cloning.c

C++ SOCKET 类

/***************************************************************************
                          cloning.c  -  description
                             -------------------
    begin                : Mon Jan 31 2000
    copyright            : (C) 2000 by 豶n E. Hansen
    email                : [e-mail]
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   * 
 *                                                                         *
 ***************************************************************************/


#include <sched.h>
#include <unistd.h>
#include <malloc.h>
#include <errno.h>

#include "cloning.h"

//
// There is a huge problem with the use of CLONE under linux,
// and it has to do with the use of the STACK.  In this version
// the stack pages are memory pages, taken by the user.  The
// stack, being top-down ordered in ix86 systems, can easyly run
// over the users memory space.
//
beginthread(int (*_fn)(void *),void *_sp,void *_arg)
{
  char *sp = _sp;
  int size=8*STACK_PAGE_SIZE;
  int pid;

  if ( sp == NULL ) {
    sp   = malloc(size);
    if( sp )
      sp += size;
  }
  if (sp == NULL)
    return -(errno = ENOMEM);
  pid = clone(_fn, sp, CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND, _arg);
  if (pid < 0) {
    if ( _sp == NULL )
      free(sp);
    sp = NULL;
  }
  return pid;
}