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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
)
64 void __kprobes
arch_copy_kprobe(struct kprobe
*p
)
66 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
)
88 static inline void save_previous_kprobe(struct kprobe_ctlblk
*kcb
)
90 kcb
->prev_kprobe
.kp
= kprobe_running();
91 kcb
->prev_kprobe
.status
= kcb
->kprobe_status
;
92 kcb
->prev_kprobe
.old_eflags
= kcb
->kprobe_old_eflags
;
93 kcb
->prev_kprobe
.saved_eflags
= kcb
->kprobe_saved_eflags
;
96 static inline void restore_previous_kprobe(struct kprobe_ctlblk
*kcb
)
98 __get_cpu_var(current_kprobe
) = kcb
->prev_kprobe
.kp
;
99 kcb
->kprobe_status
= kcb
->prev_kprobe
.status
;
100 kcb
->kprobe_old_eflags
= kcb
->prev_kprobe
.old_eflags
;
101 kcb
->kprobe_saved_eflags
= kcb
->prev_kprobe
.saved_eflags
;
104 static inline void set_current_kprobe(struct kprobe
*p
, struct pt_regs
*regs
,
105 struct kprobe_ctlblk
*kcb
)
107 __get_cpu_var(current_kprobe
) = p
;
108 kcb
->kprobe_saved_eflags
= kcb
->kprobe_old_eflags
109 = (regs
->eflags
& (TF_MASK
| IF_MASK
));
110 if (is_IF_modifier(p
->opcode
))
111 kcb
->kprobe_saved_eflags
&= ~IF_MASK
;
114 static inline void prepare_singlestep(struct kprobe
*p
, struct pt_regs
*regs
)
116 regs
->eflags
|= TF_MASK
;
117 regs
->eflags
&= ~IF_MASK
;
118 /*single step inline if the instruction is an int3*/
119 if (p
->opcode
== BREAKPOINT_INSTRUCTION
)
120 regs
->eip
= (unsigned long)p
->addr
;
122 regs
->eip
= (unsigned long)&p
->ainsn
.insn
;
125 /* Called with kretprobe_lock held */
126 void __kprobes
arch_prepare_kretprobe(struct kretprobe
*rp
,
127 struct pt_regs
*regs
)
129 unsigned long *sara
= (unsigned long *)®s
->esp
;
130 struct kretprobe_instance
*ri
;
132 if ((ri
= get_free_rp_inst(rp
)) != NULL
) {
135 ri
->ret_addr
= (kprobe_opcode_t
*) *sara
;
137 /* Replace the return addr with trampoline addr */
138 *sara
= (unsigned long) &kretprobe_trampoline
;
147 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
148 * remain disabled thorough out this function.
150 static int __kprobes
kprobe_handler(struct pt_regs
*regs
)
154 kprobe_opcode_t
*addr
= NULL
;
156 struct kprobe_ctlblk
*kcb
;
159 * We don't want to be preempted for the entire
160 * duration of kprobe processing
163 kcb
= get_kprobe_ctlblk();
165 /* Check if the application is using LDT entry for its code segment and
166 * calculate the address by reading the base address from the LDT entry.
168 if ((regs
->xcs
& 4) && (current
->mm
)) {
169 lp
= (unsigned long *) ((unsigned long)((regs
->xcs
>> 3) * 8)
170 + (char *) current
->mm
->context
.ldt
);
171 addr
= (kprobe_opcode_t
*) (get_desc_base(lp
) + regs
->eip
-
172 sizeof(kprobe_opcode_t
));
174 addr
= (kprobe_opcode_t
*)(regs
->eip
- sizeof(kprobe_opcode_t
));
176 /* Check we're not actually recursing */
177 if (kprobe_running()) {
178 p
= get_kprobe(addr
);
180 if (kcb
->kprobe_status
== KPROBE_HIT_SS
&&
181 *p
->ainsn
.insn
== BREAKPOINT_INSTRUCTION
) {
182 regs
->eflags
&= ~TF_MASK
;
183 regs
->eflags
|= kcb
->kprobe_saved_eflags
;
186 /* We have reentered the kprobe_handler(), since
187 * another probe was hit while within the handler.
188 * We here save the original kprobes variables and
189 * just single step on the instruction of the new probe
190 * without calling any user handlers.
192 save_previous_kprobe(kcb
);
193 set_current_kprobe(p
, regs
, kcb
);
195 prepare_singlestep(p
, regs
);
196 kcb
->kprobe_status
= KPROBE_REENTER
;
199 p
= __get_cpu_var(current_kprobe
);
200 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
207 p
= get_kprobe(addr
);
209 if (regs
->eflags
& VM_MASK
) {
210 /* We are in virtual-8086 mode. Return 0 */
214 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
216 * The breakpoint instruction was removed right
217 * after we hit it. Another cpu has removed
218 * either a probepoint or a debugger breakpoint
219 * at this address. In either case, no further
220 * handling of this interrupt is appropriate.
221 * Back up over the (now missing) int3 and run
222 * the original instruction.
224 regs
->eip
-= sizeof(kprobe_opcode_t
);
227 /* Not one of ours: let kernel handle it */
231 set_current_kprobe(p
, regs
, kcb
);
232 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
234 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
235 /* handler has already set things up, so skip ss setup */
239 prepare_singlestep(p
, regs
);
240 kcb
->kprobe_status
= KPROBE_HIT_SS
;
244 preempt_enable_no_resched();
249 * For function-return probes, init_kprobes() establishes a probepoint
250 * here. When a retprobed function returns, this probe is hit and
251 * trampoline_probe_handler() runs, calling the kretprobe's handler.
253 void kretprobe_trampoline_holder(void)
255 asm volatile ( ".global kretprobe_trampoline\n"
256 "kretprobe_trampoline: \n"
261 * Called when we hit the probe point at kretprobe_trampoline
263 int __kprobes
trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
265 struct kretprobe_instance
*ri
= NULL
;
266 struct hlist_head
*head
;
267 struct hlist_node
*node
, *tmp
;
268 unsigned long flags
, orig_ret_address
= 0;
269 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
271 spin_lock_irqsave(&kretprobe_lock
, flags
);
272 head
= kretprobe_inst_table_head(current
);
275 * It is possible to have multiple instances associated with a given
276 * task either because an multiple functions in the call path
277 * have a return probe installed on them, and/or more then one return
278 * return probe was registered for a target function.
280 * We can handle this because:
281 * - instances are always inserted at the head of the list
282 * - when multiple return probes are registered for the same
283 * function, the first instance's ret_addr will point to the
284 * real return address, and all the rest will point to
285 * kretprobe_trampoline
287 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
288 if (ri
->task
!= current
)
289 /* another task is sharing our hash bucket */
292 if (ri
->rp
&& ri
->rp
->handler
)
293 ri
->rp
->handler(ri
, regs
);
295 orig_ret_address
= (unsigned long)ri
->ret_addr
;
298 if (orig_ret_address
!= trampoline_address
)
300 * This is the real return address. Any other
301 * instances associated with this task are for
302 * other calls deeper on the call stack
307 BUG_ON(!orig_ret_address
|| (orig_ret_address
== trampoline_address
));
308 regs
->eip
= orig_ret_address
;
310 reset_current_kprobe();
311 spin_unlock_irqrestore(&kretprobe_lock
, flags
);
312 preempt_enable_no_resched();
315 * By returning a non-zero value, we are telling
316 * kprobe_handler() that we don't want the post_handler
317 * to run (and have re-enabled preemption)
323 * Called after single-stepping. p->addr is the address of the
324 * instruction whose first byte has been replaced by the "int 3"
325 * instruction. To avoid the SMP problems that can occur when we
326 * temporarily put back the original opcode to single-step, we
327 * single-stepped a copy of the instruction. The address of this
328 * copy is p->ainsn.insn.
330 * This function prepares to return from the post-single-step
331 * interrupt. We have to fix up the stack as follows:
333 * 0) Except in the case of absolute or indirect jump or call instructions,
334 * the new eip is relative to the copied instruction. We need to make
335 * it relative to the original instruction.
337 * 1) If the single-stepped instruction was pushfl, then the TF and IF
338 * flags are set in the just-pushed eflags, and may need to be cleared.
340 * 2) If the single-stepped instruction was a call, the return address
341 * that is atop the stack is the address following the copied instruction.
342 * We need to make it the address following the original instruction.
344 static void __kprobes
resume_execution(struct kprobe
*p
,
345 struct pt_regs
*regs
, struct kprobe_ctlblk
*kcb
)
347 unsigned long *tos
= (unsigned long *)®s
->esp
;
348 unsigned long next_eip
= 0;
349 unsigned long copy_eip
= (unsigned long)&p
->ainsn
.insn
;
350 unsigned long orig_eip
= (unsigned long)p
->addr
;
352 switch (p
->ainsn
.insn
[0]) {
353 case 0x9c: /* pushfl */
354 *tos
&= ~(TF_MASK
| IF_MASK
);
355 *tos
|= kcb
->kprobe_old_eflags
;
357 case 0xc3: /* ret/lret */
361 regs
->eflags
&= ~TF_MASK
;
362 /* eip is already adjusted, no more changes required*/
364 case 0xe8: /* call relative - Fix return addr */
365 *tos
= orig_eip
+ (*tos
- copy_eip
);
368 if ((p
->ainsn
.insn
[1] & 0x30) == 0x10) {
369 /* call absolute, indirect */
370 /* Fix return addr; eip is correct. */
371 next_eip
= regs
->eip
;
372 *tos
= orig_eip
+ (*tos
- copy_eip
);
373 } else if (((p
->ainsn
.insn
[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
374 ((p
->ainsn
.insn
[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
375 /* eip is correct. */
376 next_eip
= regs
->eip
;
379 case 0xea: /* jmp absolute -- eip is correct */
380 next_eip
= regs
->eip
;
386 regs
->eflags
&= ~TF_MASK
;
388 regs
->eip
= next_eip
;
390 regs
->eip
= orig_eip
+ (regs
->eip
- copy_eip
);
395 * Interrupts are disabled on entry as trap1 is an interrupt gate and they
396 * remain disabled thoroughout this function.
398 static inline int post_kprobe_handler(struct pt_regs
*regs
)
400 struct kprobe
*cur
= kprobe_running();
401 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
406 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
407 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
408 cur
->post_handler(cur
, regs
, 0);
411 resume_execution(cur
, regs
, kcb
);
412 regs
->eflags
|= kcb
->kprobe_saved_eflags
;
414 /*Restore back the original saved kprobes variables and continue. */
415 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
416 restore_previous_kprobe(kcb
);
419 reset_current_kprobe();
421 preempt_enable_no_resched();
424 * if somebody else is singlestepping across a probe point, eflags
425 * will have TF set, in which case, continue the remaining processing
426 * of do_debug, as if this is not a probe hit.
428 if (regs
->eflags
& TF_MASK
)
434 static inline int kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
436 struct kprobe
*cur
= kprobe_running();
437 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
439 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
442 if (kcb
->kprobe_status
& KPROBE_HIT_SS
) {
443 resume_execution(cur
, regs
, kcb
);
444 regs
->eflags
|= kcb
->kprobe_old_eflags
;
446 reset_current_kprobe();
447 preempt_enable_no_resched();
453 * Wrapper routine to for handling exceptions.
455 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
456 unsigned long val
, void *data
)
458 struct die_args
*args
= (struct die_args
*)data
;
459 int ret
= NOTIFY_DONE
;
463 if (kprobe_handler(args
->regs
))
467 if (post_kprobe_handler(args
->regs
))
472 /* kprobe_running() needs smp_processor_id() */
474 if (kprobe_running() &&
475 kprobe_fault_handler(args
->regs
, args
->trapnr
))
485 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
487 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
489 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
491 kcb
->jprobe_saved_regs
= *regs
;
492 kcb
->jprobe_saved_esp
= ®s
->esp
;
493 addr
= (unsigned long)(kcb
->jprobe_saved_esp
);
496 * TBD: As Linus pointed out, gcc assumes that the callee
497 * owns the argument space and could overwrite it, e.g.
498 * tailcall optimization. So, to be absolutely safe
499 * we also save and restore enough stack bytes to cover
502 memcpy(kcb
->jprobes_stack
, (kprobe_opcode_t
*)addr
,
503 MIN_STACK_SIZE(addr
));
504 regs
->eflags
&= ~IF_MASK
;
505 regs
->eip
= (unsigned long)(jp
->entry
);
509 void __kprobes
jprobe_return(void)
511 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
513 asm volatile (" xchgl %%ebx,%%esp \n"
515 " .globl jprobe_return_end \n"
516 " jprobe_return_end: \n"
518 (kcb
->jprobe_saved_esp
):"memory");
521 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
523 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
524 u8
*addr
= (u8
*) (regs
->eip
- 1);
525 unsigned long stack_addr
= (unsigned long)(kcb
->jprobe_saved_esp
);
526 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
528 if ((addr
> (u8
*) jprobe_return
) && (addr
< (u8
*) jprobe_return_end
)) {
529 if (®s
->esp
!= kcb
->jprobe_saved_esp
) {
530 struct pt_regs
*saved_regs
=
531 container_of(kcb
->jprobe_saved_esp
,
532 struct pt_regs
, esp
);
533 printk("current esp %p does not match saved esp %p\n",
534 ®s
->esp
, kcb
->jprobe_saved_esp
);
535 printk("Saved registers for jprobe %p\n", jp
);
536 show_registers(saved_regs
);
537 printk("Current registers\n");
538 show_registers(regs
);
541 *regs
= kcb
->jprobe_saved_regs
;
542 memcpy((kprobe_opcode_t
*) stack_addr
, kcb
->jprobes_stack
,
543 MIN_STACK_SIZE(stack_addr
));
544 preempt_enable_no_resched();
550 static struct kprobe trampoline_p
= {
551 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
552 .pre_handler
= trampoline_probe_handler
555 int __init
arch_init_kprobes(void)
557 return register_kprobe(&trampoline_p
);