1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Dynamic Ftrace based Kprobes Optimization
4 *
5 * Copyright (C) Hitachi Ltd., 2012
6 */
7 #include <linux/kprobes.h>
8 #include <linux/ptrace.h>
9 #include <linux/hardirq.h>
10 #include <linux/preempt.h>
11 #include <linux/ftrace.h>
12
13 #include "common.h"
14
15 /* Ftrace callback handler for kprobes -- called under preempt disabled */
16 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
17 struct ftrace_ops *ops, struct ftrace_regs *fregs)
18 {
19 struct pt_regs *regs = ftrace_get_regs(fregs);
20 struct kprobe *p;
21 struct kprobe_ctlblk *kcb;
22 int bit;
23
24 if (unlikely(kprobe_ftrace_disabled))
25 return;
26
27 bit = ftrace_test_recursion_trylock(ip, parent_ip);
28 if (bit < 0)
29 return;
30
31 p = get_kprobe((kprobe_opcode_t *)ip);
32 if (unlikely(!p) || kprobe_disabled(p))
33 goto out;
34
35 kcb = get_kprobe_ctlblk();
36 if (kprobe_running()) {
37 kprobes_inc_nmissed_count(p);
38 } else {
39 unsigned long orig_ip = regs->ip;
40 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
41 regs->ip = ip + sizeof(kprobe_opcode_t);
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->ip)
48 * as if there is a 5byte nop
49 */
50 regs->ip = (unsigned long)p->addr + 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 regs->ip = orig_ip;
56 }
57 /*
58 * If pre_handler returns !0, it changes regs->ip. We have to
59 * skip emulating post_handler.
60 */
61 __this_cpu_write(current_kprobe, NULL);
62 }
63 out:
64 ftrace_test_recursion_unlock(bit);
65 }
66 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
67
68 int arch_prepare_kprobe_ftrace(struct kprobe *p)
69 {
70 p->ainsn.insn = NULL;
71 p->ainsn.boostable = false;
72 return 0;
73 }
74
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