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c1bf207d DD |
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> | |
41dde781 | 28 | #include <linux/uaccess.h> |
c1bf207d DD |
29 | #include <linux/kdebug.h> |
30 | #include <linux/slab.h> | |
31 | ||
32 | #include <asm/ptrace.h> | |
6457a396 | 33 | #include <asm/branch.h> |
c1bf207d | 34 | #include <asm/break.h> |
e3031b32 MN |
35 | |
36 | #include "probes-common.h" | |
c1bf207d DD |
37 | |
38 | static 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 | ||
46 | static 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 | ||
54 | DEFINE_PER_CPU(struct kprobe *, current_kprobe); | |
55 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
56 | ||
57 | static int __kprobes insn_has_delayslot(union mips_instruction insn) | |
58 | { | |
e3031b32 | 59 | return __insn_has_delay_slot(insn); |
c1bf207d DD |
60 | } |
61 | ||
9233c1ee MS |
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 | */ | |
69 | static 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 | ||
c1bf207d DD |
86 | int __kprobes arch_prepare_kprobe(struct kprobe *p) |
87 | { | |
88 | union mips_instruction insn; | |
89 | union mips_instruction prev_insn; | |
90 | int ret = 0; | |
91 | ||
c1bf207d DD |
92 | insn = p->addr[0]; |
93 | ||
9233c1ee MS |
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 | ||
41dde781 MS |
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"); | |
c1bf207d DD |
105 | ret = -EINVAL; |
106 | goto out; | |
107 | } | |
108 | ||
d05c5130 MN |
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 | ||
c1bf207d DD |
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. | |
6457a396 MS |
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. | |
c1bf207d | 134 | */ |
6457a396 MS |
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)); | |
c1bf207d | 139 | |
c1bf207d DD |
140 | p->ainsn.insn[1] = breakpoint2_insn; |
141 | p->opcode = *p->addr; | |
142 | ||
143 | out: | |
144 | return ret; | |
145 | } | |
146 | ||
147 | void __kprobes arch_arm_kprobe(struct kprobe *p) | |
148 | { | |
149 | *p->addr = breakpoint_insn; | |
150 | flush_insn_slot(p); | |
151 | } | |
152 | ||
153 | void __kprobes arch_disarm_kprobe(struct kprobe *p) | |
154 | { | |
155 | *p->addr = p->opcode; | |
156 | flush_insn_slot(p); | |
157 | } | |
158 | ||
159 | void __kprobes arch_remove_kprobe(struct kprobe *p) | |
160 | { | |
22047b85 MH |
161 | if (p->ainsn.insn) { |
162 | free_insn_slot(p->ainsn.insn, 0); | |
163 | p->ainsn.insn = NULL; | |
164 | } | |
c1bf207d DD |
165 | } |
166 | ||
167 | static 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 | ||
176 | static void restore_previous_kprobe(struct kprobe_ctlblk *kcb) | |
177 | { | |
35898716 | 178 | __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); |
c1bf207d DD |
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 | ||
185 | static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs, | |
186 | struct kprobe_ctlblk *kcb) | |
187 | { | |
35898716 | 188 | __this_cpu_write(current_kprobe, p); |
c1bf207d DD |
189 | kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE); |
190 | kcb->kprobe_saved_epc = regs->cp0_epc; | |
191 | } | |
192 | ||
6457a396 MS |
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 | */ | |
206 | static 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 | ||
233 | unaligned: | |
234 | pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm); | |
235 | force_sig(SIGBUS, current); | |
236 | return -EFAULT; | |
237 | ||
238 | } | |
239 | ||
240 | static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs, | |
241 | struct kprobe_ctlblk *kcb) | |
c1bf207d | 242 | { |
6457a396 MS |
243 | int ret = 0; |
244 | ||
c1bf207d DD |
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; | |
6457a396 MS |
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" | |
70342287 | 264 | * instruction. To avoid the SMP problems that can occur when we |
6457a396 MS |
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 | */ | |
273 | static 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 | } | |
c1bf207d DD |
283 | } |
284 | ||
285 | static 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); | |
6457a396 | 321 | prepare_singlestep(p, regs, kcb); |
c1bf207d | 322 | kcb->kprobe_status = KPROBE_REENTER; |
6457a396 MS |
323 | if (kcb->flags & SKIP_DELAYSLOT) { |
324 | resume_execution(p, regs, kcb); | |
325 | restore_previous_kprobe(kcb); | |
326 | preempt_enable_no_resched(); | |
327 | } | |
c1bf207d DD |
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 | } | |
35898716 | 339 | p = __this_cpu_read(current_kprobe); |
c1bf207d DD |
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 | ||
370 | ss_probe: | |
6457a396 MS |
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 | ||
c1bf207d DD |
381 | return 1; |
382 | ||
383 | no_kprobe: | |
384 | preempt_enable_no_resched(); | |
385 | return ret; | |
386 | ||
387 | } | |
388 | ||
c1bf207d DD |
389 | static 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(); | |
412 | out: | |
413 | preempt_enable_no_resched(); | |
414 | ||
415 | return 1; | |
416 | } | |
417 | ||
418 | static 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 | */ | |
439 | int __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 | ||
471 | int __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. */ | |
488 | void jprobe_return_end(void); | |
489 | ||
490 | void __kprobes jprobe_return(void) | |
491 | { | |
70342287 | 492 | /* Assembler quirk necessitates this '0,code' business. */ |
c1bf207d DD |
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 | ||
500 | int __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 | */ | |
522 | static 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 | ||
536 | void kretprobe_trampoline(void); | |
537 | ||
538 | void __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 | */ | |
550 | static 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; | |
b67bfe0d | 555 | struct hlist_node *tmp; |
c1bf207d DD |
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 | |
70342287 RB |
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 | |
c1bf207d | 574 | */ |
b67bfe0d | 575 | hlist_for_each_entry_safe(ri, tmp, head, hlist) { |
c1bf207d DD |
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 | ||
b67bfe0d | 602 | hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { |
c1bf207d DD |
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 | ||
614 | int __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 | ||
622 | static struct kprobe trampoline_p = { | |
623 | .addr = (kprobe_opcode_t *)kretprobe_trampoline, | |
624 | .pre_handler = trampoline_probe_handler | |
625 | }; | |
626 | ||
627 | int __init arch_init_kprobes(void) | |
628 | { | |
629 | return register_kprobe(&trampoline_p); | |
630 | } |