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1/*
2 * Kernel Probes (KProbes)
3 * arch/mips/kernel/kprobes.c
4 *
5 * Copyright 2006 Sony Corp.
6 * Copyright 2010 Cavium Networks
7 *
8 * Some portions copied from the powerpc version.
9 *
10 * Copyright (C) IBM Corporation, 2002, 2004
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; version 2 of the License.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 */
25
26#include <linux/kprobes.h>
27#include <linux/preempt.h>
28#include <linux/uaccess.h>
29#include <linux/kdebug.h>
30#include <linux/slab.h>
31
32#include <asm/ptrace.h>
33#include <asm/branch.h>
34#include <asm/break.h>
35#include <asm/inst.h>
36
37static const union mips_instruction breakpoint_insn = {
38 .b_format = {
39 .opcode = spec_op,
40 .code = BRK_KPROBE_BP,
41 .func = break_op
42 }
43};
44
45static const union mips_instruction breakpoint2_insn = {
46 .b_format = {
47 .opcode = spec_op,
48 .code = BRK_KPROBE_SSTEPBP,
49 .func = break_op
50 }
51};
52
53DEFINE_PER_CPU(struct kprobe *, current_kprobe);
54DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
55
56static int __kprobes insn_has_delayslot(union mips_instruction insn)
57{
58 switch (insn.i_format.opcode) {
59
60 /*
61 * This group contains:
62 * jr and jalr are in r_format format.
63 */
64 case spec_op:
65 switch (insn.r_format.func) {
66 case jr_op:
67 case jalr_op:
68 break;
69 default:
70 goto insn_ok;
71 }
72
73 /*
74 * This group contains:
75 * bltz_op, bgez_op, bltzl_op, bgezl_op,
76 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
77 */
78 case bcond_op:
79
80 /*
81 * These are unconditional and in j_format.
82 */
83 case jal_op:
84 case j_op:
85
86 /*
87 * These are conditional and in i_format.
88 */
89 case beq_op:
90 case beql_op:
91 case bne_op:
92 case bnel_op:
93 case blez_op:
94 case blezl_op:
95 case bgtz_op:
96 case bgtzl_op:
97
98 /*
99 * These are the FPA/cp1 branch instructions.
100 */
101 case cop1_op:
102
103#ifdef CONFIG_CPU_CAVIUM_OCTEON
104 case lwc2_op: /* This is bbit0 on Octeon */
105 case ldc2_op: /* This is bbit032 on Octeon */
106 case swc2_op: /* This is bbit1 on Octeon */
107 case sdc2_op: /* This is bbit132 on Octeon */
108#endif
109 return 1;
110 default:
111 break;
112 }
113insn_ok:
114 return 0;
115}
116
117/*
118 * insn_has_ll_or_sc function checks whether instruction is ll or sc
119 * one; putting breakpoint on top of atomic ll/sc pair is bad idea;
120 * so we need to prevent it and refuse kprobes insertion for such
121 * instructions; cannot do much about breakpoint in the middle of
122 * ll/sc pair; it is upto user to avoid those places
123 */
124static int __kprobes insn_has_ll_or_sc(union mips_instruction insn)
125{
126 int ret = 0;
127
128 switch (insn.i_format.opcode) {
129 case ll_op:
130 case lld_op:
131 case sc_op:
132 case scd_op:
133 ret = 1;
134 break;
135 default:
136 break;
137 }
138 return ret;
139}
140
141int __kprobes arch_prepare_kprobe(struct kprobe *p)
142{
143 union mips_instruction insn;
144 union mips_instruction prev_insn;
145 int ret = 0;
146
147 insn = p->addr[0];
148
149 if (insn_has_ll_or_sc(insn)) {
150 pr_notice("Kprobes for ll and sc instructions are not"
151 "supported\n");
152 ret = -EINVAL;
153 goto out;
154 }
155
156 if ((probe_kernel_read(&prev_insn, p->addr - 1,
157 sizeof(mips_instruction)) == 0) &&
158 insn_has_delayslot(prev_insn)) {
159 pr_notice("Kprobes for branch delayslot are not supported\n");
160 ret = -EINVAL;
161 goto out;
162 }
163
164 /* insn: must be on special executable page on mips. */
165 p->ainsn.insn = get_insn_slot();
166 if (!p->ainsn.insn) {
167 ret = -ENOMEM;
168 goto out;
169 }
170
171 /*
172 * In the kprobe->ainsn.insn[] array we store the original
173 * instruction at index zero and a break trap instruction at
174 * index one.
175 *
176 * On MIPS arch if the instruction at probed address is a
177 * branch instruction, we need to execute the instruction at
178 * Branch Delayslot (BD) at the time of probe hit. As MIPS also
179 * doesn't have single stepping support, the BD instruction can
180 * not be executed in-line and it would be executed on SSOL slot
181 * using a normal breakpoint instruction in the next slot.
182 * So, read the instruction and save it for later execution.
183 */
184 if (insn_has_delayslot(insn))
185 memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t));
186 else
187 memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
188
189 p->ainsn.insn[1] = breakpoint2_insn;
190 p->opcode = *p->addr;
191
192out:
193 return ret;
194}
195
196void __kprobes arch_arm_kprobe(struct kprobe *p)
197{
198 *p->addr = breakpoint_insn;
199 flush_insn_slot(p);
200}
201
202void __kprobes arch_disarm_kprobe(struct kprobe *p)
203{
204 *p->addr = p->opcode;
205 flush_insn_slot(p);
206}
207
208void __kprobes arch_remove_kprobe(struct kprobe *p)
209{
210 free_insn_slot(p->ainsn.insn, 0);
211}
212
213static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
214{
215 kcb->prev_kprobe.kp = kprobe_running();
216 kcb->prev_kprobe.status = kcb->kprobe_status;
217 kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR;
218 kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR;
219 kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc;
220}
221
222static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
223{
224 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
225 kcb->kprobe_status = kcb->prev_kprobe.status;
226 kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR;
227 kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR;
228 kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc;
229}
230
231static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
232 struct kprobe_ctlblk *kcb)
233{
234 __get_cpu_var(current_kprobe) = p;
235 kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE);
236 kcb->kprobe_saved_epc = regs->cp0_epc;
237}
238
239/**
240 * evaluate_branch_instrucion -
241 *
242 * Evaluate the branch instruction at probed address during probe hit. The
243 * result of evaluation would be the updated epc. The insturction in delayslot
244 * would actually be single stepped using a normal breakpoint) on SSOL slot.
245 *
246 * The result is also saved in the kprobe control block for later use,
247 * in case we need to execute the delayslot instruction. The latter will be
248 * false for NOP instruction in dealyslot and the branch-likely instructions
249 * when the branch is taken. And for those cases we set a flag as
250 * SKIP_DELAYSLOT in the kprobe control block
251 */
252static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs,
253 struct kprobe_ctlblk *kcb)
254{
255 union mips_instruction insn = p->opcode;
256 long epc;
257 int ret = 0;
258
259 epc = regs->cp0_epc;
260 if (epc & 3)
261 goto unaligned;
262
263 if (p->ainsn.insn->word == 0)
264 kcb->flags |= SKIP_DELAYSLOT;
265 else
266 kcb->flags &= ~SKIP_DELAYSLOT;
267
268 ret = __compute_return_epc_for_insn(regs, insn);
269 if (ret < 0)
270 return ret;
271
272 if (ret == BRANCH_LIKELY_TAKEN)
273 kcb->flags |= SKIP_DELAYSLOT;
274
275 kcb->target_epc = regs->cp0_epc;
276
277 return 0;
278
279unaligned:
280 pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm);
281 force_sig(SIGBUS, current);
282 return -EFAULT;
283
284}
285
286static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
287 struct kprobe_ctlblk *kcb)
288{
289 int ret = 0;
290
291 regs->cp0_status &= ~ST0_IE;
292
293 /* single step inline if the instruction is a break */
294 if (p->opcode.word == breakpoint_insn.word ||
295 p->opcode.word == breakpoint2_insn.word)
296 regs->cp0_epc = (unsigned long)p->addr;
297 else if (insn_has_delayslot(p->opcode)) {
298 ret = evaluate_branch_instruction(p, regs, kcb);
299 if (ret < 0) {
300 pr_notice("Kprobes: Error in evaluating branch\n");
301 return;
302 }
303 }
304 regs->cp0_epc = (unsigned long)&p->ainsn.insn[0];
305}
306
307/*
308 * Called after single-stepping. p->addr is the address of the
309 * instruction whose first byte has been replaced by the "break 0"
310 * instruction. To avoid the SMP problems that can occur when we
311 * temporarily put back the original opcode to single-step, we
312 * single-stepped a copy of the instruction. The address of this
313 * copy is p->ainsn.insn.
314 *
315 * This function prepares to return from the post-single-step
316 * breakpoint trap. In case of branch instructions, the target
317 * epc to be restored.
318 */
319static void __kprobes resume_execution(struct kprobe *p,
320 struct pt_regs *regs,
321 struct kprobe_ctlblk *kcb)
322{
323 if (insn_has_delayslot(p->opcode))
324 regs->cp0_epc = kcb->target_epc;
325 else {
326 unsigned long orig_epc = kcb->kprobe_saved_epc;
327 regs->cp0_epc = orig_epc + 4;
328 }
329}
330
331static int __kprobes kprobe_handler(struct pt_regs *regs)
332{
333 struct kprobe *p;
334 int ret = 0;
335 kprobe_opcode_t *addr;
336 struct kprobe_ctlblk *kcb;
337
338 addr = (kprobe_opcode_t *) regs->cp0_epc;
339
340 /*
341 * We don't want to be preempted for the entire
342 * duration of kprobe processing
343 */
344 preempt_disable();
345 kcb = get_kprobe_ctlblk();
346
347 /* Check we're not actually recursing */
348 if (kprobe_running()) {
349 p = get_kprobe(addr);
350 if (p) {
351 if (kcb->kprobe_status == KPROBE_HIT_SS &&
352 p->ainsn.insn->word == breakpoint_insn.word) {
353 regs->cp0_status &= ~ST0_IE;
354 regs->cp0_status |= kcb->kprobe_saved_SR;
355 goto no_kprobe;
356 }
357 /*
358 * We have reentered the kprobe_handler(), since
359 * another probe was hit while within the handler.
360 * We here save the original kprobes variables and
361 * just single step on the instruction of the new probe
362 * without calling any user handlers.
363 */
364 save_previous_kprobe(kcb);
365 set_current_kprobe(p, regs, kcb);
366 kprobes_inc_nmissed_count(p);
367 prepare_singlestep(p, regs, kcb);
368 kcb->kprobe_status = KPROBE_REENTER;
369 if (kcb->flags & SKIP_DELAYSLOT) {
370 resume_execution(p, regs, kcb);
371 restore_previous_kprobe(kcb);
372 preempt_enable_no_resched();
373 }
374 return 1;
375 } else {
376 if (addr->word != breakpoint_insn.word) {
377 /*
378 * The breakpoint instruction was removed by
379 * another cpu right after we hit, no further
380 * handling of this interrupt is appropriate
381 */
382 ret = 1;
383 goto no_kprobe;
384 }
385 p = __get_cpu_var(current_kprobe);
386 if (p->break_handler && p->break_handler(p, regs))
387 goto ss_probe;
388 }
389 goto no_kprobe;
390 }
391
392 p = get_kprobe(addr);
393 if (!p) {
394 if (addr->word != breakpoint_insn.word) {
395 /*
396 * The breakpoint instruction was removed right
397 * after we hit it. Another cpu has removed
398 * either a probepoint or a debugger breakpoint
399 * at this address. In either case, no further
400 * handling of this interrupt is appropriate.
401 */
402 ret = 1;
403 }
404 /* Not one of ours: let kernel handle it */
405 goto no_kprobe;
406 }
407
408 set_current_kprobe(p, regs, kcb);
409 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
410
411 if (p->pre_handler && p->pre_handler(p, regs)) {
412 /* handler has already set things up, so skip ss setup */
413 return 1;
414 }
415
416ss_probe:
417 prepare_singlestep(p, regs, kcb);
418 if (kcb->flags & SKIP_DELAYSLOT) {
419 kcb->kprobe_status = KPROBE_HIT_SSDONE;
420 if (p->post_handler)
421 p->post_handler(p, regs, 0);
422 resume_execution(p, regs, kcb);
423 preempt_enable_no_resched();
424 } else
425 kcb->kprobe_status = KPROBE_HIT_SS;
426
427 return 1;
428
429no_kprobe:
430 preempt_enable_no_resched();
431 return ret;
432
433}
434
435static inline int post_kprobe_handler(struct pt_regs *regs)
436{
437 struct kprobe *cur = kprobe_running();
438 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
439
440 if (!cur)
441 return 0;
442
443 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
444 kcb->kprobe_status = KPROBE_HIT_SSDONE;
445 cur->post_handler(cur, regs, 0);
446 }
447
448 resume_execution(cur, regs, kcb);
449
450 regs->cp0_status |= kcb->kprobe_saved_SR;
451
452 /* Restore back the original saved kprobes variables and continue. */
453 if (kcb->kprobe_status == KPROBE_REENTER) {
454 restore_previous_kprobe(kcb);
455 goto out;
456 }
457 reset_current_kprobe();
458out:
459 preempt_enable_no_resched();
460
461 return 1;
462}
463
464static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
465{
466 struct kprobe *cur = kprobe_running();
467 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
468
469 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
470 return 1;
471
472 if (kcb->kprobe_status & KPROBE_HIT_SS) {
473 resume_execution(cur, regs, kcb);
474 regs->cp0_status |= kcb->kprobe_old_SR;
475
476 reset_current_kprobe();
477 preempt_enable_no_resched();
478 }
479 return 0;
480}
481
482/*
483 * Wrapper routine for handling exceptions.
484 */
485int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
486 unsigned long val, void *data)
487{
488
489 struct die_args *args = (struct die_args *)data;
490 int ret = NOTIFY_DONE;
491
492 switch (val) {
493 case DIE_BREAK:
494 if (kprobe_handler(args->regs))
495 ret = NOTIFY_STOP;
496 break;
497 case DIE_SSTEPBP:
498 if (post_kprobe_handler(args->regs))
499 ret = NOTIFY_STOP;
500 break;
501
502 case DIE_PAGE_FAULT:
503 /* kprobe_running() needs smp_processor_id() */
504 preempt_disable();
505
506 if (kprobe_running()
507 && kprobe_fault_handler(args->regs, args->trapnr))
508 ret = NOTIFY_STOP;
509 preempt_enable();
510 break;
511 default:
512 break;
513 }
514 return ret;
515}
516
517int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
518{
519 struct jprobe *jp = container_of(p, struct jprobe, kp);
520 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
521
522 kcb->jprobe_saved_regs = *regs;
523 kcb->jprobe_saved_sp = regs->regs[29];
524
525 memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp,
526 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
527
528 regs->cp0_epc = (unsigned long)(jp->entry);
529
530 return 1;
531}
532
533/* Defined in the inline asm below. */
534void jprobe_return_end(void);
535
536void __kprobes jprobe_return(void)
537{
538 /* Assembler quirk necessitates this '0,code' business. */
539 asm volatile(
540 "break 0,%0\n\t"
541 ".globl jprobe_return_end\n"
542 "jprobe_return_end:\n"
543 : : "n" (BRK_KPROBE_BP) : "memory");
544}
545
546int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
547{
548 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
549
550 if (regs->cp0_epc >= (unsigned long)jprobe_return &&
551 regs->cp0_epc <= (unsigned long)jprobe_return_end) {
552 *regs = kcb->jprobe_saved_regs;
553 memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack,
554 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
555 preempt_enable_no_resched();
556
557 return 1;
558 }
559 return 0;
560}
561
562/*
563 * Function return probe trampoline:
564 * - init_kprobes() establishes a probepoint here
565 * - When the probed function returns, this probe causes the
566 * handlers to fire
567 */
568static void __used kretprobe_trampoline_holder(void)
569{
570 asm volatile(
571 ".set push\n\t"
572 /* Keep the assembler from reordering and placing JR here. */
573 ".set noreorder\n\t"
574 "nop\n\t"
575 ".global kretprobe_trampoline\n"
576 "kretprobe_trampoline:\n\t"
577 "nop\n\t"
578 ".set pop"
579 : : : "memory");
580}
581
582void kretprobe_trampoline(void);
583
584void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
585 struct pt_regs *regs)
586{
587 ri->ret_addr = (kprobe_opcode_t *) regs->regs[31];
588
589 /* Replace the return addr with trampoline addr */
590 regs->regs[31] = (unsigned long)kretprobe_trampoline;
591}
592
593/*
594 * Called when the probe at kretprobe trampoline is hit
595 */
596static int __kprobes trampoline_probe_handler(struct kprobe *p,
597 struct pt_regs *regs)
598{
599 struct kretprobe_instance *ri = NULL;
600 struct hlist_head *head, empty_rp;
601 struct hlist_node *node, *tmp;
602 unsigned long flags, orig_ret_address = 0;
603 unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
604
605 INIT_HLIST_HEAD(&empty_rp);
606 kretprobe_hash_lock(current, &head, &flags);
607
608 /*
609 * It is possible to have multiple instances associated with a given
610 * task either because an multiple functions in the call path
611 * have a return probe installed on them, and/or more than one return
612 * return probe was registered for a target function.
613 *
614 * We can handle this because:
615 * - instances are always inserted at the head of the list
616 * - when multiple return probes are registered for the same
617 * function, the first instance's ret_addr will point to the
618 * real return address, and all the rest will point to
619 * kretprobe_trampoline
620 */
621 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
622 if (ri->task != current)
623 /* another task is sharing our hash bucket */
624 continue;
625
626 if (ri->rp && ri->rp->handler)
627 ri->rp->handler(ri, regs);
628
629 orig_ret_address = (unsigned long)ri->ret_addr;
630 recycle_rp_inst(ri, &empty_rp);
631
632 if (orig_ret_address != trampoline_address)
633 /*
634 * This is the real return address. Any other
635 * instances associated with this task are for
636 * other calls deeper on the call stack
637 */
638 break;
639 }
640
641 kretprobe_assert(ri, orig_ret_address, trampoline_address);
642 instruction_pointer(regs) = orig_ret_address;
643
644 reset_current_kprobe();
645 kretprobe_hash_unlock(current, &flags);
646 preempt_enable_no_resched();
647
648 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
649 hlist_del(&ri->hlist);
650 kfree(ri);
651 }
652 /*
653 * By returning a non-zero value, we are telling
654 * kprobe_handler() that we don't want the post_handler
655 * to run (and have re-enabled preemption)
656 */
657 return 1;
658}
659
660int __kprobes arch_trampoline_kprobe(struct kprobe *p)
661{
662 if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline)
663 return 1;
664
665 return 0;
666}
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}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Kernel Probes (KProbes)
4 * arch/mips/kernel/kprobes.c
5 *
6 * Copyright 2006 Sony Corp.
7 * Copyright 2010 Cavium Networks
8 *
9 * Some portions copied from the powerpc version.
10 *
11 * Copyright (C) IBM Corporation, 2002, 2004
12 */
13
14#include <linux/kprobes.h>
15#include <linux/preempt.h>
16#include <linux/uaccess.h>
17#include <linux/kdebug.h>
18#include <linux/slab.h>
19
20#include <asm/ptrace.h>
21#include <asm/branch.h>
22#include <asm/break.h>
23
24#include "probes-common.h"
25
26static const union mips_instruction breakpoint_insn = {
27 .b_format = {
28 .opcode = spec_op,
29 .code = BRK_KPROBE_BP,
30 .func = break_op
31 }
32};
33
34static const union mips_instruction breakpoint2_insn = {
35 .b_format = {
36 .opcode = spec_op,
37 .code = BRK_KPROBE_SSTEPBP,
38 .func = break_op
39 }
40};
41
42DEFINE_PER_CPU(struct kprobe *, current_kprobe);
43DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
44
45static int __kprobes insn_has_delayslot(union mips_instruction insn)
46{
47 return __insn_has_delay_slot(insn);
48}
49
50/*
51 * insn_has_ll_or_sc function checks whether instruction is ll or sc
52 * one; putting breakpoint on top of atomic ll/sc pair is bad idea;
53 * so we need to prevent it and refuse kprobes insertion for such
54 * instructions; cannot do much about breakpoint in the middle of
55 * ll/sc pair; it is upto user to avoid those places
56 */
57static int __kprobes insn_has_ll_or_sc(union mips_instruction insn)
58{
59 int ret = 0;
60
61 switch (insn.i_format.opcode) {
62 case ll_op:
63 case lld_op:
64 case sc_op:
65 case scd_op:
66 ret = 1;
67 break;
68 default:
69 break;
70 }
71 return ret;
72}
73
74int __kprobes arch_prepare_kprobe(struct kprobe *p)
75{
76 union mips_instruction insn;
77 union mips_instruction prev_insn;
78 int ret = 0;
79
80 insn = p->addr[0];
81
82 if (insn_has_ll_or_sc(insn)) {
83 pr_notice("Kprobes for ll and sc instructions are not"
84 "supported\n");
85 ret = -EINVAL;
86 goto out;
87 }
88
89 if ((probe_kernel_read(&prev_insn, p->addr - 1,
90 sizeof(mips_instruction)) == 0) &&
91 insn_has_delayslot(prev_insn)) {
92 pr_notice("Kprobes for branch delayslot are not supported\n");
93 ret = -EINVAL;
94 goto out;
95 }
96
97 if (__insn_is_compact_branch(insn)) {
98 pr_notice("Kprobes for compact branches are not supported\n");
99 ret = -EINVAL;
100 goto out;
101 }
102
103 /* insn: must be on special executable page on mips. */
104 p->ainsn.insn = get_insn_slot();
105 if (!p->ainsn.insn) {
106 ret = -ENOMEM;
107 goto out;
108 }
109
110 /*
111 * In the kprobe->ainsn.insn[] array we store the original
112 * instruction at index zero and a break trap instruction at
113 * index one.
114 *
115 * On MIPS arch if the instruction at probed address is a
116 * branch instruction, we need to execute the instruction at
117 * Branch Delayslot (BD) at the time of probe hit. As MIPS also
118 * doesn't have single stepping support, the BD instruction can
119 * not be executed in-line and it would be executed on SSOL slot
120 * using a normal breakpoint instruction in the next slot.
121 * So, read the instruction and save it for later execution.
122 */
123 if (insn_has_delayslot(insn))
124 memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t));
125 else
126 memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
127
128 p->ainsn.insn[1] = breakpoint2_insn;
129 p->opcode = *p->addr;
130
131out:
132 return ret;
133}
134
135void __kprobes arch_arm_kprobe(struct kprobe *p)
136{
137 *p->addr = breakpoint_insn;
138 flush_insn_slot(p);
139}
140
141void __kprobes arch_disarm_kprobe(struct kprobe *p)
142{
143 *p->addr = p->opcode;
144 flush_insn_slot(p);
145}
146
147void __kprobes arch_remove_kprobe(struct kprobe *p)
148{
149 if (p->ainsn.insn) {
150 free_insn_slot(p->ainsn.insn, 0);
151 p->ainsn.insn = NULL;
152 }
153}
154
155static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
156{
157 kcb->prev_kprobe.kp = kprobe_running();
158 kcb->prev_kprobe.status = kcb->kprobe_status;
159 kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR;
160 kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR;
161 kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc;
162}
163
164static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
165{
166 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
167 kcb->kprobe_status = kcb->prev_kprobe.status;
168 kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR;
169 kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR;
170 kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc;
171}
172
173static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
174 struct kprobe_ctlblk *kcb)
175{
176 __this_cpu_write(current_kprobe, p);
177 kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE);
178 kcb->kprobe_saved_epc = regs->cp0_epc;
179}
180
181/**
182 * evaluate_branch_instrucion -
183 *
184 * Evaluate the branch instruction at probed address during probe hit. The
185 * result of evaluation would be the updated epc. The insturction in delayslot
186 * would actually be single stepped using a normal breakpoint) on SSOL slot.
187 *
188 * The result is also saved in the kprobe control block for later use,
189 * in case we need to execute the delayslot instruction. The latter will be
190 * false for NOP instruction in dealyslot and the branch-likely instructions
191 * when the branch is taken. And for those cases we set a flag as
192 * SKIP_DELAYSLOT in the kprobe control block
193 */
194static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs,
195 struct kprobe_ctlblk *kcb)
196{
197 union mips_instruction insn = p->opcode;
198 long epc;
199 int ret = 0;
200
201 epc = regs->cp0_epc;
202 if (epc & 3)
203 goto unaligned;
204
205 if (p->ainsn.insn->word == 0)
206 kcb->flags |= SKIP_DELAYSLOT;
207 else
208 kcb->flags &= ~SKIP_DELAYSLOT;
209
210 ret = __compute_return_epc_for_insn(regs, insn);
211 if (ret < 0)
212 return ret;
213
214 if (ret == BRANCH_LIKELY_TAKEN)
215 kcb->flags |= SKIP_DELAYSLOT;
216
217 kcb->target_epc = regs->cp0_epc;
218
219 return 0;
220
221unaligned:
222 pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm);
223 force_sig(SIGBUS);
224 return -EFAULT;
225
226}
227
228static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
229 struct kprobe_ctlblk *kcb)
230{
231 int ret = 0;
232
233 regs->cp0_status &= ~ST0_IE;
234
235 /* single step inline if the instruction is a break */
236 if (p->opcode.word == breakpoint_insn.word ||
237 p->opcode.word == breakpoint2_insn.word)
238 regs->cp0_epc = (unsigned long)p->addr;
239 else if (insn_has_delayslot(p->opcode)) {
240 ret = evaluate_branch_instruction(p, regs, kcb);
241 if (ret < 0) {
242 pr_notice("Kprobes: Error in evaluating branch\n");
243 return;
244 }
245 }
246 regs->cp0_epc = (unsigned long)&p->ainsn.insn[0];
247}
248
249/*
250 * Called after single-stepping. p->addr is the address of the
251 * instruction whose first byte has been replaced by the "break 0"
252 * instruction. To avoid the SMP problems that can occur when we
253 * temporarily put back the original opcode to single-step, we
254 * single-stepped a copy of the instruction. The address of this
255 * copy is p->ainsn.insn.
256 *
257 * This function prepares to return from the post-single-step
258 * breakpoint trap. In case of branch instructions, the target
259 * epc to be restored.
260 */
261static void __kprobes resume_execution(struct kprobe *p,
262 struct pt_regs *regs,
263 struct kprobe_ctlblk *kcb)
264{
265 if (insn_has_delayslot(p->opcode))
266 regs->cp0_epc = kcb->target_epc;
267 else {
268 unsigned long orig_epc = kcb->kprobe_saved_epc;
269 regs->cp0_epc = orig_epc + 4;
270 }
271}
272
273static int __kprobes kprobe_handler(struct pt_regs *regs)
274{
275 struct kprobe *p;
276 int ret = 0;
277 kprobe_opcode_t *addr;
278 struct kprobe_ctlblk *kcb;
279
280 addr = (kprobe_opcode_t *) regs->cp0_epc;
281
282 /*
283 * We don't want to be preempted for the entire
284 * duration of kprobe processing
285 */
286 preempt_disable();
287 kcb = get_kprobe_ctlblk();
288
289 /* Check we're not actually recursing */
290 if (kprobe_running()) {
291 p = get_kprobe(addr);
292 if (p) {
293 if (kcb->kprobe_status == KPROBE_HIT_SS &&
294 p->ainsn.insn->word == breakpoint_insn.word) {
295 regs->cp0_status &= ~ST0_IE;
296 regs->cp0_status |= kcb->kprobe_saved_SR;
297 goto no_kprobe;
298 }
299 /*
300 * We have reentered the kprobe_handler(), since
301 * another probe was hit while within the handler.
302 * We here save the original kprobes variables and
303 * just single step on the instruction of the new probe
304 * without calling any user handlers.
305 */
306 save_previous_kprobe(kcb);
307 set_current_kprobe(p, regs, kcb);
308 kprobes_inc_nmissed_count(p);
309 prepare_singlestep(p, regs, kcb);
310 kcb->kprobe_status = KPROBE_REENTER;
311 if (kcb->flags & SKIP_DELAYSLOT) {
312 resume_execution(p, regs, kcb);
313 restore_previous_kprobe(kcb);
314 preempt_enable_no_resched();
315 }
316 return 1;
317 } else if (addr->word != breakpoint_insn.word) {
318 /*
319 * The breakpoint instruction was removed by
320 * another cpu right after we hit, no further
321 * handling of this interrupt is appropriate
322 */
323 ret = 1;
324 }
325 goto no_kprobe;
326 }
327
328 p = get_kprobe(addr);
329 if (!p) {
330 if (addr->word != breakpoint_insn.word) {
331 /*
332 * The breakpoint instruction was removed right
333 * after we hit it. Another cpu has removed
334 * either a probepoint or a debugger breakpoint
335 * at this address. In either case, no further
336 * handling of this interrupt is appropriate.
337 */
338 ret = 1;
339 }
340 /* Not one of ours: let kernel handle it */
341 goto no_kprobe;
342 }
343
344 set_current_kprobe(p, regs, kcb);
345 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
346
347 if (p->pre_handler && p->pre_handler(p, regs)) {
348 /* handler has already set things up, so skip ss setup */
349 reset_current_kprobe();
350 preempt_enable_no_resched();
351 return 1;
352 }
353
354 prepare_singlestep(p, regs, kcb);
355 if (kcb->flags & SKIP_DELAYSLOT) {
356 kcb->kprobe_status = KPROBE_HIT_SSDONE;
357 if (p->post_handler)
358 p->post_handler(p, regs, 0);
359 resume_execution(p, regs, kcb);
360 preempt_enable_no_resched();
361 } else
362 kcb->kprobe_status = KPROBE_HIT_SS;
363
364 return 1;
365
366no_kprobe:
367 preempt_enable_no_resched();
368 return ret;
369
370}
371
372static inline int post_kprobe_handler(struct pt_regs *regs)
373{
374 struct kprobe *cur = kprobe_running();
375 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
376
377 if (!cur)
378 return 0;
379
380 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
381 kcb->kprobe_status = KPROBE_HIT_SSDONE;
382 cur->post_handler(cur, regs, 0);
383 }
384
385 resume_execution(cur, regs, kcb);
386
387 regs->cp0_status |= kcb->kprobe_saved_SR;
388
389 /* Restore back the original saved kprobes variables and continue. */
390 if (kcb->kprobe_status == KPROBE_REENTER) {
391 restore_previous_kprobe(kcb);
392 goto out;
393 }
394 reset_current_kprobe();
395out:
396 preempt_enable_no_resched();
397
398 return 1;
399}
400
401int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
402{
403 struct kprobe *cur = kprobe_running();
404 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
405
406 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
407 return 1;
408
409 if (kcb->kprobe_status & KPROBE_HIT_SS) {
410 resume_execution(cur, regs, kcb);
411 regs->cp0_status |= kcb->kprobe_old_SR;
412
413 reset_current_kprobe();
414 preempt_enable_no_resched();
415 }
416 return 0;
417}
418
419/*
420 * Wrapper routine for handling exceptions.
421 */
422int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
423 unsigned long val, void *data)
424{
425
426 struct die_args *args = (struct die_args *)data;
427 int ret = NOTIFY_DONE;
428
429 switch (val) {
430 case DIE_BREAK:
431 if (kprobe_handler(args->regs))
432 ret = NOTIFY_STOP;
433 break;
434 case DIE_SSTEPBP:
435 if (post_kprobe_handler(args->regs))
436 ret = NOTIFY_STOP;
437 break;
438
439 case DIE_PAGE_FAULT:
440 /* kprobe_running() needs smp_processor_id() */
441 preempt_disable();
442
443 if (kprobe_running()
444 && kprobe_fault_handler(args->regs, args->trapnr))
445 ret = NOTIFY_STOP;
446 preempt_enable();
447 break;
448 default:
449 break;
450 }
451 return ret;
452}
453
454/*
455 * Function return probe trampoline:
456 * - init_kprobes() establishes a probepoint here
457 * - When the probed function returns, this probe causes the
458 * handlers to fire
459 */
460static void __used kretprobe_trampoline_holder(void)
461{
462 asm volatile(
463 ".set push\n\t"
464 /* Keep the assembler from reordering and placing JR here. */
465 ".set noreorder\n\t"
466 "nop\n\t"
467 ".global kretprobe_trampoline\n"
468 "kretprobe_trampoline:\n\t"
469 "nop\n\t"
470 ".set pop"
471 : : : "memory");
472}
473
474void kretprobe_trampoline(void);
475
476void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
477 struct pt_regs *regs)
478{
479 ri->ret_addr = (kprobe_opcode_t *) regs->regs[31];
480
481 /* Replace the return addr with trampoline addr */
482 regs->regs[31] = (unsigned long)kretprobe_trampoline;
483}
484
485/*
486 * Called when the probe at kretprobe trampoline is hit
487 */
488static int __kprobes trampoline_probe_handler(struct kprobe *p,
489 struct pt_regs *regs)
490{
491 struct kretprobe_instance *ri = NULL;
492 struct hlist_head *head, empty_rp;
493 struct hlist_node *tmp;
494 unsigned long flags, orig_ret_address = 0;
495 unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
496
497 INIT_HLIST_HEAD(&empty_rp);
498 kretprobe_hash_lock(current, &head, &flags);
499
500 /*
501 * It is possible to have multiple instances associated with a given
502 * task either because an multiple functions in the call path
503 * have a return probe installed on them, and/or more than one return
504 * return probe was registered for a target function.
505 *
506 * We can handle this because:
507 * - instances are always inserted at the head of the list
508 * - when multiple return probes are registered for the same
509 * function, the first instance's ret_addr will point to the
510 * real return address, and all the rest will point to
511 * kretprobe_trampoline
512 */
513 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
514 if (ri->task != current)
515 /* another task is sharing our hash bucket */
516 continue;
517
518 if (ri->rp && ri->rp->handler)
519 ri->rp->handler(ri, regs);
520
521 orig_ret_address = (unsigned long)ri->ret_addr;
522 recycle_rp_inst(ri, &empty_rp);
523
524 if (orig_ret_address != trampoline_address)
525 /*
526 * This is the real return address. Any other
527 * instances associated with this task are for
528 * other calls deeper on the call stack
529 */
530 break;
531 }
532
533 kretprobe_assert(ri, orig_ret_address, trampoline_address);
534 instruction_pointer(regs) = orig_ret_address;
535
536 kretprobe_hash_unlock(current, &flags);
537
538 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
539 hlist_del(&ri->hlist);
540 kfree(ri);
541 }
542 /*
543 * By returning a non-zero value, we are telling
544 * kprobe_handler() that we don't want the post_handler
545 * to run (and have re-enabled preemption)
546 */
547 return 1;
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}
557
558static struct kprobe trampoline_p = {
559 .addr = (kprobe_opcode_t *)kretprobe_trampoline,
560 .pre_handler = trampoline_probe_handler
561};
562
563int __init arch_init_kprobes(void)
564{
565 return register_kprobe(&trampoline_p);
566}