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 ftrace_regs *fregs) 18 { 19 struct kprobe *p; 20 struct kprobe_ctlblk *kcb; 21 struct pt_regs *regs; 22 int bit; 23 24 bit = ftrace_test_recursion_trylock(nip, parent_nip); 25 if (bit < 0) 26 return; 27 28 regs = ftrace_get_regs(fregs); 29 preempt_disable_notrace(); 30 p = get_kprobe((kprobe_opcode_t *)nip); 31 if (unlikely(!p) || kprobe_disabled(p)) 32 goto out; 33 34 kcb = get_kprobe_ctlblk(); 35 if (kprobe_running()) { 36 kprobes_inc_nmissed_count(p); 37 } else { 38 /* 39 * On powerpc, NIP is *before* this instruction for the 40 * pre handler 41 */ 42 regs_add_return_ip(regs, -MCOUNT_INSN_SIZE); 43 44 __this_cpu_write(current_kprobe, p); 45 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 46 if (!p->pre_handler || !p->pre_handler(p, regs)) { 47 /* 48 * Emulate singlestep (and also recover regs->nip) 49 * as if there is a nop 50 */ 51 regs_add_return_ip(regs, MCOUNT_INSN_SIZE); 52 if (unlikely(p->post_handler)) { 53 kcb->kprobe_status = KPROBE_HIT_SSDONE; 54 p->post_handler(p, regs, 0); 55 } 56 } 57 /* 58 * If pre_handler returns !0, it changes regs->nip. We have to 59 * skip emulating post_handler. 60 */ 61 __this_cpu_write(current_kprobe, NULL); 62 } 63 out: 64 preempt_enable_notrace(); 65 ftrace_test_recursion_unlock(bit); 66 } 67 NOKPROBE_SYMBOL(kprobe_ftrace_handler); 68 69 int arch_prepare_kprobe_ftrace(struct kprobe *p) 70 { 71 p->ainsn.insn = NULL; 72 p->ainsn.boostable = -1; 73 return 0; 74 } 75