1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Dynamic Ftrace based Kprobes Optimization 4 * 5 * Copyright (C) Hitachi Ltd., 2012 6 */ 7 #include <linux/kprobes.h> 8 #include <linux/ptrace.h> 9 #include <linux/hardirq.h> 10 #include <linux/preempt.h> 11 #include <linux/ftrace.h> 12 13 #include "common.h" 14 15 /* Ftrace callback handler for kprobes -- called under preempt disabled */ 16 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, 17 struct ftrace_ops *ops, struct ftrace_regs *fregs) 18 { 19 struct pt_regs *regs = ftrace_get_regs(fregs); 20 struct kprobe *p; 21 struct kprobe_ctlblk *kcb; 22 int bit; 23 24 bit = ftrace_test_recursion_trylock(ip, parent_ip); 25 if (bit < 0) 26 return; 27 28 p = get_kprobe((kprobe_opcode_t *)ip); 29 if (unlikely(!p) || kprobe_disabled(p)) 30 goto out; 31 32 kcb = get_kprobe_ctlblk(); 33 if (kprobe_running()) { 34 kprobes_inc_nmissed_count(p); 35 } else { 36 unsigned long orig_ip = regs->ip; 37 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ 38 regs->ip = ip + sizeof(kprobe_opcode_t); 39 40 __this_cpu_write(current_kprobe, p); 41 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 42 if (!p->pre_handler || !p->pre_handler(p, regs)) { 43 /* 44 * Emulate singlestep (and also recover regs->ip) 45 * as if there is a 5byte nop 46 */ 47 regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE; 48 if (unlikely(p->post_handler)) { 49 kcb->kprobe_status = KPROBE_HIT_SSDONE; 50 p->post_handler(p, regs, 0); 51 } 52 regs->ip = orig_ip; 53 } 54 /* 55 * If pre_handler returns !0, it changes regs->ip. We have to 56 * skip emulating post_handler. 57 */ 58 __this_cpu_write(current_kprobe, NULL); 59 } 60 out: 61 ftrace_test_recursion_unlock(bit); 62 } 63 NOKPROBE_SYMBOL(kprobe_ftrace_handler); 64 65 int arch_prepare_kprobe_ftrace(struct kprobe *p) 66 { 67 p->ainsn.insn = NULL; 68 p->ainsn.boostable = false; 69 return 0; 70 } 71