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 */
16 void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
17 			   struct ftrace_ops *ops, struct pt_regs *regs)
18 {
19 	struct kprobe *p;
20 	struct kprobe_ctlblk *kcb;
21 
22 	p = get_kprobe((kprobe_opcode_t *)nip);
23 	if (unlikely(!p) || kprobe_disabled(p))
24 		return;
25 
26 	kcb = get_kprobe_ctlblk();
27 	if (kprobe_running()) {
28 		kprobes_inc_nmissed_count(p);
29 	} else {
30 		/*
31 		 * On powerpc, NIP is *before* this instruction for the
32 		 * pre handler
33 		 */
34 		regs->nip -= MCOUNT_INSN_SIZE;
35 
36 		__this_cpu_write(current_kprobe, p);
37 		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
38 		if (!p->pre_handler || !p->pre_handler(p, regs)) {
39 			/*
40 			 * Emulate singlestep (and also recover regs->nip)
41 			 * as if there is a nop
42 			 */
43 			regs->nip += MCOUNT_INSN_SIZE;
44 			if (unlikely(p->post_handler)) {
45 				kcb->kprobe_status = KPROBE_HIT_SSDONE;
46 				p->post_handler(p, regs, 0);
47 			}
48 		}
49 		/*
50 		 * If pre_handler returns !0, it changes regs->nip. We have to
51 		 * skip emulating post_handler.
52 		 */
53 		__this_cpu_write(current_kprobe, NULL);
54 	}
55 }
56 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
57 
58 int arch_prepare_kprobe_ftrace(struct kprobe *p)
59 {
60 	p->ainsn.insn = NULL;
61 	p->ainsn.boostable = -1;
62 	return 0;
63 }
64