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 #include <asm/text-patching.h>
13
14 #include "common.h"
15
16 /* 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)17 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
18 struct ftrace_ops *ops, struct ftrace_regs *fregs)
19 {
20 struct pt_regs *regs = ftrace_get_regs(fregs);
21 struct kprobe *p;
22 struct kprobe_ctlblk *kcb;
23 int bit;
24
25 if (unlikely(kprobe_ftrace_disabled))
26 return;
27
28 bit = ftrace_test_recursion_trylock(ip, parent_ip);
29 if (bit < 0)
30 return;
31
32 p = get_kprobe((kprobe_opcode_t *)ip);
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 unsigned long orig_ip = instruction_pointer(regs);
41
42 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
43 instruction_pointer_set(regs, ip + INT3_INSN_SIZE);
44
45 __this_cpu_write(current_kprobe, p);
46 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
47 if (!p->pre_handler || !p->pre_handler(p, regs)) {
48 if (unlikely(p->post_handler)) {
49 /*
50 * Emulate singlestep (and also recover regs->ip)
51 * as if there is a 5byte nop
52 */
53 instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
54 kcb->kprobe_status = KPROBE_HIT_SSDONE;
55 p->post_handler(p, regs, 0);
56 }
57 /* Recover IP address */
58 instruction_pointer_set(regs, orig_ip);
59 }
60 /*
61 * If pre_handler returns !0, it changes regs->ip. We have to
62 * skip emulating post_handler.
63 */
64 __this_cpu_write(current_kprobe, NULL);
65 }
66 out:
67 ftrace_test_recursion_unlock(bit);
68 }
69 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
70
arch_prepare_kprobe_ftrace(struct kprobe * p)71 int arch_prepare_kprobe_ftrace(struct kprobe *p)
72 {
73 p->ainsn.insn = NULL;
74 p->ainsn.boostable = false;
75 return 0;
76 }
77