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 } 100