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 #include <asm/text-patching.h> 13 14 #include "common.h" 15 16 /* Ftrace callback handler for kprobes -- called under preempt disabled */ 17 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, 18 struct ftrace_ops *ops, struct ftrace_regs *fregs) 19 { 20 struct pt_regs *regs = ftrace_get_regs(fregs); 21 struct kprobe *p; 22 struct kprobe_ctlblk *kcb; 23 int bit; 24 25 if (unlikely(kprobe_ftrace_disabled)) 26 return; 27 28 bit = ftrace_test_recursion_trylock(ip, parent_ip); 29 if (bit < 0) 30 return; 31 32 p = get_kprobe((kprobe_opcode_t *)ip); 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 unsigned long orig_ip = instruction_pointer(regs); 41 42 /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ 43 instruction_pointer_set(regs, ip + INT3_INSN_SIZE); 44 45 __this_cpu_write(current_kprobe, p); 46 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 47 if (!p->pre_handler || !p->pre_handler(p, regs)) { 48 if (unlikely(p->post_handler)) { 49 /* 50 * Emulate singlestep (and also recover regs->ip) 51 * as if there is a 5byte nop 52 */ 53 instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE); 54 kcb->kprobe_status = KPROBE_HIT_SSDONE; 55 p->post_handler(p, regs, 0); 56 } 57 /* Recover IP address */ 58 instruction_pointer_set(regs, orig_ip); 59 } 60 /* 61 * If pre_handler returns !0, it changes regs->ip. We have to 62 * skip emulating post_handler. 63 */ 64 __this_cpu_write(current_kprobe, NULL); 65 } 66 out: 67 ftrace_test_recursion_unlock(bit); 68 } 69 NOKPROBE_SYMBOL(kprobe_ftrace_handler); 70 71 int arch_prepare_kprobe_ftrace(struct kprobe *p) 72 { 73 p->ainsn.insn = NULL; 74 p->ainsn.boostable = false; 75 return 0; 76 } 77