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22#include <linux/kernel.h>
23#include <linux/kprobes.h>
24#include <linux/module.h>
25#include <linux/slab.h>
26#include <linux/stop_machine.h>
27#include <linux/stringify.h>
28#include <asm/traps.h>
29#include <asm/opcodes.h>
30#include <asm/cacheflush.h>
31#include <linux/percpu.h>
32#include <linux/bug.h>
33#include <asm/patch.h>
34
35#include "../decode-arm.h"
36#include "../decode-thumb.h"
37#include "core.h"
38
39#define MIN_STACK_SIZE(addr) \
40 min((unsigned long)MAX_STACK_SIZE, \
41 (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
42
43#define flush_insns(addr, size) \
44 flush_icache_range((unsigned long)(addr), \
45 (unsigned long)(addr) + \
46 (size))
47
48
49#define JPROBE_MAGIC_ADDR 0xffffffff
50
51DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
52DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
53
54
55int __kprobes arch_prepare_kprobe(struct kprobe *p)
56{
57 kprobe_opcode_t insn;
58 kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
59 unsigned long addr = (unsigned long)p->addr;
60 bool thumb;
61 kprobe_decode_insn_t *decode_insn;
62 const union decode_action *actions;
63 int is;
64 const struct decode_checker **checkers;
65
66 if (in_exception_text(addr))
67 return -EINVAL;
68
69#ifdef CONFIG_THUMB2_KERNEL
70 thumb = true;
71 addr &= ~1;
72 insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
73 if (is_wide_instruction(insn)) {
74 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
75 insn = __opcode_thumb32_compose(insn, inst2);
76 decode_insn = thumb32_probes_decode_insn;
77 actions = kprobes_t32_actions;
78 checkers = kprobes_t32_checkers;
79 } else {
80 decode_insn = thumb16_probes_decode_insn;
81 actions = kprobes_t16_actions;
82 checkers = kprobes_t16_checkers;
83 }
84#else
85 thumb = false;
86 if (addr & 0x3)
87 return -EINVAL;
88 insn = __mem_to_opcode_arm(*p->addr);
89 decode_insn = arm_probes_decode_insn;
90 actions = kprobes_arm_actions;
91 checkers = kprobes_arm_checkers;
92#endif
93
94 p->opcode = insn;
95 p->ainsn.insn = tmp_insn;
96
97 switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
98 case INSN_REJECTED:
99 return -EINVAL;
100
101 case INSN_GOOD:
102 p->ainsn.insn = get_insn_slot();
103 if (!p->ainsn.insn)
104 return -ENOMEM;
105 for (is = 0; is < MAX_INSN_SIZE; ++is)
106 p->ainsn.insn[is] = tmp_insn[is];
107 flush_insns(p->ainsn.insn,
108 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
109 p->ainsn.insn_fn = (probes_insn_fn_t *)
110 ((uintptr_t)p->ainsn.insn | thumb);
111 break;
112
113 case INSN_GOOD_NO_SLOT:
114 p->ainsn.insn = NULL;
115 break;
116 }
117
118
119
120
121
122
123 if ((p->ainsn.stack_space < 0) ||
124 (p->ainsn.stack_space > MAX_STACK_SIZE))
125 return -EINVAL;
126
127 return 0;
128}
129
130void __kprobes arch_arm_kprobe(struct kprobe *p)
131{
132 unsigned int brkp;
133 void *addr;
134
135 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
136
137 addr = (void *)((uintptr_t)p->addr & ~1);
138
139 if (is_wide_instruction(p->opcode))
140 brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
141 else
142 brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
143 } else {
144 kprobe_opcode_t insn = p->opcode;
145
146 addr = p->addr;
147 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
148
149 if (insn >= 0xe0000000)
150 brkp |= 0xe0000000;
151 else
152 brkp |= insn & 0xf0000000;
153 }
154
155 patch_text(addr, brkp);
156}
157
158
159
160
161
162
163
164
165
166struct patch {
167 void *addr;
168 unsigned int insn;
169};
170
171static int __kprobes_remove_breakpoint(void *data)
172{
173 struct patch *p = data;
174 __patch_text(p->addr, p->insn);
175 return 0;
176}
177
178void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
179{
180 struct patch p = {
181 .addr = addr,
182 .insn = insn,
183 };
184 stop_machine(__kprobes_remove_breakpoint, &p, cpu_online_mask);
185}
186
187void __kprobes arch_disarm_kprobe(struct kprobe *p)
188{
189 kprobes_remove_breakpoint((void *)((uintptr_t)p->addr & ~1),
190 p->opcode);
191}
192
193void __kprobes arch_remove_kprobe(struct kprobe *p)
194{
195 if (p->ainsn.insn) {
196 free_insn_slot(p->ainsn.insn, 0);
197 p->ainsn.insn = NULL;
198 }
199}
200
201static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
202{
203 kcb->prev_kprobe.kp = kprobe_running();
204 kcb->prev_kprobe.status = kcb->kprobe_status;
205}
206
207static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
208{
209 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
210 kcb->kprobe_status = kcb->prev_kprobe.status;
211}
212
213static void __kprobes set_current_kprobe(struct kprobe *p)
214{
215 __this_cpu_write(current_kprobe, p);
216}
217
218static void __kprobes
219singlestep_skip(struct kprobe *p, struct pt_regs *regs)
220{
221#ifdef CONFIG_THUMB2_KERNEL
222 regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
223 if (is_wide_instruction(p->opcode))
224 regs->ARM_pc += 4;
225 else
226 regs->ARM_pc += 2;
227#else
228 regs->ARM_pc += 4;
229#endif
230}
231
232static inline void __kprobes
233singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
234{
235 p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
236}
237
238
239
240
241
242
243
244
245void __kprobes kprobe_handler(struct pt_regs *regs)
246{
247 struct kprobe *p, *cur;
248 struct kprobe_ctlblk *kcb;
249
250 kcb = get_kprobe_ctlblk();
251 cur = kprobe_running();
252
253#ifdef CONFIG_THUMB2_KERNEL
254
255
256
257
258
259 p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
260 if (!p)
261 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
262
263#else
264 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
265#endif
266
267 if (p) {
268 if (cur) {
269
270 switch (kcb->kprobe_status) {
271 case KPROBE_HIT_ACTIVE:
272 case KPROBE_HIT_SSDONE:
273
274 kprobes_inc_nmissed_count(p);
275 save_previous_kprobe(kcb);
276 set_current_kprobe(p);
277 kcb->kprobe_status = KPROBE_REENTER;
278 singlestep(p, regs, kcb);
279 restore_previous_kprobe(kcb);
280 break;
281 default:
282
283 BUG();
284 }
285 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
286
287 set_current_kprobe(p);
288 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
289
290
291
292
293
294
295
296
297 if (!p->pre_handler || !p->pre_handler(p, regs)) {
298 kcb->kprobe_status = KPROBE_HIT_SS;
299 singlestep(p, regs, kcb);
300 if (p->post_handler) {
301 kcb->kprobe_status = KPROBE_HIT_SSDONE;
302 p->post_handler(p, regs, 0);
303 }
304 reset_current_kprobe();
305 }
306 } else {
307
308
309
310
311
312 singlestep_skip(p, regs);
313 }
314 } else if (cur) {
315
316 if (cur->break_handler && cur->break_handler(cur, regs)) {
317 kcb->kprobe_status = KPROBE_HIT_SS;
318 singlestep(cur, regs, kcb);
319 if (cur->post_handler) {
320 kcb->kprobe_status = KPROBE_HIT_SSDONE;
321 cur->post_handler(cur, regs, 0);
322 }
323 }
324 reset_current_kprobe();
325 } else {
326
327
328
329
330
331
332 }
333}
334
335static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
336{
337 unsigned long flags;
338 local_irq_save(flags);
339 kprobe_handler(regs);
340 local_irq_restore(flags);
341 return 0;
342}
343
344int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
345{
346 struct kprobe *cur = kprobe_running();
347 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
348
349 switch (kcb->kprobe_status) {
350 case KPROBE_HIT_SS:
351 case KPROBE_REENTER:
352
353
354
355
356
357
358
359 regs->ARM_pc = (long)cur->addr;
360 if (kcb->kprobe_status == KPROBE_REENTER) {
361 restore_previous_kprobe(kcb);
362 } else {
363 reset_current_kprobe();
364 }
365 break;
366
367 case KPROBE_HIT_ACTIVE:
368 case KPROBE_HIT_SSDONE:
369
370
371
372
373
374 kprobes_inc_nmissed_count(cur);
375
376
377
378
379
380
381
382
383 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
384 return 1;
385 break;
386
387 default:
388 break;
389 }
390
391 return 0;
392}
393
394int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
395 unsigned long val, void *data)
396{
397
398
399
400
401 return NOTIFY_DONE;
402}
403
404
405
406
407
408
409
410
411
412void __naked __kprobes kretprobe_trampoline(void)
413{
414 __asm__ __volatile__ (
415 "stmdb sp!, {r0 - r11} \n\t"
416 "mov r0, sp \n\t"
417 "bl trampoline_handler \n\t"
418 "mov lr, r0 \n\t"
419 "ldmia sp!, {r0 - r11} \n\t"
420#ifdef CONFIG_THUMB2_KERNEL
421 "bx lr \n\t"
422#else
423 "mov pc, lr \n\t"
424#endif
425 : : : "memory");
426}
427
428
429static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
430{
431 struct kretprobe_instance *ri = NULL;
432 struct hlist_head *head, empty_rp;
433 struct hlist_node *tmp;
434 unsigned long flags, orig_ret_address = 0;
435 unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
436
437 INIT_HLIST_HEAD(&empty_rp);
438 kretprobe_hash_lock(current, &head, &flags);
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
454 if (ri->task != current)
455
456 continue;
457
458 if (ri->rp && ri->rp->handler) {
459 __this_cpu_write(current_kprobe, &ri->rp->kp);
460 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
461 ri->rp->handler(ri, regs);
462 __this_cpu_write(current_kprobe, NULL);
463 }
464
465 orig_ret_address = (unsigned long)ri->ret_addr;
466 recycle_rp_inst(ri, &empty_rp);
467
468 if (orig_ret_address != trampoline_address)
469
470
471
472
473
474 break;
475 }
476
477 kretprobe_assert(ri, orig_ret_address, trampoline_address);
478 kretprobe_hash_unlock(current, &flags);
479
480 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
481 hlist_del(&ri->hlist);
482 kfree(ri);
483 }
484
485 return (void *)orig_ret_address;
486}
487
488void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
489 struct pt_regs *regs)
490{
491 ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
492
493
494 regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
495}
496
497int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
498{
499 struct jprobe *jp = container_of(p, struct jprobe, kp);
500 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
501 long sp_addr = regs->ARM_sp;
502 long cpsr;
503
504 kcb->jprobe_saved_regs = *regs;
505 memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
506 regs->ARM_pc = (long)jp->entry;
507
508 cpsr = regs->ARM_cpsr | PSR_I_BIT;
509#ifdef CONFIG_THUMB2_KERNEL
510
511 if (regs->ARM_pc & 1)
512 cpsr |= PSR_T_BIT;
513 else
514 cpsr &= ~PSR_T_BIT;
515#endif
516 regs->ARM_cpsr = cpsr;
517
518 preempt_disable();
519 return 1;
520}
521
522void __kprobes jprobe_return(void)
523{
524 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
525
526 __asm__ __volatile__ (
527
528
529
530
531
532
533
534
535
536
537
538
539#ifdef CONFIG_THUMB2_KERNEL
540 "sub r0, %0, %1 \n\t"
541 "mov sp, r0 \n\t"
542#else
543 "sub sp, %0, %1 \n\t"
544#endif
545 "ldr r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
546 "str %0, [sp, %2] \n\t"
547 "str r0, [sp, %3] \n\t"
548 "mov r0, sp \n\t"
549 "bl kprobe_handler \n\t"
550
551
552
553
554
555#ifdef CONFIG_THUMB2_KERNEL
556 "ldr lr, [sp, %2] \n\t"
557 "ldrd r0, r1, [sp, %5] \n\t"
558 "ldr r2, [sp, %4] \n\t"
559 "stmdb lr!, {r0, r1, r2} \n\t"
560
561 "ldmia sp, {r0 - r12} \n\t"
562 "mov sp, lr \n\t"
563 "ldr lr, [sp], #4 \n\t"
564 "rfeia sp! \n\t"
565#else
566 "ldr r0, [sp, %4] \n\t"
567 "msr cpsr_cxsf, r0 \n\t"
568 "ldmia sp, {r0 - pc} \n\t"
569#endif
570 :
571 : "r" (kcb->jprobe_saved_regs.ARM_sp),
572 "I" (sizeof(struct pt_regs) * 2),
573 "J" (offsetof(struct pt_regs, ARM_sp)),
574 "J" (offsetof(struct pt_regs, ARM_pc)),
575 "J" (offsetof(struct pt_regs, ARM_cpsr)),
576 "J" (offsetof(struct pt_regs, ARM_lr))
577 : "memory", "cc");
578}
579
580int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
581{
582 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
583 long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
584 long orig_sp = regs->ARM_sp;
585 struct jprobe *jp = container_of(p, struct jprobe, kp);
586
587 if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
588 if (orig_sp != stack_addr) {
589 struct pt_regs *saved_regs =
590 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
591 printk("current sp %lx does not match saved sp %lx\n",
592 orig_sp, stack_addr);
593 printk("Saved registers for jprobe %p\n", jp);
594 show_regs(saved_regs);
595 printk("Current registers\n");
596 show_regs(regs);
597 BUG();
598 }
599 *regs = kcb->jprobe_saved_regs;
600 memcpy((void *)stack_addr, kcb->jprobes_stack,
601 MIN_STACK_SIZE(stack_addr));
602 preempt_enable_no_resched();
603 return 1;
604 }
605 return 0;
606}
607
608int __kprobes arch_trampoline_kprobe(struct kprobe *p)
609{
610 return 0;
611}
612
613#ifdef CONFIG_THUMB2_KERNEL
614
615static struct undef_hook kprobes_thumb16_break_hook = {
616 .instr_mask = 0xffff,
617 .instr_val = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
618 .cpsr_mask = MODE_MASK,
619 .cpsr_val = SVC_MODE,
620 .fn = kprobe_trap_handler,
621};
622
623static struct undef_hook kprobes_thumb32_break_hook = {
624 .instr_mask = 0xffffffff,
625 .instr_val = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
626 .cpsr_mask = MODE_MASK,
627 .cpsr_val = SVC_MODE,
628 .fn = kprobe_trap_handler,
629};
630
631#else
632
633static struct undef_hook kprobes_arm_break_hook = {
634 .instr_mask = 0x0fffffff,
635 .instr_val = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
636 .cpsr_mask = MODE_MASK,
637 .cpsr_val = SVC_MODE,
638 .fn = kprobe_trap_handler,
639};
640
641#endif
642
643int __init arch_init_kprobes()
644{
645 arm_probes_decode_init();
646#ifdef CONFIG_THUMB2_KERNEL
647 register_undef_hook(&kprobes_thumb16_break_hook);
648 register_undef_hook(&kprobes_thumb32_break_hook);
649#else
650 register_undef_hook(&kprobes_arm_break_hook);
651#endif
652 return 0;
653}
654