprobe_inline
void save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
205 kcb
->prev_kprobe
.kp
= kprobe_running();
206 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
207 kcb
->prev_kprobe
.saved_msr
= kcb
->kprobe_saved_msr
;
210 static nokprobe_inline
void restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
212 __this_cpu_write(current_kprobe
, kcb
->prev_kprobe
.kp
);
213 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
214 kcb
->kprobe_saved_msr
= kcb
->prev_kprobe
.saved_msr
;
217 static nokprobe_inline
void set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
218 struct kprobe_ctlblk
*kcb
)
220 __this_cpu_write(current_kprobe
, p
);
221 kcb
->kprobe_saved_msr
= regs
->msr
;
224 bool arch_function_offset_within_entry(unsigned long offset
)
226 #ifdef PPC64_ELF_ABI_v2
227 #ifdef CONFIG_KPROBES_ON_FTRACE
237 void arch_prepare_kretprobe(struct kretprobe_instance
*ri
, struct pt_regs
*regs
)
239 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->link
;
241 /* Replace the return addr with trampoline addr */
242 regs
->link
= (unsigned long)kretprobe_trampoline
;
244 NOKPROBE_SYMBOL(arch_prepare_kretprobe
);
246 int try_to_emulate(struct kprobe
*p
, struct pt_regs
*regs
)
249 unsigned int insn
= *p
->ainsn
.insn
;
251 /* regs->nip is also adjusted if emulate_step returns 1 */
252 ret
= emulate_step(regs
, insn
);
255 * Once this instruction has been boosted
256 * successfully, set the boostable flag
258 if (unlikely(p
->ainsn
.boostable
== 0))
259 p
->ainsn
.boostable
= 1;
260 } else if (ret
< 0) {
262 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
263 * So, we should never get here... but, its still
264 * good to catch them, just in case...
266 printk("Can't step on instruction %x\n", insn
);
269 /* This instruction can't be boosted */
270 p
->ainsn
.boostable
= -1;
274 NOKPROBE_SYMBOL(try_to_emulate
);
276 int kprobe_handler(struct pt_regs
*regs
)
280 unsigned int *addr
= (unsigned int *)regs
->nip
;
281 struct kprobe_ctlblk
*kcb
;
287 * We don't want to be preempted for the entire
288 * duration of kprobe processing
291 kcb
= get_kprobe_ctlblk();
293 /* Check we're not actually recursing */
294 if (kprobe_running()) {
295 p
= get_kprobe(addr
);
297 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
298 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
300 /* Turn off 'trace' bits */
301 regs
->msr
&= ~MSR_SINGLESTEP
;
302 regs
->msr
|= kcb
->kprobe_saved_msr
;
305 /* We have reentered the kprobe_handler(), since
306 * another probe was hit while within the handler.
307 * We here save the original kprobes variables and
308 * just single step on the instruction of the new probe
309 * without calling any user handlers.
311 save_previous_kprobe(kcb
);
312 set_current_kprobe(p
, regs
, kcb
);
313 kprobes_inc_nmissed_count(p
);
314 kcb
->kprobe_status
= KPROBE_REENTER
;
315 if (p
->ainsn
.boostable
>= 0) {
316 ret
= try_to_emulate(p
, regs
);
319 restore_previous_kprobe(kcb
);
320 preempt_enable_no_resched();
324 prepare_singlestep(p
, regs
);
327 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
328 /* If trap variant, then it belongs not to us */
329 kprobe_opcode_t cur_insn
= *addr
;
330 if (is_trap(cur_insn
))
332 /* The breakpoint instruction was removed by
333 * another cpu right after we hit, no further
334 * handling of this interrupt is appropriate
339 p
= __this_cpu_read(current_kprobe
);
340 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
341 if (!skip_singlestep(p
, regs
, kcb
))
349 p
= get_kprobe(addr
);
351 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
353 * PowerPC has multiple variants of the "trap"
354 * instruction. If the current instruction is a
355 * trap variant, it could belong to someone else
357 kprobe_opcode_t cur_insn
= *addr
;
358 if (is_trap(cur_insn
))
361 * The breakpoint instruction was removed right
362 * after we hit it. Another cpu has removed
363 * either a probepoint or a debugger breakpoint
364 * at this address. In either case, no further
365 * handling of this interrupt is appropriate.
369 /* Not one of ours: let kernel handle it */
373 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
374 set_current_kprobe(p
, regs
, kcb
);
375 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
376 /* handler has already set things up, so skip ss setup */
380 if (p
->ainsn
.boostable
>= 0) {
381 ret
= try_to_emulate(p
, regs
);
385 p
->post_handler(p
, regs
, 0);
387 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
388 reset_current_kprobe();
389 preempt_enable_no_resched();
393 prepare_singlestep(p
, regs
);
394 kcb
->kprobe_status
= KPROBE_HIT_SS
;
398 preempt_enable_no_resched();
401 NOKPROBE_SYMBOL(kprobe_handler
);
404 * Function return probe trampoline:
405 * - init_kprobes() establishes a probepoint here
406 * - When the probed function returns, this probe
407 * causes the handlers to fire
409 asm(".global kretprobe_trampoline\n"
410 ".type kretprobe_trampoline, @function\n"
411 "kretprobe_trampoline:\n"
414 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
417 * Called when the probe at kretprobe trampoline is hit
419 static int trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
421 struct kretprobe_instance
*ri
= NULL
;
422 struct hlist_head
*head
, empty_rp
;
423 struct hlist_node
*tmp
;
424 unsigned long flags
, orig_ret_address
= 0;
425 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
427 INIT_HLIST_HEAD(&empty_rp
);
428 kretprobe_hash_lock(current
, &head
, &flags
);
431 * It is possible to have multiple instances associated with a given
432 * task either because an multiple functions in the call path
433 * have a return probe installed on them, and/or more than one return
434 * return probe was registered for a target function.
436 * We can handle this because:
437 * - instances are always inserted at the head of the list
438 * - when multiple return probes are registered for the same
439 * function, the first instance's ret_addr will point to the
440 * real return address, and all the rest will point to
441 * kretprobe_trampoline
443 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
444 if (ri
->task
!= current
)
445 /* another task is sharing our hash bucket */
448 if (ri
->rp
&& ri
->rp
->handler
)
449 ri
->rp
->handler(ri
, regs
);
451 orig_ret_address
= (unsigned long)ri
->ret_addr
;
452 recycle_rp_inst(ri
, &empty_rp
);
454 if (orig_ret_address
!= trampoline_address
)
456 * This is the real return address. Any other
457 * instances associated with this task are for
458 * other calls deeper on the call stack
463 kretprobe_assert(ri
, orig_ret_address
, trampoline_address
);
464 regs
->nip
= orig_ret_address
;
466 * Make LR point to the orig_ret_address.
467 * When the 'nop' inside the kretprobe_trampoline
468 * is optimized, we can do a 'blr' after executing the
469 * detour buffer code.
471 regs
->link
= orig_ret_address
;
473 reset_current_kprobe();
474 kretprobe_hash_unlock(current
, &flags
);
475 preempt_enable_no_resched();
477 hlist_for_each_entry_safe(ri
, tmp
, &empty_rp
, hlist
) {
478 hlist_del(&ri
->hlist
);
482 * By returning a non-zero value, we are telling
483 * kprobe_handler() that we don't want the post_handler
484 * to run (and have re-enabled preemption)
488 NOKPROBE_SYMBOL(trampoline_probe_handler
);
491 * Called after single-stepping. p->addr is the address of the
492 * instruction whose first byte has been replaced by the "breakpoint"
493 * instruction. To avoid the SMP problems that can occur when we
494 * temporarily put back the original opcode to single-step, we
495 * single-stepped a copy of the instruction. The address of this
496 * copy is p->ainsn.insn.
498 int kprobe_post_handler(struct pt_regs
*regs
)
500 struct kprobe
*cur
= kprobe_running();
501 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
503 if (!cur
|| user_mode(regs
))
506 /* make sure we got here for instruction we have a kprobe on */
507 if (((unsigned long)cur
->ainsn
.insn
+ 4) != regs
->nip
)
510 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
511 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
512 cur
->post_handler(cur
, regs
, 0);
515 /* Adjust nip to after the single-stepped instruction */
516 regs
->nip
= (unsigned long)cur
->addr
+ 4;
517 regs
->msr
|= kcb
->kprobe_saved_msr
;
519 /*Restore back the original saved kprobes variables and continue. */
520 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
521 restore_previous_kprobe(kcb
);
524 reset_current_kprobe();
526 preempt_enable_no_resched();
529 * if somebody else is singlestepping across a probe point, msr
530 * will have DE/SE set, in which case, continue the remaining processing
531 * of do_debug, as if this is not a probe hit.
533 if (regs
->msr
& MSR_SINGLESTEP
)
538 NOKPROBE_SYMBOL(kprobe_post_handler
);
540 int kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
542 struct kprobe
*cur
= kprobe_running();
543 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
544 const struct exception_table_entry
*entry
;
546 switch(kcb
->kprobe_status
) {
550 * We are here because the instruction being single
551 * stepped caused a page fault. We reset the current
552 * kprobe and the nip points back to the probe address
553 * and allow the page fault handler to continue as a
556 regs
->nip
= (unsigned long)cur
->addr
;
557 regs
->msr
&= ~MSR_SINGLESTEP
; /* Turn off 'trace' bits */
558 regs
->msr
|= kcb
->kprobe_saved_msr
;
559 if (kcb
->kprobe_status
== KPROBE_REENTER
)
560 restore_previous_kprobe(kcb
);
562 reset_current_kprobe();
563 preempt_enable_no_resched();
565 case KPROBE_HIT_ACTIVE
:
566 case KPROBE_HIT_SSDONE
:
568 * We increment the nmissed count for accounting,
569 * we can also use npre/npostfault count for accounting
570 * these specific fault cases.
572 kprobes_inc_nmissed_count(cur
);
575 * We come here because instructions in the pre/post
576 * handler caused the page_fault, this could happen
577 * if handler tries to access user space by
578 * copy_from_user(), get_user() etc. Let the
579 * user-specified handler try to fix it first.
581 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
585 * In case the user-specified fault handler returned
586 * zero, try to fix up.
588 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
589 regs
->nip
= extable_fixup(entry
);
594 * fixup_exception() could not handle it,
595 * Let do_page_fault() fix it.
603 NOKPROBE_SYMBOL(kprobe_fault_handler
);
605 unsigned long arch_deref_entry_point(void *entry
)
607 return ppc_global_function_entry(entry
);
609 NOKPROBE_SYMBOL(arch_deref_entry_point
);
611 int setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
613 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
614 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
616 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
618 /* setup return addr to the jprobe handler routine */
619 regs
->nip
= arch_deref_entry_point(jp
->entry
);
620 #ifdef PPC64_ELF_ABI_v2
621 regs
->gpr
[12] = (unsigned long)jp
->entry
;
622 #elif defined(PPC64_ELF_ABI_v1)
623 regs
->gpr
[2] = (unsigned long)(((func_descr_t
*)jp
->entry
)->toc
);
627 * jprobes use jprobe_return() which skips the normal return
628 * path of the function, and this messes up the accounting of the
629 * function graph tracer.
631 * Pause function graph tracing while performing the jprobe function.
633 pause_graph_tracing();
637 NOKPROBE_SYMBOL(setjmp_pre_handler
);
639 void __used
jprobe_return(void)
641 asm volatile("trap" ::: "memory");
643 NOKPROBE_SYMBOL(jprobe_return
);
645 static void __used
jprobe_return_end(void)
648 NOKPROBE_SYMBOL(jprobe_return_end
);
650 int longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
652 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
655 * FIXME - we should ideally be validating that we got here 'cos
656 * of the "trap" in jprobe_return() above, before restoring the
659 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
660 /* It's OK to start function graph tracing again */
661 unpause_graph_tracing();
662 preempt_enable_no_resched();
665 NOKPROBE_SYMBOL(longjmp_break_handler
);
667 static struct kprobe trampoline_p
= {
668 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
669 .pre_handler
= trampoline_probe_handler
672 int __init
arch_init_kprobes(void)
674 return register_kprobe(&trampoline_p
);
677 int arch_trampoline_kprobe(struct kprobe
*p
)
679 if (p
->addr
== (kprobe_opcode_t
*)&kretprobe_trampoline
)
684 NOKPROBE_SYMBOL(arch_trampoline_kprobe
);