2 * Kernel Probes (KProbes)
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.
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.
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.
18 * Copyright (C) IBM Corporation, 2002, 2004
20 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
21 * Probes initial implementation ( includes contributions from
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
29 #include <linux/kprobes.h>
30 #include <linux/ptrace.h>
31 #include <linux/preempt.h>
32 #include <linux/extable.h>
33 #include <linux/kdebug.h>
34 #include <linux/slab.h>
35 #include <asm/code-patching.h>
36 #include <asm/cacheflush.h>
37 #include <asm/sstep.h>
38 #include <asm/sections.h>
39 #include <linux/uaccess.h>
41 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
42 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
44 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
46 bool arch_within_kprobe_blacklist(unsigned long addr)
48 return (addr >= (unsigned long)__kprobes_text_start &&
49 addr < (unsigned long)__kprobes_text_end) ||
50 (addr >= (unsigned long)_stext &&
51 addr < (unsigned long)__head_end);
54 kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
56 kprobe_opcode_t *addr = NULL;
58 #ifdef PPC64_ELF_ABI_v2
59 /* PPC64 ABIv2 needs local entry point */
60 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
61 if (addr && !offset) {
62 #ifdef CONFIG_KPROBES_ON_FTRACE
65 * Per livepatch.h, ftrace location is always within the first
66 * 16 bytes of a function on powerpc with -mprofile-kernel.
68 faddr = ftrace_location_range((unsigned long)addr,
69 (unsigned long)addr + 16);
71 addr = (kprobe_opcode_t *)faddr;
74 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
76 #elif defined(PPC64_ELF_ABI_v1)
78 * 64bit powerpc ABIv1 uses function descriptors:
79 * - Check for the dot variant of the symbol first.
80 * - If that fails, try looking up the symbol provided.
82 * This ensures we always get to the actual symbol and not
85 * Also handle <module:symbol> format.
87 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
88 bool dot_appended = false;
93 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
96 memcpy(dot_name, name, len);
100 if (*c != '\0' && *c != '.') {
101 dot_name[len++] = '.';
104 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
106 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
108 /* Fallback to the original non-dot symbol lookup */
109 if (!addr && dot_appended)
110 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
112 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
118 int arch_prepare_kprobe(struct kprobe *p)
121 kprobe_opcode_t insn = *p->addr;
123 if ((unsigned long)p->addr & 0x03) {
124 printk("Attempt to register kprobe at an unaligned address\n");
126 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
127 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
131 /* insn must be on a special executable page on ppc64. This is
132 * not explicitly required on ppc32 (right now), but it doesn't hurt */
134 p->ainsn.insn = get_insn_slot();
140 memcpy(p->ainsn.insn, p->addr,
141 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
142 p->opcode = *p->addr;
143 flush_icache_range((unsigned long)p->ainsn.insn,
144 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
147 p->ainsn.boostable = 0;
150 NOKPROBE_SYMBOL(arch_prepare_kprobe);
152 void arch_arm_kprobe(struct kprobe *p)
154 patch_instruction(p->addr, BREAKPOINT_INSTRUCTION);
156 NOKPROBE_SYMBOL(arch_arm_kprobe);
158 void arch_disarm_kprobe(struct kprobe *p)
160 patch_instruction(p->addr, p->opcode);
162 NOKPROBE_SYMBOL(arch_disarm_kprobe);
164 void arch_remove_kprobe(struct kprobe *p)
167 free_insn_slot(p->ainsn.insn, 0);
168 p->ainsn.insn = NULL;
171 NOKPROBE_SYMBOL(arch_remove_kprobe);
173 static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
175 enable_single_step(regs);
178 * On powerpc we should single step on the original
179 * instruction even if the probed insn is a trap
180 * variant as values in regs could play a part in
181 * if the trap is taken or not
183 regs->nip = (unsigned long)p->ainsn.insn;
186 static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
188 kcb->prev_kprobe.kp = kprobe_running();
189 kcb->prev_kprobe.status = kcb->kprobe_status;
190 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
193 static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
195 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
196 kcb->kprobe_status = kcb->prev_kprobe.status;
197 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
200 static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
201 struct kprobe_ctlblk *kcb)
203 __this_cpu_write(current_kprobe, p);
204 kcb->kprobe_saved_msr = regs->msr;
207 bool arch_kprobe_on_func_entry(unsigned long offset)
209 #ifdef PPC64_ELF_ABI_v2
210 #ifdef CONFIG_KPROBES_ON_FTRACE
220 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
222 ri->ret_addr = (kprobe_opcode_t *)regs->link;
224 /* Replace the return addr with trampoline addr */
225 regs->link = (unsigned long)kretprobe_trampoline;
227 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
229 static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
232 unsigned int insn = *p->ainsn.insn;
234 /* regs->nip is also adjusted if emulate_step returns 1 */
235 ret = emulate_step(regs, insn);
238 * Once this instruction has been boosted
239 * successfully, set the boostable flag
241 if (unlikely(p->ainsn.boostable == 0))
242 p->ainsn.boostable = 1;
243 } else if (ret < 0) {
245 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
246 * So, we should never get here... but, its still
247 * good to catch them, just in case...
249 printk("Can't step on instruction %x\n", insn);
253 * If we haven't previously emulated this instruction, then it
254 * can't be boosted. Note it down so we don't try to do so again.
256 * If, however, we had emulated this instruction in the past,
257 * then this is just an error with the current run (for
258 * instance, exceptions due to a load/store). We return 0 so
259 * that this is now single-stepped, but continue to try
260 * emulating it in subsequent probe hits.
262 if (unlikely(p->ainsn.boostable != 1))
263 p->ainsn.boostable = -1;
268 NOKPROBE_SYMBOL(try_to_emulate);
270 int kprobe_handler(struct pt_regs *regs)
274 unsigned int *addr = (unsigned int *)regs->nip;
275 struct kprobe_ctlblk *kcb;
280 if (!IS_ENABLED(CONFIG_BOOKE) &&
281 (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
285 * We don't want to be preempted for the entire
286 * duration of kprobe processing
289 kcb = get_kprobe_ctlblk();
291 /* Check we're not actually recursing */
292 if (kprobe_running()) {
293 p = get_kprobe(addr);
295 kprobe_opcode_t insn = *p->ainsn.insn;
296 if (kcb->kprobe_status == KPROBE_HIT_SS &&
298 /* Turn off 'trace' bits */
299 regs->msr &= ~MSR_SINGLESTEP;
300 regs->msr |= kcb->kprobe_saved_msr;
303 /* We have reentered the kprobe_handler(), since
304 * another probe was hit while within the handler.
305 * We here save the original kprobes variables and
306 * just single step on the instruction of the new probe
307 * without calling any user handlers.
309 save_previous_kprobe(kcb);
310 set_current_kprobe(p, regs, kcb);
311 kprobes_inc_nmissed_count(p);
312 kcb->kprobe_status = KPROBE_REENTER;
313 if (p->ainsn.boostable >= 0) {
314 ret = try_to_emulate(p, regs);
317 restore_previous_kprobe(kcb);
318 preempt_enable_no_resched();
322 prepare_singlestep(p, regs);
324 } else if (*addr != BREAKPOINT_INSTRUCTION) {
325 /* If trap variant, then it belongs not to us */
326 kprobe_opcode_t cur_insn = *addr;
328 if (is_trap(cur_insn))
330 /* The breakpoint instruction was removed by
331 * another cpu right after we hit, no further
332 * handling of this interrupt is appropriate
339 p = get_kprobe(addr);
341 if (*addr != BREAKPOINT_INSTRUCTION) {
343 * PowerPC has multiple variants of the "trap"
344 * instruction. If the current instruction is a
345 * trap variant, it could belong to someone else
347 kprobe_opcode_t cur_insn = *addr;
348 if (is_trap(cur_insn))
351 * The breakpoint instruction was removed right
352 * after we hit it. Another cpu has removed
353 * either a probepoint or a debugger breakpoint
354 * at this address. In either case, no further
355 * handling of this interrupt is appropriate.
359 /* Not one of ours: let kernel handle it */
363 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
364 set_current_kprobe(p, regs, kcb);
365 if (p->pre_handler && p->pre_handler(p, regs)) {
366 /* handler changed execution path, so skip ss setup */
367 reset_current_kprobe();
368 preempt_enable_no_resched();
372 if (p->ainsn.boostable >= 0) {
373 ret = try_to_emulate(p, regs);
377 p->post_handler(p, regs, 0);
379 kcb->kprobe_status = KPROBE_HIT_SSDONE;
380 reset_current_kprobe();
381 preempt_enable_no_resched();
385 prepare_singlestep(p, regs);
386 kcb->kprobe_status = KPROBE_HIT_SS;
390 preempt_enable_no_resched();
393 NOKPROBE_SYMBOL(kprobe_handler);
396 * Function return probe trampoline:
397 * - init_kprobes() establishes a probepoint here
398 * - When the probed function returns, this probe
399 * causes the handlers to fire
401 asm(".global kretprobe_trampoline\n"
402 ".type kretprobe_trampoline, @function\n"
403 "kretprobe_trampoline:\n"
406 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
409 * Called when the probe at kretprobe trampoline is hit
411 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
413 struct kretprobe_instance *ri = NULL;
414 struct hlist_head *head, empty_rp;
415 struct hlist_node *tmp;
416 unsigned long flags, orig_ret_address = 0;
417 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
419 INIT_HLIST_HEAD(&empty_rp);
420 kretprobe_hash_lock(current, &head, &flags);
423 * It is possible to have multiple instances associated with a given
424 * task either because an multiple functions in the call path
425 * have a return probe installed on them, and/or more than one return
426 * return probe was registered for a target function.
428 * We can handle this because:
429 * - instances are always inserted at the head of the list
430 * - when multiple return probes are registered for the same
431 * function, the first instance's ret_addr will point to the
432 * real return address, and all the rest will point to
433 * kretprobe_trampoline
435 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
436 if (ri->task != current)
437 /* another task is sharing our hash bucket */
440 if (ri->rp && ri->rp->handler)
441 ri->rp->handler(ri, regs);
443 orig_ret_address = (unsigned long)ri->ret_addr;
444 recycle_rp_inst(ri, &empty_rp);
446 if (orig_ret_address != trampoline_address)
448 * This is the real return address. Any other
449 * instances associated with this task are for
450 * other calls deeper on the call stack
455 kretprobe_assert(ri, orig_ret_address, trampoline_address);
458 * We get here through one of two paths:
459 * 1. by taking a trap -> kprobe_handler() -> here
460 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
462 * When going back through (1), we need regs->nip to be setup properly
463 * as it is used to determine the return address from the trap.
464 * For (2), since nip is not honoured with optprobes, we instead setup
465 * the link register properly so that the subsequent 'blr' in
466 * kretprobe_trampoline jumps back to the right instruction.
468 * For nip, we should set the address to the previous instruction since
469 * we end up emulating it in kprobe_handler(), which increments the nip
472 regs->nip = orig_ret_address - 4;
473 regs->link = orig_ret_address;
475 kretprobe_hash_unlock(current, &flags);
477 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
478 hlist_del(&ri->hlist);
484 NOKPROBE_SYMBOL(trampoline_probe_handler);
487 * Called after single-stepping. p->addr is the address of the
488 * instruction whose first byte has been replaced by the "breakpoint"
489 * instruction. To avoid the SMP problems that can occur when we
490 * temporarily put back the original opcode to single-step, we
491 * single-stepped a copy of the instruction. The address of this
492 * copy is p->ainsn.insn.
494 int kprobe_post_handler(struct pt_regs *regs)
496 struct kprobe *cur = kprobe_running();
497 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
499 if (!cur || user_mode(regs))
502 /* make sure we got here for instruction we have a kprobe on */
503 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
506 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
507 kcb->kprobe_status = KPROBE_HIT_SSDONE;
508 cur->post_handler(cur, regs, 0);
511 /* Adjust nip to after the single-stepped instruction */
512 regs->nip = (unsigned long)cur->addr + 4;
513 regs->msr |= kcb->kprobe_saved_msr;
515 /*Restore back the original saved kprobes variables and continue. */
516 if (kcb->kprobe_status == KPROBE_REENTER) {
517 restore_previous_kprobe(kcb);
520 reset_current_kprobe();
522 preempt_enable_no_resched();
525 * if somebody else is singlestepping across a probe point, msr
526 * will have DE/SE set, in which case, continue the remaining processing
527 * of do_debug, as if this is not a probe hit.
529 if (regs->msr & MSR_SINGLESTEP)
534 NOKPROBE_SYMBOL(kprobe_post_handler);
536 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
538 struct kprobe *cur = kprobe_running();
539 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
540 const struct exception_table_entry *entry;
542 switch(kcb->kprobe_status) {
546 * We are here because the instruction being single
547 * stepped caused a page fault. We reset the current
548 * kprobe and the nip points back to the probe address
549 * and allow the page fault handler to continue as a
552 regs->nip = (unsigned long)cur->addr;
553 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
554 regs->msr |= kcb->kprobe_saved_msr;
555 if (kcb->kprobe_status == KPROBE_REENTER)
556 restore_previous_kprobe(kcb);
558 reset_current_kprobe();
559 preempt_enable_no_resched();
561 case KPROBE_HIT_ACTIVE:
562 case KPROBE_HIT_SSDONE:
564 * We increment the nmissed count for accounting,
565 * we can also use npre/npostfault count for accounting
566 * these specific fault cases.
568 kprobes_inc_nmissed_count(cur);
571 * We come here because instructions in the pre/post
572 * handler caused the page_fault, this could happen
573 * if handler tries to access user space by
574 * copy_from_user(), get_user() etc. Let the
575 * user-specified handler try to fix it first.
577 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
581 * In case the user-specified fault handler returned
582 * zero, try to fix up.
584 if ((entry = search_exception_tables(regs->nip)) != NULL) {
585 regs->nip = extable_fixup(entry);
590 * fixup_exception() could not handle it,
591 * Let do_page_fault() fix it.
599 NOKPROBE_SYMBOL(kprobe_fault_handler);
601 unsigned long arch_deref_entry_point(void *entry)
603 #ifdef PPC64_ELF_ABI_v1
604 if (!kernel_text_address((unsigned long)entry))
605 return ppc_global_function_entry(entry);
608 return (unsigned long)entry;
610 NOKPROBE_SYMBOL(arch_deref_entry_point);
612 static struct kprobe trampoline_p = {
613 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
614 .pre_handler = trampoline_probe_handler
617 int __init arch_init_kprobes(void)
619 return register_kprobe(&trampoline_p);
622 int arch_trampoline_kprobe(struct kprobe *p)
624 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
629 NOKPROBE_SYMBOL(arch_trampoline_kprobe);