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 /* Ftrace callback handler for kprobes -- called under preepmt disabed */ 29 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, 30 struct ftrace_ops *ops, struct pt_regs *regs) 31 { 32 struct kprobe *p; 33 struct kprobe_ctlblk *kcb; 34 35 /* Preempt is disabled by ftrace */ 36 p = get_kprobe((kprobe_opcode_t *)ip); 37 if (unlikely(!p) || kprobe_disabled(p)) 38 return; 39 40 kcb = get_kprobe_ctlblk(); 41 if (kprobe_running()) { 42 kprobes_inc_nmissed_count(p); 43 } else { 44 unsigned long orig_ip = regs->ip; 45 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ 46 regs->ip = ip + sizeof(kprobe_opcode_t); 47 48 __this_cpu_write(current_kprobe, p); 49 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 50 if (!p->pre_handler || !p->pre_handler(p, regs)) { 51 /* 52 * Emulate singlestep (and also recover regs->ip) 53 * as if there is a 5byte nop 54 */ 55 regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE; 56 if (unlikely(p->post_handler)) { 57 kcb->kprobe_status = KPROBE_HIT_SSDONE; 58 p->post_handler(p, regs, 0); 59 } 60 regs->ip = orig_ip; 61 } 62 /* 63 * If pre_handler returns !0, it changes regs->ip. We have to 64 * skip emulating post_handler. 65 */ 66 __this_cpu_write(current_kprobe, NULL); 67 } 68 } 69 NOKPROBE_SYMBOL(kprobe_ftrace_handler); 70 71 int arch_prepare_kprobe_ftrace(struct kprobe *p) 72 { 73 p->ainsn.insn = NULL; 74 p->ainsn.boostable = false; 75 return 0; 76 } 77