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 bit = ftrace_test_recursion_trylock(ip: nip, parent_ip: parent_nip);
25 if (bit < 0)
26 return;
27
28 regs = ftrace_get_regs(fregs);
29 p = get_kprobe(addr: (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 }
62out:
63 ftrace_test_recursion_unlock(bit);
64}
65NOKPROBE_SYMBOL(kprobe_ftrace_handler);
66
67int arch_prepare_kprobe_ftrace(struct kprobe *p)
68{
69 p->ainsn.insn = NULL;
70 p->ainsn.boostable = -1;
71 return 0;
72}
73

source code of linux/arch/powerpc/kernel/kprobes-ftrace.c