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 <linux/moduleloader.h>
23 #include <asm/code-patching.h>
24 #include <asm/cacheflush.h>
25 #include <asm/sstep.h>
26 #include <asm/sections.h>
28 #include <asm/set_memory.h>
29 #include <linux/uaccess.h>
31 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
32 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
34 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
36 bool arch_within_kprobe_blacklist(unsigned long addr)
38 return (addr >= (unsigned long)__kprobes_text_start &&
39 addr < (unsigned long)__kprobes_text_end) ||
40 (addr >= (unsigned long)_stext &&
41 addr < (unsigned long)__head_end);
44 kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
46 kprobe_opcode_t *addr = NULL;
48 #ifdef PPC64_ELF_ABI_v2
49 /* PPC64 ABIv2 needs local entry point */
50 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
51 if (addr && !offset) {
52 #ifdef CONFIG_KPROBES_ON_FTRACE
55 * Per livepatch.h, ftrace location is always within the first
56 * 16 bytes of a function on powerpc with -mprofile-kernel.
58 faddr = ftrace_location_range((unsigned long)addr,
59 (unsigned long)addr + 16);
61 addr = (kprobe_opcode_t *)faddr;
64 addr = (kprobe_opcode_t *)ppc_function_entry(addr);
66 #elif defined(PPC64_ELF_ABI_v1)
68 * 64bit powerpc ABIv1 uses function descriptors:
69 * - Check for the dot variant of the symbol first.
70 * - If that fails, try looking up the symbol provided.
72 * This ensures we always get to the actual symbol and not
75 * Also handle <module:symbol> format.
77 char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
78 bool dot_appended = false;
83 if ((c = strnchr(name, MODULE_NAME_LEN, ':')) != NULL) {
86 memcpy(dot_name, name, len);
90 if (*c != '\0' && *c != '.') {
91 dot_name[len++] = '.';
94 ret = strscpy(dot_name + len, c, KSYM_NAME_LEN);
96 addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
98 /* Fallback to the original non-dot symbol lookup */
99 if (!addr && dot_appended)
100 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
102 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
108 void *alloc_insn_page(void)
112 page = module_alloc(PAGE_SIZE);
116 if (strict_module_rwx_enabled()) {
117 set_memory_ro((unsigned long)page, 1);
118 set_memory_x((unsigned long)page, 1);
123 int arch_prepare_kprobe(struct kprobe *p)
127 struct ppc_inst insn = ppc_inst_read(p->addr);
129 if ((unsigned long)p->addr & 0x03) {
130 printk("Attempt to register kprobe at an unaligned address\n");
132 } else if (IS_MTMSRD(insn) || IS_RFID(insn)) {
133 printk("Cannot register a kprobe on mtmsr[d]/rfi[d]\n");
135 } else if ((unsigned long)p->addr & ~PAGE_MASK &&
136 ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) {
137 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
141 prev = get_kprobe(p->addr - 1);
142 preempt_enable_no_resched();
143 if (prev && ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
144 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
148 /* insn must be on a special executable page on ppc64. This is
149 * not explicitly required on ppc32 (right now), but it doesn't hurt */
151 p->ainsn.insn = get_insn_slot();
157 patch_instruction(p->ainsn.insn, insn);
158 p->opcode = ppc_inst_val(insn);
161 p->ainsn.boostable = 0;
164 NOKPROBE_SYMBOL(arch_prepare_kprobe);
166 void arch_arm_kprobe(struct kprobe *p)
168 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(BREAKPOINT_INSTRUCTION)));
170 NOKPROBE_SYMBOL(arch_arm_kprobe);
172 void arch_disarm_kprobe(struct kprobe *p)
174 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(p->opcode)));
176 NOKPROBE_SYMBOL(arch_disarm_kprobe);
178 void arch_remove_kprobe(struct kprobe *p)
181 free_insn_slot(p->ainsn.insn, 0);
182 p->ainsn.insn = NULL;
185 NOKPROBE_SYMBOL(arch_remove_kprobe);
187 static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
189 enable_single_step(regs);
192 * On powerpc we should single step on the original
193 * instruction even if the probed insn is a trap
194 * variant as values in regs could play a part in
195 * if the trap is taken or not
197 regs_set_return_ip(regs, (unsigned long)p->ainsn.insn);
200 static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
202 kcb->prev_kprobe.kp = kprobe_running();
203 kcb->prev_kprobe.status = kcb->kprobe_status;
204 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
207 static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
209 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
210 kcb->kprobe_status = kcb->prev_kprobe.status;
211 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
214 static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
215 struct kprobe_ctlblk *kcb)
217 __this_cpu_write(current_kprobe, p);
218 kcb->kprobe_saved_msr = regs->msr;
221 bool arch_kprobe_on_func_entry(unsigned long offset)
223 #ifdef PPC64_ELF_ABI_v2
224 #ifdef CONFIG_KPROBES_ON_FTRACE
234 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
236 ri->ret_addr = (kprobe_opcode_t *)regs->link;
239 /* Replace the return addr with trampoline addr */
240 regs->link = (unsigned long)kretprobe_trampoline;
242 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
244 static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
247 struct ppc_inst insn = ppc_inst_read(p->ainsn.insn);
249 /* regs->nip is also adjusted if emulate_step returns 1 */
250 ret = emulate_step(regs, insn);
253 * Once this instruction has been boosted
254 * successfully, set the boostable flag
256 if (unlikely(p->ainsn.boostable == 0))
257 p->ainsn.boostable = 1;
258 } else if (ret < 0) {
260 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
261 * So, we should never get here... but, its still
262 * good to catch them, just in case...
264 printk("Can't step on instruction %s\n", ppc_inst_as_str(insn));
268 * If we haven't previously emulated this instruction, then it
269 * can't be boosted. Note it down so we don't try to do so again.
271 * If, however, we had emulated this instruction in the past,
272 * then this is just an error with the current run (for
273 * instance, exceptions due to a load/store). We return 0 so
274 * that this is now single-stepped, but continue to try
275 * emulating it in subsequent probe hits.
277 if (unlikely(p->ainsn.boostable != 1))
278 p->ainsn.boostable = -1;
283 NOKPROBE_SYMBOL(try_to_emulate);
285 int kprobe_handler(struct pt_regs *regs)
289 unsigned int *addr = (unsigned int *)regs->nip;
290 struct kprobe_ctlblk *kcb;
295 if (!IS_ENABLED(CONFIG_BOOKE) &&
296 (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
300 * We don't want to be preempted for the entire
301 * duration of kprobe processing
304 kcb = get_kprobe_ctlblk();
306 p = get_kprobe(addr);
310 if (get_kernel_nofault(instr, addr))
313 if (instr != BREAKPOINT_INSTRUCTION) {
315 * PowerPC has multiple variants of the "trap"
316 * instruction. If the current instruction is a
317 * trap variant, it could belong to someone else
322 * The breakpoint instruction was removed right
323 * after we hit it. Another cpu has removed
324 * either a probepoint or a debugger breakpoint
325 * at this address. In either case, no further
326 * handling of this interrupt is appropriate.
330 /* Not one of ours: let kernel handle it */
334 /* Check we're not actually recursing */
335 if (kprobe_running()) {
336 kprobe_opcode_t insn = *p->ainsn.insn;
337 if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
338 /* Turn off 'trace' bits */
339 regs_set_return_msr(regs,
340 (regs->msr & ~MSR_SINGLESTEP) |
341 kcb->kprobe_saved_msr);
346 * We have reentered the kprobe_handler(), since another probe
347 * was hit while within the handler. We here save the original
348 * kprobes variables and just single step on the instruction of
349 * the new probe without calling any user handlers.
351 save_previous_kprobe(kcb);
352 set_current_kprobe(p, regs, kcb);
353 kprobes_inc_nmissed_count(p);
354 kcb->kprobe_status = KPROBE_REENTER;
355 if (p->ainsn.boostable >= 0) {
356 ret = try_to_emulate(p, regs);
359 restore_previous_kprobe(kcb);
360 preempt_enable_no_resched();
364 prepare_singlestep(p, regs);
368 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
369 set_current_kprobe(p, regs, kcb);
370 if (p->pre_handler && p->pre_handler(p, regs)) {
371 /* handler changed execution path, so skip ss setup */
372 reset_current_kprobe();
373 preempt_enable_no_resched();
377 if (p->ainsn.boostable >= 0) {
378 ret = try_to_emulate(p, regs);
382 p->post_handler(p, regs, 0);
384 kcb->kprobe_status = KPROBE_HIT_SSDONE;
385 reset_current_kprobe();
386 preempt_enable_no_resched();
390 prepare_singlestep(p, regs);
391 kcb->kprobe_status = KPROBE_HIT_SS;
395 preempt_enable_no_resched();
398 NOKPROBE_SYMBOL(kprobe_handler);
401 * Function return probe trampoline:
402 * - init_kprobes() establishes a probepoint here
403 * - When the probed function returns, this probe
404 * causes the handlers to fire
406 asm(".global kretprobe_trampoline\n"
407 ".type kretprobe_trampoline, @function\n"
408 "kretprobe_trampoline:\n"
411 ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
414 * Called when the probe at kretprobe trampoline is hit
416 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
418 unsigned long orig_ret_address;
420 orig_ret_address = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
422 * We get here through one of two paths:
423 * 1. by taking a trap -> kprobe_handler() -> here
424 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
426 * When going back through (1), we need regs->nip to be setup properly
427 * as it is used to determine the return address from the trap.
428 * For (2), since nip is not honoured with optprobes, we instead setup
429 * the link register properly so that the subsequent 'blr' in
430 * kretprobe_trampoline jumps back to the right instruction.
432 * For nip, we should set the address to the previous instruction since
433 * we end up emulating it in kprobe_handler(), which increments the nip
436 regs_set_return_ip(regs, orig_ret_address - 4);
437 regs->link = orig_ret_address;
441 NOKPROBE_SYMBOL(trampoline_probe_handler);
444 * Called after single-stepping. p->addr is the address of the
445 * instruction whose first byte has been replaced by the "breakpoint"
446 * instruction. To avoid the SMP problems that can occur when we
447 * temporarily put back the original opcode to single-step, we
448 * single-stepped a copy of the instruction. The address of this
449 * copy is p->ainsn.insn.
451 int kprobe_post_handler(struct pt_regs *regs)
454 struct kprobe *cur = kprobe_running();
455 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
457 if (!cur || user_mode(regs))
460 len = ppc_inst_len(ppc_inst_read(cur->ainsn.insn));
461 /* make sure we got here for instruction we have a kprobe on */
462 if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
465 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
466 kcb->kprobe_status = KPROBE_HIT_SSDONE;
467 cur->post_handler(cur, regs, 0);
470 /* Adjust nip to after the single-stepped instruction */
471 regs_set_return_ip(regs, (unsigned long)cur->addr + len);
472 regs_set_return_msr(regs, regs->msr | kcb->kprobe_saved_msr);
474 /*Restore back the original saved kprobes variables and continue. */
475 if (kcb->kprobe_status == KPROBE_REENTER) {
476 restore_previous_kprobe(kcb);
479 reset_current_kprobe();
481 preempt_enable_no_resched();
484 * if somebody else is singlestepping across a probe point, msr
485 * will have DE/SE set, in which case, continue the remaining processing
486 * of do_debug, as if this is not a probe hit.
488 if (regs->msr & MSR_SINGLESTEP)
493 NOKPROBE_SYMBOL(kprobe_post_handler);
495 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
497 struct kprobe *cur = kprobe_running();
498 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
499 const struct exception_table_entry *entry;
501 switch(kcb->kprobe_status) {
505 * We are here because the instruction being single
506 * stepped caused a page fault. We reset the current
507 * kprobe and the nip points back to the probe address
508 * and allow the page fault handler to continue as a
511 regs_set_return_ip(regs, (unsigned long)cur->addr);
512 /* Turn off 'trace' bits */
513 regs_set_return_msr(regs,
514 (regs->msr & ~MSR_SINGLESTEP) |
515 kcb->kprobe_saved_msr);
516 if (kcb->kprobe_status == KPROBE_REENTER)
517 restore_previous_kprobe(kcb);
519 reset_current_kprobe();
520 preempt_enable_no_resched();
522 case KPROBE_HIT_ACTIVE:
523 case KPROBE_HIT_SSDONE:
525 * In case the user-specified fault handler returned
526 * zero, try to fix up.
528 if ((entry = search_exception_tables(regs->nip)) != NULL) {
529 regs_set_return_ip(regs, extable_fixup(entry));
534 * fixup_exception() could not handle it,
535 * Let do_page_fault() fix it.
543 NOKPROBE_SYMBOL(kprobe_fault_handler);
545 unsigned long arch_deref_entry_point(void *entry)
547 #ifdef PPC64_ELF_ABI_v1
548 if (!kernel_text_address((unsigned long)entry))
549 return ppc_global_function_entry(entry);
552 return (unsigned long)entry;
554 NOKPROBE_SYMBOL(arch_deref_entry_point);
556 static struct kprobe trampoline_p = {
557 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
558 .pre_handler = trampoline_probe_handler
561 int __init arch_init_kprobes(void)
563 return register_kprobe(&trampoline_p);
566 int arch_trampoline_kprobe(struct kprobe *p)
568 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
573 NOKPROBE_SYMBOL(arch_trampoline_kprobe);