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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#define pr_fmt(fmt) "kprobes: " fmt
15
16#include <linux/kprobes.h>
17#include <linux/preempt.h>
18#include <linux/uaccess.h>
19#include <linux/kdebug.h>
20#include <linux/slab.h>
21
22#include <asm/ptrace.h>
23#include <asm/branch.h>
24#include <asm/break.h>
25
26#include "probes-common.h"
27
28static const union mips_instruction breakpoint_insn = {
29 .b_format = {
30 .opcode = spec_op,
31 .code = BRK_KPROBE_BP,
32 .func = break_op
33 }
34};
35
36static const union mips_instruction breakpoint2_insn = {
37 .b_format = {
38 .opcode = spec_op,
39 .code = BRK_KPROBE_SSTEPBP,
40 .func = break_op
41 }
42};
43
44DEFINE_PER_CPU(struct kprobe *, current_kprobe);
45DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
46
47static int insn_has_delayslot(union mips_instruction insn)
48{
49 return __insn_has_delay_slot(insn);
50}
51NOKPROBE_SYMBOL(insn_has_delayslot);
52
53/*
54 * insn_has_ll_or_sc function checks whether instruction is ll or sc
55 * one; putting breakpoint on top of atomic ll/sc pair is bad idea;
56 * so we need to prevent it and refuse kprobes insertion for such
57 * instructions; cannot do much about breakpoint in the middle of
58 * ll/sc pair; it is upto user to avoid those places
59 */
60static int insn_has_ll_or_sc(union mips_instruction insn)
61{
62 int ret = 0;
63
64 switch (insn.i_format.opcode) {
65 case ll_op:
66 case lld_op:
67 case sc_op:
68 case scd_op:
69 ret = 1;
70 break;
71 default:
72 break;
73 }
74 return ret;
75}
76NOKPROBE_SYMBOL(insn_has_ll_or_sc);
77
78int arch_prepare_kprobe(struct kprobe *p)
79{
80 union mips_instruction insn;
81 union mips_instruction prev_insn;
82 int ret = 0;
83
84 insn = p->addr[0];
85
86 if (insn_has_ll_or_sc(insn)) {
87 pr_notice("Kprobes for ll and sc instructions are not supported\n");
88 ret = -EINVAL;
89 goto out;
90 }
91
92 if (copy_from_kernel_nofault(&prev_insn, p->addr - 1,
93 sizeof(mips_instruction)) == 0 &&
94 insn_has_delayslot(prev_insn)) {
95 pr_notice("Kprobes for branch delayslot are not supported\n");
96 ret = -EINVAL;
97 goto out;
98 }
99
100 if (__insn_is_compact_branch(insn)) {
101 pr_notice("Kprobes for compact branches are not supported\n");
102 ret = -EINVAL;
103 goto out;
104 }
105
106 /* insn: must be on special executable page on mips. */
107 p->ainsn.insn = get_insn_slot();
108 if (!p->ainsn.insn) {
109 ret = -ENOMEM;
110 goto out;
111 }
112
113 /*
114 * In the kprobe->ainsn.insn[] array we store the original
115 * instruction at index zero and a break trap instruction at
116 * index one.
117 *
118 * On MIPS arch if the instruction at probed address is a
119 * branch instruction, we need to execute the instruction at
120 * Branch Delayslot (BD) at the time of probe hit. As MIPS also
121 * doesn't have single stepping support, the BD instruction can
122 * not be executed in-line and it would be executed on SSOL slot
123 * using a normal breakpoint instruction in the next slot.
124 * So, read the instruction and save it for later execution.
125 */
126 if (insn_has_delayslot(insn))
127 memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t));
128 else
129 memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
130
131 p->ainsn.insn[1] = breakpoint2_insn;
132 p->opcode = *p->addr;
133
134out:
135 return ret;
136}
137NOKPROBE_SYMBOL(arch_prepare_kprobe);
138
139void arch_arm_kprobe(struct kprobe *p)
140{
141 *p->addr = breakpoint_insn;
142 flush_insn_slot(p);
143}
144NOKPROBE_SYMBOL(arch_arm_kprobe);
145
146void arch_disarm_kprobe(struct kprobe *p)
147{
148 *p->addr = p->opcode;
149 flush_insn_slot(p);
150}
151NOKPROBE_SYMBOL(arch_disarm_kprobe);
152
153void arch_remove_kprobe(struct kprobe *p)
154{
155 if (p->ainsn.insn) {
156 free_insn_slot(p->ainsn.insn, 0);
157 p->ainsn.insn = NULL;
158 }
159}
160NOKPROBE_SYMBOL(arch_remove_kprobe);
161
162static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
163{
164 kcb->prev_kprobe.kp = kprobe_running();
165 kcb->prev_kprobe.status = kcb->kprobe_status;
166 kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR;
167 kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR;
168 kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc;
169}
170
171static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
172{
173 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
174 kcb->kprobe_status = kcb->prev_kprobe.status;
175 kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR;
176 kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR;
177 kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc;
178}
179
180static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
181 struct kprobe_ctlblk *kcb)
182{
183 __this_cpu_write(current_kprobe, p);
184 kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE);
185 kcb->kprobe_saved_epc = regs->cp0_epc;
186}
187
188/**
189 * evaluate_branch_instrucion -
190 *
191 * Evaluate the branch instruction at probed address during probe hit. The
192 * result of evaluation would be the updated epc. The insturction in delayslot
193 * would actually be single stepped using a normal breakpoint) on SSOL slot.
194 *
195 * The result is also saved in the kprobe control block for later use,
196 * in case we need to execute the delayslot instruction. The latter will be
197 * false for NOP instruction in dealyslot and the branch-likely instructions
198 * when the branch is taken. And for those cases we set a flag as
199 * SKIP_DELAYSLOT in the kprobe control block
200 */
201static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs,
202 struct kprobe_ctlblk *kcb)
203{
204 union mips_instruction insn = p->opcode;
205 long epc;
206 int ret = 0;
207
208 epc = regs->cp0_epc;
209 if (epc & 3)
210 goto unaligned;
211
212 if (p->ainsn.insn->word == 0)
213 kcb->flags |= SKIP_DELAYSLOT;
214 else
215 kcb->flags &= ~SKIP_DELAYSLOT;
216
217 ret = __compute_return_epc_for_insn(regs, insn);
218 if (ret < 0)
219 return ret;
220
221 if (ret == BRANCH_LIKELY_TAKEN)
222 kcb->flags |= SKIP_DELAYSLOT;
223
224 kcb->target_epc = regs->cp0_epc;
225
226 return 0;
227
228unaligned:
229 pr_notice("Failed to emulate branch instruction because of unaligned epc - sending SIGBUS to %s.\n", current->comm);
230 force_sig(SIGBUS);
231 return -EFAULT;
232
233}
234
235static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
236 struct kprobe_ctlblk *kcb)
237{
238 int ret = 0;
239
240 regs->cp0_status &= ~ST0_IE;
241
242 /* single step inline if the instruction is a break */
243 if (p->opcode.word == breakpoint_insn.word ||
244 p->opcode.word == breakpoint2_insn.word)
245 regs->cp0_epc = (unsigned long)p->addr;
246 else if (insn_has_delayslot(p->opcode)) {
247 ret = evaluate_branch_instruction(p, regs, kcb);
248 if (ret < 0)
249 return;
250 }
251 regs->cp0_epc = (unsigned long)&p->ainsn.insn[0];
252}
253
254/*
255 * Called after single-stepping. p->addr is the address of the
256 * instruction whose first byte has been replaced by the "break 0"
257 * instruction. To avoid the SMP problems that can occur when we
258 * temporarily put back the original opcode to single-step, we
259 * single-stepped a copy of the instruction. The address of this
260 * copy is p->ainsn.insn.
261 *
262 * This function prepares to return from the post-single-step
263 * breakpoint trap. In case of branch instructions, the target
264 * epc to be restored.
265 */
266static void resume_execution(struct kprobe *p,
267 struct pt_regs *regs,
268 struct kprobe_ctlblk *kcb)
269{
270 if (insn_has_delayslot(p->opcode))
271 regs->cp0_epc = kcb->target_epc;
272 else {
273 unsigned long orig_epc = kcb->kprobe_saved_epc;
274 regs->cp0_epc = orig_epc + 4;
275 }
276}
277NOKPROBE_SYMBOL(resume_execution);
278
279static int kprobe_handler(struct pt_regs *regs)
280{
281 struct kprobe *p;
282 int ret = 0;
283 kprobe_opcode_t *addr;
284 struct kprobe_ctlblk *kcb;
285
286 addr = (kprobe_opcode_t *) regs->cp0_epc;
287
288 /*
289 * We don't want to be preempted for the entire
290 * duration of kprobe processing
291 */
292 preempt_disable();
293 kcb = get_kprobe_ctlblk();
294
295 /* Check we're not actually recursing */
296 if (kprobe_running()) {
297 p = get_kprobe(addr);
298 if (p) {
299 if (kcb->kprobe_status == KPROBE_HIT_SS &&
300 p->ainsn.insn->word == breakpoint_insn.word) {
301 regs->cp0_status &= ~ST0_IE;
302 regs->cp0_status |= kcb->kprobe_saved_SR;
303 goto no_kprobe;
304 }
305 /*
306 * We have reentered the kprobe_handler(), since
307 * another probe was hit while within the handler.
308 * We here save the original kprobes variables and
309 * just single step on the instruction of the new probe
310 * without calling any user handlers.
311 */
312 save_previous_kprobe(kcb);
313 set_current_kprobe(p, regs, kcb);
314 kprobes_inc_nmissed_count(p);
315 prepare_singlestep(p, regs, kcb);
316 kcb->kprobe_status = KPROBE_REENTER;
317 if (kcb->flags & SKIP_DELAYSLOT) {
318 resume_execution(p, regs, kcb);
319 restore_previous_kprobe(kcb);
320 preempt_enable_no_resched();
321 }
322 return 1;
323 } else if (addr->word != breakpoint_insn.word) {
324 /*
325 * The breakpoint instruction was removed by
326 * another cpu right after we hit, no further
327 * handling of this interrupt is appropriate
328 */
329 ret = 1;
330 }
331 goto no_kprobe;
332 }
333
334 p = get_kprobe(addr);
335 if (!p) {
336 if (addr->word != breakpoint_insn.word) {
337 /*
338 * The breakpoint instruction was removed right
339 * after we hit it. Another cpu has removed
340 * either a probepoint or a debugger breakpoint
341 * at this address. In either case, no further
342 * handling of this interrupt is appropriate.
343 */
344 ret = 1;
345 }
346 /* Not one of ours: let kernel handle it */
347 goto no_kprobe;
348 }
349
350 set_current_kprobe(p, regs, kcb);
351 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
352
353 if (p->pre_handler && p->pre_handler(p, regs)) {
354 /* handler has already set things up, so skip ss setup */
355 reset_current_kprobe();
356 preempt_enable_no_resched();
357 return 1;
358 }
359
360 prepare_singlestep(p, regs, kcb);
361 if (kcb->flags & SKIP_DELAYSLOT) {
362 kcb->kprobe_status = KPROBE_HIT_SSDONE;
363 if (p->post_handler)
364 p->post_handler(p, regs, 0);
365 resume_execution(p, regs, kcb);
366 preempt_enable_no_resched();
367 } else
368 kcb->kprobe_status = KPROBE_HIT_SS;
369
370 return 1;
371
372no_kprobe:
373 preempt_enable_no_resched();
374 return ret;
375
376}
377NOKPROBE_SYMBOL(kprobe_handler);
378
379static inline int post_kprobe_handler(struct pt_regs *regs)
380{
381 struct kprobe *cur = kprobe_running();
382 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
383
384 if (!cur)
385 return 0;
386
387 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
388 kcb->kprobe_status = KPROBE_HIT_SSDONE;
389 cur->post_handler(cur, regs, 0);
390 }
391
392 resume_execution(cur, regs, kcb);
393
394 regs->cp0_status |= kcb->kprobe_saved_SR;
395
396 /* Restore back the original saved kprobes variables and continue. */
397 if (kcb->kprobe_status == KPROBE_REENTER) {
398 restore_previous_kprobe(kcb);
399 goto out;
400 }
401 reset_current_kprobe();
402out:
403 preempt_enable_no_resched();
404
405 return 1;
406}
407
408int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
409{
410 struct kprobe *cur = kprobe_running();
411 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
412
413 if (kcb->kprobe_status & KPROBE_HIT_SS) {
414 resume_execution(cur, regs, kcb);
415 regs->cp0_status |= kcb->kprobe_old_SR;
416
417 reset_current_kprobe();
418 preempt_enable_no_resched();
419 }
420 return 0;
421}
422
423/*
424 * Wrapper routine for handling exceptions.
425 */
426int kprobe_exceptions_notify(struct notifier_block *self,
427 unsigned long val, void *data)
428{
429
430 struct die_args *args = (struct die_args *)data;
431 int ret = NOTIFY_DONE;
432
433 switch (val) {
434 case DIE_BREAK:
435 if (kprobe_handler(args->regs))
436 ret = NOTIFY_STOP;
437 break;
438 case DIE_SSTEPBP:
439 if (post_kprobe_handler(args->regs))
440 ret = NOTIFY_STOP;
441 break;
442
443 case DIE_PAGE_FAULT:
444 /* kprobe_running() needs smp_processor_id() */
445 preempt_disable();
446
447 if (kprobe_running()
448 && kprobe_fault_handler(args->regs, args->trapnr))
449 ret = NOTIFY_STOP;
450 preempt_enable();
451 break;
452 default:
453 break;
454 }
455 return ret;
456}
457NOKPROBE_SYMBOL(kprobe_exceptions_notify);
458
459/*
460 * Function return probe trampoline:
461 * - init_kprobes() establishes a probepoint here
462 * - When the probed function returns, this probe causes the
463 * handlers to fire
464 */
465static void __used kretprobe_trampoline_holder(void)
466{
467 asm volatile(
468 ".set push\n\t"
469 /* Keep the assembler from reordering and placing JR here. */
470 ".set noreorder\n\t"
471 "nop\n\t"
472 ".global __kretprobe_trampoline\n"
473 "__kretprobe_trampoline:\n\t"
474 "nop\n\t"
475 ".set pop"
476 : : : "memory");
477}
478
479void __kretprobe_trampoline(void);
480
481void arch_prepare_kretprobe(struct kretprobe_instance *ri,
482 struct pt_regs *regs)
483{
484 ri->ret_addr = (kprobe_opcode_t *) regs->regs[31];
485 ri->fp = NULL;
486
487 /* Replace the return addr with trampoline addr */
488 regs->regs[31] = (unsigned long)__kretprobe_trampoline;
489}
490NOKPROBE_SYMBOL(arch_prepare_kretprobe);
491
492/*
493 * Called when the probe at kretprobe trampoline is hit
494 */
495static int trampoline_probe_handler(struct kprobe *p,
496 struct pt_regs *regs)
497{
498 instruction_pointer(regs) = __kretprobe_trampoline_handler(regs, NULL);
499 /*
500 * By returning a non-zero value, we are telling
501 * kprobe_handler() that we don't want the post_handler
502 * to run (and have re-enabled preemption)
503 */
504 return 1;
505}
506NOKPROBE_SYMBOL(trampoline_probe_handler);
507
508int arch_trampoline_kprobe(struct kprobe *p)
509{
510 if (p->addr == (kprobe_opcode_t *)__kretprobe_trampoline)
511 return 1;
512
513 return 0;
514}
515NOKPROBE_SYMBOL(arch_trampoline_kprobe);
516
517static struct kprobe trampoline_p = {
518 .addr = (kprobe_opcode_t *)__kretprobe_trampoline,
519 .pre_handler = trampoline_probe_handler
520};
521
522int __init arch_init_kprobes(void)
523{
524 return register_kprobe(&trampoline_p);
525}
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 if (p->ainsn.insn) {
211 free_insn_slot(p->ainsn.insn, 0);
212 p->ainsn.insn = NULL;
213 }
214}
215
216static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
217{
218 kcb->prev_kprobe.kp = kprobe_running();
219 kcb->prev_kprobe.status = kcb->kprobe_status;
220 kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR;
221 kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR;
222 kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc;
223}
224
225static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
226{
227 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
228 kcb->kprobe_status = kcb->prev_kprobe.status;
229 kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR;
230 kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR;
231 kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc;
232}
233
234static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
235 struct kprobe_ctlblk *kcb)
236{
237 __this_cpu_write(current_kprobe, p);
238 kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE);
239 kcb->kprobe_saved_epc = regs->cp0_epc;
240}
241
242/**
243 * evaluate_branch_instrucion -
244 *
245 * Evaluate the branch instruction at probed address during probe hit. The
246 * result of evaluation would be the updated epc. The insturction in delayslot
247 * would actually be single stepped using a normal breakpoint) on SSOL slot.
248 *
249 * The result is also saved in the kprobe control block for later use,
250 * in case we need to execute the delayslot instruction. The latter will be
251 * false for NOP instruction in dealyslot and the branch-likely instructions
252 * when the branch is taken. And for those cases we set a flag as
253 * SKIP_DELAYSLOT in the kprobe control block
254 */
255static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs,
256 struct kprobe_ctlblk *kcb)
257{
258 union mips_instruction insn = p->opcode;
259 long epc;
260 int ret = 0;
261
262 epc = regs->cp0_epc;
263 if (epc & 3)
264 goto unaligned;
265
266 if (p->ainsn.insn->word == 0)
267 kcb->flags |= SKIP_DELAYSLOT;
268 else
269 kcb->flags &= ~SKIP_DELAYSLOT;
270
271 ret = __compute_return_epc_for_insn(regs, insn);
272 if (ret < 0)
273 return ret;
274
275 if (ret == BRANCH_LIKELY_TAKEN)
276 kcb->flags |= SKIP_DELAYSLOT;
277
278 kcb->target_epc = regs->cp0_epc;
279
280 return 0;
281
282unaligned:
283 pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm);
284 force_sig(SIGBUS, current);
285 return -EFAULT;
286
287}
288
289static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
290 struct kprobe_ctlblk *kcb)
291{
292 int ret = 0;
293
294 regs->cp0_status &= ~ST0_IE;
295
296 /* single step inline if the instruction is a break */
297 if (p->opcode.word == breakpoint_insn.word ||
298 p->opcode.word == breakpoint2_insn.word)
299 regs->cp0_epc = (unsigned long)p->addr;
300 else if (insn_has_delayslot(p->opcode)) {
301 ret = evaluate_branch_instruction(p, regs, kcb);
302 if (ret < 0) {
303 pr_notice("Kprobes: Error in evaluating branch\n");
304 return;
305 }
306 }
307 regs->cp0_epc = (unsigned long)&p->ainsn.insn[0];
308}
309
310/*
311 * Called after single-stepping. p->addr is the address of the
312 * instruction whose first byte has been replaced by the "break 0"
313 * instruction. To avoid the SMP problems that can occur when we
314 * temporarily put back the original opcode to single-step, we
315 * single-stepped a copy of the instruction. The address of this
316 * copy is p->ainsn.insn.
317 *
318 * This function prepares to return from the post-single-step
319 * breakpoint trap. In case of branch instructions, the target
320 * epc to be restored.
321 */
322static void __kprobes resume_execution(struct kprobe *p,
323 struct pt_regs *regs,
324 struct kprobe_ctlblk *kcb)
325{
326 if (insn_has_delayslot(p->opcode))
327 regs->cp0_epc = kcb->target_epc;
328 else {
329 unsigned long orig_epc = kcb->kprobe_saved_epc;
330 regs->cp0_epc = orig_epc + 4;
331 }
332}
333
334static int __kprobes kprobe_handler(struct pt_regs *regs)
335{
336 struct kprobe *p;
337 int ret = 0;
338 kprobe_opcode_t *addr;
339 struct kprobe_ctlblk *kcb;
340
341 addr = (kprobe_opcode_t *) regs->cp0_epc;
342
343 /*
344 * We don't want to be preempted for the entire
345 * duration of kprobe processing
346 */
347 preempt_disable();
348 kcb = get_kprobe_ctlblk();
349
350 /* Check we're not actually recursing */
351 if (kprobe_running()) {
352 p = get_kprobe(addr);
353 if (p) {
354 if (kcb->kprobe_status == KPROBE_HIT_SS &&
355 p->ainsn.insn->word == breakpoint_insn.word) {
356 regs->cp0_status &= ~ST0_IE;
357 regs->cp0_status |= kcb->kprobe_saved_SR;
358 goto no_kprobe;
359 }
360 /*
361 * We have reentered the kprobe_handler(), since
362 * another probe was hit while within the handler.
363 * We here save the original kprobes variables and
364 * just single step on the instruction of the new probe
365 * without calling any user handlers.
366 */
367 save_previous_kprobe(kcb);
368 set_current_kprobe(p, regs, kcb);
369 kprobes_inc_nmissed_count(p);
370 prepare_singlestep(p, regs, kcb);
371 kcb->kprobe_status = KPROBE_REENTER;
372 if (kcb->flags & SKIP_DELAYSLOT) {
373 resume_execution(p, regs, kcb);
374 restore_previous_kprobe(kcb);
375 preempt_enable_no_resched();
376 }
377 return 1;
378 } else {
379 if (addr->word != breakpoint_insn.word) {
380 /*
381 * The breakpoint instruction was removed by
382 * another cpu right after we hit, no further
383 * handling of this interrupt is appropriate
384 */
385 ret = 1;
386 goto no_kprobe;
387 }
388 p = __this_cpu_read(current_kprobe);
389 if (p->break_handler && p->break_handler(p, regs))
390 goto ss_probe;
391 }
392 goto no_kprobe;
393 }
394
395 p = get_kprobe(addr);
396 if (!p) {
397 if (addr->word != breakpoint_insn.word) {
398 /*
399 * The breakpoint instruction was removed right
400 * after we hit it. Another cpu has removed
401 * either a probepoint or a debugger breakpoint
402 * at this address. In either case, no further
403 * handling of this interrupt is appropriate.
404 */
405 ret = 1;
406 }
407 /* Not one of ours: let kernel handle it */
408 goto no_kprobe;
409 }
410
411 set_current_kprobe(p, regs, kcb);
412 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
413
414 if (p->pre_handler && p->pre_handler(p, regs)) {
415 /* handler has already set things up, so skip ss setup */
416 return 1;
417 }
418
419ss_probe:
420 prepare_singlestep(p, regs, kcb);
421 if (kcb->flags & SKIP_DELAYSLOT) {
422 kcb->kprobe_status = KPROBE_HIT_SSDONE;
423 if (p->post_handler)
424 p->post_handler(p, regs, 0);
425 resume_execution(p, regs, kcb);
426 preempt_enable_no_resched();
427 } else
428 kcb->kprobe_status = KPROBE_HIT_SS;
429
430 return 1;
431
432no_kprobe:
433 preempt_enable_no_resched();
434 return ret;
435
436}
437
438static inline int post_kprobe_handler(struct pt_regs *regs)
439{
440 struct kprobe *cur = kprobe_running();
441 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
442
443 if (!cur)
444 return 0;
445
446 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
447 kcb->kprobe_status = KPROBE_HIT_SSDONE;
448 cur->post_handler(cur, regs, 0);
449 }
450
451 resume_execution(cur, regs, kcb);
452
453 regs->cp0_status |= kcb->kprobe_saved_SR;
454
455 /* Restore back the original saved kprobes variables and continue. */
456 if (kcb->kprobe_status == KPROBE_REENTER) {
457 restore_previous_kprobe(kcb);
458 goto out;
459 }
460 reset_current_kprobe();
461out:
462 preempt_enable_no_resched();
463
464 return 1;
465}
466
467static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
468{
469 struct kprobe *cur = kprobe_running();
470 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
471
472 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
473 return 1;
474
475 if (kcb->kprobe_status & KPROBE_HIT_SS) {
476 resume_execution(cur, regs, kcb);
477 regs->cp0_status |= kcb->kprobe_old_SR;
478
479 reset_current_kprobe();
480 preempt_enable_no_resched();
481 }
482 return 0;
483}
484
485/*
486 * Wrapper routine for handling exceptions.
487 */
488int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
489 unsigned long val, void *data)
490{
491
492 struct die_args *args = (struct die_args *)data;
493 int ret = NOTIFY_DONE;
494
495 switch (val) {
496 case DIE_BREAK:
497 if (kprobe_handler(args->regs))
498 ret = NOTIFY_STOP;
499 break;
500 case DIE_SSTEPBP:
501 if (post_kprobe_handler(args->regs))
502 ret = NOTIFY_STOP;
503 break;
504
505 case DIE_PAGE_FAULT:
506 /* kprobe_running() needs smp_processor_id() */
507 preempt_disable();
508
509 if (kprobe_running()
510 && kprobe_fault_handler(args->regs, args->trapnr))
511 ret = NOTIFY_STOP;
512 preempt_enable();
513 break;
514 default:
515 break;
516 }
517 return ret;
518}
519
520int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
521{
522 struct jprobe *jp = container_of(p, struct jprobe, kp);
523 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
524
525 kcb->jprobe_saved_regs = *regs;
526 kcb->jprobe_saved_sp = regs->regs[29];
527
528 memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp,
529 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
530
531 regs->cp0_epc = (unsigned long)(jp->entry);
532
533 return 1;
534}
535
536/* Defined in the inline asm below. */
537void jprobe_return_end(void);
538
539void __kprobes jprobe_return(void)
540{
541 /* Assembler quirk necessitates this '0,code' business. */
542 asm volatile(
543 "break 0,%0\n\t"
544 ".globl jprobe_return_end\n"
545 "jprobe_return_end:\n"
546 : : "n" (BRK_KPROBE_BP) : "memory");
547}
548
549int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
550{
551 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
552
553 if (regs->cp0_epc >= (unsigned long)jprobe_return &&
554 regs->cp0_epc <= (unsigned long)jprobe_return_end) {
555 *regs = kcb->jprobe_saved_regs;
556 memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack,
557 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
558 preempt_enable_no_resched();
559
560 return 1;
561 }
562 return 0;
563}
564
565/*
566 * Function return probe trampoline:
567 * - init_kprobes() establishes a probepoint here
568 * - When the probed function returns, this probe causes the
569 * handlers to fire
570 */
571static void __used kretprobe_trampoline_holder(void)
572{
573 asm volatile(
574 ".set push\n\t"
575 /* Keep the assembler from reordering and placing JR here. */
576 ".set noreorder\n\t"
577 "nop\n\t"
578 ".global kretprobe_trampoline\n"
579 "kretprobe_trampoline:\n\t"
580 "nop\n\t"
581 ".set pop"
582 : : : "memory");
583}
584
585void kretprobe_trampoline(void);
586
587void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
588 struct pt_regs *regs)
589{
590 ri->ret_addr = (kprobe_opcode_t *) regs->regs[31];
591
592 /* Replace the return addr with trampoline addr */
593 regs->regs[31] = (unsigned long)kretprobe_trampoline;
594}
595
596/*
597 * Called when the probe at kretprobe trampoline is hit
598 */
599static int __kprobes trampoline_probe_handler(struct kprobe *p,
600 struct pt_regs *regs)
601{
602 struct kretprobe_instance *ri = NULL;
603 struct hlist_head *head, empty_rp;
604 struct hlist_node *tmp;
605 unsigned long flags, orig_ret_address = 0;
606 unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
607
608 INIT_HLIST_HEAD(&empty_rp);
609 kretprobe_hash_lock(current, &head, &flags);
610
611 /*
612 * It is possible to have multiple instances associated with a given
613 * task either because an multiple functions in the call path
614 * have a return probe installed on them, and/or more than one return
615 * return probe was registered for a target function.
616 *
617 * We can handle this because:
618 * - instances are always inserted at the head of the list
619 * - when multiple return probes are registered for the same
620 * function, the first instance's ret_addr will point to the
621 * real return address, and all the rest will point to
622 * kretprobe_trampoline
623 */
624 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
625 if (ri->task != current)
626 /* another task is sharing our hash bucket */
627 continue;
628
629 if (ri->rp && ri->rp->handler)
630 ri->rp->handler(ri, regs);
631
632 orig_ret_address = (unsigned long)ri->ret_addr;
633 recycle_rp_inst(ri, &empty_rp);
634
635 if (orig_ret_address != trampoline_address)
636 /*
637 * This is the real return address. Any other
638 * instances associated with this task are for
639 * other calls deeper on the call stack
640 */
641 break;
642 }
643
644 kretprobe_assert(ri, orig_ret_address, trampoline_address);
645 instruction_pointer(regs) = orig_ret_address;
646
647 reset_current_kprobe();
648 kretprobe_hash_unlock(current, &flags);
649 preempt_enable_no_resched();
650
651 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
652 hlist_del(&ri->hlist);
653 kfree(ri);
654 }
655 /*
656 * By returning a non-zero value, we are telling
657 * kprobe_handler() that we don't want the post_handler
658 * to run (and have re-enabled preemption)
659 */
660 return 1;
661}
662
663int __kprobes arch_trampoline_kprobe(struct kprobe *p)
664{
665 if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline)
666 return 1;
667
668 return 0;
669}
670
671static struct kprobe trampoline_p = {
672 .addr = (kprobe_opcode_t *)kretprobe_trampoline,
673 .pre_handler = trampoline_probe_handler
674};
675
676int __init arch_init_kprobes(void)
677{
678 return register_kprobe(&trampoline_p);
679}