1// SPDX-License-Identifier: GPL-2.0
 2
 3#include <linux/kprobes.h>
 4
 5/* Ftrace callback handler for kprobes -- called under preepmt disabled */
 6void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 7			   struct ftrace_ops *ops, struct ftrace_regs *fregs)
 8{
 9	int bit;
10	bool lr_saver = false;
11	struct kprobe *p;
12	struct kprobe_ctlblk *kcb;
13	struct pt_regs *regs;
14
15	bit = ftrace_test_recursion_trylock(ip, parent_ip);
16	if (bit < 0)
17		return;
18
19	regs = ftrace_get_regs(fregs);
20	p = get_kprobe((kprobe_opcode_t *)ip);
21	if (!p) {
22		p = get_kprobe((kprobe_opcode_t *)(ip - MCOUNT_INSN_SIZE));
23		if (unlikely(!p) || kprobe_disabled(p))
24			goto out;
25		lr_saver = true;
26	}
27
28	kcb = get_kprobe_ctlblk();
29	if (kprobe_running()) {
30		kprobes_inc_nmissed_count(p);
31	} else {
32		unsigned long orig_ip = instruction_pointer(regs);
33
34		if (lr_saver)
35			ip -= MCOUNT_INSN_SIZE;
36		instruction_pointer_set(regs, ip);
37		__this_cpu_write(current_kprobe, p);
38		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
39		if (!p->pre_handler || !p->pre_handler(p, regs)) {
40			/*
41			 * Emulate singlestep (and also recover regs->pc)
42			 * as if there is a nop
43			 */
44			instruction_pointer_set(regs,
45				(unsigned long)p->addr + MCOUNT_INSN_SIZE);
46			if (unlikely(p->post_handler)) {
47				kcb->kprobe_status = KPROBE_HIT_SSDONE;
48				p->post_handler(p, regs, 0);
49			}
50			instruction_pointer_set(regs, orig_ip);
51		}
52		/*
53		 * If pre_handler returns !0, it changes regs->pc. We have to
54		 * skip emulating post_handler.
55		 */
56		__this_cpu_write(current_kprobe, NULL);
57	}
58out:
59	ftrace_test_recursion_unlock(bit);
60}
61NOKPROBE_SYMBOL(kprobe_ftrace_handler);
62
63int arch_prepare_kprobe_ftrace(struct kprobe *p)
64{
65	p->ainsn.api.insn = NULL;
66	return 0;
67}