arch/x86/kernel/kprobes/ftrace.c

   1 /*
   2  * Dynamic Ftrace based Kprobes Optimization
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) Hitachi Ltd., 2012
  19  */
  20 #include <linux/kprobes.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/hardirq.h>
  23 #include <linux/preempt.h>
  24 #include <linux/ftrace.h>
  25
  26 #include "common.h"
  27
  28 static nokprobe_inline
  29 void __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  30                       struct kprobe_ctlblk *kcb, unsigned long orig_ip)
  31 {
  32         /*
  33          * Emulate singlestep (and also recover regs->ip)
  34          * as if there is a 5byte nop
  35          */
  36         regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
  37         if (unlikely(p->post_handler)) {
  38                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
  39                 p->post_handler(p, regs, 0);
  40         }
  41         __this_cpu_write(current_kprobe, NULL);
  42         if (orig_ip)
  43                 regs->ip = orig_ip;
  44 }
  45
  46 int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  47                     struct kprobe_ctlblk *kcb)
  48 {
  49         if (kprobe_ftrace(p)) {
  50                 __skip_singlestep(p, regs, kcb, 0);
  51                 preempt_enable_no_resched();
  52                 return 1;
  53         }
  54         return 0;
  55 }
  56 NOKPROBE_SYMBOL(skip_singlestep);
  57
  58 /* Ftrace callback handler for kprobes -- called under preepmt disabed */
  59 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
  60                            struct ftrace_ops *ops, struct pt_regs *regs)
  61 {
  62         struct kprobe *p;
  63         struct kprobe_ctlblk *kcb;
  64
  65         /* Preempt is disabled by ftrace */
  66         p = get_kprobe((kprobe_opcode_t *)ip);
  67         if (unlikely(!p) || kprobe_disabled(p))
  68                 return;
  69
  70         kcb = get_kprobe_ctlblk();
  71         if (kprobe_running()) {
  72                 kprobes_inc_nmissed_count(p);
  73         } else {
  74                 unsigned long orig_ip = regs->ip;
  75                 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
  76                 regs->ip = ip + sizeof(kprobe_opcode_t);
  77
  78                 /* To emulate trap based kprobes, preempt_disable here */
  79                 preempt_disable();
  80                 __this_cpu_write(current_kprobe, p);
  81                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  82                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
  83                         __skip_singlestep(p, regs, kcb, orig_ip);
  84                         preempt_enable_no_resched();
  85                 }
  86                 /*
  87                  * If pre_handler returns !0, it sets regs->ip and
  88                  * resets current kprobe, and keep preempt count +1.
  89                  */
  90         }
  91 }
  92 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  93
  94 int arch_prepare_kprobe_ftrace(struct kprobe *p)
  95 {
  96         p->ainsn.insn = NULL;
  97         p->ainsn.boostable = false;
  98         return 0;
  99 }