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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 | ||
35 | static 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 | ||
43 | static 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 | ||
51 | DEFINE_PER_CPU(struct kprobe *, current_kprobe); | |
52 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
53 | ||
54 | static 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 | } | |
111 | insn_ok: | |
112 | return 0; | |
113 | } | |
114 | ||
115 | int __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 | ||
147 | out: | |
148 | return ret; | |
149 | } | |
150 | ||
151 | void __kprobes arch_arm_kprobe(struct kprobe *p) | |
152 | { | |
153 | *p->addr = breakpoint_insn; | |
154 | flush_insn_slot(p); | |
155 | } | |
156 | ||
157 | void __kprobes arch_disarm_kprobe(struct kprobe *p) | |
158 | { | |
159 | *p->addr = p->opcode; | |
160 | flush_insn_slot(p); | |
161 | } | |
162 | ||
163 | void __kprobes arch_remove_kprobe(struct kprobe *p) | |
164 | { | |
165 | free_insn_slot(p->ainsn.insn, 0); | |
166 | } | |
167 | ||
168 | static 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 | ||
177 | static 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 | ||
186 | static 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 | ||
194 | static 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 | ||
206 | static 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 | ||
286 | ss_probe: | |
287 | prepare_singlestep(p, regs); | |
288 | kcb->kprobe_status = KPROBE_HIT_SS; | |
289 | return 1; | |
290 | ||
291 | no_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 | */ | |
308 | static 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 | ||
316 | static 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(); | |
339 | out: | |
340 | preempt_enable_no_resched(); | |
341 | ||
342 | return 1; | |
343 | } | |
344 | ||
345 | static 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 | */ | |
366 | int __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 | ||
398 | int __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. */ | |
415 | void jprobe_return_end(void); | |
416 | ||
417 | void __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 | ||
427 | int __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 | */ | |
449 | static 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 | ||
463 | void kretprobe_trampoline(void); | |
464 | ||
465 | void __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 | */ | |
477 | static 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 | ||
541 | int __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 | ||
549 | static struct kprobe trampoline_p = { | |
550 | .addr = (kprobe_opcode_t *)kretprobe_trampoline, | |
551 | .pre_handler = trampoline_probe_handler | |
552 | }; | |
553 | ||
554 | int __init arch_init_kprobes(void) | |
555 | { | |
556 | return register_kprobe(&trampoline_p); | |
557 | } |