2 * Kernel Probes (KProbes)
3 * arch/i386/kernel/kprobes.c
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19 * Copyright (C) IBM Corporation, 2002, 2004
21 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
22 * Probes initial implementation ( includes contributions from
24 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
25 * interface to access function arguments.
26 * 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
27 * <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
28 * <prasanna@in.ibm.com> added function-return probes.
31 #include <linux/config.h>
32 #include <linux/kprobes.h>
33 #include <linux/ptrace.h>
34 #include <linux/preempt.h>
35 #include <asm/cacheflush.h>
36 #include <asm/kdebug.h>
39 void jprobe_return_end(void);
41 DEFINE_PER_CPU(struct kprobe
*, current_kprobe
) = NULL
;
42 DEFINE_PER_CPU(struct kprobe_ctlblk
, kprobe_ctlblk
);
45 * returns non-zero if opcode modifies the interrupt flag.
47 static inline int is_IF_modifier(kprobe_opcode_t opcode
)
52 case 0xcf: /* iret/iretd */
53 case 0x9d: /* popf/popfd */
59 int __kprobes
arch_prepare_kprobe(struct kprobe
*p
)
61 /* insn: must be on special executable page on i386. */
62 p
->ainsn
.insn
= get_insn_slot();
66 memcpy(p
->ainsn
.insn
, p
->addr
, MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
71 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
73 *p
->addr
= BREAKPOINT_INSTRUCTION
;
74 flush_icache_range((unsigned long) p
->addr
,
75 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
78 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
81 flush_icache_range((unsigned long) p
->addr
,
82 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
85 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
88 free_insn_slot(p
->ainsn
.insn
);
92 static inline void save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
94 kcb
->prev_kprobe
.kp
= kprobe_running();
95 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
96 kcb
->prev_kprobe
.old_eflags
= kcb
->kprobe_old_eflags
;
97 kcb
->prev_kprobe
.saved_eflags
= kcb
->kprobe_saved_eflags
;
100 static inline void restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
102 __get_cpu_var(current_kprobe
) = kcb
->prev_kprobe
.kp
;
103 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
104 kcb
->kprobe_old_eflags
= kcb
->prev_kprobe
.old_eflags
;
105 kcb
->kprobe_saved_eflags
= kcb
->prev_kprobe
.saved_eflags
;
108 static inline void set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
109 struct kprobe_ctlblk
*kcb
)
111 __get_cpu_var(current_kprobe
) = p
;
112 kcb
->kprobe_saved_eflags
= kcb
->kprobe_old_eflags
113 = (regs
->eflags
& (TF_MASK
| IF_MASK
));
114 if (is_IF_modifier(p
->opcode
))
115 kcb
->kprobe_saved_eflags
&= ~IF_MASK
;
118 static inline void prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
120 regs
->eflags
|= TF_MASK
;
121 regs
->eflags
&= ~IF_MASK
;
122 /*single step inline if the instruction is an int3*/
123 if (p
->opcode
== BREAKPOINT_INSTRUCTION
)
124 regs
->eip
= (unsigned long)p
->addr
;
126 regs
->eip
= (unsigned long)p
->ainsn
.insn
;
129 /* Called with kretprobe_lock held */
130 void __kprobes
arch_prepare_kretprobe(struct kretprobe
*rp
,
131 struct pt_regs
*regs
)
133 unsigned long *sara
= (unsigned long *)®s
->esp
;
134 struct kretprobe_instance
*ri
;
136 if ((ri
= get_free_rp_inst(rp
)) != NULL
) {
139 ri
->ret_addr
= (kprobe_opcode_t
*) *sara
;
141 /* Replace the return addr with trampoline addr */
142 *sara
= (unsigned long) &kretprobe_trampoline
;
151 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
152 * remain disabled thorough out this function.
154 static int __kprobes
kprobe_handler(struct pt_regs
*regs
)
158 kprobe_opcode_t
*addr
= NULL
;
160 struct kprobe_ctlblk
*kcb
;
163 * We don't want to be preempted for the entire
164 * duration of kprobe processing
167 kcb
= get_kprobe_ctlblk();
169 /* Check if the application is using LDT entry for its code segment and
170 * calculate the address by reading the base address from the LDT entry.
172 if ((regs
->xcs
& 4) && (current
->mm
)) {
173 lp
= (unsigned long *) ((unsigned long)((regs
->xcs
>> 3) * 8)
174 + (char *) current
->mm
->context
.ldt
);
175 addr
= (kprobe_opcode_t
*) (get_desc_base(lp
) + regs
->eip
-
176 sizeof(kprobe_opcode_t
));
178 addr
= (kprobe_opcode_t
*)(regs
->eip
- sizeof(kprobe_opcode_t
));
180 /* Check we're not actually recursing */
181 if (kprobe_running()) {
182 p
= get_kprobe(addr
);
184 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
185 *p
->ainsn
.insn
== BREAKPOINT_INSTRUCTION
) {
186 regs
->eflags
&= ~TF_MASK
;
187 regs
->eflags
|= kcb
->kprobe_saved_eflags
;
190 /* We have reentered the kprobe_handler(), since
191 * another probe was hit while within the handler.
192 * We here save the original kprobes variables and
193 * just single step on the instruction of the new probe
194 * without calling any user handlers.
196 save_previous_kprobe(kcb
);
197 set_current_kprobe(p
, regs
, kcb
);
198 kprobes_inc_nmissed_count(p
);
199 prepare_singlestep(p
, regs
);
200 kcb
->kprobe_status
= KPROBE_REENTER
;
203 if (regs
->eflags
& VM_MASK
) {
204 /* We are in virtual-8086 mode. Return 0 */
207 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
208 /* The breakpoint instruction was removed by
209 * another cpu right after we hit, no further
210 * handling of this interrupt is appropriate
212 regs
->eip
-= sizeof(kprobe_opcode_t
);
216 p
= __get_cpu_var(current_kprobe
);
217 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
224 p
= get_kprobe(addr
);
226 if (regs
->eflags
& VM_MASK
) {
227 /* We are in virtual-8086 mode. Return 0 */
231 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
233 * The breakpoint instruction was removed right
234 * after we hit it. Another cpu has removed
235 * either a probepoint or a debugger breakpoint
236 * at this address. In either case, no further
237 * handling of this interrupt is appropriate.
238 * Back up over the (now missing) int3 and run
239 * the original instruction.
241 regs
->eip
-= sizeof(kprobe_opcode_t
);
244 /* Not one of ours: let kernel handle it */
248 set_current_kprobe(p
, regs
, kcb
);
249 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
251 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
252 /* handler has already set things up, so skip ss setup */
256 prepare_singlestep(p
, regs
);
257 kcb
->kprobe_status
= KPROBE_HIT_SS
;
261 preempt_enable_no_resched();
266 * For function-return probes, init_kprobes() establishes a probepoint
267 * here. When a retprobed function returns, this probe is hit and
268 * trampoline_probe_handler() runs, calling the kretprobe's handler.
270 void kretprobe_trampoline_holder(void)
272 asm volatile ( ".global kretprobe_trampoline\n"
273 "kretprobe_trampoline: \n"
278 * Called when we hit the probe point at kretprobe_trampoline
280 int __kprobes
trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
282 struct kretprobe_instance
*ri
= NULL
;
283 struct hlist_head
*head
;
284 struct hlist_node
*node
, *tmp
;
285 unsigned long flags
, orig_ret_address
= 0;
286 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
288 spin_lock_irqsave(&kretprobe_lock
, flags
);
289 head
= kretprobe_inst_table_head(current
);
292 * It is possible to have multiple instances associated with a given
293 * task either because an multiple functions in the call path
294 * have a return probe installed on them, and/or more then one return
295 * return probe was registered for a target function.
297 * We can handle this because:
298 * - instances are always inserted at the head of the list
299 * - when multiple return probes are registered for the same
300 * function, the first instance's ret_addr will point to the
301 * real return address, and all the rest will point to
302 * kretprobe_trampoline
304 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
305 if (ri
->task
!= current
)
306 /* another task is sharing our hash bucket */
309 if (ri
->rp
&& ri
->rp
->handler
)
310 ri
->rp
->handler(ri
, regs
);
312 orig_ret_address
= (unsigned long)ri
->ret_addr
;
315 if (orig_ret_address
!= trampoline_address
)
317 * This is the real return address. Any other
318 * instances associated with this task are for
319 * other calls deeper on the call stack
324 BUG_ON(!orig_ret_address
|| (orig_ret_address
== trampoline_address
));
325 regs
->eip
= orig_ret_address
;
327 reset_current_kprobe();
328 spin_unlock_irqrestore(&kretprobe_lock
, flags
);
329 preempt_enable_no_resched();
332 * By returning a non-zero value, we are telling
333 * kprobe_handler() that we don't want the post_handler
334 * to run (and have re-enabled preemption)
340 * Called after single-stepping. p->addr is the address of the
341 * instruction whose first byte has been replaced by the "int 3"
342 * instruction. To avoid the SMP problems that can occur when we
343 * temporarily put back the original opcode to single-step, we
344 * single-stepped a copy of the instruction. The address of this
345 * copy is p->ainsn.insn.
347 * This function prepares to return from the post-single-step
348 * interrupt. We have to fix up the stack as follows:
350 * 0) Except in the case of absolute or indirect jump or call instructions,
351 * the new eip is relative to the copied instruction. We need to make
352 * it relative to the original instruction.
354 * 1) If the single-stepped instruction was pushfl, then the TF and IF
355 * flags are set in the just-pushed eflags, and may need to be cleared.
357 * 2) If the single-stepped instruction was a call, the return address
358 * that is atop the stack is the address following the copied instruction.
359 * We need to make it the address following the original instruction.
361 static void __kprobes
resume_execution(struct kprobe
*p
,
362 struct pt_regs
*regs
, struct kprobe_ctlblk
*kcb
)
364 unsigned long *tos
= (unsigned long *)®s
->esp
;
365 unsigned long next_eip
= 0;
366 unsigned long copy_eip
= (unsigned long)p
->ainsn
.insn
;
367 unsigned long orig_eip
= (unsigned long)p
->addr
;
369 switch (p
->ainsn
.insn
[0]) {
370 case 0x9c: /* pushfl */
371 *tos
&= ~(TF_MASK
| IF_MASK
);
372 *tos
|= kcb
->kprobe_old_eflags
;
374 case 0xc3: /* ret/lret */
378 regs
->eflags
&= ~TF_MASK
;
379 /* eip is already adjusted, no more changes required*/
381 case 0xe8: /* call relative - Fix return addr */
382 *tos
= orig_eip
+ (*tos
- copy_eip
);
385 if ((p
->ainsn
.insn
[1] & 0x30) == 0x10) {
386 /* call absolute, indirect */
387 /* Fix return addr; eip is correct. */
388 next_eip
= regs
->eip
;
389 *tos
= orig_eip
+ (*tos
- copy_eip
);
390 } else if (((p
->ainsn
.insn
[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
391 ((p
->ainsn
.insn
[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
392 /* eip is correct. */
393 next_eip
= regs
->eip
;
396 case 0xea: /* jmp absolute -- eip is correct */
397 next_eip
= regs
->eip
;
403 regs
->eflags
&= ~TF_MASK
;
405 regs
->eip
= next_eip
;
407 regs
->eip
= orig_eip
+ (regs
->eip
- copy_eip
);
412 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
413 * remain disabled thoroughout this function.
415 static inline int post_kprobe_handler(struct pt_regs
*regs
)
417 struct kprobe
*cur
= kprobe_running();
418 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
423 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
424 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
425 cur
->post_handler(cur
, regs
, 0);
428 resume_execution(cur
, regs
, kcb
);
429 regs
->eflags
|= kcb
->kprobe_saved_eflags
;
431 /*Restore back the original saved kprobes variables and continue. */
432 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
433 restore_previous_kprobe(kcb
);
436 reset_current_kprobe();
438 preempt_enable_no_resched();
441 * if somebody else is singlestepping across a probe point, eflags
442 * will have TF set, in which case, continue the remaining processing
443 * of do_debug, as if this is not a probe hit.
445 if (regs
->eflags
& TF_MASK
)
451 static inline int kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
453 struct kprobe
*cur
= kprobe_running();
454 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
456 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
459 if (kcb
->kprobe_status
& KPROBE_HIT_SS
) {
460 resume_execution(cur
, regs
, kcb
);
461 regs
->eflags
|= kcb
->kprobe_old_eflags
;
463 reset_current_kprobe();
464 preempt_enable_no_resched();
470 * Wrapper routine to for handling exceptions.
472 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
473 unsigned long val
, void *data
)
475 struct die_args
*args
= (struct die_args
*)data
;
476 int ret
= NOTIFY_DONE
;
480 if (kprobe_handler(args
->regs
))
484 if (post_kprobe_handler(args
->regs
))
489 /* kprobe_running() needs smp_processor_id() */
491 if (kprobe_running() &&
492 kprobe_fault_handler(args
->regs
, args
->trapnr
))
502 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
504 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
506 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
508 kcb
->jprobe_saved_regs
= *regs
;
509 kcb
->jprobe_saved_esp
= ®s
->esp
;
510 addr
= (unsigned long)(kcb
->jprobe_saved_esp
);
513 * TBD: As Linus pointed out, gcc assumes that the callee
514 * owns the argument space and could overwrite it, e.g.
515 * tailcall optimization. So, to be absolutely safe
516 * we also save and restore enough stack bytes to cover
519 memcpy(kcb
->jprobes_stack
, (kprobe_opcode_t
*)addr
,
520 MIN_STACK_SIZE(addr
));
521 regs
->eflags
&= ~IF_MASK
;
522 regs
->eip
= (unsigned long)(jp
->entry
);
526 void __kprobes
jprobe_return(void)
528 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
530 asm volatile (" xchgl %%ebx,%%esp \n"
532 " .globl jprobe_return_end \n"
533 " jprobe_return_end: \n"
535 (kcb
->jprobe_saved_esp
):"memory");
538 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
540 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
541 u8
*addr
= (u8
*) (regs
->eip
- 1);
542 unsigned long stack_addr
= (unsigned long)(kcb
->jprobe_saved_esp
);
543 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
545 if ((addr
> (u8
*) jprobe_return
) && (addr
< (u8
*) jprobe_return_end
)) {
546 if (®s
->esp
!= kcb
->jprobe_saved_esp
) {
547 struct pt_regs
*saved_regs
=
548 container_of(kcb
->jprobe_saved_esp
,
549 struct pt_regs
, esp
);
550 printk("current esp %p does not match saved esp %p\n",
551 ®s
->esp
, kcb
->jprobe_saved_esp
);
552 printk("Saved registers for jprobe %p\n", jp
);
553 show_registers(saved_regs
);
554 printk("Current registers\n");
555 show_registers(regs
);
558 *regs
= kcb
->jprobe_saved_regs
;
559 memcpy((kprobe_opcode_t
*) stack_addr
, kcb
->jprobes_stack
,
560 MIN_STACK_SIZE(stack_addr
));
561 preempt_enable_no_resched();
567 static struct kprobe trampoline_p
= {
568 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
569 .pre_handler
= trampoline_probe_handler
572 int __init
arch_init_kprobes(void)
574 return register_kprobe(&trampoline_p
);