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 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> 20 * IBM Corporation 21 */ 22 #include <linux/kprobes.h> 23 #include <linux/ptrace.h> 24 #include <linux/hardirq.h> 25 #include <linux/preempt.h> 26 #include <linux/ftrace.h> 27 28 /* Ftrace callback handler for kprobes */ 29 void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, 30 struct ftrace_ops *ops, struct pt_regs *regs) 31 { 32 struct kprobe *p; 33 struct kprobe_ctlblk *kcb; 34 35 p = get_kprobe((kprobe_opcode_t *)nip); 36 if (unlikely(!p) || kprobe_disabled(p)) 37 return; 38 39 kcb = get_kprobe_ctlblk(); 40 if (kprobe_running()) { 41 kprobes_inc_nmissed_count(p); 42 } else { 43 /* 44 * On powerpc, NIP is *before* this instruction for the 45 * pre handler 46 */ 47 regs->nip -= MCOUNT_INSN_SIZE; 48 49 __this_cpu_write(current_kprobe, p); 50 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 51 if (!p->pre_handler || !p->pre_handler(p, regs)) { 52 /* 53 * Emulate singlestep (and also recover regs->nip) 54 * as if there is a nop 55 */ 56 regs->nip += MCOUNT_INSN_SIZE; 57 if (unlikely(p->post_handler)) { 58 kcb->kprobe_status = KPROBE_HIT_SSDONE; 59 p->post_handler(p, regs, 0); 60 } 61 } 62 /* 63 * If pre_handler returns !0, it changes regs->nip. 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 = -1; 75 return 0; 76 } 77