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 ftrace_regs *fregs)
18 {
19 	struct kprobe *p;
20 	struct kprobe_ctlblk *kcb;
21 	struct pt_regs *regs;
22 	int bit;
23 
24 	bit = ftrace_test_recursion_trylock(nip, parent_nip);
25 	if (bit < 0)
26 		return;
27 
28 	regs = ftrace_get_regs(fregs);
29 	p = get_kprobe((kprobe_opcode_t *)nip);
30 	if (unlikely(!p) || kprobe_disabled(p))
31 		goto out;
32 
33 	kcb = get_kprobe_ctlblk();
34 	if (kprobe_running()) {
35 		kprobes_inc_nmissed_count(p);
36 	} else {
37 		/*
38 		 * On powerpc, NIP is *before* this instruction for the
39 		 * pre handler
40 		 */
41 		regs_add_return_ip(regs, -MCOUNT_INSN_SIZE);
42 
43 		__this_cpu_write(current_kprobe, p);
44 		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
45 		if (!p->pre_handler || !p->pre_handler(p, regs)) {
46 			/*
47 			 * Emulate singlestep (and also recover regs->nip)
48 			 * as if there is a nop
49 			 */
50 			regs_add_return_ip(regs, MCOUNT_INSN_SIZE);
51 			if (unlikely(p->post_handler)) {
52 				kcb->kprobe_status = KPROBE_HIT_SSDONE;
53 				p->post_handler(p, regs, 0);
54 			}
55 		}
56 		/*
57 		 * If pre_handler returns !0, it changes regs->nip. We have to
58 		 * skip emulating post_handler.
59 		 */
60 		__this_cpu_write(current_kprobe, NULL);
61 	}
62 out:
63 	ftrace_test_recursion_unlock(bit);
64 }
65 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
66 
67 int arch_prepare_kprobe_ftrace(struct kprobe *p)
68 {
69 	p->ainsn.insn = NULL;
70 	p->ainsn.boostable = -1;
71 	return 0;
72 }
73