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24ba613c AS |
1 | /* |
2 | * arch/arm/kernel/kprobes.c | |
3 | * | |
4 | * Kprobes on ARM | |
5 | * | |
6 | * Abhishek Sagar <sagar.abhishek@gmail.com> | |
7 | * Copyright (C) 2006, 2007 Motorola Inc. | |
8 | * | |
9 | * Nicolas Pitre <nico@marvell.com> | |
10 | * Copyright (C) 2007 Marvell Ltd. | |
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 version 2 as | |
14 | * published by the Free Software Foundation. | |
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 GNU | |
19 | * General Public License for more details. | |
20 | */ | |
21 | ||
22 | #include <linux/kernel.h> | |
23 | #include <linux/kprobes.h> | |
24 | #include <linux/module.h> | |
5a0e3ad6 | 25 | #include <linux/slab.h> |
2003b7af | 26 | #include <linux/stop_machine.h> |
24ba613c AS |
27 | #include <linux/stringify.h> |
28 | #include <asm/traps.h> | |
29 | #include <asm/cacheflush.h> | |
30 | ||
24ba613c AS |
31 | #define MIN_STACK_SIZE(addr) \ |
32 | min((unsigned long)MAX_STACK_SIZE, \ | |
33 | (unsigned long)current_thread_info() + THREAD_START_SP - (addr)) | |
34 | ||
35 | #define flush_insns(addr, cnt) \ | |
36 | flush_icache_range((unsigned long)(addr), \ | |
37 | (unsigned long)(addr) + \ | |
38 | sizeof(kprobe_opcode_t) * (cnt)) | |
39 | ||
40 | /* Used as a marker in ARM_pc to note when we're in a jprobe. */ | |
41 | #define JPROBE_MAGIC_ADDR 0xffffffff | |
42 | ||
43 | DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; | |
44 | DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); | |
45 | ||
46 | ||
47 | int __kprobes arch_prepare_kprobe(struct kprobe *p) | |
48 | { | |
49 | kprobe_opcode_t insn; | |
50 | kprobe_opcode_t tmp_insn[MAX_INSN_SIZE]; | |
51 | unsigned long addr = (unsigned long)p->addr; | |
52 | int is; | |
53 | ||
785d3cd2 | 54 | if (addr & 0x3 || in_exception_text(addr)) |
24ba613c AS |
55 | return -EINVAL; |
56 | ||
57 | insn = *p->addr; | |
58 | p->opcode = insn; | |
59 | p->ainsn.insn = tmp_insn; | |
60 | ||
61 | switch (arm_kprobe_decode_insn(insn, &p->ainsn)) { | |
62 | case INSN_REJECTED: /* not supported */ | |
63 | return -EINVAL; | |
64 | ||
65 | case INSN_GOOD: /* instruction uses slot */ | |
66 | p->ainsn.insn = get_insn_slot(); | |
67 | if (!p->ainsn.insn) | |
68 | return -ENOMEM; | |
69 | for (is = 0; is < MAX_INSN_SIZE; ++is) | |
70 | p->ainsn.insn[is] = tmp_insn[is]; | |
8f79ff0c | 71 | flush_insns(p->ainsn.insn, MAX_INSN_SIZE); |
24ba613c AS |
72 | break; |
73 | ||
74 | case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */ | |
75 | p->ainsn.insn = NULL; | |
76 | break; | |
77 | } | |
78 | ||
79 | return 0; | |
80 | } | |
81 | ||
82 | void __kprobes arch_arm_kprobe(struct kprobe *p) | |
83 | { | |
84 | *p->addr = KPROBE_BREAKPOINT_INSTRUCTION; | |
85 | flush_insns(p->addr, 1); | |
86 | } | |
87 | ||
2003b7af FR |
88 | /* |
89 | * The actual disarming is done here on each CPU and synchronized using | |
90 | * stop_machine. This synchronization is necessary on SMP to avoid removing | |
91 | * a probe between the moment the 'Undefined Instruction' exception is raised | |
92 | * and the moment the exception handler reads the faulting instruction from | |
93 | * memory. | |
94 | */ | |
95 | int __kprobes __arch_disarm_kprobe(void *p) | |
96 | { | |
97 | struct kprobe *kp = p; | |
98 | *kp->addr = kp->opcode; | |
99 | flush_insns(kp->addr, 1); | |
100 | return 0; | |
101 | } | |
102 | ||
24ba613c AS |
103 | void __kprobes arch_disarm_kprobe(struct kprobe *p) |
104 | { | |
2003b7af | 105 | stop_machine(__arch_disarm_kprobe, p, &cpu_online_map); |
24ba613c AS |
106 | } |
107 | ||
108 | void __kprobes arch_remove_kprobe(struct kprobe *p) | |
109 | { | |
110 | if (p->ainsn.insn) { | |
24ba613c | 111 | free_insn_slot(p->ainsn.insn, 0); |
24ba613c AS |
112 | p->ainsn.insn = NULL; |
113 | } | |
114 | } | |
115 | ||
116 | static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) | |
117 | { | |
118 | kcb->prev_kprobe.kp = kprobe_running(); | |
119 | kcb->prev_kprobe.status = kcb->kprobe_status; | |
120 | } | |
121 | ||
122 | static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) | |
123 | { | |
124 | __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; | |
125 | kcb->kprobe_status = kcb->prev_kprobe.status; | |
126 | } | |
127 | ||
128 | static void __kprobes set_current_kprobe(struct kprobe *p) | |
129 | { | |
130 | __get_cpu_var(current_kprobe) = p; | |
131 | } | |
132 | ||
133 | static void __kprobes singlestep(struct kprobe *p, struct pt_regs *regs, | |
134 | struct kprobe_ctlblk *kcb) | |
135 | { | |
136 | regs->ARM_pc += 4; | |
137 | p->ainsn.insn_handler(p, regs); | |
138 | } | |
139 | ||
140 | /* | |
141 | * Called with IRQs disabled. IRQs must remain disabled from that point | |
142 | * all the way until processing this kprobe is complete. The current | |
143 | * kprobes implementation cannot process more than one nested level of | |
144 | * kprobe, and that level is reserved for user kprobe handlers, so we can't | |
145 | * risk encountering a new kprobe in an interrupt handler. | |
146 | */ | |
147 | void __kprobes kprobe_handler(struct pt_regs *regs) | |
148 | { | |
149 | struct kprobe *p, *cur; | |
150 | struct kprobe_ctlblk *kcb; | |
151 | kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->ARM_pc; | |
152 | ||
153 | kcb = get_kprobe_ctlblk(); | |
154 | cur = kprobe_running(); | |
155 | p = get_kprobe(addr); | |
156 | ||
157 | if (p) { | |
158 | if (cur) { | |
159 | /* Kprobe is pending, so we're recursing. */ | |
160 | switch (kcb->kprobe_status) { | |
161 | case KPROBE_HIT_ACTIVE: | |
162 | case KPROBE_HIT_SSDONE: | |
163 | /* A pre- or post-handler probe got us here. */ | |
164 | kprobes_inc_nmissed_count(p); | |
165 | save_previous_kprobe(kcb); | |
166 | set_current_kprobe(p); | |
167 | kcb->kprobe_status = KPROBE_REENTER; | |
168 | singlestep(p, regs, kcb); | |
169 | restore_previous_kprobe(kcb); | |
170 | break; | |
171 | default: | |
172 | /* impossible cases */ | |
173 | BUG(); | |
174 | } | |
175 | } else { | |
176 | set_current_kprobe(p); | |
177 | kcb->kprobe_status = KPROBE_HIT_ACTIVE; | |
178 | ||
179 | /* | |
180 | * If we have no pre-handler or it returned 0, we | |
181 | * continue with normal processing. If we have a | |
182 | * pre-handler and it returned non-zero, it prepped | |
183 | * for calling the break_handler below on re-entry, | |
184 | * so get out doing nothing more here. | |
185 | */ | |
186 | if (!p->pre_handler || !p->pre_handler(p, regs)) { | |
187 | kcb->kprobe_status = KPROBE_HIT_SS; | |
188 | singlestep(p, regs, kcb); | |
189 | if (p->post_handler) { | |
190 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
191 | p->post_handler(p, regs, 0); | |
192 | } | |
193 | reset_current_kprobe(); | |
194 | } | |
195 | } | |
196 | } else if (cur) { | |
197 | /* We probably hit a jprobe. Call its break handler. */ | |
198 | if (cur->break_handler && cur->break_handler(cur, regs)) { | |
199 | kcb->kprobe_status = KPROBE_HIT_SS; | |
200 | singlestep(cur, regs, kcb); | |
201 | if (cur->post_handler) { | |
202 | kcb->kprobe_status = KPROBE_HIT_SSDONE; | |
203 | cur->post_handler(cur, regs, 0); | |
204 | } | |
205 | } | |
206 | reset_current_kprobe(); | |
207 | } else { | |
208 | /* | |
209 | * The probe was removed and a race is in progress. | |
210 | * There is nothing we can do about it. Let's restart | |
211 | * the instruction. By the time we can restart, the | |
212 | * real instruction will be there. | |
213 | */ | |
214 | } | |
215 | } | |
216 | ||
3305a607 | 217 | static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr) |
24ba613c | 218 | { |
3305a607 NP |
219 | unsigned long flags; |
220 | local_irq_save(flags); | |
24ba613c | 221 | kprobe_handler(regs); |
3305a607 | 222 | local_irq_restore(flags); |
24ba613c AS |
223 | return 0; |
224 | } | |
225 | ||
226 | int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) | |
227 | { | |
228 | struct kprobe *cur = kprobe_running(); | |
229 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
230 | ||
231 | switch (kcb->kprobe_status) { | |
232 | case KPROBE_HIT_SS: | |
233 | case KPROBE_REENTER: | |
234 | /* | |
235 | * We are here because the instruction being single | |
236 | * stepped caused a page fault. We reset the current | |
237 | * kprobe and the PC to point back to the probe address | |
238 | * and allow the page fault handler to continue as a | |
239 | * normal page fault. | |
240 | */ | |
241 | regs->ARM_pc = (long)cur->addr; | |
242 | if (kcb->kprobe_status == KPROBE_REENTER) { | |
243 | restore_previous_kprobe(kcb); | |
244 | } else { | |
245 | reset_current_kprobe(); | |
246 | } | |
247 | break; | |
248 | ||
249 | case KPROBE_HIT_ACTIVE: | |
250 | case KPROBE_HIT_SSDONE: | |
251 | /* | |
252 | * We increment the nmissed count for accounting, | |
253 | * we can also use npre/npostfault count for accounting | |
254 | * these specific fault cases. | |
255 | */ | |
256 | kprobes_inc_nmissed_count(cur); | |
257 | ||
258 | /* | |
259 | * We come here because instructions in the pre/post | |
260 | * handler caused the page_fault, this could happen | |
261 | * if handler tries to access user space by | |
262 | * copy_from_user(), get_user() etc. Let the | |
263 | * user-specified handler try to fix it. | |
264 | */ | |
265 | if (cur->fault_handler && cur->fault_handler(cur, regs, fsr)) | |
266 | return 1; | |
267 | break; | |
268 | ||
269 | default: | |
270 | break; | |
271 | } | |
272 | ||
273 | return 0; | |
274 | } | |
275 | ||
276 | int __kprobes kprobe_exceptions_notify(struct notifier_block *self, | |
277 | unsigned long val, void *data) | |
278 | { | |
279 | /* | |
280 | * notify_die() is currently never called on ARM, | |
281 | * so this callback is currently empty. | |
282 | */ | |
283 | return NOTIFY_DONE; | |
284 | } | |
285 | ||
286 | /* | |
287 | * When a retprobed function returns, trampoline_handler() is called, | |
288 | * calling the kretprobe's handler. We construct a struct pt_regs to | |
289 | * give a view of registers r0-r11 to the user return-handler. This is | |
290 | * not a complete pt_regs structure, but that should be plenty sufficient | |
291 | * for kretprobe handlers which should normally be interested in r0 only | |
292 | * anyway. | |
293 | */ | |
e0773410 | 294 | void __naked __kprobes kretprobe_trampoline(void) |
24ba613c AS |
295 | { |
296 | __asm__ __volatile__ ( | |
297 | "stmdb sp!, {r0 - r11} \n\t" | |
298 | "mov r0, sp \n\t" | |
299 | "bl trampoline_handler \n\t" | |
300 | "mov lr, r0 \n\t" | |
301 | "ldmia sp!, {r0 - r11} \n\t" | |
302 | "mov pc, lr \n\t" | |
303 | : : : "memory"); | |
304 | } | |
305 | ||
306 | /* Called from kretprobe_trampoline */ | |
307 | static __used __kprobes void *trampoline_handler(struct pt_regs *regs) | |
308 | { | |
309 | struct kretprobe_instance *ri = NULL; | |
310 | struct hlist_head *head, empty_rp; | |
311 | struct hlist_node *node, *tmp; | |
312 | unsigned long flags, orig_ret_address = 0; | |
313 | unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline; | |
314 | ||
315 | INIT_HLIST_HEAD(&empty_rp); | |
ef53d9c5 | 316 | kretprobe_hash_lock(current, &head, &flags); |
24ba613c AS |
317 | |
318 | /* | |
319 | * It is possible to have multiple instances associated with a given | |
320 | * task either because multiple functions in the call path have | |
321 | * a return probe installed on them, and/or more than one return | |
322 | * probe was registered for a target function. | |
323 | * | |
324 | * We can handle this because: | |
325 | * - instances are always inserted at the head of the list | |
326 | * - when multiple return probes are registered for the same | |
327 | * function, the first instance's ret_addr will point to the | |
328 | * real return address, and all the rest will point to | |
329 | * kretprobe_trampoline | |
330 | */ | |
331 | hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { | |
332 | if (ri->task != current) | |
333 | /* another task is sharing our hash bucket */ | |
334 | continue; | |
335 | ||
336 | if (ri->rp && ri->rp->handler) { | |
337 | __get_cpu_var(current_kprobe) = &ri->rp->kp; | |
338 | get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; | |
339 | ri->rp->handler(ri, regs); | |
340 | __get_cpu_var(current_kprobe) = NULL; | |
341 | } | |
342 | ||
343 | orig_ret_address = (unsigned long)ri->ret_addr; | |
344 | recycle_rp_inst(ri, &empty_rp); | |
345 | ||
346 | if (orig_ret_address != trampoline_address) | |
347 | /* | |
348 | * This is the real return address. Any other | |
349 | * instances associated with this task are for | |
350 | * other calls deeper on the call stack | |
351 | */ | |
352 | break; | |
353 | } | |
354 | ||
355 | kretprobe_assert(ri, orig_ret_address, trampoline_address); | |
ef53d9c5 | 356 | kretprobe_hash_unlock(current, &flags); |
24ba613c AS |
357 | |
358 | hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { | |
359 | hlist_del(&ri->hlist); | |
360 | kfree(ri); | |
361 | } | |
362 | ||
363 | return (void *)orig_ret_address; | |
364 | } | |
365 | ||
24ba613c AS |
366 | void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, |
367 | struct pt_regs *regs) | |
368 | { | |
369 | ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr; | |
370 | ||
371 | /* Replace the return addr with trampoline addr. */ | |
372 | regs->ARM_lr = (unsigned long)&kretprobe_trampoline; | |
373 | } | |
374 | ||
375 | int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) | |
376 | { | |
377 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
378 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
379 | long sp_addr = regs->ARM_sp; | |
380 | ||
381 | kcb->jprobe_saved_regs = *regs; | |
382 | memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr)); | |
383 | regs->ARM_pc = (long)jp->entry; | |
384 | regs->ARM_cpsr |= PSR_I_BIT; | |
385 | preempt_disable(); | |
386 | return 1; | |
387 | } | |
388 | ||
389 | void __kprobes jprobe_return(void) | |
390 | { | |
391 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
392 | ||
393 | __asm__ __volatile__ ( | |
394 | /* | |
395 | * Setup an empty pt_regs. Fill SP and PC fields as | |
396 | * they're needed by longjmp_break_handler. | |
397 | */ | |
398 | "sub sp, %0, %1 \n\t" | |
399 | "ldr r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t" | |
400 | "str %0, [sp, %2] \n\t" | |
401 | "str r0, [sp, %3] \n\t" | |
402 | "mov r0, sp \n\t" | |
403 | "bl kprobe_handler \n\t" | |
404 | ||
405 | /* | |
406 | * Return to the context saved by setjmp_pre_handler | |
407 | * and restored by longjmp_break_handler. | |
408 | */ | |
409 | "ldr r0, [sp, %4] \n\t" | |
410 | "msr cpsr_cxsf, r0 \n\t" | |
411 | "ldmia sp, {r0 - pc} \n\t" | |
412 | : | |
413 | : "r" (kcb->jprobe_saved_regs.ARM_sp), | |
414 | "I" (sizeof(struct pt_regs)), | |
415 | "J" (offsetof(struct pt_regs, ARM_sp)), | |
416 | "J" (offsetof(struct pt_regs, ARM_pc)), | |
417 | "J" (offsetof(struct pt_regs, ARM_cpsr)) | |
418 | : "memory", "cc"); | |
419 | } | |
420 | ||
421 | int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) | |
422 | { | |
423 | struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); | |
424 | long stack_addr = kcb->jprobe_saved_regs.ARM_sp; | |
425 | long orig_sp = regs->ARM_sp; | |
426 | struct jprobe *jp = container_of(p, struct jprobe, kp); | |
427 | ||
428 | if (regs->ARM_pc == JPROBE_MAGIC_ADDR) { | |
429 | if (orig_sp != stack_addr) { | |
430 | struct pt_regs *saved_regs = | |
431 | (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp; | |
432 | printk("current sp %lx does not match saved sp %lx\n", | |
433 | orig_sp, stack_addr); | |
434 | printk("Saved registers for jprobe %p\n", jp); | |
435 | show_regs(saved_regs); | |
436 | printk("Current registers\n"); | |
437 | show_regs(regs); | |
438 | BUG(); | |
439 | } | |
440 | *regs = kcb->jprobe_saved_regs; | |
441 | memcpy((void *)stack_addr, kcb->jprobes_stack, | |
442 | MIN_STACK_SIZE(stack_addr)); | |
443 | preempt_enable_no_resched(); | |
444 | return 1; | |
445 | } | |
446 | return 0; | |
447 | } | |
448 | ||
b24061fa NP |
449 | int __kprobes arch_trampoline_kprobe(struct kprobe *p) |
450 | { | |
451 | return 0; | |
452 | } | |
453 | ||
24ba613c AS |
454 | static struct undef_hook kprobes_break_hook = { |
455 | .instr_mask = 0xffffffff, | |
456 | .instr_val = KPROBE_BREAKPOINT_INSTRUCTION, | |
457 | .cpsr_mask = MODE_MASK, | |
458 | .cpsr_val = SVC_MODE, | |
459 | .fn = kprobe_trap_handler, | |
460 | }; | |
461 | ||
462 | int __init arch_init_kprobes() | |
463 | { | |
464 | arm_kprobe_decode_init(); | |
465 | register_undef_hook(&kprobes_break_hook); | |
466 | return 0; | |
467 | } |