// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Helpers for initial module or kernel cmdline parsing
 * Copyright (C) 2001 Rusty Russell.
 */
#include <linux/ctype.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/kstrtox.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/overflow.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/string.h>

#ifdef CONFIG_SYSFS
/* Protects all built-in parameters, modules use their own param_lock */
static DEFINE_MUTEX(param_lock);

/* Use the module's mutex, or if built-in use the built-in mutex */
#ifdef CONFIG_MODULES
#define KPARAM_MUTEX(mod)       ((mod) ? &(mod)->param_lock : &param_lock)
#else
#define KPARAM_MUTEX(mod)       (&param_lock)
#endif

static inline void check_kparam_locked(struct module *mod)
{
        BUG_ON(!mutex_is_locked(KPARAM_MUTEX(mod)));
}
#else
static inline void check_kparam_locked(struct module *mod)
{
}
#endif /* !CONFIG_SYSFS */

/* This just allows us to keep track of which parameters are kmalloced. */
struct kmalloced_param {
        struct list_head list;
        char val[];
};
static LIST_HEAD(kmalloced_params);
static DEFINE_SPINLOCK(kmalloced_params_lock);

static void *kmalloc_parameter(unsigned int size)
{
        struct kmalloced_param *p;

        p = kmalloc(size_add(sizeof(*p), size), GFP_KERNEL);
        if (!p)
                return NULL;

        spin_lock(&kmalloced_params_lock);
        list_add(&p->list, &kmalloced_params);
        spin_unlock(&kmalloced_params_lock);

        return p->val;
}

/* Does nothing if parameter wasn't kmalloced above. */
static void maybe_kfree_parameter(void *param)
{
        struct kmalloced_param *p;

        spin_lock(&kmalloced_params_lock);
        list_for_each_entry(p, &kmalloced_params, list) {
                if (p->val == param) {
                        list_del(&p->list);
                        kfree(p);
                        break;
                }
        }
        spin_unlock(&kmalloced_params_lock);
}

static char dash2underscore(char c)
{
        if (c == '-')
                return '_';
        return c;
}

bool parameqn(const char *a, const char *b, size_t n)
{
        size_t i;

        for (i = 0; i < n; i++) {
                if (dash2underscore(a[i]) != dash2underscore(b[i]))
                        return false;
        }
        return true;
}

bool parameq(const char *a, const char *b)
{
        return parameqn(a, b, strlen(a)+1);
}

static bool param_check_unsafe(const struct kernel_param *kp)
{
        if (kp->flags & KERNEL_PARAM_FL_HWPARAM &&
            security_locked_down(LOCKDOWN_MODULE_PARAMETERS))
                return false;

        if (kp->flags & KERNEL_PARAM_FL_UNSAFE) {
                pr_notice("Setting dangerous option %s - tainting kernel\n",
                          kp->name);
                add_taint(TAINT_USER, LOCKDEP_STILL_OK);
        }

        return true;
}

static int parse_one(char *param,
                     char *val,
                     const char *doing,
                     const struct kernel_param *params,
                     unsigned num_params,
                     s16 min_level,
                     s16 max_level,
                     void *arg, parse_unknown_fn handle_unknown)
{
        unsigned int i;
        int err;

        /* Find parameter */
        for (i = 0; i < num_params; i++) {
                if (parameq(param, params[i].name)) {
                        if (params[i].level < min_level
                            || params[i].level > max_level)
                                return 0;
                        /* No one handled NULL, so do it here. */
                        if (!val &&
                            !(params[i].ops->flags & KERNEL_PARAM_OPS_FL_NOARG))
                                return -EINVAL;
                        pr_debug("handling %s with %p\n", param,
                                params[i].ops->set);
                        kernel_param_lock(params[i].mod);
                        if (param_check_unsafe(&params[i]))
                                err = params[i].ops->set(val, &params[i]);
                        else
                                err = -EPERM;
                        kernel_param_unlock(params[i].mod);
                        return err;
                }
        }

        if (handle_unknown) {
                pr_debug("doing %s: %s='%s'\n", doing, param, val);
                return handle_unknown(param, val, doing, arg);
        }

        pr_debug("Unknown argument '%s'\n", param);
        return -ENOENT;
}

/* Args looks like "foo=bar,bar2 baz=fuz wiz". */
char *parse_args(const char *doing,
                 char *args,
                 const struct kernel_param *params,
                 unsigned num,
                 s16 min_level,
                 s16 max_level,
                 void *arg, parse_unknown_fn unknown)
{
        char *param, *val, *err = NULL;

        /* Chew leading spaces */
        args = skip_spaces(args);

        if (*args)
                pr_debug("doing %s, parsing ARGS: '%s'\n", doing, args);

        while (*args) {
                int ret;
                int irq_was_disabled;

                args = next_arg(args, &param, &val);
                /* Stop at -- */
                if (!val && strcmp(param, "--") == 0)
                        return err ?: args;
                irq_was_disabled = irqs_disabled();
                ret = parse_one(param, val, doing, params, num,
                                min_level, max_level, arg, unknown);
                if (irq_was_disabled && !irqs_disabled())
                        pr_warn("%s: option '%s' enabled irq's!\n",
                                doing, param);

                switch (ret) {
                case 0:
                        continue;
                case -ENOENT:
                        pr_err("%s: Unknown parameter `%s'\n", doing, param);
                        break;
                case -ENOSPC:
                        pr_err("%s: `%s' too large for parameter `%s'\n",
                               doing, val ?: "", param);
                        break;
                default:
                        pr_err("%s: `%s' invalid for parameter `%s'\n",
                               doing, val ?: "", param);
                        break;
                }

                err = ERR_PTR(ret);
        }

        return err;
}

/* Lazy bastard, eh? */
#define STANDARD_PARAM_DEF(name, type, format, strtolfn)                \
        int param_set_##name(const char *val, const struct kernel_param *kp) \
        {                                                               \
                return strtolfn(val, 0, (type *)kp->arg);               \
        }                                                               \
        int param_get_##name(char *buffer, const struct kernel_param *kp) \
        {                                                               \
                return scnprintf(buffer, PAGE_SIZE, format "\n",        \
                                *((type *)kp->arg));                    \
        }                                                               \
        const struct kernel_param_ops param_ops_##name = {                      \
                .set = param_set_##name,                                \
                .get = param_get_##name,                                \
        };                                                              \
        EXPORT_SYMBOL(param_set_##name);                                \
        EXPORT_SYMBOL(param_get_##name);                                \
        EXPORT_SYMBOL(param_ops_##name)


STANDARD_PARAM_DEF(byte,        unsigned char,          "%hhu",         kstrtou8);
STANDARD_PARAM_DEF(short,       short,                  "%hi",          kstrtos16);
STANDARD_PARAM_DEF(ushort,      unsigned short,         "%hu",          kstrtou16);
STANDARD_PARAM_DEF(int,         int,                    "%i",           kstrtoint);
STANDARD_PARAM_DEF(uint,        unsigned int,           "%u",           kstrtouint);
STANDARD_PARAM_DEF(long,        long,                   "%li",          kstrtol);
STANDARD_PARAM_DEF(ulong,       unsigned long,          "%lu",          kstrtoul);
STANDARD_PARAM_DEF(ullong,      unsigned long long,     "%llu",         kstrtoull);
STANDARD_PARAM_DEF(hexint,      unsigned int,           "%#08x",        kstrtouint);

int param_set_uint_minmax(const char *val, const struct kernel_param *kp,
                unsigned int min, unsigned int max)
{
        unsigned int num;
        int ret;

        if (!val)
                return -EINVAL;
        ret = kstrtouint(val, 0, &num);
        if (ret)
                return ret;
        if (num < min || num > max)
                return -EINVAL;
        *((unsigned int *)kp->arg) = num;
        return 0;
}
EXPORT_SYMBOL_GPL(param_set_uint_minmax);

int param_set_charp(const char *val, const struct kernel_param *kp)
{
        size_t len, maxlen = 1024;

        len = strnlen(val, maxlen + 1);
        if (len == maxlen + 1) {
                pr_err("%s: string parameter too long\n", kp->name);
                return -ENOSPC;
        }

        maybe_kfree_parameter(*(char **)kp->arg);

        /*
         * This is a hack. We can't kmalloc() in early boot, and we
         * don't need to; this mangled commandline is preserved.
         */
        if (slab_is_available()) {
                *(char **)kp->arg = kmalloc_parameter(len + 1);
                if (!*(char **)kp->arg)
                        return -ENOMEM;
                strcpy(*(char **)kp->arg, val);
        } else
                *(const char **)kp->arg = val;

        return 0;
}
EXPORT_SYMBOL(param_set_charp);

int param_get_charp(char *buffer, const struct kernel_param *kp)
{
        return scnprintf(buffer, PAGE_SIZE, "%s\n", *((char **)kp->arg));
}
EXPORT_SYMBOL(param_get_charp);

void param_free_charp(void *arg)
{
        maybe_kfree_parameter(*((char **)arg));
}
EXPORT_SYMBOL(param_free_charp);

const struct kernel_param_ops param_ops_charp = {
        .set = param_set_charp,
        .get = param_get_charp,
        .free = param_free_charp,
};
EXPORT_SYMBOL(param_ops_charp);

/* Actually could be a bool or an int, for historical reasons. */
int param_set_bool(const char *val, const struct kernel_param *kp)
{
        /* No equals means "set"... */
        if (!val) val = "1";

        /* One of =[yYnN01] */
        return kstrtobool(val, kp->arg);
}
EXPORT_SYMBOL(param_set_bool);

int param_get_bool(char *buffer, const struct kernel_param *kp)
{
        /* Y and N chosen as being relatively non-coder friendly */
        return sprintf(buffer, "%c\n", *(bool *)kp->arg ? 'Y' : 'N');
}
EXPORT_SYMBOL(param_get_bool);

const struct kernel_param_ops param_ops_bool = {
        .flags = KERNEL_PARAM_OPS_FL_NOARG,
        .set = param_set_bool,
        .get = param_get_bool,
};
EXPORT_SYMBOL(param_ops_bool);

int param_set_bool_enable_only(const char *val, const struct kernel_param *kp)
{
        int err;
        bool new_value;
        bool orig_value = *(bool *)kp->arg;
        struct kernel_param dummy_kp = *kp;

        dummy_kp.arg = &new_value;

        err = param_set_bool(val, &dummy_kp);
        if (err)
                return err;

        /* Don't let them unset it once it's set! */
        if (!new_value && orig_value)
                return -EROFS;

        if (new_value)
                err = param_set_bool(val, kp);

        return err;
}
EXPORT_SYMBOL_GPL(param_set_bool_enable_only);

const struct kernel_param_ops param_ops_bool_enable_only = {
        .flags = KERNEL_PARAM_OPS_FL_NOARG,
        .set = param_set_bool_enable_only,
        .get = param_get_bool,
};
EXPORT_SYMBOL_GPL(param_ops_bool_enable_only);

/* This one must be bool. */
int param_set_invbool(const char *val, const struct kernel_param *kp)
{
        int ret;
        bool boolval;
        struct kernel_param dummy;

        dummy.arg = &boolval;
        ret = param_set_bool(val, &dummy);
        if (ret == 0)
                *(bool *)kp->arg = !boolval;
        return ret;
}
EXPORT_SYMBOL(param_set_invbool);

int param_get_invbool(char *buffer, const struct kernel_param *kp)
{
        return sprintf(buffer, "%c\n", (*(bool *)kp->arg) ? 'N' : 'Y');
}
EXPORT_SYMBOL(param_get_invbool);

const struct kernel_param_ops param_ops_invbool = {
        .set = param_set_invbool,
        .get = param_get_invbool,
};
EXPORT_SYMBOL(param_ops_invbool);

int param_set_bint(const char *val, const struct kernel_param *kp)
{
        /* Match bool exactly, by re-using it. */
        struct kernel_param boolkp = *kp;
        bool v;
        int ret;

        boolkp.arg = &v;

        ret = param_set_bool(val, &boolkp);
        if (ret == 0)
                *(int *)kp->arg = v;
        return ret;
}
EXPORT_SYMBOL(param_set_bint);

const struct kernel_param_ops param_ops_bint = {
        .flags = KERNEL_PARAM_OPS_FL_NOARG,
        .set = param_set_bint,
        .get = param_get_int,
};
EXPORT_SYMBOL(param_ops_bint);

/* We break the rule and mangle the string. */
static int param_array(struct module *mod,
                       const char *name,
                       const char *val,
                       unsigned int min, unsigned int max,
                       void *elem, int elemsize,
                       int (*set)(const char *, const struct kernel_param *kp),
                       s16 level,
                       unsigned int *num)
{
        int ret;
        struct kernel_param kp;
        char save;

        /* Get the name right for errors. */
        kp.name = name;
        kp.arg = elem;
        kp.level = level;

        *num = 0;
        /* We expect a comma-separated list of values. */
        do {
                int len;

                if (*num == max) {
                        pr_err("%s: can only take %i arguments\n", name, max);
                        return -EINVAL;
                }
                len = strcspn(val, ",");

                /* nul-terminate and parse */
                save = val[len];
                ((char *)val)[len] = '\0';
                check_kparam_locked(mod);
                ret = set(val, &kp);

                if (ret != 0)
                        return ret;
                kp.arg += elemsize;
                val += len+1;
                (*num)++;
        } while (save == ',');

        if (*num < min) {
                pr_err("%s: needs at least %i arguments\n", name, min);
                return -EINVAL;
        }
        return 0;
}

static int param_array_set(const char *val, const struct kernel_param *kp)
{
        const struct kparam_array *arr = kp->arr;
        unsigned int temp_num;

        return param_array(kp->mod, kp->name, val, 1, arr->max, arr->elem,
                           arr->elemsize, arr->ops->set, kp->level,
                           arr->num ?: &temp_num);
}

static int param_array_get(char *buffer, const struct kernel_param *kp)
{
        int i, off, ret;
        const struct kparam_array *arr = kp->arr;
        struct kernel_param p = *kp;

        for (i = off = 0; i < (arr->num ? *arr->num : arr->max); i++) {
                /* Replace \n with comma */
                if (i)
                        buffer[off - 1] = ',';
                p.arg = arr->elem + arr->elemsize * i;
                check_kparam_locked(p.mod);
                ret = arr->ops->get(buffer + off, &p);
                if (ret < 0)
                        return ret;
                off += ret;
        }
        buffer[off] = '\0';
        return off;
}

static void param_array_free(void *arg)
{
        unsigned int i;
        const struct kparam_array *arr = arg;

        if (arr->ops->free)
                for (i = 0; i < (arr->num ? *arr->num : arr->max); i++)
                        arr->ops->free(arr->elem + arr->elemsize * i);
}

const struct kernel_param_ops param_array_ops = {
        .set = param_array_set,
        .get = param_array_get,
        .free = param_array_free,
};
EXPORT_SYMBOL(param_array_ops);

int param_set_copystring(const char *val, const struct kernel_param *kp)
{
        const struct kparam_string *kps = kp->str;
        const size_t len = strnlen(val, kps->maxlen);

        if (len == kps->maxlen) {
                pr_err("%s: string doesn't fit in %u chars.\n",
                       kp->name, kps->maxlen-1);
                return -ENOSPC;
        }
        memcpy(kps->string, val, len + 1);
        return 0;
}
EXPORT_SYMBOL(param_set_copystring);

int param_get_string(char *buffer, const struct kernel_param *kp)
{
        const struct kparam_string *kps = kp->str;
        return scnprintf(buffer, PAGE_SIZE, "%s\n", kps->string);
}
EXPORT_SYMBOL(param_get_string);

const struct kernel_param_ops param_ops_string = {
        .set = param_set_copystring,
        .get = param_get_string,
};
EXPORT_SYMBOL(param_ops_string);

/* sysfs output in /sys/modules/XYZ/parameters/ */
#define to_module_attr(n) container_of_const(n, struct module_attribute, attr)
#define to_module_kobject(n) container_of(n, struct module_kobject, kobj)

struct param_attribute
{
        struct module_attribute mattr;
        const struct kernel_param *param;
};

struct module_param_attrs
{
        unsigned int num;
        struct attribute_group grp;
        struct param_attribute attrs[] __counted_by(num);
};

#ifdef CONFIG_SYSFS
#define to_param_attr(n) container_of_const(n, struct param_attribute, mattr)

static ssize_t param_attr_show(const struct module_attribute *mattr,
                               struct module_kobject *mk, char *buf)
{
        int count;
        const struct param_attribute *attribute = to_param_attr(mattr);

        if (!attribute->param->ops->get)
                return -EPERM;

        kernel_param_lock(mk->mod);
        count = attribute->param->ops->get(buf, attribute->param);
        kernel_param_unlock(mk->mod);
        return count;
}

/* sysfs always hands a nul-terminated string in buf.  We rely on that. */
static ssize_t param_attr_store(const struct module_attribute *mattr,
                                struct module_kobject *mk,
                                const char *buf, size_t len)
{
        int err;
        const struct param_attribute *attribute = to_param_attr(mattr);

        if (!attribute->param->ops->set)
                return -EPERM;

        kernel_param_lock(mk->mod);
        if (param_check_unsafe(attribute->param))
                err = attribute->param->ops->set(buf, attribute->param);
        else
                err = -EPERM;
        kernel_param_unlock(mk->mod);
        if (!err)
                return len;
        return err;
}
#endif

#ifdef CONFIG_SYSFS
void kernel_param_lock(struct module *mod)
{
        mutex_lock(KPARAM_MUTEX(mod));
}

void kernel_param_unlock(struct module *mod)
{
        mutex_unlock(KPARAM_MUTEX(mod));
}

EXPORT_SYMBOL(kernel_param_lock);
EXPORT_SYMBOL(kernel_param_unlock);

/*
 * add_sysfs_param - add a parameter to sysfs
 * @mk: struct module_kobject
 * @kp: the actual parameter definition to add to sysfs
 * @name: name of parameter
 *
 * Create a kobject if for a (per-module) parameter if mp NULL, and
 * create file in sysfs.  Returns an error on out of memory.  Always cleans up
 * if there's an error.
 */
static __init_or_module int add_sysfs_param(struct module_kobject *mk,
                                            const struct kernel_param *kp,
                                            const char *name)
{
        struct module_param_attrs *new_mp;
        struct attribute **new_attrs;
        unsigned int i;

        /* We don't bother calling this with invisible parameters. */
        BUG_ON(!kp->perm);

        if (!mk->mp) {
                /* First allocation. */
                mk->mp = kzalloc_obj(*mk->mp);
                if (!mk->mp)
                        return -ENOMEM;
                mk->mp->grp.name = "parameters";
                /* NULL-terminated attribute array. */
                mk->mp->grp.attrs = kzalloc_obj(mk->mp->grp.attrs[0]);
                /* Caller will cleanup via free_module_param_attrs */
                if (!mk->mp->grp.attrs)
                        return -ENOMEM;
        }

        /* Enlarge allocations. */
        new_mp = krealloc(mk->mp, struct_size(mk->mp, attrs, mk->mp->num + 1),
                          GFP_KERNEL);
        if (!new_mp)
                return -ENOMEM;
        mk->mp = new_mp;
        mk->mp->num++;

        /* Extra pointer for NULL terminator */
        new_attrs = krealloc_array(mk->mp->grp.attrs, mk->mp->num + 1,
                                   sizeof(mk->mp->grp.attrs[0]), GFP_KERNEL);
        if (!new_attrs)
                return -ENOMEM;
        mk->mp->grp.attrs = new_attrs;

        /* Tack new one on the end. */
        memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
        sysfs_attr_init(&mk->mp->attrs[mk->mp->num - 1].mattr.attr);
        mk->mp->attrs[mk->mp->num - 1].param = kp;
        mk->mp->attrs[mk->mp->num - 1].mattr.show = param_attr_show;
        /* Do not allow runtime DAC changes to make param writable. */
        if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
                mk->mp->attrs[mk->mp->num - 1].mattr.store = param_attr_store;
        else
                mk->mp->attrs[mk->mp->num - 1].mattr.store = NULL;
        mk->mp->attrs[mk->mp->num - 1].mattr.attr.name = (char *)name;
        mk->mp->attrs[mk->mp->num - 1].mattr.attr.mode = kp->perm;

        /* Fix up all the pointers, since krealloc can move us */
        for (i = 0; i < mk->mp->num; i++)
                mk->mp->grp.attrs[i] = &mk->mp->attrs[i].mattr.attr;
        mk->mp->grp.attrs[mk->mp->num] = NULL;
        return 0;
}

#ifdef CONFIG_MODULES
static void free_module_param_attrs(struct module_kobject *mk)
{
        if (mk->mp)
                kfree(mk->mp->grp.attrs);
        kfree(mk->mp);
        mk->mp = NULL;
}

/*
 * module_param_sysfs_setup - setup sysfs support for one module
 * @mod: module
 * @kparam: module parameters (array)
 * @num_params: number of module parameters
 *
 * Adds sysfs entries for module parameters under
 * /sys/module/[mod->name]/parameters/
 */
int module_param_sysfs_setup(struct module *mod,
                             const struct kernel_param *kparam,
                             unsigned int num_params)
{
        int i, err;
        bool params = false;

        for (i = 0; i < num_params; i++) {
                if (kparam[i].perm == 0)
                        continue;
                err = add_sysfs_param(&mod->mkobj, &kparam[i], kparam[i].name);
                if (err) {
                        free_module_param_attrs(&mod->mkobj);
                        return err;
                }
                params = true;
        }

        if (!params)
                return 0;

        /* Create the param group. */
        err = sysfs_create_group(&mod->mkobj.kobj, &mod->mkobj.mp->grp);
        if (err)
                free_module_param_attrs(&mod->mkobj);
        return err;
}

/*
 * module_param_sysfs_remove - remove sysfs support for one module
 * @mod: module
 *
 * Remove sysfs entries for module parameters and the corresponding
 * kobject.
 */
void module_param_sysfs_remove(struct module *mod)
{
        if (mod->mkobj.mp) {
                sysfs_remove_group(&mod->mkobj.kobj, &mod->mkobj.mp->grp);
                /*
                 * We are positive that no one is using any param
                 * attrs at this point. Deallocate immediately.
                 */
                free_module_param_attrs(&mod->mkobj);
        }
}
#endif

void destroy_params(const struct kernel_param *params, unsigned num)
{
        unsigned int i;

        for (i = 0; i < num; i++)
                if (params[i].ops->free)
                        params[i].ops->free(params[i].arg);
}

struct module_kobject * __init_or_module
lookup_or_create_module_kobject(const char *name)
{
        struct module_kobject *mk;
        struct kobject *kobj;
        int err;

        kobj = kset_find_obj(module_kset, name);
        if (kobj)
                return to_module_kobject(kobj);

        mk = kzalloc_obj(struct module_kobject);
        if (!mk)
                return NULL;

        mk->mod = THIS_MODULE;
        mk->kobj.kset = module_kset;
        err = kobject_init_and_add(&mk->kobj, &module_ktype, NULL, "%s", name);
        if (IS_ENABLED(CONFIG_MODULES) && !err)
                err = sysfs_create_file(&mk->kobj, &module_uevent.attr);
        if (err) {
                kobject_put(&mk->kobj);
                pr_crit("Adding module '%s' to sysfs failed (%d), the system may be unstable.\n",
                        name, err);
                return NULL;
        }

        /* So that we hold reference in both cases. */
        kobject_get(&mk->kobj);

        return mk;
}

static void __init kernel_add_sysfs_param(const char *name,
                                          const struct kernel_param *kparam,
                                          unsigned int name_skip)
{
        struct module_kobject *mk;
        int err;

        mk = lookup_or_create_module_kobject(name);
        if (!mk)
                return;

        /* We need to remove old parameters before adding more. */
        if (mk->mp)
                sysfs_remove_group(&mk->kobj, &mk->mp->grp);

        /* These should not fail at boot. */
        err = add_sysfs_param(mk, kparam, kparam->name + name_skip);
        BUG_ON(err);
        err = sysfs_create_group(&mk->kobj, &mk->mp->grp);
        BUG_ON(err);
        kobject_uevent(&mk->kobj, KOBJ_ADD);
        kobject_put(&mk->kobj);
}

/*
 * param_sysfs_builtin - add sysfs parameters for built-in modules
 *
 * Add module_parameters to sysfs for "modules" built into the kernel.
 *
 * The "module" name (KBUILD_MODNAME) is stored before a dot, the
 * "parameter" name is stored behind a dot in kernel_param->name. So,
 * extract the "module" name for all built-in kernel_param-eters,
 * and for all who have the same, call kernel_add_sysfs_param.
 */
static void __init param_sysfs_builtin(void)
{
        const struct kernel_param *kp;
        unsigned int name_len;
        char modname[MODULE_NAME_LEN];

        for (kp = __start___param; kp < __stop___param; kp++) {
                char *dot;

                if (kp->perm == 0)
                        continue;

                dot = strchr(kp->name, '.');
                if (!dot) {
                        /* This happens for core_param() */
                        strscpy(modname, "kernel");
                        name_len = 0;
                } else {
                        name_len = dot - kp->name + 1;
                        strscpy(modname, kp->name, name_len);
                }
                kernel_add_sysfs_param(modname, kp, name_len);
        }
}

ssize_t __modver_version_show(const struct module_attribute *mattr,
                              struct module_kobject *mk, char *buf)
{
        const struct module_version_attribute *vattr =
                container_of_const(mattr, struct module_version_attribute, mattr);

        return scnprintf(buf, PAGE_SIZE, "%s\n", vattr->version);
}

extern const struct module_version_attribute __start___modver[];
extern const struct module_version_attribute __stop___modver[];

static void __init version_sysfs_builtin(void)
{
        const struct module_version_attribute *vattr;
        struct module_kobject *mk;
        int err;

        for (vattr = __start___modver; vattr < __stop___modver; vattr++) {
                mk = lookup_or_create_module_kobject(vattr->module_name);
                if (mk) {
                        err = sysfs_create_file(&mk->kobj, &vattr->mattr.attr);
                        WARN_ON_ONCE(err);
                        kobject_uevent(&mk->kobj, KOBJ_ADD);
                        kobject_put(&mk->kobj);
                }
        }
}

/* module-related sysfs stuff */

static ssize_t module_attr_show(struct kobject *kobj,
                                struct attribute *attr,
                                char *buf)
{
        const struct module_attribute *attribute;
        struct module_kobject *mk;
        int ret;

        attribute = to_module_attr(attr);
        mk = to_module_kobject(kobj);

        if (!attribute->show)
                return -EIO;

        ret = attribute->show(attribute, mk, buf);

        return ret;
}

static ssize_t module_attr_store(struct kobject *kobj,
                                struct attribute *attr,
                                const char *buf, size_t len)
{
        const struct module_attribute *attribute;
        struct module_kobject *mk;
        int ret;

        attribute = to_module_attr(attr);
        mk = to_module_kobject(kobj);

        if (!attribute->store)
                return -EIO;

        ret = attribute->store(attribute, mk, buf, len);

        return ret;
}

static const struct sysfs_ops module_sysfs_ops = {
        .show = module_attr_show,
        .store = module_attr_store,
};

static int uevent_filter(const struct kobject *kobj)
{
        const struct kobj_type *ktype = get_ktype(kobj);

        if (ktype == &module_ktype)
                return 1;
        return 0;
}

static const struct kset_uevent_ops module_uevent_ops = {
        .filter = uevent_filter,
};

struct kset *module_kset;

static void module_kobj_release(struct kobject *kobj)
{
        struct module_kobject *mk = to_module_kobject(kobj);

        if (mk->kobj_completion)
                complete(mk->kobj_completion);
}

const struct kobj_type module_ktype = {
        .release   =    module_kobj_release,
        .sysfs_ops =    &module_sysfs_ops,
};

/*
 * param_sysfs_init - create "module" kset
 *
 * This must be done before the initramfs is unpacked and
 * request_module() thus becomes possible, because otherwise the
 * module load would fail in mod_sysfs_init.
 */
static int __init param_sysfs_init(void)
{
        module_kset = kset_create_and_add("module", &module_uevent_ops, NULL);
        if (!module_kset) {
                printk(KERN_WARNING "%s (%d): error creating kset\n",
                        __FILE__, __LINE__);
                return -ENOMEM;
        }

        return 0;
}
subsys_initcall(param_sysfs_init);

/*
 * param_sysfs_builtin_init - add sysfs version and parameter
 * attributes for built-in modules
 */
static int __init param_sysfs_builtin_init(void)
{
        if (!module_kset)
                return -ENOMEM;

        version_sysfs_builtin();
        param_sysfs_builtin();

        return 0;
}
late_initcall(param_sysfs_builtin_init);

#endif /* CONFIG_SYSFS */