/*
 *  linux/kernel/sys.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/utsname.h>
#include <linux/mman.h>
#include <linux/smp_lock.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/prctl.h>
#include <linux/highuid.h>
#include <linux/fs.h>
#include <linux/perf_event.h>
#include <linux/resource.h>
#include <linux/kernel.h>
#include <linux/kexec.h>
#include <linux/workqueue.h>
#include <linux/capability.h>
#include <linux/device.h>
#include <linux/key.h>
#include <linux/times.h>
#include <linux/posix-timers.h>
#include <linux/security.h>
#include <linux/dcookies.h>
#include <linux/suspend.h>
#include <linux/tty.h>
#include <linux/signal.h>
#include <linux/cn_proc.h>
#include <linux/getcpu.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/seccomp.h>
#include <linux/cpu.h>
#include <linux/ptrace.h>
#include <linux/fs_struct.h>

#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/kprobes.h>
#include <linux/user_namespace.h>

#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/unistd.h>

#ifndef SET_UNALIGN_CTL
# define SET_UNALIGN_CTL(a,b)   (-EINVAL)
#endif
#ifndef GET_UNALIGN_CTL
# define GET_UNALIGN_CTL(a,b)   (-EINVAL)
#endif
#ifndef SET_FPEMU_CTL
# define SET_FPEMU_CTL(a,b)     (-EINVAL)
#endif
#ifndef GET_FPEMU_CTL
# define GET_FPEMU_CTL(a,b)     (-EINVAL)
#endif
#ifndef SET_FPEXC_CTL
# define SET_FPEXC_CTL(a,b)     (-EINVAL)
#endif
#ifndef GET_FPEXC_CTL
# define GET_FPEXC_CTL(a,b)     (-EINVAL)
#endif
#ifndef GET_ENDIAN
# define GET_ENDIAN(a,b)        (-EINVAL)
#endif
#ifndef SET_ENDIAN
# define SET_ENDIAN(a,b)        (-EINVAL)
#endif
#ifndef GET_TSC_CTL
# define GET_TSC_CTL(a)         (-EINVAL)
#endif
#ifndef SET_TSC_CTL
# define SET_TSC_CTL(a)         (-EINVAL)
#endif

/*
 * this is where the system-wide overflow UID and GID are defined, for
 * architectures that now have 32-bit UID/GID but didn't in the past
 */

int overflowuid = DEFAULT_OVERFLOWUID;
int overflowgid = DEFAULT_OVERFLOWGID;

#ifdef CONFIG_UID16
EXPORT_SYMBOL(overflowuid);
EXPORT_SYMBOL(overflowgid);
#endif

/*
 * the same as above, but for filesystems which can only store a 16-bit
 * UID and GID. as such, this is needed on all architectures
 */

int fs_overflowuid = DEFAULT_FS_OVERFLOWUID;
int fs_overflowgid = DEFAULT_FS_OVERFLOWUID;

EXPORT_SYMBOL(fs_overflowuid);
EXPORT_SYMBOL(fs_overflowgid);

/*
 * this indicates whether you can reboot with ctrl-alt-del: the default is yes
 */

int C_A_D = 1;
struct pid *cad_pid;
EXPORT_SYMBOL(cad_pid);

/*
 * If set, this is used for preparing the system to power off.
 */

void (*pm_power_off_prepare)(void);

/*
 * set the priority of a task
 * - the caller must hold the RCU read lock
 */
static int set_one_prio(struct task_struct *p, int niceval, int error)
{
        const struct cred *cred = current_cred(), *pcred = __task_cred(p);
        int no_nice;

        if (pcred->uid  != cred->euid &&
            pcred->euid != cred->euid && !capable(CAP_SYS_NICE)) {
                error = -EPERM;
                goto out;
        }
        if (niceval < task_nice(p) && !can_nice(p, niceval)) {
                error = -EACCES;
                goto out;
        }
        no_nice = security_task_setnice(p, niceval);
        if (no_nice) {
                error = no_nice;
                goto out;
        }
        if (error == -ESRCH)
                error = 0;
        set_user_nice(p, niceval);
out:
        return error;
}

SYSCALL_DEFINE3(setpriority, int, which, int, who, int, niceval)
{
        struct task_struct *g, *p;
        struct user_struct *user;
        const struct cred *cred = current_cred();
        int error = -EINVAL;
        struct pid *pgrp;

        if (which > PRIO_USER || which < PRIO_PROCESS)
                goto out;

        /* normalize: avoid signed division (rounding problems) */
        error = -ESRCH;
        if (niceval < -20)
                niceval = -20;
        if (niceval > 19)
                niceval = 19;

        read_lock(&tasklist_lock);
        switch (which) {
                case PRIO_PROCESS:
                        if (who)
                                p = find_task_by_vpid(who);
                        else
                                p = current;
                        if (p)
                                error = set_one_prio(p, niceval, error);
                        break;
                case PRIO_PGRP:
                        if (who)
                                pgrp = find_vpid(who);
                        else
                                pgrp = task_pgrp(current);
                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
                                error = set_one_prio(p, niceval, error);
                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
                        break;
                case PRIO_USER:
                        user = (struct user_struct *) cred->user;
                        if (!who)
                                who = cred->uid;
                        else if ((who != cred->uid) &&
                                 !(user = find_user(who)))
                                goto out_unlock;        /* No processes for this user */

                        do_each_thread(g, p)
                                if (__task_cred(p)->uid == who)
                                        error = set_one_prio(p, niceval, error);
                        while_each_thread(g, p);
                        if (who != cred->uid)
                                free_uid(user);         /* For find_user() */
                        break;
        }
out_unlock:
        read_unlock(&tasklist_lock);
out:
        return error;
}

/*
 * Ugh. To avoid negative return values, "getpriority()" will
 * not return the normal nice-value, but a negated value that
 * has been offset by 20 (ie it returns 40..1 instead of -20..19)
 * to stay compatible.
 */
SYSCALL_DEFINE2(getpriority, int, which, int, who)
{
        struct task_struct *g, *p;
        struct user_struct *user;
        const struct cred *cred = current_cred();
        long niceval, retval = -ESRCH;
        struct pid *pgrp;

        if (which > PRIO_USER || which < PRIO_PROCESS)
                return -EINVAL;

        read_lock(&tasklist_lock);
        switch (which) {
                case PRIO_PROCESS:
                        if (who)
                                p = find_task_by_vpid(who);
                        else
                                p = current;
                        if (p) {
                                niceval = 20 - task_nice(p);
                                if (niceval > retval)
                                        retval = niceval;
                        }
                        break;
                case PRIO_PGRP:
                        if (who)
                                pgrp = find_vpid(who);
                        else
                                pgrp = task_pgrp(current);
                        do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
                                niceval = 20 - task_nice(p);
                                if (niceval > retval)
                                        retval = niceval;
                        } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
                        break;
                case PRIO_USER:
                        user = (struct user_struct *) cred->user;
                        if (!who)
                                who = cred->uid;
                        else if ((who != cred->uid) &&
                                 !(user = find_user(who)))
                                goto out_unlock;        /* No processes for this user */

                        do_each_thread(g, p)
                                if (__task_cred(p)->uid == who) {
                                        niceval = 20 - task_nice(p);
                                        if (niceval > retval)
                                                retval = niceval;
                                }
                        while_each_thread(g, p);
                        if (who != cred->uid)
                                free_uid(user);         /* for find_user() */
                        break;
        }
out_unlock:
        read_unlock(&tasklist_lock);

        return retval;
}

/**
 *      emergency_restart - reboot the system
 *
 *      Without shutting down any hardware or taking any locks
 *      reboot the system.  This is called when we know we are in
 *      trouble so this is our best effort to reboot.  This is
 *      safe to call in interrupt context.
 */
void emergency_restart(void)
{
        machine_emergency_restart();
}
EXPORT_SYMBOL_GPL(emergency_restart);

void kernel_restart_prepare(char *cmd)
{
        blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
        system_state = SYSTEM_RESTART;
        device_shutdown();
        sysdev_shutdown();
}

/**
 *      kernel_restart - reboot the system
 *      @cmd: pointer to buffer containing command to execute for restart
 *              or %NULL
 *
 *      Shutdown everything and perform a clean reboot.
 *      This is not safe to call in interrupt context.
 */
void kernel_restart(char *cmd)
{
        kernel_restart_prepare(cmd);
        if (!cmd)
                printk(KERN_EMERG "Restarting system.\n");
        else
                printk(KERN_EMERG "Restarting system with command '%s'.\n", cmd);
        machine_restart(cmd);
}
EXPORT_SYMBOL_GPL(kernel_restart);

static void kernel_shutdown_prepare(enum system_states state)
{
        blocking_notifier_call_chain(&reboot_notifier_list,
                (state == SYSTEM_HALT)?SYS_HALT:SYS_POWER_OFF, NULL);
        system_state = state;
        device_shutdown();
}
/**
 *      kernel_halt - halt the system
 *
 *      Shutdown everything and perform a clean system halt.
 */
void kernel_halt(void)
{
        kernel_shutdown_prepare(SYSTEM_HALT);
        sysdev_shutdown();
        printk(KERN_EMERG "System halted.\n");
        machine_halt();
}

EXPORT_SYMBOL_GPL(kernel_halt);

/**
 *      kernel_power_off - power_off the system
 *
 *      Shutdown everything and perform a clean system power_off.
 */
void kernel_power_off(void)
{
        kernel_shutdown_prepare(SYSTEM_POWER_OFF);
        if (pm_power_off_prepare)
                pm_power_off_prepare();
        disable_nonboot_cpus();
        sysdev_shutdown();
        printk(KERN_EMERG "Power down.\n");
        machine_power_off();
}
EXPORT_SYMBOL_GPL(kernel_power_off);
/*
 * Reboot system call: for obvious reasons only root may call it,
 * and even root needs to set up some magic numbers in the registers
 * so that some mistake won't make this reboot the whole machine.
 * You can also set the meaning of the ctrl-alt-del-key here.
 *
 * reboot doesn't sync: do that yourself before calling this.
 */
SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
                void __user *, arg)
{
        char buffer[256];
        int ret = 0;

        /* We only trust the superuser with rebooting the system. */
        if (!capable(CAP_SYS_BOOT))
                return -EPERM;

        /* For safety, we require "magic" arguments. */
        if (magic1 != LINUX_REBOOT_MAGIC1 ||
            (magic2 != LINUX_REBOOT_MAGIC2 &&
                        magic2 != LINUX_REBOOT_MAGIC2A &&
                        magic2 != LINUX_REBOOT_MAGIC2B &&
                        magic2 != LINUX_REBOOT_MAGIC2C))
                return -EINVAL;

        /* Instead of trying to make the power_off code look like
         * halt when pm_power_off is not set do it the easy way.
         */
        if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
                cmd = LINUX_REBOOT_CMD_HALT;

        lock_kernel();
        switch (cmd) {
        case LINUX_REBOOT_CMD_RESTART:
                kernel_restart(NULL);
                break;

        case LINUX_REBOOT_CMD_CAD_ON:
                C_A_D = 1;
                break;

        case LINUX_REBOOT_CMD_CAD_OFF:
                C_A_D = 0;
                break;

        case LINUX_REBOOT_CMD_HALT:
                kernel_halt();
                unlock_kernel();
                do_exit(0);
                panic("cannot halt");

        case LINUX_REBOOT_CMD_POWER_OFF:
                kernel_power_off();
                unlock_kernel();
                do_exit(0);
                break;

        case LINUX_REBOOT_CMD_RESTART2:
                if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {
                        unlock_kernel();
                        return -EFAULT;
                }
                buffer[sizeof(buffer) - 1] = '\0';

                kernel_restart(buffer);
                break;

#ifdef CONFIG_KEXEC
        case LINUX_REBOOT_CMD_KEXEC:
                ret = kernel_kexec();
                break;
#endif

#ifdef CONFIG_HIBERNATION
        case LINUX_REBOOT_CMD_SW_SUSPEND:
                ret = hibernate();
                break;
#endif

        default:
                ret = -EINVAL;
                break;
        }
        unlock_kernel();
        return ret;
}

static void deferred_cad(struct work_struct *dummy)
{
        kernel_restart(NULL);
}

/*
 * This function gets called by ctrl-alt-del - ie the keyboard interrupt.
 * As it's called within an interrupt, it may NOT sync: the only choice
 * is whether to reboot at once, or just ignore the ctrl-alt-del.
 */
void ctrl_alt_del(void)
{
        static DECLARE_WORK(cad_work, deferred_cad);

        if (C_A_D)
                schedule_work(&cad_work);
        else
                kill_cad_pid(SIGINT, 1);
}
        
/*
 * Unprivileged users may change the real gid to the effective gid
 * or vice versa.  (BSD-style)
 *
 * If you set the real gid at all, or set the effective gid to a value not
 * equal to the real gid, then the saved gid is set to the new effective gid.
 *
 * This makes it possible for a setgid program to completely drop its
 * privileges, which is often a useful assertion to make when you are doing
 * a security audit over a program.
 *
 * The general idea is that a program which uses just setregid() will be
 * 100% compatible with BSD.  A program which uses just setgid() will be
 * 100% compatible with POSIX with saved IDs. 
 *
 * SMP: There are not races, the GIDs are checked only by filesystem
 *      operations (as far as semantic preservation is concerned).
 */
SYSCALL_DEFINE2(setregid, gid_t, rgid, gid_t, egid)
{
        const struct cred *old;
        struct cred *new;
        int retval;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;
        old = current_cred();

        retval = security_task_setgid(rgid, egid, (gid_t)-1, LSM_SETID_RE);
        if (retval)
                goto error;

        retval = -EPERM;
        if (rgid != (gid_t) -1) {
                if (old->gid == rgid ||
                    old->egid == rgid ||
                    capable(CAP_SETGID))
                        new->gid = rgid;
                else
                        goto error;
        }
        if (egid != (gid_t) -1) {
                if (old->gid == egid ||
                    old->egid == egid ||
                    old->sgid == egid ||
                    capable(CAP_SETGID))
                        new->egid = egid;
                else
                        goto error;
        }

        if (rgid != (gid_t) -1 ||
            (egid != (gid_t) -1 && egid != old->gid))
                new->sgid = new->egid;
        new->fsgid = new->egid;

        return commit_creds(new);

error:
        abort_creds(new);
        return retval;
}

/*
 * setgid() is implemented like SysV w/ SAVED_IDS 
 *
 * SMP: Same implicit races as above.
 */
SYSCALL_DEFINE1(setgid, gid_t, gid)
{
        const struct cred *old;
        struct cred *new;
        int retval;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;
        old = current_cred();

        retval = security_task_setgid(gid, (gid_t)-1, (gid_t)-1, LSM_SETID_ID);
        if (retval)
                goto error;

        retval = -EPERM;
        if (capable(CAP_SETGID))
                new->gid = new->egid = new->sgid = new->fsgid = gid;
        else if (gid == old->gid || gid == old->sgid)
                new->egid = new->fsgid = gid;
        else
                goto error;

        return commit_creds(new);

error:
        abort_creds(new);
        return retval;
}

/*
 * change the user struct in a credentials set to match the new UID
 */
static int set_user(struct cred *new)
{
        struct user_struct *new_user;

        new_user = alloc_uid(current_user_ns(), new->uid);
        if (!new_user)
                return -EAGAIN;

        if (!task_can_switch_user(new_user, current)) {
                free_uid(new_user);
                return -EINVAL;
        }

        if (atomic_read(&new_user->processes) >=
                                current->signal->rlim[RLIMIT_NPROC].rlim_cur &&
                        new_user != INIT_USER) {
                free_uid(new_user);
                return -EAGAIN;
        }

        free_uid(new->user);
        new->user = new_user;
        return 0;
}

/*
 * Unprivileged users may change the real uid to the effective uid
 * or vice versa.  (BSD-style)
 *
 * If you set the real uid at all, or set the effective uid to a value not
 * equal to the real uid, then the saved uid is set to the new effective uid.
 *
 * This makes it possible for a setuid program to completely drop its
 * privileges, which is often a useful assertion to make when you are doing
 * a security audit over a program.
 *
 * The general idea is that a program which uses just setreuid() will be
 * 100% compatible with BSD.  A program which uses just setuid() will be
 * 100% compatible with POSIX with saved IDs. 
 */
SYSCALL_DEFINE2(setreuid, uid_t, ruid, uid_t, euid)
{
        const struct cred *old;
        struct cred *new;
        int retval;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;
        old = current_cred();

        retval = security_task_setuid(ruid, euid, (uid_t)-1, LSM_SETID_RE);
        if (retval)
                goto error;

        retval = -EPERM;
        if (ruid != (uid_t) -1) {
                new->uid = ruid;
                if (old->uid != ruid &&
                    old->euid != ruid &&
                    !capable(CAP_SETUID))
                        goto error;
        }

        if (euid != (uid_t) -1) {
                new->euid = euid;
                if (old->uid != euid &&
                    old->euid != euid &&
                    old->suid != euid &&
                    !capable(CAP_SETUID))
                        goto error;
        }

        if (new->uid != old->uid) {
                retval = set_user(new);
                if (retval < 0)
                        goto error;
        }
        if (ruid != (uid_t) -1 ||
            (euid != (uid_t) -1 && euid != old->uid))
                new->suid = new->euid;
        new->fsuid = new->euid;

        retval = security_task_fix_setuid(new, old, LSM_SETID_RE);
        if (retval < 0)
                goto error;

        return commit_creds(new);

error:
        abort_creds(new);
        return retval;
}
                
/*
 * setuid() is implemented like SysV with SAVED_IDS 
 * 
 * Note that SAVED_ID's is deficient in that a setuid root program
 * like sendmail, for example, cannot set its uid to be a normal 
 * user and then switch back, because if you're root, setuid() sets
 * the saved uid too.  If you don't like this, blame the bright people
 * in the POSIX committee and/or USG.  Note that the BSD-style setreuid()
 * will allow a root program to temporarily drop privileges and be able to
 * regain them by swapping the real and effective uid.  
 */
SYSCALL_DEFINE1(setuid, uid_t, uid)
{
        const struct cred *old;
        struct cred *new;
        int retval;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;
        old = current_cred();

        retval = security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_ID);
        if (retval)
                goto error;

        retval = -EPERM;
        if (capable(CAP_SETUID)) {
                new->suid = new->uid = uid;
                if (uid != old->uid) {
                        retval = set_user(new);
                        if (retval < 0)
                                goto error;
                }
        } else if (uid != old->uid && uid != new->suid) {
                goto error;
        }

        new->fsuid = new->euid = uid;

        retval = security_task_fix_setuid(new, old, LSM_SETID_ID);
        if (retval < 0)
                goto error;

        return commit_creds(new);

error:
        abort_creds(new);
        return retval;
}


/*
 * This function implements a generic ability to update ruid, euid,
 * and suid.  This allows you to implement the 4.4 compatible seteuid().
 */
SYSCALL_DEFINE3(setresuid, uid_t, ruid, uid_t, euid, uid_t, suid)
{
        const struct cred *old;
        struct cred *new;
        int retval;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        retval = security_task_setuid(ruid, euid, suid, LSM_SETID_RES);
        if (retval)
                goto error;
        old = current_cred();

        retval = -EPERM;
        if (!capable(CAP_SETUID)) {
                if (ruid != (uid_t) -1 && ruid != old->uid &&
                    ruid != old->euid  && ruid != old->suid)
                        goto error;
                if (euid != (uid_t) -1 && euid != old->uid &&
                    euid != old->euid  && euid != old->suid)
                        goto error;
                if (suid != (uid_t) -1 && suid != old->uid &&
                    suid != old->euid  && suid != old->suid)
                        goto error;
        }

        if (ruid != (uid_t) -1) {
                new->uid = ruid;
                if (ruid != old->uid) {
                        retval = set_user(new);
                        if (retval < 0)
                                goto error;
                }
        }
        if (euid != (uid_t) -1)
                new->euid = euid;
        if (suid != (uid_t) -1)
                new->suid = suid;
        new->fsuid = new->euid;

        retval = security_task_fix_setuid(new, old, LSM_SETID_RES);
        if (retval < 0)
                goto error;

        return commit_creds(new);

error:
        abort_creds(new);
        return retval;
}

SYSCALL_DEFINE3(getresuid, uid_t __user *, ruid, uid_t __user *, euid, uid_t __user *, suid)
{
        const struct cred *cred = current_cred();
        int retval;

        if (!(retval   = put_user(cred->uid,  ruid)) &&
            !(retval   = put_user(cred->euid, euid)))
                retval = put_user(cred->suid, suid);

        return retval;
}

/*
 * Same as above, but for rgid, egid, sgid.
 */
SYSCALL_DEFINE3(setresgid, gid_t, rgid, gid_t, egid, gid_t, sgid)
{
        const struct cred *old;
        struct cred *new;
        int retval;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;
        old = current_cred();

        retval = security_task_setgid(rgid, egid, sgid, LSM_SETID_RES);
        if (retval)
                goto error;

        retval = -EPERM;
        if (!capable(CAP_SETGID)) {
                if (rgid != (gid_t) -1 && rgid != old->gid &&
                    rgid != old->egid  && rgid != old->sgid)
                        goto error;
                if (egid != (gid_t) -1 && egid != old->gid &&
                    egid != old->egid  && egid != old->sgid)
                        goto error;
                if (sgid != (gid_t) -1 && sgid != old->gid &&
                    sgid != old->egid  && sgid != old->sgid)
                        goto error;
        }

        if (rgid != (gid_t) -1)
                new->gid = rgid;
        if (egid != (gid_t) -1)
                new->egid = egid;
        if (sgid != (gid_t) -1)
                new->sgid = sgid;
        new->fsgid = new->egid;

        return commit_creds(new);

error:
        abort_creds(new);
        return retval;
}

SYSCALL_DEFINE3(getresgid, gid_t __user *, rgid, gid_t __user *, egid, gid_t __user *, sgid)
{
        const struct cred *cred = current_cred();
        int retval;

        if (!(retval   = put_user(cred->gid,  rgid)) &&
            !(retval   = put_user(cred->egid, egid)))
                retval = put_user(cred->sgid, sgid);

        return retval;
}


/*
 * "setfsuid()" sets the fsuid - the uid used for filesystem checks. This
 * is used for "access()" and for the NFS daemon (letting nfsd stay at
 * whatever uid it wants to). It normally shadows "euid", except when
 * explicitly set by setfsuid() or for access..
 */
SYSCALL_DEFINE1(setfsuid, uid_t, uid)
{
        const struct cred *old;
        struct cred *new;
        uid_t old_fsuid;

        new = prepare_creds();
        if (!new)
                return current_fsuid();
        old = current_cred();
        old_fsuid = old->fsuid;

        if (security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS) < 0)
                goto error;

        if (uid == old->uid  || uid == old->euid  ||
            uid == old->suid || uid == old->fsuid ||
            capable(CAP_SETUID)) {
                if (uid != old_fsuid) {
                        new->fsuid = uid;
                        if (security_task_fix_setuid(new, old, LSM_SETID_FS) == 0)
                                goto change_okay;
                }
        }

error:
        abort_creds(new);
        return old_fsuid;

change_okay:
        commit_creds(new);
        return old_fsuid;
}

/*
 * Samma på svenska..
 */
SYSCALL_DEFINE1(setfsgid, gid_t, gid)
{
        const struct cred *old;
        struct cred *new;
        gid_t old_fsgid;

        new = prepare_creds();
        if (!new)
                return current_fsgid();
        old = current_cred();
        old_fsgid = old->fsgid;

        if (security_task_setgid(gid, (gid_t)-1, (gid_t)-1, LSM_SETID_FS))
                goto error;

        if (gid == old->gid  || gid == old->egid  ||
            gid == old->sgid || gid == old->fsgid ||
            capable(CAP_SETGID)) {
                if (gid != old_fsgid) {
                        new->fsgid = gid;
                        goto change_okay;
                }
        }

error:
        abort_creds(new);
        return old_fsgid;

change_okay:
        commit_creds(new);
        return old_fsgid;
}

void do_sys_times(struct tms *tms)
{
        struct task_cputime cputime;
        cputime_t cutime, cstime;

        thread_group_cputime(current, &cputime);
        spin_lock_irq(&current->sighand->siglock);
        cutime = current->signal->cutime;
        cstime = current->signal->cstime;
        spin_unlock_irq(&current->sighand->siglock);
        tms->tms_utime = cputime_to_clock_t(cputime.utime);
        tms->tms_stime = cputime_to_clock_t(cputime.stime);
        tms->tms_cutime = cputime_to_clock_t(cutime);
        tms->tms_cstime = cputime_to_clock_t(cstime);
}

SYSCALL_DEFINE1(times, struct tms __user *, tbuf)
{
        if (tbuf) {
                struct tms tmp;

                do_sys_times(&tmp);
                if (copy_to_user(tbuf, &tmp, sizeof(struct tms)))
                        return -EFAULT;
        }
        force_successful_syscall_return();
        return (long) jiffies_64_to_clock_t(get_jiffies_64());
}

/*
 * This needs some heavy checking ...
 * I just haven't the stomach for it. I also don't fully
 * understand sessions/pgrp etc. Let somebody who does explain it.
 *
 * OK, I think I have the protection semantics right.... this is really
 * only important on a multi-user system anyway, to make sure one user
 * can't send a signal to a process owned by another.  -TYT, 12/12/91
 *
 * Auch. Had to add the 'did_exec' flag to conform completely to POSIX.
 * LBT 04.03.94
 */
SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)
{
        struct task_struct *p;
        struct task_struct *group_leader = current->group_leader;
        struct pid *pgrp;
        int err;

        if (!pid)
                pid = task_pid_vnr(group_leader);
        if (!pgid)
                pgid = pid;
        if (pgid < 0)
                return -EINVAL;

        /* From this point forward we keep holding onto the tasklist lock
         * so that our parent does not change from under us. -DaveM
         */
        write_lock_irq(&tasklist_lock);

        err = -ESRCH;
        p = find_task_by_vpid(pid);
        if (!p)
                goto out;

        err = -EINVAL;
        if (!thread_group_leader(p))
                goto out;

        if (same_thread_group(p->real_parent, group_leader)) {
                err = -EPERM;
                if (task_session(p) != task_session(group_leader))
                        goto out;
                err = -EACCES;
                if (p->did_exec)
                        goto out;
        } else {
                err = -ESRCH;
                if (p != group_leader)
                        goto out;
        }

        err = -EPERM;
        if (p->signal->leader)
                goto out;

        pgrp = task_pid(p);
        if (pgid != pid) {
                struct task_struct *g;

                pgrp = find_vpid(pgid);
                g = pid_task(pgrp, PIDTYPE_PGID);
                if (!g || task_session(g) != task_session(group_leader))
                        goto out;
        }

        err = security_task_setpgid(p, pgid);
        if (err)
                goto out;

        if (task_pgrp(p) != pgrp)
                change_pid(p, PIDTYPE_PGID, pgrp);

        err = 0;
out:
        /* All paths lead to here, thus we are safe. -DaveM */
        write_unlock_irq(&tasklist_lock);
        return err;
}

SYSCALL_DEFINE1(getpgid, pid_t, pid)
{
        struct task_struct *p;
        struct pid *grp;
        int retval;

        rcu_read_lock();
        if (!pid)
                grp = task_pgrp(current);
        else {
                retval = -ESRCH;
                p = find_task_by_vpid(pid);
                if (!p)
                        goto out;
                grp = task_pgrp(p);
                if (!grp)
                        goto out;

                retval = security_task_getpgid(p);
                if (retval)
                        goto out;
        }
        retval = pid_vnr(grp);
out:
        rcu_read_unlock();
        return retval;
}

#ifdef __ARCH_WANT_SYS_GETPGRP

SYSCALL_DEFINE0(getpgrp)
{
        return sys_getpgid(0);
}

#endif

SYSCALL_DEFINE1(getsid, pid_t, pid)
{
        struct task_struct *p;
        struct pid *sid;
        int retval;

        rcu_read_lock();
        if (!pid)
                sid = task_session(current);
        else {
                retval = -ESRCH;
                p = find_task_by_vpid(pid);
                if (!p)
                        goto out;
                sid = task_session(p);
                if (!sid)
                        goto out;

                retval = security_task_getsid(p);
                if (retval)
                        goto out;
        }
        retval = pid_vnr(sid);
out:
        rcu_read_unlock();
        return retval;
}

SYSCALL_DEFINE0(setsid)
{
        struct task_struct *group_leader = current->group_leader;
        struct pid *sid = task_pid(group_leader);
        pid_t session = pid_vnr(sid);
        int err = -EPERM;

        write_lock_irq(&tasklist_lock);
        /* Fail if I am already a session leader */
        if (group_leader->signal->leader)
                goto out;

        /* Fail if a process group id already exists that equals the
         * proposed session id.
         */
        if (pid_task(sid, PIDTYPE_PGID))
                goto out;

        group_leader->signal->leader = 1;
        __set_special_pids(sid);

        proc_clear_tty(group_leader);

        err = session;
out:
        write_unlock_irq(&tasklist_lock);
        if (err > 0)
                proc_sid_connector(group_leader);
        return err;
}

DECLARE_RWSEM(uts_sem);

SYSCALL_DEFINE1(newuname, struct new_utsname __user *, name)
{
        int errno = 0;

        down_read(&uts_sem);
        if (copy_to_user(name, utsname(), sizeof *name))
                errno = -EFAULT;
        up_read(&uts_sem);
        return errno;
}

SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)
{
        int errno;
        char tmp[__NEW_UTS_LEN];

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
        if (len < 0 || len > __NEW_UTS_LEN)
                return -EINVAL;
        down_write(&uts_sem);
        errno = -EFAULT;
        if (!copy_from_user(tmp, name, len)) {
                struct new_utsname *u = utsname();

                memcpy(u->nodename, tmp, len);
                memset(u->nodename + len, 0, sizeof(u->nodename) - len);
                errno = 0;
        }
        up_write(&uts_sem);
        return errno;
}

#ifdef __ARCH_WANT_SYS_GETHOSTNAME

SYSCALL_DEFINE2(gethostname, char __user *, name, int, len)
{
        int i, errno;
        struct new_utsname *u;

        if (len < 0)
                return -EINVAL;
        down_read(&uts_sem);
        u = utsname();
        i = 1 + strlen(u->nodename);
        if (i > len)
                i = len;
        errno = 0;
        if (copy_to_user(name, u->nodename, i))
                errno = -EFAULT;
        up_read(&uts_sem);
        return errno;
}

#endif

/*
 * Only setdomainname; getdomainname can be implemented by calling
 * uname()
 */
SYSCALL_DEFINE2(setdomainname, char __user *, name, int, len)
{
        int errno;
        char tmp[__NEW_UTS_LEN];

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
        if (len < 0 || len > __NEW_UTS_LEN)
                return -EINVAL;

        down_write(&uts_sem);
        errno = -EFAULT;
        if (!copy_from_user(tmp, name, len)) {
                struct new_utsname *u = utsname();

                memcpy(u->domainname, tmp, len);
                memset(u->domainname + len, 0, sizeof(u->domainname) - len);
                errno = 0;
        }
        up_write(&uts_sem);
        return errno;
}

SYSCALL_DEFINE2(getrlimit, unsigned int, resource, struct rlimit __user *, rlim)
{
        if (resource >= RLIM_NLIMITS)
                return -EINVAL;
        else {
                struct rlimit value;
                task_lock(current->group_leader);
                value = current->signal->rlim[resource];
                task_unlock(current->group_leader);
                return copy_to_user(rlim, &value, sizeof(*rlim)) ? -EFAULT : 0;
        }
}

#ifdef __ARCH_WANT_SYS_OLD_GETRLIMIT

/*
 *      Back compatibility for getrlimit. Needed for some apps.
 */
 
SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
                struct rlimit __user *, rlim)
{
        struct rlimit x;
        if (resource >= RLIM_NLIMITS)
                return -EINVAL;

        task_lock(current->group_leader);
        x = current->signal->rlim[resource];
        task_unlock(current->group_leader);
        if (x.rlim_cur > 0x7FFFFFFF)
                x.rlim_cur = 0x7FFFFFFF;
        if (x.rlim_max > 0x7FFFFFFF)
                x.rlim_max = 0x7FFFFFFF;
        return copy_to_user(rlim, &x, sizeof(x))?-EFAULT:0;
}

#endif

SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
{
        struct rlimit new_rlim, *old_rlim;
        int retval;

        if (resource >= RLIM_NLIMITS)
                return -EINVAL;
        if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
                return -EFAULT;
        if (new_rlim.rlim_cur > new_rlim.rlim_max)
                return -EINVAL;
        old_rlim = current->signal->rlim + resource;
        if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
            !capable(CAP_SYS_RESOURCE))
                return -EPERM;
        if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
                return -EPERM;

        retval = security_task_setrlimit(resource, &new_rlim);
        if (retval)
                return retval;

        if (resource == RLIMIT_CPU && new_rlim.rlim_cur == 0) {
                /*
                 * The caller is asking for an immediate RLIMIT_CPU
                 * expiry.  But we use the zero value to mean "it was
                 * never set".  So let's cheat and make it one second
                 * instead
                 */
                new_rlim.rlim_cur = 1;
        }

        task_lock(current->group_leader);
        *old_rlim = new_rlim;
        task_unlock(current->group_leader);

        if (resource != RLIMIT_CPU)
                goto out;

        /*
         * RLIMIT_CPU handling.   Note that the kernel fails to return an error
         * code if it rejected the user's attempt to set RLIMIT_CPU.  This is a
         * very long-standing error, and fixing it now risks breakage of
         * applications, so we live with it
         */
        if (new_rlim.rlim_cur == RLIM_INFINITY)
                goto out;

        update_rlimit_cpu(new_rlim.rlim_cur);
out:
        return 0;
}

/*
 * It would make sense to put struct rusage in the task_struct,
 * except that would make the task_struct be *really big*.  After
 * task_struct gets moved into malloc'ed memory, it would
 * make sense to do this.  It will make moving the rest of the information
 * a lot simpler!  (Which we're not doing right now because we're not
 * measuring them yet).
 *
 * When sampling multiple threads for RUSAGE_SELF, under SMP we might have
 * races with threads incrementing their own counters.  But since word
 * reads are atomic, we either get new values or old values and we don't
 * care which for the sums.  We always take the siglock to protect reading
 * the c* fields from p->signal from races with exit.c updating those
 * fields when reaping, so a sample either gets all the additions of a
 * given child after it's reaped, or none so this sample is before reaping.
 *
 * Locking:
 * We need to take the siglock for CHILDEREN, SELF and BOTH
 * for  the cases current multithreaded, non-current single threaded
 * non-current multithreaded.  Thread traversal is now safe with
 * the siglock held.
 * Strictly speaking, we donot need to take the siglock if we are current and
 * single threaded,  as no one else can take our signal_struct away, no one
 * else can  reap the  children to update signal->c* counters, and no one else
 * can race with the signal-> fields. If we do not take any lock, the
 * signal-> fields could be read out of order while another thread was just
 * exiting. So we should  place a read memory barrier when we avoid the lock.
 * On the writer side,  write memory barrier is implied in  __exit_signal
 * as __exit_signal releases  the siglock spinlock after updating the signal->
 * fields. But we don't do this yet to keep things simple.
 *
 */

static void accumulate_thread_rusage(struct task_struct *t, struct rusage *r)
{
        r->ru_nvcsw += t->nvcsw;
        r->ru_nivcsw += t->nivcsw;
        r->ru_minflt += t->min_flt;
        r->ru_majflt += t->maj_flt;
        r->ru_inblock += task_io_get_inblock(t);
        r->ru_oublock += task_io_get_oublock(t);
}

static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
{
        struct task_struct *t;
        unsigned long flags;
        cputime_t utime, stime;
        struct task_cputime cputime;
        unsigned long maxrss = 0;

        memset((char *) r, 0, sizeof *r);
        utime = stime = cputime_zero;

        if (who == RUSAGE_THREAD) {
                utime = task_utime(current);
                stime = task_stime(current);
                accumulate_thread_rusage(p, r);
                maxrss = p->signal->maxrss;
                goto out;
        }

        if (!lock_task_sighand(p, &flags))
                return;

        switch (who) {
                case RUSAGE_BOTH:
                case RUSAGE_CHILDREN:
                        utime = p->signal->cutime;
                        stime = p->signal->cstime;
                        r->ru_nvcsw = p->signal->cnvcsw;
                        r->ru_nivcsw = p->signal->cnivcsw;
                        r->ru_minflt = p->signal->cmin_flt;
                        r->ru_majflt = p->signal->cmaj_flt;
                        r->ru_inblock = p->signal->cinblock;
                        r->ru_oublock = p->signal->coublock;
                        maxrss = p->signal->cmaxrss;

                        if (who == RUSAGE_CHILDREN)
                                break;

                case RUSAGE_SELF:
                        thread_group_cputime(p, &cputime);
                        utime = cputime_add(utime, cputime.utime);
                        stime = cputime_add(stime, cputime.stime);
                        r->ru_nvcsw += p->signal->nvcsw;
                        r->ru_nivcsw += p->signal->nivcsw;
                        r->ru_minflt += p->signal->min_flt;
                        r->ru_majflt += p->signal->maj_flt;
                        r->ru_inblock += p->signal->inblock;
                        r->ru_oublock += p->signal->oublock;
                        if (maxrss < p->signal->maxrss)
                                maxrss = p->signal->maxrss;
                        t = p;
                        do {
                                accumulate_thread_rusage(t, r);
                                t = next_thread(t);
                        } while (t != p);
                        break;

                default:
                        BUG();
        }
        unlock_task_sighand(p, &flags);

out:
        cputime_to_timeval(utime, &r->ru_utime);
        cputime_to_timeval(stime, &r->ru_stime);

        if (who != RUSAGE_CHILDREN) {
                struct mm_struct *mm = get_task_mm(p);
                if (mm) {
                        setmax_mm_hiwater_rss(&maxrss, mm);
                        mmput(mm);
                }
        }
        r->ru_maxrss = maxrss * (PAGE_SIZE / 1024); /* convert pages to KBs */
}

int getrusage(struct task_struct *p, int who, struct rusage __user *ru)
{
        struct rusage r;
        k_getrusage(p, who, &r);
        return copy_to_user(ru, &r, sizeof(r)) ? -EFAULT : 0;
}

SYSCALL_DEFINE2(getrusage, int, who, struct rusage __user *, ru)
{
        if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN &&
            who != RUSAGE_THREAD)
                return -EINVAL;
        return getrusage(current, who, ru);
}

SYSCALL_DEFINE1(umask, int, mask)
{
        mask = xchg(&current->fs->umask, mask & S_IRWXUGO);
        return mask;
}

SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
                unsigned long, arg4, unsigned long, arg5)
{
        struct task_struct *me = current;
        unsigned char comm[sizeof(me->comm)];
        long error;

        error = security_task_prctl(option, arg2, arg3, arg4, arg5);
        if (error != -ENOSYS)
                return error;

        error = 0;
        switch (option) {
                case PR_SET_PDEATHSIG:
                        if (!valid_signal(arg2)) {
                                error = -EINVAL;
                                break;
                        }
                        me->pdeath_signal = arg2;
                        error = 0;
                        break;
                case PR_GET_PDEATHSIG:
                        error = put_user(me->pdeath_signal, (int __user *)arg2);
                        break;
                case PR_GET_DUMPABLE:
                        error = get_dumpable(me->mm);
                        break;
                case PR_SET_DUMPABLE:
                        if (arg2 < 0 || arg2 > 1) {
                                error = -EINVAL;
                                break;
                        }
                        set_dumpable(me->mm, arg2);
                        error = 0;
                        break;

                case PR_SET_UNALIGN:
                        error = SET_UNALIGN_CTL(me, arg2);
                        break;
                case PR_GET_UNALIGN:
                        error = GET_UNALIGN_CTL(me, arg2);
                        break;
                case PR_SET_FPEMU:
                        error = SET_FPEMU_CTL(me, arg2);
                        break;
                case PR_GET_FPEMU:
                        error = GET_FPEMU_CTL(me, arg2);
                        break;
                case PR_SET_FPEXC:
                        error = SET_FPEXC_CTL(me, arg2);
                        break;
                case PR_GET_FPEXC:
                        error = GET_FPEXC_CTL(me, arg2);
                        break;
                case PR_GET_TIMING:
                        error = PR_TIMING_STATISTICAL;
                        break;
                case PR_SET_TIMING:
                        if (arg2 != PR_TIMING_STATISTICAL)
                                error = -EINVAL;
                        else
                                error = 0;
                        break;

                case PR_SET_NAME:
                        comm[sizeof(me->comm)-1] = 0;
                        if (strncpy_from_user(comm, (char __user *)arg2,
                                              sizeof(me->comm) - 1) < 0)
                                return -EFAULT;
                        set_task_comm(me, comm);
                        return 0;
                case PR_GET_NAME:
                        get_task_comm(comm, me);
                        if (copy_to_user((char __user *)arg2, comm,
                                         sizeof(comm)))
                                return -EFAULT;
                        return 0;
                case PR_GET_ENDIAN:
                        error = GET_ENDIAN(me, arg2);
                        break;
                case PR_SET_ENDIAN:
                        error = SET_ENDIAN(me, arg2);
                        break;

                case PR_GET_SECCOMP:
                        error = prctl_get_seccomp();
                        break;
                case PR_SET_SECCOMP:
                        error = prctl_set_seccomp(arg2);
                        break;
                case PR_GET_TSC:
                        error = GET_TSC_CTL(arg2);
                        break;
                case PR_SET_TSC:
                        error = SET_TSC_CTL(arg2);
                        break;
                case PR_TASK_PERF_EVENTS_DISABLE:
                        error = perf_event_task_disable();
                        break;
                case PR_TASK_PERF_EVENTS_ENABLE:
                        error = perf_event_task_enable();
                        break;
                case PR_GET_TIMERSLACK:
                        error = current->timer_slack_ns;
                        break;
                case PR_SET_TIMERSLACK:
                        if (arg2 <= 0)
                                current->timer_slack_ns =
                                        current->default_timer_slack_ns;
                        else
                                current->timer_slack_ns = arg2;
                        error = 0;
                        break;
                case PR_MCE_KILL:
                        if (arg4 | arg5)
                                return -EINVAL;
                        switch (arg2) {
                        case PR_MCE_KILL_CLEAR:
                                if (arg3 != 0)
                                        return -EINVAL;
                                current->flags &= ~PF_MCE_PROCESS;
                                break;
                        case PR_MCE_KILL_SET:
                                current->flags |= PF_MCE_PROCESS;
                                if (arg3 == PR_MCE_KILL_EARLY)
                                        current->flags |= PF_MCE_EARLY;
                                else if (arg3 == PR_MCE_KILL_LATE)
                                        current->flags &= ~PF_MCE_EARLY;
                                else if (arg3 == PR_MCE_KILL_DEFAULT)
                                        current->flags &=
                                                ~(PF_MCE_EARLY|PF_MCE_PROCESS);
                                else
                                        return -EINVAL;
                                break;
                        default:
                                return -EINVAL;
                        }
                        error = 0;
                        break;
                case PR_MCE_KILL_GET:
                        if (arg2 | arg3 | arg4 | arg5)
                                return -EINVAL;
                        if (current->flags & PF_MCE_PROCESS)
                                error = (current->flags & PF_MCE_EARLY) ?
                                        PR_MCE_KILL_EARLY : PR_MCE_KILL_LATE;
                        else
                                error = PR_MCE_KILL_DEFAULT;
                        break;
                default:
                        error = -EINVAL;
                        break;
        }
        return error;
}

SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep,
                struct getcpu_cache __user *, unused)
{
        int err = 0;
        int cpu = raw_smp_processor_id();
        if (cpup)
                err |= put_user(cpu, cpup);
        if (nodep)
                err |= put_user(cpu_to_node(cpu), nodep);
        return err ? -EFAULT : 0;
}

char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";

static void argv_cleanup(char **argv, char **envp)
{
        argv_free(argv);
}

/**
 * orderly_poweroff - Trigger an orderly system poweroff
 * @force: force poweroff if command execution fails
 *
 * This may be called from any context to trigger a system shutdown.
 * If the orderly shutdown fails, it will force an immediate shutdown.
 */
int orderly_poweroff(bool force)
{
        int argc;
        char **argv = argv_split(GFP_ATOMIC, poweroff_cmd, &argc);
        static char *envp[] = {
                "HOME=/",
                "PATH=/sbin:/bin:/usr/sbin:/usr/bin",
                NULL
        };
        int ret = -ENOMEM;
        struct subprocess_info *info;

        if (argv == NULL) {
                printk(KERN_WARNING "%s failed to allocate memory for \"%s\"\n",
                       __func__, poweroff_cmd);
                goto out;
        }

        info = call_usermodehelper_setup(argv[0], argv, envp, GFP_ATOMIC);
        if (info == NULL) {
                argv_free(argv);
                goto out;
        }

        call_usermodehelper_setcleanup(info, argv_cleanup);

        ret = call_usermodehelper_exec(info, UMH_NO_WAIT);

  out:
        if (ret && force) {
                printk(KERN_WARNING "Failed to start orderly shutdown: "
                       "forcing the issue\n");

                /* I guess this should try to kick off some daemon to
                   sync and poweroff asap.  Or not even bother syncing
                   if we're doing an emergency shutdown? */
                emergency_sync();
                kernel_power_off();
        }

        return ret;
}
EXPORT_SYMBOL_GPL(orderly_poweroff);