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 */
kprobe_ftrace_handler(unsigned long ip,unsigned long parent_ip,struct ftrace_ops * ops,struct ftrace_regs * fregs)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 bit = ftrace_test_recursion_trylock(ip, parent_ip);
25 if (bit < 0)
26 return;
27
28 preempt_disable_notrace();
29 p = get_kprobe((kprobe_opcode_t *)ip);
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 unsigned long orig_ip = regs->ip;
38 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
39 regs->ip = ip + sizeof(kprobe_opcode_t);
40
41 __this_cpu_write(current_kprobe, p);
42 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
43 if (!p->pre_handler || !p->pre_handler(p, regs)) {
44 /*
45 * Emulate singlestep (and also recover regs->ip)
46 * as if there is a 5byte nop
47 */
48 regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
49 if (unlikely(p->post_handler)) {
50 kcb->kprobe_status = KPROBE_HIT_SSDONE;
51 p->post_handler(p, regs, 0);
52 }
53 regs->ip = orig_ip;
54 }
55 /*
56 * If pre_handler returns !0, it changes regs->ip. We have to
57 * skip emulating post_handler.
58 */
59 __this_cpu_write(current_kprobe, NULL);
60 }
61 out:
62 preempt_enable_notrace();
63 ftrace_test_recursion_unlock(bit);
64 }
65 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
66
arch_prepare_kprobe_ftrace(struct kprobe * p)67 int arch_prepare_kprobe_ftrace(struct kprobe *p)
68 {
69 p->ainsn.insn = NULL;
70 p->ainsn.boostable = false;
71 return 0;
72 }
73