int open_files, nfds, size, i, error = 0;	/*	 * A background process may not have any files ...	 */	oldf = current->files;	if (!oldf)		goto out;	if (clone_flags & CLONE_FILES) {		atomic_inc(&oldf->count);		goto out;	}	tsk->files = NULL;	error = -ENOMEM;	newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);	if (!newf) 		goto out;	atomic_set(&newf->count, 1);	newf->file_lock	    = RW_LOCK_UNLOCKED;	newf->next_fd	    = 0;	newf->max_fds	    = NR_OPEN_DEFAULT;	newf->max_fdset	    = __FD_SETSIZE;	newf->close_on_exec = &newf->close_on_exec_init;	newf->open_fds	    = &newf->open_fds_init;	newf->fd	    = &newf->fd_array[0];	/* We don't yet have the oldf readlock, but even if the old           fdset gets grown now, we'll only copy up to "size" fds */	size = oldf->max_fdset;	if (size > __FD_SETSIZE) {		newf->max_fdset = 0;		write_lock(&newf->file_lock);		error = expand_fdset(newf, size-1);		write_unlock(&newf->file_lock);		if (error)			goto out_release;	}	read_lock(&oldf->file_lock);	open_files = count_open_files(oldf, size);	/*	 * Check whether we need to allocate a larger fd array.	 * Note: we're not a clone task, so the open count won't	 * change.	 */	nfds = NR_OPEN_DEFAULT;	if (open_files > nfds) {		read_unlock(&oldf->file_lock);		newf->max_fds = 0;		write_lock(&newf->file_lock);		error = expand_fd_array(newf, open_files-1);		write_unlock(&newf->file_lock);		if (error) 			goto out_release;		nfds = newf->max_fds;		read_lock(&oldf->file_lock);	}	old_fds = oldf->fd;	new_fds = newf->fd;	memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8);	memcpy(newf->close_on_exec->fds_bits, oldf->close_on_exec->fds_bits, open_files/8);	for (i = open_files; i != 0; i--) {		struct file *f = *old_fds++;		if (f)			get_file(f);		*new_fds++ = f;	}	read_unlock(&oldf->file_lock);	/* compute the remainder to be cleared */	size = (newf->max_fds - open_files) * sizeof(struct file *);	/* This is long word aligned thus could use a optimized version */ 	memset(new_fds, 0, size); 	if (newf->max_fdset > open_files) {		int left = (newf->max_fdset-open_files)/8;		int start = open_files / (8 * sizeof(unsigned long));				memset(&newf->open_fds->fds_bits[start], 0, left);		memset(&newf->close_on_exec->fds_bits[start], 0, left);	}	tsk->files = newf;	error = 0;out:	return error;out_release:	free_fdset (newf->close_on_exec, newf->max_fdset);	free_fdset (newf->open_fds, newf->max_fdset);	kmem_cache_free(files_cachep, newf);	goto out;}static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk){	struct signal_struct *sig;	if (clone_flags & CLONE_SIGHAND) {		atomic_inc(&current->sig->count);		return 0;	}	sig = kmem_cache_alloc(sigact_cachep, GFP_KERNEL);	tsk->sig = sig;	if (!sig)		return -1;	spin_lock_init(&sig->siglock);	atomic_set(&sig->count, 1);	memcpy(tsk->sig->action, current->sig->action, sizeof(tsk->sig->action));	return 0;}static inline void copy_flags(unsigned long clone_flags, struct task_struct *p){	unsigned long new_flags = p->flags;	new_flags &= ~(PF_SUPERPRIV | PF_USEDFPU);	new_flags |= PF_FORKNOEXEC;	if (!(clone_flags & CLONE_PTRACE))		p->ptrace = 0;	p->flags = new_flags;}static inline int fork_traceflag (unsigned clone_flags){	if (clone_flags & CLONE_UNTRACED)		return 0;	else if (clone_flags & CLONE_VFORK) {		if (current->ptrace & PT_TRACE_VFORK)			return PTRACE_EVENT_VFORK;	} else if ((clone_flags & CSIGNAL) != SIGCHLD) {		if (current->ptrace & PT_TRACE_CLONE)			return PTRACE_EVENT_CLONE;	} else if (current->ptrace & PT_TRACE_FORK)		return PTRACE_EVENT_FORK;	return 0;}/* *  Ok, this is the main fork-routine. It copies the system process * information (task[nr]) and sets up the necessary registers. It also * copies the data segment in its entirety.  The "stack_start" and * "stack_top" arguments are simply passed along to the platform * specific copy_thread() routine.  Most platforms ignore stack_top. * For an example that's using stack_top, see * arch/ia64/kernel/process.c. */int do_fork(unsigned long clone_flags, unsigned long stack_start,	    struct pt_regs *regs, unsigned long stack_size){	int retval;	struct task_struct *p;	struct completion vfork;	int trace = 0;	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))		return -EINVAL;	retval = -EPERM;	if (unlikely(current->ptrace)) {		trace = fork_traceflag (clone_flags);		if (trace)			clone_flags |= CLONE_PTRACE;	}	/* 	 * CLONE_PID is only allowed for the initial SMP swapper	 * calls	 */	if (clone_flags & CLONE_PID) {		if (current->pid)			goto fork_out;	}	retval = -ENOMEM;	p = alloc_task_struct();	if (!p)		goto fork_out;	*p = *current;	retval = -EAGAIN;	/*	 * Check if we are over our maximum process limit, but be sure to	 * exclude root. This is needed to make it possible for login and	 * friends to set the per-user process limit to something lower	 * than the amount of processes root is running. -- Rik	 */	if (atomic_read(&p->user->processes) >= p->rlim[RLIMIT_NPROC].rlim_cur	              && !capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE))		goto bad_fork_free;	atomic_inc(&p->user->__count);	atomic_inc(&p->user->processes);	/*	 * Counter increases are protected by	 * the kernel lock so nr_threads can't	 * increase under us (but it may decrease).	 */	if (nr_threads >= max_threads)		goto bad_fork_cleanup_count;		get_exec_domain(p->exec_domain);	if (p->binfmt && p->binfmt->module)		__MOD_INC_USE_COUNT(p->binfmt->module);#ifdef CONFIG_PREEMPT	/*	 * Continue with preemption disabled as part of the context	 * switch, so start with preempt_count set to 1.         */	p->preempt_count = 1;#endif	p->did_exec = 0;	p->swappable = 0;	p->state = TASK_UNINTERRUPTIBLE;	copy_flags(clone_flags, p);	p->pid = get_pid(clone_flags);	if (p->pid == 0 && current->pid != 0)		goto bad_fork_cleanup;	INIT_LIST_HEAD(&p->run_list);	p->p_cptr = NULL;	init_waitqueue_head(&p->wait_chldexit);	p->vfork_done = NULL;	if (clone_flags & CLONE_VFORK) {		p->vfork_done = &vfork;		init_completion(&vfork);	}	spin_lock_init(&p->alloc_lock);	p->sigpending = 0;	init_sigpending(&p->pending);	p->it_real_value = p->it_virt_value = p->it_prof_value = 0;	p->it_real_incr = p->it_virt_incr = p->it_prof_incr = 0;	init_timer(&p->real_timer);	p->real_timer.data = (unsigned long) p;	p->leader = 0;		/* session leadership doesn't inherit */	p->tty_old_pgrp = 0;	p->times.tms_utime = p->times.tms_stime = 0;	p->times.tms_cutime = p->times.tms_cstime = 0;#ifdef CONFIG_SMP	{		int i;		/* ?? should we just memset this ?? */		for(i = 0; i < smp_num_cpus; i++)			p->per_cpu_utime[cpu_logical_map(i)] =				p->per_cpu_stime[cpu_logical_map(i)] = 0;		spin_lock_init(&p->sigmask_lock);	}#endif	p->array = NULL;	p->lock_depth = -1;		/* -1 = no lock */	p->start_time = jiffies;	INIT_LIST_HEAD(&p->local_pages);	retval = -ENOMEM;	/* copy all the process information */	if (copy_files(clone_flags, p))		goto bad_fork_cleanup;	if (copy_fs(clone_flags, p))		goto bad_fork_cleanup_files;	if (copy_sighand(clone_flags, p))		goto bad_fork_cleanup_fs;	if (copy_mm(clone_flags, p))		goto bad_fork_cleanup_sighand;	if (copy_namespace(clone_flags, p))		goto bad_fork_cleanup_mm;	retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);	if (retval)		goto bad_fork_cleanup_namespace;	p->semundo = NULL;		/* Our parent execution domain becomes current domain	   These must match for thread signalling to apply */	   	p->parent_exec_id = p->self_exec_id;	/* ok, now we should be set up.. */	p->swappable = 1;	p->exit_signal = clone_flags & CSIGNAL;	p->pdeath_signal = 0;	/*	 * Share the timeslice between parent and child, thus the	 * total amount of pending timeslices in the system doesnt change,	 * resulting in more scheduling fairness.	 */	__cli();	if (!current->time_slice)		BUG();	p->time_slice = (current->time_slice + 1) >> 1;	current->time_slice >>= 1;	p->first_time_slice = 1;	if (!current->time_slice) {		/*		 * This case is rare, it happens when the parent has only		 * a single jiffy left from its timeslice. Taking the		 * runqueue lock is not a problem.		 */		current->time_slice = 1;		scheduler_tick(0,0);	}	p->sleep_timestamp = jiffies;	__sti();	/*	 * Ok, add it to the run-queues and make it	 * visible to the rest of the system.	 *	 * Let it rip!	 */	retval = p->pid;	p->tgid = retval;	INIT_LIST_HEAD(&p->thread_group);	/* Need tasklist lock for parent etc handling! */	write_lock_irq(&tasklist_lock);	/* CLONE_PARENT re-uses the old parent */	p->p_opptr = current->p_opptr;	p->p_pptr = current->p_pptr;	if (!(clone_flags & CLONE_PARENT)) {		p->p_opptr = current;		if (!(p->ptrace & PT_PTRACED))			p->p_pptr = current;	}	if (clone_flags & CLONE_THREAD) {		p->tgid = current->tgid;		list_add(&p->thread_group, &current->thread_group);	}	SET_LINKS(p);	hash_pid(p);	nr_threads++;	write_unlock_irq(&tasklist_lock);	if (p->ptrace & PT_PTRACED)		send_sig(SIGSTOP, p, 1);	/* Trace the event  */	TRACE_PROCESS(TRACE_EV_PROCESS_FORK, retval, 0);	wake_up_forked_process(p);	/* do this last */	++total_forks;	if (unlikely(trace)) {		current->ptrace_message = (unsigned long) p->pid;		ptrace_notify ((trace << 8) | SIGTRAP);	}	if (clone_flags & CLONE_VFORK)		wait_for_completion(&vfork);	else		/*		 * Let the child process run first, to avoid most of the		 * COW overhead when the child exec()s afterwards.		 */		current->need_resched = 1;fork_out:	return retval;bad_fork_cleanup_namespace:	exit_namespace(p);bad_fork_cleanup_mm:	exit_mm(p);bad_fork_cleanup_sighand:	exit_sighand(p);bad_fork_cleanup_fs:	exit_fs(p); /* blocking */bad_fork_cleanup_files:	exit_files(p); /* blocking */bad_fork_cleanup:	put_exec_domain(p->exec_domain);	if (p->binfmt && p->binfmt->module)		__MOD_DEC_USE_COUNT(p->binfmt->module);bad_fork_cleanup_count:	atomic_dec(&p->user->processes);	free_uid(p->user);bad_fork_free:	free_task_struct(p);	goto fork_out;}/* SLAB cache for signal_struct structures (tsk->sig) */kmem_cache_t *sigact_cachep;/* SLAB cache for files_struct structures (tsk->files) */kmem_cache_t *files_cachep;/* SLAB cache for fs_struct structures (tsk->fs) */kmem_cache_t *fs_cachep;/* SLAB cache for vm_area_struct structures */kmem_cache_t *vm_area_cachep;/* SLAB cache for mm_struct structures (tsk->mm) */kmem_cache_t *mm_cachep;void __init proc_caches_init(void){	sigact_cachep = kmem_cache_create("signal_act",			sizeof(struct signal_struct), 0,			SLAB_HWCACHE_ALIGN, NULL, NULL);	if (!sigact_cachep)		panic("Cannot create signal action SLAB cache");	files_cachep = kmem_cache_create("files_cache", 			 sizeof(struct files_struct), 0, 			 SLAB_HWCACHE_ALIGN, NULL, NULL);	if (!files_cachep) 		panic("Cannot create files SLAB cache");	fs_cachep = kmem_cache_create("fs_cache", 			 sizeof(struct fs_struct), 0, 			 SLAB_HWCACHE_ALIGN, NULL, NULL);	if (!fs_cachep) 		panic("Cannot create fs_struct SLAB cache"); 	vm_area_cachep = kmem_cache_create("vm_area_struct",			sizeof(struct vm_area_struct), 0,			SLAB_HWCACHE_ALIGN, NULL, NULL);	if(!vm_area_cachep)		panic("vma_init: Cannot alloc vm_area_struct SLAB cache");	mm_cachep = kmem_cache_create("mm_struct",			sizeof(struct mm_struct), 0,			SLAB_HWCACHE_ALIGN, NULL, NULL);	if(!mm_cachep)		panic("vma_init: Cannot alloc mm_struct SLAB cache");}