2 * arch/arm64/kernel/probes/kprobes.c
4 * Kprobes support for ARM64
6 * Copyright (C) 2013 Linaro Limited.
7 * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
19 #include <linux/kasan.h>
20 #include <linux/kernel.h>
21 #include <linux/kprobes.h>
22 #include <linux/extable.h>
23 #include <linux/slab.h>
24 #include <linux/stop_machine.h>
25 #include <linux/sched/debug.h>
26 #include <linux/stringify.h>
27 #include <asm/traps.h>
28 #include <asm/ptrace.h>
29 #include <asm/cacheflush.h>
30 #include <asm/debug-monitors.h>
31 #include <asm/system_misc.h>
33 #include <linux/uaccess.h>
35 #include <asm/sections.h>
37 #include "decode-insn.h"
39 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
40 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
43 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
45 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
47 /* prepare insn slot */
48 p->ainsn.api.insn[0] = cpu_to_le32(p->opcode);
50 flush_icache_range((uintptr_t) (p->ainsn.api.insn),
51 (uintptr_t) (p->ainsn.api.insn) +
52 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
55 * Needs restoring of return address after stepping xol.
57 p->ainsn.api.restore = (unsigned long) p->addr +
58 sizeof(kprobe_opcode_t);
61 static void __kprobes arch_prepare_simulate(struct kprobe *p)
63 /* This instructions is not executed xol. No need to adjust the PC */
64 p->ainsn.api.restore = 0;
67 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
69 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
71 if (p->ainsn.api.handler)
72 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs);
74 /* single step simulated, now go for post processing */
75 post_kprobe_handler(kcb, regs);
78 int __kprobes arch_prepare_kprobe(struct kprobe *p)
80 unsigned long probe_addr = (unsigned long)p->addr;
81 extern char __start_rodata[];
82 extern char __end_rodata[];
87 /* copy instruction */
88 p->opcode = le32_to_cpu(*p->addr);
90 if (in_exception_text(probe_addr))
92 if (probe_addr >= (unsigned long) __start_rodata &&
93 probe_addr <= (unsigned long) __end_rodata)
96 /* decode instruction */
97 switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
98 case INSN_REJECTED: /* insn not supported */
101 case INSN_GOOD_NO_SLOT: /* insn need simulation */
102 p->ainsn.api.insn = NULL;
105 case INSN_GOOD: /* instruction uses slot */
106 p->ainsn.api.insn = get_insn_slot();
107 if (!p->ainsn.api.insn)
112 /* prepare the instruction */
113 if (p->ainsn.api.insn)
114 arch_prepare_ss_slot(p);
116 arch_prepare_simulate(p);
121 static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
126 addrs[0] = (void *)addr;
127 insns[0] = (u32)opcode;
129 return aarch64_insn_patch_text(addrs, insns, 1);
132 /* arm kprobe: install breakpoint in text */
133 void __kprobes arch_arm_kprobe(struct kprobe *p)
135 patch_text(p->addr, BRK64_OPCODE_KPROBES);
138 /* disarm kprobe: remove breakpoint from text */
139 void __kprobes arch_disarm_kprobe(struct kprobe *p)
141 patch_text(p->addr, p->opcode);
144 void __kprobes arch_remove_kprobe(struct kprobe *p)
146 if (p->ainsn.api.insn) {
147 free_insn_slot(p->ainsn.api.insn, 0);
148 p->ainsn.api.insn = NULL;
152 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
154 kcb->prev_kprobe.kp = kprobe_running();
155 kcb->prev_kprobe.status = kcb->kprobe_status;
158 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
160 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
161 kcb->kprobe_status = kcb->prev_kprobe.status;
164 static void __kprobes set_current_kprobe(struct kprobe *p)
166 __this_cpu_write(current_kprobe, p);
170 * When PSTATE.D is set (masked), then software step exceptions can not be
172 * SPSR's D bit shows the value of PSTATE.D immediately before the
173 * exception was taken. PSTATE.D is set while entering into any exception
174 * mode, however software clears it for any normal (none-debug-exception)
175 * mode in the exception entry. Therefore, when we are entering into kprobe
176 * breakpoint handler from any normal mode then SPSR.D bit is already
177 * cleared, however it is set when we are entering from any debug exception
179 * Since we always need to generate single step exception after a kprobe
180 * breakpoint exception therefore we need to clear it unconditionally, when
181 * we become sure that the current breakpoint exception is for kprobe.
183 static void __kprobes
184 spsr_set_debug_flag(struct pt_regs *regs, int mask)
186 unsigned long spsr = regs->pstate;
197 * Interrupts need to be disabled before single-step mode is set, and not
198 * reenabled until after single-step mode ends.
199 * Without disabling interrupt on local CPU, there is a chance of
200 * interrupt occurrence in the period of exception return and start of
201 * out-of-line single-step, that result in wrongly single stepping
202 * into the interrupt handler.
204 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
205 struct pt_regs *regs)
207 kcb->saved_irqflag = regs->pstate;
208 regs->pstate |= PSR_I_BIT;
211 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
212 struct pt_regs *regs)
214 if (kcb->saved_irqflag & PSR_I_BIT)
215 regs->pstate |= PSR_I_BIT;
217 regs->pstate &= ~PSR_I_BIT;
220 static void __kprobes
221 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr)
223 kcb->ss_ctx.ss_pending = true;
224 kcb->ss_ctx.match_addr = addr + sizeof(kprobe_opcode_t);
227 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
229 kcb->ss_ctx.ss_pending = false;
230 kcb->ss_ctx.match_addr = 0;
233 static void __kprobes setup_singlestep(struct kprobe *p,
234 struct pt_regs *regs,
235 struct kprobe_ctlblk *kcb, int reenter)
240 save_previous_kprobe(kcb);
241 set_current_kprobe(p);
242 kcb->kprobe_status = KPROBE_REENTER;
244 kcb->kprobe_status = KPROBE_HIT_SS;
248 if (p->ainsn.api.insn) {
249 /* prepare for single stepping */
250 slot = (unsigned long)p->ainsn.api.insn;
252 set_ss_context(kcb, slot); /* mark pending ss */
254 spsr_set_debug_flag(regs, 0);
256 /* IRQs and single stepping do not mix well. */
257 kprobes_save_local_irqflag(kcb, regs);
258 kernel_enable_single_step(regs);
259 instruction_pointer_set(regs, slot);
261 /* insn simulation */
262 arch_simulate_insn(p, regs);
266 static int __kprobes reenter_kprobe(struct kprobe *p,
267 struct pt_regs *regs,
268 struct kprobe_ctlblk *kcb)
270 switch (kcb->kprobe_status) {
271 case KPROBE_HIT_SSDONE:
272 case KPROBE_HIT_ACTIVE:
273 kprobes_inc_nmissed_count(p);
274 setup_singlestep(p, regs, kcb, 1);
278 pr_warn("Unrecoverable kprobe detected at %p.\n", p->addr);
290 static void __kprobes
291 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
293 struct kprobe *cur = kprobe_running();
298 /* return addr restore if non-branching insn */
299 if (cur->ainsn.api.restore != 0)
300 instruction_pointer_set(regs, cur->ainsn.api.restore);
302 /* restore back original saved kprobe variables and continue */
303 if (kcb->kprobe_status == KPROBE_REENTER) {
304 restore_previous_kprobe(kcb);
307 /* call post handler */
308 kcb->kprobe_status = KPROBE_HIT_SSDONE;
309 if (cur->post_handler) {
310 /* post_handler can hit breakpoint and single step
311 * again, so we enable D-flag for recursive exception.
313 cur->post_handler(cur, regs, 0);
316 reset_current_kprobe();
319 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
321 struct kprobe *cur = kprobe_running();
322 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
324 switch (kcb->kprobe_status) {
328 * We are here because the instruction being single
329 * stepped caused a page fault. We reset the current
330 * kprobe and the ip points back to the probe address
331 * and allow the page fault handler to continue as a
334 instruction_pointer_set(regs, (unsigned long) cur->addr);
335 if (!instruction_pointer(regs))
338 kernel_disable_single_step();
340 if (kcb->kprobe_status == KPROBE_REENTER)
341 restore_previous_kprobe(kcb);
343 reset_current_kprobe();
346 case KPROBE_HIT_ACTIVE:
347 case KPROBE_HIT_SSDONE:
349 * We increment the nmissed count for accounting,
350 * we can also use npre/npostfault count for accounting
351 * these specific fault cases.
353 kprobes_inc_nmissed_count(cur);
356 * We come here because instructions in the pre/post
357 * handler caused the page_fault, this could happen
358 * if handler tries to access user space by
359 * copy_from_user(), get_user() etc. Let the
360 * user-specified handler try to fix it first.
362 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
366 * In case the user-specified fault handler returned
367 * zero, try to fix up.
369 if (fixup_exception(regs))
375 static void __kprobes kprobe_handler(struct pt_regs *regs)
377 struct kprobe *p, *cur_kprobe;
378 struct kprobe_ctlblk *kcb;
379 unsigned long addr = instruction_pointer(regs);
381 kcb = get_kprobe_ctlblk();
382 cur_kprobe = kprobe_running();
384 p = get_kprobe((kprobe_opcode_t *) addr);
388 if (reenter_kprobe(p, regs, kcb))
392 set_current_kprobe(p);
393 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
396 * If we have no pre-handler or it returned 0, we
397 * continue with normal processing. If we have a
398 * pre-handler and it returned non-zero, it prepped
399 * for calling the break_handler below on re-entry,
400 * so get out doing nothing more here.
402 * pre_handler can hit a breakpoint and can step thru
403 * before return, keep PSTATE D-flag enabled until
404 * pre_handler return back.
406 if (!p->pre_handler || !p->pre_handler(p, regs)) {
407 setup_singlestep(p, regs, kcb, 0);
411 } else if ((le32_to_cpu(*(kprobe_opcode_t *) addr) ==
412 BRK64_OPCODE_KPROBES) && cur_kprobe) {
413 /* We probably hit a jprobe. Call its break handler. */
414 if (cur_kprobe->break_handler &&
415 cur_kprobe->break_handler(cur_kprobe, regs)) {
416 setup_singlestep(cur_kprobe, regs, kcb, 0);
421 * The breakpoint instruction was removed right
422 * after we hit it. Another cpu has removed
423 * either a probepoint or a debugger breakpoint
424 * at this address. In either case, no further
425 * handling of this interrupt is appropriate.
426 * Return back to original instruction, and continue.
431 kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
433 if ((kcb->ss_ctx.ss_pending)
434 && (kcb->ss_ctx.match_addr == addr)) {
435 clear_ss_context(kcb); /* clear pending ss */
436 return DBG_HOOK_HANDLED;
438 /* not ours, kprobes should ignore it */
439 return DBG_HOOK_ERROR;
443 kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
445 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
448 /* return error if this is not our step */
449 retval = kprobe_ss_hit(kcb, instruction_pointer(regs));
451 if (retval == DBG_HOOK_HANDLED) {
452 kprobes_restore_local_irqflag(kcb, regs);
453 kernel_disable_single_step();
455 post_kprobe_handler(kcb, regs);
462 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
464 kprobe_handler(regs);
465 return DBG_HOOK_HANDLED;
468 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
470 struct jprobe *jp = container_of(p, struct jprobe, kp);
471 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
473 kcb->jprobe_saved_regs = *regs;
475 * Since we can't be sure where in the stack frame "stacked"
476 * pass-by-value arguments are stored we just don't try to
477 * duplicate any of the stack. Do not use jprobes on functions that
478 * use more than 64 bytes (after padding each to an 8 byte boundary)
479 * of arguments, or pass individual arguments larger than 16 bytes.
482 instruction_pointer_set(regs, (unsigned long) jp->entry);
484 pause_graph_tracing();
488 void __kprobes jprobe_return(void)
490 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
493 * Jprobe handler return by entering break exception,
494 * encoded same as kprobe, but with following conditions
495 * -a special PC to identify it from the other kprobes.
496 * -restore stack addr to original saved pt_regs
498 asm volatile(" mov sp, %0 \n"
499 "jprobe_return_break: brk %1 \n"
501 : "r" (kcb->jprobe_saved_regs.sp),
502 "I" (BRK64_ESR_KPROBES)
508 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
510 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
511 long stack_addr = kcb->jprobe_saved_regs.sp;
512 long orig_sp = kernel_stack_pointer(regs);
513 struct jprobe *jp = container_of(p, struct jprobe, kp);
514 extern const char jprobe_return_break[];
516 if (instruction_pointer(regs) != (u64) jprobe_return_break)
519 if (orig_sp != stack_addr) {
520 struct pt_regs *saved_regs =
521 (struct pt_regs *)kcb->jprobe_saved_regs.sp;
522 pr_err("current sp %lx does not match saved sp %lx\n",
523 orig_sp, stack_addr);
524 pr_err("Saved registers for jprobe %p\n", jp);
525 show_regs(saved_regs);
526 pr_err("Current registers\n");
530 unpause_graph_tracing();
531 *regs = kcb->jprobe_saved_regs;
532 preempt_enable_no_resched();
536 bool arch_within_kprobe_blacklist(unsigned long addr)
538 if ((addr >= (unsigned long)__kprobes_text_start &&
539 addr < (unsigned long)__kprobes_text_end) ||
540 (addr >= (unsigned long)__entry_text_start &&
541 addr < (unsigned long)__entry_text_end) ||
542 (addr >= (unsigned long)__idmap_text_start &&
543 addr < (unsigned long)__idmap_text_end) ||
544 !!search_exception_tables(addr))
547 if (!is_kernel_in_hyp_mode()) {
548 if ((addr >= (unsigned long)__hyp_text_start &&
549 addr < (unsigned long)__hyp_text_end) ||
550 (addr >= (unsigned long)__hyp_idmap_text_start &&
551 addr < (unsigned long)__hyp_idmap_text_end))
558 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
560 struct kretprobe_instance *ri = NULL;
561 struct hlist_head *head, empty_rp;
562 struct hlist_node *tmp;
563 unsigned long flags, orig_ret_address = 0;
564 unsigned long trampoline_address =
565 (unsigned long)&kretprobe_trampoline;
566 kprobe_opcode_t *correct_ret_addr = NULL;
568 INIT_HLIST_HEAD(&empty_rp);
569 kretprobe_hash_lock(current, &head, &flags);
572 * It is possible to have multiple instances associated with a given
573 * task either because multiple functions in the call path have
574 * return probes installed on them, and/or more than one
575 * return probe was registered for a target function.
577 * We can handle this because:
578 * - instances are always pushed into the head of the list
579 * - when multiple return probes are registered for the same
580 * function, the (chronologically) first instance's ret_addr
581 * will be the real return address, and all the rest will
582 * point to kretprobe_trampoline.
584 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
585 if (ri->task != current)
586 /* another task is sharing our hash bucket */
589 orig_ret_address = (unsigned long)ri->ret_addr;
591 if (orig_ret_address != trampoline_address)
593 * This is the real return address. Any other
594 * instances associated with this task are for
595 * other calls deeper on the call stack
600 kretprobe_assert(ri, orig_ret_address, trampoline_address);
602 correct_ret_addr = ri->ret_addr;
603 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
604 if (ri->task != current)
605 /* another task is sharing our hash bucket */
608 orig_ret_address = (unsigned long)ri->ret_addr;
609 if (ri->rp && ri->rp->handler) {
610 __this_cpu_write(current_kprobe, &ri->rp->kp);
611 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
612 ri->ret_addr = correct_ret_addr;
613 ri->rp->handler(ri, regs);
614 __this_cpu_write(current_kprobe, NULL);
617 recycle_rp_inst(ri, &empty_rp);
619 if (orig_ret_address != trampoline_address)
621 * This is the real return address. Any other
622 * instances associated with this task are for
623 * other calls deeper on the call stack
628 kretprobe_hash_unlock(current, &flags);
630 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
631 hlist_del(&ri->hlist);
634 return (void *)orig_ret_address;
637 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
638 struct pt_regs *regs)
640 ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
642 /* replace return addr (x30) with trampoline */
643 regs->regs[30] = (long)&kretprobe_trampoline;
646 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
651 int __init arch_init_kprobes(void)