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/module.h>
33 #include <linux/kdebug.h>
34 #include <asm/cacheflush.h>
35 #include <asm/sstep.h>
36 #include <asm/uaccess.h>
38 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
39 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
41 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
43 int __kprobes arch_prepare_kprobe(struct kprobe *p)
46 kprobe_opcode_t insn = *p->addr;
48 if ((unsigned long)p->addr & 0x03) {
49 printk("Attempt to register kprobe at an unaligned address\n");
51 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
52 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
56 /* insn must be on a special executable page on ppc64 */
58 p->ainsn.insn = get_insn_slot();
64 memcpy(p->ainsn.insn, p->addr,
65 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
67 flush_icache_range((unsigned long)p->ainsn.insn,
68 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
71 p->ainsn.boostable = 0;
75 void __kprobes arch_arm_kprobe(struct kprobe *p)
77 *p->addr = BREAKPOINT_INSTRUCTION;
78 flush_icache_range((unsigned long) p->addr,
79 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
82 void __kprobes arch_disarm_kprobe(struct kprobe *p)
85 flush_icache_range((unsigned long) p->addr,
86 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
89 void __kprobes arch_remove_kprobe(struct kprobe *p)
91 mutex_lock(&kprobe_mutex);
92 free_insn_slot(p->ainsn.insn, 0);
93 mutex_unlock(&kprobe_mutex);
96 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
98 /* We turn off async exceptions to ensure that the single step will
99 * be for the instruction we have the kprobe on, if we dont its
100 * possible we'd get the single step reported for an exception handler
101 * like Decrementer or External Interrupt */
102 regs->msr &= ~MSR_EE;
106 * On powerpc we should single step on the original
107 * instruction even if the probed insn is a trap
108 * variant as values in regs could play a part in
109 * if the trap is taken or not
111 regs->nip = (unsigned long)p->ainsn.insn;
114 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
116 kcb->prev_kprobe.kp = kprobe_running();
117 kcb->prev_kprobe.status = kcb->kprobe_status;
118 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
121 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
123 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
124 kcb->kprobe_status = kcb->prev_kprobe.status;
125 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
128 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
129 struct kprobe_ctlblk *kcb)
131 __get_cpu_var(current_kprobe) = p;
132 kcb->kprobe_saved_msr = regs->msr;
135 /* Called with kretprobe_lock held */
136 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
137 struct pt_regs *regs)
139 ri->ret_addr = (kprobe_opcode_t *)regs->link;
141 /* Replace the return addr with trampoline addr */
142 regs->link = (unsigned long)kretprobe_trampoline;
145 static int __kprobes kprobe_handler(struct pt_regs *regs)
149 unsigned int *addr = (unsigned int *)regs->nip;
150 struct kprobe_ctlblk *kcb;
153 * We don't want to be preempted for the entire
154 * duration of kprobe processing
157 kcb = get_kprobe_ctlblk();
159 /* Check we're not actually recursing */
160 if (kprobe_running()) {
161 p = get_kprobe(addr);
163 kprobe_opcode_t insn = *p->ainsn.insn;
164 if (kcb->kprobe_status == KPROBE_HIT_SS &&
166 regs->msr &= ~MSR_SE;
167 regs->msr |= kcb->kprobe_saved_msr;
170 /* We have reentered the kprobe_handler(), since
171 * another probe was hit while within the handler.
172 * We here save the original kprobes variables and
173 * just single step on the instruction of the new probe
174 * without calling any user handlers.
176 save_previous_kprobe(kcb);
177 set_current_kprobe(p, regs, kcb);
178 kcb->kprobe_saved_msr = regs->msr;
179 kprobes_inc_nmissed_count(p);
180 prepare_singlestep(p, regs);
181 kcb->kprobe_status = KPROBE_REENTER;
184 if (*addr != BREAKPOINT_INSTRUCTION) {
185 /* If trap variant, then it belongs not to us */
186 kprobe_opcode_t cur_insn = *addr;
187 if (is_trap(cur_insn))
189 /* The breakpoint instruction was removed by
190 * another cpu right after we hit, no further
191 * handling of this interrupt is appropriate
196 p = __get_cpu_var(current_kprobe);
197 if (p->break_handler && p->break_handler(p, regs)) {
204 p = get_kprobe(addr);
206 if (*addr != BREAKPOINT_INSTRUCTION) {
208 * PowerPC has multiple variants of the "trap"
209 * instruction. If the current instruction is a
210 * trap variant, it could belong to someone else
212 kprobe_opcode_t cur_insn = *addr;
213 if (is_trap(cur_insn))
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.
224 /* Not one of ours: let kernel handle it */
228 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
229 set_current_kprobe(p, regs, kcb);
230 if (p->pre_handler && p->pre_handler(p, regs))
231 /* handler has already set things up, so skip ss setup */
235 if (p->ainsn.boostable >= 0) {
236 unsigned int insn = *p->ainsn.insn;
238 /* regs->nip is also adjusted if emulate_step returns 1 */
239 ret = emulate_step(regs, insn);
242 * Once this instruction has been boosted
243 * successfully, set the boostable flag
245 if (unlikely(p->ainsn.boostable == 0))
246 p->ainsn.boostable = 1;
249 p->post_handler(p, regs, 0);
251 kcb->kprobe_status = KPROBE_HIT_SSDONE;
252 reset_current_kprobe();
253 preempt_enable_no_resched();
255 } else if (ret < 0) {
257 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
258 * So, we should never get here... but, its still
259 * good to catch them, just in case...
261 printk("Can't step on instruction %x\n", insn);
264 /* This instruction can't be boosted */
265 p->ainsn.boostable = -1;
267 prepare_singlestep(p, regs);
268 kcb->kprobe_status = KPROBE_HIT_SS;
272 preempt_enable_no_resched();
277 * Function return probe trampoline:
278 * - init_kprobes() establishes a probepoint here
279 * - When the probed function returns, this probe
280 * causes the handlers to fire
282 static void __used kretprobe_trampoline_holder(void)
284 asm volatile(".global kretprobe_trampoline\n"
285 "kretprobe_trampoline:\n"
290 * Called when the probe at kretprobe trampoline is hit
292 static int __kprobes trampoline_probe_handler(struct kprobe *p,
293 struct pt_regs *regs)
295 struct kretprobe_instance *ri = NULL;
296 struct hlist_head *head, empty_rp;
297 struct hlist_node *node, *tmp;
298 unsigned long flags, orig_ret_address = 0;
299 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
301 INIT_HLIST_HEAD(&empty_rp);
302 spin_lock_irqsave(&kretprobe_lock, flags);
303 head = kretprobe_inst_table_head(current);
306 * It is possible to have multiple instances associated with a given
307 * task either because an multiple functions in the call path
308 * have a return probe installed on them, and/or more then one return
309 * return probe was registered for a target function.
311 * We can handle this because:
312 * - instances are always inserted at the head of the list
313 * - when multiple return probes are registered for the same
314 * function, the first instance's ret_addr will point to the
315 * real return address, and all the rest will point to
316 * kretprobe_trampoline
318 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
319 if (ri->task != current)
320 /* another task is sharing our hash bucket */
323 if (ri->rp && ri->rp->handler)
324 ri->rp->handler(ri, regs);
326 orig_ret_address = (unsigned long)ri->ret_addr;
327 recycle_rp_inst(ri, &empty_rp);
329 if (orig_ret_address != trampoline_address)
331 * This is the real return address. Any other
332 * instances associated with this task are for
333 * other calls deeper on the call stack
338 kretprobe_assert(ri, orig_ret_address, trampoline_address);
339 regs->nip = orig_ret_address;
341 reset_current_kprobe();
342 spin_unlock_irqrestore(&kretprobe_lock, flags);
343 preempt_enable_no_resched();
345 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
346 hlist_del(&ri->hlist);
350 * By returning a non-zero value, we are telling
351 * kprobe_handler() that we don't want the post_handler
352 * to run (and have re-enabled preemption)
358 * Called after single-stepping. p->addr is the address of the
359 * instruction whose first byte has been replaced by the "breakpoint"
360 * instruction. To avoid the SMP problems that can occur when we
361 * temporarily put back the original opcode to single-step, we
362 * single-stepped a copy of the instruction. The address of this
363 * copy is p->ainsn.insn.
365 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
368 unsigned int insn = *p->ainsn.insn;
370 regs->nip = (unsigned long)p->addr;
371 ret = emulate_step(regs, insn);
373 regs->nip = (unsigned long)p->addr + 4;
376 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
378 struct kprobe *cur = kprobe_running();
379 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
384 /* make sure we got here for instruction we have a kprobe on */
385 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
388 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
389 kcb->kprobe_status = KPROBE_HIT_SSDONE;
390 cur->post_handler(cur, regs, 0);
393 resume_execution(cur, regs);
394 regs->msr |= kcb->kprobe_saved_msr;
396 /*Restore back the original saved kprobes variables and continue. */
397 if (kcb->kprobe_status == KPROBE_REENTER) {
398 restore_previous_kprobe(kcb);
401 reset_current_kprobe();
403 preempt_enable_no_resched();
406 * if somebody else is singlestepping across a probe point, msr
407 * will have SE set, in which case, continue the remaining processing
408 * of do_debug, as if this is not a probe hit.
410 if (regs->msr & MSR_SE)
416 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
418 struct kprobe *cur = kprobe_running();
419 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
420 const struct exception_table_entry *entry;
422 switch(kcb->kprobe_status) {
426 * We are here because the instruction being single
427 * stepped caused a page fault. We reset the current
428 * kprobe and the nip points back to the probe address
429 * and allow the page fault handler to continue as a
432 regs->nip = (unsigned long)cur->addr;
433 regs->msr &= ~MSR_SE;
434 regs->msr |= kcb->kprobe_saved_msr;
435 if (kcb->kprobe_status == KPROBE_REENTER)
436 restore_previous_kprobe(kcb);
438 reset_current_kprobe();
439 preempt_enable_no_resched();
441 case KPROBE_HIT_ACTIVE:
442 case KPROBE_HIT_SSDONE:
444 * We increment the nmissed count for accounting,
445 * we can also use npre/npostfault count for accouting
446 * these specific fault cases.
448 kprobes_inc_nmissed_count(cur);
451 * We come here because instructions in the pre/post
452 * handler caused the page_fault, this could happen
453 * if handler tries to access user space by
454 * copy_from_user(), get_user() etc. Let the
455 * user-specified handler try to fix it first.
457 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
461 * In case the user-specified fault handler returned
462 * zero, try to fix up.
464 if ((entry = search_exception_tables(regs->nip)) != NULL) {
465 regs->nip = entry->fixup;
470 * fixup_exception() could not handle it,
471 * Let do_page_fault() fix it.
481 * Wrapper routine to for handling exceptions.
483 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
484 unsigned long val, void *data)
486 struct die_args *args = (struct die_args *)data;
487 int ret = NOTIFY_DONE;
489 if (args->regs && user_mode(args->regs))
494 if (kprobe_handler(args->regs))
498 if (post_kprobe_handler(args->regs))
508 unsigned long arch_deref_entry_point(void *entry)
510 return ((func_descr_t *)entry)->entry;
514 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
516 struct jprobe *jp = container_of(p, struct jprobe, kp);
517 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
519 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
521 /* setup return addr to the jprobe handler routine */
522 regs->nip = arch_deref_entry_point(jp->entry);
524 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
530 void __used __kprobes jprobe_return(void)
532 asm volatile("trap" ::: "memory");
535 static void __used __kprobes jprobe_return_end(void)
539 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
541 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
544 * FIXME - we should ideally be validating that we got here 'cos
545 * of the "trap" in jprobe_return() above, before restoring the
548 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
549 preempt_enable_no_resched();
553 static struct kprobe trampoline_p = {
554 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
555 .pre_handler = trampoline_probe_handler
558 int __init arch_init_kprobes(void)
560 return register_kprobe(&trampoline_p);
563 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
565 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)