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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/*
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/kdebug.h>
29#include <linux/slab.h>
30
31#include <asm/ptrace.h>
32#include <asm/break.h>
33#include <asm/inst.h>
34
35static const union mips_instruction breakpoint_insn = {
36 .b_format = {
37 .opcode = spec_op,
38 .code = BRK_KPROBE_BP,
39 .func = break_op
40 }
41};
42
43static const union mips_instruction breakpoint2_insn = {
44 .b_format = {
45 .opcode = spec_op,
46 .code = BRK_KPROBE_SSTEPBP,
47 .func = break_op
48 }
49};
50
51DEFINE_PER_CPU(struct kprobe *, current_kprobe);
52DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
53
54static int __kprobes insn_has_delayslot(union mips_instruction insn)
55{
56 switch (insn.i_format.opcode) {
57
58 /*
59 * This group contains:
60 * jr and jalr are in r_format format.
61 */
62 case spec_op:
63 switch (insn.r_format.func) {
64 case jr_op:
65 case jalr_op:
66 break;
67 default:
68 goto insn_ok;
69 }
70
71 /*
72 * This group contains:
73 * bltz_op, bgez_op, bltzl_op, bgezl_op,
74 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
75 */
76 case bcond_op:
77
78 /*
79 * These are unconditional and in j_format.
80 */
81 case jal_op:
82 case j_op:
83
84 /*
85 * These are conditional and in i_format.
86 */
87 case beq_op:
88 case beql_op:
89 case bne_op:
90 case bnel_op:
91 case blez_op:
92 case blezl_op:
93 case bgtz_op:
94 case bgtzl_op:
95
96 /*
97 * These are the FPA/cp1 branch instructions.
98 */
99 case cop1_op:
100
101#ifdef CONFIG_CPU_CAVIUM_OCTEON
102 case lwc2_op: /* This is bbit0 on Octeon */
103 case ldc2_op: /* This is bbit032 on Octeon */
104 case swc2_op: /* This is bbit1 on Octeon */
105 case sdc2_op: /* This is bbit132 on Octeon */
106#endif
107 return 1;
108 default:
109 break;
110 }
111insn_ok:
112 return 0;
113}
114
115int __kprobes arch_prepare_kprobe(struct kprobe *p)
116{
117 union mips_instruction insn;
118 union mips_instruction prev_insn;
119 int ret = 0;
120
121 prev_insn = p->addr[-1];
122 insn = p->addr[0];
123
124 if (insn_has_delayslot(insn) || insn_has_delayslot(prev_insn)) {
125 pr_notice("Kprobes for branch and jump instructions are not supported\n");
126 ret = -EINVAL;
127 goto out;
128 }
129
130 /* insn: must be on special executable page on mips. */
131 p->ainsn.insn = get_insn_slot();
132 if (!p->ainsn.insn) {
133 ret = -ENOMEM;
134 goto out;
135 }
136
137 /*
138 * In the kprobe->ainsn.insn[] array we store the original
139 * instruction at index zero and a break trap instruction at
140 * index one.
141 */
142
143 memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
144 p->ainsn.insn[1] = breakpoint2_insn;
145 p->opcode = *p->addr;
146
147out:
148 return ret;
149}
150
151void __kprobes arch_arm_kprobe(struct kprobe *p)
152{
153 *p->addr = breakpoint_insn;
154 flush_insn_slot(p);
155}
156
157void __kprobes arch_disarm_kprobe(struct kprobe *p)
158{
159 *p->addr = p->opcode;
160 flush_insn_slot(p);
161}
162
163void __kprobes arch_remove_kprobe(struct kprobe *p)
164{
165 free_insn_slot(p->ainsn.insn, 0);
166}
167
168static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
169{
170 kcb->prev_kprobe.kp = kprobe_running();
171 kcb->prev_kprobe.status = kcb->kprobe_status;
172 kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR;
173 kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR;
174 kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc;
175}
176
177static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
178{
179 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
180 kcb->kprobe_status = kcb->prev_kprobe.status;
181 kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR;
182 kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR;
183 kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc;
184}
185
186static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
187 struct kprobe_ctlblk *kcb)
188{
189 __get_cpu_var(current_kprobe) = p;
190 kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE);
191 kcb->kprobe_saved_epc = regs->cp0_epc;
192}
193
194static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
195{
196 regs->cp0_status &= ~ST0_IE;
197
198 /* single step inline if the instruction is a break */
199 if (p->opcode.word == breakpoint_insn.word ||
200 p->opcode.word == breakpoint2_insn.word)
201 regs->cp0_epc = (unsigned long)p->addr;
202 else
203 regs->cp0_epc = (unsigned long)&p->ainsn.insn[0];
204}
205
206static int __kprobes kprobe_handler(struct pt_regs *regs)
207{
208 struct kprobe *p;
209 int ret = 0;
210 kprobe_opcode_t *addr;
211 struct kprobe_ctlblk *kcb;
212
213 addr = (kprobe_opcode_t *) regs->cp0_epc;
214
215 /*
216 * We don't want to be preempted for the entire
217 * duration of kprobe processing
218 */
219 preempt_disable();
220 kcb = get_kprobe_ctlblk();
221
222 /* Check we're not actually recursing */
223 if (kprobe_running()) {
224 p = get_kprobe(addr);
225 if (p) {
226 if (kcb->kprobe_status == KPROBE_HIT_SS &&
227 p->ainsn.insn->word == breakpoint_insn.word) {
228 regs->cp0_status &= ~ST0_IE;
229 regs->cp0_status |= kcb->kprobe_saved_SR;
230 goto no_kprobe;
231 }
232 /*
233 * We have reentered the kprobe_handler(), since
234 * another probe was hit while within the handler.
235 * We here save the original kprobes variables and
236 * just single step on the instruction of the new probe
237 * without calling any user handlers.
238 */
239 save_previous_kprobe(kcb);
240 set_current_kprobe(p, regs, kcb);
241 kprobes_inc_nmissed_count(p);
242 prepare_singlestep(p, regs);
243 kcb->kprobe_status = KPROBE_REENTER;
244 return 1;
245 } else {
246 if (addr->word != breakpoint_insn.word) {
247 /*
248 * The breakpoint instruction was removed by
249 * another cpu right after we hit, no further
250 * handling of this interrupt is appropriate
251 */
252 ret = 1;
253 goto no_kprobe;
254 }
255 p = __get_cpu_var(current_kprobe);
256 if (p->break_handler && p->break_handler(p, regs))
257 goto ss_probe;
258 }
259 goto no_kprobe;
260 }
261
262 p = get_kprobe(addr);
263 if (!p) {
264 if (addr->word != breakpoint_insn.word) {
265 /*
266 * The breakpoint instruction was removed right
267 * after we hit it. Another cpu has removed
268 * either a probepoint or a debugger breakpoint
269 * at this address. In either case, no further
270 * handling of this interrupt is appropriate.
271 */
272 ret = 1;
273 }
274 /* Not one of ours: let kernel handle it */
275 goto no_kprobe;
276 }
277
278 set_current_kprobe(p, regs, kcb);
279 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
280
281 if (p->pre_handler && p->pre_handler(p, regs)) {
282 /* handler has already set things up, so skip ss setup */
283 return 1;
284 }
285
286ss_probe:
287 prepare_singlestep(p, regs);
288 kcb->kprobe_status = KPROBE_HIT_SS;
289 return 1;
290
291no_kprobe:
292 preempt_enable_no_resched();
293 return ret;
294
295}
296
297/*
298 * Called after single-stepping. p->addr is the address of the
299 * instruction whose first byte has been replaced by the "break 0"
300 * instruction. To avoid the SMP problems that can occur when we
301 * temporarily put back the original opcode to single-step, we
302 * single-stepped a copy of the instruction. The address of this
303 * copy is p->ainsn.insn.
304 *
305 * This function prepares to return from the post-single-step
306 * breakpoint trap.
307 */
308static void __kprobes resume_execution(struct kprobe *p,
309 struct pt_regs *regs,
310 struct kprobe_ctlblk *kcb)
311{
312 unsigned long orig_epc = kcb->kprobe_saved_epc;
313 regs->cp0_epc = orig_epc + 4;
314}
315
316static inline int post_kprobe_handler(struct pt_regs *regs)
317{
318 struct kprobe *cur = kprobe_running();
319 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
320
321 if (!cur)
322 return 0;
323
324 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
325 kcb->kprobe_status = KPROBE_HIT_SSDONE;
326 cur->post_handler(cur, regs, 0);
327 }
328
329 resume_execution(cur, regs, kcb);
330
331 regs->cp0_status |= kcb->kprobe_saved_SR;
332
333 /* Restore back the original saved kprobes variables and continue. */
334 if (kcb->kprobe_status == KPROBE_REENTER) {
335 restore_previous_kprobe(kcb);
336 goto out;
337 }
338 reset_current_kprobe();
339out:
340 preempt_enable_no_resched();
341
342 return 1;
343}
344
345static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
346{
347 struct kprobe *cur = kprobe_running();
348 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
349
350 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
351 return 1;
352
353 if (kcb->kprobe_status & KPROBE_HIT_SS) {
354 resume_execution(cur, regs, kcb);
355 regs->cp0_status |= kcb->kprobe_old_SR;
356
357 reset_current_kprobe();
358 preempt_enable_no_resched();
359 }
360 return 0;
361}
362
363/*
364 * Wrapper routine for handling exceptions.
365 */
366int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
367 unsigned long val, void *data)
368{
369
370 struct die_args *args = (struct die_args *)data;
371 int ret = NOTIFY_DONE;
372
373 switch (val) {
374 case DIE_BREAK:
375 if (kprobe_handler(args->regs))
376 ret = NOTIFY_STOP;
377 break;
378 case DIE_SSTEPBP:
379 if (post_kprobe_handler(args->regs))
380 ret = NOTIFY_STOP;
381 break;
382
383 case DIE_PAGE_FAULT:
384 /* kprobe_running() needs smp_processor_id() */
385 preempt_disable();
386
387 if (kprobe_running()
388 && kprobe_fault_handler(args->regs, args->trapnr))
389 ret = NOTIFY_STOP;
390 preempt_enable();
391 break;
392 default:
393 break;
394 }
395 return ret;
396}
397
398int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
399{
400 struct jprobe *jp = container_of(p, struct jprobe, kp);
401 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
402
403 kcb->jprobe_saved_regs = *regs;
404 kcb->jprobe_saved_sp = regs->regs[29];
405
406 memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp,
407 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
408
409 regs->cp0_epc = (unsigned long)(jp->entry);
410
411 return 1;
412}
413
414/* Defined in the inline asm below. */
415void jprobe_return_end(void);
416
417void __kprobes jprobe_return(void)
418{
419 /* Assembler quirk necessitates this '0,code' business. */
420 asm volatile(
421 "break 0,%0\n\t"
422 ".globl jprobe_return_end\n"
423 "jprobe_return_end:\n"
424 : : "n" (BRK_KPROBE_BP) : "memory");
425}
426
427int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
428{
429 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
430
431 if (regs->cp0_epc >= (unsigned long)jprobe_return &&
432 regs->cp0_epc <= (unsigned long)jprobe_return_end) {
433 *regs = kcb->jprobe_saved_regs;
434 memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack,
435 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
436 preempt_enable_no_resched();
437
438 return 1;
439 }
440 return 0;
441}
442
443/*
444 * Function return probe trampoline:
445 * - init_kprobes() establishes a probepoint here
446 * - When the probed function returns, this probe causes the
447 * handlers to fire
448 */
449static void __used kretprobe_trampoline_holder(void)
450{
451 asm volatile(
452 ".set push\n\t"
453 /* Keep the assembler from reordering and placing JR here. */
454 ".set noreorder\n\t"
455 "nop\n\t"
456 ".global kretprobe_trampoline\n"
457 "kretprobe_trampoline:\n\t"
458 "nop\n\t"
459 ".set pop"
460 : : : "memory");
461}
462
463void kretprobe_trampoline(void);
464
465void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
466 struct pt_regs *regs)
467{
468 ri->ret_addr = (kprobe_opcode_t *) regs->regs[31];
469
470 /* Replace the return addr with trampoline addr */
471 regs->regs[31] = (unsigned long)kretprobe_trampoline;
472}
473
474/*
475 * Called when the probe at kretprobe trampoline is hit
476 */
477static int __kprobes trampoline_probe_handler(struct kprobe *p,
478 struct pt_regs *regs)
479{
480 struct kretprobe_instance *ri = NULL;
481 struct hlist_head *head, empty_rp;
482 struct hlist_node *node, *tmp;
483 unsigned long flags, orig_ret_address = 0;
484 unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
485
486 INIT_HLIST_HEAD(&empty_rp);
487 kretprobe_hash_lock(current, &head, &flags);
488
489 /*
490 * It is possible to have multiple instances associated with a given
491 * task either because an multiple functions in the call path
492 * have a return probe installed on them, and/or more than one return
493 * return probe was registered for a target function.
494 *
495 * We can handle this because:
496 * - instances are always inserted at the head of the list
497 * - when multiple return probes are registered for the same
498 * function, the first instance's ret_addr will point to the
499 * real return address, and all the rest will point to
500 * kretprobe_trampoline
501 */
502 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
503 if (ri->task != current)
504 /* another task is sharing our hash bucket */
505 continue;
506
507 if (ri->rp && ri->rp->handler)
508 ri->rp->handler(ri, regs);
509
510 orig_ret_address = (unsigned long)ri->ret_addr;
511 recycle_rp_inst(ri, &empty_rp);
512
513 if (orig_ret_address != trampoline_address)
514 /*
515 * This is the real return address. Any other
516 * instances associated with this task are for
517 * other calls deeper on the call stack
518 */
519 break;
520 }
521
522 kretprobe_assert(ri, orig_ret_address, trampoline_address);
523 instruction_pointer(regs) = orig_ret_address;
524
525 reset_current_kprobe();
526 kretprobe_hash_unlock(current, &flags);
527 preempt_enable_no_resched();
528
529 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
530 hlist_del(&ri->hlist);
531 kfree(ri);
532 }
533 /*
534 * By returning a non-zero value, we are telling
535 * kprobe_handler() that we don't want the post_handler
536 * to run (and have re-enabled preemption)
537 */
538 return 1;
539}
540
541int __kprobes arch_trampoline_kprobe(struct kprobe *p)
542{
543 if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline)
544 return 1;
545
546 return 0;
547}
548
549static struct kprobe trampoline_p = {
550 .addr = (kprobe_opcode_t *)kretprobe_trampoline,
551 .pre_handler = trampoline_probe_handler
552};
553
554int __init arch_init_kprobes(void)
555{
556 return register_kprobe(&trampoline_p);
557}