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 preepmt disabed */
16void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
17			   struct ftrace_ops *ops, struct pt_regs *regs)
18{
19	struct kprobe *p;
20	struct kprobe_ctlblk *kcb;
21
22	/* Preempt is disabled by ftrace */
23	p = get_kprobe((kprobe_opcode_t *)ip);
24	if (unlikely(!p) || kprobe_disabled(p))
25		return;
26
27	kcb = get_kprobe_ctlblk();
28	if (kprobe_running()) {
29		kprobes_inc_nmissed_count(p);
30	} else {
31		unsigned long orig_ip = regs->ip;
32		/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
33		regs->ip = ip + sizeof(kprobe_opcode_t);
34
35		__this_cpu_write(current_kprobe, p);
36		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
37		if (!p->pre_handler || !p->pre_handler(p, regs)) {
38			/*
39			 * Emulate singlestep (and also recover regs->ip)
40			 * as if there is a 5byte nop
41			 */
42			regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
43			if (unlikely(p->post_handler)) {
44				kcb->kprobe_status = KPROBE_HIT_SSDONE;
45				p->post_handler(p, regs, 0);
46			}
47			regs->ip = orig_ip;
48		}
49		/*
50		 * If pre_handler returns !0, it changes regs->ip. We have to
51		 * skip emulating post_handler.
52		 */
53		__this_cpu_write(current_kprobe, NULL);
54	}
55}
56NOKPROBE_SYMBOL(kprobe_ftrace_handler);
57
58int arch_prepare_kprobe_ftrace(struct kprobe *p)
59{
60	p->ainsn.insn = NULL;
61	p->ainsn.boostable = false;
62	return 0;
63}