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