kprobes-ftrace.c

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * Dynamic Ftrace based Kprobes Optimization
 4 *
 5 * Copyright (C) Hitachi Ltd., 2012
 6 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
 7 *		  IBM Corporation
 8 */
 9#include <linux/kprobes.h>
10#include <linux/ptrace.h>
11#include <linux/hardirq.h>
12#include <linux/preempt.h>
13#include <linux/ftrace.h>
14
15/* Ftrace callback handler for kprobes */
16void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
17			   struct ftrace_ops *ops, struct ftrace_regs *fregs)
18{
19	struct kprobe *p;
20	struct kprobe_ctlblk *kcb;
21	struct pt_regs *regs;
22	int bit;
23
24	if (unlikely(kprobe_ftrace_disabled))
25		return;
26
27	bit = ftrace_test_recursion_trylock(nip, parent_nip);
28	if (bit < 0)
29		return;
30
31	regs = ftrace_get_regs(fregs);
32	p = get_kprobe((kprobe_opcode_t *)nip);
33	if (unlikely(!p) || kprobe_disabled(p))
34		goto out;
35
36	kcb = get_kprobe_ctlblk();
37	if (kprobe_running()) {
38		kprobes_inc_nmissed_count(p);
39	} else {
40		/*
41		 * On powerpc, NIP is *before* this instruction for the
42		 * pre handler
43		 */
44		regs_add_return_ip(regs, -MCOUNT_INSN_SIZE);
45
46		__this_cpu_write(current_kprobe, p);
47		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
48		if (!p->pre_handler || !p->pre_handler(p, regs)) {
49			/*
50			 * Emulate singlestep (and also recover regs->nip)
51			 * as if there is a nop
52			 */
53			regs_add_return_ip(regs, MCOUNT_INSN_SIZE);
54			if (unlikely(p->post_handler)) {
55				kcb->kprobe_status = KPROBE_HIT_SSDONE;
56				p->post_handler(p, regs, 0);
57			}
58		}
59		/*
60		 * If pre_handler returns !0, it changes regs->nip. We have to
61		 * skip emulating post_handler.
62		 */
63		__this_cpu_write(current_kprobe, NULL);
64	}
65out:
66	ftrace_test_recursion_unlock(bit);
67}
68NOKPROBE_SYMBOL(kprobe_ftrace_handler);
69
70int arch_prepare_kprobe_ftrace(struct kprobe *p)
71{
72	p->ainsn.insn = NULL;
73	p->ainsn.boostable = -1;
74	return 0;
75}