source: trunk/kLdr/kLdr.c@ 3232

/* $Id: kLdr.c 2944 2007-01-13 15:55:40Z bird $ */
/** @file
 *
 * kLdr - The Dynamic Loader.
 *
 * Copyright (c) 2006 knut st. osmundsen <bird@anduin.net>
 *
 *
 * This file is part of kLdr.
 *
 * kLdr 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.
 *
 * kLdr is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with kLdr; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

/** @mainpage   kLdr - The Dynamic Loader
 *
 * The purpose of kLdr is to provide a generic interface for querying
 * information about and loading executable image modules.
 *
 * kLdr defines the term executable image to include all kinds of files that contains
 * binary code that can be executed on a CPU - linker objects (OBJs/Os), shared
 * objects (SOs), dynamic link libraries (DLLs), executables (EXEs), and all kinds
 * of kernel modules / device drivers (SYSs).
 *
 * kLdr provides two types of services:
 *      -# Inspect or/and load individual modules (kLdrMod).
 *      -# Work as a dynamic loader - construct and maintain an address space (kLdrDy).
 *
 * The kLdrMod API works on KLDRMOD structures where all the internals are exposed, while
 * the kLdrDy API works opque KLDRDY structures. KLDRDY are in reality simple wrappers
 * around KLDRMOD with some extra linking and attributes.
 *
 */




/*******************************************************************************
*   Header Files                                                               *
*******************************************************************************/
#include "kLdr.h"
#include "kLdrHlp.h"
#include "kLdrInternal.h"


/*******************************************************************************
*   Global Variables                                                           *
*******************************************************************************/
/** Flag indicating whether we've initialized the loader or not.
 *
 * 0 if not initialized.
 * -1 if we're initializing or terminating.
 * 1 if we've successfully initialized it.
 * -2 if initialization failed.
 */
static int volatile g_fInitialized;



/**
 * Initializes the loader.
 * @returns 0 on success, non-zero OS status code on failure.
 */
int kldrInit(void)
{
    int rc;

    /* check we're already good. */
    if (g_fInitialized == 1)
        return 0;

    /* a tiny serialization effort. */
    for (;;)
    {
        if (g_fInitialized == 1)
            return 0;
        if (g_fInitialized == -2)
            return -1;
        /** @todo atomic test and set if we care. */
        if (g_fInitialized == 0)
        {
            g_fInitialized = -1;
            break;
        }
        kldrHlpSleep(1);
    }

    /*
     * Do the initialization.
     */
    rc = kldrHlpHeapInit();
    if (!rc)
    {
        rc = kldrHlpSemInit();
        if (!rc)
        {
            rc = kldrDyldInit();
            if (!rc)
            {
                g_fInitialized = 1;
                return 0;
            }
            kldrHlpSemTerm();
        }
        kldrHlpHeapTerm();
    }
    g_fInitialized = -2;
    return rc;
}


/**
 * Terminates the loader.
 */
void kldrTerm(void)
{
    /* can't terminate unless it's initialized. */
    if (g_fInitialized != 1)
        return;
    g_fInitialized = -1;

    /*
     * Do the termination.
     */
    kldrHlpSemTerm();
    kldrHlpHeapTerm();

    /* done */
    g_fInitialized = 0;
}