Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-rc-fixes-2.6
[linux-2.6] / arch / sh / kernel / kprobes.c
1 /*
2  * Kernel probes (kprobes) for SuperH
3  *
4  * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
5  * Copyright (C) 2006 Lineo Solutions, Inc.
6  *
7  * This file is subject to the terms and conditions of the GNU General Public
8  * License.  See the file "COPYING" in the main directory of this archive
9  * for more details.
10  */
11 #include <linux/kprobes.h>
12 #include <linux/module.h>
13 #include <linux/ptrace.h>
14 #include <linux/preempt.h>
15 #include <linux/kdebug.h>
16 #include <asm/cacheflush.h>
17 #include <asm/uaccess.h>
18
19 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
20 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
21
22 static struct kprobe saved_current_opcode;
23 static struct kprobe saved_next_opcode;
24 static struct kprobe saved_next_opcode2;
25
26 #define OPCODE_JMP(x)   (((x) & 0xF0FF) == 0x402b)
27 #define OPCODE_JSR(x)   (((x) & 0xF0FF) == 0x400b)
28 #define OPCODE_BRA(x)   (((x) & 0xF000) == 0xa000)
29 #define OPCODE_BRAF(x)  (((x) & 0xF0FF) == 0x0023)
30 #define OPCODE_BSR(x)   (((x) & 0xF000) == 0xb000)
31 #define OPCODE_BSRF(x)  (((x) & 0xF0FF) == 0x0003)
32
33 #define OPCODE_BF_S(x)  (((x) & 0xFF00) == 0x8f00)
34 #define OPCODE_BT_S(x)  (((x) & 0xFF00) == 0x8d00)
35
36 #define OPCODE_BF(x)    (((x) & 0xFF00) == 0x8b00)
37 #define OPCODE_BT(x)    (((x) & 0xFF00) == 0x8900)
38
39 #define OPCODE_RTS(x)   (((x) & 0x000F) == 0x000b)
40 #define OPCODE_RTE(x)   (((x) & 0xFFFF) == 0x002b)
41
42 int __kprobes arch_prepare_kprobe(struct kprobe *p)
43 {
44         kprobe_opcode_t opcode = *(kprobe_opcode_t *) (p->addr);
45
46         if (OPCODE_RTE(opcode))
47                 return -EFAULT; /* Bad breakpoint */
48
49         p->opcode = opcode;
50
51         return 0;
52 }
53
54 void __kprobes arch_copy_kprobe(struct kprobe *p)
55 {
56         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
57         p->opcode = *p->addr;
58 }
59
60 void __kprobes arch_arm_kprobe(struct kprobe *p)
61 {
62         *p->addr = BREAKPOINT_INSTRUCTION;
63         flush_icache_range((unsigned long)p->addr,
64                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
65 }
66
67 void __kprobes arch_disarm_kprobe(struct kprobe *p)
68 {
69         *p->addr = p->opcode;
70         flush_icache_range((unsigned long)p->addr,
71                            (unsigned long)p->addr + sizeof(kprobe_opcode_t));
72 }
73
74 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
75 {
76         if (*p->addr == BREAKPOINT_INSTRUCTION)
77                 return 1;
78
79         return 0;
80 }
81
82 /**
83  * If an illegal slot instruction exception occurs for an address
84  * containing a kprobe, remove the probe.
85  *
86  * Returns 0 if the exception was handled successfully, 1 otherwise.
87  */
88 int __kprobes kprobe_handle_illslot(unsigned long pc)
89 {
90         struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);
91
92         if (p != NULL) {
93                 printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
94                        (unsigned int)pc + 2);
95                 unregister_kprobe(p);
96                 return 0;
97         }
98
99         return 1;
100 }
101
102 void __kprobes arch_remove_kprobe(struct kprobe *p)
103 {
104         if (saved_next_opcode.addr != 0x0) {
105                 arch_disarm_kprobe(p);
106                 arch_disarm_kprobe(&saved_next_opcode);
107                 saved_next_opcode.addr = 0x0;
108                 saved_next_opcode.opcode = 0x0;
109
110                 if (saved_next_opcode2.addr != 0x0) {
111                         arch_disarm_kprobe(&saved_next_opcode2);
112                         saved_next_opcode2.addr = 0x0;
113                         saved_next_opcode2.opcode = 0x0;
114                 }
115         }
116 }
117
118 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
119 {
120         kcb->prev_kprobe.kp = kprobe_running();
121         kcb->prev_kprobe.status = kcb->kprobe_status;
122 }
123
124 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
125 {
126         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
127         kcb->kprobe_status = kcb->prev_kprobe.status;
128 }
129
130 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
131                                          struct kprobe_ctlblk *kcb)
132 {
133         __get_cpu_var(current_kprobe) = p;
134 }
135
136 /*
137  * Singlestep is implemented by disabling the current kprobe and setting one
138  * on the next instruction, following branches. Two probes are set if the
139  * branch is conditional.
140  */
141 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
142 {
143         kprobe_opcode_t *addr = NULL;
144         saved_current_opcode.addr = (kprobe_opcode_t *) (regs->pc);
145         addr = saved_current_opcode.addr;
146
147         if (p != NULL) {
148                 arch_disarm_kprobe(p);
149
150                 if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
151                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
152                         saved_next_opcode.addr =
153                             (kprobe_opcode_t *) regs->regs[reg_nr];
154                 } else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
155                         unsigned long disp = (p->opcode & 0x0FFF);
156                         saved_next_opcode.addr =
157                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
158
159                 } else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
160                         unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
161                         saved_next_opcode.addr =
162                             (kprobe_opcode_t *) (regs->pc + 4 +
163                                                  regs->regs[reg_nr]);
164
165                 } else if (OPCODE_RTS(p->opcode)) {
166                         saved_next_opcode.addr = (kprobe_opcode_t *) regs->pr;
167
168                 } else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
169                         unsigned long disp = (p->opcode & 0x00FF);
170                         /* case 1 */
171                         saved_next_opcode.addr = p->addr + 1;
172                         /* case 2 */
173                         saved_next_opcode2.addr =
174                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
175                         saved_next_opcode2.opcode = *(saved_next_opcode2.addr);
176                         arch_arm_kprobe(&saved_next_opcode2);
177
178                 } else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
179                         unsigned long disp = (p->opcode & 0x00FF);
180                         /* case 1 */
181                         saved_next_opcode.addr = p->addr + 2;
182                         /* case 2 */
183                         saved_next_opcode2.addr =
184                             (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
185                         saved_next_opcode2.opcode = *(saved_next_opcode2.addr);
186                         arch_arm_kprobe(&saved_next_opcode2);
187
188                 } else {
189                         saved_next_opcode.addr = p->addr + 1;
190                 }
191
192                 saved_next_opcode.opcode = *(saved_next_opcode.addr);
193                 arch_arm_kprobe(&saved_next_opcode);
194         }
195 }
196
197 /* Called with kretprobe_lock held */
198 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
199                                       struct pt_regs *regs)
200 {
201         ri->ret_addr = (kprobe_opcode_t *) regs->pr;
202
203         /* Replace the return addr with trampoline addr */
204         regs->pr = (unsigned long)kretprobe_trampoline;
205 }
206
207 static int __kprobes kprobe_handler(struct pt_regs *regs)
208 {
209         struct kprobe *p;
210         int ret = 0;
211         kprobe_opcode_t *addr = NULL;
212         struct kprobe_ctlblk *kcb;
213
214         /*
215          * We don't want to be preempted for the entire
216          * duration of kprobe processing
217          */
218         preempt_disable();
219         kcb = get_kprobe_ctlblk();
220
221         addr = (kprobe_opcode_t *) (regs->pc);
222
223         /* Check we're not actually recursing */
224         if (kprobe_running()) {
225                 p = get_kprobe(addr);
226                 if (p) {
227                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
228                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
229                                 goto no_kprobe;
230                         }
231                         /* We have reentered the kprobe_handler(), since
232                          * another probe was hit while within the handler.
233                          * We here save the original kprobes variables and
234                          * just single step on the instruction of the new probe
235                          * without calling any user handlers.
236                          */
237                         save_previous_kprobe(kcb);
238                         set_current_kprobe(p, regs, kcb);
239                         kprobes_inc_nmissed_count(p);
240                         prepare_singlestep(p, regs);
241                         kcb->kprobe_status = KPROBE_REENTER;
242                         return 1;
243                 } else {
244                         p = __get_cpu_var(current_kprobe);
245                         if (p->break_handler && p->break_handler(p, regs)) {
246                                 goto ss_probe;
247                         }
248                 }
249                 goto no_kprobe;
250         }
251
252         p = get_kprobe(addr);
253         if (!p) {
254                 /* Not one of ours: let kernel handle it */
255                 if (*(kprobe_opcode_t *)addr != BREAKPOINT_INSTRUCTION) {
256                         /*
257                          * The breakpoint instruction was removed right
258                          * after we hit it. Another cpu has removed
259                          * either a probepoint or a debugger breakpoint
260                          * at this address. In either case, no further
261                          * handling of this interrupt is appropriate.
262                          */
263                         ret = 1;
264                 }
265
266                 goto no_kprobe;
267         }
268
269         set_current_kprobe(p, regs, kcb);
270         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
271
272         if (p->pre_handler && p->pre_handler(p, regs))
273                 /* handler has already set things up, so skip ss setup */
274                 return 1;
275
276 ss_probe:
277         prepare_singlestep(p, regs);
278         kcb->kprobe_status = KPROBE_HIT_SS;
279         return 1;
280
281 no_kprobe:
282         preempt_enable_no_resched();
283         return ret;
284 }
285
286 /*
287  * For function-return probes, init_kprobes() establishes a probepoint
288  * here. When a retprobed function returns, this probe is hit and
289  * trampoline_probe_handler() runs, calling the kretprobe's handler.
290  */
291 static void __used kretprobe_trampoline_holder(void)
292 {
293         asm volatile (".globl kretprobe_trampoline\n"
294                       "kretprobe_trampoline:\n\t"
295                       "nop\n");
296 }
297
298 /*
299  * Called when we hit the probe point at kretprobe_trampoline
300  */
301 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
302 {
303         struct kretprobe_instance *ri = NULL;
304         struct hlist_head *head, empty_rp;
305         struct hlist_node *node, *tmp;
306         unsigned long flags, orig_ret_address = 0;
307         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
308
309         INIT_HLIST_HEAD(&empty_rp);
310         kretprobe_hash_lock(current, &head, &flags);
311
312         /*
313          * It is possible to have multiple instances associated with a given
314          * task either because an multiple functions in the call path
315          * have a return probe installed on them, and/or more then one return
316          * return probe was registered for a target function.
317          *
318          * We can handle this because:
319          *     - instances are always inserted at the head of the list
320          *     - when multiple return probes are registered for the same
321          *       function, the first instance's ret_addr will point to the
322          *       real return address, and all the rest will point to
323          *       kretprobe_trampoline
324          */
325         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
326                 if (ri->task != current)
327                         /* another task is sharing our hash bucket */
328                         continue;
329
330                 if (ri->rp && ri->rp->handler) {
331                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
332                         ri->rp->handler(ri, regs);
333                         __get_cpu_var(current_kprobe) = NULL;
334                 }
335
336                 orig_ret_address = (unsigned long)ri->ret_addr;
337                 recycle_rp_inst(ri, &empty_rp);
338
339                 if (orig_ret_address != trampoline_address)
340                         /*
341                          * This is the real return address. Any other
342                          * instances associated with this task are for
343                          * other calls deeper on the call stack
344                          */
345                         break;
346         }
347
348         kretprobe_assert(ri, orig_ret_address, trampoline_address);
349
350         regs->pc = orig_ret_address;
351         kretprobe_hash_unlock(current, &flags);
352
353         preempt_enable_no_resched();
354
355         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
356                 hlist_del(&ri->hlist);
357                 kfree(ri);
358         }
359
360         return orig_ret_address;
361 }
362
363 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
364 {
365         struct kprobe *cur = kprobe_running();
366         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
367         kprobe_opcode_t *addr = NULL;
368         struct kprobe *p = NULL;
369
370         if (!cur)
371                 return 0;
372
373         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
374                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
375                 cur->post_handler(cur, regs, 0);
376         }
377
378         if (saved_next_opcode.addr != 0x0) {
379                 arch_disarm_kprobe(&saved_next_opcode);
380                 saved_next_opcode.addr = 0x0;
381                 saved_next_opcode.opcode = 0x0;
382
383                 addr = saved_current_opcode.addr;
384                 saved_current_opcode.addr = 0x0;
385
386                 p = get_kprobe(addr);
387                 arch_arm_kprobe(p);
388
389                 if (saved_next_opcode2.addr != 0x0) {
390                         arch_disarm_kprobe(&saved_next_opcode2);
391                         saved_next_opcode2.addr = 0x0;
392                         saved_next_opcode2.opcode = 0x0;
393                 }
394         }
395
396         /* Restore back the original saved kprobes variables and continue. */
397         if (kcb->kprobe_status == KPROBE_REENTER) {
398                 restore_previous_kprobe(kcb);
399                 goto out;
400         }
401
402         reset_current_kprobe();
403
404 out:
405         preempt_enable_no_resched();
406
407         return 1;
408 }
409
410 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
411 {
412         struct kprobe *cur = kprobe_running();
413         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
414         const struct exception_table_entry *entry;
415
416         switch (kcb->kprobe_status) {
417         case KPROBE_HIT_SS:
418         case KPROBE_REENTER:
419                 /*
420                  * We are here because the instruction being single
421                  * stepped caused a page fault. We reset the current
422                  * kprobe, point the pc back to the probe address
423                  * and allow the page fault handler to continue as a
424                  * normal page fault.
425                  */
426                 regs->pc = (unsigned long)cur->addr;
427                 if (kcb->kprobe_status == KPROBE_REENTER)
428                         restore_previous_kprobe(kcb);
429                 else
430                         reset_current_kprobe();
431                 preempt_enable_no_resched();
432                 break;
433         case KPROBE_HIT_ACTIVE:
434         case KPROBE_HIT_SSDONE:
435                 /*
436                  * We increment the nmissed count for accounting,
437                  * we can also use npre/npostfault count for accounting
438                  * these specific fault cases.
439                  */
440                 kprobes_inc_nmissed_count(cur);
441
442                 /*
443                  * We come here because instructions in the pre/post
444                  * handler caused the page_fault, this could happen
445                  * if handler tries to access user space by
446                  * copy_from_user(), get_user() etc. Let the
447                  * user-specified handler try to fix it first.
448                  */
449                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
450                         return 1;
451
452                 /*
453                  * In case the user-specified fault handler returned
454                  * zero, try to fix up.
455                  */
456                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
457                         regs->pc = entry->fixup;
458                         return 1;
459                 }
460
461                 /*
462                  * fixup_exception() could not handle it,
463                  * Let do_page_fault() fix it.
464                  */
465                 break;
466         default:
467                 break;
468         }
469
470         return 0;
471 }
472
473 /*
474  * Wrapper routine to for handling exceptions.
475  */
476 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
477                                        unsigned long val, void *data)
478 {
479         struct kprobe *p = NULL;
480         struct die_args *args = (struct die_args *)data;
481         int ret = NOTIFY_DONE;
482         kprobe_opcode_t *addr = NULL;
483         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
484
485         addr = (kprobe_opcode_t *) (args->regs->pc);
486         if (val == DIE_TRAP) {
487                 if (!kprobe_running()) {
488                         if (kprobe_handler(args->regs)) {
489                                 ret = NOTIFY_STOP;
490                         } else {
491                                 /* Not a kprobe trap */
492                                 ret = NOTIFY_DONE;
493                         }
494                 } else {
495                         p = get_kprobe(addr);
496                         if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
497                             (kcb->kprobe_status == KPROBE_REENTER)) {
498                                 if (post_kprobe_handler(args->regs))
499                                         ret = NOTIFY_STOP;
500                         } else {
501                                 if (kprobe_handler(args->regs)) {
502                                         ret = NOTIFY_STOP;
503                                 } else {
504                                         p = __get_cpu_var(current_kprobe);
505                                         if (p->break_handler &&
506                                             p->break_handler(p, args->regs))
507                                                 ret = NOTIFY_STOP;
508                                 }
509                         }
510                 }
511         }
512
513         return ret;
514 }
515
516 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
517 {
518         struct jprobe *jp = container_of(p, struct jprobe, kp);
519         unsigned long addr;
520         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
521
522         kcb->jprobe_saved_regs = *regs;
523         kcb->jprobe_saved_r15 = regs->regs[15];
524         addr = kcb->jprobe_saved_r15;
525
526         /*
527          * TBD: As Linus pointed out, gcc assumes that the callee
528          * owns the argument space and could overwrite it, e.g.
529          * tailcall optimization. So, to be absolutely safe
530          * we also save and restore enough stack bytes to cover
531          * the argument area.
532          */
533         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
534                MIN_STACK_SIZE(addr));
535
536         regs->pc = (unsigned long)(jp->entry);
537
538         return 1;
539 }
540
541 void __kprobes jprobe_return(void)
542 {
543         asm volatile ("trapa #0x3a\n\t" "jprobe_return_end:\n\t" "nop\n\t");
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         unsigned long stack_addr = kcb->jprobe_saved_r15;
550         u8 *addr = (u8 *)regs->pc;
551
552         if ((addr >= (u8 *)jprobe_return) &&
553             (addr <= (u8 *)jprobe_return_end)) {
554                 *regs = kcb->jprobe_saved_regs;
555
556                 memcpy((kprobe_opcode_t *)stack_addr, kcb->jprobes_stack,
557                        MIN_STACK_SIZE(stack_addr));
558
559                 kcb->kprobe_status = KPROBE_HIT_SS;
560                 preempt_enable_no_resched();
561                 return 1;
562         }
563
564         return 0;
565 }
566
567 static struct kprobe trampoline_p = {
568         .addr = (kprobe_opcode_t *)&kretprobe_trampoline,
569         .pre_handler = trampoline_probe_handler
570 };
571
572 int __init arch_init_kprobes(void)
573 {
574         saved_next_opcode.addr = 0x0;
575         saved_next_opcode.opcode = 0x0;
576
577         saved_current_opcode.addr = 0x0;
578         saved_current_opcode.opcode = 0x0;
579
580         saved_next_opcode2.addr = 0x0;
581         saved_next_opcode2.opcode = 0x0;
582
583         return register_kprobe(&trampoline_p);
584 }