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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 <linux/moduleloader.h>
23#include <linux/set_memory.h>
24#include <asm/code-patching.h>
25#include <asm/cacheflush.h>
26#include <asm/sstep.h>
27#include <asm/sections.h>
28#include <asm/inst.h>
29#include <linux/uaccess.h>
30
31DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
32DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
33
34struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
35
36bool arch_within_kprobe_blacklist(unsigned long addr)
37{
38 return (addr >= (unsigned long)__kprobes_text_start &&
39 addr < (unsigned long)__kprobes_text_end) ||
40 (addr >= (unsigned long)_stext &&
41 addr < (unsigned long)__head_end);
42}
43
44kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
45{
46 kprobe_opcode_t *addr = NULL;
47
48#ifdef CONFIG_PPC64_ELF_ABI_V2
49 /* PPC64 ABIv2 needs local entry point */
50 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
51 if (addr && !offset) {
52#ifdef CONFIG_KPROBES_ON_FTRACE
53 unsigned long faddr;
54 /*
55 * Per livepatch.h, ftrace location is always within the first
56 * 16 bytes of a function on powerpc with -mprofile-kernel.
57 */
58 faddr = ftrace_location_range((unsigned long)addr,
59 (unsigned long)addr + 16);
60 if (faddr)
61 addr = (kprobe_opcode_t *)faddr;
62 else
63#endif
64 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
65 }
66#elif defined(CONFIG_PPC64_ELF_ABI_V1)
67 /*
68 * 64bit powerpc ABIv1 uses function descriptors:
69 * - Check for the dot variant of the symbol first.
70 * - If that fails, try looking up the symbol provided.
71 *
72 * This ensures we always get to the actual symbol and not
73 * the descriptor.
74 *
75 * Also handle <module:symbol> format.
76 */
77 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
78 bool dot_appended = false;
79 const char *c;
80 ssize_t ret = 0;
81 int len = 0;
82
83 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
84 c++;
85 len = c - name;
86 memcpy(dot_name, name, len);
87 } else
88 c = name;
89
90 if (*c != '\0' && *c != '.') {
91 dot_name[len++] = '.';
92 dot_appended = true;
93 }
94 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
95 if (ret > 0)
96 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
97
98 /* Fallback to the original non-dot symbol lookup */
99 if (!addr && dot_appended)
100 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
101#else
102 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
103#endif
104
105 return addr;
106}
107
108static bool arch_kprobe_on_func_entry(unsigned long offset)
109{
110#ifdef CONFIG_PPC64_ELF_ABI_V2
111#ifdef CONFIG_KPROBES_ON_FTRACE
112 return offset <= 16;
113#else
114 return offset <= 8;
115#endif
116#else
117 return !offset;
118#endif
119}
120
121/* XXX try and fold the magic of kprobe_lookup_name() in this */
122kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
123 bool *on_func_entry)
124{
125 *on_func_entry = arch_kprobe_on_func_entry(offset);
126 return (kprobe_opcode_t *)(addr + offset);
127}
128
129void *alloc_insn_page(void)
130{
131 void *page;
132
133 page = module_alloc(PAGE_SIZE);
134 if (!page)
135 return NULL;
136
137 if (strict_module_rwx_enabled()) {
138 int err = set_memory_rox((unsigned long)page, 1);
139
140 if (err)
141 goto error;
142 }
143 return page;
144error:
145 module_memfree(page);
146 return NULL;
147}
148
149int arch_prepare_kprobe(struct kprobe *p)
150{
151 int ret = 0;
152 struct kprobe *prev;
153 ppc_inst_t insn = ppc_inst_read(p->addr);
154
155 if ((unsigned long)p->addr & 0x03) {
156 printk("Attempt to register kprobe at an unaligned address\n");
157 ret = -EINVAL;
158 } else if (!can_single_step(ppc_inst_val(insn))) {
159 printk("Cannot register a kprobe on instructions that can't be single stepped\n");
160 ret = -EINVAL;
161 } else if ((unsigned long)p->addr & ~PAGE_MASK &&
162 ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) {
163 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
164 ret = -EINVAL;
165 }
166 prev = get_kprobe(p->addr - 1);
167
168 /*
169 * When prev is a ftrace-based kprobe, we don't have an insn, and it
170 * doesn't probe for prefixed instruction.
171 */
172 if (prev && !kprobe_ftrace(prev) &&
173 ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
174 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
175 ret = -EINVAL;
176 }
177
178 /* insn must be on a special executable page on ppc64. This is
179 * not explicitly required on ppc32 (right now), but it doesn't hurt */
180 if (!ret) {
181 p->ainsn.insn = get_insn_slot();
182 if (!p->ainsn.insn)
183 ret = -ENOMEM;
184 }
185
186 if (!ret) {
187 patch_instruction(p->ainsn.insn, insn);
188 p->opcode = ppc_inst_val(insn);
189 }
190
191 p->ainsn.boostable = 0;
192 return ret;
193}
194NOKPROBE_SYMBOL(arch_prepare_kprobe);
195
196void arch_arm_kprobe(struct kprobe *p)
197{
198 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(BREAKPOINT_INSTRUCTION)));
199}
200NOKPROBE_SYMBOL(arch_arm_kprobe);
201
202void arch_disarm_kprobe(struct kprobe *p)
203{
204 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(p->opcode)));
205}
206NOKPROBE_SYMBOL(arch_disarm_kprobe);
207
208void arch_remove_kprobe(struct kprobe *p)
209{
210 if (p->ainsn.insn) {
211 free_insn_slot(p->ainsn.insn, 0);
212 p->ainsn.insn = NULL;
213 }
214}
215NOKPROBE_SYMBOL(arch_remove_kprobe);
216
217static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
218{
219 enable_single_step(regs);
220
221 /*
222 * On powerpc we should single step on the original
223 * instruction even if the probed insn is a trap
224 * variant as values in regs could play a part in
225 * if the trap is taken or not
226 */
227 regs_set_return_ip(regs, (unsigned long)p->ainsn.insn);
228}
229
230static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
231{
232 kcb->prev_kprobe.kp = kprobe_running();
233 kcb->prev_kprobe.status = kcb->kprobe_status;
234 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
235}
236
237static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
238{
239 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
240 kcb->kprobe_status = kcb->prev_kprobe.status;
241 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
242}
243
244static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
245 struct kprobe_ctlblk *kcb)
246{
247 __this_cpu_write(current_kprobe, p);
248 kcb->kprobe_saved_msr = regs->msr;
249}
250
251void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
252{
253 ri->ret_addr = (kprobe_opcode_t *)regs->link;
254 ri->fp = NULL;
255
256 /* Replace the return addr with trampoline addr */
257 regs->link = (unsigned long)__kretprobe_trampoline;
258}
259NOKPROBE_SYMBOL(arch_prepare_kretprobe);
260
261static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
262{
263 int ret;
264 ppc_inst_t insn = ppc_inst_read(p->ainsn.insn);
265
266 /* regs->nip is also adjusted if emulate_step returns 1 */
267 ret = emulate_step(regs, insn);
268 if (ret > 0) {
269 /*
270 * Once this instruction has been boosted
271 * successfully, set the boostable flag
272 */
273 if (unlikely(p->ainsn.boostable == 0))
274 p->ainsn.boostable = 1;
275 } else if (ret < 0) {
276 /*
277 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
278 * So, we should never get here... but, its still
279 * good to catch them, just in case...
280 */
281 printk("Can't step on instruction %08lx\n", ppc_inst_as_ulong(insn));
282 BUG();
283 } else {
284 /*
285 * If we haven't previously emulated this instruction, then it
286 * can't be boosted. Note it down so we don't try to do so again.
287 *
288 * If, however, we had emulated this instruction in the past,
289 * then this is just an error with the current run (for
290 * instance, exceptions due to a load/store). We return 0 so
291 * that this is now single-stepped, but continue to try
292 * emulating it in subsequent probe hits.
293 */
294 if (unlikely(p->ainsn.boostable != 1))
295 p->ainsn.boostable = -1;
296 }
297
298 return ret;
299}
300NOKPROBE_SYMBOL(try_to_emulate);
301
302int kprobe_handler(struct pt_regs *regs)
303{
304 struct kprobe *p;
305 int ret = 0;
306 unsigned int *addr = (unsigned int *)regs->nip;
307 struct kprobe_ctlblk *kcb;
308
309 if (user_mode(regs))
310 return 0;
311
312 if (!IS_ENABLED(CONFIG_BOOKE) &&
313 (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
314 return 0;
315
316 /*
317 * We don't want to be preempted for the entire
318 * duration of kprobe processing
319 */
320 preempt_disable();
321 kcb = get_kprobe_ctlblk();
322
323 p = get_kprobe(addr);
324 if (!p) {
325 unsigned int instr;
326
327 if (get_kernel_nofault(instr, addr))
328 goto no_kprobe;
329
330 if (instr != BREAKPOINT_INSTRUCTION) {
331 /*
332 * PowerPC has multiple variants of the "trap"
333 * instruction. If the current instruction is a
334 * trap variant, it could belong to someone else
335 */
336 if (is_trap(instr))
337 goto no_kprobe;
338 /*
339 * The breakpoint instruction was removed right
340 * after we hit it. Another cpu has removed
341 * either a probepoint or a debugger breakpoint
342 * at this address. In either case, no further
343 * handling of this interrupt is appropriate.
344 */
345 ret = 1;
346 }
347 /* Not one of ours: let kernel handle it */
348 goto no_kprobe;
349 }
350
351 /* Check we're not actually recursing */
352 if (kprobe_running()) {
353 kprobe_opcode_t insn = *p->ainsn.insn;
354 if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
355 /* Turn off 'trace' bits */
356 regs_set_return_msr(regs,
357 (regs->msr & ~MSR_SINGLESTEP) |
358 kcb->kprobe_saved_msr);
359 goto no_kprobe;
360 }
361
362 /*
363 * We have reentered the kprobe_handler(), since another probe
364 * was hit while within the handler. We here save the original
365 * kprobes variables and just single step on the instruction of
366 * the new probe without calling any user handlers.
367 */
368 save_previous_kprobe(kcb);
369 set_current_kprobe(p, regs, kcb);
370 kprobes_inc_nmissed_count(p);
371 kcb->kprobe_status = KPROBE_REENTER;
372 if (p->ainsn.boostable >= 0) {
373 ret = try_to_emulate(p, regs);
374
375 if (ret > 0) {
376 restore_previous_kprobe(kcb);
377 preempt_enable();
378 return 1;
379 }
380 }
381 prepare_singlestep(p, regs);
382 return 1;
383 }
384
385 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
386 set_current_kprobe(p, regs, kcb);
387 if (p->pre_handler && p->pre_handler(p, regs)) {
388 /* handler changed execution path, so skip ss setup */
389 reset_current_kprobe();
390 preempt_enable();
391 return 1;
392 }
393
394 if (p->ainsn.boostable >= 0) {
395 ret = try_to_emulate(p, regs);
396
397 if (ret > 0) {
398 if (p->post_handler)
399 p->post_handler(p, regs, 0);
400
401 kcb->kprobe_status = KPROBE_HIT_SSDONE;
402 reset_current_kprobe();
403 preempt_enable();
404 return 1;
405 }
406 }
407 prepare_singlestep(p, regs);
408 kcb->kprobe_status = KPROBE_HIT_SS;
409 return 1;
410
411no_kprobe:
412 preempt_enable();
413 return ret;
414}
415NOKPROBE_SYMBOL(kprobe_handler);
416
417/*
418 * Function return probe trampoline:
419 * - init_kprobes() establishes a probepoint here
420 * - When the probed function returns, this probe
421 * causes the handlers to fire
422 */
423asm(".global __kretprobe_trampoline\n"
424 ".type __kretprobe_trampoline, @function\n"
425 "__kretprobe_trampoline:\n"
426 "nop\n"
427 "blr\n"
428 ".size __kretprobe_trampoline, .-__kretprobe_trampoline\n");
429
430/*
431 * Called when the probe at kretprobe trampoline is hit
432 */
433static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
434{
435 unsigned long orig_ret_address;
436
437 orig_ret_address = __kretprobe_trampoline_handler(regs, NULL);
438 /*
439 * We get here through one of two paths:
440 * 1. by taking a trap -> kprobe_handler() -> here
441 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
442 *
443 * When going back through (1), we need regs->nip to be setup properly
444 * as it is used to determine the return address from the trap.
445 * For (2), since nip is not honoured with optprobes, we instead setup
446 * the link register properly so that the subsequent 'blr' in
447 * __kretprobe_trampoline jumps back to the right instruction.
448 *
449 * For nip, we should set the address to the previous instruction since
450 * we end up emulating it in kprobe_handler(), which increments the nip
451 * again.
452 */
453 regs_set_return_ip(regs, orig_ret_address - 4);
454 regs->link = orig_ret_address;
455
456 return 0;
457}
458NOKPROBE_SYMBOL(trampoline_probe_handler);
459
460/*
461 * Called after single-stepping. p->addr is the address of the
462 * instruction whose first byte has been replaced by the "breakpoint"
463 * instruction. To avoid the SMP problems that can occur when we
464 * temporarily put back the original opcode to single-step, we
465 * single-stepped a copy of the instruction. The address of this
466 * copy is p->ainsn.insn.
467 */
468int kprobe_post_handler(struct pt_regs *regs)
469{
470 int len;
471 struct kprobe *cur = kprobe_running();
472 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
473
474 if (!cur || user_mode(regs))
475 return 0;
476
477 len = ppc_inst_len(ppc_inst_read(cur->ainsn.insn));
478 /* make sure we got here for instruction we have a kprobe on */
479 if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
480 return 0;
481
482 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
483 kcb->kprobe_status = KPROBE_HIT_SSDONE;
484 cur->post_handler(cur, regs, 0);
485 }
486
487 /* Adjust nip to after the single-stepped instruction */
488 regs_set_return_ip(regs, (unsigned long)cur->addr + len);
489 regs_set_return_msr(regs, regs->msr | kcb->kprobe_saved_msr);
490
491 /*Restore back the original saved kprobes variables and continue. */
492 if (kcb->kprobe_status == KPROBE_REENTER) {
493 restore_previous_kprobe(kcb);
494 goto out;
495 }
496 reset_current_kprobe();
497out:
498 preempt_enable();
499
500 /*
501 * if somebody else is singlestepping across a probe point, msr
502 * will have DE/SE set, in which case, continue the remaining processing
503 * of do_debug, as if this is not a probe hit.
504 */
505 if (regs->msr & MSR_SINGLESTEP)
506 return 0;
507
508 return 1;
509}
510NOKPROBE_SYMBOL(kprobe_post_handler);
511
512int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
513{
514 struct kprobe *cur = kprobe_running();
515 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
516 const struct exception_table_entry *entry;
517
518 switch(kcb->kprobe_status) {
519 case KPROBE_HIT_SS:
520 case KPROBE_REENTER:
521 /*
522 * We are here because the instruction being single
523 * stepped caused a page fault. We reset the current
524 * kprobe and the nip points back to the probe address
525 * and allow the page fault handler to continue as a
526 * normal page fault.
527 */
528 regs_set_return_ip(regs, (unsigned long)cur->addr);
529 /* Turn off 'trace' bits */
530 regs_set_return_msr(regs,
531 (regs->msr & ~MSR_SINGLESTEP) |
532 kcb->kprobe_saved_msr);
533 if (kcb->kprobe_status == KPROBE_REENTER)
534 restore_previous_kprobe(kcb);
535 else
536 reset_current_kprobe();
537 preempt_enable();
538 break;
539 case KPROBE_HIT_ACTIVE:
540 case KPROBE_HIT_SSDONE:
541 /*
542 * In case the user-specified fault handler returned
543 * zero, try to fix up.
544 */
545 if ((entry = search_exception_tables(regs->nip)) != NULL) {
546 regs_set_return_ip(regs, extable_fixup(entry));
547 return 1;
548 }
549
550 /*
551 * fixup_exception() could not handle it,
552 * Let do_page_fault() fix it.
553 */
554 break;
555 default:
556 break;
557 }
558 return 0;
559}
560NOKPROBE_SYMBOL(kprobe_fault_handler);
561
562static struct kprobe trampoline_p = {
563 .addr = (kprobe_opcode_t *) &__kretprobe_trampoline,
564 .pre_handler = trampoline_probe_handler
565};
566
567int __init arch_init_kprobes(void)
568{
569 return register_kprobe(&trampoline_p);
570}
571
572int arch_trampoline_kprobe(struct kprobe *p)
573{
574 if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
575 return 1;
576
577 return 0;
578}
579NOKPROBE_SYMBOL(arch_trampoline_kprobe);