2 * Kernel Probes (KProbes)
3 * arch/ppc64/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 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
30 #include <linux/config.h>
31 #include <linux/kprobes.h>
32 #include <linux/ptrace.h>
33 #include <linux/preempt.h>
34 #include <asm/cacheflush.h>
35 #include <asm/kdebug.h>
36 #include <asm/sstep.h>
38 static DECLARE_MUTEX(kprobe_mutex
);
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 */
58 p
->ainsn
.insn
= get_insn_slot();
65 memcpy(p
->ainsn
.insn
, p
->addr
, MAX_INSN_SIZE
* sizeof(kprobe_opcode_t
));
72 void __kprobes
arch_arm_kprobe(struct kprobe
*p
)
74 *p
->addr
= BREAKPOINT_INSTRUCTION
;
75 flush_icache_range((unsigned long) p
->addr
,
76 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
79 void __kprobes
arch_disarm_kprobe(struct kprobe
*p
)
82 flush_icache_range((unsigned long) p
->addr
,
83 (unsigned long) p
->addr
+ sizeof(kprobe_opcode_t
));
86 void __kprobes
arch_remove_kprobe(struct kprobe
*p
)
88 free_insn_slot(p
->ainsn
.insn
);
91 static inline void 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 inline void 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 inline void 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 inline void 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 inline int 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 p
= __get_cpu_var(current_kprobe
);
184 if (p
->break_handler
&& p
->break_handler(p
, regs
)) {
191 p
= get_kprobe(addr
);
193 if (*addr
!= BREAKPOINT_INSTRUCTION
) {
195 * PowerPC has multiple variants of the "trap"
196 * instruction. If the current instruction is a
197 * trap variant, it could belong to someone else
199 kprobe_opcode_t cur_insn
= *addr
;
200 if (is_trap(cur_insn
))
203 * The breakpoint instruction was removed right
204 * after we hit it. Another cpu has removed
205 * either a probepoint or a debugger breakpoint
206 * at this address. In either case, no further
207 * handling of this interrupt is appropriate.
211 /* Not one of ours: let kernel handle it */
215 kcb
->kprobe_status
= KPROBE_HIT_ACTIVE
;
216 set_current_kprobe(p
, regs
, kcb
);
217 if (p
->pre_handler
&& p
->pre_handler(p
, regs
))
218 /* handler has already set things up, so skip ss setup */
222 prepare_singlestep(p
, regs
);
223 kcb
->kprobe_status
= KPROBE_HIT_SS
;
227 preempt_enable_no_resched();
232 * Function return probe trampoline:
233 * - init_kprobes() establishes a probepoint here
234 * - When the probed function returns, this probe
235 * causes the handlers to fire
237 void kretprobe_trampoline_holder(void)
239 asm volatile(".global kretprobe_trampoline\n"
240 "kretprobe_trampoline:\n"
245 * Called when the probe at kretprobe trampoline is hit
247 int __kprobes
trampoline_probe_handler(struct kprobe
*p
, struct pt_regs
*regs
)
249 struct kretprobe_instance
*ri
= NULL
;
250 struct hlist_head
*head
;
251 struct hlist_node
*node
, *tmp
;
252 unsigned long flags
, orig_ret_address
= 0;
253 unsigned long trampoline_address
=(unsigned long)&kretprobe_trampoline
;
255 spin_lock_irqsave(&kretprobe_lock
, flags
);
256 head
= kretprobe_inst_table_head(current
);
259 * It is possible to have multiple instances associated with a given
260 * task either because an multiple functions in the call path
261 * have a return probe installed on them, and/or more then one return
262 * return probe was registered for a target function.
264 * We can handle this because:
265 * - instances are always inserted at the head of the list
266 * - when multiple return probes are registered for the same
267 * function, the first instance's ret_addr will point to the
268 * real return address, and all the rest will point to
269 * kretprobe_trampoline
271 hlist_for_each_entry_safe(ri
, node
, tmp
, head
, hlist
) {
272 if (ri
->task
!= current
)
273 /* another task is sharing our hash bucket */
276 if (ri
->rp
&& ri
->rp
->handler
)
277 ri
->rp
->handler(ri
, regs
);
279 orig_ret_address
= (unsigned long)ri
->ret_addr
;
282 if (orig_ret_address
!= trampoline_address
)
284 * This is the real return address. Any other
285 * instances associated with this task are for
286 * other calls deeper on the call stack
291 BUG_ON(!orig_ret_address
|| (orig_ret_address
== trampoline_address
));
292 regs
->nip
= orig_ret_address
;
294 reset_current_kprobe();
295 spin_unlock_irqrestore(&kretprobe_lock
, flags
);
296 preempt_enable_no_resched();
299 * By returning a non-zero value, we are telling
300 * kprobe_handler() that we don't want the post_handler
301 * to run (and have re-enabled preemption)
307 * Called after single-stepping. p->addr is the address of the
308 * instruction whose first byte has been replaced by the "breakpoint"
309 * instruction. To avoid the SMP problems that can occur when we
310 * temporarily put back the original opcode to single-step, we
311 * single-stepped a copy of the instruction. The address of this
312 * copy is p->ainsn.insn.
314 static void __kprobes
resume_execution(struct kprobe
*p
, struct pt_regs
*regs
)
317 unsigned int insn
= *p
->ainsn
.insn
;
319 regs
->nip
= (unsigned long)p
->addr
;
320 ret
= emulate_step(regs
, insn
);
322 regs
->nip
= (unsigned long)p
->addr
+ 4;
325 static inline int post_kprobe_handler(struct pt_regs
*regs
)
327 struct kprobe
*cur
= kprobe_running();
328 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
333 if ((kcb
->kprobe_status
!= KPROBE_REENTER
) && cur
->post_handler
) {
334 kcb
->kprobe_status
= KPROBE_HIT_SSDONE
;
335 cur
->post_handler(cur
, regs
, 0);
338 resume_execution(cur
, regs
);
339 regs
->msr
|= kcb
->kprobe_saved_msr
;
341 /*Restore back the original saved kprobes variables and continue. */
342 if (kcb
->kprobe_status
== KPROBE_REENTER
) {
343 restore_previous_kprobe(kcb
);
346 reset_current_kprobe();
348 preempt_enable_no_resched();
351 * if somebody else is singlestepping across a probe point, msr
352 * will have SE set, in which case, continue the remaining processing
353 * of do_debug, as if this is not a probe hit.
355 if (regs
->msr
& MSR_SE
)
361 static inline int kprobe_fault_handler(struct pt_regs
*regs
, int trapnr
)
363 struct kprobe
*cur
= kprobe_running();
364 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
366 if (cur
->fault_handler
&& cur
->fault_handler(cur
, regs
, trapnr
))
369 if (kcb
->kprobe_status
& KPROBE_HIT_SS
) {
370 resume_execution(cur
, regs
);
371 regs
->msr
&= ~MSR_SE
;
372 regs
->msr
|= kcb
->kprobe_saved_msr
;
374 reset_current_kprobe();
375 preempt_enable_no_resched();
381 * Wrapper routine to for handling exceptions.
383 int __kprobes
kprobe_exceptions_notify(struct notifier_block
*self
,
384 unsigned long val
, void *data
)
386 struct die_args
*args
= (struct die_args
*)data
;
387 int ret
= NOTIFY_DONE
;
391 if (kprobe_handler(args
->regs
))
395 if (post_kprobe_handler(args
->regs
))
399 /* kprobe_running() needs smp_processor_id() */
401 if (kprobe_running() &&
402 kprobe_fault_handler(args
->regs
, args
->trapnr
))
412 int __kprobes
setjmp_pre_handler(struct kprobe
*p
, struct pt_regs
*regs
)
414 struct jprobe
*jp
= container_of(p
, struct jprobe
, kp
);
415 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
417 memcpy(&kcb
->jprobe_saved_regs
, regs
, sizeof(struct pt_regs
));
419 /* setup return addr to the jprobe handler routine */
420 regs
->nip
= (unsigned long)(((func_descr_t
*)jp
->entry
)->entry
);
421 regs
->gpr
[2] = (unsigned long)(((func_descr_t
*)jp
->entry
)->toc
);
426 void __kprobes
jprobe_return(void)
428 asm volatile("trap" ::: "memory");
431 void __kprobes
jprobe_return_end(void)
435 int __kprobes
longjmp_break_handler(struct kprobe
*p
, struct pt_regs
*regs
)
437 struct kprobe_ctlblk
*kcb
= get_kprobe_ctlblk();
440 * FIXME - we should ideally be validating that we got here 'cos
441 * of the "trap" in jprobe_return() above, before restoring the
444 memcpy(regs
, &kcb
->jprobe_saved_regs
, sizeof(struct pt_regs
));
445 preempt_enable_no_resched();
449 static struct kprobe trampoline_p
= {
450 .addr
= (kprobe_opcode_t
*) &kretprobe_trampoline
,
451 .pre_handler
= trampoline_probe_handler
454 int __init
arch_init_kprobes(void)
456 return register_kprobe(&trampoline_p
);