1/*
2 * Dynamic Ftrace based Kprobes Optimization
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) Hitachi Ltd., 2012
19 */
20#include <linux/kprobes.h>
21#include <linux/ptrace.h>
22#include <linux/hardirq.h>
23#include <linux/preempt.h>
24#include <linux/ftrace.h>
25
26#include "common.h"
27
28static nokprobe_inline
29int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
30		      struct kprobe_ctlblk *kcb)
31{
32	/*
33	 * Emulate singlestep (and also recover regs->ip)
34	 * as if there is a 5byte nop
35	 */
36	regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
37	if (unlikely(p->post_handler)) {
38		kcb->kprobe_status = KPROBE_HIT_SSDONE;
39		p->post_handler(p, regs, 0);
40	}
41	__this_cpu_write(current_kprobe, NULL);
42	return 1;
43}
44
45int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
46		    struct kprobe_ctlblk *kcb)
47{
48	if (kprobe_ftrace(p))
49		return __skip_singlestep(p, regs, kcb);
50	else
51		return 0;
52}
53NOKPROBE_SYMBOL(skip_singlestep);
54
55/* Ftrace callback handler for kprobes */
56void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
57			   struct ftrace_ops *ops, struct pt_regs *regs)
58{
59	struct kprobe *p;
60	struct kprobe_ctlblk *kcb;
61	unsigned long flags;
62
63	/* Disable irq for emulating a breakpoint and avoiding preempt */
64	local_irq_save(flags);
65
66	p = get_kprobe((kprobe_opcode_t *)ip);
67	if (unlikely(!p) || kprobe_disabled(p))
68		goto end;
69
70	kcb = get_kprobe_ctlblk();
71	if (kprobe_running()) {
72		kprobes_inc_nmissed_count(p);
73	} else {
74		/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
75		regs->ip = ip + sizeof(kprobe_opcode_t);
76
77		__this_cpu_write(current_kprobe, p);
78		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
79		if (!p->pre_handler || !p->pre_handler(p, regs))
80			__skip_singlestep(p, regs, kcb);
81		/*
82		 * If pre_handler returns !0, it sets regs->ip and
83		 * resets current kprobe.
84		 */
85	}
86end:
87	local_irq_restore(flags);
88}
89NOKPROBE_SYMBOL(kprobe_ftrace_handler);
90
91int arch_prepare_kprobe_ftrace(struct kprobe *p)
92{
93	p->ainsn.insn = NULL;
94	p->ainsn.boostable = -1;
95	return 0;
96}
97