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/extable.h>
33 #include <linux/kdebug.h>
34 #include <linux/slab.h>
35 #include <asm/code-patching.h>
36 #include <asm/cacheflush.h>
37 #include <asm/sstep.h>
38 #include <asm/uaccess.h>
40 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
41 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
43 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
45 int __kprobes arch_prepare_kprobe(struct kprobe *p)
48 kprobe_opcode_t insn = *p->addr;
50 if ((unsigned long)p->addr & 0x03) {
51 printk("Attempt to register kprobe at an unaligned address\n");
53 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
54 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
58 /* insn must be on a special executable page on ppc64. This is
59 * not explicitly required on ppc32 (right now), but it doesn't hurt */
61 p->ainsn.insn = get_insn_slot();
67 memcpy(p->ainsn.insn, p->addr,
68 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
70 flush_icache_range((unsigned long)p->ainsn.insn,
71 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
74 p->ainsn.boostable = 0;
78 void __kprobes arch_arm_kprobe(struct kprobe *p)
80 *p->addr = BREAKPOINT_INSTRUCTION;
81 flush_icache_range((unsigned long) p->addr,
82 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
85 void __kprobes arch_disarm_kprobe(struct kprobe *p)
88 flush_icache_range((unsigned long) p->addr,
89 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
92 void __kprobes arch_remove_kprobe(struct kprobe *p)
95 free_insn_slot(p->ainsn.insn, 0);
100 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
102 enable_single_step(regs);
105 * On powerpc we should single step on the original
106 * instruction even if the probed insn is a trap
107 * variant as values in regs could play a part in
108 * if the trap is taken or not
110 regs->nip = (unsigned long)p->ainsn.insn;
113 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
115 kcb->prev_kprobe.kp = kprobe_running();
116 kcb->prev_kprobe.status = kcb->kprobe_status;
117 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
120 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
122 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
123 kcb->kprobe_status = kcb->prev_kprobe.status;
124 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
127 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
128 struct kprobe_ctlblk *kcb)
130 __this_cpu_write(current_kprobe, p);
131 kcb->kprobe_saved_msr = regs->msr;
134 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
135 struct pt_regs *regs)
137 ri->ret_addr = (kprobe_opcode_t *)regs->link;
139 /* Replace the return addr with trampoline addr */
140 regs->link = (unsigned long)kretprobe_trampoline;
143 int __kprobes kprobe_handler(struct pt_regs *regs)
147 unsigned int *addr = (unsigned int *)regs->nip;
148 struct kprobe_ctlblk *kcb;
154 * We don't want to be preempted for the entire
155 * duration of kprobe processing
158 kcb = get_kprobe_ctlblk();
160 /* Check we're not actually recursing */
161 if (kprobe_running()) {
162 p = get_kprobe(addr);
164 kprobe_opcode_t insn = *p->ainsn.insn;
165 if (kcb->kprobe_status == KPROBE_HIT_SS &&
167 /* Turn off 'trace' bits */
168 regs->msr &= ~MSR_SINGLESTEP;
169 regs->msr |= kcb->kprobe_saved_msr;
172 /* We have reentered the kprobe_handler(), since
173 * another probe was hit while within the handler.
174 * We here save the original kprobes variables and
175 * just single step on the instruction of the new probe
176 * without calling any user handlers.
178 save_previous_kprobe(kcb);
179 set_current_kprobe(p, regs, kcb);
180 kcb->kprobe_saved_msr = regs->msr;
181 kprobes_inc_nmissed_count(p);
182 prepare_singlestep(p, regs);
183 kcb->kprobe_status = KPROBE_REENTER;
186 if (*addr != BREAKPOINT_INSTRUCTION) {
187 /* If trap variant, then it belongs not to us */
188 kprobe_opcode_t cur_insn = *addr;
189 if (is_trap(cur_insn))
191 /* The breakpoint instruction was removed by
192 * another cpu right after we hit, no further
193 * handling of this interrupt is appropriate
198 p = __this_cpu_read(current_kprobe);
199 if (p->break_handler && p->break_handler(p, regs)) {
206 p = get_kprobe(addr);
208 if (*addr != BREAKPOINT_INSTRUCTION) {
210 * PowerPC has multiple variants of the "trap"
211 * instruction. If the current instruction is a
212 * trap variant, it could belong to someone else
214 kprobe_opcode_t cur_insn = *addr;
215 if (is_trap(cur_insn))
218 * The breakpoint instruction was removed right
219 * after we hit it. Another cpu has removed
220 * either a probepoint or a debugger breakpoint
221 * at this address. In either case, no further
222 * handling of this interrupt is appropriate.
226 /* Not one of ours: let kernel handle it */
230 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
231 set_current_kprobe(p, regs, kcb);
232 if (p->pre_handler && p->pre_handler(p, regs))
233 /* handler has already set things up, so skip ss setup */
237 if (p->ainsn.boostable >= 0) {
238 unsigned int insn = *p->ainsn.insn;
240 /* regs->nip is also adjusted if emulate_step returns 1 */
241 ret = emulate_step(regs, insn);
244 * Once this instruction has been boosted
245 * successfully, set the boostable flag
247 if (unlikely(p->ainsn.boostable == 0))
248 p->ainsn.boostable = 1;
251 p->post_handler(p, regs, 0);
253 kcb->kprobe_status = KPROBE_HIT_SSDONE;
254 reset_current_kprobe();
255 preempt_enable_no_resched();
257 } else if (ret < 0) {
259 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
260 * So, we should never get here... but, its still
261 * good to catch them, just in case...
263 printk("Can't step on instruction %x\n", insn);
266 /* This instruction can't be boosted */
267 p->ainsn.boostable = -1;
269 prepare_singlestep(p, regs);
270 kcb->kprobe_status = KPROBE_HIT_SS;
274 preempt_enable_no_resched();
279 * Function return probe trampoline:
280 * - init_kprobes() establishes a probepoint here
281 * - When the probed function returns, this probe
282 * causes the handlers to fire
284 asm(".global kretprobe_trampoline\n"
285 ".type kretprobe_trampoline, @function\n"
286 "kretprobe_trampoline:\n"
288 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
291 * Called when the probe at kretprobe trampoline is hit
293 static int __kprobes trampoline_probe_handler(struct kprobe *p,
294 struct pt_regs *regs)
296 struct kretprobe_instance *ri = NULL;
297 struct hlist_head *head, empty_rp;
298 struct hlist_node *tmp;
299 unsigned long flags, orig_ret_address = 0;
300 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
302 INIT_HLIST_HEAD(&empty_rp);
303 kretprobe_hash_lock(current, &head, &flags);
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 than 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, 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 kretprobe_hash_unlock(current, &flags);
343 preempt_enable_no_resched();
345 hlist_for_each_entry_safe(ri, 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 int __kprobes kprobe_post_handler(struct pt_regs *regs)
367 struct kprobe *cur = kprobe_running();
368 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
370 if (!cur || user_mode(regs))
373 /* make sure we got here for instruction we have a kprobe on */
374 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
377 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
378 kcb->kprobe_status = KPROBE_HIT_SSDONE;
379 cur->post_handler(cur, regs, 0);
382 /* Adjust nip to after the single-stepped instruction */
383 regs->nip = (unsigned long)cur->addr + 4;
384 regs->msr |= kcb->kprobe_saved_msr;
386 /*Restore back the original saved kprobes variables and continue. */
387 if (kcb->kprobe_status == KPROBE_REENTER) {
388 restore_previous_kprobe(kcb);
391 reset_current_kprobe();
393 preempt_enable_no_resched();
396 * if somebody else is singlestepping across a probe point, msr
397 * will have DE/SE set, in which case, continue the remaining processing
398 * of do_debug, as if this is not a probe hit.
400 if (regs->msr & MSR_SINGLESTEP)
406 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
408 struct kprobe *cur = kprobe_running();
409 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
410 const struct exception_table_entry *entry;
412 switch(kcb->kprobe_status) {
416 * We are here because the instruction being single
417 * stepped caused a page fault. We reset the current
418 * kprobe and the nip points back to the probe address
419 * and allow the page fault handler to continue as a
422 regs->nip = (unsigned long)cur->addr;
423 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
424 regs->msr |= kcb->kprobe_saved_msr;
425 if (kcb->kprobe_status == KPROBE_REENTER)
426 restore_previous_kprobe(kcb);
428 reset_current_kprobe();
429 preempt_enable_no_resched();
431 case KPROBE_HIT_ACTIVE:
432 case KPROBE_HIT_SSDONE:
434 * We increment the nmissed count for accounting,
435 * we can also use npre/npostfault count for accounting
436 * these specific fault cases.
438 kprobes_inc_nmissed_count(cur);
441 * We come here because instructions in the pre/post
442 * handler caused the page_fault, this could happen
443 * if handler tries to access user space by
444 * copy_from_user(), get_user() etc. Let the
445 * user-specified handler try to fix it first.
447 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
451 * In case the user-specified fault handler returned
452 * zero, try to fix up.
454 if ((entry = search_exception_tables(regs->nip)) != NULL) {
455 regs->nip = extable_fixup(entry);
460 * fixup_exception() could not handle it,
461 * Let do_page_fault() fix it.
471 * Wrapper routine to for handling exceptions.
473 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
474 unsigned long val, void *data)
479 unsigned long arch_deref_entry_point(void *entry)
481 return ppc_global_function_entry(entry);
484 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
486 struct jprobe *jp = container_of(p, struct jprobe, kp);
487 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
489 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
491 /* setup return addr to the jprobe handler routine */
492 regs->nip = arch_deref_entry_point(jp->entry);
493 #ifdef PPC64_ELF_ABI_v2
494 regs->gpr[12] = (unsigned long)jp->entry;
495 #elif defined(PPC64_ELF_ABI_v1)
496 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
502 void __used __kprobes jprobe_return(void)
504 asm volatile("trap" ::: "memory");
507 static void __used __kprobes jprobe_return_end(void)
511 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
513 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
516 * FIXME - we should ideally be validating that we got here 'cos
517 * of the "trap" in jprobe_return() above, before restoring the
520 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
521 preempt_enable_no_resched();
525 static struct kprobe trampoline_p = {
526 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
527 .pre_handler = trampoline_probe_handler
530 int __init arch_init_kprobes(void)
532 return register_kprobe(&trampoline_p);
535 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
537 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)