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

#include <linux/config.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/smp_lock.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/tty.h>
#include <linux/namespace.h>
#include <linux/security.h>
#include <linux/acct.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/ptrace.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

extern void sem_exit (void);
extern struct task_struct *child_reaper;

int getrusage(struct task_struct *, int, struct rusage *);

static struct dentry * __unhash_process(struct task_struct *p)
{
        struct dentry *proc_dentry;
        nr_threads--;
        detach_pid(p, PIDTYPE_PID);
        if (thread_group_leader(p)) {
                detach_pid(p, PIDTYPE_PGID);
                detach_pid(p, PIDTYPE_SID);
        }

        REMOVE_LINKS(p);
        p->pid = 0;
        proc_dentry = p->proc_dentry;
        if (unlikely(proc_dentry != NULL)) {
                spin_lock(&dcache_lock);
                if (!list_empty(&proc_dentry->d_hash)) {
                        dget_locked(proc_dentry);
                        list_del_init(&proc_dentry->d_hash);
                } else
                        proc_dentry = NULL;
                spin_unlock(&dcache_lock);
        }
        return proc_dentry;
}

void release_task(struct task_struct * p)
{
        struct dentry *proc_dentry;

        if (p->state != TASK_ZOMBIE)
                BUG();
        if (p != current)
                wait_task_inactive(p);
        atomic_dec(&p->user->processes);
        security_ops->task_free_security(p);
        free_uid(p->user);
        if (unlikely(p->ptrace)) {
                write_lock_irq(&tasklist_lock);
                __ptrace_unlink(p);
                write_unlock_irq(&tasklist_lock);
        }
        BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
        write_lock_irq(&tasklist_lock);
        __exit_sighand(p);
        proc_dentry = __unhash_process(p);
        p->parent->cutime += p->utime + p->cutime;
        p->parent->cstime += p->stime + p->cstime;
        p->parent->cmin_flt += p->min_flt + p->cmin_flt;
        p->parent->cmaj_flt += p->maj_flt + p->cmaj_flt;
        p->parent->cnswap += p->nswap + p->cnswap;
        sched_exit(p);
        write_unlock_irq(&tasklist_lock);

        if (unlikely(proc_dentry != NULL)) {
                shrink_dcache_parent(proc_dentry);
                dput(proc_dentry);
        }
        release_thread(p);
        put_task_struct(p);
}

/* we are using it only for SMP init */

void unhash_process(struct task_struct *p)
{
        struct dentry *proc_dentry;

        write_lock_irq(&tasklist_lock);
        proc_dentry = __unhash_process(p);
        write_unlock_irq(&tasklist_lock);

        if (unlikely(proc_dentry != NULL)) {
                shrink_dcache_parent(proc_dentry);
                dput(proc_dentry);
        }
}

/*
 * This checks not only the pgrp, but falls back on the pid if no
 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 * without this...
 */
int session_of_pgrp(int pgrp)
{
        struct task_struct *p;
        struct list_head *l;
        struct pid *pid;
        int sid = -1;

        read_lock(&tasklist_lock);
        for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid)
                if (p->session > 0) {
                        sid = p->session;
                        break;
                }
        read_unlock(&tasklist_lock);
        return sid;
}

/*
 * Determine if a process group is "orphaned", according to the POSIX
 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 * by terminal-generated stop signals.  Newly orphaned process groups are
 * to receive a SIGHUP and a SIGCONT.
 *
 * "I ask you, have you ever known what it is to be an orphan?"
 */
static int __will_become_orphaned_pgrp(int pgrp, task_t *ignored_task)
{
        struct task_struct *p;
        struct list_head *l;
        struct pid *pid;
        int ret = 1;

        for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid) {
                if (p == ignored_task
                                || p->state == TASK_ZOMBIE 
                                || p->real_parent->pid == 1)
                        continue;
                if (p->real_parent->pgrp != pgrp
                            && p->real_parent->session == p->session) {
                        ret = 0;
                        break;
                }
        }
        return ret;     /* (sighing) "Often!" */
}

static int will_become_orphaned_pgrp(int pgrp, struct task_struct * ignored_task)
{
        int retval;

        read_lock(&tasklist_lock);
        retval = __will_become_orphaned_pgrp(pgrp, ignored_task);
        read_unlock(&tasklist_lock);

        return retval;
}

int is_orphaned_pgrp(int pgrp)
{
        return will_become_orphaned_pgrp(pgrp, 0);
}

static inline int __has_stopped_jobs(int pgrp)
{
        int retval = 0;
        struct task_struct *p;
        struct list_head *l;
        struct pid *pid;

        for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid) {
                if (p->state != TASK_STOPPED)
                        continue;
                retval = 1;
                break;
        }
        return retval;
}

static inline int has_stopped_jobs(int pgrp)
{
        int retval;

        read_lock(&tasklist_lock);
        retval = __has_stopped_jobs(pgrp);
        read_unlock(&tasklist_lock);

        return retval;
}

/**
 * reparent_to_init() - Reparent the calling kernel thread to the init task.
 *
 * If a kernel thread is launched as a result of a system call, or if
 * it ever exits, it should generally reparent itself to init so that
 * it is correctly cleaned up on exit.
 *
 * The various task state such as scheduling policy and priority may have
 * been inherited from a user process, so we reset them to sane values here.
 *
 * NOTE that reparent_to_init() gives the caller full capabilities.
 */
void reparent_to_init(void)
{
        write_lock_irq(&tasklist_lock);

        ptrace_unlink(current);
        /* Reparent to init */
        REMOVE_LINKS(current);
        current->parent = child_reaper;
        current->real_parent = child_reaper;
        SET_LINKS(current);

        /* Set the exit signal to SIGCHLD so we signal init on exit */
        current->exit_signal = SIGCHLD;

        if ((current->policy == SCHED_NORMAL) && (task_nice(current) < 0))
                set_user_nice(current, 0);
        /* cpus_allowed? */
        /* rt_priority? */
        /* signals? */
        security_ops->task_reparent_to_init(current);
        memcpy(current->rlim, init_task.rlim, sizeof(*(current->rlim)));
        current->user = INIT_USER;

        write_unlock_irq(&tasklist_lock);
}

/*
 *      Put all the gunge required to become a kernel thread without
 *      attached user resources in one place where it belongs.
 */

void daemonize(void)
{
        struct fs_struct *fs;


        /*
         * If we were started as result of loading a module, close all of the
         * user space pages.  We don't need them, and if we didn't close them
         * they would be locked into memory.
         */
        exit_mm(current);

        current->session = 1;
        current->pgrp = 1;
        current->tty = NULL;

        /* Become as one with the init task */

        exit_fs(current);       /* current->fs->count--; */
        fs = init_task.fs;
        current->fs = fs;
        atomic_inc(&fs->count);
        exit_files(current);
        current->files = init_task.files;
        atomic_inc(&current->files->count);

        reparent_to_init();
}

static inline void close_files(struct files_struct * files)
{
        int i, j;

        j = 0;
        for (;;) {
                unsigned long set;
                i = j * __NFDBITS;
                if (i >= files->max_fdset || i >= files->max_fds)
                        break;
                set = files->open_fds->fds_bits[j++];
                while (set) {
                        if (set & 1) {
                                struct file * file = xchg(&files->fd[i], NULL);
                                if (file)
                                        filp_close(file, files);
                        }
                        i++;
                        set >>= 1;
                }
        }
}

void put_files_struct(struct files_struct *files)
{
        if (atomic_dec_and_test(&files->count)) {
                close_files(files);
                /*
                 * Free the fd and fdset arrays if we expanded them.
                 */
                if (files->fd != &files->fd_array[0])
                        free_fd_array(files->fd, files->max_fds);
                if (files->max_fdset > __FD_SETSIZE) {
                        free_fdset(files->open_fds, files->max_fdset);
                        free_fdset(files->close_on_exec, files->max_fdset);
                }
                kmem_cache_free(files_cachep, files);
        }
}

static inline void __exit_files(struct task_struct *tsk)
{
        struct files_struct * files = tsk->files;

        if (files) {
                task_lock(tsk);
                tsk->files = NULL;
                task_unlock(tsk);
                put_files_struct(files);
        }
}

void exit_files(struct task_struct *tsk)
{
        __exit_files(tsk);
}

static inline void __put_fs_struct(struct fs_struct *fs)
{
        /* No need to hold fs->lock if we are killing it */
        if (atomic_dec_and_test(&fs->count)) {
                dput(fs->root);
                mntput(fs->rootmnt);
                dput(fs->pwd);
                mntput(fs->pwdmnt);
                if (fs->altroot) {
                        dput(fs->altroot);
                        mntput(fs->altrootmnt);
                }
                kmem_cache_free(fs_cachep, fs);
        }
}

void put_fs_struct(struct fs_struct *fs)
{
        __put_fs_struct(fs);
}

static inline void __exit_fs(struct task_struct *tsk)
{
        struct fs_struct * fs = tsk->fs;

        if (fs) {
                task_lock(tsk);
                tsk->fs = NULL;
                task_unlock(tsk);
                __put_fs_struct(fs);
        }
}

void exit_fs(struct task_struct *tsk)
{
        __exit_fs(tsk);
}

/*
 * We can use these to temporarily drop into
 * "lazy TLB" mode and back.
 */
struct mm_struct * start_lazy_tlb(void)
{
        struct mm_struct *mm = current->mm;
        current->mm = NULL;
        /* active_mm is still 'mm' */
        atomic_inc(&mm->mm_count);
        enter_lazy_tlb(mm, current, smp_processor_id());
        return mm;
}

void end_lazy_tlb(struct mm_struct *mm)
{
        struct mm_struct *active_mm = current->active_mm;

        current->mm = mm;
        if (mm != active_mm) {
                current->active_mm = mm;
                activate_mm(active_mm, mm);
        }
        mmdrop(active_mm);
}

/*
 * Turn us into a lazy TLB process if we
 * aren't already..
 */
static inline void __exit_mm(struct task_struct * tsk)
{
        struct mm_struct * mm = tsk->mm;

        mm_release();
        if (mm) {
                atomic_inc(&mm->mm_count);
                if (mm != tsk->active_mm) BUG();
                /* more a memory barrier than a real lock */
                task_lock(tsk);
                tsk->mm = NULL;
                enter_lazy_tlb(mm, current, smp_processor_id());
                task_unlock(tsk);
                mmput(mm);
        }
}

void exit_mm(struct task_struct *tsk)
{
        __exit_mm(tsk);
}

static inline void choose_new_parent(task_t *p, task_t *reaper, task_t *child_reaper)
{
        /* Make sure we're not reparenting to ourselves.  */
        if (p == reaper)
                p->real_parent = child_reaper;
        else
                p->real_parent = reaper;
        if (p->parent == p->real_parent)
                BUG();
}

static inline void reparent_thread(task_t *p, task_t *father, int traced)
{
        /* We dont want people slaying init.  */
        if (p->exit_signal != -1)
                p->exit_signal = SIGCHLD;
        p->self_exec_id++;

        if (p->pdeath_signal)
                send_sig(p->pdeath_signal, p, 0);

        /* Move the child from its dying parent to the new one.  */
        if (unlikely(traced)) {
                /* Preserve ptrace links if someone else is tracing this child.  */
                list_del_init(&p->ptrace_list);
                if (p->parent != p->real_parent)
                        list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
        } else {
                /* If this child is being traced, then we're the one tracing it
                 * anyway, so let go of it.
                 */
                p->ptrace = 0;
                list_del_init(&p->sibling);
                p->parent = p->real_parent;
                list_add_tail(&p->sibling, &p->parent->children);

                /* If we'd notified the old parent about this child's death,
                 * also notify the new parent.
                 */
                if (p->state == TASK_ZOMBIE && p->exit_signal != -1)
                        do_notify_parent(p, p->exit_signal);
        }

        /*
         * process group orphan check
         * Case ii: Our child is in a different pgrp
         * than we are, and it was the only connection
         * outside, so the child pgrp is now orphaned.
         */
        if ((p->pgrp != father->pgrp) &&
            (p->session == father->session)) {
                int pgrp = p->pgrp;

                if (__will_become_orphaned_pgrp(pgrp, 0) && __has_stopped_jobs(pgrp)) {
                        __kill_pg_info(SIGHUP, (void *)1, pgrp);
                        __kill_pg_info(SIGCONT, (void *)1, pgrp);
                }
        }
}

/*
 * When we die, we re-parent all our children.
 * Try to give them to another thread in our thread
 * group, and if no such member exists, give it to
 * the global child reaper process (ie "init")
 */
static inline void forget_original_parent(struct task_struct * father)
{
        struct task_struct *p, *reaper = father;
        struct list_head *_p, *_n;

        reaper = father->group_leader;
        if (reaper == father)
                reaper = child_reaper;

        /*
         * There are only two places where our children can be:
         *
         * - in our child list
         * - in our ptraced child list
         *
         * Search them and reparent children.
         */
        list_for_each_safe(_p, _n, &father->children) {
                p = list_entry(_p,struct task_struct,sibling);
                if (father == p->real_parent) {
                        choose_new_parent(p, reaper, child_reaper);
                        reparent_thread(p, father, 0);
                } else {
                        ptrace_unlink (p);
                        if (p->state == TASK_ZOMBIE && p->exit_signal != -1)
                                do_notify_parent(p, p->exit_signal);
                }
        }
        list_for_each_safe(_p, _n, &father->ptrace_children) {
                p = list_entry(_p,struct task_struct,ptrace_list);
                choose_new_parent(p, reaper, child_reaper);
                reparent_thread(p, father, 1);
        }
}

/*
 * Send signals to all our closest relatives so that they know
 * to properly mourn us..
 */
static void exit_notify(void)
{
        struct task_struct *t;

        write_lock_irq(&tasklist_lock);

        /*
         * This does two things:
         *
         * A.  Make init inherit all the child processes
         * B.  Check to see if any process groups have become orphaned
         *      as a result of our exiting, and if they have any stopped
         *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
         */

        forget_original_parent(current);
        BUG_ON(!list_empty(&current->children));

        /*
         * Check to see if any process groups have become orphaned
         * as a result of our exiting, and if they have any stopped
         * jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
         *
         * Case i: Our father is in a different pgrp than we are
         * and we were the only connection outside, so our pgrp
         * is about to become orphaned.
         */
         
        t = current->parent;
        
        if ((t->pgrp != current->pgrp) &&
            (t->session == current->session) &&
            __will_become_orphaned_pgrp(current->pgrp, current) &&
            __has_stopped_jobs(current->pgrp)) {
                __kill_pg_info(SIGHUP, (void *)1, current->pgrp);
                __kill_pg_info(SIGCONT, (void *)1, current->pgrp);
        }

        /* Let father know we died 
         *
         * Thread signals are configurable, but you aren't going to use
         * that to send signals to arbitary processes. 
         * That stops right now.
         *
         * If the parent exec id doesn't match the exec id we saved
         * when we started then we know the parent has changed security
         * domain.
         *
         * If our self_exec id doesn't match our parent_exec_id then
         * we have changed execution domain as these two values started
         * the same after a fork.
         *      
         */
        
        if (current->exit_signal != SIGCHLD && current->exit_signal != -1 &&
            ( current->parent_exec_id != t->self_exec_id  ||
              current->self_exec_id != current->parent_exec_id) 
            && !capable(CAP_KILL))
                current->exit_signal = SIGCHLD;


        if (current->exit_signal != -1)
                do_notify_parent(current, current->exit_signal);

        current->state = TASK_ZOMBIE;
        /*
         * No need to unlock IRQs, we'll schedule() immediately
         * anyway. In the preemption case this also makes it
         * impossible for the task to get runnable again (thus
         * the "_raw_" unlock - to make sure we don't try to
         * preempt here).
         */
        _raw_write_unlock(&tasklist_lock);
}

NORET_TYPE void do_exit(long code)
{
        struct task_struct *tsk = current;

        if (in_interrupt())
                panic("Aiee, killing interrupt handler!");
        if (!tsk->pid)
                panic("Attempted to kill the idle task!");
        if (tsk->pid == 1)
                panic("Attempted to kill init!");
        tsk->flags |= PF_EXITING;
        del_timer_sync(&tsk->real_timer);

        if (unlikely(preempt_count()))
                printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
                                current->comm, current->pid,
                                preempt_count());

fake_volatile:
        acct_process(code);
        __exit_mm(tsk);

        sem_exit();
        __exit_files(tsk);
        __exit_fs(tsk);
        exit_namespace(tsk);
        exit_thread();

        if (current->leader)
                disassociate_ctty(1);

        put_exec_domain(tsk->thread_info->exec_domain);
        if (tsk->binfmt && tsk->binfmt->module)
                __MOD_DEC_USE_COUNT(tsk->binfmt->module);

        tsk->exit_code = code;
        exit_notify();
        preempt_disable();
        if (current->exit_signal == -1)
                release_task(current);
        schedule();
        BUG();
/*
 * In order to get rid of the "volatile function does return" message
 * I did this little loop that confuses gcc to think do_exit really
 * is volatile. In fact it's schedule() that is volatile in some
 * circumstances: when current->state = ZOMBIE, schedule() never
 * returns.
 *
 * In fact the natural way to do all this is to have the label and the
 * goto right after each other, but I put the fake_volatile label at
 * the start of the function just in case something /really/ bad
 * happens, and the schedule returns. This way we can try again. I'm
 * not paranoid: it's just that everybody is out to get me.
 */
        goto fake_volatile;
}

NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
        if (comp)
                complete(comp);
        
        do_exit(code);
}

asmlinkage long sys_exit(int error_code)
{
        do_exit((error_code&0xff)<<8);
}

/*
 * this kills every thread in the thread group. Note that any externally
 * wait4()-ing process will get the correct exit code - even if this 
 * thread is not the thread group leader.
 */
asmlinkage long sys_exit_group(int error_code)
{
        unsigned int exit_code = (error_code & 0xff) << 8;

        if (!list_empty(&current->thread_group)) {
                struct signal_struct *sig = current->sig;

                spin_lock_irq(&sig->siglock);
                if (sig->group_exit) {
                        spin_unlock_irq(&sig->siglock);

                        /* another thread was faster: */
                        do_exit(sig->group_exit_code);
                }
                sig->group_exit = 1;
                sig->group_exit_code = exit_code;
                __broadcast_thread_group(current, SIGKILL);
                spin_unlock_irq(&sig->siglock);
        }

        do_exit(exit_code);
}

static int eligible_child(pid_t pid, int options, task_t *p)
{
        if (pid > 0) {
                if (p->pid != pid)
                        return 0;
        } else if (!pid) {
                if (p->pgrp != current->pgrp)
                        return 0;
        } else if (pid != -1) {
                if (p->pgrp != -pid)
                        return 0;
        }

        /*
         * Do not consider detached threads that are
         * not ptraced:
         */
        if (p->exit_signal == -1 && !p->ptrace)
                return 0;

        /* Wait for all children (clone and not) if __WALL is set;
         * otherwise, wait for clone children *only* if __WCLONE is
         * set; otherwise, wait for non-clone children *only*.  (Note:
         * A "clone" child here is one that reports to its parent
         * using a signal other than SIGCHLD.) */
        if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
            && !(options & __WALL))
                return 0;
        /*
         * Do not consider thread group leaders that are
         * in a non-empty thread group:
         */
        if (current->tgid != p->tgid && delay_group_leader(p))
                return 2;

        if (security_ops->task_wait(p))
                return 0;

        return 1;
}

asmlinkage long sys_wait4(pid_t pid,unsigned int * stat_addr, int options, struct rusage * ru)
{
        int flag, retval;
        DECLARE_WAITQUEUE(wait, current);
        struct task_struct *tsk;

        if (options & ~(WNOHANG|WUNTRACED|__WNOTHREAD|__WCLONE|__WALL))
                return -EINVAL;

        add_wait_queue(&current->wait_chldexit,&wait);
repeat:
        flag = 0;
        current->state = TASK_INTERRUPTIBLE;
        read_lock(&tasklist_lock);
        tsk = current;
        do {
                struct task_struct *p;
                struct list_head *_p;
                int ret;

                list_for_each(_p,&tsk->children) {
                        p = list_entry(_p,struct task_struct,sibling);

                        ret = eligible_child(pid, options, p);
                        if (!ret)
                                continue;
                        flag = 1;

                        switch (p->state) {
                        case TASK_STOPPED:
                                if (!p->exit_code)
                                        continue;
                                if (!(options & WUNTRACED) && !(p->ptrace & PT_PTRACED))
                                        continue;
                                read_unlock(&tasklist_lock);

                                /* move to end of parent's list to avoid starvation */
                                write_lock_irq(&tasklist_lock);
                                remove_parent(p);
                                add_parent(p, p->parent);
                                write_unlock_irq(&tasklist_lock);
                                retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0; 
                                if (!retval && stat_addr) 
                                        retval = put_user((p->exit_code << 8) | 0x7f, stat_addr);
                                if (!retval) {
                                        p->exit_code = 0;
                                        retval = p->pid;
                                }
                                goto end_wait4;
                        case TASK_ZOMBIE:
                                /*
                                 * Eligible but we cannot release it yet:
                                 */
                                if (ret == 2)
                                        continue;
                                read_unlock(&tasklist_lock);
                                retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
                                if (!retval && stat_addr) {
                                        if (p->sig->group_exit)
                                                retval = put_user(p->sig->group_exit_code, stat_addr);
                                        else
                                                retval = put_user(p->exit_code, stat_addr);
                                }
                                if (retval)
                                        goto end_wait4; 
                                retval = p->pid;
                                if (p->real_parent != p->parent) {
                                        write_lock_irq(&tasklist_lock);
                                        __ptrace_unlink(p);
                                        do_notify_parent(p, SIGCHLD);
                                        write_unlock_irq(&tasklist_lock);
                                } else
                                        release_task(p);
                                goto end_wait4;
                        default:
                                continue;
                        }
                }
                if (!flag) {
                        list_for_each (_p,&tsk->ptrace_children) {
                                p = list_entry(_p,struct task_struct,ptrace_list);
                                if (!eligible_child(pid, options, p))
                                        continue;
                                flag = 1;
                                break;
                        }
                }
                if (options & __WNOTHREAD)
                        break;
                tsk = next_thread(tsk);
                if (tsk->sig != current->sig)
                        BUG();
        } while (tsk != current);
        read_unlock(&tasklist_lock);
        if (flag) {
                retval = 0;
                if (options & WNOHANG)
                        goto end_wait4;
                retval = -ERESTARTSYS;
                if (signal_pending(current))
                        goto end_wait4;
                schedule();
                goto repeat;
        }
        retval = -ECHILD;
end_wait4:
        current->state = TASK_RUNNING;
        remove_wait_queue(&current->wait_chldexit,&wait);
        return retval;
}

#if !defined(__alpha__) && !defined(__ia64__) && !defined(__arm__)

/*
 * sys_waitpid() remains for compatibility. waitpid() should be
 * implemented by calling sys_wait4() from libc.a.
 */
asmlinkage long sys_waitpid(pid_t pid,unsigned int * stat_addr, int options)
{
        return sys_wait4(pid, stat_addr, options, NULL);
}

#endif