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 int __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         return 1;
  45 }
  46
  47 int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  48                     struct kprobe_ctlblk *kcb)
  49 {
  50         if (kprobe_ftrace(p))
  51                 return __skip_singlestep(p, regs, kcb, 0);
  52         else
  53                 return 0;
  54 }
  55 NOKPROBE_SYMBOL(skip_singlestep);
  56
  57 /* Ftrace callback handler for kprobes */
  58 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
  59                            struct ftrace_ops *ops, struct pt_regs *regs)
  60 {
  61         struct kprobe *p;
  62         struct kprobe_ctlblk *kcb;
  63         unsigned long flags;
  64
  65         /* Disable irq for emulating a breakpoint and avoiding preempt */
  66         local_irq_save(flags);
  67
  68         p = get_kprobe((kprobe_opcode_t *)ip);
  69         if (unlikely(!p) || kprobe_disabled(p))
  70                 goto end;
  71
  72         kcb = get_kprobe_ctlblk();
  73         if (kprobe_running()) {
  74                 kprobes_inc_nmissed_count(p);
  75         } else {
  76                 unsigned long orig_ip = regs->ip;
  77                 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
  78                 regs->ip = ip + sizeof(kprobe_opcode_t);
  79
  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                 /*
  85                  * If pre_handler returns !0, it sets regs->ip and
  86                  * resets current kprobe.
  87                  */
  88         }
  89 end:
  90         local_irq_restore(flags);
  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 = -1;
  98         return 0;
  99 }