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 <linux/set_memory.h>
24 #include <asm/code-patching.h>
25 #include <asm/cacheflush.h>
26 #include <asm/sstep.h>
27 #include <asm/sections.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 CONFIG_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(CONFIG_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 static bool arch_kprobe_on_func_entry(unsigned long offset)
110 #ifdef CONFIG_PPC64_ELF_ABI_V2
111 #ifdef CONFIG_KPROBES_ON_FTRACE
121 /* XXX try and fold the magic of kprobe_lookup_name() in this */
122 kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
125 *on_func_entry = arch_kprobe_on_func_entry(offset);
126 return (kprobe_opcode_t *)(addr + offset);
129 void *alloc_insn_page(void)
133 page = module_alloc(PAGE_SIZE);
137 if (strict_module_rwx_enabled()) {
138 int err = set_memory_rox((unsigned long)page, 1);
145 module_memfree(page);
149 int arch_prepare_kprobe(struct kprobe *p)
153 ppc_inst_t insn = ppc_inst_read(p->addr);
155 if ((unsigned long)p->addr & 0x03) {
156 printk("Attempt to register kprobe at an unaligned address\n");
158 } else if (!can_single_step(ppc_inst_val(insn))) {
159 printk("Cannot register a kprobe on instructions that can't be single stepped\n");
161 } else if ((unsigned long)p->addr & ~PAGE_MASK &&
162 ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) {
163 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
166 prev = get_kprobe(p->addr - 1);
169 * When prev is a ftrace-based kprobe, we don't have an insn, and it
170 * doesn't probe for prefixed instruction.
172 if (prev && !kprobe_ftrace(prev) &&
173 ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
174 printk("Cannot register a kprobe on the second word of prefixed instruction\n");
178 /* insn must be on a special executable page on ppc64. This is
179 * not explicitly required on ppc32 (right now), but it doesn't hurt */
181 p->ainsn.insn = get_insn_slot();
187 patch_instruction(p->ainsn.insn, insn);
188 p->opcode = ppc_inst_val(insn);
191 p->ainsn.boostable = 0;
194 NOKPROBE_SYMBOL(arch_prepare_kprobe);
196 void arch_arm_kprobe(struct kprobe *p)
198 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(BREAKPOINT_INSTRUCTION)));
200 NOKPROBE_SYMBOL(arch_arm_kprobe);
202 void arch_disarm_kprobe(struct kprobe *p)
204 WARN_ON_ONCE(patch_instruction(p->addr, ppc_inst(p->opcode)));
206 NOKPROBE_SYMBOL(arch_disarm_kprobe);
208 void arch_remove_kprobe(struct kprobe *p)
211 free_insn_slot(p->ainsn.insn, 0);
212 p->ainsn.insn = NULL;
215 NOKPROBE_SYMBOL(arch_remove_kprobe);
217 static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
219 enable_single_step(regs);
222 * On powerpc we should single step on the original
223 * instruction even if the probed insn is a trap
224 * variant as values in regs could play a part in
225 * if the trap is taken or not
227 regs_set_return_ip(regs, (unsigned long)p->ainsn.insn);
230 static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
232 kcb->prev_kprobe.kp = kprobe_running();
233 kcb->prev_kprobe.status = kcb->kprobe_status;
234 kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
237 static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
239 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
240 kcb->kprobe_status = kcb->prev_kprobe.status;
241 kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
244 static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
245 struct kprobe_ctlblk *kcb)
247 __this_cpu_write(current_kprobe, p);
248 kcb->kprobe_saved_msr = regs->msr;
251 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
253 ri->ret_addr = (kprobe_opcode_t *)regs->link;
256 /* Replace the return addr with trampoline addr */
257 regs->link = (unsigned long)__kretprobe_trampoline;
259 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
261 static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
264 ppc_inst_t insn = ppc_inst_read(p->ainsn.insn);
266 /* regs->nip is also adjusted if emulate_step returns 1 */
267 ret = emulate_step(regs, insn);
270 * Once this instruction has been boosted
271 * successfully, set the boostable flag
273 if (unlikely(p->ainsn.boostable == 0))
274 p->ainsn.boostable = 1;
275 } else if (ret < 0) {
277 * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
278 * So, we should never get here... but, its still
279 * good to catch them, just in case...
281 printk("Can't step on instruction %08lx\n", ppc_inst_as_ulong(insn));
285 * If we haven't previously emulated this instruction, then it
286 * can't be boosted. Note it down so we don't try to do so again.
288 * If, however, we had emulated this instruction in the past,
289 * then this is just an error with the current run (for
290 * instance, exceptions due to a load/store). We return 0 so
291 * that this is now single-stepped, but continue to try
292 * emulating it in subsequent probe hits.
294 if (unlikely(p->ainsn.boostable != 1))
295 p->ainsn.boostable = -1;
300 NOKPROBE_SYMBOL(try_to_emulate);
302 int kprobe_handler(struct pt_regs *regs)
306 unsigned int *addr = (unsigned int *)regs->nip;
307 struct kprobe_ctlblk *kcb;
312 if (!IS_ENABLED(CONFIG_BOOKE) &&
313 (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)))
317 * We don't want to be preempted for the entire
318 * duration of kprobe processing
321 kcb = get_kprobe_ctlblk();
323 p = get_kprobe(addr);
327 if (get_kernel_nofault(instr, addr))
330 if (instr != BREAKPOINT_INSTRUCTION) {
332 * PowerPC has multiple variants of the "trap"
333 * instruction. If the current instruction is a
334 * trap variant, it could belong to someone else
339 * The breakpoint instruction was removed right
340 * after we hit it. Another cpu has removed
341 * either a probepoint or a debugger breakpoint
342 * at this address. In either case, no further
343 * handling of this interrupt is appropriate.
347 /* Not one of ours: let kernel handle it */
351 /* Check we're not actually recursing */
352 if (kprobe_running()) {
353 kprobe_opcode_t insn = *p->ainsn.insn;
354 if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) {
355 /* Turn off 'trace' bits */
356 regs_set_return_msr(regs,
357 (regs->msr & ~MSR_SINGLESTEP) |
358 kcb->kprobe_saved_msr);
363 * We have reentered the kprobe_handler(), since another probe
364 * was hit while within the handler. We here save the original
365 * kprobes variables and just single step on the instruction of
366 * the new probe without calling any user handlers.
368 save_previous_kprobe(kcb);
369 set_current_kprobe(p, regs, kcb);
370 kprobes_inc_nmissed_count(p);
371 kcb->kprobe_status = KPROBE_REENTER;
372 if (p->ainsn.boostable >= 0) {
373 ret = try_to_emulate(p, regs);
376 restore_previous_kprobe(kcb);
381 prepare_singlestep(p, regs);
385 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
386 set_current_kprobe(p, regs, kcb);
387 if (p->pre_handler && p->pre_handler(p, regs)) {
388 /* handler changed execution path, so skip ss setup */
389 reset_current_kprobe();
394 if (p->ainsn.boostable >= 0) {
395 ret = try_to_emulate(p, regs);
399 p->post_handler(p, regs, 0);
401 kcb->kprobe_status = KPROBE_HIT_SSDONE;
402 reset_current_kprobe();
407 prepare_singlestep(p, regs);
408 kcb->kprobe_status = KPROBE_HIT_SS;
415 NOKPROBE_SYMBOL(kprobe_handler);
418 * Function return probe trampoline:
419 * - init_kprobes() establishes a probepoint here
420 * - When the probed function returns, this probe
421 * causes the handlers to fire
423 asm(".global __kretprobe_trampoline\n"
424 ".type __kretprobe_trampoline, @function\n"
425 "__kretprobe_trampoline:\n"
428 ".size __kretprobe_trampoline, .-__kretprobe_trampoline\n");
431 * Called when the probe at kretprobe trampoline is hit
433 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
435 unsigned long orig_ret_address;
437 orig_ret_address = __kretprobe_trampoline_handler(regs, NULL);
439 * We get here through one of two paths:
440 * 1. by taking a trap -> kprobe_handler() -> here
441 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
443 * When going back through (1), we need regs->nip to be setup properly
444 * as it is used to determine the return address from the trap.
445 * For (2), since nip is not honoured with optprobes, we instead setup
446 * the link register properly so that the subsequent 'blr' in
447 * __kretprobe_trampoline jumps back to the right instruction.
449 * For nip, we should set the address to the previous instruction since
450 * we end up emulating it in kprobe_handler(), which increments the nip
453 regs_set_return_ip(regs, orig_ret_address - 4);
454 regs->link = orig_ret_address;
458 NOKPROBE_SYMBOL(trampoline_probe_handler);
461 * Called after single-stepping. p->addr is the address of the
462 * instruction whose first byte has been replaced by the "breakpoint"
463 * instruction. To avoid the SMP problems that can occur when we
464 * temporarily put back the original opcode to single-step, we
465 * single-stepped a copy of the instruction. The address of this
466 * copy is p->ainsn.insn.
468 int kprobe_post_handler(struct pt_regs *regs)
471 struct kprobe *cur = kprobe_running();
472 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
474 if (!cur || user_mode(regs))
477 len = ppc_inst_len(ppc_inst_read(cur->ainsn.insn));
478 /* make sure we got here for instruction we have a kprobe on */
479 if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
482 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
483 kcb->kprobe_status = KPROBE_HIT_SSDONE;
484 cur->post_handler(cur, regs, 0);
487 /* Adjust nip to after the single-stepped instruction */
488 regs_set_return_ip(regs, (unsigned long)cur->addr + len);
489 regs_set_return_msr(regs, regs->msr | kcb->kprobe_saved_msr);
491 /*Restore back the original saved kprobes variables and continue. */
492 if (kcb->kprobe_status == KPROBE_REENTER) {
493 restore_previous_kprobe(kcb);
496 reset_current_kprobe();
501 * if somebody else is singlestepping across a probe point, msr
502 * will have DE/SE set, in which case, continue the remaining processing
503 * of do_debug, as if this is not a probe hit.
505 if (regs->msr & MSR_SINGLESTEP)
510 NOKPROBE_SYMBOL(kprobe_post_handler);
512 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
514 struct kprobe *cur = kprobe_running();
515 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
516 const struct exception_table_entry *entry;
518 switch(kcb->kprobe_status) {
522 * We are here because the instruction being single
523 * stepped caused a page fault. We reset the current
524 * kprobe and the nip points back to the probe address
525 * and allow the page fault handler to continue as a
528 regs_set_return_ip(regs, (unsigned long)cur->addr);
529 /* Turn off 'trace' bits */
530 regs_set_return_msr(regs,
531 (regs->msr & ~MSR_SINGLESTEP) |
532 kcb->kprobe_saved_msr);
533 if (kcb->kprobe_status == KPROBE_REENTER)
534 restore_previous_kprobe(kcb);
536 reset_current_kprobe();
539 case KPROBE_HIT_ACTIVE:
540 case KPROBE_HIT_SSDONE:
542 * In case the user-specified fault handler returned
543 * zero, try to fix up.
545 if ((entry = search_exception_tables(regs->nip)) != NULL) {
546 regs_set_return_ip(regs, extable_fixup(entry));
551 * fixup_exception() could not handle it,
552 * Let do_page_fault() fix it.
560 NOKPROBE_SYMBOL(kprobe_fault_handler);
562 static struct kprobe trampoline_p = {
563 .addr = (kprobe_opcode_t *) &__kretprobe_trampoline,
564 .pre_handler = trampoline_probe_handler
567 int __init arch_init_kprobes(void)
569 return register_kprobe(&trampoline_p);
572 int arch_trampoline_kprobe(struct kprobe *p)
574 if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
579 NOKPROBE_SYMBOL(arch_trampoline_kprobe);