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 */
kprobe_ftrace_handler(unsigned long nip,unsigned long parent_nip,struct ftrace_ops * ops,struct pt_regs * regs)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
arch_prepare_kprobe_ftrace(struct kprobe * p)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