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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/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}
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}