root/kernel/utsname_sysctl.c

DEFINITIONS

1. get_uts
2. put_uts
3. proc_do_uts_string
4. sysctl_uts_string
5. utsname_sysctl_init

/*
 *  Copyright (C) 2007
 *
 *  Author: Eric Biederman <ebiederm@xmision.com>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation, version 2 of the
 *  License.
 */

#include <linux/module.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/sysctl.h>

static void *get_uts(ctl_table *table, int write)
{
        char *which = table->data;
        struct uts_namespace *uts_ns;

        uts_ns = current->nsproxy->uts_ns;
        which = (which - (char *)&init_uts_ns) + (char *)uts_ns;

        if (!write)
                down_read(&uts_sem);
        else
                down_write(&uts_sem);
        return which;
}

static void put_uts(ctl_table *table, int write, void *which)
{
        if (!write)
                up_read(&uts_sem);
        else
                up_write(&uts_sem);
}

#ifdef CONFIG_PROC_FS
/*
 *      Special case of dostring for the UTS structure. This has locks
 *      to observe. Should this be in kernel/sys.c ????
 */
static int proc_do_uts_string(ctl_table *table, int write, struct file *filp,
                  void __user *buffer, size_t *lenp, loff_t *ppos)
{
        struct ctl_table uts_table;
        int r;
        memcpy(&uts_table, table, sizeof(uts_table));
        uts_table.data = get_uts(table, write);
        r = proc_dostring(&uts_table,write,filp,buffer,lenp, ppos);
        put_uts(table, write, uts_table.data);
        return r;
}
#else
#define proc_do_uts_string NULL
#endif


#ifdef CONFIG_SYSCTL_SYSCALL
/* The generic string strategy routine: */
static int sysctl_uts_string(ctl_table *table, int __user *name, int nlen,
                  void __user *oldval, size_t __user *oldlenp,
                  void __user *newval, size_t newlen)
{
        struct ctl_table uts_table;
        int r, write;
        write = newval && newlen;
        memcpy(&uts_table, table, sizeof(uts_table));
        uts_table.data = get_uts(table, write);
        r = sysctl_string(&uts_table, name, nlen,
                oldval, oldlenp, newval, newlen);
        put_uts(table, write, uts_table.data);
        return r;
}
#else
#define sysctl_uts_string NULL
#endif

static struct ctl_table uts_kern_table[] = {
        {
                .ctl_name       = KERN_OSTYPE,
                .procname       = "ostype",
                .data           = init_uts_ns.name.sysname,
                .maxlen         = sizeof(init_uts_ns.name.sysname),
                .mode           = 0444,
                .proc_handler   = proc_do_uts_string,
                .strategy       = sysctl_uts_string,
        },
        {
                .ctl_name       = KERN_OSRELEASE,
                .procname       = "osrelease",
                .data           = init_uts_ns.name.release,
                .maxlen         = sizeof(init_uts_ns.name.release),
                .mode           = 0444,
                .proc_handler   = proc_do_uts_string,
                .strategy       = sysctl_uts_string,
        },
        {
                .ctl_name       = KERN_VERSION,
                .procname       = "version",
                .data           = init_uts_ns.name.version,
                .maxlen         = sizeof(init_uts_ns.name.version),
                .mode           = 0444,
                .proc_handler   = proc_do_uts_string,
                .strategy       = sysctl_uts_string,
        },
        {
                .ctl_name       = KERN_NODENAME,
                .procname       = "hostname",
                .data           = init_uts_ns.name.nodename,
                .maxlen         = sizeof(init_uts_ns.name.nodename),
                .mode           = 0644,
                .proc_handler   = proc_do_uts_string,
                .strategy       = sysctl_uts_string,
        },
        {
                .ctl_name       = KERN_DOMAINNAME,
                .procname       = "domainname",
                .data           = init_uts_ns.name.domainname,
                .maxlen         = sizeof(init_uts_ns.name.domainname),
                .mode           = 0644,
                .proc_handler   = proc_do_uts_string,
                .strategy       = sysctl_uts_string,
        },
        {}
};

static struct ctl_table uts_root_table[] = {
        {
                .ctl_name       = CTL_KERN,
                .procname       = "kernel",
                .mode           = 0555,
                .child          = uts_kern_table,
        },
        {}
};

static int __init utsname_sysctl_init(void)
{
        register_sysctl_table(uts_root_table);
        return 0;
}

__initcall(utsname_sysctl_init);