1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/kprobes.h>
4
5 /* Ftrace callback handler for kprobes -- called under preepmt disabled */
6 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
7 struct ftrace_ops *ops, struct ftrace_regs *fregs)
8 {
9 int bit;
10 bool lr_saver = false;
11 struct kprobe *p;
12 struct kprobe_ctlblk *kcb;
13 struct pt_regs *regs;
14
15 if (unlikely(kprobe_ftrace_disabled))
16 return;
17
18 bit = ftrace_test_recursion_trylock(ip, parent_ip);
19 if (bit < 0)
20 return;
21
22 regs = ftrace_get_regs(fregs);
23 p = get_kprobe((kprobe_opcode_t *)ip);
24 if (!p) {
25 p = get_kprobe((kprobe_opcode_t *)(ip - MCOUNT_INSN_SIZE));
26 if (unlikely(!p) || kprobe_disabled(p))
27 goto out;
28 lr_saver = true;
29 }
30
31 kcb = get_kprobe_ctlblk();
32 if (kprobe_running()) {
33 kprobes_inc_nmissed_count(p);
34 } else {
35 unsigned long orig_ip = instruction_pointer(regs);
36
37 if (lr_saver)
38 ip -= MCOUNT_INSN_SIZE;
39 instruction_pointer_set(regs, ip);
40 __this_cpu_write(current_kprobe, p);
41 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
42 if (!p->pre_handler || !p->pre_handler(p, regs)) {
43 /*
44 * Emulate singlestep (and also recover regs->pc)
45 * as if there is a nop
46 */
47 instruction_pointer_set(regs,
48 (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 instruction_pointer_set(regs, orig_ip);
54 }
55 /*
56 * If pre_handler returns !0, it changes regs->pc. We have to
57 * skip emulating post_handler.
58 */
59 __this_cpu_write(current_kprobe, NULL);
60 }
61 out:
62 ftrace_test_recursion_unlock(bit);
63 }
64 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
65
66 int arch_prepare_kprobe_ftrace(struct kprobe *p)
67 {
68 p->ainsn.api.insn = NULL;
69 return 0;
70 }
71
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