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