arch/x86/kernel/kprobes/ftrace.c

   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 preepmt disabed */
  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
  67 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  68 {
  69         p->ainsn.insn = NULL;
  70         p->ainsn.boostable = false;
  71         return 0;
  72 }