// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Dynamic Ftrace based Kprobes Optimization
 *
 * Copyright (C) Hitachi Ltd., 2012
 */
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/hardirq.h>
#include <linux/preempt.h>
#include <linux/ftrace.h>
#include <asm/text-patching.h>

#include "common.h"

/* Ftrace callback handler for kprobes -- called under preempt disabled */
void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
                           struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
        struct pt_regs *regs = ftrace_get_regs(fregs);
        struct kprobe *p;
        struct kprobe_ctlblk *kcb;
        int bit;

        if (unlikely(kprobe_ftrace_disabled))
                return;

        bit = ftrace_test_recursion_trylock(ip, parent_ip);
        if (bit < 0)
                return;

        p = get_kprobe((kprobe_opcode_t *)ip);
        if (unlikely(!p) || kprobe_disabled(p))
                goto out;

        kcb = get_kprobe_ctlblk();
        if (kprobe_running()) {
                kprobes_inc_nmissed_count(p);
        } else {
                unsigned long orig_ip = instruction_pointer(regs);

                /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
                instruction_pointer_set(regs, ip + INT3_INSN_SIZE);

                __this_cpu_write(current_kprobe, p);
                kcb->kprobe_status = KPROBE_HIT_ACTIVE;
                if (!p->pre_handler || !p->pre_handler(p, regs)) {
                        if (unlikely(p->post_handler)) {
                                /*
                                 * Emulate singlestep (and also recover regs->ip)
                                 * as if there is a 5byte nop
                                 */
                                instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
                                kcb->kprobe_status = KPROBE_HIT_SSDONE;
                                p->post_handler(p, regs, 0);
                        }
                        /* Recover IP address */
                        instruction_pointer_set(regs, orig_ip);
                }
                /*
                 * If pre_handler returns !0, it changes regs->ip. We have to
                 * skip emulating post_handler.
                 */
                __this_cpu_write(current_kprobe, NULL);
        }
out:
        ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);

int arch_prepare_kprobe_ftrace(struct kprobe *p)
{
        p->ainsn.insn = NULL;
        p->ainsn.boostable = false;
        return 0;
}