GNU Linux-libre 4.19.314-gnu1
[releases.git] / arch / arc / kernel / kprobes.c
1 /*
2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8
9 #include <linux/types.h>
10 #include <linux/kprobes.h>
11 #include <linux/slab.h>
12 #include <linux/module.h>
13 #include <linux/kdebug.h>
14 #include <linux/sched.h>
15 #include <linux/uaccess.h>
16 #include <asm/cacheflush.h>
17 #include <asm/current.h>
18 #include <asm/disasm.h>
19
20 #define MIN_STACK_SIZE(addr)    min((unsigned long)MAX_STACK_SIZE, \
21                 (unsigned long)current_thread_info() + THREAD_SIZE - (addr))
22
23 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
24 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
25
26 int __kprobes arch_prepare_kprobe(struct kprobe *p)
27 {
28         /* Attempt to probe at unaligned address */
29         if ((unsigned long)p->addr & 0x01)
30                 return -EINVAL;
31
32         /* Address should not be in exception handling code */
33
34         p->ainsn.is_short = is_short_instr((unsigned long)p->addr);
35         p->opcode = *p->addr;
36
37         return 0;
38 }
39
40 void __kprobes arch_arm_kprobe(struct kprobe *p)
41 {
42         *p->addr = UNIMP_S_INSTRUCTION;
43
44         flush_icache_range((unsigned long)p->addr,
45                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
46 }
47
48 void __kprobes arch_disarm_kprobe(struct kprobe *p)
49 {
50         *p->addr = p->opcode;
51
52         flush_icache_range((unsigned long)p->addr,
53                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
54 }
55
56 void __kprobes arch_remove_kprobe(struct kprobe *p)
57 {
58         arch_disarm_kprobe(p);
59
60         /* Can we remove the kprobe in the middle of kprobe handling? */
61         if (p->ainsn.t1_addr) {
62                 *(p->ainsn.t1_addr) = p->ainsn.t1_opcode;
63
64                 flush_icache_range((unsigned long)p->ainsn.t1_addr,
65                                    (unsigned long)p->ainsn.t1_addr +
66                                    sizeof(kprobe_opcode_t));
67
68                 p->ainsn.t1_addr = NULL;
69         }
70
71         if (p->ainsn.t2_addr) {
72                 *(p->ainsn.t2_addr) = p->ainsn.t2_opcode;
73
74                 flush_icache_range((unsigned long)p->ainsn.t2_addr,
75                                    (unsigned long)p->ainsn.t2_addr +
76                                    sizeof(kprobe_opcode_t));
77
78                 p->ainsn.t2_addr = NULL;
79         }
80 }
81
82 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
83 {
84         kcb->prev_kprobe.kp = kprobe_running();
85         kcb->prev_kprobe.status = kcb->kprobe_status;
86 }
87
88 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
89 {
90         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
91         kcb->kprobe_status = kcb->prev_kprobe.status;
92 }
93
94 static inline void __kprobes set_current_kprobe(struct kprobe *p)
95 {
96         __this_cpu_write(current_kprobe, p);
97 }
98
99 static void __kprobes resume_execution(struct kprobe *p, unsigned long addr,
100                                        struct pt_regs *regs)
101 {
102         /* Remove the trap instructions inserted for single step and
103          * restore the original instructions
104          */
105         if (p->ainsn.t1_addr) {
106                 *(p->ainsn.t1_addr) = p->ainsn.t1_opcode;
107
108                 flush_icache_range((unsigned long)p->ainsn.t1_addr,
109                                    (unsigned long)p->ainsn.t1_addr +
110                                    sizeof(kprobe_opcode_t));
111
112                 p->ainsn.t1_addr = NULL;
113         }
114
115         if (p->ainsn.t2_addr) {
116                 *(p->ainsn.t2_addr) = p->ainsn.t2_opcode;
117
118                 flush_icache_range((unsigned long)p->ainsn.t2_addr,
119                                    (unsigned long)p->ainsn.t2_addr +
120                                    sizeof(kprobe_opcode_t));
121
122                 p->ainsn.t2_addr = NULL;
123         }
124
125         return;
126 }
127
128 static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs)
129 {
130         unsigned long next_pc;
131         unsigned long tgt_if_br = 0;
132         int is_branch;
133         unsigned long bta;
134
135         /* Copy the opcode back to the kprobe location and execute the
136          * instruction. Because of this we will not be able to get into the
137          * same kprobe until this kprobe is done
138          */
139         *(p->addr) = p->opcode;
140
141         flush_icache_range((unsigned long)p->addr,
142                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
143
144         /* Now we insert the trap at the next location after this instruction to
145          * single step. If it is a branch we insert the trap at possible branch
146          * targets
147          */
148
149         bta = regs->bta;
150
151         if (regs->status32 & 0x40) {
152                 /* We are in a delay slot with the branch taken */
153
154                 next_pc = bta & ~0x01;
155
156                 if (!p->ainsn.is_short) {
157                         if (bta & 0x01)
158                                 regs->blink += 2;
159                         else {
160                                 /* Branch not taken */
161                                 next_pc += 2;
162
163                                 /* next pc is taken from bta after executing the
164                                  * delay slot instruction
165                                  */
166                                 regs->bta += 2;
167                         }
168                 }
169
170                 is_branch = 0;
171         } else
172                 is_branch =
173                     disasm_next_pc((unsigned long)p->addr, regs,
174                         (struct callee_regs *) current->thread.callee_reg,
175                         &next_pc, &tgt_if_br);
176
177         p->ainsn.t1_addr = (kprobe_opcode_t *) next_pc;
178         p->ainsn.t1_opcode = *(p->ainsn.t1_addr);
179         *(p->ainsn.t1_addr) = TRAP_S_2_INSTRUCTION;
180
181         flush_icache_range((unsigned long)p->ainsn.t1_addr,
182                            (unsigned long)p->ainsn.t1_addr +
183                            sizeof(kprobe_opcode_t));
184
185         if (is_branch) {
186                 p->ainsn.t2_addr = (kprobe_opcode_t *) tgt_if_br;
187                 p->ainsn.t2_opcode = *(p->ainsn.t2_addr);
188                 *(p->ainsn.t2_addr) = TRAP_S_2_INSTRUCTION;
189
190                 flush_icache_range((unsigned long)p->ainsn.t2_addr,
191                                    (unsigned long)p->ainsn.t2_addr +
192                                    sizeof(kprobe_opcode_t));
193         }
194 }
195
196 int __kprobes arc_kprobe_handler(unsigned long addr, struct pt_regs *regs)
197 {
198         struct kprobe *p;
199         struct kprobe_ctlblk *kcb;
200
201         preempt_disable();
202
203         kcb = get_kprobe_ctlblk();
204         p = get_kprobe((unsigned long *)addr);
205
206         if (p) {
207                 /*
208                  * We have reentered the kprobe_handler, since another kprobe
209                  * was hit while within the handler, we save the original
210                  * kprobes and single step on the instruction of the new probe
211                  * without calling any user handlers to avoid recursive
212                  * kprobes.
213                  */
214                 if (kprobe_running()) {
215                         save_previous_kprobe(kcb);
216                         set_current_kprobe(p);
217                         kprobes_inc_nmissed_count(p);
218                         setup_singlestep(p, regs);
219                         kcb->kprobe_status = KPROBE_REENTER;
220                         return 1;
221                 }
222
223                 set_current_kprobe(p);
224                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
225
226                 /* If we have no pre-handler or it returned 0, we continue with
227                  * normal processing. If we have a pre-handler and it returned
228                  * non-zero - which means user handler setup registers to exit
229                  * to another instruction, we must skip the single stepping.
230                  */
231                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
232                         setup_singlestep(p, regs);
233                         kcb->kprobe_status = KPROBE_HIT_SS;
234                 } else {
235                         reset_current_kprobe();
236                         preempt_enable_no_resched();
237                 }
238
239                 return 1;
240         }
241
242         /* no_kprobe: */
243         preempt_enable_no_resched();
244         return 0;
245 }
246
247 static int __kprobes arc_post_kprobe_handler(unsigned long addr,
248                                          struct pt_regs *regs)
249 {
250         struct kprobe *cur = kprobe_running();
251         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
252
253         if (!cur)
254                 return 0;
255
256         resume_execution(cur, addr, regs);
257
258         /* Rearm the kprobe */
259         arch_arm_kprobe(cur);
260
261         /*
262          * When we return from trap instruction we go to the next instruction
263          * We restored the actual instruction in resume_exectuiont and we to
264          * return to the same address and execute it
265          */
266         regs->ret = addr;
267
268         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
269                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
270                 cur->post_handler(cur, regs, 0);
271         }
272
273         if (kcb->kprobe_status == KPROBE_REENTER) {
274                 restore_previous_kprobe(kcb);
275                 goto out;
276         }
277
278         reset_current_kprobe();
279
280 out:
281         preempt_enable_no_resched();
282         return 1;
283 }
284
285 /*
286  * Fault can be for the instruction being single stepped or for the
287  * pre/post handlers in the module.
288  * This is applicable for applications like user probes, where we have the
289  * probe in user space and the handlers in the kernel
290  */
291
292 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned long trapnr)
293 {
294         struct kprobe *cur = kprobe_running();
295         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
296
297         switch (kcb->kprobe_status) {
298         case KPROBE_HIT_SS:
299         case KPROBE_REENTER:
300                 /*
301                  * We are here because the instruction being single stepped
302                  * caused the fault. We reset the current kprobe and allow the
303                  * exception handler as if it is regular exception. In our
304                  * case it doesn't matter because the system will be halted
305                  */
306                 resume_execution(cur, (unsigned long)cur->addr, regs);
307
308                 if (kcb->kprobe_status == KPROBE_REENTER)
309                         restore_previous_kprobe(kcb);
310                 else
311                         reset_current_kprobe();
312
313                 preempt_enable_no_resched();
314                 break;
315
316         case KPROBE_HIT_ACTIVE:
317         case KPROBE_HIT_SSDONE:
318                 /*
319                  * We are here because the instructions in the pre/post handler
320                  * caused the fault.
321                  */
322
323                 /* We increment the nmissed count for accounting,
324                  * we can also use npre/npostfault count for accounting
325                  * these specific fault cases.
326                  */
327                 kprobes_inc_nmissed_count(cur);
328
329                 /*
330                  * We come here because instructions in the pre/post
331                  * handler caused the page_fault, this could happen
332                  * if handler tries to access user space by
333                  * copy_from_user(), get_user() etc. Let the
334                  * user-specified handler try to fix it first.
335                  */
336                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
337                         return 1;
338
339                 /*
340                  * In case the user-specified fault handler returned zero,
341                  * try to fix up.
342                  */
343                 if (fixup_exception(regs))
344                         return 1;
345
346                 /*
347                  * fixup_exception() could not handle it,
348                  * Let do_page_fault() fix it.
349                  */
350                 break;
351
352         default:
353                 break;
354         }
355         return 0;
356 }
357
358 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
359                                        unsigned long val, void *data)
360 {
361         struct die_args *args = data;
362         unsigned long addr = args->err;
363         int ret = NOTIFY_DONE;
364
365         switch (val) {
366         case DIE_IERR:
367                 if (arc_kprobe_handler(addr, args->regs))
368                         return NOTIFY_STOP;
369                 break;
370
371         case DIE_TRAP:
372                 if (arc_post_kprobe_handler(addr, args->regs))
373                         return NOTIFY_STOP;
374                 break;
375
376         default:
377                 break;
378         }
379
380         return ret;
381 }
382
383 static void __used kretprobe_trampoline_holder(void)
384 {
385         __asm__ __volatile__(".global kretprobe_trampoline\n"
386                              "kretprobe_trampoline:\n" "nop\n");
387 }
388
389 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
390                                       struct pt_regs *regs)
391 {
392
393         ri->ret_addr = (kprobe_opcode_t *) regs->blink;
394
395         /* Replace the return addr with trampoline addr */
396         regs->blink = (unsigned long)&kretprobe_trampoline;
397 }
398
399 static int __kprobes trampoline_probe_handler(struct kprobe *p,
400                                               struct pt_regs *regs)
401 {
402         struct kretprobe_instance *ri = NULL;
403         struct hlist_head *head, empty_rp;
404         struct hlist_node *tmp;
405         unsigned long flags, orig_ret_address = 0;
406         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
407
408         INIT_HLIST_HEAD(&empty_rp);
409         kretprobe_hash_lock(current, &head, &flags);
410
411         /*
412          * It is possible to have multiple instances associated with a given
413          * task either because an multiple functions in the call path
414          * have a return probe installed on them, and/or more than one return
415          * return probe was registered for a target function.
416          *
417          * We can handle this because:
418          *     - instances are always inserted at the head of the list
419          *     - when multiple return probes are registered for the same
420          *       function, the first instance's ret_addr will point to the
421          *       real return address, and all the rest will point to
422          *       kretprobe_trampoline
423          */
424         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
425                 if (ri->task != current)
426                         /* another task is sharing our hash bucket */
427                         continue;
428
429                 if (ri->rp && ri->rp->handler)
430                         ri->rp->handler(ri, regs);
431
432                 orig_ret_address = (unsigned long)ri->ret_addr;
433                 recycle_rp_inst(ri, &empty_rp);
434
435                 if (orig_ret_address != trampoline_address) {
436                         /*
437                          * This is the real return address. Any other
438                          * instances associated with this task are for
439                          * other calls deeper on the call stack
440                          */
441                         break;
442                 }
443         }
444
445         kretprobe_assert(ri, orig_ret_address, trampoline_address);
446         regs->ret = orig_ret_address;
447
448         kretprobe_hash_unlock(current, &flags);
449
450         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
451                 hlist_del(&ri->hlist);
452                 kfree(ri);
453         }
454
455         /* By returning a non zero value, we are telling the kprobe handler
456          * that we don't want the post_handler to run
457          */
458         return 1;
459 }
460
461 static struct kprobe trampoline_p = {
462         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
463         .pre_handler = trampoline_probe_handler
464 };
465
466 int __init arch_init_kprobes(void)
467 {
468         /* Registering the trampoline code for the kret probe */
469         return register_kprobe(&trampoline_p);
470 }
471
472 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
473 {
474         if (p->addr == (kprobe_opcode_t *) &kretprobe_trampoline)
475                 return 1;
476
477         return 0;
478 }
479
480 void trap_is_kprobe(unsigned long address, struct pt_regs *regs)
481 {
482         notify_die(DIE_TRAP, "kprobe_trap", regs, address, 0, SIGTRAP);
483 }