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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// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright (C) IBM Corporation, 2002, 2004
6 *
7 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
8 * Probes initial implementation ( includes contributions from
9 * Rusty Russell).
10 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
11 * interface to access function arguments.
12 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
13 * for PPC64
14 */
15
16#include <linux/kprobes.h>
17#include <linux/ptrace.h>
18#include <linux/preempt.h>
19#include <linux/extable.h>
20#include <linux/kdebug.h>
21#include <linux/slab.h>
22#include <asm/code-patching.h>
23#include <asm/cacheflush.h>
24#include <asm/sstep.h>
25#include <asm/sections.h>
26#include <linux/uaccess.h>
27
28DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
29DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
30
31struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
32
33bool arch_within_kprobe_blacklist(unsigned long addr)
34{
35 return (addr >= (unsigned long)__kprobes_text_start &&
36 addr < (unsigned long)__kprobes_text_end) ||
37 (addr >= (unsigned long)_stext &&
38 addr < (unsigned long)__head_end);
39}
40
41kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
42{
43 kprobe_opcode_t *addr = NULL;
44
45#ifdef PPC64_ELF_ABI_v2
46 /* PPC64 ABIv2 needs local entry point */
47 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
48 if (addr && !offset) {
49#ifdef CONFIG_KPROBES_ON_FTRACE
50 unsigned long faddr;
51 /*
52 * Per livepatch.h, ftrace location is always within the first
53 * 16 bytes of a function on powerpc with -mprofile-kernel.
54 */
55 faddr = ftrace_location_range((unsigned long)addr,
56 (unsigned long)addr + 16);
57 if (faddr)
58 addr = (kprobe_opcode_t *)faddr;
59 else
60#endif
61 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
62 }
63#elif defined(PPC64_ELF_ABI_v1)
64 /*
65 * 64bit powerpc ABIv1 uses function descriptors:
66 * - Check for the dot variant of the symbol first.
67 * - If that fails, try looking up the symbol provided.
68 *
69 * This ensures we always get to the actual symbol and not
70 * the descriptor.
71 *
72 * Also handle <module:symbol> format.
73 */
74 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
75 bool dot_appended = false;
76 const char *c;
77 ssize_t ret = 0;
78 int len = 0;
79
80 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
81 c++;
82 len = c - name;
83 memcpy(dot_name, name, len);
84 } else
85 c = name;
86
87 if (*c != '\0' && *c != '.') {
88 dot_name[len++] = '.';
89 dot_appended = true;
90 }
91 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
92 if (ret > 0)
93 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
94
95 /* Fallback to the original non-dot symbol lookup */
96 if (!addr && dot_appended)
97 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
98#else
99 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
100#endif
101
102 return addr;
103}
104
105int arch_prepare_kprobe(struct kprobe *p)
106{
107 int ret = 0;
108 kprobe_opcode_t insn = *p->addr;
109
110 if ((unsigned long)p->addr & 0x03) {
111 printk("Attempt to register kprobe at an unaligned address\n");
112 ret = -EINVAL;
113 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
114 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
115 ret = -EINVAL;
116 }
117
118 /* insn must be on a special executable page on ppc64. This is
119 * not explicitly required on ppc32 (right now), but it doesn't hurt */
120 if (!ret) {
121 p->ainsn.insn = get_insn_slot();
122 if (!p->ainsn.insn)
123 ret = -ENOMEM;
124 }
125
126 if (!ret) {
127 memcpy(p->ainsn.insn, p->addr,
128 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
129 p->opcode = *p->addr;
130 flush_icache_range((unsigned long)p->ainsn.insn,
131 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
132 }
133
134 p->ainsn.boostable = 0;
135 return ret;
136}
137NOKPROBE_SYMBOL(arch_prepare_kprobe);
138
139void arch_arm_kprobe(struct kprobe *p)
140{
141 patch_instruction(p->addr, BREAKPOINT_INSTRUCTION);
142}
143NOKPROBE_SYMBOL(arch_arm_kprobe);
144
145void arch_disarm_kprobe(struct kprobe *p)
146{
147 patch_instruction(p->addr, p->opcode);
148}
149NOKPROBE_SYMBOL(arch_disarm_kprobe);
150
151void arch_remove_kprobe(struct kprobe *p)
152{
153 if (p->ainsn.insn) {
154 free_insn_slot(p->ainsn.insn, 0);
155 p->ainsn.insn = NULL;
156 }
157}
158NOKPROBE_SYMBOL(arch_remove_kprobe);
159
160static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
161{
162 enable_single_step(regs);
163
164 /*
165 * On powerpc we should single step on the original
166 * instruction even if the probed insn is a trap
167 * variant as values in regs could play a part in
168 * if the trap is taken or not
169 */
170 regs->nip = (unsigned long)p->ainsn.insn;
171}
172
173static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
174{
175 kcb->prev_kprobe.kp = kprobe_running();
176 kcb->prev_kprobe.status = kcb->kprobe_status;
177 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
178}
179
180static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
181{
182 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
183 kcb->kprobe_status = kcb->prev_kprobe.status;
184 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
185}
186
187static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
188 struct kprobe_ctlblk *kcb)
189{
190 __this_cpu_write(current_kprobe, p);
191 kcb->kprobe_saved_msr = regs->msr;
192}
193
194bool arch_kprobe_on_func_entry(unsigned long offset)
195{
196#ifdef PPC64_ELF_ABI_v2
197#ifdef CONFIG_KPROBES_ON_FTRACE
198 return offset <= 16;
199#else
200 return offset <= 8;
201#endif
202#else
203 return !offset;
204#endif
205}
206
207void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
208{
209 ri->ret_addr = (kprobe_opcode_t *)regs->link;
210
211 /* Replace the return addr with trampoline addr */
212 regs->link = (unsigned long)kretprobe_trampoline;
213}
214NOKPROBE_SYMBOL(arch_prepare_kretprobe);
215
216static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
217{
218 int ret;
219 unsigned int insn = *p->ainsn.insn;
220
221 /* regs->nip is also adjusted if emulate_step returns 1 */
222 ret = emulate_step(regs, insn);
223 if (ret > 0) {
224 /*
225 * Once this instruction has been boosted
226 * successfully, set the boostable flag
227 */
228 if (unlikely(p->ainsn.boostable == 0))
229 p->ainsn.boostable = 1;
230 } else if (ret < 0) {
231 /*
232 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
233 * So, we should never get here... but, its still
234 * good to catch them, just in case...
235 */
236 printk("Can't step on instruction %x\n", insn);
237 BUG();
238 } else {
239 /*
240 * If we haven't previously emulated this instruction, then it
241 * can't be boosted. Note it down so we don't try to do so again.
242 *
243 * If, however, we had emulated this instruction in the past,
244 * then this is just an error with the current run (for
245 * instance, exceptions due to a load/store). We return 0 so
246 * that this is now single-stepped, but continue to try
247 * emulating it in subsequent probe hits.
248 */
249 if (unlikely(p->ainsn.boostable != 1))
250 p->ainsn.boostable = -1;
251 }
252
253 return ret;
254}
255NOKPROBE_SYMBOL(try_to_emulate);
256
257int kprobe_handler(struct pt_regs *regs)
258{
259 struct kprobe *p;
260 int ret = 0;
261 unsigned int *addr = (unsigned int *)regs->nip;
262 struct kprobe_ctlblk *kcb;
263
264 if (user_mode(regs))
265 return 0;
266
267 /*
268 * We don't want to be preempted for the entire
269 * duration of kprobe processing
270 */
271 preempt_disable();
272 kcb = get_kprobe_ctlblk();
273
274 /* Check we're not actually recursing */
275 if (kprobe_running()) {
276 p = get_kprobe(addr);
277 if (p) {
278 kprobe_opcode_t insn = *p->ainsn.insn;
279 if (kcb->kprobe_status == KPROBE_HIT_SS &&
280 is_trap(insn)) {
281 /* Turn off 'trace' bits */
282 regs->msr &= ~MSR_SINGLESTEP;
283 regs->msr |= kcb->kprobe_saved_msr;
284 goto no_kprobe;
285 }
286 /* We have reentered the kprobe_handler(), since
287 * another probe was hit while within the handler.
288 * We here save the original kprobes variables and
289 * just single step on the instruction of the new probe
290 * without calling any user handlers.
291 */
292 save_previous_kprobe(kcb);
293 set_current_kprobe(p, regs, kcb);
294 kprobes_inc_nmissed_count(p);
295 kcb->kprobe_status = KPROBE_REENTER;
296 if (p->ainsn.boostable >= 0) {
297 ret = try_to_emulate(p, regs);
298
299 if (ret > 0) {
300 restore_previous_kprobe(kcb);
301 preempt_enable_no_resched();
302 return 1;
303 }
304 }
305 prepare_singlestep(p, regs);
306 return 1;
307 } else if (*addr != BREAKPOINT_INSTRUCTION) {
308 /* If trap variant, then it belongs not to us */
309 kprobe_opcode_t cur_insn = *addr;
310
311 if (is_trap(cur_insn))
312 goto no_kprobe;
313 /* The breakpoint instruction was removed by
314 * another cpu right after we hit, no further
315 * handling of this interrupt is appropriate
316 */
317 ret = 1;
318 }
319 goto no_kprobe;
320 }
321
322 p = get_kprobe(addr);
323 if (!p) {
324 if (*addr != BREAKPOINT_INSTRUCTION) {
325 /*
326 * PowerPC has multiple variants of the "trap"
327 * instruction. If the current instruction is a
328 * trap variant, it could belong to someone else
329 */
330 kprobe_opcode_t cur_insn = *addr;
331 if (is_trap(cur_insn))
332 goto no_kprobe;
333 /*
334 * The breakpoint instruction was removed right
335 * after we hit it. Another cpu has removed
336 * either a probepoint or a debugger breakpoint
337 * at this address. In either case, no further
338 * handling of this interrupt is appropriate.
339 */
340 ret = 1;
341 }
342 /* Not one of ours: let kernel handle it */
343 goto no_kprobe;
344 }
345
346 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
347 set_current_kprobe(p, regs, kcb);
348 if (p->pre_handler && p->pre_handler(p, regs)) {
349 /* handler changed execution path, so skip ss setup */
350 reset_current_kprobe();
351 preempt_enable_no_resched();
352 return 1;
353 }
354
355 if (p->ainsn.boostable >= 0) {
356 ret = try_to_emulate(p, regs);
357
358 if (ret > 0) {
359 if (p->post_handler)
360 p->post_handler(p, regs, 0);
361
362 kcb->kprobe_status = KPROBE_HIT_SSDONE;
363 reset_current_kprobe();
364 preempt_enable_no_resched();
365 return 1;
366 }
367 }
368 prepare_singlestep(p, regs);
369 kcb->kprobe_status = KPROBE_HIT_SS;
370 return 1;
371
372no_kprobe:
373 preempt_enable_no_resched();
374 return ret;
375}
376NOKPROBE_SYMBOL(kprobe_handler);
377
378/*
379 * Function return probe trampoline:
380 * - init_kprobes() establishes a probepoint here
381 * - When the probed function returns, this probe
382 * causes the handlers to fire
383 */
384asm(".global kretprobe_trampoline\n"
385 ".type kretprobe_trampoline, @function\n"
386 "kretprobe_trampoline:\n"
387 "nop\n"
388 "blr\n"
389 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
390
391/*
392 * Called when the probe at kretprobe trampoline is hit
393 */
394static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
395{
396 struct kretprobe_instance *ri = NULL;
397 struct hlist_head *head, empty_rp;
398 struct hlist_node *tmp;
399 unsigned long flags, orig_ret_address = 0;
400 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
401
402 INIT_HLIST_HEAD(&empty_rp);
403 kretprobe_hash_lock(current, &head, &flags);
404
405 /*
406 * It is possible to have multiple instances associated with a given
407 * task either because an multiple functions in the call path
408 * have a return probe installed on them, and/or more than one return
409 * return probe was registered for a target function.
410 *
411 * We can handle this because:
412 * - instances are always inserted at the head of the list
413 * - when multiple return probes are registered for the same
414 * function, the first instance's ret_addr will point to the
415 * real return address, and all the rest will point to
416 * kretprobe_trampoline
417 */
418 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
419 if (ri->task != current)
420 /* another task is sharing our hash bucket */
421 continue;
422
423 if (ri->rp && ri->rp->handler)
424 ri->rp->handler(ri, regs);
425
426 orig_ret_address = (unsigned long)ri->ret_addr;
427 recycle_rp_inst(ri, &empty_rp);
428
429 if (orig_ret_address != trampoline_address)
430 /*
431 * This is the real return address. Any other
432 * instances associated with this task are for
433 * other calls deeper on the call stack
434 */
435 break;
436 }
437
438 kretprobe_assert(ri, orig_ret_address, trampoline_address);
439
440 /*
441 * We get here through one of two paths:
442 * 1. by taking a trap -> kprobe_handler() -> here
443 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
444 *
445 * When going back through (1), we need regs->nip to be setup properly
446 * as it is used to determine the return address from the trap.
447 * For (2), since nip is not honoured with optprobes, we instead setup
448 * the link register properly so that the subsequent 'blr' in
449 * kretprobe_trampoline jumps back to the right instruction.
450 *
451 * For nip, we should set the address to the previous instruction since
452 * we end up emulating it in kprobe_handler(), which increments the nip
453 * again.
454 */
455 regs->nip = orig_ret_address - 4;
456 regs->link = orig_ret_address;
457
458 kretprobe_hash_unlock(current, &flags);
459
460 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
461 hlist_del(&ri->hlist);
462 kfree(ri);
463 }
464
465 return 0;
466}
467NOKPROBE_SYMBOL(trampoline_probe_handler);
468
469/*
470 * Called after single-stepping. p->addr is the address of the
471 * instruction whose first byte has been replaced by the "breakpoint"
472 * instruction. To avoid the SMP problems that can occur when we
473 * temporarily put back the original opcode to single-step, we
474 * single-stepped a copy of the instruction. The address of this
475 * copy is p->ainsn.insn.
476 */
477int kprobe_post_handler(struct pt_regs *regs)
478{
479 struct kprobe *cur = kprobe_running();
480 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
481
482 if (!cur || user_mode(regs))
483 return 0;
484
485 /* make sure we got here for instruction we have a kprobe on */
486 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
487 return 0;
488
489 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
490 kcb->kprobe_status = KPROBE_HIT_SSDONE;
491 cur->post_handler(cur, regs, 0);
492 }
493
494 /* Adjust nip to after the single-stepped instruction */
495 regs->nip = (unsigned long)cur->addr + 4;
496 regs->msr |= kcb->kprobe_saved_msr;
497
498 /*Restore back the original saved kprobes variables and continue. */
499 if (kcb->kprobe_status == KPROBE_REENTER) {
500 restore_previous_kprobe(kcb);
501 goto out;
502 }
503 reset_current_kprobe();
504out:
505 preempt_enable_no_resched();
506
507 /*
508 * if somebody else is singlestepping across a probe point, msr
509 * will have DE/SE set, in which case, continue the remaining processing
510 * of do_debug, as if this is not a probe hit.
511 */
512 if (regs->msr & MSR_SINGLESTEP)
513 return 0;
514
515 return 1;
516}
517NOKPROBE_SYMBOL(kprobe_post_handler);
518
519int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
520{
521 struct kprobe *cur = kprobe_running();
522 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
523 const struct exception_table_entry *entry;
524
525 switch(kcb->kprobe_status) {
526 case KPROBE_HIT_SS:
527 case KPROBE_REENTER:
528 /*
529 * We are here because the instruction being single
530 * stepped caused a page fault. We reset the current
531 * kprobe and the nip points back to the probe address
532 * and allow the page fault handler to continue as a
533 * normal page fault.
534 */
535 regs->nip = (unsigned long)cur->addr;
536 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
537 regs->msr |= kcb->kprobe_saved_msr;
538 if (kcb->kprobe_status == KPROBE_REENTER)
539 restore_previous_kprobe(kcb);
540 else
541 reset_current_kprobe();
542 preempt_enable_no_resched();
543 break;
544 case KPROBE_HIT_ACTIVE:
545 case KPROBE_HIT_SSDONE:
546 /*
547 * We increment the nmissed count for accounting,
548 * we can also use npre/npostfault count for accounting
549 * these specific fault cases.
550 */
551 kprobes_inc_nmissed_count(cur);
552
553 /*
554 * We come here because instructions in the pre/post
555 * handler caused the page_fault, this could happen
556 * if handler tries to access user space by
557 * copy_from_user(), get_user() etc. Let the
558 * user-specified handler try to fix it first.
559 */
560 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
561 return 1;
562
563 /*
564 * In case the user-specified fault handler returned
565 * zero, try to fix up.
566 */
567 if ((entry = search_exception_tables(regs->nip)) != NULL) {
568 regs->nip = extable_fixup(entry);
569 return 1;
570 }
571
572 /*
573 * fixup_exception() could not handle it,
574 * Let do_page_fault() fix it.
575 */
576 break;
577 default:
578 break;
579 }
580 return 0;
581}
582NOKPROBE_SYMBOL(kprobe_fault_handler);
583
584unsigned long arch_deref_entry_point(void *entry)
585{
586#ifdef PPC64_ELF_ABI_v1
587 if (!kernel_text_address((unsigned long)entry))
588 return ppc_global_function_entry(entry);
589 else
590#endif
591 return (unsigned long)entry;
592}
593NOKPROBE_SYMBOL(arch_deref_entry_point);
594
595static struct kprobe trampoline_p = {
596 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
597 .pre_handler = trampoline_probe_handler
598};
599
600int __init arch_init_kprobes(void)
601{
602 return register_kprobe(&trampoline_p);
603}
604
605int arch_trampoline_kprobe(struct kprobe *p)
606{
607 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
608 return 1;
609
610 return 0;
611}
612NOKPROBE_SYMBOL(arch_trampoline_kprobe);