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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)) { | |
93 | pr_notice("Kprobes for control instructions are not " | |
94 | "supported\n"); | |
95 | return -EINVAL; | |
96 | } | |
97 | ||
98 | /* insn: must be on special executable page on tile. */ | |
99 | p->ainsn.insn = get_insn_slot(); | |
100 | if (!p->ainsn.insn) | |
101 | return -ENOMEM; | |
102 | ||
103 | /* | |
104 | * In the kprobe->ainsn.insn[] array we store the original | |
105 | * instruction at index zero and a break trap instruction at | |
106 | * index one. | |
107 | */ | |
108 | memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t)); | |
109 | p->ainsn.insn[1] = breakpoint2_insn; | |
110 | p->opcode = *p->addr; | |
111 | ||
112 | return 0; | |
113 | } | |
114 | ||
115 | void __kprobes arch_arm_kprobe(struct kprobe *p) | |
116 | { | |
117 | unsigned long addr_wr; | |
118 | ||
119 | /* Operate on writable kernel text mapping. */ | |
120 | addr_wr = (unsigned long)p->addr - MEM_SV_START + PAGE_OFFSET; | |
121 | ||
122 | if (probe_kernel_write((void *)addr_wr, &breakpoint_insn, | |
123 | sizeof(breakpoint_insn))) | |
124 | pr_err("%s: failed to enable kprobe\n", __func__); | |
125 | ||
126 | smp_wmb(); | |
127 | flush_insn_slot(p); | |
128 | } | |
129 | ||
130 | void __kprobes arch_disarm_kprobe(struct kprobe *kp) | |
131 | { | |
132 | unsigned long addr_wr; | |
133 | ||
134 | /* Operate on writable kernel text mapping. */ | |
135 | addr_wr = (unsigned long)kp->addr - MEM_SV_START + PAGE_OFFSET; | |
136 | ||
137 | if (probe_kernel_write((void *)addr_wr, &kp->opcode, | |
138 | sizeof(kp->opcode))) | |
139 | pr_err("%s: failed to enable kprobe\n", __func__); | |
140 | ||
141 | smp_wmb(); | |
142 | flush_insn_slot(kp); | |
143 | } | |
144 | ||
145 | void __kprobes arch_remove_kprobe(struct kprobe *p) | |
146 | { | |
147 | if (p->ainsn.insn) { | |
148 | free_insn_slot(p->ainsn.insn, 0); | |
149 | p->ainsn.insn = NULL; | |
150 | } | |
151 | } | |
152 | ||
153 | static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) | |
154 | { | |
155 | kcb->prev_kprobe.kp = kprobe_running(); | |
156 | kcb->prev_kprobe.status = kcb->kprobe_status; | |
157 | kcb->prev_kprobe.saved_pc = kcb->kprobe_saved_pc; | |
158 | } | |
159 | ||
160 | static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) | |
161 | { | |
162 | __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); | |
163 | kcb->kprobe_status = kcb->prev_kprobe.status; | |
164 | kcb->kprobe_saved_pc = kcb->prev_kprobe.saved_pc; | |
165 | } | |
166 | ||
167 | static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, | |
168 | struct kprobe_ctlblk *kcb) | |
169 | { | |
170 | __this_cpu_write(current_kprobe, p); | |
171 | kcb->kprobe_saved_pc = regs->pc; | |
172 | } | |
173 | ||
174 | static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) | |
175 | { | |
176 | /* Single step inline if the instruction is a break. */ | |
177 | if (p->opcode == breakpoint_insn || | |
178 | p->opcode == breakpoint2_insn) | |
179 | regs->pc = (unsigned long)p->addr; | |
180 | else | |
181 | regs->pc = (unsigned long)&p->ainsn.insn[0]; | |
182 | } | |
183 | ||
184 | static int __kprobes kprobe_handler(struct pt_regs *regs) | |
185 | { | |
186 | struct kprobe *p; | |
187 | int ret = 0; | |
188 | kprobe_opcode_t *addr; | |
189 | struct kprobe_ctlblk *kcb; | |
190 | ||
191 | addr = (kprobe_opcode_t *)regs->pc; | |
192 | ||
193 | /* | |
194 | * We don't want to be preempted for the entire | |
195 | * duration of kprobe processing. | |
196 | */ | |
197 | preempt_disable(); | |
198 | kcb = get_kprobe_ctlblk(); | |
199 | ||
200 | /* Check we're not actually recursing. */ | |
201 | if (kprobe_running()) { | |
202 | p = get_kprobe(addr); | |
203 | if (p) { | |
204 | if (kcb->kprobe_status == KPROBE_HIT_SS && | |
205 | p->ainsn.insn[0] == breakpoint_insn) { | |
206 | goto no_kprobe; | |
207 | } | |
208 | /* | |
209 | * We have reentered the kprobe_handler(), since | |
210 | * another probe was hit while within the handler. | |
211 | * We here save the original kprobes variables and | |
212 | * just single step on the instruction of the new probe | |
213 | * without calling any user handlers. | |
214 | */ | |
215 | save_previous_kprobe(kcb); | |
216 | set_current_kprobe(p, regs, kcb); | |
217 | kprobes_inc_nmissed_count(p); | |
218 | prepare_singlestep(p, regs); | |
219 | kcb->kprobe_status = KPROBE_REENTER; | |
220 | return 1; | |
221 | } else { | |
222 | if (*addr != breakpoint_insn) { | |
223 | /* | |
224 | * The breakpoint instruction was removed by | |
225 | * another cpu right after we hit, no further | |
226 | * handling of this interrupt is appropriate. | |
227 | */ | |
228 | ret = 1; | |
229 | goto no_kprobe; | |
230 | } | |
231 | p = __this_cpu_read(current_kprobe); | |
232 | if (p->break_handler && p->break_handler(p, regs)) | |
233 | goto ss_probe; | |
234 | } | |
235 | goto no_kprobe; | |
236 | } | |
237 | ||
238 | p = get_kprobe(addr); | |
239 | if (!p) { | |
240 | if (*addr != breakpoint_insn) { | |
241 | /* | |
242 | * The breakpoint instruction was removed right | |
243 | * after we hit it. Another cpu has removed | |
244 | * either a probepoint or a debugger breakpoint | |
245 | * at this address. In either case, no further | |
246 | * handling of this interrupt is appropriate. | |
247 | */ | |
248 | ret = 1; | |
249 | } | |
250 | /* Not one of ours: let kernel handle it. */ | |
251 | goto no_kprobe; | |
252 | } | |
253 | ||
254 | set_current_kprobe(p, regs, kcb); | |
255 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; | |
256 | ||
257 | if (p->pre_handler && p->pre_handler(p, regs)) { | |
258 | /* Handler has already set things up, so skip ss setup. */ | |
259 | return 1; | |
260 | } | |
261 | ||
262 | ss_probe: | |
263 | prepare_singlestep(p, regs); | |
264 | kcb->kprobe_status = KPROBE_HIT_SS; | |
265 | return 1; | |
266 | ||
267 | no_kprobe: | |
268 | preempt_enable_no_resched(); | |
269 | return ret; | |
270 | } | |
271 | ||
272 | /* | |
273 | * Called after single-stepping. p->addr is the address of the | |
274 | * instruction that has been replaced by the breakpoint. To avoid the | |
275 | * SMP problems that can occur when we temporarily put back the | |
276 | * original opcode to single-step, we single-stepped a copy of the | |
277 | * instruction. The address of this copy is p->ainsn.insn. | |
278 | * | |
279 | * This function prepares to return from the post-single-step | |
280 | * breakpoint trap. | |
281 | */ | |
282 | static void __kprobes resume_execution(struct kprobe *p, | |
283 | struct pt_regs *regs, | |
284 | struct kprobe_ctlblk *kcb) | |
285 | { | |
286 | unsigned long orig_pc = kcb->kprobe_saved_pc; | |
287 | regs->pc = orig_pc + 8; | |
288 | } | |
289 | ||
290 | static inline int post_kprobe_handler(struct pt_regs *regs) | |
291 | { | |
292 | struct kprobe *cur = kprobe_running(); | |
293 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
294 | ||
295 | if (!cur) | |
296 | return 0; | |
297 | ||
298 | if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { | |
299 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
300 | cur->post_handler(cur, regs, 0); | |
301 | } | |
302 | ||
303 | resume_execution(cur, regs, kcb); | |
304 | ||
305 | /* Restore back the original saved kprobes variables and continue. */ | |
306 | if (kcb->kprobe_status == KPROBE_REENTER) { | |
307 | restore_previous_kprobe(kcb); | |
308 | goto out; | |
309 | } | |
310 | reset_current_kprobe(); | |
311 | out: | |
312 | preempt_enable_no_resched(); | |
313 | ||
314 | return 1; | |
315 | } | |
316 | ||
317 | static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) | |
318 | { | |
319 | struct kprobe *cur = kprobe_running(); | |
320 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
321 | ||
322 | if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) | |
323 | return 1; | |
324 | ||
325 | if (kcb->kprobe_status & KPROBE_HIT_SS) { | |
326 | /* | |
327 | * We are here because the instruction being single | |
328 | * stepped caused a page fault. We reset the current | |
329 | * kprobe and the ip points back to the probe address | |
330 | * and allow the page fault handler to continue as a | |
331 | * normal page fault. | |
332 | */ | |
333 | resume_execution(cur, regs, kcb); | |
334 | reset_current_kprobe(); | |
335 | preempt_enable_no_resched(); | |
336 | } | |
337 | return 0; | |
338 | } | |
339 | ||
340 | /* | |
341 | * Wrapper routine for handling exceptions. | |
342 | */ | |
343 | int __kprobes kprobe_exceptions_notify(struct notifier_block *self, | |
344 | unsigned long val, void *data) | |
345 | { | |
346 | struct die_args *args = (struct die_args *)data; | |
347 | int ret = NOTIFY_DONE; | |
348 | ||
349 | switch (val) { | |
350 | case DIE_BREAK: | |
351 | if (kprobe_handler(args->regs)) | |
352 | ret = NOTIFY_STOP; | |
353 | break; | |
354 | case DIE_SSTEPBP: | |
355 | if (post_kprobe_handler(args->regs)) | |
356 | ret = NOTIFY_STOP; | |
357 | break; | |
358 | case DIE_PAGE_FAULT: | |
359 | /* kprobe_running() needs smp_processor_id(). */ | |
360 | preempt_disable(); | |
361 | ||
362 | if (kprobe_running() | |
363 | && kprobe_fault_handler(args->regs, args->trapnr)) | |
364 | ret = NOTIFY_STOP; | |
365 | preempt_enable(); | |
366 | break; | |
367 | default: | |
368 | break; | |
369 | } | |
370 | return ret; | |
371 | } | |
372 | ||
373 | int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
374 | { | |
375 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
376 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
377 | ||
378 | kcb->jprobe_saved_regs = *regs; | |
379 | kcb->jprobe_saved_sp = regs->sp; | |
380 | ||
381 | memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp, | |
382 | MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp)); | |
383 | ||
384 | regs->pc = (unsigned long)(jp->entry); | |
385 | ||
386 | return 1; | |
387 | } | |
388 | ||
389 | /* Defined in the inline asm below. */ | |
390 | void jprobe_return_end(void); | |
391 | ||
392 | void __kprobes jprobe_return(void) | |
393 | { | |
394 | asm volatile( | |
395 | "bpt\n\t" | |
396 | ".globl jprobe_return_end\n" | |
397 | "jprobe_return_end:\n"); | |
398 | } | |
399 | ||
400 | int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) | |
401 | { | |
402 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
403 | ||
404 | if (regs->pc >= (unsigned long)jprobe_return && | |
405 | regs->pc <= (unsigned long)jprobe_return_end) { | |
406 | *regs = kcb->jprobe_saved_regs; | |
407 | memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack, | |
408 | MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp)); | |
409 | preempt_enable_no_resched(); | |
410 | ||
411 | return 1; | |
412 | } | |
413 | return 0; | |
414 | } | |
415 | ||
416 | /* | |
417 | * Function return probe trampoline: | |
418 | * - init_kprobes() establishes a probepoint here | |
419 | * - When the probed function returns, this probe causes the | |
420 | * handlers to fire | |
421 | */ | |
422 | static void __used kretprobe_trampoline_holder(void) | |
423 | { | |
424 | asm volatile( | |
425 | "nop\n\t" | |
426 | ".global kretprobe_trampoline\n" | |
427 | "kretprobe_trampoline:\n\t" | |
428 | "nop\n\t" | |
429 | : : : "memory"); | |
430 | } | |
431 | ||
432 | void kretprobe_trampoline(void); | |
433 | ||
434 | void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, | |
435 | struct pt_regs *regs) | |
436 | { | |
437 | ri->ret_addr = (kprobe_opcode_t *) regs->lr; | |
438 | ||
439 | /* Replace the return addr with trampoline addr */ | |
440 | regs->lr = (unsigned long)kretprobe_trampoline; | |
441 | } | |
442 | ||
443 | /* | |
444 | * Called when the probe at kretprobe trampoline is hit. | |
445 | */ | |
446 | static int __kprobes trampoline_probe_handler(struct kprobe *p, | |
447 | struct pt_regs *regs) | |
448 | { | |
449 | struct kretprobe_instance *ri = NULL; | |
450 | struct hlist_head *head, empty_rp; | |
451 | struct hlist_node *tmp; | |
452 | unsigned long flags, orig_ret_address = 0; | |
453 | unsigned long trampoline_address = (unsigned long)kretprobe_trampoline; | |
454 | ||
455 | INIT_HLIST_HEAD(&empty_rp); | |
456 | kretprobe_hash_lock(current, &head, &flags); | |
457 | ||
458 | /* | |
459 | * It is possible to have multiple instances associated with a given | |
460 | * task either because multiple functions in the call path have | |
461 | * a return probe installed on them, and/or more than one return | |
462 | * return probe was registered for a target function. | |
463 | * | |
464 | * We can handle this because: | |
465 | * - instances are always inserted at the head of the list | |
466 | * - when multiple return probes are registered for the same | |
467 | * function, the first instance's ret_addr will point to the | |
468 | * real return address, and all the rest will point to | |
469 | * kretprobe_trampoline | |
470 | */ | |
471 | hlist_for_each_entry_safe(ri, tmp, head, hlist) { | |
472 | if (ri->task != current) | |
473 | /* another task is sharing our hash bucket */ | |
474 | continue; | |
475 | ||
476 | if (ri->rp && ri->rp->handler) | |
477 | ri->rp->handler(ri, regs); | |
478 | ||
479 | orig_ret_address = (unsigned long)ri->ret_addr; | |
480 | recycle_rp_inst(ri, &empty_rp); | |
481 | ||
482 | if (orig_ret_address != trampoline_address) { | |
483 | /* | |
484 | * This is the real return address. Any other | |
485 | * instances associated with this task are for | |
486 | * other calls deeper on the call stack | |
487 | */ | |
488 | break; | |
489 | } | |
490 | } | |
491 | ||
492 | kretprobe_assert(ri, orig_ret_address, trampoline_address); | |
493 | instruction_pointer(regs) = orig_ret_address; | |
494 | ||
495 | reset_current_kprobe(); | |
496 | kretprobe_hash_unlock(current, &flags); | |
497 | preempt_enable_no_resched(); | |
498 | ||
499 | hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { | |
500 | hlist_del(&ri->hlist); | |
501 | kfree(ri); | |
502 | } | |
503 | /* | |
504 | * By returning a non-zero value, we are telling | |
505 | * kprobe_handler() that we don't want the post_handler | |
506 | * to run (and have re-enabled preemption) | |
507 | */ | |
508 | return 1; | |
509 | } | |
510 | ||
511 | int __kprobes arch_trampoline_kprobe(struct kprobe *p) | |
512 | { | |
513 | if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline) | |
514 | return 1; | |
515 | ||
516 | return 0; | |
517 | } | |
518 | ||
519 | static struct kprobe trampoline_p = { | |
520 | .addr = (kprobe_opcode_t *)kretprobe_trampoline, | |
521 | .pre_handler = trampoline_probe_handler | |
522 | }; | |
523 | ||
524 | int __init arch_init_kprobes(void) | |
525 | { | |
526 | register_kprobe(&trampoline_p); | |
527 | return 0; | |
528 | } |