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

#undef DEBUG_PROC_TREE

#include <linux/wait.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/resource.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/malloc.h>

#include <asm/segment.h>
extern void sem_exit (void);

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

static int generate(unsigned long sig, struct task_struct * p)
{
        unsigned long mask = 1 << (sig-1);
        struct sigaction * sa = sig + p->sigaction - 1;

        /* always generate signals for traced processes ??? */
        if (p->flags & PF_PTRACED) {
                p->signal |= mask;
                return 1;
        }
        /* don't bother with ignored signals (but SIGCHLD is special) */
        if (sa->sa_handler == SIG_IGN && sig != SIGCHLD)
                return 0;
        /* some signals are ignored by default.. (but SIGCONT already did its deed) */
        if ((sa->sa_handler == SIG_DFL) &&
            (sig == SIGCONT || sig == SIGCHLD || sig == SIGWINCH))
                return 0;
        p->signal |= mask;
        return 1;
}

int send_sig(unsigned long sig,struct task_struct * p,int priv)
{
        if (!p || sig > 32)
                return -EINVAL;
        if (!priv && ((sig != SIGCONT) || (current->session != p->session)) &&
            (current->euid != p->euid) && (current->euid != p->uid) && !suser())
                return -EPERM;
        if (!sig)
                return 0;
        /*
         * Forget it if the process is already zombie'd.
         */
        if (p->state == TASK_ZOMBIE)
                return 0;
        if ((sig == SIGKILL) || (sig == SIGCONT)) {
                if (p->state == TASK_STOPPED)
                        p->state = TASK_RUNNING;
                p->exit_code = 0;
                p->signal &= ~( (1<<(SIGSTOP-1)) | (1<<(SIGTSTP-1)) |
                                (1<<(SIGTTIN-1)) | (1<<(SIGTTOU-1)) );
        }
        /* Depends on order SIGSTOP, SIGTSTP, SIGTTIN, SIGTTOU */
        if ((sig >= SIGSTOP) && (sig <= SIGTTOU)) 
                p->signal &= ~(1<<(SIGCONT-1));
        /* Actually generate the signal */
        generate(sig,p);
        return 0;
}

void notify_parent(struct task_struct * tsk)
{
        if (tsk->p_pptr == task[1])
                tsk->exit_signal = SIGCHLD;
        send_sig(tsk->exit_signal, tsk->p_pptr, 1);
        wake_up_interruptible(&tsk->p_pptr->wait_chldexit);
}

void release(struct task_struct * p)
{
        int i;

        if (!p)
                return;
        if (p == current) {
                printk("task releasing itself\n");
                return;
        }
        for (i=1 ; i<NR_TASKS ; i++)
                if (task[i] == p) {
                        nr_tasks--;
                        task[i] = NULL;
                        REMOVE_LINKS(p);
                        if (STACK_MAGIC != *(unsigned long *)p->kernel_stack_page)
                                printk(KERN_ALERT "release: %s kernel stack corruption. Aiee\n", p->comm);
                        free_page(p->kernel_stack_page);
                        free_page((long) p);
                        return;
                }
        panic("trying to release non-existent task");
}

#ifdef DEBUG_PROC_TREE
/*
 * Check to see if a task_struct pointer is present in the task[] array
 * Return 0 if found, and 1 if not found.
 */
int bad_task_ptr(struct task_struct *p)
{
        int     i;

        if (!p)
                return 0;
        for (i=0 ; i<NR_TASKS ; i++)
                if (task[i] == p)
                        return 0;
        return 1;
}
        
/*
 * This routine scans the pid tree and makes sure the rep invariant still
 * holds.  Used for debugging only, since it's very slow....
 *
 * It looks a lot scarier than it really is.... we're doing nothing more
 * than verifying the doubly-linked list found in p_ysptr and p_osptr, 
 * and checking it corresponds with the process tree defined by p_cptr and 
 * p_pptr;
 */
void audit_ptree(void)
{
        int     i;

        for (i=1 ; i<NR_TASKS ; i++) {
                if (!task[i])
                        continue;
                if (bad_task_ptr(task[i]->p_pptr))
                        printk("Warning, pid %d's parent link is bad\n",
                                task[i]->pid);
                if (bad_task_ptr(task[i]->p_cptr))
                        printk("Warning, pid %d's child link is bad\n",
                                task[i]->pid);
                if (bad_task_ptr(task[i]->p_ysptr))
                        printk("Warning, pid %d's ys link is bad\n",
                                task[i]->pid);
                if (bad_task_ptr(task[i]->p_osptr))
                        printk("Warning, pid %d's os link is bad\n",
                                task[i]->pid);
                if (task[i]->p_pptr == task[i])
                        printk("Warning, pid %d parent link points to self\n",
                                task[i]->pid);
                if (task[i]->p_cptr == task[i])
                        printk("Warning, pid %d child link points to self\n",
                                task[i]->pid);
                if (task[i]->p_ysptr == task[i])
                        printk("Warning, pid %d ys link points to self\n",
                                task[i]->pid);
                if (task[i]->p_osptr == task[i])
                        printk("Warning, pid %d os link points to self\n",
                                task[i]->pid);
                if (task[i]->p_osptr) {
                        if (task[i]->p_pptr != task[i]->p_osptr->p_pptr)
                                printk(
                        "Warning, pid %d older sibling %d parent is %d\n",
                                task[i]->pid, task[i]->p_osptr->pid,
                                task[i]->p_osptr->p_pptr->pid);
                        if (task[i]->p_osptr->p_ysptr != task[i])
                                printk(
                "Warning, pid %d older sibling %d has mismatched ys link\n",
                                task[i]->pid, task[i]->p_osptr->pid);
                }
                if (task[i]->p_ysptr) {
                        if (task[i]->p_pptr != task[i]->p_ysptr->p_pptr)
                                printk(
                        "Warning, pid %d younger sibling %d parent is %d\n",
                                task[i]->pid, task[i]->p_osptr->pid,
                                task[i]->p_osptr->p_pptr->pid);
                        if (task[i]->p_ysptr->p_osptr != task[i])
                                printk(
                "Warning, pid %d younger sibling %d has mismatched os link\n",
                                task[i]->pid, task[i]->p_ysptr->pid);
                }
                if (task[i]->p_cptr) {
                        if (task[i]->p_cptr->p_pptr != task[i])
                                printk(
                        "Warning, pid %d youngest child %d has mismatched parent link\n",
                                task[i]->pid, task[i]->p_cptr->pid);
                        if (task[i]->p_cptr->p_ysptr)
                                printk(
                        "Warning, pid %d youngest child %d has non-NULL ys link\n",
                                task[i]->pid, task[i]->p_cptr->pid);
                }
        }
}
#endif /* DEBUG_PROC_TREE */

/*
 * 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;
        int fallback;

        fallback = -1;
        for_each_task(p) {
                if (p->session <= 0)
                        continue;
                if (p->pgrp == pgrp)
                        return p->session;
                if (p->pid == pgrp)
                        fallback = p->session;
        }
        return fallback;
}

/*
 * kill_pg() sends a signal to a process group: this is what the tty
 * control characters do (^C, ^Z etc)
 */
int kill_pg(int pgrp, int sig, int priv)
{
        struct task_struct *p;
        int err,retval = -ESRCH;
        int found = 0;

        if (sig<0 || sig>32 || pgrp<=0)
                return -EINVAL;
        for_each_task(p) {
                if (p->pgrp == pgrp) {
                        if ((err = send_sig(sig,p,priv)) != 0)
                                retval = err;
                        else
                                found++;
                }
        }
        return(found ? 0 : retval);
}

/*
 * kill_sl() sends a signal to the session leader: this is used
 * to send SIGHUP to the controlling process of a terminal when
 * the connection is lost.
 */
int kill_sl(int sess, int sig, int priv)
{
        struct task_struct *p;
        int err,retval = -ESRCH;
        int found = 0;

        if (sig<0 || sig>32 || sess<=0)
                return -EINVAL;
        for_each_task(p) {
                if (p->session == sess && p->leader) {
                        if ((err = send_sig(sig,p,priv)) != 0)
                                retval = err;
                        else
                                found++;
                }
        }
        return(found ? 0 : retval);
}

int kill_proc(int pid, int sig, int priv)
{
        struct task_struct *p;

        if (sig<0 || sig>32)
                return -EINVAL;
        for_each_task(p) {
                if (p && p->pid == pid)
                        return send_sig(sig,p,priv);
        }
        return(-ESRCH);
}

/*
 * POSIX specifies that kill(-1,sig) is unspecified, but what we have
 * is probably wrong.  Should make it like BSD or SYSV.
 */
asmlinkage int sys_kill(int pid,int sig)
{
        int err, retval = 0, count = 0;

        if (!pid)
                return(kill_pg(current->pgrp,sig,0));
        if (pid == -1) {
                struct task_struct * p;
                for_each_task(p) {
                        if (p->pid > 1 && p != current) {
                                ++count;
                                if ((err = send_sig(sig,p,0)) != -EPERM)
                                        retval = err;
                        }
                }
                return(count ? retval : -ESRCH);
        }
        if (pid < 0) 
                return(kill_pg(-pid,sig,0));
        /* Normal kill */
        return(kill_proc(pid,sig,0));
}

/*
 * 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?"
 */
int is_orphaned_pgrp(int pgrp)
{
        struct task_struct *p;

        for_each_task(p) {
                if ((p->pgrp != pgrp) || 
                    (p->state == TASK_ZOMBIE) ||
                    (p->p_pptr->pid == 1))
                        continue;
                if ((p->p_pptr->pgrp != pgrp) &&
                    (p->p_pptr->session == p->session))
                        return 0;
        }
        return(1);      /* (sighing) "Often!" */
}

static int has_stopped_jobs(int pgrp)
{
        struct task_struct * p;

        for_each_task(p) {
                if (p->pgrp != pgrp)
                        continue;
                if (p->state == TASK_STOPPED)
                        return(1);
        }
        return(0);
}

static void forget_original_parent(struct task_struct * father)
{
        struct task_struct * p;

        for_each_task(p) {
                if (p->p_opptr == father)
                        if (task[1])
                                p->p_opptr = task[1];
                        else
                                p->p_opptr = task[0];
        }
}

static void exit_files(void)
{
        int i;

        for (i=0 ; i<NR_OPEN ; i++)
                if (current->files->fd[i])
                        sys_close(i);
}

static void exit_fs(void)
{
        iput(current->fs->pwd);
        current->fs->pwd = NULL;
        iput(current->fs->root);
        current->fs->root = NULL;
}

NORET_TYPE void do_exit(long code)
{
        struct task_struct *p;

        if (intr_count) {
                printk("Aiee, killing interrupt handler\n");
                intr_count = 0;
        }
fake_volatile:
        current->flags |= PF_EXITING;
        sem_exit();
        exit_mmap(current);
        free_page_tables(current);
        exit_files();
        exit_fs();
        exit_thread();
        forget_original_parent(current);
        /* 
         * 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 SIGUP 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.
         */
        if ((current->p_pptr->pgrp != current->pgrp) &&
            (current->p_pptr->session == current->session) &&
            is_orphaned_pgrp(current->pgrp) &&
            has_stopped_jobs(current->pgrp)) {
                kill_pg(current->pgrp,SIGHUP,1);
                kill_pg(current->pgrp,SIGCONT,1);
        }
        /* Let father know we died */
        notify_parent(current);
        
        /*
         * This loop 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)
         */
        while ((p = current->p_cptr) != NULL) {
                current->p_cptr = p->p_osptr;
                p->p_ysptr = NULL;
                p->flags &= ~(PF_PTRACED|PF_TRACESYS);
                if (task[1] && task[1] != current)
                        p->p_pptr = task[1];
                else
                        p->p_pptr = task[0];
                p->p_osptr = p->p_pptr->p_cptr;
                p->p_osptr->p_ysptr = p;
                p->p_pptr->p_cptr = p;
                if (p->state == TASK_ZOMBIE)
                        notify_parent(p);
                /*
                 * 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 != current->pgrp) &&
                    (p->session == current->session) &&
                    is_orphaned_pgrp(p->pgrp) &&
                    has_stopped_jobs(p->pgrp)) {
                        kill_pg(p->pgrp,SIGHUP,1);
                        kill_pg(p->pgrp,SIGCONT,1);
                }
        }
        if (current->leader)
                disassociate_ctty(1);
        if (last_task_used_math == current)
                last_task_used_math = NULL;
        current->state = TASK_ZOMBIE;
        current->exit_code = code;
        current->mm->rss = 0;
#ifdef DEBUG_PROC_TREE
        audit_ptree();
#endif
        if (current->exec_domain && current->exec_domain->use_count)
                (*current->exec_domain->use_count)--;
        if (current->binfmt && current->binfmt->use_count)
                (*current->binfmt->use_count)--;
        schedule();
/*
 * 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;
}

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

asmlinkage int sys_wait4(pid_t pid,unsigned long * stat_addr, int options, struct rusage * ru)
{
        int flag, retval;
        struct wait_queue wait = { current, NULL };
        struct task_struct *p;

        if (stat_addr) {
                flag = verify_area(VERIFY_WRITE, stat_addr, 4);
                if (flag)
                        return flag;
        }
        add_wait_queue(&current->wait_chldexit,&wait);
repeat:
        flag=0;
        for (p = current->p_cptr ; p ; p = p->p_osptr) {
                if (pid>0) {
                        if (p->pid != pid)
                                continue;
                } else if (!pid) {
                        if (p->pgrp != current->pgrp)
                                continue;
                } else if (pid != -1) {
                        if (p->pgrp != -pid)
                                continue;
                }
                /* wait for cloned processes iff the __WCLONE flag is set */
                if ((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
                        continue;
                flag = 1;
                switch (p->state) {
                        case TASK_STOPPED:
                                if (!p->exit_code)
                                        continue;
                                if (!(options & WUNTRACED) && !(p->flags & PF_PTRACED))
                                        continue;
                                if (stat_addr)
                                        put_fs_long((p->exit_code << 8) | 0x7f,
                                                stat_addr);
                                p->exit_code = 0;
                                if (ru != NULL)
                                        getrusage(p, RUSAGE_BOTH, ru);
                                retval = p->pid;
                                goto end_wait4;
                        case TASK_ZOMBIE:
                                current->cutime += p->utime + p->cutime;
                                current->cstime += p->stime + p->cstime;
                                current->mm->cmin_flt += p->mm->min_flt + p->mm->cmin_flt;
                                current->mm->cmaj_flt += p->mm->maj_flt + p->mm->cmaj_flt;
                                if (ru != NULL)
                                        getrusage(p, RUSAGE_BOTH, ru);
                                flag = p->pid;
                                if (stat_addr)
                                        put_fs_long(p->exit_code, stat_addr);
                                if (p->p_opptr != p->p_pptr) {
                                        REMOVE_LINKS(p);
                                        p->p_pptr = p->p_opptr;
                                        SET_LINKS(p);
                                        notify_parent(p);
                                } else
                                        release(p);
#ifdef DEBUG_PROC_TREE
                                audit_ptree();
#endif
                                retval = flag;
                                goto end_wait4;
                        default:
                                continue;
                }
        }
        if (flag) {
                retval = 0;
                if (options & WNOHANG)
                        goto end_wait4;
                current->state=TASK_INTERRUPTIBLE;
                schedule();
                current->signal &= ~(1<<(SIGCHLD-1));
                retval = -ERESTARTSYS;
                if (current->signal & ~current->blocked)
                        goto end_wait4;
                goto repeat;
        }
        retval = -ECHILD;
end_wait4:
        remove_wait_queue(&current->wait_chldexit,&wait);
        return retval;
}

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