Commit | Line | Data |
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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 DD |
34 | #include <asm/break.h> |
35 | #include <asm/inst.h> | |
36 | ||
37 | static const union mips_instruction breakpoint_insn = { | |
38 | .b_format = { | |
39 | .opcode = spec_op, | |
40 | .code = BRK_KPROBE_BP, | |
41 | .func = break_op | |
42 | } | |
43 | }; | |
44 | ||
45 | static const union mips_instruction breakpoint2_insn = { | |
46 | .b_format = { | |
47 | .opcode = spec_op, | |
48 | .code = BRK_KPROBE_SSTEPBP, | |
49 | .func = break_op | |
50 | } | |
51 | }; | |
52 | ||
53 | DEFINE_PER_CPU(struct kprobe *, current_kprobe); | |
54 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
55 | ||
56 | static int __kprobes insn_has_delayslot(union mips_instruction insn) | |
57 | { | |
58 | switch (insn.i_format.opcode) { | |
59 | ||
60 | /* | |
61 | * This group contains: | |
62 | * jr and jalr are in r_format format. | |
63 | */ | |
64 | case spec_op: | |
65 | switch (insn.r_format.func) { | |
66 | case jr_op: | |
67 | case jalr_op: | |
68 | break; | |
69 | default: | |
70 | goto insn_ok; | |
71 | } | |
72 | ||
73 | /* | |
74 | * This group contains: | |
75 | * bltz_op, bgez_op, bltzl_op, bgezl_op, | |
76 | * bltzal_op, bgezal_op, bltzall_op, bgezall_op. | |
77 | */ | |
78 | case bcond_op: | |
79 | ||
80 | /* | |
81 | * These are unconditional and in j_format. | |
82 | */ | |
83 | case jal_op: | |
84 | case j_op: | |
85 | ||
86 | /* | |
87 | * These are conditional and in i_format. | |
88 | */ | |
89 | case beq_op: | |
90 | case beql_op: | |
91 | case bne_op: | |
92 | case bnel_op: | |
93 | case blez_op: | |
94 | case blezl_op: | |
95 | case bgtz_op: | |
96 | case bgtzl_op: | |
97 | ||
98 | /* | |
99 | * These are the FPA/cp1 branch instructions. | |
100 | */ | |
101 | case cop1_op: | |
102 | ||
103 | #ifdef CONFIG_CPU_CAVIUM_OCTEON | |
104 | case lwc2_op: /* This is bbit0 on Octeon */ | |
105 | case ldc2_op: /* This is bbit032 on Octeon */ | |
106 | case swc2_op: /* This is bbit1 on Octeon */ | |
107 | case sdc2_op: /* This is bbit132 on Octeon */ | |
108 | #endif | |
109 | return 1; | |
110 | default: | |
111 | break; | |
112 | } | |
113 | insn_ok: | |
114 | return 0; | |
115 | } | |
116 | ||
9233c1ee MS |
117 | /* |
118 | * insn_has_ll_or_sc function checks whether instruction is ll or sc | |
119 | * one; putting breakpoint on top of atomic ll/sc pair is bad idea; | |
120 | * so we need to prevent it and refuse kprobes insertion for such | |
121 | * instructions; cannot do much about breakpoint in the middle of | |
122 | * ll/sc pair; it is upto user to avoid those places | |
123 | */ | |
124 | static int __kprobes insn_has_ll_or_sc(union mips_instruction insn) | |
125 | { | |
126 | int ret = 0; | |
127 | ||
128 | switch (insn.i_format.opcode) { | |
129 | case ll_op: | |
130 | case lld_op: | |
131 | case sc_op: | |
132 | case scd_op: | |
133 | ret = 1; | |
134 | break; | |
135 | default: | |
136 | break; | |
137 | } | |
138 | return ret; | |
139 | } | |
140 | ||
c1bf207d DD |
141 | int __kprobes arch_prepare_kprobe(struct kprobe *p) |
142 | { | |
143 | union mips_instruction insn; | |
144 | union mips_instruction prev_insn; | |
145 | int ret = 0; | |
146 | ||
c1bf207d DD |
147 | insn = p->addr[0]; |
148 | ||
9233c1ee MS |
149 | if (insn_has_ll_or_sc(insn)) { |
150 | pr_notice("Kprobes for ll and sc instructions are not" | |
151 | "supported\n"); | |
152 | ret = -EINVAL; | |
153 | goto out; | |
154 | } | |
155 | ||
41dde781 MS |
156 | if ((probe_kernel_read(&prev_insn, p->addr - 1, |
157 | sizeof(mips_instruction)) == 0) && | |
158 | insn_has_delayslot(prev_insn)) { | |
159 | pr_notice("Kprobes for branch delayslot are not supported\n"); | |
c1bf207d DD |
160 | ret = -EINVAL; |
161 | goto out; | |
162 | } | |
163 | ||
164 | /* insn: must be on special executable page on mips. */ | |
165 | p->ainsn.insn = get_insn_slot(); | |
166 | if (!p->ainsn.insn) { | |
167 | ret = -ENOMEM; | |
168 | goto out; | |
169 | } | |
170 | ||
171 | /* | |
172 | * In the kprobe->ainsn.insn[] array we store the original | |
173 | * instruction at index zero and a break trap instruction at | |
174 | * index one. | |
6457a396 MS |
175 | * |
176 | * On MIPS arch if the instruction at probed address is a | |
177 | * branch instruction, we need to execute the instruction at | |
178 | * Branch Delayslot (BD) at the time of probe hit. As MIPS also | |
179 | * doesn't have single stepping support, the BD instruction can | |
180 | * not be executed in-line and it would be executed on SSOL slot | |
181 | * using a normal breakpoint instruction in the next slot. | |
182 | * So, read the instruction and save it for later execution. | |
c1bf207d | 183 | */ |
6457a396 MS |
184 | if (insn_has_delayslot(insn)) |
185 | memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t)); | |
186 | else | |
187 | memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t)); | |
c1bf207d | 188 | |
c1bf207d DD |
189 | p->ainsn.insn[1] = breakpoint2_insn; |
190 | p->opcode = *p->addr; | |
191 | ||
192 | out: | |
193 | return ret; | |
194 | } | |
195 | ||
196 | void __kprobes arch_arm_kprobe(struct kprobe *p) | |
197 | { | |
198 | *p->addr = breakpoint_insn; | |
199 | flush_insn_slot(p); | |
200 | } | |
201 | ||
202 | void __kprobes arch_disarm_kprobe(struct kprobe *p) | |
203 | { | |
204 | *p->addr = p->opcode; | |
205 | flush_insn_slot(p); | |
206 | } | |
207 | ||
208 | void __kprobes arch_remove_kprobe(struct kprobe *p) | |
209 | { | |
210 | free_insn_slot(p->ainsn.insn, 0); | |
211 | } | |
212 | ||
213 | static void save_previous_kprobe(struct kprobe_ctlblk *kcb) | |
214 | { | |
215 | kcb->prev_kprobe.kp = kprobe_running(); | |
216 | kcb->prev_kprobe.status = kcb->kprobe_status; | |
217 | kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR; | |
218 | kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR; | |
219 | kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc; | |
220 | } | |
221 | ||
222 | static void restore_previous_kprobe(struct kprobe_ctlblk *kcb) | |
223 | { | |
224 | __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; | |
225 | kcb->kprobe_status = kcb->prev_kprobe.status; | |
226 | kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR; | |
227 | kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR; | |
228 | kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc; | |
229 | } | |
230 | ||
231 | static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs, | |
232 | struct kprobe_ctlblk *kcb) | |
233 | { | |
234 | __get_cpu_var(current_kprobe) = p; | |
235 | kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE); | |
236 | kcb->kprobe_saved_epc = regs->cp0_epc; | |
237 | } | |
238 | ||
6457a396 MS |
239 | /** |
240 | * evaluate_branch_instrucion - | |
241 | * | |
242 | * Evaluate the branch instruction at probed address during probe hit. The | |
243 | * result of evaluation would be the updated epc. The insturction in delayslot | |
244 | * would actually be single stepped using a normal breakpoint) on SSOL slot. | |
245 | * | |
246 | * The result is also saved in the kprobe control block for later use, | |
247 | * in case we need to execute the delayslot instruction. The latter will be | |
248 | * false for NOP instruction in dealyslot and the branch-likely instructions | |
249 | * when the branch is taken. And for those cases we set a flag as | |
250 | * SKIP_DELAYSLOT in the kprobe control block | |
251 | */ | |
252 | static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs, | |
253 | struct kprobe_ctlblk *kcb) | |
254 | { | |
255 | union mips_instruction insn = p->opcode; | |
256 | long epc; | |
257 | int ret = 0; | |
258 | ||
259 | epc = regs->cp0_epc; | |
260 | if (epc & 3) | |
261 | goto unaligned; | |
262 | ||
263 | if (p->ainsn.insn->word == 0) | |
264 | kcb->flags |= SKIP_DELAYSLOT; | |
265 | else | |
266 | kcb->flags &= ~SKIP_DELAYSLOT; | |
267 | ||
268 | ret = __compute_return_epc_for_insn(regs, insn); | |
269 | if (ret < 0) | |
270 | return ret; | |
271 | ||
272 | if (ret == BRANCH_LIKELY_TAKEN) | |
273 | kcb->flags |= SKIP_DELAYSLOT; | |
274 | ||
275 | kcb->target_epc = regs->cp0_epc; | |
276 | ||
277 | return 0; | |
278 | ||
279 | unaligned: | |
280 | pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm); | |
281 | force_sig(SIGBUS, current); | |
282 | return -EFAULT; | |
283 | ||
284 | } | |
285 | ||
286 | static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs, | |
287 | struct kprobe_ctlblk *kcb) | |
c1bf207d | 288 | { |
6457a396 MS |
289 | int ret = 0; |
290 | ||
c1bf207d DD |
291 | regs->cp0_status &= ~ST0_IE; |
292 | ||
293 | /* single step inline if the instruction is a break */ | |
294 | if (p->opcode.word == breakpoint_insn.word || | |
295 | p->opcode.word == breakpoint2_insn.word) | |
296 | regs->cp0_epc = (unsigned long)p->addr; | |
6457a396 MS |
297 | else if (insn_has_delayslot(p->opcode)) { |
298 | ret = evaluate_branch_instruction(p, regs, kcb); | |
299 | if (ret < 0) { | |
300 | pr_notice("Kprobes: Error in evaluating branch\n"); | |
301 | return; | |
302 | } | |
303 | } | |
304 | regs->cp0_epc = (unsigned long)&p->ainsn.insn[0]; | |
305 | } | |
306 | ||
307 | /* | |
308 | * Called after single-stepping. p->addr is the address of the | |
309 | * instruction whose first byte has been replaced by the "break 0" | |
310 | * instruction. To avoid the SMP problems that can occur when we | |
311 | * temporarily put back the original opcode to single-step, we | |
312 | * single-stepped a copy of the instruction. The address of this | |
313 | * copy is p->ainsn.insn. | |
314 | * | |
315 | * This function prepares to return from the post-single-step | |
316 | * breakpoint trap. In case of branch instructions, the target | |
317 | * epc to be restored. | |
318 | */ | |
319 | static void __kprobes resume_execution(struct kprobe *p, | |
320 | struct pt_regs *regs, | |
321 | struct kprobe_ctlblk *kcb) | |
322 | { | |
323 | if (insn_has_delayslot(p->opcode)) | |
324 | regs->cp0_epc = kcb->target_epc; | |
325 | else { | |
326 | unsigned long orig_epc = kcb->kprobe_saved_epc; | |
327 | regs->cp0_epc = orig_epc + 4; | |
328 | } | |
c1bf207d DD |
329 | } |
330 | ||
331 | static int __kprobes kprobe_handler(struct pt_regs *regs) | |
332 | { | |
333 | struct kprobe *p; | |
334 | int ret = 0; | |
335 | kprobe_opcode_t *addr; | |
336 | struct kprobe_ctlblk *kcb; | |
337 | ||
338 | addr = (kprobe_opcode_t *) regs->cp0_epc; | |
339 | ||
340 | /* | |
341 | * We don't want to be preempted for the entire | |
342 | * duration of kprobe processing | |
343 | */ | |
344 | preempt_disable(); | |
345 | kcb = get_kprobe_ctlblk(); | |
346 | ||
347 | /* Check we're not actually recursing */ | |
348 | if (kprobe_running()) { | |
349 | p = get_kprobe(addr); | |
350 | if (p) { | |
351 | if (kcb->kprobe_status == KPROBE_HIT_SS && | |
352 | p->ainsn.insn->word == breakpoint_insn.word) { | |
353 | regs->cp0_status &= ~ST0_IE; | |
354 | regs->cp0_status |= kcb->kprobe_saved_SR; | |
355 | goto no_kprobe; | |
356 | } | |
357 | /* | |
358 | * We have reentered the kprobe_handler(), since | |
359 | * another probe was hit while within the handler. | |
360 | * We here save the original kprobes variables and | |
361 | * just single step on the instruction of the new probe | |
362 | * without calling any user handlers. | |
363 | */ | |
364 | save_previous_kprobe(kcb); | |
365 | set_current_kprobe(p, regs, kcb); | |
366 | kprobes_inc_nmissed_count(p); | |
6457a396 | 367 | prepare_singlestep(p, regs, kcb); |
c1bf207d | 368 | kcb->kprobe_status = KPROBE_REENTER; |
6457a396 MS |
369 | if (kcb->flags & SKIP_DELAYSLOT) { |
370 | resume_execution(p, regs, kcb); | |
371 | restore_previous_kprobe(kcb); | |
372 | preempt_enable_no_resched(); | |
373 | } | |
c1bf207d DD |
374 | return 1; |
375 | } else { | |
376 | if (addr->word != breakpoint_insn.word) { | |
377 | /* | |
378 | * The breakpoint instruction was removed by | |
379 | * another cpu right after we hit, no further | |
380 | * handling of this interrupt is appropriate | |
381 | */ | |
382 | ret = 1; | |
383 | goto no_kprobe; | |
384 | } | |
385 | p = __get_cpu_var(current_kprobe); | |
386 | if (p->break_handler && p->break_handler(p, regs)) | |
387 | goto ss_probe; | |
388 | } | |
389 | goto no_kprobe; | |
390 | } | |
391 | ||
392 | p = get_kprobe(addr); | |
393 | if (!p) { | |
394 | if (addr->word != breakpoint_insn.word) { | |
395 | /* | |
396 | * The breakpoint instruction was removed right | |
397 | * after we hit it. Another cpu has removed | |
398 | * either a probepoint or a debugger breakpoint | |
399 | * at this address. In either case, no further | |
400 | * handling of this interrupt is appropriate. | |
401 | */ | |
402 | ret = 1; | |
403 | } | |
404 | /* Not one of ours: let kernel handle it */ | |
405 | goto no_kprobe; | |
406 | } | |
407 | ||
408 | set_current_kprobe(p, regs, kcb); | |
409 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; | |
410 | ||
411 | if (p->pre_handler && p->pre_handler(p, regs)) { | |
412 | /* handler has already set things up, so skip ss setup */ | |
413 | return 1; | |
414 | } | |
415 | ||
416 | ss_probe: | |
6457a396 MS |
417 | prepare_singlestep(p, regs, kcb); |
418 | if (kcb->flags & SKIP_DELAYSLOT) { | |
419 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
420 | if (p->post_handler) | |
421 | p->post_handler(p, regs, 0); | |
422 | resume_execution(p, regs, kcb); | |
423 | preempt_enable_no_resched(); | |
424 | } else | |
425 | kcb->kprobe_status = KPROBE_HIT_SS; | |
426 | ||
c1bf207d DD |
427 | return 1; |
428 | ||
429 | no_kprobe: | |
430 | preempt_enable_no_resched(); | |
431 | return ret; | |
432 | ||
433 | } | |
434 | ||
c1bf207d DD |
435 | static inline int post_kprobe_handler(struct pt_regs *regs) |
436 | { | |
437 | struct kprobe *cur = kprobe_running(); | |
438 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
439 | ||
440 | if (!cur) | |
441 | return 0; | |
442 | ||
443 | if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { | |
444 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
445 | cur->post_handler(cur, regs, 0); | |
446 | } | |
447 | ||
448 | resume_execution(cur, regs, kcb); | |
449 | ||
450 | regs->cp0_status |= kcb->kprobe_saved_SR; | |
451 | ||
452 | /* Restore back the original saved kprobes variables and continue. */ | |
453 | if (kcb->kprobe_status == KPROBE_REENTER) { | |
454 | restore_previous_kprobe(kcb); | |
455 | goto out; | |
456 | } | |
457 | reset_current_kprobe(); | |
458 | out: | |
459 | preempt_enable_no_resched(); | |
460 | ||
461 | return 1; | |
462 | } | |
463 | ||
464 | static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) | |
465 | { | |
466 | struct kprobe *cur = kprobe_running(); | |
467 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
468 | ||
469 | if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) | |
470 | return 1; | |
471 | ||
472 | if (kcb->kprobe_status & KPROBE_HIT_SS) { | |
473 | resume_execution(cur, regs, kcb); | |
474 | regs->cp0_status |= kcb->kprobe_old_SR; | |
475 | ||
476 | reset_current_kprobe(); | |
477 | preempt_enable_no_resched(); | |
478 | } | |
479 | return 0; | |
480 | } | |
481 | ||
482 | /* | |
483 | * Wrapper routine for handling exceptions. | |
484 | */ | |
485 | int __kprobes kprobe_exceptions_notify(struct notifier_block *self, | |
486 | unsigned long val, void *data) | |
487 | { | |
488 | ||
489 | struct die_args *args = (struct die_args *)data; | |
490 | int ret = NOTIFY_DONE; | |
491 | ||
492 | switch (val) { | |
493 | case DIE_BREAK: | |
494 | if (kprobe_handler(args->regs)) | |
495 | ret = NOTIFY_STOP; | |
496 | break; | |
497 | case DIE_SSTEPBP: | |
498 | if (post_kprobe_handler(args->regs)) | |
499 | ret = NOTIFY_STOP; | |
500 | break; | |
501 | ||
502 | case DIE_PAGE_FAULT: | |
503 | /* kprobe_running() needs smp_processor_id() */ | |
504 | preempt_disable(); | |
505 | ||
506 | if (kprobe_running() | |
507 | && kprobe_fault_handler(args->regs, args->trapnr)) | |
508 | ret = NOTIFY_STOP; | |
509 | preempt_enable(); | |
510 | break; | |
511 | default: | |
512 | break; | |
513 | } | |
514 | return ret; | |
515 | } | |
516 | ||
517 | int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
518 | { | |
519 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
520 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
521 | ||
522 | kcb->jprobe_saved_regs = *regs; | |
523 | kcb->jprobe_saved_sp = regs->regs[29]; | |
524 | ||
525 | memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp, | |
526 | MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp)); | |
527 | ||
528 | regs->cp0_epc = (unsigned long)(jp->entry); | |
529 | ||
530 | return 1; | |
531 | } | |
532 | ||
533 | /* Defined in the inline asm below. */ | |
534 | void jprobe_return_end(void); | |
535 | ||
536 | void __kprobes jprobe_return(void) | |
537 | { | |
538 | /* Assembler quirk necessitates this '0,code' business. */ | |
539 | asm volatile( | |
540 | "break 0,%0\n\t" | |
541 | ".globl jprobe_return_end\n" | |
542 | "jprobe_return_end:\n" | |
543 | : : "n" (BRK_KPROBE_BP) : "memory"); | |
544 | } | |
545 | ||
546 | int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) | |
547 | { | |
548 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
549 | ||
550 | if (regs->cp0_epc >= (unsigned long)jprobe_return && | |
551 | regs->cp0_epc <= (unsigned long)jprobe_return_end) { | |
552 | *regs = kcb->jprobe_saved_regs; | |
553 | memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack, | |
554 | MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp)); | |
555 | preempt_enable_no_resched(); | |
556 | ||
557 | return 1; | |
558 | } | |
559 | return 0; | |
560 | } | |
561 | ||
562 | /* | |
563 | * Function return probe trampoline: | |
564 | * - init_kprobes() establishes a probepoint here | |
565 | * - When the probed function returns, this probe causes the | |
566 | * handlers to fire | |
567 | */ | |
568 | static void __used kretprobe_trampoline_holder(void) | |
569 | { | |
570 | asm volatile( | |
571 | ".set push\n\t" | |
572 | /* Keep the assembler from reordering and placing JR here. */ | |
573 | ".set noreorder\n\t" | |
574 | "nop\n\t" | |
575 | ".global kretprobe_trampoline\n" | |
576 | "kretprobe_trampoline:\n\t" | |
577 | "nop\n\t" | |
578 | ".set pop" | |
579 | : : : "memory"); | |
580 | } | |
581 | ||
582 | void kretprobe_trampoline(void); | |
583 | ||
584 | void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, | |
585 | struct pt_regs *regs) | |
586 | { | |
587 | ri->ret_addr = (kprobe_opcode_t *) regs->regs[31]; | |
588 | ||
589 | /* Replace the return addr with trampoline addr */ | |
590 | regs->regs[31] = (unsigned long)kretprobe_trampoline; | |
591 | } | |
592 | ||
593 | /* | |
594 | * Called when the probe at kretprobe trampoline is hit | |
595 | */ | |
596 | static int __kprobes trampoline_probe_handler(struct kprobe *p, | |
597 | struct pt_regs *regs) | |
598 | { | |
599 | struct kretprobe_instance *ri = NULL; | |
600 | struct hlist_head *head, empty_rp; | |
b67bfe0d | 601 | struct hlist_node *tmp; |
c1bf207d DD |
602 | unsigned long flags, orig_ret_address = 0; |
603 | unsigned long trampoline_address = (unsigned long)kretprobe_trampoline; | |
604 | ||
605 | INIT_HLIST_HEAD(&empty_rp); | |
606 | kretprobe_hash_lock(current, &head, &flags); | |
607 | ||
608 | /* | |
609 | * It is possible to have multiple instances associated with a given | |
610 | * task either because an multiple functions in the call path | |
611 | * have a return probe installed on them, and/or more than one return | |
612 | * return probe was registered for a target function. | |
613 | * | |
614 | * We can handle this because: | |
615 | * - instances are always inserted at the head of the list | |
616 | * - when multiple return probes are registered for the same | |
617 | * function, the first instance's ret_addr will point to the | |
618 | * real return address, and all the rest will point to | |
619 | * kretprobe_trampoline | |
620 | */ | |
b67bfe0d | 621 | hlist_for_each_entry_safe(ri, tmp, head, hlist) { |
c1bf207d DD |
622 | if (ri->task != current) |
623 | /* another task is sharing our hash bucket */ | |
624 | continue; | |
625 | ||
626 | if (ri->rp && ri->rp->handler) | |
627 | ri->rp->handler(ri, regs); | |
628 | ||
629 | orig_ret_address = (unsigned long)ri->ret_addr; | |
630 | recycle_rp_inst(ri, &empty_rp); | |
631 | ||
632 | if (orig_ret_address != trampoline_address) | |
633 | /* | |
634 | * This is the real return address. Any other | |
635 | * instances associated with this task are for | |
636 | * other calls deeper on the call stack | |
637 | */ | |
638 | break; | |
639 | } | |
640 | ||
641 | kretprobe_assert(ri, orig_ret_address, trampoline_address); | |
642 | instruction_pointer(regs) = orig_ret_address; | |
643 | ||
644 | reset_current_kprobe(); | |
645 | kretprobe_hash_unlock(current, &flags); | |
646 | preempt_enable_no_resched(); | |
647 | ||
b67bfe0d | 648 | hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { |
c1bf207d DD |
649 | hlist_del(&ri->hlist); |
650 | kfree(ri); | |
651 | } | |
652 | /* | |
653 | * By returning a non-zero value, we are telling | |
654 | * kprobe_handler() that we don't want the post_handler | |
655 | * to run (and have re-enabled preemption) | |
656 | */ | |
657 | return 1; | |
658 | } | |
659 | ||
660 | int __kprobes arch_trampoline_kprobe(struct kprobe *p) | |
661 | { | |
662 | if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline) | |
663 | return 1; | |
664 | ||
665 | return 0; | |
666 | } | |
667 | ||
668 | static struct kprobe trampoline_p = { | |
669 | .addr = (kprobe_opcode_t *)kretprobe_trampoline, | |
670 | .pre_handler = trampoline_probe_handler | |
671 | }; | |
672 | ||
673 | int __init arch_init_kprobes(void) | |
674 | { | |
675 | return register_kprobe(&trampoline_p); | |
676 | } |