/*
 * sysctl.c: General linux system control interface
 *
 * Begun 24 March 1995, Stephen Tweedie
 * Added /proc support, Dec 1995
 * Added bdflush entry and intvec min/max checking, 2/23/96, Tom Dyas.
 * Added hooks for /proc/sys/net (minor, minor patch), 96/4/1, Mike Shaver.
 * Added kernel/java-{interpreter,appletviewer}, 96/5/10, Mike Shaver.
 * Dynamic registration fixes, Stephen Tweedie.
 * Added kswapd-interval, ctrl-alt-del, printk stuff, 1/8/97, Chris Horn.
 * Made sysctl support optional via CONFIG_SYSCTL, 1/10/97, Chris
 *  Horn.
 * Added proc_doulongvec_ms_jiffies_minmax, 09/08/99, Carlos H. Bauer.
 * Added proc_doulongvec_minmax, 09/08/99, Carlos H. Bauer.
 * Changed linked lists to use list.h instead of lists.h, 02/24/00, Bill
 *  Wendling.
 * The list_for_each() macro wasn't appropriate for the sysctl loop.
 *  Removed it and replaced it with older style, 03/23/00, Bill Wendling
 */

#include <linux/config.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/ctype.h>
#include <linux/utsname.h>
#include <linux/capability.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/sysrq.h>
#include <linux/highuid.h>
#include <linux/writeback.h>

#include <asm/uaccess.h>

#ifdef CONFIG_ROOT_NFS
#include <linux/nfs_fs.h>
#endif

#if defined(CONFIG_SYSCTL)

/* External variables not in a header file. */
extern int panic_timeout;
extern int C_A_D;
extern int sysctl_overcommit_memory;
extern int sysctl_overcommit_ratio;
extern int max_threads;
extern atomic_t nr_queued_signals;
extern int max_queued_signals;
extern int sysrq_enabled;
extern int core_uses_pid;
extern int cad_pid;
extern int pid_max;

/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
static int maxolduid = 65535;
static int minolduid;

#ifdef CONFIG_KMOD
extern char modprobe_path[];
#endif
#ifdef CONFIG_HOTPLUG
extern char hotplug_path[];
#endif
#ifdef CONFIG_CHR_DEV_SG
extern int sg_big_buff;
#endif
#ifdef CONFIG_SYSVIPC
extern size_t shm_ctlmax;
extern size_t shm_ctlall;
extern int shm_ctlmni;
extern int msg_ctlmax;
extern int msg_ctlmnb;
extern int msg_ctlmni;
extern int sem_ctls[];
#endif

#ifdef __sparc__
extern char reboot_command [];
extern int stop_a_enabled;
#endif

#ifdef CONFIG_ARCH_S390
#ifdef CONFIG_MATHEMU
extern int sysctl_ieee_emulation_warnings;
#endif
extern int sysctl_userprocess_debug;
#endif

#ifdef CONFIG_PPC32
extern unsigned long zero_paged_on, powersave_nap;
int proc_dol2crvec(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp);
#endif

#ifdef CONFIG_BSD_PROCESS_ACCT
extern int acct_parm[];
#endif

#ifdef CONFIG_HUGETLB_PAGE
extern int htlbpage_max;
extern int set_hugetlb_mem_size(int);
#endif

static int parse_table(int *, int, void *, size_t *, void *, size_t,
                       ctl_table *, void **);
static int proc_doutsstring(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp);

static ctl_table root_table[];
static struct ctl_table_header root_table_header =
        { root_table, LIST_HEAD_INIT(root_table_header.ctl_entry) };

static ctl_table kern_table[];
static ctl_table vm_table[];
#ifdef CONFIG_NET
extern ctl_table net_table[];
#endif
static ctl_table proc_table[];
static ctl_table fs_table[];
static ctl_table debug_table[];
static ctl_table dev_table[];
extern ctl_table random_table[];

/* /proc declarations: */

#ifdef CONFIG_PROC_FS

static ssize_t proc_readsys(struct file *, char *, size_t, loff_t *);
static ssize_t proc_writesys(struct file *, const char *, size_t, loff_t *);
static int proc_sys_permission(struct inode *, int);

struct file_operations proc_sys_file_operations = {
        .read           = proc_readsys,
        .write          = proc_writesys,
};

static struct inode_operations proc_sys_inode_operations = {
        .permission     = proc_sys_permission,
};

extern struct proc_dir_entry *proc_sys_root;

static void register_proc_table(ctl_table *, struct proc_dir_entry *);
static void unregister_proc_table(ctl_table *, struct proc_dir_entry *);
#endif

/* The default sysctl tables: */

static ctl_table root_table[] = {
        {CTL_KERN, "kernel", NULL, 0, 0555, kern_table},
        {CTL_VM, "vm", NULL, 0, 0555, vm_table},
#ifdef CONFIG_NET
        {CTL_NET, "net", NULL, 0, 0555, net_table},
#endif
        {CTL_PROC, "proc", NULL, 0, 0555, proc_table},
        {CTL_FS, "fs", NULL, 0, 0555, fs_table},
        {CTL_DEBUG, "debug", NULL, 0, 0555, debug_table},
        {CTL_DEV, "dev", NULL, 0, 0555, dev_table},
        {0}
};

static ctl_table kern_table[] = {
        {KERN_OSTYPE, "ostype", system_utsname.sysname, 64,
         0444, NULL, &proc_doutsstring, &sysctl_string},
        {KERN_OSRELEASE, "osrelease", system_utsname.release, 64,
         0444, NULL, &proc_doutsstring, &sysctl_string},
        {KERN_VERSION, "version", system_utsname.version, 64,
         0444, NULL, &proc_doutsstring, &sysctl_string},
        {KERN_NODENAME, "hostname", system_utsname.nodename, 64,
         0644, NULL, &proc_doutsstring, &sysctl_string},
        {KERN_DOMAINNAME, "domainname", system_utsname.domainname, 64,
         0644, NULL, &proc_doutsstring, &sysctl_string},
        {KERN_PANIC, "panic", &panic_timeout, sizeof(int),
         0644, NULL, &proc_dointvec},
        {KERN_CORE_USES_PID, "core_uses_pid", &core_uses_pid, sizeof(int),
         0644, NULL, &proc_dointvec},
        {KERN_TAINTED, "tainted", &tainted, sizeof(int),
         0644, NULL, &proc_dointvec},
        {KERN_CAP_BSET, "cap-bound", &cap_bset, sizeof(kernel_cap_t),
         0600, NULL, &proc_dointvec_bset},
#ifdef CONFIG_BLK_DEV_INITRD
        {KERN_REALROOTDEV, "real-root-dev", &real_root_dev, sizeof(int),
         0644, NULL, &proc_dointvec},
#endif
#ifdef __sparc__
        {KERN_SPARC_REBOOT, "reboot-cmd", reboot_command,
         256, 0644, NULL, &proc_dostring, &sysctl_string },
        {KERN_SPARC_STOP_A, "stop-a", &stop_a_enabled, sizeof (int),
         0644, NULL, &proc_dointvec},
#endif
#ifdef CONFIG_PPC32
        {KERN_PPC_ZEROPAGED, "zero-paged", &zero_paged_on, sizeof(int),
         0644, NULL, &proc_dointvec},
        {KERN_PPC_POWERSAVE_NAP, "powersave-nap", &powersave_nap, sizeof(int),
         0644, NULL, &proc_dointvec},
        {KERN_PPC_L2CR, "l2cr", NULL, 0,
         0644, NULL, &proc_dol2crvec},
#endif
        {KERN_CTLALTDEL, "ctrl-alt-del", &C_A_D, sizeof(int),
         0644, NULL, &proc_dointvec},
        {KERN_PRINTK, "printk", &console_loglevel, 4*sizeof(int),
         0644, NULL, &proc_dointvec},
#ifdef CONFIG_KMOD
        {KERN_MODPROBE, "modprobe", &modprobe_path, 256,
         0644, NULL, &proc_dostring, &sysctl_string },
#endif
#ifdef CONFIG_HOTPLUG
        {KERN_HOTPLUG, "hotplug", &hotplug_path, 256,
         0644, NULL, &proc_dostring, &sysctl_string },
#endif
#ifdef CONFIG_CHR_DEV_SG
        {KERN_SG_BIG_BUFF, "sg-big-buff", &sg_big_buff, sizeof (int),
         0444, NULL, &proc_dointvec},
#endif
#ifdef CONFIG_BSD_PROCESS_ACCT
        {KERN_ACCT, "acct", &acct_parm, 3*sizeof(int),
        0644, NULL, &proc_dointvec},
#endif
        {KERN_RTSIGNR, "rtsig-nr", &nr_queued_signals, sizeof(int),
         0444, NULL, &proc_dointvec},
        {KERN_RTSIGMAX, "rtsig-max", &max_queued_signals, sizeof(int),
         0644, NULL, &proc_dointvec},
#ifdef CONFIG_SYSVIPC
        {KERN_SHMMAX, "shmmax", &shm_ctlmax, sizeof (size_t),
         0644, NULL, &proc_doulongvec_minmax},
        {KERN_SHMALL, "shmall", &shm_ctlall, sizeof (size_t),
         0644, NULL, &proc_doulongvec_minmax},
        {KERN_SHMMNI, "shmmni", &shm_ctlmni, sizeof (int),
         0644, NULL, &proc_dointvec},
        {KERN_MSGMAX, "msgmax", &msg_ctlmax, sizeof (int),
         0644, NULL, &proc_dointvec},
        {KERN_MSGMNI, "msgmni", &msg_ctlmni, sizeof (int),
         0644, NULL, &proc_dointvec},
        {KERN_MSGMNB, "msgmnb", &msg_ctlmnb, sizeof (int),
         0644, NULL, &proc_dointvec},
        {KERN_SEM, "sem", &sem_ctls, 4*sizeof (int),
         0644, NULL, &proc_dointvec},
#endif
#ifdef CONFIG_MAGIC_SYSRQ
        {KERN_SYSRQ, "sysrq", &sysrq_enabled, sizeof (int),
         0644, NULL, &proc_dointvec},
#endif   
        {KERN_CADPID, "cad_pid", &cad_pid, sizeof (int),
         0600, NULL, &proc_dointvec},
        {KERN_MAX_THREADS, "threads-max", &max_threads, sizeof(int),
         0644, NULL, &proc_dointvec},
        {KERN_RANDOM, "random", NULL, 0, 0555, random_table},
        {KERN_OVERFLOWUID, "overflowuid", &overflowuid, sizeof(int), 0644, NULL,
         &proc_dointvec_minmax, &sysctl_intvec, NULL,
         &minolduid, &maxolduid},
        {KERN_OVERFLOWGID, "overflowgid", &overflowgid, sizeof(int), 0644, NULL,
         &proc_dointvec_minmax, &sysctl_intvec, NULL,
         &minolduid, &maxolduid},
#ifdef CONFIG_ARCH_S390
#ifdef CONFIG_MATHEMU
        {KERN_IEEE_EMULATION_WARNINGS,"ieee_emulation_warnings",
         &sysctl_ieee_emulation_warnings,sizeof(int),0644,NULL,&proc_dointvec},
#endif
        {KERN_S390_USER_DEBUG_LOGGING,"userprocess_debug",
         &sysctl_userprocess_debug,sizeof(int),0644,NULL,&proc_dointvec},
#endif
        {KERN_PIDMAX, "pid_max", &pid_max, sizeof (int),
         0600, NULL, &proc_dointvec},
        {0}
};

/* Constants for minimum and maximum testing in vm_table.
   We use these as one-element integer vectors. */
static int zero = 0;
static int one = 1;
static int one_hundred = 100;


static ctl_table vm_table[] = {
        {VM_OVERCOMMIT_MEMORY, "overcommit_memory", &sysctl_overcommit_memory,
         sizeof(sysctl_overcommit_memory), 0644, NULL, &proc_dointvec},
        {VM_OVERCOMMIT_RATIO, "overcommit_ratio",
         &sysctl_overcommit_ratio, sizeof(sysctl_overcommit_ratio), 0644,
         NULL, &proc_dointvec},
        {VM_PAGE_CLUSTER, "page-cluster", 
         &page_cluster, sizeof(int), 0644, NULL, &proc_dointvec},
        {VM_DIRTY_BACKGROUND, "dirty_background_ratio",
         &dirty_background_ratio, sizeof(dirty_background_ratio),
         0644, NULL, &proc_dointvec_minmax,  &sysctl_intvec, NULL,
         &zero, &one_hundred },
        {VM_DIRTY_ASYNC, "dirty_async_ratio", &dirty_async_ratio,
         sizeof(dirty_async_ratio), 0644, NULL, &proc_dointvec_minmax,
         &sysctl_intvec, NULL, &zero, &one_hundred },
        {VM_DIRTY_WB_CS, "dirty_writeback_centisecs",
         &dirty_writeback_centisecs, sizeof(dirty_writeback_centisecs), 0644,
         NULL, &proc_dointvec_minmax, &sysctl_intvec, NULL,
         /* Here, we define the range of possible values for
            dirty_writeback_centisecs.

            The default value is 5 seconds (500 centisec).  We will use 1
            centisec, the smallest possible value that could make any sort of
            sense.  If we allowed the user to set the interval to 0 seconds
            (which would presumably mean to chew up all of the CPU looking for
            dirty pages and writing them out, without taking a break), the
            interval would effectively become 1 second (100 centisecs), due to
            some nicely documented throttling code in wb_kupdate().

            There is no maximum legal value for dirty_writeback. */
         &one , NULL},
        {VM_DIRTY_EXPIRE_CS, "dirty_expire_centisecs",
         &dirty_expire_centisecs, sizeof(dirty_expire_centisecs), 0644,
         NULL, &proc_dointvec},
        { VM_NR_PDFLUSH_THREADS, "nr_pdflush_threads",
          &nr_pdflush_threads, sizeof nr_pdflush_threads,
          0444 /* read-only*/, NULL, &proc_dointvec},
#ifdef CONFIG_HUGETLB_PAGE
         {VM_HUGETLB_PAGES, "nr_hugepages", &htlbpage_max, sizeof(int), 0644, NULL, 
          &proc_dointvec},
#endif
        {0}
};

static ctl_table proc_table[] = {
        {0}
};

static ctl_table fs_table[] = {
        {FS_NRINODE, "inode-nr", &inodes_stat, 2*sizeof(int),
         0444, NULL, &proc_dointvec},
        {FS_STATINODE, "inode-state", &inodes_stat, 7*sizeof(int),
         0444, NULL, &proc_dointvec},
        {FS_NRFILE, "file-nr", &files_stat, 3*sizeof(int),
         0444, NULL, &proc_dointvec},
        {FS_MAXFILE, "file-max", &files_stat.max_files, sizeof(int),
         0644, NULL, &proc_dointvec},
        {FS_DENTRY, "dentry-state", &dentry_stat, 6*sizeof(int),
         0444, NULL, &proc_dointvec},
        {FS_OVERFLOWUID, "overflowuid", &fs_overflowuid, sizeof(int), 0644, NULL,
         &proc_dointvec_minmax, &sysctl_intvec, NULL,
         &minolduid, &maxolduid},
        {FS_OVERFLOWGID, "overflowgid", &fs_overflowgid, sizeof(int), 0644, NULL,
         &proc_dointvec_minmax, &sysctl_intvec, NULL,
         &minolduid, &maxolduid},
        {FS_LEASES, "leases-enable", &leases_enable, sizeof(int),
         0644, NULL, &proc_dointvec},
        {FS_DIR_NOTIFY, "dir-notify-enable", &dir_notify_enable,
         sizeof(int), 0644, NULL, &proc_dointvec},
        {FS_LEASE_TIME, "lease-break-time", &lease_break_time, sizeof(int),
         0644, NULL, &proc_dointvec},
        {0}
};

static ctl_table debug_table[] = {
        {0}
};

static ctl_table dev_table[] = {
        {0}
};  

extern void init_irq_proc (void);

void __init sysctl_init(void)
{
#ifdef CONFIG_PROC_FS
        register_proc_table(root_table, proc_sys_root);
        init_irq_proc();
#endif
}

int do_sysctl(int *name, int nlen, void *oldval, size_t *oldlenp,
               void *newval, size_t newlen)
{
        struct list_head *tmp;

        if (nlen <= 0 || nlen >= CTL_MAXNAME)
                return -ENOTDIR;
        if (oldval) {
                int old_len;
                if (!oldlenp || get_user(old_len, oldlenp))
                        return -EFAULT;
        }
        tmp = &root_table_header.ctl_entry;
        do {
                struct ctl_table_header *head =
                        list_entry(tmp, struct ctl_table_header, ctl_entry);
                void *context = NULL;
                int error = parse_table(name, nlen, oldval, oldlenp, 
                                        newval, newlen, head->ctl_table,
                                        &context);
                if (context)
                        kfree(context);
                if (error != -ENOTDIR)
                        return error;
                tmp = tmp->next;
        } while (tmp != &root_table_header.ctl_entry);
        return -ENOTDIR;
}

extern asmlinkage long sys_sysctl(struct __sysctl_args *args)
{
        struct __sysctl_args tmp;
        int error;

        if (copy_from_user(&tmp, args, sizeof(tmp)))
                return -EFAULT;
                
        lock_kernel();
        error = do_sysctl(tmp.name, tmp.nlen, tmp.oldval, tmp.oldlenp,
                          tmp.newval, tmp.newlen);
        unlock_kernel();
        return error;
}

/*
 * ctl_perm does NOT grant the superuser all rights automatically, because
 * some sysctl variables are readonly even to root.
 */

static int test_perm(int mode, int op)
{
        if (!current->euid)
                mode >>= 6;
        else if (in_egroup_p(0))
                mode >>= 3;
        if ((mode & op & 0007) == op)
                return 0;
        return -EACCES;
}

static inline int ctl_perm(ctl_table *table, int op)
{
        return test_perm(table->mode, op);
}

static int parse_table(int *name, int nlen,
                       void *oldval, size_t *oldlenp,
                       void *newval, size_t newlen,
                       ctl_table *table, void **context)
{
        int n;
repeat:
        if (!nlen)
                return -ENOTDIR;
        if (get_user(n, name))
                return -EFAULT;
        for ( ; table->ctl_name; table++) {
                if (n == table->ctl_name || table->ctl_name == CTL_ANY) {
                        int error;
                        if (table->child) {
                                if (ctl_perm(table, 001))
                                        return -EPERM;
                                if (table->strategy) {
                                        error = table->strategy(
                                                table, name, nlen,
                                                oldval, oldlenp,
                                                newval, newlen, context);
                                        if (error)
                                                return error;
                                }
                                name++;
                                nlen--;
                                table = table->child;
                                goto repeat;
                        }
                        error = do_sysctl_strategy(table, name, nlen,
                                                   oldval, oldlenp,
                                                   newval, newlen, context);
                        return error;
                }
        }
        return -ENOTDIR;
}

/* Perform the actual read/write of a sysctl table entry. */
int do_sysctl_strategy (ctl_table *table, 
                        int *name, int nlen,
                        void *oldval, size_t *oldlenp,
                        void *newval, size_t newlen, void **context)
{
        int op = 0, rc;
        size_t len;

        if (oldval)
                op |= 004;
        if (newval) 
                op |= 002;
        if (ctl_perm(table, op))
                return -EPERM;

        if (table->strategy) {
                rc = table->strategy(table, name, nlen, oldval, oldlenp,
                                     newval, newlen, context);
                if (rc < 0)
                        return rc;
                if (rc > 0)
                        return 0;
        }

        /* If there is no strategy routine, or if the strategy returns
         * zero, proceed with automatic r/w */
        if (table->data && table->maxlen) {
                if (oldval && oldlenp) {
                        get_user(len, oldlenp);
                        if (len) {
                                if (len > table->maxlen)
                                        len = table->maxlen;
                                if(copy_to_user(oldval, table->data, len))
                                        return -EFAULT;
                                if(put_user(len, oldlenp))
                                        return -EFAULT;
                        }
                }
                if (newval && newlen) {
                        len = newlen;
                        if (len > table->maxlen)
                                len = table->maxlen;
                        if(copy_from_user(table->data, newval, len))
                                return -EFAULT;
                }
        }
        return 0;
}

/**
 * register_sysctl_table - register a sysctl hierarchy
 * @table: the top-level table structure
 * @insert_at_head: whether the entry should be inserted in front or at the end
 *
 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
 * array. An entry with a ctl_name of 0 terminates the table. 
 *
 * The members of the &ctl_table structure are used as follows:
 *
 * ctl_name - This is the numeric sysctl value used by sysctl(2). The number
 *            must be unique within that level of sysctl
 *
 * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
 *            enter a sysctl file
 *
 * data - a pointer to data for use by proc_handler
 *
 * maxlen - the maximum size in bytes of the data
 *
 * mode - the file permissions for the /proc/sys file, and for sysctl(2)
 *
 * child - a pointer to the child sysctl table if this entry is a directory, or
 *         %NULL.
 *
 * proc_handler - the text handler routine (described below)
 *
 * strategy - the strategy routine (described below)
 *
 * de - for internal use by the sysctl routines
 *
 * extra1, extra2 - extra pointers usable by the proc handler routines
 *
 * Leaf nodes in the sysctl tree will be represented by a single file
 * under /proc; non-leaf nodes will be represented by directories.
 *
 * sysctl(2) can automatically manage read and write requests through
 * the sysctl table.  The data and maxlen fields of the ctl_table
 * struct enable minimal validation of the values being written to be
 * performed, and the mode field allows minimal authentication.
 *
 * More sophisticated management can be enabled by the provision of a
 * strategy routine with the table entry.  This will be called before
 * any automatic read or write of the data is performed.
 *
 * The strategy routine may return
 *
 * < 0 - Error occurred (error is passed to user process)
 *
 * 0   - OK - proceed with automatic read or write.
 *
 * > 0 - OK - read or write has been done by the strategy routine, so
 *       return immediately.
 *
 * There must be a proc_handler routine for any terminal nodes
 * mirrored under /proc/sys (non-terminals are handled by a built-in
 * directory handler).  Several default handlers are available to
 * cover common cases -
 *
 * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
 * proc_dointvec_minmax(), proc_doulongvec_ms_jiffies_minmax(),
 * proc_doulongvec_minmax()
 *
 * It is the handler's job to read the input buffer from user memory
 * and process it. The handler should return 0 on success.
 *
 * This routine returns %NULL on a failure to register, and a pointer
 * to the table header on success.
 */
struct ctl_table_header *register_sysctl_table(ctl_table * table, 
                                               int insert_at_head)
{
        struct ctl_table_header *tmp;
        tmp = kmalloc(sizeof(struct ctl_table_header), GFP_KERNEL);
        if (!tmp)
                return NULL;
        tmp->ctl_table = table;
        INIT_LIST_HEAD(&tmp->ctl_entry);
        if (insert_at_head)
                list_add(&tmp->ctl_entry, &root_table_header.ctl_entry);
        else
                list_add_tail(&tmp->ctl_entry, &root_table_header.ctl_entry);
#ifdef CONFIG_PROC_FS
        register_proc_table(table, proc_sys_root);
#endif
        return tmp;
}

/**
 * unregister_sysctl_table - unregister a sysctl table hierarchy
 * @header: the header returned from register_sysctl_table
 *
 * Unregisters the sysctl table and all children. proc entries may not
 * actually be removed until they are no longer used by anyone.
 */
void unregister_sysctl_table(struct ctl_table_header * header)
{
        list_del(&header->ctl_entry);
#ifdef CONFIG_PROC_FS
        unregister_proc_table(header->ctl_table, proc_sys_root);
#endif
        kfree(header);
}

/*
 * /proc/sys support
 */

#ifdef CONFIG_PROC_FS

/* Scan the sysctl entries in table and add them all into /proc */
static void register_proc_table(ctl_table * table, struct proc_dir_entry *root)
{
        struct proc_dir_entry *de;
        int len;
        mode_t mode;
        
        for (; table->ctl_name; table++) {
                /* Can't do anything without a proc name. */
                if (!table->procname)
                        continue;
                /* Maybe we can't do anything with it... */
                if (!table->proc_handler && !table->child) {
                        printk(KERN_WARNING "SYSCTL: Can't register %s\n",
                                table->procname);
                        continue;
                }

                len = strlen(table->procname);
                mode = table->mode;

                de = NULL;
                if (table->proc_handler)
                        mode |= S_IFREG;
                else {
                        mode |= S_IFDIR;
                        for (de = root->subdir; de; de = de->next) {
                                if (proc_match(len, table->procname, de))
                                        break;
                        }
                        /* If the subdir exists already, de is non-NULL */
                }

                if (!de) {
                        de = create_proc_entry(table->procname, mode, root);
                        if (!de)
                                continue;
                        de->data = (void *) table;
                        if (table->proc_handler) {
                                de->proc_fops = &proc_sys_file_operations;
                                de->proc_iops = &proc_sys_inode_operations;
                        }
                }
                table->de = de;
                if (de->mode & S_IFDIR)
                        register_proc_table(table->child, de);
        }
}

/*
 * Unregister a /proc sysctl table and any subdirectories.
 */
static void unregister_proc_table(ctl_table * table, struct proc_dir_entry *root)
{
        struct proc_dir_entry *de;
        for (; table->ctl_name; table++) {
                if (!(de = table->de))
                        continue;
                if (de->mode & S_IFDIR) {
                        if (!table->child) {
                                printk (KERN_ALERT "Help - malformed sysctl tree on free\n");
                                continue;
                        }
                        unregister_proc_table(table->child, de);

                        /* Don't unregister directories which still have entries.. */
                        if (de->subdir)
                                continue;
                }

                /* Don't unregister proc entries that are still being used.. */
                if (atomic_read(&de->count))
                        continue;

                table->de = NULL;
                remove_proc_entry(table->procname, root);
        }
}

static ssize_t do_rw_proc(int write, struct file * file, char * buf,
                          size_t count, loff_t *ppos)
{
        int op;
        struct proc_dir_entry *de;
        struct ctl_table *table;
        size_t res;
        ssize_t error;
        
        de = PDE(file->f_dentry->d_inode);
        if (!de || !de->data)
                return -ENOTDIR;
        table = (struct ctl_table *) de->data;
        if (!table || !table->proc_handler)
                return -ENOTDIR;
        op = (write ? 002 : 004);
        if (ctl_perm(table, op))
                return -EPERM;
        
        res = count;

        /*
         * FIXME: we need to pass on ppos to the handler.
         */

        error = (*table->proc_handler) (table, write, file, buf, &res);
        if (error)
                return error;
        return res;
}

static ssize_t proc_readsys(struct file * file, char * buf,
                            size_t count, loff_t *ppos)
{
        return do_rw_proc(0, file, buf, count, ppos);
}

static ssize_t proc_writesys(struct file * file, const char * buf,
                             size_t count, loff_t *ppos)
{
        return do_rw_proc(1, file, (char *) buf, count, ppos);
}

static int proc_sys_permission(struct inode *inode, int op)
{
        return test_perm(inode->i_mode, op);
}

/**
 * proc_dostring - read a string sysctl
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes a string from/to the user buffer. If the kernel
 * buffer provided is not large enough to hold the string, the
 * string is truncated. The copied string is %NULL-terminated.
 * If the string is being read by the user process, it is copied
 * and a newline '\n' is added. It is truncated if the buffer is
 * not large enough.
 *
 * Returns 0 on success.
 */
int proc_dostring(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp)
{
        size_t len;
        char *p, c;
        
        if (!table->data || !table->maxlen || !*lenp ||
            (filp->f_pos && !write)) {
                *lenp = 0;
                return 0;
        }
        
        if (write) {
                len = 0;
                p = buffer;
                while (len < *lenp) {
                        if(get_user(c, p++))
                                return -EFAULT;
                        if (c == 0 || c == '\n')
                                break;
                        len++;
                }
                if (len >= table->maxlen)
                        len = table->maxlen-1;
                if(copy_from_user(table->data, buffer, len))
                        return -EFAULT;
                ((char *) table->data)[len] = 0;
                filp->f_pos += *lenp;
        } else {
                len = strlen(table->data);
                if (len > table->maxlen)
                        len = table->maxlen;
                if (len > *lenp)
                        len = *lenp;
                if (len)
                        if(copy_to_user(buffer, table->data, len))
                                return -EFAULT;
                if (len < *lenp) {
                        if(put_user('\n', ((char *) buffer) + len))
                                return -EFAULT;
                        len++;
                }
                *lenp = len;
                filp->f_pos += len;
        }
        return 0;
}

/*
 *      Special case of dostring for the UTS structure. This has locks
 *      to observe. Should this be in kernel/sys.c ????
 */
 
static int proc_doutsstring(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp)
{
        int r;

        if (!write) {
                down_read(&uts_sem);
                r=proc_dostring(table,0,filp,buffer,lenp);
                up_read(&uts_sem);
        } else {
                down_write(&uts_sem);
                r=proc_dostring(table,1,filp,buffer,lenp);
                up_write(&uts_sem);
        }
        return r;
}

#define OP_SET  0
#define OP_AND  1
#define OP_OR   2
#define OP_MAX  3
#define OP_MIN  4

static int do_proc_dointvec(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp, int conv, int op)
{
        int *i, vleft, first=1, neg, val;
        size_t left, len;
        
        #define TMPBUFLEN 20
        char buf[TMPBUFLEN], *p;
        
        if (!table->data || !table->maxlen || !*lenp ||
            (filp->f_pos && !write)) {
                *lenp = 0;
                return 0;
        }
        
        i = (int *) table->data;
        vleft = table->maxlen / sizeof(int);
        left = *lenp;
        
        for (; left && vleft--; i++, first=0) {
                if (write) {
                        while (left) {
                                char c;
                                if(get_user(c,(char *) buffer))
                                        return -EFAULT;
                                if (!isspace(c))
                                        break;
                                left--;
                                ((char *) buffer)++;
                        }
                        if (!left)
                                break;
                        neg = 0;
                        len = left;
                        if (len > TMPBUFLEN-1)
                                len = TMPBUFLEN-1;
                        if(copy_from_user(buf, buffer, len))
                                return -EFAULT;
                        buf[len] = 0;
                        p = buf;
                        if (*p == '-' && left > 1) {
                                neg = 1;
                                left--, p++;
                        }
                        if (*p < '0' || *p > '9')
                                break;
                        val = simple_strtoul(p, &p, 0) * conv;
                        len = p-buf;
                        if ((len < left) && *p && !isspace(*p))
                                break;
                        if (neg)
                                val = -val;
                        buffer += len;
                        left -= len;
#ifdef CONFIG_HUGETLB_PAGE
                        if (i == &htlbpage_max)
                                val = set_hugetlb_mem_size(val);
#endif
                        switch(op) {
                        case OP_SET:    *i = val; break;
                        case OP_AND:    *i &= val; break;
                        case OP_OR:     *i |= val; break;
                        case OP_MAX:    if(*i < val)
                                                *i = val;
                                        break;
                        case OP_MIN:    if(*i > val)
                                                *i = val;
                                        break;
                        }
                } else {
                        p = buf;
                        if (!first)
                                *p++ = '\t';
                        sprintf(p, "%d", (*i) / conv);
                        len = strlen(buf);
                        if (len > left)
                                len = left;
                        if(copy_to_user(buffer, buf, len))
                                return -EFAULT;
                        left -= len;
                        buffer += len;
                }
        }

        if (!write && !first && left) {
                if(put_user('\n', (char *) buffer))
                        return -EFAULT;
                left--, buffer++;
        }
        if (write) {
                p = (char *) buffer;
                while (left) {
                        char c;
                        if(get_user(c, p++))
                                return -EFAULT;
                        if (!isspace(c))
                                break;
                        left--;
                }
        }
        if (write && first)
                return -EINVAL;
        *lenp -= left;
        filp->f_pos += *lenp;
        return 0;
}

/**
 * proc_dointvec - read a vector of integers
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
 * values from/to the user buffer, treated as an ASCII string. 
 *
 * Returns 0 on success.
 */
int proc_dointvec(ctl_table *table, int write, struct file *filp,
                     void *buffer, size_t *lenp)
{
    return do_proc_dointvec(table,write,filp,buffer,lenp,1,OP_SET);
}

/*
 *      init may raise the set.
 */
 
int proc_dointvec_bset(ctl_table *table, int write, struct file *filp,
                        void *buffer, size_t *lenp)
{
        if (!capable(CAP_SYS_MODULE)) {
                return -EPERM;
        }
        return do_proc_dointvec(table,write,filp,buffer,lenp,1,
                                (current->pid == 1) ? OP_SET : OP_AND);
}

/**
 * proc_dointvec_minmax - read a vector of integers with min/max values
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) integer

 * values from/to the user buffer, treated as an ASCII string.
 *
 * This routine will ensure the values are within the range specified by
 * table->extra1 (min) and table->extra2 (max).
 *
 * Returns 0 on success.
 */
int proc_dointvec_minmax(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp)
{
        int *i, *min, *max, vleft, first=1, neg, val;
        size_t len, left;
        #define TMPBUFLEN 20
        char buf[TMPBUFLEN], *p;
        
        if (!table->data || !table->maxlen || !*lenp ||
            (filp->f_pos && !write)) {
                *lenp = 0;
                return 0;
        }
        
        i = (int *) table->data;
        min = (int *) table->extra1;
        max = (int *) table->extra2;
        vleft = table->maxlen / sizeof(int);
        left = *lenp;
        
        for (; left && vleft--; i++, min++, max++, first=0) {
                if (write) {
                        while (left) {
                                char c;
                                if(get_user(c, (char *) buffer))
                                        return -EFAULT;
                                if (!isspace(c))
                                        break;
                                left--;
                                ((char *) buffer)++;
                        }
                        if (!left)
                                break;
                        neg = 0;
                        len = left;
                        if (len > TMPBUFLEN-1)
                                len = TMPBUFLEN-1;
                        if(copy_from_user(buf, buffer, len))
                                return -EFAULT;
                        buf[len] = 0;
                        p = buf;
                        if (*p == '-' && left > 1) {
                                neg = 1;
                                left--, p++;
                        }
                        if (*p < '0' || *p > '9')
                                break;
                        val = simple_strtoul(p, &p, 0);
                        len = p-buf;
                        if ((len < left) && *p && !isspace(*p))
                                break;
                        if (neg)
                                val = -val;
                        buffer += len;
                        left -= len;

                        if ((min && val < *min) || (max && val > *max))
                                continue;
                        *i = val;
                } else {
                        p = buf;
                        if (!first)
                                *p++ = '\t';
                        sprintf(p, "%d", *i);
                        len = strlen(buf);
                        if (len > left)
                                len = left;
                        if(copy_to_user(buffer, buf, len))
                                return -EFAULT;
                        left -= len;
                        buffer += len;
                }
        }

        if (!write && !first && left) {
                if(put_user('\n', (char *) buffer))
                        return -EFAULT;
                left--, buffer++;
        }
        if (write) {
                p = (char *) buffer;
                while (left) {
                        char c;
                        if(get_user(c, p++))
                                return -EFAULT;
                        if (!isspace(c))
                                break;
                        left--;
                }
        }
        if (write && first)
                return -EINVAL;
        *lenp -= left;
        filp->f_pos += *lenp;
        return 0;
}

static int do_proc_doulongvec_minmax(ctl_table *table, int write,
                                     struct file *filp,
                                     void *buffer, size_t *lenp,
                                     unsigned long convmul,
                                     unsigned long convdiv)
{
#define TMPBUFLEN 20
        unsigned long *i, *min, *max, val;
        int vleft, first=1, neg;
        size_t len, left;
        char buf[TMPBUFLEN], *p;
        
        if (!table->data || !table->maxlen || !*lenp ||
            (filp->f_pos && !write)) {
                *lenp = 0;
                return 0;
        }
        
        i = (unsigned long *) table->data;
        min = (unsigned long *) table->extra1;
        max = (unsigned long *) table->extra2;
        vleft = table->maxlen / sizeof(unsigned long);
        left = *lenp;
        
        for (; left && vleft--; i++, min++, max++, first=0) {
                if (write) {
                        while (left) {
                                char c;
                                if(get_user(c, (char *) buffer))
                                        return -EFAULT;
                                if (!isspace(c))
                                        break;
                                left--;
                                ((char *) buffer)++;
                        }
                        if (!left)
                                break;
                        neg = 0;
                        len = left;
                        if (len > TMPBUFLEN-1)
                                len = TMPBUFLEN-1;
                        if(copy_from_user(buf, buffer, len))
                                return -EFAULT;
                        buf[len] = 0;
                        p = buf;
                        if (*p == '-' && left > 1) {
                                neg = 1;
                                left--, p++;
                        }
                        if (*p < '0' || *p > '9')
                                break;
                        val = simple_strtoul(p, &p, 0) * convmul / convdiv ;
                        len = p-buf;
                        if ((len < left) && *p && !isspace(*p))
                                break;
                        if (neg)
                                val = -val;
                        buffer += len;
                        left -= len;

                        if(neg)
                                continue;
                        if ((min && val < *min) || (max && val > *max))
                                continue;
                        *i = val;
                } else {
                        p = buf;
                        if (!first)
                                *p++ = '\t';
                        sprintf(p, "%lu", convdiv * (*i) / convmul);
                        len = strlen(buf);
                        if (len > left)
                                len = left;
                        if(copy_to_user(buffer, buf, len))
                                return -EFAULT;
                        left -= len;
                        buffer += len;
                }
        }

        if (!write && !first && left) {
                if(put_user('\n', (char *) buffer))
                        return -EFAULT;
                left--, buffer++;
        }
        if (write) {
                p = (char *) buffer;
                while (left) {
                        char c;
                        if(get_user(c, p++))
                                return -EFAULT;
                        if (!isspace(c))
                                break;
                        left--;
                }
        }
        if (write && first)
                return -EINVAL;
        *lenp -= left;
        filp->f_pos += *lenp;
        return 0;
#undef TMPBUFLEN
}

/**
 * proc_doulongvec_minmax - read a vector of long integers with min/max values
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned long) unsigned long
 * values from/to the user buffer, treated as an ASCII string.
 *
 * This routine will ensure the values are within the range specified by
 * table->extra1 (min) and table->extra2 (max).
 *
 * Returns 0 on success.
 */
int proc_doulongvec_minmax(ctl_table *table, int write, struct file *filp,
                           void *buffer, size_t *lenp)
{
    return do_proc_doulongvec_minmax(table, write, filp, buffer, lenp, 1l, 1l);
}

/**
 * proc_doulongvec_ms_jiffies_minmax - read a vector of millisecond values with min/max values
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned long) unsigned long
 * values from/to the user buffer, treated as an ASCII string. The values
 * are treated as milliseconds, and converted to jiffies when they are stored.
 *
 * This routine will ensure the values are within the range specified by
 * table->extra1 (min) and table->extra2 (max).
 *
 * Returns 0 on success.
 */
int proc_doulongvec_ms_jiffies_minmax(ctl_table *table, int write,
                                      struct file *filp,
                                      void *buffer, size_t *lenp)
{
    return do_proc_doulongvec_minmax(table, write, filp, buffer,
                                     lenp, HZ, 1000l);
}


/**
 * proc_dointvec_jiffies - read a vector of integers as seconds
 * @table: the sysctl table
 * @write: %TRUE if this is a write to the sysctl file
 * @filp: the file structure
 * @buffer: the user buffer
 * @lenp: the size of the user buffer
 *
 * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
 * values from/to the user buffer, treated as an ASCII string. 
 * The values read are assumed to be in seconds, and are converted into
 * jiffies.
 *
 * Returns 0 on success.
 */
int proc_dointvec_jiffies(ctl_table *table, int write, struct file *filp,
                          void *buffer, size_t *lenp)
{
    return do_proc_dointvec(table,write,filp,buffer,lenp,HZ,OP_SET);
}

#else /* CONFIG_PROC_FS */

int proc_dostring(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

static int proc_doutsstring(ctl_table *table, int write, struct file *filp,
                            void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec_bset(ctl_table *table, int write, struct file *filp,
                        void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec_minmax(ctl_table *table, int write, struct file *filp,
                    void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec_jiffies(ctl_table *table, int write, struct file *filp,
                    void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_doulongvec_minmax(ctl_table *table, int write, struct file *filp,
                    void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_doulongvec_ms_jiffies_minmax(ctl_table *table, int write,
                                      struct file *filp,
                                      void *buffer, size_t *lenp)
{
    return -ENOSYS;
}


#endif /* CONFIG_PROC_FS */


/*
 * General sysctl support routines 
 */

/* The generic string strategy routine: */
int sysctl_string(ctl_table *table, int *name, int nlen,
                  void *oldval, size_t *oldlenp,
                  void *newval, size_t newlen, void **context)
{
        size_t l, len;
        
        if (!table->data || !table->maxlen) 
                return -ENOTDIR;
        
        if (oldval && oldlenp) {
                if(get_user(len, oldlenp))
                        return -EFAULT;
                if (len) {
                        l = strlen(table->data);
                        if (len > l) len = l;
                        if (len >= table->maxlen)
                                len = table->maxlen;
                        if(copy_to_user(oldval, table->data, len))
                                return -EFAULT;
                        if(put_user(0, ((char *) oldval) + len))
                                return -EFAULT;
                        if(put_user(len, oldlenp))
                                return -EFAULT;
                }
        }
        if (newval && newlen) {
                len = newlen;
                if (len > table->maxlen)
                        len = table->maxlen;
                if(copy_from_user(table->data, newval, len))
                        return -EFAULT;
                if (len == table->maxlen)
                        len--;
                ((char *) table->data)[len] = 0;
        }
        return 0;
}

/*
 * This function makes sure that all of the integers in the vector
 * are between the minimum and maximum values given in the arrays
 * table->extra1 and table->extra2, respectively.
 */
int sysctl_intvec(ctl_table *table, int *name, int nlen,
                void *oldval, size_t *oldlenp,
                void *newval, size_t newlen, void **context)
{
        int i, *vec, *min, *max;
        size_t length;

        if (newval && newlen) {
                if (newlen % sizeof(int) != 0)
                        return -EINVAL;

                if (!table->extra1 && !table->extra2)
                        return 0;

                if (newlen > table->maxlen)
                        newlen = table->maxlen;
                length = newlen / sizeof(int);

                vec = (int *) newval;
                min = (int *) table->extra1;
                max = (int *) table->extra2;

                for (i = 0; i < length; i++) {
                        int value;
                        get_user(value, vec + i);
                        if (min && value < min[i])
                                return -EINVAL;
                        if (max && value > max[i])
                                return -EINVAL;
                }
        }
        return 0;
}

/* Strategy function to convert jiffies to seconds */ 
int sysctl_jiffies(ctl_table *table, int *name, int nlen,
                void *oldval, size_t *oldlenp,
                void *newval, size_t newlen, void **context)
{
        if (oldval) {
                size_t olen;
                if (oldlenp) { 
                        if (get_user(olen, oldlenp))
                                return -EFAULT;
                        if (olen!=sizeof(int))
                                return -EINVAL; 
                }
                if (put_user(*(int *)(table->data) / HZ, (int *)oldval) || 
                    (oldlenp && put_user(sizeof(int),oldlenp)))
                        return -EFAULT;
        }
        if (newval && newlen) { 
                int new;
                if (newlen != sizeof(int))
                        return -EINVAL; 
                if (get_user(new, (int *)newval))
                        return -EFAULT;
                *(int *)(table->data) = new*HZ; 
        }
        return 1;
}


#else /* CONFIG_SYSCTL */


extern asmlinkage long sys_sysctl(struct __sysctl_args *args)
{
        return -ENOSYS;
}

int sysctl_string(ctl_table *table, int *name, int nlen,
                  void *oldval, size_t *oldlenp,
                  void *newval, size_t newlen, void **context)
{
        return -ENOSYS;
}

int sysctl_intvec(ctl_table *table, int *name, int nlen,
                void *oldval, size_t *oldlenp,
                void *newval, size_t newlen, void **context)
{
        return -ENOSYS;
}

int sysctl_jiffies(ctl_table *table, int *name, int nlen,
                void *oldval, size_t *oldlenp,
                void *newval, size_t newlen, void **context)
{
        return -ENOSYS;
}

int proc_dostring(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec(ctl_table *table, int write, struct file *filp,
                  void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec_bset(ctl_table *table, int write, struct file *filp,
                        void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec_minmax(ctl_table *table, int write, struct file *filp,
                    void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_dointvec_jiffies(ctl_table *table, int write, struct file *filp,
                          void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_doulongvec_minmax(ctl_table *table, int write, struct file *filp,
                    void *buffer, size_t *lenp)
{
        return -ENOSYS;
}

int proc_doulongvec_ms_jiffies_minmax(ctl_table *table, int write,
                                      struct file *filp,
                                      void *buffer, size_t *lenp)
{
    return -ENOSYS;
}

struct ctl_table_header * register_sysctl_table(ctl_table * table, 
                                                int insert_at_head)
{
        return 0;
}

void unregister_sysctl_table(struct ctl_table_header * table)
{
}

#endif /* CONFIG_SYSCTL */