Merge tag 'dma-mapping-4.20-2' of git://git.infradead.org/users/hch/dma-mapping
[muen/linux.git] / arch / arm64 / kernel / probes / kprobes.c
1 /*
2  * arch/arm64/kernel/probes/kprobes.c
3  *
4  * Kprobes support for ARM64
5  *
6  * Copyright (C) 2013 Linaro Limited.
7  * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2 as
11  * published by the Free Software Foundation.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16  * General Public License for more details.
17  *
18  */
19 #include <linux/kasan.h>
20 #include <linux/kernel.h>
21 #include <linux/kprobes.h>
22 #include <linux/extable.h>
23 #include <linux/slab.h>
24 #include <linux/stop_machine.h>
25 #include <linux/sched/debug.h>
26 #include <linux/stringify.h>
27 #include <asm/traps.h>
28 #include <asm/ptrace.h>
29 #include <asm/cacheflush.h>
30 #include <asm/debug-monitors.h>
31 #include <asm/system_misc.h>
32 #include <asm/insn.h>
33 #include <linux/uaccess.h>
34 #include <asm/irq.h>
35 #include <asm/sections.h>
36
37 #include "decode-insn.h"
38
39 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
40 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
41
42 static void __kprobes
43 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
44
45 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
46 {
47         /* prepare insn slot */
48         p->ainsn.api.insn[0] = cpu_to_le32(p->opcode);
49
50         flush_icache_range((uintptr_t) (p->ainsn.api.insn),
51                            (uintptr_t) (p->ainsn.api.insn) +
52                            MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
53
54         /*
55          * Needs restoring of return address after stepping xol.
56          */
57         p->ainsn.api.restore = (unsigned long) p->addr +
58           sizeof(kprobe_opcode_t);
59 }
60
61 static void __kprobes arch_prepare_simulate(struct kprobe *p)
62 {
63         /* This instructions is not executed xol. No need to adjust the PC */
64         p->ainsn.api.restore = 0;
65 }
66
67 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
68 {
69         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
70
71         if (p->ainsn.api.handler)
72                 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs);
73
74         /* single step simulated, now go for post processing */
75         post_kprobe_handler(kcb, regs);
76 }
77
78 int __kprobes arch_prepare_kprobe(struct kprobe *p)
79 {
80         unsigned long probe_addr = (unsigned long)p->addr;
81         extern char __start_rodata[];
82         extern char __end_rodata[];
83
84         if (probe_addr & 0x3)
85                 return -EINVAL;
86
87         /* copy instruction */
88         p->opcode = le32_to_cpu(*p->addr);
89
90         if (in_exception_text(probe_addr))
91                 return -EINVAL;
92         if (probe_addr >= (unsigned long) __start_rodata &&
93             probe_addr <= (unsigned long) __end_rodata)
94                 return -EINVAL;
95
96         /* decode instruction */
97         switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
98         case INSN_REJECTED:     /* insn not supported */
99                 return -EINVAL;
100
101         case INSN_GOOD_NO_SLOT: /* insn need simulation */
102                 p->ainsn.api.insn = NULL;
103                 break;
104
105         case INSN_GOOD: /* instruction uses slot */
106                 p->ainsn.api.insn = get_insn_slot();
107                 if (!p->ainsn.api.insn)
108                         return -ENOMEM;
109                 break;
110         }
111
112         /* prepare the instruction */
113         if (p->ainsn.api.insn)
114                 arch_prepare_ss_slot(p);
115         else
116                 arch_prepare_simulate(p);
117
118         return 0;
119 }
120
121 static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
122 {
123         void *addrs[1];
124         u32 insns[1];
125
126         addrs[0] = (void *)addr;
127         insns[0] = (u32)opcode;
128
129         return aarch64_insn_patch_text(addrs, insns, 1);
130 }
131
132 /* arm kprobe: install breakpoint in text */
133 void __kprobes arch_arm_kprobe(struct kprobe *p)
134 {
135         patch_text(p->addr, BRK64_OPCODE_KPROBES);
136 }
137
138 /* disarm kprobe: remove breakpoint from text */
139 void __kprobes arch_disarm_kprobe(struct kprobe *p)
140 {
141         patch_text(p->addr, p->opcode);
142 }
143
144 void __kprobes arch_remove_kprobe(struct kprobe *p)
145 {
146         if (p->ainsn.api.insn) {
147                 free_insn_slot(p->ainsn.api.insn, 0);
148                 p->ainsn.api.insn = NULL;
149         }
150 }
151
152 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
153 {
154         kcb->prev_kprobe.kp = kprobe_running();
155         kcb->prev_kprobe.status = kcb->kprobe_status;
156 }
157
158 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
159 {
160         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
161         kcb->kprobe_status = kcb->prev_kprobe.status;
162 }
163
164 static void __kprobes set_current_kprobe(struct kprobe *p)
165 {
166         __this_cpu_write(current_kprobe, p);
167 }
168
169 /*
170  * When PSTATE.D is set (masked), then software step exceptions can not be
171  * generated.
172  * SPSR's D bit shows the value of PSTATE.D immediately before the
173  * exception was taken. PSTATE.D is set while entering into any exception
174  * mode, however software clears it for any normal (none-debug-exception)
175  * mode in the exception entry. Therefore, when we are entering into kprobe
176  * breakpoint handler from any normal mode then SPSR.D bit is already
177  * cleared, however it is set when we are entering from any debug exception
178  * mode.
179  * Since we always need to generate single step exception after a kprobe
180  * breakpoint exception therefore we need to clear it unconditionally, when
181  * we become sure that the current breakpoint exception is for kprobe.
182  */
183 static void __kprobes
184 spsr_set_debug_flag(struct pt_regs *regs, int mask)
185 {
186         unsigned long spsr = regs->pstate;
187
188         if (mask)
189                 spsr |= PSR_D_BIT;
190         else
191                 spsr &= ~PSR_D_BIT;
192
193         regs->pstate = spsr;
194 }
195
196 /*
197  * Interrupts need to be disabled before single-step mode is set, and not
198  * reenabled until after single-step mode ends.
199  * Without disabling interrupt on local CPU, there is a chance of
200  * interrupt occurrence in the period of exception return and  start of
201  * out-of-line single-step, that result in wrongly single stepping
202  * into the interrupt handler.
203  */
204 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
205                                                 struct pt_regs *regs)
206 {
207         kcb->saved_irqflag = regs->pstate;
208         regs->pstate |= PSR_I_BIT;
209 }
210
211 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
212                                                 struct pt_regs *regs)
213 {
214         if (kcb->saved_irqflag & PSR_I_BIT)
215                 regs->pstate |= PSR_I_BIT;
216         else
217                 regs->pstate &= ~PSR_I_BIT;
218 }
219
220 static void __kprobes
221 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr)
222 {
223         kcb->ss_ctx.ss_pending = true;
224         kcb->ss_ctx.match_addr = addr + sizeof(kprobe_opcode_t);
225 }
226
227 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
228 {
229         kcb->ss_ctx.ss_pending = false;
230         kcb->ss_ctx.match_addr = 0;
231 }
232
233 static void __kprobes setup_singlestep(struct kprobe *p,
234                                        struct pt_regs *regs,
235                                        struct kprobe_ctlblk *kcb, int reenter)
236 {
237         unsigned long slot;
238
239         if (reenter) {
240                 save_previous_kprobe(kcb);
241                 set_current_kprobe(p);
242                 kcb->kprobe_status = KPROBE_REENTER;
243         } else {
244                 kcb->kprobe_status = KPROBE_HIT_SS;
245         }
246
247
248         if (p->ainsn.api.insn) {
249                 /* prepare for single stepping */
250                 slot = (unsigned long)p->ainsn.api.insn;
251
252                 set_ss_context(kcb, slot);      /* mark pending ss */
253
254                 spsr_set_debug_flag(regs, 0);
255
256                 /* IRQs and single stepping do not mix well. */
257                 kprobes_save_local_irqflag(kcb, regs);
258                 kernel_enable_single_step(regs);
259                 instruction_pointer_set(regs, slot);
260         } else {
261                 /* insn simulation */
262                 arch_simulate_insn(p, regs);
263         }
264 }
265
266 static int __kprobes reenter_kprobe(struct kprobe *p,
267                                     struct pt_regs *regs,
268                                     struct kprobe_ctlblk *kcb)
269 {
270         switch (kcb->kprobe_status) {
271         case KPROBE_HIT_SSDONE:
272         case KPROBE_HIT_ACTIVE:
273                 kprobes_inc_nmissed_count(p);
274                 setup_singlestep(p, regs, kcb, 1);
275                 break;
276         case KPROBE_HIT_SS:
277         case KPROBE_REENTER:
278                 pr_warn("Unrecoverable kprobe detected.\n");
279                 dump_kprobe(p);
280                 BUG();
281                 break;
282         default:
283                 WARN_ON(1);
284                 return 0;
285         }
286
287         return 1;
288 }
289
290 static void __kprobes
291 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
292 {
293         struct kprobe *cur = kprobe_running();
294
295         if (!cur)
296                 return;
297
298         /* return addr restore if non-branching insn */
299         if (cur->ainsn.api.restore != 0)
300                 instruction_pointer_set(regs, cur->ainsn.api.restore);
301
302         /* restore back original saved kprobe variables and continue */
303         if (kcb->kprobe_status == KPROBE_REENTER) {
304                 restore_previous_kprobe(kcb);
305                 return;
306         }
307         /* call post handler */
308         kcb->kprobe_status = KPROBE_HIT_SSDONE;
309         if (cur->post_handler)  {
310                 /* post_handler can hit breakpoint and single step
311                  * again, so we enable D-flag for recursive exception.
312                  */
313                 cur->post_handler(cur, regs, 0);
314         }
315
316         reset_current_kprobe();
317 }
318
319 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
320 {
321         struct kprobe *cur = kprobe_running();
322         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
323
324         switch (kcb->kprobe_status) {
325         case KPROBE_HIT_SS:
326         case KPROBE_REENTER:
327                 /*
328                  * We are here because the instruction being single
329                  * stepped caused a page fault. We reset the current
330                  * kprobe and the ip points back to the probe address
331                  * and allow the page fault handler to continue as a
332                  * normal page fault.
333                  */
334                 instruction_pointer_set(regs, (unsigned long) cur->addr);
335                 if (!instruction_pointer(regs))
336                         BUG();
337
338                 kernel_disable_single_step();
339
340                 if (kcb->kprobe_status == KPROBE_REENTER)
341                         restore_previous_kprobe(kcb);
342                 else
343                         reset_current_kprobe();
344
345                 break;
346         case KPROBE_HIT_ACTIVE:
347         case KPROBE_HIT_SSDONE:
348                 /*
349                  * We increment the nmissed count for accounting,
350                  * we can also use npre/npostfault count for accounting
351                  * these specific fault cases.
352                  */
353                 kprobes_inc_nmissed_count(cur);
354
355                 /*
356                  * We come here because instructions in the pre/post
357                  * handler caused the page_fault, this could happen
358                  * if handler tries to access user space by
359                  * copy_from_user(), get_user() etc. Let the
360                  * user-specified handler try to fix it first.
361                  */
362                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
363                         return 1;
364
365                 /*
366                  * In case the user-specified fault handler returned
367                  * zero, try to fix up.
368                  */
369                 if (fixup_exception(regs))
370                         return 1;
371         }
372         return 0;
373 }
374
375 static void __kprobes kprobe_handler(struct pt_regs *regs)
376 {
377         struct kprobe *p, *cur_kprobe;
378         struct kprobe_ctlblk *kcb;
379         unsigned long addr = instruction_pointer(regs);
380
381         kcb = get_kprobe_ctlblk();
382         cur_kprobe = kprobe_running();
383
384         p = get_kprobe((kprobe_opcode_t *) addr);
385
386         if (p) {
387                 if (cur_kprobe) {
388                         if (reenter_kprobe(p, regs, kcb))
389                                 return;
390                 } else {
391                         /* Probe hit */
392                         set_current_kprobe(p);
393                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
394
395                         /*
396                          * If we have no pre-handler or it returned 0, we
397                          * continue with normal processing.  If we have a
398                          * pre-handler and it returned non-zero, it will
399                          * modify the execution path and no need to single
400                          * stepping. Let's just reset current kprobe and exit.
401                          *
402                          * pre_handler can hit a breakpoint and can step thru
403                          * before return, keep PSTATE D-flag enabled until
404                          * pre_handler return back.
405                          */
406                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
407                                 setup_singlestep(p, regs, kcb, 0);
408                         } else
409                                 reset_current_kprobe();
410                 }
411         }
412         /*
413          * The breakpoint instruction was removed right
414          * after we hit it.  Another cpu has removed
415          * either a probepoint or a debugger breakpoint
416          * at this address.  In either case, no further
417          * handling of this interrupt is appropriate.
418          * Return back to original instruction, and continue.
419          */
420 }
421
422 static int __kprobes
423 kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
424 {
425         if ((kcb->ss_ctx.ss_pending)
426             && (kcb->ss_ctx.match_addr == addr)) {
427                 clear_ss_context(kcb);  /* clear pending ss */
428                 return DBG_HOOK_HANDLED;
429         }
430         /* not ours, kprobes should ignore it */
431         return DBG_HOOK_ERROR;
432 }
433
434 int __kprobes
435 kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
436 {
437         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
438         int retval;
439
440         /* return error if this is not our step */
441         retval = kprobe_ss_hit(kcb, instruction_pointer(regs));
442
443         if (retval == DBG_HOOK_HANDLED) {
444                 kprobes_restore_local_irqflag(kcb, regs);
445                 kernel_disable_single_step();
446
447                 post_kprobe_handler(kcb, regs);
448         }
449
450         return retval;
451 }
452
453 int __kprobes
454 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
455 {
456         kprobe_handler(regs);
457         return DBG_HOOK_HANDLED;
458 }
459
460 bool arch_within_kprobe_blacklist(unsigned long addr)
461 {
462         if ((addr >= (unsigned long)__kprobes_text_start &&
463             addr < (unsigned long)__kprobes_text_end) ||
464             (addr >= (unsigned long)__entry_text_start &&
465             addr < (unsigned long)__entry_text_end) ||
466             (addr >= (unsigned long)__idmap_text_start &&
467             addr < (unsigned long)__idmap_text_end) ||
468             !!search_exception_tables(addr))
469                 return true;
470
471         if (!is_kernel_in_hyp_mode()) {
472                 if ((addr >= (unsigned long)__hyp_text_start &&
473                     addr < (unsigned long)__hyp_text_end) ||
474                     (addr >= (unsigned long)__hyp_idmap_text_start &&
475                     addr < (unsigned long)__hyp_idmap_text_end))
476                         return true;
477         }
478
479         return false;
480 }
481
482 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
483 {
484         struct kretprobe_instance *ri = NULL;
485         struct hlist_head *head, empty_rp;
486         struct hlist_node *tmp;
487         unsigned long flags, orig_ret_address = 0;
488         unsigned long trampoline_address =
489                 (unsigned long)&kretprobe_trampoline;
490         kprobe_opcode_t *correct_ret_addr = NULL;
491
492         INIT_HLIST_HEAD(&empty_rp);
493         kretprobe_hash_lock(current, &head, &flags);
494
495         /*
496          * It is possible to have multiple instances associated with a given
497          * task either because multiple functions in the call path have
498          * return probes installed on them, and/or more than one
499          * return probe was registered for a target function.
500          *
501          * We can handle this because:
502          *     - instances are always pushed into the head of the list
503          *     - when multiple return probes are registered for the same
504          *       function, the (chronologically) first instance's ret_addr
505          *       will be the real return address, and all the rest will
506          *       point to kretprobe_trampoline.
507          */
508         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
509                 if (ri->task != current)
510                         /* another task is sharing our hash bucket */
511                         continue;
512
513                 orig_ret_address = (unsigned long)ri->ret_addr;
514
515                 if (orig_ret_address != trampoline_address)
516                         /*
517                          * This is the real return address. Any other
518                          * instances associated with this task are for
519                          * other calls deeper on the call stack
520                          */
521                         break;
522         }
523
524         kretprobe_assert(ri, orig_ret_address, trampoline_address);
525
526         correct_ret_addr = ri->ret_addr;
527         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
528                 if (ri->task != current)
529                         /* another task is sharing our hash bucket */
530                         continue;
531
532                 orig_ret_address = (unsigned long)ri->ret_addr;
533                 if (ri->rp && ri->rp->handler) {
534                         __this_cpu_write(current_kprobe, &ri->rp->kp);
535                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
536                         ri->ret_addr = correct_ret_addr;
537                         ri->rp->handler(ri, regs);
538                         __this_cpu_write(current_kprobe, NULL);
539                 }
540
541                 recycle_rp_inst(ri, &empty_rp);
542
543                 if (orig_ret_address != trampoline_address)
544                         /*
545                          * This is the real return address. Any other
546                          * instances associated with this task are for
547                          * other calls deeper on the call stack
548                          */
549                         break;
550         }
551
552         kretprobe_hash_unlock(current, &flags);
553
554         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
555                 hlist_del(&ri->hlist);
556                 kfree(ri);
557         }
558         return (void *)orig_ret_address;
559 }
560
561 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
562                                       struct pt_regs *regs)
563 {
564         ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
565
566         /* replace return addr (x30) with trampoline */
567         regs->regs[30] = (long)&kretprobe_trampoline;
568 }
569
570 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
571 {
572         return 0;
573 }
574
575 int __init arch_init_kprobes(void)
576 {
577         return 0;
578 }