1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Kernel Probes (KProbes)
5 * Copyright (C) IBM Corporation, 2002, 2004
7 * 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
8 * Probes initial implementation ( includes contributions from
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
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 <linux/uaccess.h>
28 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
29 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
31 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
33 bool arch_within_kprobe_blacklist(unsigned long addr)
35 return (addr >= (unsigned long)__kprobes_text_start &&
36 addr < (unsigned long)__kprobes_text_end) ||
37 (addr >= (unsigned long)_stext &&
38 addr < (unsigned long)__head_end);
41 kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
43 kprobe_opcode_t *addr = NULL;
45 #ifdef PPC64_ELF_ABI_v2
46 /* PPC64 ABIv2 needs local entry point */
47 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
48 if (addr && !offset) {
49 #ifdef CONFIG_KPROBES_ON_FTRACE
52 * Per livepatch.h, ftrace location is always within the first
53 * 16 bytes of a function on powerpc with -mprofile-kernel.
55 faddr = ftrace_location_range((unsigned long)addr,
56 (unsigned long)addr + 16);
58 addr = (kprobe_opcode_t *)faddr;
61 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
63 #elif defined(PPC64_ELF_ABI_v1)
65 * 64bit powerpc ABIv1 uses function descriptors:
66 * - Check for the dot variant of the symbol first.
67 * - If that fails, try looking up the symbol provided.
69 * This ensures we always get to the actual symbol and not
72 * Also handle <module:symbol> format.
74 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
75 bool dot_appended = false;
80 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
83 memcpy(dot_name, name, len);
87 if (*c != '\0' && *c != '.') {
88 dot_name[len++] = '.';
91 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
93 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
95 /* Fallback to the original non-dot symbol lookup */
96 if (!addr && dot_appended)
97 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
99 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
105 int arch_prepare_kprobe(struct kprobe *p)
108 kprobe_opcode_t insn = *p->addr;
110 if ((unsigned long)p->addr & 0x03) {
111 printk("Attempt to register kprobe at an unaligned address\n");
113 } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
114 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
118 /* insn must be on a special executable page on ppc64. This is
119 * not explicitly required on ppc32 (right now), but it doesn't hurt */
121 p->ainsn.insn = get_insn_slot();
127 memcpy(p->ainsn.insn, p->addr,
128 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
129 p->opcode = *p->addr;
130 flush_icache_range((unsigned long)p->ainsn.insn,
131 (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
134 p->ainsn.boostable = 0;
137 NOKPROBE_SYMBOL(arch_prepare_kprobe);
139 void arch_arm_kprobe(struct kprobe *p)
141 patch_instruction(p->addr, BREAKPOINT_INSTRUCTION);
143 NOKPROBE_SYMBOL(arch_arm_kprobe);
145 void arch_disarm_kprobe(struct kprobe *p)
147 patch_instruction(p->addr, p->opcode);
149 NOKPROBE_SYMBOL(arch_disarm_kprobe);
151 void arch_remove_kprobe(struct kprobe *p)
154 free_insn_slot(p->ainsn.insn, 0);
155 p->ainsn.insn = NULL;
158 NOKPROBE_SYMBOL(arch_remove_kprobe);
160 static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
162 enable_single_step(regs);
165 * On powerpc we should single step on the original
166 * instruction even if the probed insn is a trap
167 * variant as values in regs could play a part in
168 * if the trap is taken or not
170 regs->nip = (unsigned long)p->ainsn.insn;
173 static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
175 kcb->prev_kprobe.kp = kprobe_running();
176 kcb->prev_kprobe.status = kcb->kprobe_status;
177 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
180 static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
182 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
183 kcb->kprobe_status = kcb->prev_kprobe.status;
184 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
187 static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
188 struct kprobe_ctlblk *kcb)
190 __this_cpu_write(current_kprobe, p);
191 kcb->kprobe_saved_msr = regs->msr;
194 bool arch_kprobe_on_func_entry(unsigned long offset)
196 #ifdef PPC64_ELF_ABI_v2
197 #ifdef CONFIG_KPROBES_ON_FTRACE
207 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
209 ri->ret_addr = (kprobe_opcode_t *)regs->link;
211 /* Replace the return addr with trampoline addr */
212 regs->link = (unsigned long)kretprobe_trampoline;
214 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
216 static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
219 unsigned int insn = *p->ainsn.insn;
221 /* regs->nip is also adjusted if emulate_step returns 1 */
222 ret = emulate_step(regs, insn);
225 * Once this instruction has been boosted
226 * successfully, set the boostable flag
228 if (unlikely(p->ainsn.boostable == 0))
229 p->ainsn.boostable = 1;
230 } else if (ret < 0) {
232 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
233 * So, we should never get here... but, its still
234 * good to catch them, just in case...
236 printk("Can't step on instruction %x\n", insn);
240 * If we haven't previously emulated this instruction, then it
241 * can't be boosted. Note it down so we don't try to do so again.
243 * If, however, we had emulated this instruction in the past,
244 * then this is just an error with the current run (for
245 * instance, exceptions due to a load/store). We return 0 so
246 * that this is now single-stepped, but continue to try
247 * emulating it in subsequent probe hits.
249 if (unlikely(p->ainsn.boostable != 1))
250 p->ainsn.boostable = -1;
255 NOKPROBE_SYMBOL(try_to_emulate);
257 int kprobe_handler(struct pt_regs *regs)
261 unsigned int *addr = (unsigned int *)regs->nip;
262 struct kprobe_ctlblk *kcb;
267 if (!IS_ENABLED(CONFIG_BOOKE) &&
268 (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
272 * We don't want to be preempted for the entire
273 * duration of kprobe processing
276 kcb = get_kprobe_ctlblk();
278 /* Check we're not actually recursing */
279 if (kprobe_running()) {
280 p = get_kprobe(addr);
282 kprobe_opcode_t insn = *p->ainsn.insn;
283 if (kcb->kprobe_status == KPROBE_HIT_SS &&
285 /* Turn off 'trace' bits */
286 regs->msr &= ~MSR_SINGLESTEP;
287 regs->msr |= kcb->kprobe_saved_msr;
290 /* We have reentered the kprobe_handler(), since
291 * another probe was hit while within the handler.
292 * We here save the original kprobes variables and
293 * just single step on the instruction of the new probe
294 * without calling any user handlers.
296 save_previous_kprobe(kcb);
297 set_current_kprobe(p, regs, kcb);
298 kprobes_inc_nmissed_count(p);
299 kcb->kprobe_status = KPROBE_REENTER;
300 if (p->ainsn.boostable >= 0) {
301 ret = try_to_emulate(p, regs);
304 restore_previous_kprobe(kcb);
305 preempt_enable_no_resched();
309 prepare_singlestep(p, regs);
311 } else if (*addr != BREAKPOINT_INSTRUCTION) {
312 /* If trap variant, then it belongs not to us */
313 kprobe_opcode_t cur_insn = *addr;
315 if (is_trap(cur_insn))
317 /* The breakpoint instruction was removed by
318 * another cpu right after we hit, no further
319 * handling of this interrupt is appropriate
326 p = get_kprobe(addr);
328 if (*addr != BREAKPOINT_INSTRUCTION) {
330 * PowerPC has multiple variants of the "trap"
331 * instruction. If the current instruction is a
332 * trap variant, it could belong to someone else
334 kprobe_opcode_t cur_insn = *addr;
335 if (is_trap(cur_insn))
338 * The breakpoint instruction was removed right
339 * after we hit it. Another cpu has removed
340 * either a probepoint or a debugger breakpoint
341 * at this address. In either case, no further
342 * handling of this interrupt is appropriate.
346 /* Not one of ours: let kernel handle it */
350 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
351 set_current_kprobe(p, regs, kcb);
352 if (p->pre_handler && p->pre_handler(p, regs)) {
353 /* handler changed execution path, so skip ss setup */
354 reset_current_kprobe();
355 preempt_enable_no_resched();
359 if (p->ainsn.boostable >= 0) {
360 ret = try_to_emulate(p, regs);
364 p->post_handler(p, regs, 0);
366 kcb->kprobe_status = KPROBE_HIT_SSDONE;
367 reset_current_kprobe();
368 preempt_enable_no_resched();
372 prepare_singlestep(p, regs);
373 kcb->kprobe_status = KPROBE_HIT_SS;
377 preempt_enable_no_resched();
380 NOKPROBE_SYMBOL(kprobe_handler);
383 * Function return probe trampoline:
384 * - init_kprobes() establishes a probepoint here
385 * - When the probed function returns, this probe
386 * causes the handlers to fire
388 asm(".global kretprobe_trampoline\n"
389 ".type kretprobe_trampoline, @function\n"
390 "kretprobe_trampoline:\n"
393 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
396 * Called when the probe at kretprobe trampoline is hit
398 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
400 struct kretprobe_instance *ri = NULL;
401 struct hlist_head *head, empty_rp;
402 struct hlist_node *tmp;
403 unsigned long flags, orig_ret_address = 0;
404 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
406 INIT_HLIST_HEAD(&empty_rp);
407 kretprobe_hash_lock(current, &head, &flags);
410 * It is possible to have multiple instances associated with a given
411 * task either because an multiple functions in the call path
412 * have a return probe installed on them, and/or more than one return
413 * return probe was registered for a target function.
415 * We can handle this because:
416 * - instances are always inserted at the head of the list
417 * - when multiple return probes are registered for the same
418 * function, the first instance's ret_addr will point to the
419 * real return address, and all the rest will point to
420 * kretprobe_trampoline
422 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
423 if (ri->task != current)
424 /* another task is sharing our hash bucket */
427 if (ri->rp && ri->rp->handler)
428 ri->rp->handler(ri, regs);
430 orig_ret_address = (unsigned long)ri->ret_addr;
431 recycle_rp_inst(ri, &empty_rp);
433 if (orig_ret_address != trampoline_address)
435 * This is the real return address. Any other
436 * instances associated with this task are for
437 * other calls deeper on the call stack
442 kretprobe_assert(ri, orig_ret_address, trampoline_address);
445 * We get here through one of two paths:
446 * 1. by taking a trap -> kprobe_handler() -> here
447 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
449 * When going back through (1), we need regs->nip to be setup properly
450 * as it is used to determine the return address from the trap.
451 * For (2), since nip is not honoured with optprobes, we instead setup
452 * the link register properly so that the subsequent 'blr' in
453 * kretprobe_trampoline jumps back to the right instruction.
455 * For nip, we should set the address to the previous instruction since
456 * we end up emulating it in kprobe_handler(), which increments the nip
459 regs->nip = orig_ret_address - 4;
460 regs->link = orig_ret_address;
462 kretprobe_hash_unlock(current, &flags);
464 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
465 hlist_del(&ri->hlist);
471 NOKPROBE_SYMBOL(trampoline_probe_handler);
474 * Called after single-stepping. p->addr is the address of the
475 * instruction whose first byte has been replaced by the "breakpoint"
476 * instruction. To avoid the SMP problems that can occur when we
477 * temporarily put back the original opcode to single-step, we
478 * single-stepped a copy of the instruction. The address of this
479 * copy is p->ainsn.insn.
481 int kprobe_post_handler(struct pt_regs *regs)
483 struct kprobe *cur = kprobe_running();
484 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
486 if (!cur || user_mode(regs))
489 /* make sure we got here for instruction we have a kprobe on */
490 if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
493 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
494 kcb->kprobe_status = KPROBE_HIT_SSDONE;
495 cur->post_handler(cur, regs, 0);
498 /* Adjust nip to after the single-stepped instruction */
499 regs->nip = (unsigned long)cur->addr + 4;
500 regs->msr |= kcb->kprobe_saved_msr;
502 /*Restore back the original saved kprobes variables and continue. */
503 if (kcb->kprobe_status == KPROBE_REENTER) {
504 restore_previous_kprobe(kcb);
507 reset_current_kprobe();
509 preempt_enable_no_resched();
512 * if somebody else is singlestepping across a probe point, msr
513 * will have DE/SE set, in which case, continue the remaining processing
514 * of do_debug, as if this is not a probe hit.
516 if (regs->msr & MSR_SINGLESTEP)
521 NOKPROBE_SYMBOL(kprobe_post_handler);
523 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
525 struct kprobe *cur = kprobe_running();
526 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
527 const struct exception_table_entry *entry;
529 switch(kcb->kprobe_status) {
533 * We are here because the instruction being single
534 * stepped caused a page fault. We reset the current
535 * kprobe and the nip points back to the probe address
536 * and allow the page fault handler to continue as a
539 regs->nip = (unsigned long)cur->addr;
540 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
541 regs->msr |= kcb->kprobe_saved_msr;
542 if (kcb->kprobe_status == KPROBE_REENTER)
543 restore_previous_kprobe(kcb);
545 reset_current_kprobe();
546 preempt_enable_no_resched();
548 case KPROBE_HIT_ACTIVE:
549 case KPROBE_HIT_SSDONE:
551 * We increment the nmissed count for accounting,
552 * we can also use npre/npostfault count for accounting
553 * these specific fault cases.
555 kprobes_inc_nmissed_count(cur);
558 * We come here because instructions in the pre/post
559 * handler caused the page_fault, this could happen
560 * if handler tries to access user space by
561 * copy_from_user(), get_user() etc. Let the
562 * user-specified handler try to fix it first.
564 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
568 * In case the user-specified fault handler returned
569 * zero, try to fix up.
571 if ((entry = search_exception_tables(regs->nip)) != NULL) {
572 regs->nip = extable_fixup(entry);
577 * fixup_exception() could not handle it,
578 * Let do_page_fault() fix it.
586 NOKPROBE_SYMBOL(kprobe_fault_handler);
588 unsigned long arch_deref_entry_point(void *entry)
590 #ifdef PPC64_ELF_ABI_v1
591 if (!kernel_text_address((unsigned long)entry))
592 return ppc_global_function_entry(entry);
595 return (unsigned long)entry;
597 NOKPROBE_SYMBOL(arch_deref_entry_point);
599 static struct kprobe trampoline_p = {
600 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
601 .pre_handler = trampoline_probe_handler
604 int __init arch_init_kprobes(void)
606 return register_kprobe(&trampoline_p);
609 int arch_trampoline_kprobe(struct kprobe *p)
611 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
616 NOKPROBE_SYMBOL(arch_trampoline_kprobe);