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 <linux/slab.h>
35 #include <asm/cacheflush.h>
36 #include <asm/sstep.h>
37 #include <asm/uaccess.h>
39 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
40 #define MSR_SINGLESTEP (MSR_DE)
42 #define MSR_SINGLESTEP (MSR_SE)
45 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
46 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
48 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
50 int __kprobes arch_prepare_kprobe(struct kprobe *p)
53 kprobe_opcode_t insn = *p->addr;
55 if ((unsigned long)p->addr & 0x03) {
56 printk("Attempt to register kprobe at an unaligned address\n");
58 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
59 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
63 /* insn must be on a special executable page on ppc64. This is
64 * not explicitly required on ppc32 (right now), but it doesn't hurt */
66 p->ainsn.insn = get_insn_slot();
72 memcpy(p->ainsn.insn, p->addr,
73 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
75 flush_icache_range((unsigned long)p->ainsn.insn,
76 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
79 p->ainsn.boostable = 0;
83 void __kprobes arch_arm_kprobe(struct kprobe *p)
85 *p->addr = BREAKPOINT_INSTRUCTION;
86 flush_icache_range((unsigned long) p->addr,
87 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
90 void __kprobes arch_disarm_kprobe(struct kprobe *p)
93 flush_icache_range((unsigned long) p->addr,
94 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
97 void __kprobes arch_remove_kprobe(struct kprobe *p)
100 free_insn_slot(p->ainsn.insn, 0);
101 p->ainsn.insn = NULL;
105 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
107 /* We turn off async exceptions to ensure that the single step will
108 * be for the instruction we have the kprobe on, if we dont its
109 * possible we'd get the single step reported for an exception handler
110 * like Decrementer or External Interrupt */
111 regs->msr &= ~MSR_EE;
112 regs->msr |= MSR_SINGLESTEP;
113 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
114 regs->msr &= ~MSR_CE;
115 mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
116 #ifdef CONFIG_PPC_47x
122 * On powerpc we should single step on the original
123 * instruction even if the probed insn is a trap
124 * variant as values in regs could play a part in
125 * if the trap is taken or not
127 regs->nip = (unsigned long)p->ainsn.insn;
130 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
132 kcb->prev_kprobe.kp = kprobe_running();
133 kcb->prev_kprobe.status = kcb->kprobe_status;
134 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
137 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
139 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
140 kcb->kprobe_status = kcb->prev_kprobe.status;
141 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
144 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
145 struct kprobe_ctlblk *kcb)
147 __get_cpu_var(current_kprobe) = p;
148 kcb->kprobe_saved_msr = regs->msr;
151 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
152 struct pt_regs *regs)
154 ri->ret_addr = (kprobe_opcode_t *)regs->link;
156 /* Replace the return addr with trampoline addr */
157 regs->link = (unsigned long)kretprobe_trampoline;
160 static int __kprobes kprobe_handler(struct pt_regs *regs)
164 unsigned int *addr = (unsigned int *)regs->nip;
165 struct kprobe_ctlblk *kcb;
168 * We don't want to be preempted for the entire
169 * duration of kprobe processing
172 kcb = get_kprobe_ctlblk();
174 /* Check we're not actually recursing */
175 if (kprobe_running()) {
176 p = get_kprobe(addr);
178 kprobe_opcode_t insn = *p->ainsn.insn;
179 if (kcb->kprobe_status == KPROBE_HIT_SS &&
181 /* Turn off 'trace' bits */
182 regs->msr &= ~MSR_SINGLESTEP;
183 regs->msr |= kcb->kprobe_saved_msr;
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);
194 kcb->kprobe_saved_msr = regs->msr;
195 kprobes_inc_nmissed_count(p);
196 prepare_singlestep(p, regs);
197 kcb->kprobe_status = KPROBE_REENTER;
200 if (*addr != BREAKPOINT_INSTRUCTION) {
201 /* If trap variant, then it belongs not to us */
202 kprobe_opcode_t cur_insn = *addr;
203 if (is_trap(cur_insn))
205 /* The breakpoint instruction was removed by
206 * another cpu right after we hit, no further
207 * handling of this interrupt is appropriate
212 p = __get_cpu_var(current_kprobe);
213 if (p->break_handler && p->break_handler(p, regs)) {
220 p = get_kprobe(addr);
222 if (*addr != BREAKPOINT_INSTRUCTION) {
224 * PowerPC has multiple variants of the "trap"
225 * instruction. If the current instruction is a
226 * trap variant, it could belong to someone else
228 kprobe_opcode_t cur_insn = *addr;
229 if (is_trap(cur_insn))
232 * The breakpoint instruction was removed right
233 * after we hit it. Another cpu has removed
234 * either a probepoint or a debugger breakpoint
235 * at this address. In either case, no further
236 * handling of this interrupt is appropriate.
240 /* Not one of ours: let kernel handle it */
244 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
245 set_current_kprobe(p, regs, kcb);
246 if (p->pre_handler && p->pre_handler(p, regs))
247 /* handler has already set things up, so skip ss setup */
251 if (p->ainsn.boostable >= 0) {
252 unsigned int insn = *p->ainsn.insn;
254 /* regs->nip is also adjusted if emulate_step returns 1 */
255 ret = emulate_step(regs, insn);
258 * Once this instruction has been boosted
259 * successfully, set the boostable flag
261 if (unlikely(p->ainsn.boostable == 0))
262 p->ainsn.boostable = 1;
265 p->post_handler(p, regs, 0);
267 kcb->kprobe_status = KPROBE_HIT_SSDONE;
268 reset_current_kprobe();
269 preempt_enable_no_resched();
271 } else if (ret < 0) {
273 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
274 * So, we should never get here... but, its still
275 * good to catch them, just in case...
277 printk("Can't step on instruction %x\n", insn);
280 /* This instruction can't be boosted */
281 p->ainsn.boostable = -1;
283 prepare_singlestep(p, regs);
284 kcb->kprobe_status = KPROBE_HIT_SS;
288 preempt_enable_no_resched();
293 * Function return probe trampoline:
294 * - init_kprobes() establishes a probepoint here
295 * - When the probed function returns, this probe
296 * causes the handlers to fire
298 static void __used kretprobe_trampoline_holder(void)
300 asm volatile(".global kretprobe_trampoline\n"
301 "kretprobe_trampoline:\n"
306 * Called when the probe at kretprobe trampoline is hit
308 static int __kprobes trampoline_probe_handler(struct kprobe *p,
309 struct pt_regs *regs)
311 struct kretprobe_instance *ri = NULL;
312 struct hlist_head *head, empty_rp;
313 struct hlist_node *node, *tmp;
314 unsigned long flags, orig_ret_address = 0;
315 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
317 INIT_HLIST_HEAD(&empty_rp);
318 kretprobe_hash_lock(current, &head, &flags);
321 * It is possible to have multiple instances associated with a given
322 * task either because an multiple functions in the call path
323 * have a return probe installed on them, and/or more than one return
324 * return probe was registered for a target function.
326 * We can handle this because:
327 * - instances are always inserted at the head of the list
328 * - when multiple return probes are registered for the same
329 * function, the first instance's ret_addr will point to the
330 * real return address, and all the rest will point to
331 * kretprobe_trampoline
333 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
334 if (ri->task != current)
335 /* another task is sharing our hash bucket */
338 if (ri->rp && ri->rp->handler)
339 ri->rp->handler(ri, regs);
341 orig_ret_address = (unsigned long)ri->ret_addr;
342 recycle_rp_inst(ri, &empty_rp);
344 if (orig_ret_address != trampoline_address)
346 * This is the real return address. Any other
347 * instances associated with this task are for
348 * other calls deeper on the call stack
353 kretprobe_assert(ri, orig_ret_address, trampoline_address);
354 regs->nip = orig_ret_address;
356 reset_current_kprobe();
357 kretprobe_hash_unlock(current, &flags);
358 preempt_enable_no_resched();
360 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
361 hlist_del(&ri->hlist);
365 * By returning a non-zero value, we are telling
366 * kprobe_handler() that we don't want the post_handler
367 * to run (and have re-enabled preemption)
373 * Called after single-stepping. p->addr is the address of the
374 * instruction whose first byte has been replaced by the "breakpoint"
375 * instruction. To avoid the SMP problems that can occur when we
376 * temporarily put back the original opcode to single-step, we
377 * single-stepped a copy of the instruction. The address of this
378 * copy is p->ainsn.insn.
380 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
382 struct kprobe *cur = kprobe_running();
383 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
388 /* make sure we got here for instruction we have a kprobe on */
389 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
392 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
393 kcb->kprobe_status = KPROBE_HIT_SSDONE;
394 cur->post_handler(cur, regs, 0);
397 /* Adjust nip to after the single-stepped instruction */
398 regs->nip = (unsigned long)cur->addr + 4;
399 regs->msr |= kcb->kprobe_saved_msr;
401 /*Restore back the original saved kprobes variables and continue. */
402 if (kcb->kprobe_status == KPROBE_REENTER) {
403 restore_previous_kprobe(kcb);
406 reset_current_kprobe();
408 preempt_enable_no_resched();
411 * if somebody else is singlestepping across a probe point, msr
412 * will have DE/SE set, in which case, continue the remaining processing
413 * of do_debug, as if this is not a probe hit.
415 if (regs->msr & MSR_SINGLESTEP)
421 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
423 struct kprobe *cur = kprobe_running();
424 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
425 const struct exception_table_entry *entry;
427 switch(kcb->kprobe_status) {
431 * We are here because the instruction being single
432 * stepped caused a page fault. We reset the current
433 * kprobe and the nip points back to the probe address
434 * and allow the page fault handler to continue as a
437 regs->nip = (unsigned long)cur->addr;
438 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
439 regs->msr |= kcb->kprobe_saved_msr;
440 if (kcb->kprobe_status == KPROBE_REENTER)
441 restore_previous_kprobe(kcb);
443 reset_current_kprobe();
444 preempt_enable_no_resched();
446 case KPROBE_HIT_ACTIVE:
447 case KPROBE_HIT_SSDONE:
449 * We increment the nmissed count for accounting,
450 * we can also use npre/npostfault count for accouting
451 * these specific fault cases.
453 kprobes_inc_nmissed_count(cur);
456 * We come here because instructions in the pre/post
457 * handler caused the page_fault, this could happen
458 * if handler tries to access user space by
459 * copy_from_user(), get_user() etc. Let the
460 * user-specified handler try to fix it first.
462 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
466 * In case the user-specified fault handler returned
467 * zero, try to fix up.
469 if ((entry = search_exception_tables(regs->nip)) != NULL) {
470 regs->nip = entry->fixup;
475 * fixup_exception() could not handle it,
476 * Let do_page_fault() fix it.
486 * Wrapper routine to for handling exceptions.
488 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
489 unsigned long val, void *data)
491 struct die_args *args = (struct die_args *)data;
492 int ret = NOTIFY_DONE;
494 if (args->regs && user_mode(args->regs))
499 if (kprobe_handler(args->regs))
503 if (post_kprobe_handler(args->regs))
513 unsigned long arch_deref_entry_point(void *entry)
515 return ((func_descr_t *)entry)->entry;
519 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
521 struct jprobe *jp = container_of(p, struct jprobe, kp);
522 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
524 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
526 /* setup return addr to the jprobe handler routine */
527 regs->nip = arch_deref_entry_point(jp->entry);
529 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
535 void __used __kprobes jprobe_return(void)
537 asm volatile("trap" ::: "memory");
540 static void __used __kprobes jprobe_return_end(void)
544 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
546 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
549 * FIXME - we should ideally be validating that we got here 'cos
550 * of the "trap" in jprobe_return() above, before restoring the
553 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
554 preempt_enable_no_resched();
558 static struct kprobe trampoline_p = {
559 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
560 .pre_handler = trampoline_probe_handler
563 int __init arch_init_kprobes(void)
565 return register_kprobe(&trampoline_p);
568 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
570 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)