// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Dynamic Ftrace based Kprobes Optimization
 *
 * Copyright (C) Hitachi Ltd., 2012
 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
 *                IBM Corporation
 */
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/hardirq.h>
#include <linux/preempt.h>
#include <linux/ftrace.h>

/* Ftrace callback handler for kprobes */
void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
                           struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
        struct kprobe *p;
        struct kprobe_ctlblk *kcb;
        struct pt_regs *regs;
        int bit;

        if (unlikely(kprobe_ftrace_disabled))
                return;

        bit = ftrace_test_recursion_trylock(nip, parent_nip);
        if (bit < 0)
                return;

        regs = ftrace_get_regs(fregs);
        p = get_kprobe((kprobe_opcode_t *)nip);
        if (unlikely(!p) || kprobe_disabled(p))
                goto out;

        kcb = get_kprobe_ctlblk();
        if (kprobe_running()) {
                kprobes_inc_nmissed_count(p);
        } else {
                /*
                 * On powerpc, NIP is *before* this instruction for the
                 * pre handler
                 */
                regs_add_return_ip(regs, -MCOUNT_INSN_SIZE);

                __this_cpu_write(current_kprobe, p);
                kcb->kprobe_status = KPROBE_HIT_ACTIVE;
                if (!p->pre_handler || !p->pre_handler(p, regs)) {
                        /*
                         * Emulate singlestep (and also recover regs->nip)
                         * as if there is a nop
                         */
                        regs_add_return_ip(regs, MCOUNT_INSN_SIZE);
                        if (unlikely(p->post_handler)) {
                                kcb->kprobe_status = KPROBE_HIT_SSDONE;
                                p->post_handler(p, regs, 0);
                        }
                }
                /*
                 * If pre_handler returns !0, it changes regs->nip. 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 = -1;
        return 0;
}