// SPDX-License-Identifier: GPL-2.0
/*
 * jump label x86 support
 *
 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
 *
 */
#include <linux/jump_label.h>
#include <linux/memory.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/cpu.h>
#include <asm/kprobes.h>
#include <asm/alternative.h>
#include <asm/text-patching.h>
#include <asm/insn.h>

int arch_jump_entry_size(struct jump_entry *entry)
{
        struct insn insn = {};

        insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
        BUG_ON(insn.length != 2 && insn.length != 5);

        return insn.length;
}

struct jump_label_patch {
        const void *code;
        int size;
};

static struct jump_label_patch
__jump_label_patch(struct jump_entry *entry, enum jump_label_type type)
{
        const void *expect, *code, *nop;
        const void *addr, *dest;
        int size;

        addr = (void *)jump_entry_code(entry);
        dest = (void *)jump_entry_target(entry);

        size = arch_jump_entry_size(entry);
        switch (size) {
        case JMP8_INSN_SIZE:
                code = text_gen_insn(JMP8_INSN_OPCODE, addr, dest);
                nop = x86_nops[size];
                break;

        case JMP32_INSN_SIZE:
                code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
                nop = x86_nops[size];
                break;

        default: BUG();
        }

        if (type == JUMP_LABEL_JMP)
                expect = nop;
        else
                expect = code;

        if (memcmp(addr, expect, size)) {
                /*
                 * The location is not an op that we were expecting.
                 * Something went wrong. Crash the box, as something could be
                 * corrupting the kernel.
                 */
                pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph != %5ph)) size:%d type:%d\n",
                                addr, addr, addr, expect, size, type);
                BUG();
        }

        if (type == JUMP_LABEL_NOP)
                code = nop;

        return (struct jump_label_patch){.code = code, .size = size};
}

static __always_inline void
__jump_label_transform(struct jump_entry *entry,
                       enum jump_label_type type,
                       int init)
{
        const struct jump_label_patch jlp = __jump_label_patch(entry, type);

        /*
         * As long as only a single processor is running and the code is still
         * not marked as RO, text_poke_early() can be used; Checking that
         * system_state is SYSTEM_BOOTING guarantees it. It will be set to
         * SYSTEM_SCHEDULING before other cores are awaken and before the
         * code is write-protected.
         *
         * At the time the change is being done, just ignore whether we
         * are doing nop -> jump or jump -> nop transition, and assume
         * always nop being the 'currently valid' instruction
         */
        if (init || system_state == SYSTEM_BOOTING) {
                text_poke_early((void *)jump_entry_code(entry), jlp.code, jlp.size);
                return;
        }

        smp_text_poke_single((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
}

static void __ref jump_label_transform(struct jump_entry *entry,
                                       enum jump_label_type type,
                                       int init)
{
        mutex_lock(&text_mutex);
        __jump_label_transform(entry, type, init);
        mutex_unlock(&text_mutex);
}

void arch_jump_label_transform(struct jump_entry *entry,
                               enum jump_label_type type)
{
        jump_label_transform(entry, type, 0);
}

bool arch_jump_label_transform_queue(struct jump_entry *entry,
                                     enum jump_label_type type)
{
        struct jump_label_patch jlp;

        if (system_state == SYSTEM_BOOTING) {
                /*
                 * Fallback to the non-batching mode.
                 */
                arch_jump_label_transform(entry, type);
                return true;
        }

        mutex_lock(&text_mutex);
        jlp = __jump_label_patch(entry, type);
        smp_text_poke_batch_add((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
        mutex_unlock(&text_mutex);
        return true;
}

void arch_jump_label_transform_apply(void)
{
        mutex_lock(&text_mutex);
        smp_text_poke_batch_finish();
        mutex_unlock(&text_mutex);
}