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 if (unlikely(kprobe_ftrace_disabled))
25 return;
26
27 bit = ftrace_test_recursion_trylock(nip, parent_nip);
28 if (bit < 0)
29 return;
30
31 regs = ftrace_get_regs(fregs);
32 p = get_kprobe((kprobe_opcode_t *)nip);
33 if (unlikely(!p) || kprobe_disabled(p))
34 goto out;
35
36 kcb = get_kprobe_ctlblk();
37 if (kprobe_running()) {
38 kprobes_inc_nmissed_count(p);
39 } else {
40 /*
41 * On powerpc, NIP is *before* this instruction for the
42 * pre handler
43 */
44 regs_add_return_ip(regs, -MCOUNT_INSN_SIZE);
45
46 __this_cpu_write(current_kprobe, p);
47 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
48 if (!p->pre_handler || !p->pre_handler(p, regs)) {
49 /*
50 * Emulate singlestep (and also recover regs->nip)
51 * as if there is a nop
52 */
53 regs_add_return_ip(regs, MCOUNT_INSN_SIZE);
54 if (unlikely(p->post_handler)) {
55 kcb->kprobe_status = KPROBE_HIT_SSDONE;
56 p->post_handler(p, regs, 0);
57 }
58 }
59 /*
60 * If pre_handler returns !0, it changes regs->nip. We have to
61 * skip emulating post_handler.
62 */
63 __this_cpu_write(current_kprobe, NULL);
64 }
65 out:
66 ftrace_test_recursion_unlock(bit);
67 }
68 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
69
70 int arch_prepare_kprobe_ftrace(struct kprobe *p)
71 {
72 p->ainsn.insn = NULL;
73 p->ainsn.boostable = -1;
74 return 0;
75 }
76
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