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 } 94