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 ftrace_regs * fregs)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 preempt_disable_notrace();
30 p = get_kprobe((kprobe_opcode_t *)nip);
31 if (unlikely(!p) || kprobe_disabled(p))
32 goto out;
33
34 kcb = get_kprobe_ctlblk();
35 if (kprobe_running()) {
36 kprobes_inc_nmissed_count(p);
37 } else {
38 /*
39 * On powerpc, NIP is *before* this instruction for the
40 * pre handler
41 */
42 regs->nip -= MCOUNT_INSN_SIZE;
43
44 __this_cpu_write(current_kprobe, p);
45 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
46 if (!p->pre_handler || !p->pre_handler(p, regs)) {
47 /*
48 * Emulate singlestep (and also recover regs->nip)
49 * as if there is a nop
50 */
51 regs->nip += MCOUNT_INSN_SIZE;
52 if (unlikely(p->post_handler)) {
53 kcb->kprobe_status = KPROBE_HIT_SSDONE;
54 p->post_handler(p, regs, 0);
55 }
56 }
57 /*
58 * If pre_handler returns !0, it changes regs->nip. We have to
59 * skip emulating post_handler.
60 */
61 __this_cpu_write(current_kprobe, NULL);
62 }
63 out:
64 preempt_enable_notrace();
65 ftrace_test_recursion_unlock(bit);
66 }
67 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
68
arch_prepare_kprobe_ftrace(struct kprobe * p)69 int arch_prepare_kprobe_ftrace(struct kprobe *p)
70 {
71 p->ainsn.insn = NULL;
72 p->ainsn.boostable = -1;
73 return 0;
74 }
75