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 if (unlikely(kprobe_ftrace_disabled)) 25 return; 26 27 bit = ftrace_test_recursion_trylock(nip, parent_nip); 28 if (bit < 0) 29 return; 30 31 regs = ftrace_get_regs(fregs); 32 p = get_kprobe((kprobe_opcode_t *)nip); 33 if (unlikely(!p) || kprobe_disabled(p)) 34 goto out; 35 36 kcb = get_kprobe_ctlblk(); 37 if (kprobe_running()) { 38 kprobes_inc_nmissed_count(p); 39 } else { 40 /* 41 * On powerpc, NIP is *before* this instruction for the 42 * pre handler 43 */ 44 regs_add_return_ip(regs, -MCOUNT_INSN_SIZE); 45 46 __this_cpu_write(current_kprobe, p); 47 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 48 if (!p->pre_handler || !p->pre_handler(p, regs)) { 49 /* 50 * Emulate singlestep (and also recover regs->nip) 51 * as if there is a nop 52 */ 53 regs_add_return_ip(regs, MCOUNT_INSN_SIZE); 54 if (unlikely(p->post_handler)) { 55 kcb->kprobe_status = KPROBE_HIT_SSDONE; 56 p->post_handler(p, regs, 0); 57 } 58 } 59 /* 60 * If pre_handler returns !0, it changes regs->nip. We have to 61 * skip emulating post_handler. 62 */ 63 __this_cpu_write(current_kprobe, NULL); 64 } 65 out: 66 ftrace_test_recursion_unlock(bit); 67 } 68 NOKPROBE_SYMBOL(kprobe_ftrace_handler); 69 70 int arch_prepare_kprobe_ftrace(struct kprobe *p) 71 { 72 p->ainsn.insn = NULL; 73 p->ainsn.boostable = -1; 74 return 0; 75 } 76