1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Dynamic Ftrace based Kprobes Optimization 4 * 5 * Copyright (C) Hitachi Ltd., 2012 6 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> 7 * IBM Corporation 8 */ 9 #include <linux/kprobes.h> 10 #include <linux/ptrace.h> 11 #include <linux/hardirq.h> 12 #include <linux/preempt.h> 13 #include <linux/ftrace.h> 14 15 /* Ftrace callback handler for kprobes */ 16 void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, 17 struct ftrace_ops *ops, struct pt_regs *regs) 18 { 19 struct kprobe *p; 20 struct kprobe_ctlblk *kcb; 21 22 p = get_kprobe((kprobe_opcode_t *)nip); 23 if (unlikely(!p) || kprobe_disabled(p)) 24 return; 25 26 kcb = get_kprobe_ctlblk(); 27 if (kprobe_running()) { 28 kprobes_inc_nmissed_count(p); 29 } else { 30 /* 31 * On powerpc, NIP is *before* this instruction for the 32 * pre handler 33 */ 34 regs->nip -= MCOUNT_INSN_SIZE; 35 36 __this_cpu_write(current_kprobe, p); 37 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 38 if (!p->pre_handler || !p->pre_handler(p, regs)) { 39 /* 40 * Emulate singlestep (and also recover regs->nip) 41 * as if there is a nop 42 */ 43 regs->nip += MCOUNT_INSN_SIZE; 44 if (unlikely(p->post_handler)) { 45 kcb->kprobe_status = KPROBE_HIT_SSDONE; 46 p->post_handler(p, regs, 0); 47 } 48 } 49 /* 50 * If pre_handler returns !0, it changes regs->nip. We have to 51 * skip emulating post_handler. 52 */ 53 __this_cpu_write(current_kprobe, NULL); 54 } 55 } 56 NOKPROBE_SYMBOL(kprobe_ftrace_handler); 57 58 int arch_prepare_kprobe_ftrace(struct kprobe *p) 59 { 60 p->ainsn.insn = NULL; 61 p->ainsn.boostable = -1; 62 return 0; 63 } 64