Nucleus

/*
 * This file contains the clone() function/system call.  It creates a new task,
 * and copies most of the attributes from the parent task into it.
 */

#include <sys/sched.h>
#include <sys/types.h>
#include <nucleus/io.h>
#include <nucleus/task.h>
#include <nucleus/vfs.h>

/* Clone a task */
pid_t
clone(int flags)
{
	enter_critical_section();

	Task *parent = current, *child = new(&taskType), *tmp;
	pid_t tid = 0;

	if (flags & CLONE_THREAD) {
		flags |= CLONE_PARENT;
		flags |= CLONE_VM;
	}

	/* Clone parent's file system namespace */
	if (flags & CLONE_FS)
		child->fs = get(parent->fs);
	else
		child->fs = copy(parent->fs);

	/* Clone parent's files namespace */
	if (flags & CLONE_FILES)
		child->files = get(parent->files);
	else
		child->files = copy(parent->files);

	/* Clone parent's virtual memory namespace */
	if (flags & CLONE_VM)
		child->vm = get(parent->vm);
	else
		child->vm = copy(parent->vm);
	/* Copy stack */
	if (parent->stack)
		child->stack = copy(parent->stack);

	/* Clone parent's signals namespace */
	if (flags & CLONE_SIGHAND)
		child->signals = get(parent->signals);
	else
		child->signals = copy(parent->signals);

	/* Get executable file */
	if (parent->executable)
		child->executable = get(parent->executable);

	child->inSyscall = parent->inSyscall;

	/* After this, anything on the stack is desynchronised */
	child->pageDir = clone_dir();

	/* Split tasks here */
	asm volatile("mov %%esi, %0" : "=r" (child->esi));
	asm volatile("mov %%edi, %0" : "=r" (child->edi));
	asm volatile("mov %%ebx, %0" : "=r" (child->ebx));
	asm volatile("mov %%esp, %0" : "=r" (child->esp));
	asm volatile("mov %%ebp, %0" : "=r" (child->ebp));
	child->eip = (uintptr_t) &&end;
	enqueue_task(child);
	tid = child->tid;
	put(child);
	exit_critical_section();
end:
	return tid;
}