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 pt_regs *regs)
  18 {
  19         struct kprobe *p;
  20         struct kprobe_ctlblk *kcb;
  21
  22         /* Preempt is disabled by ftrace */
  23         p = get_kprobe((kprobe_opcode_t *)ip);
  24         if (unlikely(!p) || kprobe_disabled(p))
  25                 return;
  26
  27         kcb = get_kprobe_ctlblk();
  28         if (kprobe_running()) {
  29                 kprobes_inc_nmissed_count(p);
  30         } else {
  31                 unsigned long orig_ip = regs->ip;
  32                 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
  33                 regs->ip = ip + sizeof(kprobe_opcode_t);
  34
  35                 __this_cpu_write(current_kprobe, p);
  36                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  37                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
  38                         /*
  39                          * Emulate singlestep (and also recover regs->ip)
  40                          * as if there is a 5byte nop
  41                          */
  42                         regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
  43                         if (unlikely(p->post_handler)) {
  44                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
  45                                 p->post_handler(p, regs, 0);
  46                         }
  47                         regs->ip = orig_ip;
  48                 }
  49                 /*
  50                  * If pre_handler returns !0, it changes regs->ip. We have to
  51                  * skip emulating post_handler.
  52                  */
  53                 __this_cpu_write(current_kprobe, NULL);
  54         }
  55 }
  56 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  57
  58 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  59 {
  60         p->ainsn.insn = NULL;
  61         p->ainsn.boostable = false;
  62         return 0;
  63 }