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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright (C) IBM Corporation, 2002, 2004
6 *
7 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
8 * Probes initial implementation ( includes contributions from
9 * Rusty Russell).
10 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
11 * interface to access function arguments.
12 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
13 * for PPC64
14 */
15
16#include <linux/kprobes.h>
17#include <linux/ptrace.h>
18#include <linux/preempt.h>
19#include <linux/extable.h>
20#include <linux/kdebug.h>
21#include <linux/slab.h>
22#include <asm/code-patching.h>
23#include <asm/cacheflush.h>
24#include <asm/sstep.h>
25#include <asm/sections.h>
26#include <asm/inst.h>
27#include <linux/uaccess.h>
28
29DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
30DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
31
32struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
33
34bool arch_within_kprobe_blacklist(unsigned long addr)
35{
36 return (addr >= (unsigned long)__kprobes_text_start &&
37 addr < (unsigned long)__kprobes_text_end) ||
38 (addr >= (unsigned long)_stext &&
39 addr < (unsigned long)__head_end);
40}
41
42kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
43{
44 kprobe_opcode_t *addr = NULL;
45
46#ifdef PPC64_ELF_ABI_v2
47 /* PPC64 ABIv2 needs local entry point */
48 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
49 if (addr && !offset) {
50#ifdef CONFIG_KPROBES_ON_FTRACE
51 unsigned long faddr;
52 /*
53 * Per livepatch.h, ftrace location is always within the first
54 * 16 bytes of a function on powerpc with -mprofile-kernel.
55 */
56 faddr = ftrace_location_range((unsigned long)addr,
57 (unsigned long)addr + 16);
58 if (faddr)
59 addr = (kprobe_opcode_t *)faddr;
60 else
61#endif
62 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
63 }
64#elif defined(PPC64_ELF_ABI_v1)
65 /*
66 * 64bit powerpc ABIv1 uses function descriptors:
67 * - Check for the dot variant of the symbol first.
68 * - If that fails, try looking up the symbol provided.
69 *
70 * This ensures we always get to the actual symbol and not
71 * the descriptor.
72 *
73 * Also handle <module:symbol> format.
74 */
75 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
76 bool dot_appended = false;
77 const char *c;
78 ssize_t ret = 0;
79 int len = 0;
80
81 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
82 c++;
83 len = c - name;
84 memcpy(dot_name, name, len);
85 } else
86 c = name;
87
88 if (*c != '\0' && *c != '.') {
89 dot_name[len++] = '.';
90 dot_appended = true;
91 }
92 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
93 if (ret > 0)
94 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
95
96 /* Fallback to the original non-dot symbol lookup */
97 if (!addr && dot_appended)
98 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
99#else
100 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
101#endif
102
103 return addr;
104}
105
106int arch_prepare_kprobe(struct kprobe *p)
107{
108 int ret = 0;
109 struct kprobe *prev;
110 struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr);
111 struct ppc_inst prefix = ppc_inst_read((struct ppc_inst *)(p->addr - 1));
112
113 if ((unsigned long)p->addr & 0x03) {
114 printk("Attempt to register kprobe at an unaligned address\n");
115 ret = -EINVAL;
116 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
117 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
118 ret = -EINVAL;
119 } else if (ppc_inst_prefixed(prefix)) {
120 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
121 ret = -EINVAL;
122 }
123 preempt_disable();
124 prev = get_kprobe(p->addr - 1);
125 preempt_enable_no_resched();
126 if (prev &&
127 ppc_inst_prefixed(ppc_inst_read((struct ppc_inst *)prev->ainsn.insn))) {
128 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
129 ret = -EINVAL;
130 }
131
132 /* insn must be on a special executable page on ppc64. This is
133 * not explicitly required on ppc32 (right now), but it doesn't hurt */
134 if (!ret) {
135 p->ainsn.insn = get_insn_slot();
136 if (!p->ainsn.insn)
137 ret = -ENOMEM;
138 }
139
140 if (!ret) {
141 patch_instruction((struct ppc_inst *)p->ainsn.insn, insn);
142 p->opcode = ppc_inst_val(insn);
143 }
144
145 p->ainsn.boostable = 0;
146 return ret;
147}
148NOKPROBE_SYMBOL(arch_prepare_kprobe);
149
150void arch_arm_kprobe(struct kprobe *p)
151{
152 patch_instruction((struct ppc_inst *)p->addr, ppc_inst(BREAKPOINT_INSTRUCTION));
153}
154NOKPROBE_SYMBOL(arch_arm_kprobe);
155
156void arch_disarm_kprobe(struct kprobe *p)
157{
158 patch_instruction((struct ppc_inst *)p->addr, ppc_inst(p->opcode));
159}
160NOKPROBE_SYMBOL(arch_disarm_kprobe);
161
162void arch_remove_kprobe(struct kprobe *p)
163{
164 if (p->ainsn.insn) {
165 free_insn_slot(p->ainsn.insn, 0);
166 p->ainsn.insn = NULL;
167 }
168}
169NOKPROBE_SYMBOL(arch_remove_kprobe);
170
171static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
172{
173 enable_single_step(regs);
174
175 /*
176 * On powerpc we should single step on the original
177 * instruction even if the probed insn is a trap
178 * variant as values in regs could play a part in
179 * if the trap is taken or not
180 */
181 regs->nip = (unsigned long)p->ainsn.insn;
182}
183
184static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
185{
186 kcb->prev_kprobe.kp = kprobe_running();
187 kcb->prev_kprobe.status = kcb->kprobe_status;
188 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
189}
190
191static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
192{
193 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
194 kcb->kprobe_status = kcb->prev_kprobe.status;
195 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
196}
197
198static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
199 struct kprobe_ctlblk *kcb)
200{
201 __this_cpu_write(current_kprobe, p);
202 kcb->kprobe_saved_msr = regs->msr;
203}
204
205bool arch_kprobe_on_func_entry(unsigned long offset)
206{
207#ifdef PPC64_ELF_ABI_v2
208#ifdef CONFIG_KPROBES_ON_FTRACE
209 return offset <= 16;
210#else
211 return offset <= 8;
212#endif
213#else
214 return !offset;
215#endif
216}
217
218void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
219{
220 ri->ret_addr = (kprobe_opcode_t *)regs->link;
221
222 /* Replace the return addr with trampoline addr */
223 regs->link = (unsigned long)kretprobe_trampoline;
224}
225NOKPROBE_SYMBOL(arch_prepare_kretprobe);
226
227static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
228{
229 int ret;
230 struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
231
232 /* regs->nip is also adjusted if emulate_step returns 1 */
233 ret = emulate_step(regs, insn);
234 if (ret > 0) {
235 /*
236 * Once this instruction has been boosted
237 * successfully, set the boostable flag
238 */
239 if (unlikely(p->ainsn.boostable == 0))
240 p->ainsn.boostable = 1;
241 } else if (ret < 0) {
242 /*
243 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
244 * So, we should never get here... but, its still
245 * good to catch them, just in case...
246 */
247 printk("Can't step on instruction %s\n", ppc_inst_as_str(insn));
248 BUG();
249 } else {
250 /*
251 * If we haven't previously emulated this instruction, then it
252 * can't be boosted. Note it down so we don't try to do so again.
253 *
254 * If, however, we had emulated this instruction in the past,
255 * then this is just an error with the current run (for
256 * instance, exceptions due to a load/store). We return 0 so
257 * that this is now single-stepped, but continue to try
258 * emulating it in subsequent probe hits.
259 */
260 if (unlikely(p->ainsn.boostable != 1))
261 p->ainsn.boostable = -1;
262 }
263
264 return ret;
265}
266NOKPROBE_SYMBOL(try_to_emulate);
267
268int kprobe_handler(struct pt_regs *regs)
269{
270 struct kprobe *p;
271 int ret = 0;
272 unsigned int *addr = (unsigned int *)regs->nip;
273 struct kprobe_ctlblk *kcb;
274
275 if (user_mode(regs))
276 return 0;
277
278 if (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR))
279 return 0;
280
281 /*
282 * We don't want to be preempted for the entire
283 * duration of kprobe processing
284 */
285 preempt_disable();
286 kcb = get_kprobe_ctlblk();
287
288 p = get_kprobe(addr);
289 if (!p) {
290 unsigned int instr;
291
292 if (get_kernel_nofault(instr, addr))
293 goto no_kprobe;
294
295 if (instr != BREAKPOINT_INSTRUCTION) {
296 /*
297 * PowerPC has multiple variants of the "trap"
298 * instruction. If the current instruction is a
299 * trap variant, it could belong to someone else
300 */
301 if (is_trap(instr))
302 goto no_kprobe;
303 /*
304 * The breakpoint instruction was removed right
305 * after we hit it. Another cpu has removed
306 * either a probepoint or a debugger breakpoint
307 * at this address. In either case, no further
308 * handling of this interrupt is appropriate.
309 */
310 ret = 1;
311 }
312 /* Not one of ours: let kernel handle it */
313 goto no_kprobe;
314 }
315
316 /* Check we're not actually recursing */
317 if (kprobe_running()) {
318 kprobe_opcode_t insn = *p->ainsn.insn;
319 if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
320 /* Turn off 'trace' bits */
321 regs->msr &= ~MSR_SINGLESTEP;
322 regs->msr |= kcb->kprobe_saved_msr;
323 goto no_kprobe;
324 }
325
326 /*
327 * We have reentered the kprobe_handler(), since another probe
328 * was hit while within the handler. We here save the original
329 * kprobes variables and just single step on the instruction of
330 * the new probe without calling any user handlers.
331 */
332 save_previous_kprobe(kcb);
333 set_current_kprobe(p, regs, kcb);
334 kprobes_inc_nmissed_count(p);
335 kcb->kprobe_status = KPROBE_REENTER;
336 if (p->ainsn.boostable >= 0) {
337 ret = try_to_emulate(p, regs);
338
339 if (ret > 0) {
340 restore_previous_kprobe(kcb);
341 preempt_enable_no_resched();
342 return 1;
343 }
344 }
345 prepare_singlestep(p, regs);
346 return 1;
347 }
348
349 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
350 set_current_kprobe(p, regs, kcb);
351 if (p->pre_handler && p->pre_handler(p, regs)) {
352 /* handler changed execution path, so skip ss setup */
353 reset_current_kprobe();
354 preempt_enable_no_resched();
355 return 1;
356 }
357
358 if (p->ainsn.boostable >= 0) {
359 ret = try_to_emulate(p, regs);
360
361 if (ret > 0) {
362 if (p->post_handler)
363 p->post_handler(p, regs, 0);
364
365 kcb->kprobe_status = KPROBE_HIT_SSDONE;
366 reset_current_kprobe();
367 preempt_enable_no_resched();
368 return 1;
369 }
370 }
371 prepare_singlestep(p, regs);
372 kcb->kprobe_status = KPROBE_HIT_SS;
373 return 1;
374
375no_kprobe:
376 preempt_enable_no_resched();
377 return ret;
378}
379NOKPROBE_SYMBOL(kprobe_handler);
380
381/*
382 * Function return probe trampoline:
383 * - init_kprobes() establishes a probepoint here
384 * - When the probed function returns, this probe
385 * causes the handlers to fire
386 */
387asm(".global kretprobe_trampoline\n"
388 ".type kretprobe_trampoline, @function\n"
389 "kretprobe_trampoline:\n"
390 "nop\n"
391 "blr\n"
392 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
393
394/*
395 * Called when the probe at kretprobe trampoline is hit
396 */
397static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
398{
399 struct kretprobe_instance *ri = NULL;
400 struct hlist_head *head, empty_rp;
401 struct hlist_node *tmp;
402 unsigned long flags, orig_ret_address = 0;
403 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
404
405 INIT_HLIST_HEAD(&empty_rp);
406 kretprobe_hash_lock(current, &head, &flags);
407
408 /*
409 * It is possible to have multiple instances associated with a given
410 * task either because an multiple functions in the call path
411 * have a return probe installed on them, and/or more than one return
412 * return probe was registered for a target function.
413 *
414 * We can handle this because:
415 * - instances are always inserted at the head of the list
416 * - when multiple return probes are registered for the same
417 * function, the first instance's ret_addr will point to the
418 * real return address, and all the rest will point to
419 * kretprobe_trampoline
420 */
421 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
422 if (ri->task != current)
423 /* another task is sharing our hash bucket */
424 continue;
425
426 if (ri->rp && ri->rp->handler)
427 ri->rp->handler(ri, regs);
428
429 orig_ret_address = (unsigned long)ri->ret_addr;
430 recycle_rp_inst(ri, &empty_rp);
431
432 if (orig_ret_address != trampoline_address)
433 /*
434 * This is the real return address. Any other
435 * instances associated with this task are for
436 * other calls deeper on the call stack
437 */
438 break;
439 }
440
441 kretprobe_assert(ri, orig_ret_address, trampoline_address);
442
443 /*
444 * We get here through one of two paths:
445 * 1. by taking a trap -> kprobe_handler() -> here
446 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
447 *
448 * When going back through (1), we need regs->nip to be setup properly
449 * as it is used to determine the return address from the trap.
450 * For (2), since nip is not honoured with optprobes, we instead setup
451 * the link register properly so that the subsequent 'blr' in
452 * kretprobe_trampoline jumps back to the right instruction.
453 *
454 * For nip, we should set the address to the previous instruction since
455 * we end up emulating it in kprobe_handler(), which increments the nip
456 * again.
457 */
458 regs->nip = orig_ret_address - 4;
459 regs->link = orig_ret_address;
460
461 kretprobe_hash_unlock(current, &flags);
462
463 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
464 hlist_del(&ri->hlist);
465 kfree(ri);
466 }
467
468 return 0;
469}
470NOKPROBE_SYMBOL(trampoline_probe_handler);
471
472/*
473 * Called after single-stepping. p->addr is the address of the
474 * instruction whose first byte has been replaced by the "breakpoint"
475 * instruction. To avoid the SMP problems that can occur when we
476 * temporarily put back the original opcode to single-step, we
477 * single-stepped a copy of the instruction. The address of this
478 * copy is p->ainsn.insn.
479 */
480int kprobe_post_handler(struct pt_regs *regs)
481{
482 int len;
483 struct kprobe *cur = kprobe_running();
484 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
485
486 if (!cur || user_mode(regs))
487 return 0;
488
489 len = ppc_inst_len(ppc_inst_read((struct ppc_inst *)cur->ainsn.insn));
490 /* make sure we got here for instruction we have a kprobe on */
491 if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
492 return 0;
493
494 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
495 kcb->kprobe_status = KPROBE_HIT_SSDONE;
496 cur->post_handler(cur, regs, 0);
497 }
498
499 /* Adjust nip to after the single-stepped instruction */
500 regs->nip = (unsigned long)cur->addr + len;
501 regs->msr |= kcb->kprobe_saved_msr;
502
503 /*Restore back the original saved kprobes variables and continue. */
504 if (kcb->kprobe_status == KPROBE_REENTER) {
505 restore_previous_kprobe(kcb);
506 goto out;
507 }
508 reset_current_kprobe();
509out:
510 preempt_enable_no_resched();
511
512 /*
513 * if somebody else is singlestepping across a probe point, msr
514 * will have DE/SE set, in which case, continue the remaining processing
515 * of do_debug, as if this is not a probe hit.
516 */
517 if (regs->msr & MSR_SINGLESTEP)
518 return 0;
519
520 return 1;
521}
522NOKPROBE_SYMBOL(kprobe_post_handler);
523
524int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
525{
526 struct kprobe *cur = kprobe_running();
527 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
528 const struct exception_table_entry *entry;
529
530 switch(kcb->kprobe_status) {
531 case KPROBE_HIT_SS:
532 case KPROBE_REENTER:
533 /*
534 * We are here because the instruction being single
535 * stepped caused a page fault. We reset the current
536 * kprobe and the nip points back to the probe address
537 * and allow the page fault handler to continue as a
538 * normal page fault.
539 */
540 regs->nip = (unsigned long)cur->addr;
541 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
542 regs->msr |= kcb->kprobe_saved_msr;
543 if (kcb->kprobe_status == KPROBE_REENTER)
544 restore_previous_kprobe(kcb);
545 else
546 reset_current_kprobe();
547 preempt_enable_no_resched();
548 break;
549 case KPROBE_HIT_ACTIVE:
550 case KPROBE_HIT_SSDONE:
551 /*
552 * We increment the nmissed count for accounting,
553 * we can also use npre/npostfault count for accounting
554 * these specific fault cases.
555 */
556 kprobes_inc_nmissed_count(cur);
557
558 /*
559 * We come here because instructions in the pre/post
560 * handler caused the page_fault, this could happen
561 * if handler tries to access user space by
562 * copy_from_user(), get_user() etc. Let the
563 * user-specified handler try to fix it first.
564 */
565 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
566 return 1;
567
568 /*
569 * In case the user-specified fault handler returned
570 * zero, try to fix up.
571 */
572 if ((entry = search_exception_tables(regs->nip)) != NULL) {
573 regs->nip = extable_fixup(entry);
574 return 1;
575 }
576
577 /*
578 * fixup_exception() could not handle it,
579 * Let do_page_fault() fix it.
580 */
581 break;
582 default:
583 break;
584 }
585 return 0;
586}
587NOKPROBE_SYMBOL(kprobe_fault_handler);
588
589unsigned long arch_deref_entry_point(void *entry)
590{
591#ifdef PPC64_ELF_ABI_v1
592 if (!kernel_text_address((unsigned long)entry))
593 return ppc_global_function_entry(entry);
594 else
595#endif
596 return (unsigned long)entry;
597}
598NOKPROBE_SYMBOL(arch_deref_entry_point);
599
600static struct kprobe trampoline_p = {
601 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
602 .pre_handler = trampoline_probe_handler
603};
604
605int __init arch_init_kprobes(void)
606{
607 return register_kprobe(&trampoline_p);
608}
609
610int arch_trampoline_kprobe(struct kprobe *p)
611{
612 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
613 return 1;
614
615 return 0;
616}
617NOKPROBE_SYMBOL(arch_trampoline_kprobe);
1/*
2 * Kernel Probes (KProbes)
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 as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2002, 2004
19 *
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
22 * Rusty Russell).
23 * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
24 * interface to access function arguments.
25 * 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
26 * for PPC64
27 */
28
29#include <linux/kprobes.h>
30#include <linux/ptrace.h>
31#include <linux/preempt.h>
32#include <linux/module.h>
33#include <linux/kdebug.h>
34#include <linux/slab.h>
35#include <asm/cacheflush.h>
36#include <asm/sstep.h>
37#include <asm/uaccess.h>
38
39#ifdef CONFIG_PPC_ADV_DEBUG_REGS
40#define MSR_SINGLESTEP (MSR_DE)
41#else
42#define MSR_SINGLESTEP (MSR_SE)
43#endif
44
45DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
46DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
47
48struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
49
50int __kprobes arch_prepare_kprobe(struct kprobe *p)
51{
52 int ret = 0;
53 kprobe_opcode_t insn = *p->addr;
54
55 if ((unsigned long)p->addr & 0x03) {
56 printk("Attempt to register kprobe at an unaligned address\n");
57 ret = -EINVAL;
58 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
59 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
60 ret = -EINVAL;
61 }
62
63 /* insn must be on a special executable page on ppc64. This is
64 * not explicitly required on ppc32 (right now), but it doesn't hurt */
65 if (!ret) {
66 p->ainsn.insn = get_insn_slot();
67 if (!p->ainsn.insn)
68 ret = -ENOMEM;
69 }
70
71 if (!ret) {
72 memcpy(p->ainsn.insn, p->addr,
73 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
74 p->opcode = *p->addr;
75 flush_icache_range((unsigned long)p->ainsn.insn,
76 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
77 }
78
79 p->ainsn.boostable = 0;
80 return ret;
81}
82
83void __kprobes arch_arm_kprobe(struct kprobe *p)
84{
85 *p->addr = BREAKPOINT_INSTRUCTION;
86 flush_icache_range((unsigned long) p->addr,
87 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
88}
89
90void __kprobes arch_disarm_kprobe(struct kprobe *p)
91{
92 *p->addr = p->opcode;
93 flush_icache_range((unsigned long) p->addr,
94 (unsigned long) p->addr + sizeof(kprobe_opcode_t));
95}
96
97void __kprobes arch_remove_kprobe(struct kprobe *p)
98{
99 if (p->ainsn.insn) {
100 free_insn_slot(p->ainsn.insn, 0);
101 p->ainsn.insn = NULL;
102 }
103}
104
105static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
106{
107 /* We turn off async exceptions to ensure that the single step will
108 * be for the instruction we have the kprobe on, if we dont its
109 * possible we'd get the single step reported for an exception handler
110 * like Decrementer or External Interrupt */
111 regs->msr &= ~MSR_EE;
112 regs->msr |= MSR_SINGLESTEP;
113#ifdef CONFIG_PPC_ADV_DEBUG_REGS
114 regs->msr &= ~MSR_CE;
115 mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
116#ifdef CONFIG_PPC_47x
117 isync();
118#endif
119#endif
120
121 /*
122 * On powerpc we should single step on the original
123 * instruction even if the probed insn is a trap
124 * variant as values in regs could play a part in
125 * if the trap is taken or not
126 */
127 regs->nip = (unsigned long)p->ainsn.insn;
128}
129
130static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
131{
132 kcb->prev_kprobe.kp = kprobe_running();
133 kcb->prev_kprobe.status = kcb->kprobe_status;
134 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
135}
136
137static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
138{
139 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
140 kcb->kprobe_status = kcb->prev_kprobe.status;
141 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
142}
143
144static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
145 struct kprobe_ctlblk *kcb)
146{
147 __get_cpu_var(current_kprobe) = p;
148 kcb->kprobe_saved_msr = regs->msr;
149}
150
151void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
152 struct pt_regs *regs)
153{
154 ri->ret_addr = (kprobe_opcode_t *)regs->link;
155
156 /* Replace the return addr with trampoline addr */
157 regs->link = (unsigned long)kretprobe_trampoline;
158}
159
160static int __kprobes kprobe_handler(struct pt_regs *regs)
161{
162 struct kprobe *p;
163 int ret = 0;
164 unsigned int *addr = (unsigned int *)regs->nip;
165 struct kprobe_ctlblk *kcb;
166
167 /*
168 * We don't want to be preempted for the entire
169 * duration of kprobe processing
170 */
171 preempt_disable();
172 kcb = get_kprobe_ctlblk();
173
174 /* Check we're not actually recursing */
175 if (kprobe_running()) {
176 p = get_kprobe(addr);
177 if (p) {
178 kprobe_opcode_t insn = *p->ainsn.insn;
179 if (kcb->kprobe_status == KPROBE_HIT_SS &&
180 is_trap(insn)) {
181 /* Turn off 'trace' bits */
182 regs->msr &= ~MSR_SINGLESTEP;
183 regs->msr |= kcb->kprobe_saved_msr;
184 goto no_kprobe;
185 }
186 /* We have reentered the kprobe_handler(), since
187 * another probe was hit while within the handler.
188 * We here save the original kprobes variables and
189 * just single step on the instruction of the new probe
190 * without calling any user handlers.
191 */
192 save_previous_kprobe(kcb);
193 set_current_kprobe(p, regs, kcb);
194 kcb->kprobe_saved_msr = regs->msr;
195 kprobes_inc_nmissed_count(p);
196 prepare_singlestep(p, regs);
197 kcb->kprobe_status = KPROBE_REENTER;
198 return 1;
199 } else {
200 if (*addr != BREAKPOINT_INSTRUCTION) {
201 /* If trap variant, then it belongs not to us */
202 kprobe_opcode_t cur_insn = *addr;
203 if (is_trap(cur_insn))
204 goto no_kprobe;
205 /* The breakpoint instruction was removed by
206 * another cpu right after we hit, no further
207 * handling of this interrupt is appropriate
208 */
209 ret = 1;
210 goto no_kprobe;
211 }
212 p = __get_cpu_var(current_kprobe);
213 if (p->break_handler && p->break_handler(p, regs)) {
214 goto ss_probe;
215 }
216 }
217 goto no_kprobe;
218 }
219
220 p = get_kprobe(addr);
221 if (!p) {
222 if (*addr != BREAKPOINT_INSTRUCTION) {
223 /*
224 * PowerPC has multiple variants of the "trap"
225 * instruction. If the current instruction is a
226 * trap variant, it could belong to someone else
227 */
228 kprobe_opcode_t cur_insn = *addr;
229 if (is_trap(cur_insn))
230 goto no_kprobe;
231 /*
232 * The breakpoint instruction was removed right
233 * after we hit it. Another cpu has removed
234 * either a probepoint or a debugger breakpoint
235 * at this address. In either case, no further
236 * handling of this interrupt is appropriate.
237 */
238 ret = 1;
239 }
240 /* Not one of ours: let kernel handle it */
241 goto no_kprobe;
242 }
243
244 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
245 set_current_kprobe(p, regs, kcb);
246 if (p->pre_handler && p->pre_handler(p, regs))
247 /* handler has already set things up, so skip ss setup */
248 return 1;
249
250ss_probe:
251 if (p->ainsn.boostable >= 0) {
252 unsigned int insn = *p->ainsn.insn;
253
254 /* regs->nip is also adjusted if emulate_step returns 1 */
255 ret = emulate_step(regs, insn);
256 if (ret > 0) {
257 /*
258 * Once this instruction has been boosted
259 * successfully, set the boostable flag
260 */
261 if (unlikely(p->ainsn.boostable == 0))
262 p->ainsn.boostable = 1;
263
264 if (p->post_handler)
265 p->post_handler(p, regs, 0);
266
267 kcb->kprobe_status = KPROBE_HIT_SSDONE;
268 reset_current_kprobe();
269 preempt_enable_no_resched();
270 return 1;
271 } else if (ret < 0) {
272 /*
273 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
274 * So, we should never get here... but, its still
275 * good to catch them, just in case...
276 */
277 printk("Can't step on instruction %x\n", insn);
278 BUG();
279 } else if (ret == 0)
280 /* This instruction can't be boosted */
281 p->ainsn.boostable = -1;
282 }
283 prepare_singlestep(p, regs);
284 kcb->kprobe_status = KPROBE_HIT_SS;
285 return 1;
286
287no_kprobe:
288 preempt_enable_no_resched();
289 return ret;
290}
291
292/*
293 * Function return probe trampoline:
294 * - init_kprobes() establishes a probepoint here
295 * - When the probed function returns, this probe
296 * causes the handlers to fire
297 */
298static void __used kretprobe_trampoline_holder(void)
299{
300 asm volatile(".global kretprobe_trampoline\n"
301 "kretprobe_trampoline:\n"
302 "nop\n");
303}
304
305/*
306 * Called when the probe at kretprobe trampoline is hit
307 */
308static int __kprobes trampoline_probe_handler(struct kprobe *p,
309 struct pt_regs *regs)
310{
311 struct kretprobe_instance *ri = NULL;
312 struct hlist_head *head, empty_rp;
313 struct hlist_node *node, *tmp;
314 unsigned long flags, orig_ret_address = 0;
315 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
316
317 INIT_HLIST_HEAD(&empty_rp);
318 kretprobe_hash_lock(current, &head, &flags);
319
320 /*
321 * It is possible to have multiple instances associated with a given
322 * task either because an multiple functions in the call path
323 * have a return probe installed on them, and/or more than one return
324 * return probe was registered for a target function.
325 *
326 * We can handle this because:
327 * - instances are always inserted at the head of the list
328 * - when multiple return probes are registered for the same
329 * function, the first instance's ret_addr will point to the
330 * real return address, and all the rest will point to
331 * kretprobe_trampoline
332 */
333 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
334 if (ri->task != current)
335 /* another task is sharing our hash bucket */
336 continue;
337
338 if (ri->rp && ri->rp->handler)
339 ri->rp->handler(ri, regs);
340
341 orig_ret_address = (unsigned long)ri->ret_addr;
342 recycle_rp_inst(ri, &empty_rp);
343
344 if (orig_ret_address != trampoline_address)
345 /*
346 * This is the real return address. Any other
347 * instances associated with this task are for
348 * other calls deeper on the call stack
349 */
350 break;
351 }
352
353 kretprobe_assert(ri, orig_ret_address, trampoline_address);
354 regs->nip = orig_ret_address;
355
356 reset_current_kprobe();
357 kretprobe_hash_unlock(current, &flags);
358 preempt_enable_no_resched();
359
360 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
361 hlist_del(&ri->hlist);
362 kfree(ri);
363 }
364 /*
365 * By returning a non-zero value, we are telling
366 * kprobe_handler() that we don't want the post_handler
367 * to run (and have re-enabled preemption)
368 */
369 return 1;
370}
371
372/*
373 * Called after single-stepping. p->addr is the address of the
374 * instruction whose first byte has been replaced by the "breakpoint"
375 * instruction. To avoid the SMP problems that can occur when we
376 * temporarily put back the original opcode to single-step, we
377 * single-stepped a copy of the instruction. The address of this
378 * copy is p->ainsn.insn.
379 */
380static int __kprobes post_kprobe_handler(struct pt_regs *regs)
381{
382 struct kprobe *cur = kprobe_running();
383 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
384
385 if (!cur)
386 return 0;
387
388 /* make sure we got here for instruction we have a kprobe on */
389 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
390 return 0;
391
392 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
393 kcb->kprobe_status = KPROBE_HIT_SSDONE;
394 cur->post_handler(cur, regs, 0);
395 }
396
397 /* Adjust nip to after the single-stepped instruction */
398 regs->nip = (unsigned long)cur->addr + 4;
399 regs->msr |= kcb->kprobe_saved_msr;
400
401 /*Restore back the original saved kprobes variables and continue. */
402 if (kcb->kprobe_status == KPROBE_REENTER) {
403 restore_previous_kprobe(kcb);
404 goto out;
405 }
406 reset_current_kprobe();
407out:
408 preempt_enable_no_resched();
409
410 /*
411 * if somebody else is singlestepping across a probe point, msr
412 * will have DE/SE set, in which case, continue the remaining processing
413 * of do_debug, as if this is not a probe hit.
414 */
415 if (regs->msr & MSR_SINGLESTEP)
416 return 0;
417
418 return 1;
419}
420
421int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
422{
423 struct kprobe *cur = kprobe_running();
424 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
425 const struct exception_table_entry *entry;
426
427 switch(kcb->kprobe_status) {
428 case KPROBE_HIT_SS:
429 case KPROBE_REENTER:
430 /*
431 * We are here because the instruction being single
432 * stepped caused a page fault. We reset the current
433 * kprobe and the nip points back to the probe address
434 * and allow the page fault handler to continue as a
435 * normal page fault.
436 */
437 regs->nip = (unsigned long)cur->addr;
438 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
439 regs->msr |= kcb->kprobe_saved_msr;
440 if (kcb->kprobe_status == KPROBE_REENTER)
441 restore_previous_kprobe(kcb);
442 else
443 reset_current_kprobe();
444 preempt_enable_no_resched();
445 break;
446 case KPROBE_HIT_ACTIVE:
447 case KPROBE_HIT_SSDONE:
448 /*
449 * We increment the nmissed count for accounting,
450 * we can also use npre/npostfault count for accouting
451 * these specific fault cases.
452 */
453 kprobes_inc_nmissed_count(cur);
454
455 /*
456 * We come here because instructions in the pre/post
457 * handler caused the page_fault, this could happen
458 * if handler tries to access user space by
459 * copy_from_user(), get_user() etc. Let the
460 * user-specified handler try to fix it first.
461 */
462 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
463 return 1;
464
465 /*
466 * In case the user-specified fault handler returned
467 * zero, try to fix up.
468 */
469 if ((entry = search_exception_tables(regs->nip)) != NULL) {
470 regs->nip = entry->fixup;
471 return 1;
472 }
473
474 /*
475 * fixup_exception() could not handle it,
476 * Let do_page_fault() fix it.
477 */
478 break;
479 default:
480 break;
481 }
482 return 0;
483}
484
485/*
486 * Wrapper routine to for handling exceptions.
487 */
488int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
489 unsigned long val, void *data)
490{
491 struct die_args *args = (struct die_args *)data;
492 int ret = NOTIFY_DONE;
493
494 if (args->regs && user_mode(args->regs))
495 return ret;
496
497 switch (val) {
498 case DIE_BPT:
499 if (kprobe_handler(args->regs))
500 ret = NOTIFY_STOP;
501 break;
502 case DIE_SSTEP:
503 if (post_kprobe_handler(args->regs))
504 ret = NOTIFY_STOP;
505 break;
506 default:
507 break;
508 }
509 return ret;
510}
511
512#ifdef CONFIG_PPC64
513unsigned long arch_deref_entry_point(void *entry)
514{
515 return ((func_descr_t *)entry)->entry;
516}
517#endif
518
519int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
520{
521 struct jprobe *jp = container_of(p, struct jprobe, kp);
522 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
523
524 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
525
526 /* setup return addr to the jprobe handler routine */
527 regs->nip = arch_deref_entry_point(jp->entry);
528#ifdef CONFIG_PPC64
529 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
530#endif
531
532 return 1;
533}
534
535void __used __kprobes jprobe_return(void)
536{
537 asm volatile("trap" ::: "memory");
538}
539
540static void __used __kprobes jprobe_return_end(void)
541{
542};
543
544int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
545{
546 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
547
548 /*
549 * FIXME - we should ideally be validating that we got here 'cos
550 * of the "trap" in jprobe_return() above, before restoring the
551 * saved regs...
552 */
553 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
554 preempt_enable_no_resched();
555 return 1;
556}
557
558static struct kprobe trampoline_p = {
559 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
560 .pre_handler = trampoline_probe_handler
561};
562
563int __init arch_init_kprobes(void)
564{
565 return register_kprobe(&trampoline_p);
566}
567
568int __kprobes arch_trampoline_kprobe(struct kprobe *p)
569{
570 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
571 return 1;
572
573 return 0;
574}