LXR linux/arch/x86/kernel/kprobes/ftrace.c

   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 */
  16void 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        preempt_disable_notrace();
  29        p = get_kprobe((kprobe_opcode_t *)ip);
  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                unsigned long orig_ip = regs->ip;
  38                /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
  39                regs->ip = ip + sizeof(kprobe_opcode_t);
  40
  41                __this_cpu_write(current_kprobe, p);
  42                kcb->kprobe_status = KPROBE_HIT_ACTIVE;
  43                if (!p->pre_handler || !p->pre_handler(p, regs)) {
  44                        /*
  45                         * Emulate singlestep (and also recover regs->ip)
  46                         * as if there is a 5byte nop
  47                         */
  48                        regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
  49                        if (unlikely(p->post_handler)) {
  50                                kcb->kprobe_status = KPROBE_HIT_SSDONE;
  51                                p->post_handler(p, regs, 0);
  52                        }
  53                        regs->ip = orig_ip;
  54                }
  55                /*
  56                 * If pre_handler returns !0, it changes regs->ip. We have to
  57                 * skip emulating post_handler.
  58                 */
  59                __this_cpu_write(current_kprobe, NULL);
  60        }
  61out:
  62        preempt_enable_notrace();
  63        ftrace_test_recursion_unlock(bit);
  64}
  65NOKPROBE_SYMBOL(kprobe_ftrace_handler);
  66
  67int arch_prepare_kprobe_ftrace(struct kprobe *p)
  68{
  69        p->ainsn.insn = NULL;
  70        p->ainsn.boostable = false;
  71        return 0;
  72}
  73