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1/*
2 * Kernel Probes (KProbes)
3 *
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.
8 *
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.
13 *
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.
17 *
18 * Copyright (C) IBM Corporation, 2002, 2004
19 *
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
22 * Rusty Russell).
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
26 * for PPC64
27 */
28
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/sections.h>
39#include <linux/uaccess.h>
40
41DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
42DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
43
44struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
45
46bool arch_within_kprobe_blacklist(unsigned long addr)
47{
48 return (addr >= (unsigned long)__kprobes_text_start &&
49 addr < (unsigned long)__kprobes_text_end) ||
50 (addr >= (unsigned long)_stext &&
51 addr < (unsigned long)__head_end);
52}
53
54kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
55{
56 kprobe_opcode_t *addr = NULL;
57
58#ifdef PPC64_ELF_ABI_v2
59 /* PPC64 ABIv2 needs local entry point */
60 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
61 if (addr && !offset) {
62#ifdef CONFIG_KPROBES_ON_FTRACE
63 unsigned long faddr;
64 /*
65 * Per livepatch.h, ftrace location is always within the first
66 * 16 bytes of a function on powerpc with -mprofile-kernel.
67 */
68 faddr = ftrace_location_range((unsigned long)addr,
69 (unsigned long)addr + 16);
70 if (faddr)
71 addr = (kprobe_opcode_t *)faddr;
72 else
73#endif
74 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
75 }
76#elif defined(PPC64_ELF_ABI_v1)
77 /*
78 * 64bit powerpc ABIv1 uses function descriptors:
79 * - Check for the dot variant of the symbol first.
80 * - If that fails, try looking up the symbol provided.
81 *
82 * This ensures we always get to the actual symbol and not
83 * the descriptor.
84 *
85 * Also handle <module:symbol> format.
86 */
87 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
88 bool dot_appended = false;
89 const char *c;
90 ssize_t ret = 0;
91 int len = 0;
92
93 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
94 c++;
95 len = c - name;
96 memcpy(dot_name, name, len);
97 } else
98 c = name;
99
100 if (*c != '\0' && *c != '.') {
101 dot_name[len++] = '.';
102 dot_appended = true;
103 }
104 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
105 if (ret > 0)
106 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
107
108 /* Fallback to the original non-dot symbol lookup */
109 if (!addr && dot_appended)
110 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
111#else
112 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
113#endif
114
115 return addr;
116}
117
118int arch_prepare_kprobe(struct kprobe *p)
119{
120 int ret = 0;
121 kprobe_opcode_t insn = *p->addr;
122
123 if ((unsigned long)p->addr & 0x03) {
124 printk("Attempt to register kprobe at an unaligned address\n");
125 ret = -EINVAL;
126 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
127 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
128 ret = -EINVAL;
129 }
130
131 /* insn must be on a special executable page on ppc64. This is
132 * not explicitly required on ppc32 (right now), but it doesn't hurt */
133 if (!ret) {
134 p->ainsn.insn = get_insn_slot();
135 if (!p->ainsn.insn)
136 ret = -ENOMEM;
137 }
138
139 if (!ret) {
140 memcpy(p->ainsn.insn, p->addr,
141 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
142 p->opcode = *p->addr;
143 flush_icache_range((unsigned long)p->ainsn.insn,
144 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
145 }
146
147 p->ainsn.boostable = 0;
148 return ret;
149}
150NOKPROBE_SYMBOL(arch_prepare_kprobe);
151
152void arch_arm_kprobe(struct kprobe *p)
153{
154 patch_instruction(p->addr, BREAKPOINT_INSTRUCTION);
155}
156NOKPROBE_SYMBOL(arch_arm_kprobe);
157
158void arch_disarm_kprobe(struct kprobe *p)
159{
160 patch_instruction(p->addr, p->opcode);
161}
162NOKPROBE_SYMBOL(arch_disarm_kprobe);
163
164void arch_remove_kprobe(struct kprobe *p)
165{
166 if (p->ainsn.insn) {
167 free_insn_slot(p->ainsn.insn, 0);
168 p->ainsn.insn = NULL;
169 }
170}
171NOKPROBE_SYMBOL(arch_remove_kprobe);
172
173static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
174{
175 enable_single_step(regs);
176
177 /*
178 * On powerpc we should single step on the original
179 * instruction even if the probed insn is a trap
180 * variant as values in regs could play a part in
181 * if the trap is taken or not
182 */
183 regs->nip = (unsigned long)p->ainsn.insn;
184}
185
186static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
187{
188 kcb->prev_kprobe.kp = kprobe_running();
189 kcb->prev_kprobe.status = kcb->kprobe_status;
190 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
191}
192
193static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
194{
195 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
196 kcb->kprobe_status = kcb->prev_kprobe.status;
197 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
198}
199
200static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
201 struct kprobe_ctlblk *kcb)
202{
203 __this_cpu_write(current_kprobe, p);
204 kcb->kprobe_saved_msr = regs->msr;
205}
206
207bool arch_kprobe_on_func_entry(unsigned long offset)
208{
209#ifdef PPC64_ELF_ABI_v2
210#ifdef CONFIG_KPROBES_ON_FTRACE
211 return offset <= 16;
212#else
213 return offset <= 8;
214#endif
215#else
216 return !offset;
217#endif
218}
219
220void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
221{
222 ri->ret_addr = (kprobe_opcode_t *)regs->link;
223
224 /* Replace the return addr with trampoline addr */
225 regs->link = (unsigned long)kretprobe_trampoline;
226}
227NOKPROBE_SYMBOL(arch_prepare_kretprobe);
228
229static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
230{
231 int ret;
232 unsigned int insn = *p->ainsn.insn;
233
234 /* regs->nip is also adjusted if emulate_step returns 1 */
235 ret = emulate_step(regs, insn);
236 if (ret > 0) {
237 /*
238 * Once this instruction has been boosted
239 * successfully, set the boostable flag
240 */
241 if (unlikely(p->ainsn.boostable == 0))
242 p->ainsn.boostable = 1;
243 } else if (ret < 0) {
244 /*
245 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
246 * So, we should never get here... but, its still
247 * good to catch them, just in case...
248 */
249 printk("Can't step on instruction %x\n", insn);
250 BUG();
251 } else {
252 /*
253 * If we haven't previously emulated this instruction, then it
254 * can't be boosted. Note it down so we don't try to do so again.
255 *
256 * If, however, we had emulated this instruction in the past,
257 * then this is just an error with the current run (for
258 * instance, exceptions due to a load/store). We return 0 so
259 * that this is now single-stepped, but continue to try
260 * emulating it in subsequent probe hits.
261 */
262 if (unlikely(p->ainsn.boostable != 1))
263 p->ainsn.boostable = -1;
264 }
265
266 return ret;
267}
268NOKPROBE_SYMBOL(try_to_emulate);
269
270int kprobe_handler(struct pt_regs *regs)
271{
272 struct kprobe *p;
273 int ret = 0;
274 unsigned int *addr = (unsigned int *)regs->nip;
275 struct kprobe_ctlblk *kcb;
276
277 if (user_mode(regs))
278 return 0;
279
280 /*
281 * We don't want to be preempted for the entire
282 * duration of kprobe processing
283 */
284 preempt_disable();
285 kcb = get_kprobe_ctlblk();
286
287 /* Check we're not actually recursing */
288 if (kprobe_running()) {
289 p = get_kprobe(addr);
290 if (p) {
291 kprobe_opcode_t insn = *p->ainsn.insn;
292 if (kcb->kprobe_status == KPROBE_HIT_SS &&
293 is_trap(insn)) {
294 /* Turn off 'trace' bits */
295 regs->msr &= ~MSR_SINGLESTEP;
296 regs->msr |= kcb->kprobe_saved_msr;
297 goto no_kprobe;
298 }
299 /* We have reentered the kprobe_handler(), since
300 * another probe was hit while within the handler.
301 * We here save the original kprobes variables and
302 * just single step on the instruction of the new probe
303 * without calling any user handlers.
304 */
305 save_previous_kprobe(kcb);
306 set_current_kprobe(p, regs, kcb);
307 kprobes_inc_nmissed_count(p);
308 kcb->kprobe_status = KPROBE_REENTER;
309 if (p->ainsn.boostable >= 0) {
310 ret = try_to_emulate(p, regs);
311
312 if (ret > 0) {
313 restore_previous_kprobe(kcb);
314 preempt_enable_no_resched();
315 return 1;
316 }
317 }
318 prepare_singlestep(p, regs);
319 return 1;
320 } else {
321 if (*addr != BREAKPOINT_INSTRUCTION) {
322 /* If trap variant, then it belongs not to us */
323 kprobe_opcode_t cur_insn = *addr;
324 if (is_trap(cur_insn))
325 goto no_kprobe;
326 /* The breakpoint instruction was removed by
327 * another cpu right after we hit, no further
328 * handling of this interrupt is appropriate
329 */
330 ret = 1;
331 goto no_kprobe;
332 }
333 p = __this_cpu_read(current_kprobe);
334 if (p->break_handler && p->break_handler(p, regs)) {
335 if (!skip_singlestep(p, regs, kcb))
336 goto ss_probe;
337 ret = 1;
338 }
339 }
340 goto no_kprobe;
341 }
342
343 p = get_kprobe(addr);
344 if (!p) {
345 if (*addr != BREAKPOINT_INSTRUCTION) {
346 /*
347 * PowerPC has multiple variants of the "trap"
348 * instruction. If the current instruction is a
349 * trap variant, it could belong to someone else
350 */
351 kprobe_opcode_t cur_insn = *addr;
352 if (is_trap(cur_insn))
353 goto no_kprobe;
354 /*
355 * The breakpoint instruction was removed right
356 * after we hit it. Another cpu has removed
357 * either a probepoint or a debugger breakpoint
358 * at this address. In either case, no further
359 * handling of this interrupt is appropriate.
360 */
361 ret = 1;
362 }
363 /* Not one of ours: let kernel handle it */
364 goto no_kprobe;
365 }
366
367 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
368 set_current_kprobe(p, regs, kcb);
369 if (p->pre_handler && p->pre_handler(p, regs))
370 /* handler has already set things up, so skip ss setup */
371 return 1;
372
373ss_probe:
374 if (p->ainsn.boostable >= 0) {
375 ret = try_to_emulate(p, regs);
376
377 if (ret > 0) {
378 if (p->post_handler)
379 p->post_handler(p, regs, 0);
380
381 kcb->kprobe_status = KPROBE_HIT_SSDONE;
382 reset_current_kprobe();
383 preempt_enable_no_resched();
384 return 1;
385 }
386 }
387 prepare_singlestep(p, regs);
388 kcb->kprobe_status = KPROBE_HIT_SS;
389 return 1;
390
391no_kprobe:
392 preempt_enable_no_resched();
393 return ret;
394}
395NOKPROBE_SYMBOL(kprobe_handler);
396
397/*
398 * Function return probe trampoline:
399 * - init_kprobes() establishes a probepoint here
400 * - When the probed function returns, this probe
401 * causes the handlers to fire
402 */
403asm(".global kretprobe_trampoline\n"
404 ".type kretprobe_trampoline, @function\n"
405 "kretprobe_trampoline:\n"
406 "nop\n"
407 "blr\n"
408 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
409
410/*
411 * Called when the probe at kretprobe trampoline is hit
412 */
413static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
414{
415 struct kretprobe_instance *ri = NULL;
416 struct hlist_head *head, empty_rp;
417 struct hlist_node *tmp;
418 unsigned long flags, orig_ret_address = 0;
419 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
420
421 INIT_HLIST_HEAD(&empty_rp);
422 kretprobe_hash_lock(current, &head, &flags);
423
424 /*
425 * It is possible to have multiple instances associated with a given
426 * task either because an multiple functions in the call path
427 * have a return probe installed on them, and/or more than one return
428 * return probe was registered for a target function.
429 *
430 * We can handle this because:
431 * - instances are always inserted at the head of the list
432 * - when multiple return probes are registered for the same
433 * function, the first instance's ret_addr will point to the
434 * real return address, and all the rest will point to
435 * kretprobe_trampoline
436 */
437 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
438 if (ri->task != current)
439 /* another task is sharing our hash bucket */
440 continue;
441
442 if (ri->rp && ri->rp->handler)
443 ri->rp->handler(ri, regs);
444
445 orig_ret_address = (unsigned long)ri->ret_addr;
446 recycle_rp_inst(ri, &empty_rp);
447
448 if (orig_ret_address != trampoline_address)
449 /*
450 * This is the real return address. Any other
451 * instances associated with this task are for
452 * other calls deeper on the call stack
453 */
454 break;
455 }
456
457 kretprobe_assert(ri, orig_ret_address, trampoline_address);
458
459 /*
460 * We get here through one of two paths:
461 * 1. by taking a trap -> kprobe_handler() -> here
462 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
463 *
464 * When going back through (1), we need regs->nip to be setup properly
465 * as it is used to determine the return address from the trap.
466 * For (2), since nip is not honoured with optprobes, we instead setup
467 * the link register properly so that the subsequent 'blr' in
468 * kretprobe_trampoline jumps back to the right instruction.
469 *
470 * For nip, we should set the address to the previous instruction since
471 * we end up emulating it in kprobe_handler(), which increments the nip
472 * again.
473 */
474 regs->nip = orig_ret_address - 4;
475 regs->link = orig_ret_address;
476
477 kretprobe_hash_unlock(current, &flags);
478
479 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
480 hlist_del(&ri->hlist);
481 kfree(ri);
482 }
483
484 return 0;
485}
486NOKPROBE_SYMBOL(trampoline_probe_handler);
487
488/*
489 * Called after single-stepping. p->addr is the address of the
490 * instruction whose first byte has been replaced by the "breakpoint"
491 * instruction. To avoid the SMP problems that can occur when we
492 * temporarily put back the original opcode to single-step, we
493 * single-stepped a copy of the instruction. The address of this
494 * copy is p->ainsn.insn.
495 */
496int kprobe_post_handler(struct pt_regs *regs)
497{
498 struct kprobe *cur = kprobe_running();
499 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
500
501 if (!cur || user_mode(regs))
502 return 0;
503
504 /* make sure we got here for instruction we have a kprobe on */
505 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
506 return 0;
507
508 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
509 kcb->kprobe_status = KPROBE_HIT_SSDONE;
510 cur->post_handler(cur, regs, 0);
511 }
512
513 /* Adjust nip to after the single-stepped instruction */
514 regs->nip = (unsigned long)cur->addr + 4;
515 regs->msr |= kcb->kprobe_saved_msr;
516
517 /*Restore back the original saved kprobes variables and continue. */
518 if (kcb->kprobe_status == KPROBE_REENTER) {
519 restore_previous_kprobe(kcb);
520 goto out;
521 }
522 reset_current_kprobe();
523out:
524 preempt_enable_no_resched();
525
526 /*
527 * if somebody else is singlestepping across a probe point, msr
528 * will have DE/SE set, in which case, continue the remaining processing
529 * of do_debug, as if this is not a probe hit.
530 */
531 if (regs->msr & MSR_SINGLESTEP)
532 return 0;
533
534 return 1;
535}
536NOKPROBE_SYMBOL(kprobe_post_handler);
537
538int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
539{
540 struct kprobe *cur = kprobe_running();
541 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
542 const struct exception_table_entry *entry;
543
544 switch(kcb->kprobe_status) {
545 case KPROBE_HIT_SS:
546 case KPROBE_REENTER:
547 /*
548 * We are here because the instruction being single
549 * stepped caused a page fault. We reset the current
550 * kprobe and the nip points back to the probe address
551 * and allow the page fault handler to continue as a
552 * normal page fault.
553 */
554 regs->nip = (unsigned long)cur->addr;
555 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
556 regs->msr |= kcb->kprobe_saved_msr;
557 if (kcb->kprobe_status == KPROBE_REENTER)
558 restore_previous_kprobe(kcb);
559 else
560 reset_current_kprobe();
561 preempt_enable_no_resched();
562 break;
563 case KPROBE_HIT_ACTIVE:
564 case KPROBE_HIT_SSDONE:
565 /*
566 * We increment the nmissed count for accounting,
567 * we can also use npre/npostfault count for accounting
568 * these specific fault cases.
569 */
570 kprobes_inc_nmissed_count(cur);
571
572 /*
573 * We come here because instructions in the pre/post
574 * handler caused the page_fault, this could happen
575 * if handler tries to access user space by
576 * copy_from_user(), get_user() etc. Let the
577 * user-specified handler try to fix it first.
578 */
579 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
580 return 1;
581
582 /*
583 * In case the user-specified fault handler returned
584 * zero, try to fix up.
585 */
586 if ((entry = search_exception_tables(regs->nip)) != NULL) {
587 regs->nip = extable_fixup(entry);
588 return 1;
589 }
590
591 /*
592 * fixup_exception() could not handle it,
593 * Let do_page_fault() fix it.
594 */
595 break;
596 default:
597 break;
598 }
599 return 0;
600}
601NOKPROBE_SYMBOL(kprobe_fault_handler);
602
603unsigned long arch_deref_entry_point(void *entry)
604{
605#ifdef PPC64_ELF_ABI_v1
606 if (!kernel_text_address((unsigned long)entry))
607 return ppc_global_function_entry(entry);
608 else
609#endif
610 return (unsigned long)entry;
611}
612NOKPROBE_SYMBOL(arch_deref_entry_point);
613
614int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
615{
616 struct jprobe *jp = container_of(p, struct jprobe, kp);
617 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
618
619 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
620
621 /* setup return addr to the jprobe handler routine */
622 regs->nip = arch_deref_entry_point(jp->entry);
623#ifdef PPC64_ELF_ABI_v2
624 regs->gpr[12] = (unsigned long)jp->entry;
625#elif defined(PPC64_ELF_ABI_v1)
626 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
627#endif
628
629 /*
630 * jprobes use jprobe_return() which skips the normal return
631 * path of the function, and this messes up the accounting of the
632 * function graph tracer.
633 *
634 * Pause function graph tracing while performing the jprobe function.
635 */
636 pause_graph_tracing();
637
638 return 1;
639}
640NOKPROBE_SYMBOL(setjmp_pre_handler);
641
642void __used jprobe_return(void)
643{
644 asm volatile("jprobe_return_trap:\n"
645 "trap\n"
646 ::: "memory");
647}
648NOKPROBE_SYMBOL(jprobe_return);
649
650int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
651{
652 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
653
654 if (regs->nip != ppc_kallsyms_lookup_name("jprobe_return_trap")) {
655 pr_debug("longjmp_break_handler NIP (0x%lx) does not match jprobe_return_trap (0x%lx)\n",
656 regs->nip, ppc_kallsyms_lookup_name("jprobe_return_trap"));
657 return 0;
658 }
659
660 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
661 /* It's OK to start function graph tracing again */
662 unpause_graph_tracing();
663 preempt_enable_no_resched();
664 return 1;
665}
666NOKPROBE_SYMBOL(longjmp_break_handler);
667
668static struct kprobe trampoline_p = {
669 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
670 .pre_handler = trampoline_probe_handler
671};
672
673int __init arch_init_kprobes(void)
674{
675 return register_kprobe(&trampoline_p);
676}
677
678int arch_trampoline_kprobe(struct kprobe *p)
679{
680 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
681 return 1;
682
683 return 0;
684}
685NOKPROBE_SYMBOL(arch_trampoline_kprobe);
1/*
2 * Kernel Probes (KProbes)
3 *
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.
8 *
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.
13 *
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.
17 *
18 * Copyright (C) IBM Corporation, 2002, 2004
19 *
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
22 * Rusty Russell).
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
26 * for PPC64
27 */
28
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>
38
39DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
40DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
41
42struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
43
44int __kprobes arch_prepare_kprobe(struct kprobe *p)
45{
46 int ret = 0;
47 kprobe_opcode_t insn = *p->addr;
48
49 if ((unsigned long)p->addr & 0x03) {
50 printk("Attempt to register kprobe at an unaligned address\n");
51 ret = -EINVAL;
52 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
53 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
54 ret = -EINVAL;
55 }
56
57 /* insn must be on a special executable page on ppc64. This is
58 * not explicitly required on ppc32 (right now), but it doesn't hurt */
59 if (!ret) {
60 p->ainsn.insn = get_insn_slot();
61 if (!p->ainsn.insn)
62 ret = -ENOMEM;
63 }
64
65 if (!ret) {
66 memcpy(p->ainsn.insn, p->addr,
67 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
68 p->opcode = *p->addr;
69 flush_icache_range((unsigned long)p->ainsn.insn,
70 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
71 }
72
73 p->ainsn.boostable = 0;
74 return ret;
75}
76
77void __kprobes arch_arm_kprobe(struct kprobe *p)
78{
79 *p->addr = BREAKPOINT_INSTRUCTION;
80 flush_icache_range((unsigned long) p->addr,
81 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
82}
83
84void __kprobes arch_disarm_kprobe(struct kprobe *p)
85{
86 *p->addr = p->opcode;
87 flush_icache_range((unsigned long) p->addr,
88 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
89}
90
91void __kprobes arch_remove_kprobe(struct kprobe *p)
92{
93 if (p->ainsn.insn) {
94 free_insn_slot(p->ainsn.insn, 0);
95 p->ainsn.insn = NULL;
96 }
97}
98
99static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
100{
101 enable_single_step(regs);
102
103 /*
104 * On powerpc we should single step on the original
105 * instruction even if the probed insn is a trap
106 * variant as values in regs could play a part in
107 * if the trap is taken or not
108 */
109 regs->nip = (unsigned long)p->ainsn.insn;
110}
111
112static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
113{
114 kcb->prev_kprobe.kp = kprobe_running();
115 kcb->prev_kprobe.status = kcb->kprobe_status;
116 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
117}
118
119static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
120{
121 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
122 kcb->kprobe_status = kcb->prev_kprobe.status;
123 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
124}
125
126static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
127 struct kprobe_ctlblk *kcb)
128{
129 __get_cpu_var(current_kprobe) = p;
130 kcb->kprobe_saved_msr = regs->msr;
131}
132
133void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
134 struct pt_regs *regs)
135{
136 ri->ret_addr = (kprobe_opcode_t *)regs->link;
137
138 /* Replace the return addr with trampoline addr */
139 regs->link = (unsigned long)kretprobe_trampoline;
140}
141
142static int __kprobes kprobe_handler(struct pt_regs *regs)
143{
144 struct kprobe *p;
145 int ret = 0;
146 unsigned int *addr = (unsigned int *)regs->nip;
147 struct kprobe_ctlblk *kcb;
148
149 /*
150 * We don't want to be preempted for the entire
151 * duration of kprobe processing
152 */
153 preempt_disable();
154 kcb = get_kprobe_ctlblk();
155
156 /* Check we're not actually recursing */
157 if (kprobe_running()) {
158 p = get_kprobe(addr);
159 if (p) {
160 kprobe_opcode_t insn = *p->ainsn.insn;
161 if (kcb->kprobe_status == KPROBE_HIT_SS &&
162 is_trap(insn)) {
163 /* Turn off 'trace' bits */
164 regs->msr &= ~MSR_SINGLESTEP;
165 regs->msr |= kcb->kprobe_saved_msr;
166 goto no_kprobe;
167 }
168 /* We have reentered the kprobe_handler(), since
169 * another probe was hit while within the handler.
170 * We here save the original kprobes variables and
171 * just single step on the instruction of the new probe
172 * without calling any user handlers.
173 */
174 save_previous_kprobe(kcb);
175 set_current_kprobe(p, regs, kcb);
176 kcb->kprobe_saved_msr = regs->msr;
177 kprobes_inc_nmissed_count(p);
178 prepare_singlestep(p, regs);
179 kcb->kprobe_status = KPROBE_REENTER;
180 return 1;
181 } else {
182 if (*addr != BREAKPOINT_INSTRUCTION) {
183 /* If trap variant, then it belongs not to us */
184 kprobe_opcode_t cur_insn = *addr;
185 if (is_trap(cur_insn))
186 goto no_kprobe;
187 /* The breakpoint instruction was removed by
188 * another cpu right after we hit, no further
189 * handling of this interrupt is appropriate
190 */
191 ret = 1;
192 goto no_kprobe;
193 }
194 p = __get_cpu_var(current_kprobe);
195 if (p->break_handler && p->break_handler(p, regs)) {
196 goto ss_probe;
197 }
198 }
199 goto no_kprobe;
200 }
201
202 p = get_kprobe(addr);
203 if (!p) {
204 if (*addr != BREAKPOINT_INSTRUCTION) {
205 /*
206 * PowerPC has multiple variants of the "trap"
207 * instruction. If the current instruction is a
208 * trap variant, it could belong to someone else
209 */
210 kprobe_opcode_t cur_insn = *addr;
211 if (is_trap(cur_insn))
212 goto no_kprobe;
213 /*
214 * The breakpoint instruction was removed right
215 * after we hit it. Another cpu has removed
216 * either a probepoint or a debugger breakpoint
217 * at this address. In either case, no further
218 * handling of this interrupt is appropriate.
219 */
220 ret = 1;
221 }
222 /* Not one of ours: let kernel handle it */
223 goto no_kprobe;
224 }
225
226 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
227 set_current_kprobe(p, regs, kcb);
228 if (p->pre_handler && p->pre_handler(p, regs))
229 /* handler has already set things up, so skip ss setup */
230 return 1;
231
232ss_probe:
233 if (p->ainsn.boostable >= 0) {
234 unsigned int insn = *p->ainsn.insn;
235
236 /* regs->nip is also adjusted if emulate_step returns 1 */
237 ret = emulate_step(regs, insn);
238 if (ret > 0) {
239 /*
240 * Once this instruction has been boosted
241 * successfully, set the boostable flag
242 */
243 if (unlikely(p->ainsn.boostable == 0))
244 p->ainsn.boostable = 1;
245
246 if (p->post_handler)
247 p->post_handler(p, regs, 0);
248
249 kcb->kprobe_status = KPROBE_HIT_SSDONE;
250 reset_current_kprobe();
251 preempt_enable_no_resched();
252 return 1;
253 } else if (ret < 0) {
254 /*
255 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
256 * So, we should never get here... but, its still
257 * good to catch them, just in case...
258 */
259 printk("Can't step on instruction %x\n", insn);
260 BUG();
261 } else if (ret == 0)
262 /* This instruction can't be boosted */
263 p->ainsn.boostable = -1;
264 }
265 prepare_singlestep(p, regs);
266 kcb->kprobe_status = KPROBE_HIT_SS;
267 return 1;
268
269no_kprobe:
270 preempt_enable_no_resched();
271 return ret;
272}
273
274/*
275 * Function return probe trampoline:
276 * - init_kprobes() establishes a probepoint here
277 * - When the probed function returns, this probe
278 * causes the handlers to fire
279 */
280static void __used kretprobe_trampoline_holder(void)
281{
282 asm volatile(".global kretprobe_trampoline\n"
283 "kretprobe_trampoline:\n"
284 "nop\n");
285}
286
287/*
288 * Called when the probe at kretprobe trampoline is hit
289 */
290static int __kprobes trampoline_probe_handler(struct kprobe *p,
291 struct pt_regs *regs)
292{
293 struct kretprobe_instance *ri = NULL;
294 struct hlist_head *head, empty_rp;
295 struct hlist_node *tmp;
296 unsigned long flags, orig_ret_address = 0;
297 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
298
299 INIT_HLIST_HEAD(&empty_rp);
300 kretprobe_hash_lock(current, &head, &flags);
301
302 /*
303 * It is possible to have multiple instances associated with a given
304 * task either because an multiple functions in the call path
305 * have a return probe installed on them, and/or more than one return
306 * return probe was registered for a target function.
307 *
308 * We can handle this because:
309 * - instances are always inserted at the head of the list
310 * - when multiple return probes are registered for the same
311 * function, the first instance's ret_addr will point to the
312 * real return address, and all the rest will point to
313 * kretprobe_trampoline
314 */
315 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
316 if (ri->task != current)
317 /* another task is sharing our hash bucket */
318 continue;
319
320 if (ri->rp && ri->rp->handler)
321 ri->rp->handler(ri, regs);
322
323 orig_ret_address = (unsigned long)ri->ret_addr;
324 recycle_rp_inst(ri, &empty_rp);
325
326 if (orig_ret_address != trampoline_address)
327 /*
328 * This is the real return address. Any other
329 * instances associated with this task are for
330 * other calls deeper on the call stack
331 */
332 break;
333 }
334
335 kretprobe_assert(ri, orig_ret_address, trampoline_address);
336 regs->nip = orig_ret_address;
337
338 reset_current_kprobe();
339 kretprobe_hash_unlock(current, &flags);
340 preempt_enable_no_resched();
341
342 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
343 hlist_del(&ri->hlist);
344 kfree(ri);
345 }
346 /*
347 * By returning a non-zero value, we are telling
348 * kprobe_handler() that we don't want the post_handler
349 * to run (and have re-enabled preemption)
350 */
351 return 1;
352}
353
354/*
355 * Called after single-stepping. p->addr is the address of the
356 * instruction whose first byte has been replaced by the "breakpoint"
357 * instruction. To avoid the SMP problems that can occur when we
358 * temporarily put back the original opcode to single-step, we
359 * single-stepped a copy of the instruction. The address of this
360 * copy is p->ainsn.insn.
361 */
362static int __kprobes post_kprobe_handler(struct pt_regs *regs)
363{
364 struct kprobe *cur = kprobe_running();
365 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
366
367 if (!cur)
368 return 0;
369
370 /* make sure we got here for instruction we have a kprobe on */
371 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
372 return 0;
373
374 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
375 kcb->kprobe_status = KPROBE_HIT_SSDONE;
376 cur->post_handler(cur, regs, 0);
377 }
378
379 /* Adjust nip to after the single-stepped instruction */
380 regs->nip = (unsigned long)cur->addr + 4;
381 regs->msr |= kcb->kprobe_saved_msr;
382
383 /*Restore back the original saved kprobes variables and continue. */
384 if (kcb->kprobe_status == KPROBE_REENTER) {
385 restore_previous_kprobe(kcb);
386 goto out;
387 }
388 reset_current_kprobe();
389out:
390 preempt_enable_no_resched();
391
392 /*
393 * if somebody else is singlestepping across a probe point, msr
394 * will have DE/SE set, in which case, continue the remaining processing
395 * of do_debug, as if this is not a probe hit.
396 */
397 if (regs->msr & MSR_SINGLESTEP)
398 return 0;
399
400 return 1;
401}
402
403int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
404{
405 struct kprobe *cur = kprobe_running();
406 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
407 const struct exception_table_entry *entry;
408
409 switch(kcb->kprobe_status) {
410 case KPROBE_HIT_SS:
411 case KPROBE_REENTER:
412 /*
413 * We are here because the instruction being single
414 * stepped caused a page fault. We reset the current
415 * kprobe and the nip points back to the probe address
416 * and allow the page fault handler to continue as a
417 * normal page fault.
418 */
419 regs->nip = (unsigned long)cur->addr;
420 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
421 regs->msr |= kcb->kprobe_saved_msr;
422 if (kcb->kprobe_status == KPROBE_REENTER)
423 restore_previous_kprobe(kcb);
424 else
425 reset_current_kprobe();
426 preempt_enable_no_resched();
427 break;
428 case KPROBE_HIT_ACTIVE:
429 case KPROBE_HIT_SSDONE:
430 /*
431 * We increment the nmissed count for accounting,
432 * we can also use npre/npostfault count for accounting
433 * these specific fault cases.
434 */
435 kprobes_inc_nmissed_count(cur);
436
437 /*
438 * We come here because instructions in the pre/post
439 * handler caused the page_fault, this could happen
440 * if handler tries to access user space by
441 * copy_from_user(), get_user() etc. Let the
442 * user-specified handler try to fix it first.
443 */
444 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
445 return 1;
446
447 /*
448 * In case the user-specified fault handler returned
449 * zero, try to fix up.
450 */
451 if ((entry = search_exception_tables(regs->nip)) != NULL) {
452 regs->nip = entry->fixup;
453 return 1;
454 }
455
456 /*
457 * fixup_exception() could not handle it,
458 * Let do_page_fault() fix it.
459 */
460 break;
461 default:
462 break;
463 }
464 return 0;
465}
466
467/*
468 * Wrapper routine to for handling exceptions.
469 */
470int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
471 unsigned long val, void *data)
472{
473 struct die_args *args = (struct die_args *)data;
474 int ret = NOTIFY_DONE;
475
476 if (args->regs && user_mode(args->regs))
477 return ret;
478
479 switch (val) {
480 case DIE_BPT:
481 if (kprobe_handler(args->regs))
482 ret = NOTIFY_STOP;
483 break;
484 case DIE_SSTEP:
485 if (post_kprobe_handler(args->regs))
486 ret = NOTIFY_STOP;
487 break;
488 default:
489 break;
490 }
491 return ret;
492}
493
494#ifdef CONFIG_PPC64
495unsigned long arch_deref_entry_point(void *entry)
496{
497 return ((func_descr_t *)entry)->entry;
498}
499#endif
500
501int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
502{
503 struct jprobe *jp = container_of(p, struct jprobe, kp);
504 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
505
506 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
507
508 /* setup return addr to the jprobe handler routine */
509 regs->nip = arch_deref_entry_point(jp->entry);
510#ifdef CONFIG_PPC64
511 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
512#endif
513
514 return 1;
515}
516
517void __used __kprobes jprobe_return(void)
518{
519 asm volatile("trap" ::: "memory");
520}
521
522static void __used __kprobes jprobe_return_end(void)
523{
524};
525
526int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
527{
528 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
529
530 /*
531 * FIXME - we should ideally be validating that we got here 'cos
532 * of the "trap" in jprobe_return() above, before restoring the
533 * saved regs...
534 */
535 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
536 preempt_enable_no_resched();
537 return 1;
538}
539
540static struct kprobe trampoline_p = {
541 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
542 .pre_handler = trampoline_probe_handler
543};
544
545int __init arch_init_kprobes(void)
546{
547 return register_kprobe(&trampoline_p);
548}
549
550int __kprobes arch_trampoline_kprobe(struct kprobe *p)
551{
552 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
553 return 1;
554
555 return 0;
556}