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3fa17c39 TL |
1 | /* |
2 | * arch/tile/kernel/kprobes.c | |
3 | * Kprobes on TILE-Gx | |
4 | * | |
5 | * Some portions copied from the MIPS version. | |
6 | * | |
7 | * Copyright (C) IBM Corporation, 2002, 2004 | |
8 | * Copyright 2006 Sony Corp. | |
9 | * Copyright 2010 Cavium Networks | |
10 | * | |
11 | * Copyright 2012 Tilera Corporation. All Rights Reserved. | |
12 | * | |
13 | * This program is free software; you can redistribute it and/or | |
14 | * modify it under the terms of the GNU General Public License | |
15 | * as published by the Free Software Foundation, version 2. | |
16 | * | |
17 | * This program is distributed in the hope that it will be useful, but | |
18 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or | |
20 | * NON INFRINGEMENT. See the GNU General Public License for | |
21 | * more details. | |
22 | */ | |
23 | ||
24 | #include <linux/kprobes.h> | |
25 | #include <linux/kdebug.h> | |
26 | #include <linux/module.h> | |
27 | #include <linux/slab.h> | |
28 | #include <linux/uaccess.h> | |
29 | #include <asm/cacheflush.h> | |
30 | ||
31 | #include <arch/opcode.h> | |
32 | ||
33 | DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; | |
34 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
35 | ||
36 | tile_bundle_bits breakpoint_insn = TILEGX_BPT_BUNDLE; | |
37 | tile_bundle_bits breakpoint2_insn = TILEGX_BPT_BUNDLE | DIE_SSTEPBP; | |
38 | ||
39 | /* | |
40 | * Check whether instruction is branch or jump, or if executing it | |
41 | * has different results depending on where it is executed (e.g. lnk). | |
42 | */ | |
43 | static int __kprobes insn_has_control(kprobe_opcode_t insn) | |
44 | { | |
45 | if (get_Mode(insn) != 0) { /* Y-format bundle */ | |
46 | if (get_Opcode_Y1(insn) != RRR_1_OPCODE_Y1 || | |
47 | get_RRROpcodeExtension_Y1(insn) != UNARY_RRR_1_OPCODE_Y1) | |
48 | return 0; | |
49 | ||
50 | switch (get_UnaryOpcodeExtension_Y1(insn)) { | |
51 | case JALRP_UNARY_OPCODE_Y1: | |
52 | case JALR_UNARY_OPCODE_Y1: | |
53 | case JRP_UNARY_OPCODE_Y1: | |
54 | case JR_UNARY_OPCODE_Y1: | |
55 | case LNK_UNARY_OPCODE_Y1: | |
56 | return 1; | |
57 | default: | |
58 | return 0; | |
59 | } | |
60 | } | |
61 | ||
62 | switch (get_Opcode_X1(insn)) { | |
63 | case BRANCH_OPCODE_X1: /* branch instructions */ | |
64 | case JUMP_OPCODE_X1: /* jump instructions: j and jal */ | |
65 | return 1; | |
66 | ||
67 | case RRR_0_OPCODE_X1: /* other jump instructions */ | |
68 | if (get_RRROpcodeExtension_X1(insn) != UNARY_RRR_0_OPCODE_X1) | |
69 | return 0; | |
70 | switch (get_UnaryOpcodeExtension_X1(insn)) { | |
71 | case JALRP_UNARY_OPCODE_X1: | |
72 | case JALR_UNARY_OPCODE_X1: | |
73 | case JRP_UNARY_OPCODE_X1: | |
74 | case JR_UNARY_OPCODE_X1: | |
75 | case LNK_UNARY_OPCODE_X1: | |
76 | return 1; | |
77 | default: | |
78 | return 0; | |
79 | } | |
80 | default: | |
81 | return 0; | |
82 | } | |
83 | } | |
84 | ||
85 | int __kprobes arch_prepare_kprobe(struct kprobe *p) | |
86 | { | |
87 | unsigned long addr = (unsigned long)p->addr; | |
88 | ||
89 | if (addr & (sizeof(kprobe_opcode_t) - 1)) | |
90 | return -EINVAL; | |
91 | ||
92 | if (insn_has_control(*p->addr)) { | |
f4743673 | 93 | pr_notice("Kprobes for control instructions are not supported\n"); |
3fa17c39 TL |
94 | return -EINVAL; |
95 | } | |
96 | ||
97 | /* insn: must be on special executable page on tile. */ | |
98 | p->ainsn.insn = get_insn_slot(); | |
99 | if (!p->ainsn.insn) | |
100 | return -ENOMEM; | |
101 | ||
102 | /* | |
103 | * In the kprobe->ainsn.insn[] array we store the original | |
104 | * instruction at index zero and a break trap instruction at | |
105 | * index one. | |
106 | */ | |
107 | memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t)); | |
108 | p->ainsn.insn[1] = breakpoint2_insn; | |
109 | p->opcode = *p->addr; | |
110 | ||
111 | return 0; | |
112 | } | |
113 | ||
114 | void __kprobes arch_arm_kprobe(struct kprobe *p) | |
115 | { | |
116 | unsigned long addr_wr; | |
117 | ||
118 | /* Operate on writable kernel text mapping. */ | |
f419e6f6 | 119 | addr_wr = ktext_writable_addr(p->addr); |
3fa17c39 TL |
120 | |
121 | if (probe_kernel_write((void *)addr_wr, &breakpoint_insn, | |
122 | sizeof(breakpoint_insn))) | |
123 | pr_err("%s: failed to enable kprobe\n", __func__); | |
124 | ||
125 | smp_wmb(); | |
126 | flush_insn_slot(p); | |
127 | } | |
128 | ||
129 | void __kprobes arch_disarm_kprobe(struct kprobe *kp) | |
130 | { | |
131 | unsigned long addr_wr; | |
132 | ||
133 | /* Operate on writable kernel text mapping. */ | |
f419e6f6 | 134 | addr_wr = ktext_writable_addr(kp->addr); |
3fa17c39 TL |
135 | |
136 | if (probe_kernel_write((void *)addr_wr, &kp->opcode, | |
137 | sizeof(kp->opcode))) | |
138 | pr_err("%s: failed to enable kprobe\n", __func__); | |
139 | ||
140 | smp_wmb(); | |
141 | flush_insn_slot(kp); | |
142 | } | |
143 | ||
144 | void __kprobes arch_remove_kprobe(struct kprobe *p) | |
145 | { | |
146 | if (p->ainsn.insn) { | |
147 | free_insn_slot(p->ainsn.insn, 0); | |
148 | p->ainsn.insn = NULL; | |
149 | } | |
150 | } | |
151 | ||
152 | static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) | |
153 | { | |
154 | kcb->prev_kprobe.kp = kprobe_running(); | |
155 | kcb->prev_kprobe.status = kcb->kprobe_status; | |
156 | kcb->prev_kprobe.saved_pc = kcb->kprobe_saved_pc; | |
157 | } | |
158 | ||
159 | static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) | |
160 | { | |
161 | __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); | |
162 | kcb->kprobe_status = kcb->prev_kprobe.status; | |
163 | kcb->kprobe_saved_pc = kcb->prev_kprobe.saved_pc; | |
164 | } | |
165 | ||
166 | static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, | |
167 | struct kprobe_ctlblk *kcb) | |
168 | { | |
169 | __this_cpu_write(current_kprobe, p); | |
170 | kcb->kprobe_saved_pc = regs->pc; | |
171 | } | |
172 | ||
173 | static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) | |
174 | { | |
175 | /* Single step inline if the instruction is a break. */ | |
176 | if (p->opcode == breakpoint_insn || | |
177 | p->opcode == breakpoint2_insn) | |
178 | regs->pc = (unsigned long)p->addr; | |
179 | else | |
180 | regs->pc = (unsigned long)&p->ainsn.insn[0]; | |
181 | } | |
182 | ||
183 | static int __kprobes kprobe_handler(struct pt_regs *regs) | |
184 | { | |
185 | struct kprobe *p; | |
186 | int ret = 0; | |
187 | kprobe_opcode_t *addr; | |
188 | struct kprobe_ctlblk *kcb; | |
189 | ||
190 | addr = (kprobe_opcode_t *)regs->pc; | |
191 | ||
192 | /* | |
193 | * We don't want to be preempted for the entire | |
194 | * duration of kprobe processing. | |
195 | */ | |
196 | preempt_disable(); | |
197 | kcb = get_kprobe_ctlblk(); | |
198 | ||
199 | /* Check we're not actually recursing. */ | |
200 | if (kprobe_running()) { | |
201 | p = get_kprobe(addr); | |
202 | if (p) { | |
203 | if (kcb->kprobe_status == KPROBE_HIT_SS && | |
204 | p->ainsn.insn[0] == breakpoint_insn) { | |
205 | goto no_kprobe; | |
206 | } | |
207 | /* | |
208 | * We have reentered the kprobe_handler(), since | |
209 | * another probe was hit while within the handler. | |
210 | * We here save the original kprobes variables and | |
211 | * just single step on the instruction of the new probe | |
212 | * without calling any user handlers. | |
213 | */ | |
214 | save_previous_kprobe(kcb); | |
215 | set_current_kprobe(p, regs, kcb); | |
216 | kprobes_inc_nmissed_count(p); | |
217 | prepare_singlestep(p, regs); | |
218 | kcb->kprobe_status = KPROBE_REENTER; | |
219 | return 1; | |
220 | } else { | |
221 | if (*addr != breakpoint_insn) { | |
222 | /* | |
223 | * The breakpoint instruction was removed by | |
224 | * another cpu right after we hit, no further | |
225 | * handling of this interrupt is appropriate. | |
226 | */ | |
227 | ret = 1; | |
228 | goto no_kprobe; | |
229 | } | |
230 | p = __this_cpu_read(current_kprobe); | |
231 | if (p->break_handler && p->break_handler(p, regs)) | |
232 | goto ss_probe; | |
233 | } | |
234 | goto no_kprobe; | |
235 | } | |
236 | ||
237 | p = get_kprobe(addr); | |
238 | if (!p) { | |
239 | if (*addr != breakpoint_insn) { | |
240 | /* | |
241 | * The breakpoint instruction was removed right | |
242 | * after we hit it. Another cpu has removed | |
243 | * either a probepoint or a debugger breakpoint | |
244 | * at this address. In either case, no further | |
245 | * handling of this interrupt is appropriate. | |
246 | */ | |
247 | ret = 1; | |
248 | } | |
249 | /* Not one of ours: let kernel handle it. */ | |
250 | goto no_kprobe; | |
251 | } | |
252 | ||
253 | set_current_kprobe(p, regs, kcb); | |
254 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; | |
255 | ||
256 | if (p->pre_handler && p->pre_handler(p, regs)) { | |
257 | /* Handler has already set things up, so skip ss setup. */ | |
258 | return 1; | |
259 | } | |
260 | ||
261 | ss_probe: | |
262 | prepare_singlestep(p, regs); | |
263 | kcb->kprobe_status = KPROBE_HIT_SS; | |
264 | return 1; | |
265 | ||
266 | no_kprobe: | |
267 | preempt_enable_no_resched(); | |
268 | return ret; | |
269 | } | |
270 | ||
271 | /* | |
272 | * Called after single-stepping. p->addr is the address of the | |
273 | * instruction that has been replaced by the breakpoint. To avoid the | |
274 | * SMP problems that can occur when we temporarily put back the | |
275 | * original opcode to single-step, we single-stepped a copy of the | |
276 | * instruction. The address of this copy is p->ainsn.insn. | |
277 | * | |
278 | * This function prepares to return from the post-single-step | |
279 | * breakpoint trap. | |
280 | */ | |
281 | static void __kprobes resume_execution(struct kprobe *p, | |
282 | struct pt_regs *regs, | |
283 | struct kprobe_ctlblk *kcb) | |
284 | { | |
285 | unsigned long orig_pc = kcb->kprobe_saved_pc; | |
286 | regs->pc = orig_pc + 8; | |
287 | } | |
288 | ||
289 | static inline int post_kprobe_handler(struct pt_regs *regs) | |
290 | { | |
291 | struct kprobe *cur = kprobe_running(); | |
292 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
293 | ||
294 | if (!cur) | |
295 | return 0; | |
296 | ||
297 | if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { | |
298 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
299 | cur->post_handler(cur, regs, 0); | |
300 | } | |
301 | ||
302 | resume_execution(cur, regs, kcb); | |
303 | ||
304 | /* Restore back the original saved kprobes variables and continue. */ | |
305 | if (kcb->kprobe_status == KPROBE_REENTER) { | |
306 | restore_previous_kprobe(kcb); | |
307 | goto out; | |
308 | } | |
309 | reset_current_kprobe(); | |
310 | out: | |
311 | preempt_enable_no_resched(); | |
312 | ||
313 | return 1; | |
314 | } | |
315 | ||
316 | static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) | |
317 | { | |
318 | struct kprobe *cur = kprobe_running(); | |
319 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
320 | ||
321 | if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) | |
322 | return 1; | |
323 | ||
324 | if (kcb->kprobe_status & KPROBE_HIT_SS) { | |
325 | /* | |
326 | * We are here because the instruction being single | |
327 | * stepped caused a page fault. We reset the current | |
328 | * kprobe and the ip points back to the probe address | |
329 | * and allow the page fault handler to continue as a | |
330 | * normal page fault. | |
331 | */ | |
332 | resume_execution(cur, regs, kcb); | |
333 | reset_current_kprobe(); | |
334 | preempt_enable_no_resched(); | |
335 | } | |
336 | return 0; | |
337 | } | |
338 | ||
339 | /* | |
340 | * Wrapper routine for handling exceptions. | |
341 | */ | |
342 | int __kprobes kprobe_exceptions_notify(struct notifier_block *self, | |
343 | unsigned long val, void *data) | |
344 | { | |
345 | struct die_args *args = (struct die_args *)data; | |
346 | int ret = NOTIFY_DONE; | |
347 | ||
348 | switch (val) { | |
349 | case DIE_BREAK: | |
350 | if (kprobe_handler(args->regs)) | |
351 | ret = NOTIFY_STOP; | |
352 | break; | |
353 | case DIE_SSTEPBP: | |
354 | if (post_kprobe_handler(args->regs)) | |
355 | ret = NOTIFY_STOP; | |
356 | break; | |
357 | case DIE_PAGE_FAULT: | |
358 | /* kprobe_running() needs smp_processor_id(). */ | |
359 | preempt_disable(); | |
360 | ||
361 | if (kprobe_running() | |
362 | && kprobe_fault_handler(args->regs, args->trapnr)) | |
363 | ret = NOTIFY_STOP; | |
364 | preempt_enable(); | |
365 | break; | |
366 | default: | |
367 | break; | |
368 | } | |
369 | return ret; | |
370 | } | |
371 | ||
372 | int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
373 | { | |
374 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
375 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
376 | ||
377 | kcb->jprobe_saved_regs = *regs; | |
378 | kcb->jprobe_saved_sp = regs->sp; | |
379 | ||
380 | memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp, | |
381 | MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp)); | |
382 | ||
383 | regs->pc = (unsigned long)(jp->entry); | |
384 | ||
385 | return 1; | |
386 | } | |
387 | ||
388 | /* Defined in the inline asm below. */ | |
389 | void jprobe_return_end(void); | |
390 | ||
391 | void __kprobes jprobe_return(void) | |
392 | { | |
393 | asm volatile( | |
394 | "bpt\n\t" | |
395 | ".globl jprobe_return_end\n" | |
396 | "jprobe_return_end:\n"); | |
397 | } | |
398 | ||
399 | int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) | |
400 | { | |
401 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
402 | ||
403 | if (regs->pc >= (unsigned long)jprobe_return && | |
404 | regs->pc <= (unsigned long)jprobe_return_end) { | |
405 | *regs = kcb->jprobe_saved_regs; | |
406 | memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack, | |
407 | MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp)); | |
408 | preempt_enable_no_resched(); | |
409 | ||
410 | return 1; | |
411 | } | |
412 | return 0; | |
413 | } | |
414 | ||
415 | /* | |
416 | * Function return probe trampoline: | |
417 | * - init_kprobes() establishes a probepoint here | |
418 | * - When the probed function returns, this probe causes the | |
419 | * handlers to fire | |
420 | */ | |
421 | static void __used kretprobe_trampoline_holder(void) | |
422 | { | |
423 | asm volatile( | |
424 | "nop\n\t" | |
425 | ".global kretprobe_trampoline\n" | |
426 | "kretprobe_trampoline:\n\t" | |
427 | "nop\n\t" | |
428 | : : : "memory"); | |
429 | } | |
430 | ||
431 | void kretprobe_trampoline(void); | |
432 | ||
433 | void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, | |
434 | struct pt_regs *regs) | |
435 | { | |
436 | ri->ret_addr = (kprobe_opcode_t *) regs->lr; | |
437 | ||
438 | /* Replace the return addr with trampoline addr */ | |
439 | regs->lr = (unsigned long)kretprobe_trampoline; | |
440 | } | |
441 | ||
442 | /* | |
443 | * Called when the probe at kretprobe trampoline is hit. | |
444 | */ | |
445 | static int __kprobes trampoline_probe_handler(struct kprobe *p, | |
446 | struct pt_regs *regs) | |
447 | { | |
448 | struct kretprobe_instance *ri = NULL; | |
449 | struct hlist_head *head, empty_rp; | |
450 | struct hlist_node *tmp; | |
451 | unsigned long flags, orig_ret_address = 0; | |
452 | unsigned long trampoline_address = (unsigned long)kretprobe_trampoline; | |
453 | ||
454 | INIT_HLIST_HEAD(&empty_rp); | |
455 | kretprobe_hash_lock(current, &head, &flags); | |
456 | ||
457 | /* | |
458 | * It is possible to have multiple instances associated with a given | |
459 | * task either because multiple functions in the call path have | |
460 | * a return probe installed on them, and/or more than one return | |
461 | * return probe was registered for a target function. | |
462 | * | |
463 | * We can handle this because: | |
464 | * - instances are always inserted at the head of the list | |
465 | * - when multiple return probes are registered for the same | |
466 | * function, the first instance's ret_addr will point to the | |
467 | * real return address, and all the rest will point to | |
468 | * kretprobe_trampoline | |
469 | */ | |
470 | hlist_for_each_entry_safe(ri, tmp, head, hlist) { | |
471 | if (ri->task != current) | |
472 | /* another task is sharing our hash bucket */ | |
473 | continue; | |
474 | ||
475 | if (ri->rp && ri->rp->handler) | |
476 | ri->rp->handler(ri, regs); | |
477 | ||
478 | orig_ret_address = (unsigned long)ri->ret_addr; | |
479 | recycle_rp_inst(ri, &empty_rp); | |
480 | ||
481 | if (orig_ret_address != trampoline_address) { | |
482 | /* | |
483 | * This is the real return address. Any other | |
484 | * instances associated with this task are for | |
485 | * other calls deeper on the call stack | |
486 | */ | |
487 | break; | |
488 | } | |
489 | } | |
490 | ||
491 | kretprobe_assert(ri, orig_ret_address, trampoline_address); | |
492 | instruction_pointer(regs) = orig_ret_address; | |
493 | ||
494 | reset_current_kprobe(); | |
495 | kretprobe_hash_unlock(current, &flags); | |
496 | preempt_enable_no_resched(); | |
497 | ||
498 | hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { | |
499 | hlist_del(&ri->hlist); | |
500 | kfree(ri); | |
501 | } | |
502 | /* | |
503 | * By returning a non-zero value, we are telling | |
504 | * kprobe_handler() that we don't want the post_handler | |
505 | * to run (and have re-enabled preemption) | |
506 | */ | |
507 | return 1; | |
508 | } | |
509 | ||
510 | int __kprobes arch_trampoline_kprobe(struct kprobe *p) | |
511 | { | |
512 | if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline) | |
513 | return 1; | |
514 | ||
515 | return 0; | |
516 | } | |
517 | ||
518 | static struct kprobe trampoline_p = { | |
519 | .addr = (kprobe_opcode_t *)kretprobe_trampoline, | |
520 | .pre_handler = trampoline_probe_handler | |
521 | }; | |
522 | ||
523 | int __init arch_init_kprobes(void) | |
524 | { | |
525 | register_kprobe(&trampoline_p); | |
526 | return 0; | |
527 | } |