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(addr: (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}
71

source code of linux/arch/x86/kernel/kprobes/ftrace.c