1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * Dynamic Ftrace based Kprobes Optimization
 4 *
 5 * Copyright (C) Hitachi Ltd., 2012
 6 */
 7#include <linux/kprobes.h>
 8#include <linux/ptrace.h>
 9#include <linux/hardirq.h>
10#include <linux/preempt.h>
11#include <linux/ftrace.h>
12
13#include "common.h"
14
15/* Ftrace callback handler for kprobes -- called under preempt disabled */
16void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
17			   struct ftrace_ops *ops, struct ftrace_regs *fregs)
18{
19	struct pt_regs *regs = ftrace_get_regs(fregs);
20	struct kprobe *p;
21	struct kprobe_ctlblk *kcb;
22	int bit;
23
24	bit = ftrace_test_recursion_trylock(ip, parent_ip);
25	if (bit < 0)
26		return;
27
28	p = get_kprobe((kprobe_opcode_t *)ip);
29	if (unlikely(!p) || kprobe_disabled(p))
30		goto out;
31
32	kcb = get_kprobe_ctlblk();
33	if (kprobe_running()) {
34		kprobes_inc_nmissed_count(p);
35	} else {
36		unsigned long orig_ip = regs->ip;
37		/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
38		regs->ip = ip + sizeof(kprobe_opcode_t);
39
40		__this_cpu_write(current_kprobe, p);
41		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
42		if (!p->pre_handler || !p->pre_handler(p, regs)) {
43			/*
44			 * Emulate singlestep (and also recover regs->ip)
45			 * as if there is a 5byte nop
46			 */
47			regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
48			if (unlikely(p->post_handler)) {
49				kcb->kprobe_status = KPROBE_HIT_SSDONE;
50				p->post_handler(p, regs, 0);
51			}
52			regs->ip = orig_ip;
53		}
54		/*
55		 * If pre_handler returns !0, it changes regs->ip. We have to
56		 * skip emulating post_handler.
57		 */
58		__this_cpu_write(current_kprobe, NULL);
59	}
60out:
61	ftrace_test_recursion_unlock(bit);
62}
63NOKPROBE_SYMBOL(kprobe_ftrace_handler);
64
65int arch_prepare_kprobe_ftrace(struct kprobe *p)
66{
67	p->ainsn.insn = NULL;
68	p->ainsn.boostable = false;
69	return 0;
70}