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 int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  29                              struct kprobe_ctlblk *kcb)
  30 {
  31         /*
  32          * Emulate singlestep (and also recover regs->ip)
  33          * as if there is a 5byte nop
  34          */
  35         regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
  36         if (unlikely(p->post_handler)) {
  37                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
  38                 p->post_handler(p, regs, 0);
  39         }
  40         __this_cpu_write(current_kprobe, NULL);
  41         return 1;
  42 }
  43
  44 int __kprobes skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  45                               struct kprobe_ctlblk *kcb)
  46 {
  47         if (kprobe_ftrace(p))
  48                 return __skip_singlestep(p, regs, kcb);
  49         else
  50                 return 0;
  51 }
  52
  53 /* Ftrace callback handler for kprobes */
  54 void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
  55                                      struct ftrace_ops *ops, struct pt_regs *regs)
  56 {
  57         struct kprobe *p;
  58         struct kprobe_ctlblk *kcb;
  59         unsigned long flags;
  60
  61         /* Disable irq for emulating a breakpoint and avoiding preempt */
  62         local_irq_save(flags);
  63
  64         p = get_kprobe((kprobe_opcode_t *)ip);
  65         if (unlikely(!p) || kprobe_disabled(p))
  66                 goto end;
  67
  68         kcb = get_kprobe_ctlblk();
  69         if (kprobe_running()) {
  70                 kprobes_inc_nmissed_count(p);
  71         } else {
  72                 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
  73                 regs->ip = ip + sizeof(kprobe_opcode_t);
  74
  75                 __this_cpu_write(current_kprobe, p);
  76                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  77                 if (!p->pre_handler || !p->pre_handler(p, regs))
  78                         __skip_singlestep(p, regs, kcb);
  79                 /*
  80                  * If pre_handler returns !0, it sets regs->ip and
  81                  * resets current kprobe.
  82                  */
  83         }
  84 end:
  85         local_irq_restore(flags);
  86 }
  87
  88 int __kprobes arch_prepare_kprobe_ftrace(struct kprobe *p)
  89 {
  90         p->ainsn.insn = NULL;
  91         p->ainsn.boostable = -1;
  92         return 0;
  93 }