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 bool arch_within_kprobe_blacklist(unsigned long addr
)
48 return (addr
>= (unsigned long)__kprobes_text_start
&&
49 addr
< (unsigned long)__kprobes_text_end
) ||
50 (addr
>= (unsigned long)_stext
&&
51 addr
< (unsigned long)__head_end
);
54 kprobe_opcode_t
*kprobe_lookup_name(const char *name
, unsigned int offset
)
56 kprobe_opcode_t
*addr
= NULL
;
58 #ifdef PPC64_ELF_ABI_v2
59 /* PPC64 ABIv2 needs local entry point */
60 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(name
);
61 if (addr
&& !offset
) {
62 #ifdef CONFIG_KPROBES_ON_FTRACE
65 * Per livepatch.h, ftrace location is always within the first
66 * 16 bytes of a function on powerpc with -mprofile-kernel.
68 faddr
= ftrace_location_range((unsigned long)addr
,
69 (unsigned long)addr
+ 16);
71 addr
= (kprobe_opcode_t
*)faddr
;
74 addr
= (kprobe_opcode_t
*)ppc_function_entry(addr
);
76 #elif defined(PPC64_ELF_ABI_v1)
78 * 64bit powerpc ABIv1 uses function descriptors:
79 * - Check for the dot variant of the symbol first.
80 * - If that fails, try looking up the symbol provided.
82 * This ensures we always get to the actual symbol and not
85 * Also handle <module:symbol> format.
87 char dot_name
[MODULE_NAME_LEN
+ 1 + KSYM_NAME_LEN
];
88 bool dot_appended
= false;
93 if ((c
= strnchr(name
, MODULE_NAME_LEN
, ':')) != NULL
) {
96 memcpy(dot_name
, name
, len
);
100 if (*c
!= '\0' && *c
!= '.') {
101 dot_name
[len
++] = '.';
104 ret
= strscpy(dot_name
+ len
, c
, KSYM_NAME_LEN
);
106 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(dot_name
);
108 /* Fallback to the original non-dot symbol lookup */
109 if (!addr
&& dot_appended
)
110 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(name
);
112 addr
= (kprobe_opcode_t
*)kallsyms_lookup_name(name
);
118 int arch_prepare_kprobe(struct kprobe
*p
)
121 kprobe_opcode_t insn
= *p
->addr
;
123 if ((unsigned long)p
->addr
& 0x03) {
124 printk("Attempt to register kprobe at an unaligned address\n");
126 } else if (IS_MTMSRD(insn
) || IS_RFID(insn
) || IS_RFI(insn
)) {
127 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
131 /* insn must be on a special executable page on ppc64. This is
132 * not explicitly required on ppc32 (right now), but it doesn't hurt */
134 p
->ainsn
.insn
= get_insn_slot();
140 memcpy(p
->ainsn
.insn
, p
->addr
,
141 MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
142 p
->opcode
= *p
->addr
;
143 flush_icache_range((unsigned long)p
->ainsn
.insn
,
144 (unsigned long)p
->ainsn
.insn
+ sizeof(kprobe_opcode_t
));
147 p
->ainsn
.boostable
= 0;
150 NOKPROBE_SYMBOL(arch_prepare_kprobe
);
152 void arch_arm_kprobe(struct kprobe
*p
)
154 patch_instruction(p
->addr
, BREAKPOINT_INSTRUCTION
);
156 NOKPROBE_SYMBOL(arch_arm_kprobe
);
158 void arch_disarm_kprobe(struct kprobe
*p
)
160 patch_instruction(p
->addr
, p
->opcode
);
162 NOKPROBE_SYMBOL(arch_disarm_kprobe
);
164 void arch_remove_kprobe(struct kprobe
*p
)
167 free_insn_slot(p
->ainsn
.insn
, 0);
168 p
->ainsn
.insn
= NULL
;
171 NOKPROBE_SYMBOL(arch_remove_kprobe
);
173 static nokprobe_inline
void prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
175 enable_single_step(regs
);
178 * On powerpc we should single step on the original
179 * instruction even if the probed insn is a trap
180 * variant as values in regs could play a part in
181 * if the trap is taken or not
183 regs
->nip
= (unsigned long)p
->ainsn
.insn
;
186 static nokprobe_inline
void save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
188 kcb
->prev_kprobe
.kp
= kprobe_running();
189 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
190 kcb
->prev_kprobe
.saved_msr
= kcb
->kprobe_saved_msr
;
193 static nokprobe_inline
void restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
195 __this_cpu_write(current_kprobe
, kcb
->prev_kprobe
.kp
);
196 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
197 kcb
->kprobe_saved_msr
= kcb
->prev_kprobe
.saved_msr
;
200 static nokprobe_inline
void set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
201 struct kprobe_ctlblk
*kcb
)
203 __this_cpu_write(current_kprobe
, p
);
204 kcb
->kprobe_saved_msr
= regs
->msr
;
207 bool arch_kprobe_on_func_entry(unsigned long offset
)
209 #ifdef PPC64_ELF_ABI_v2
210 #ifdef CONFIG_KPROBES_ON_FTRACE
220 void arch_prepare_kretprobe(struct kretprobe_instance
*ri
, struct pt_regs
*regs
)
222 ri
->ret_addr
= (kprobe_opcode_t
*)regs
->link
;
224 /* Replace the return addr with trampoline addr */
225 regs
->link
= (unsigned long)kretprobe_trampoline
;
227 NOKPROBE_SYMBOL(arch_prepare_kretprobe
);
229 static int try_to_emulate(struct kprobe
*p
, struct pt_regs
*regs
)
232 unsigned int insn
= *p
->ainsn
.insn
;
234 /* regs->nip is also adjusted if emulate_step returns 1 */
235 ret
= emulate_step(regs
, insn
);
238 * Once this instruction has been boosted
239 * successfully, set the boostable flag
241 if (unlikely(p
->ainsn
.boostable
== 0))
242 p
->ainsn
.boostable
= 1;
243 } else if (ret
< 0) {
245 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
246 * So, we should never get here... but, its still
247 * good to catch them, just in case...
249 printk("Can't step on instruction %x\n", insn
);
253 * If we haven't previously emulated this instruction, then it
254 * can't be boosted. Note it down so we don't try to do so again.
256 * If, however, we had emulated this instruction in the past,
257 * then this is just an error with the current run (for
258 * instance, exceptions due to a load/store). We return 0 so
259 * that this is now single-stepped, but continue to try
260 * emulating it in subsequent probe hits.
262 if (unlikely(p
->ainsn
.boostable
!= 1))
263 p
->ainsn
.boostable
= -1;
268 NOKPROBE_SYMBOL(try_to_emulate
);
270 int kprobe_handler(struct pt_regs
*regs
)
274 unsigned int *addr
= (unsigned int *)regs
->nip
;
275 struct kprobe_ctlblk
*kcb
;
281 * We don't want to be preempted for the entire
282 * duration of kprobe processing
285 kcb
= get_kprobe_ctlblk();
287 /* Check we're not actually recursing */
288 if (kprobe_running()) {
289 p
= get_kprobe(addr
);
291 kprobe_opcode_t insn
= *p
->ainsn
.insn
;
292 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
294 /* Turn off 'trace' bits */
295 regs
->msr
&= ~MSR_SINGLESTEP
;
296 regs
->msr
|= kcb
->kprobe_saved_msr
;
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 kcb
->kprobe_status
= KPROBE_REENTER
;
309 if (p
->ainsn
.boostable
>= 0) {
310 ret
= try_to_emulate(p
, regs
);
313 restore_previous_kprobe(kcb
);
314 preempt_enable_no_resched();
318 prepare_singlestep(p
, regs
);
320 } else if (*addr
!= BREAKPOINT_INSTRUCTION
) {
321 /* If trap variant, then it belongs not to us */
322 kprobe_opcode_t cur_insn
= *addr
;
324 if (is_trap(cur_insn
))
326 /* The breakpoint instruction was removed by
327 * another cpu right after we hit, no further
328 * handling of this interrupt is appropriate
335 p
= get_kprobe(addr
);
337 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
339 * PowerPC has multiple variants of the "trap"
340 * instruction. If the current instruction is a
341 * trap variant, it could belong to someone else
343 kprobe_opcode_t cur_insn
= *addr
;
344 if (is_trap(cur_insn
))
347 * The breakpoint instruction was removed right
348 * after we hit it. Another cpu has removed
349 * either a probepoint or a debugger breakpoint
350 * at this address. In either case, no further
351 * handling of this interrupt is appropriate.
355 /* Not one of ours: let kernel handle it */
359 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
360 set_current_kprobe(p
, regs
, kcb
);
361 if (p
->pre_handler
&& p
->pre_handler(p
, regs
)) {
362 /* handler changed execution path, so skip ss setup */
363 reset_current_kprobe();
364 preempt_enable_no_resched();
368 if (p
->ainsn
.boostable
>= 0) {
369 ret
= try_to_emulate(p
, regs
);
373 p
->post_handler(p
, regs
, 0);
375 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
376 reset_current_kprobe();
377 preempt_enable_no_resched();
381 prepare_singlestep(p
, regs
);
382 kcb
->kprobe_status
= KPROBE_HIT_SS
;
386 preempt_enable_no_resched();
389 NOKPROBE_SYMBOL(kprobe_handler
);
392 * Function return probe trampoline:
393 * - init_kprobes() establishes a probepoint here
394 * - When the probed function returns, this probe
395 * causes the handlers to fire
397 asm(".global kretprobe_trampoline\n"
398 ".type kretprobe_trampoline, @function\n"
399 "kretprobe_trampoline:\n"
402 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
405 * Called when the probe at kretprobe trampoline is hit
407 static int trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
409 struct kretprobe_instance
*ri
= NULL
;
410 struct hlist_head
*head
, empty_rp
;
411 struct hlist_node
*tmp
;
412 unsigned long flags
, orig_ret_address
= 0;
413 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
415 INIT_HLIST_HEAD(&empty_rp
);
416 kretprobe_hash_lock(current
, &head
, &flags
);
419 * It is possible to have multiple instances associated with a given
420 * task either because an multiple functions in the call path
421 * have a return probe installed on them, and/or more than one return
422 * return probe was registered for a target function.
424 * We can handle this because:
425 * - instances are always inserted at the head of the list
426 * - when multiple return probes are registered for the same
427 * function, the first instance's ret_addr will point to the
428 * real return address, and all the rest will point to
429 * kretprobe_trampoline
431 hlist_for_each_entry_safe(ri
, tmp
, head
, hlist
) {
432 if (ri
->task
!= current
)
433 /* another task is sharing our hash bucket */
436 if (ri
->rp
&& ri
->rp
->handler
)
437 ri
->rp
->handler(ri
, regs
);
439 orig_ret_address
= (unsigned long)ri
->ret_addr
;
440 recycle_rp_inst(ri
, &empty_rp
);
442 if (orig_ret_address
!= trampoline_address
)
444 * This is the real return address. Any other
445 * instances associated with this task are for
446 * other calls deeper on the call stack
451 kretprobe_assert(ri
, orig_ret_address
, trampoline_address
);
454 * We get here through one of two paths:
455 * 1. by taking a trap -> kprobe_handler() -> here
456 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
458 * When going back through (1), we need regs->nip to be setup properly
459 * as it is used to determine the return address from the trap.
460 * For (2), since nip is not honoured with optprobes, we instead setup
461 * the link register properly so that the subsequent 'blr' in
462 * kretprobe_trampoline jumps back to the right instruction.
464 * For nip, we should set the address to the previous instruction since
465 * we end up emulating it in kprobe_handler(), which increments the nip
468 regs
->nip
= orig_ret_address
- 4;
469 regs
->link
= orig_ret_address
;
471 kretprobe_hash_unlock(current
, &flags
);
473 hlist_for_each_entry_safe(ri
, tmp
, &empty_rp
, hlist
) {
474 hlist_del(&ri
->hlist
);
480 NOKPROBE_SYMBOL(trampoline_probe_handler
);
483 * Called after single-stepping. p->addr is the address of the
484 * instruction whose first byte has been replaced by the "breakpoint"
485 * instruction. To avoid the SMP problems that can occur when we
486 * temporarily put back the original opcode to single-step, we
487 * single-stepped a copy of the instruction. The address of this
488 * copy is p->ainsn.insn.
490 int kprobe_post_handler(struct pt_regs
*regs
)
492 struct kprobe
*cur
= kprobe_running();
493 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
495 if (!cur
|| user_mode(regs
))
498 /* make sure we got here for instruction we have a kprobe on */
499 if (((unsigned long)cur
->ainsn
.insn
+ 4) != regs
->nip
)
502 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
503 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
504 cur
->post_handler(cur
, regs
, 0);
507 /* Adjust nip to after the single-stepped instruction */
508 regs
->nip
= (unsigned long)cur
->addr
+ 4;
509 regs
->msr
|= kcb
->kprobe_saved_msr
;
511 /*Restore back the original saved kprobes variables and continue. */
512 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
513 restore_previous_kprobe(kcb
);
516 reset_current_kprobe();
518 preempt_enable_no_resched();
521 * if somebody else is singlestepping across a probe point, msr
522 * will have DE/SE set, in which case, continue the remaining processing
523 * of do_debug, as if this is not a probe hit.
525 if (regs
->msr
& MSR_SINGLESTEP
)
530 NOKPROBE_SYMBOL(kprobe_post_handler
);
532 int kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
534 struct kprobe
*cur
= kprobe_running();
535 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
536 const struct exception_table_entry
*entry
;
538 switch(kcb
->kprobe_status
) {
542 * We are here because the instruction being single
543 * stepped caused a page fault. We reset the current
544 * kprobe and the nip points back to the probe address
545 * and allow the page fault handler to continue as a
548 regs
->nip
= (unsigned long)cur
->addr
;
549 regs
->msr
&= ~MSR_SINGLESTEP
; /* Turn off 'trace' bits */
550 regs
->msr
|= kcb
->kprobe_saved_msr
;
551 if (kcb
->kprobe_status
== KPROBE_REENTER
)
552 restore_previous_kprobe(kcb
);
554 reset_current_kprobe();
555 preempt_enable_no_resched();
557 case KPROBE_HIT_ACTIVE
:
558 case KPROBE_HIT_SSDONE
:
560 * We increment the nmissed count for accounting,
561 * we can also use npre/npostfault count for accounting
562 * these specific fault cases.
564 kprobes_inc_nmissed_count(cur
);
567 * We come here because instructions in the pre/post
568 * handler caused the page_fault, this could happen
569 * if handler tries to access user space by
570 * copy_from_user(), get_user() etc. Let the
571 * user-specified handler try to fix it first.
573 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
577 * In case the user-specified fault handler returned
578 * zero, try to fix up.
580 if ((entry
= search_exception_tables(regs
->nip
)) != NULL
) {
581 regs
->nip
= extable_fixup(entry
);
586 * fixup_exception() could not handle it,
587 * Let do_page_fault() fix it.
595 NOKPROBE_SYMBOL(kprobe_fault_handler
);
597 unsigned long arch_deref_entry_point(void *entry
)
599 #ifdef PPC64_ELF_ABI_v1
600 if (!kernel_text_address((unsigned long)entry
))
601 return ppc_global_function_entry(entry
);
604 return (unsigned long)entry
;
606 NOKPROBE_SYMBOL(arch_deref_entry_point
);
608 static struct kprobe trampoline_p
= {
609 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
610 .pre_handler
= trampoline_probe_handler
613 int __init
arch_init_kprobes(void)
615 return register_kprobe(&trampoline_p
);
618 int arch_trampoline_kprobe(struct kprobe
*p
)
620 if (p
->addr
== (kprobe_opcode_t
*)&kretprobe_trampoline
)
625 NOKPROBE_SYMBOL(arch_trampoline_kprobe
);