context.c

含有完整TCP/IP PPP协议的嵌入式操作系统

/*
 * Copyright (C) 2001-2005 by egnite Software GmbH. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY EGNITE SOFTWARE GMBH AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL EGNITE
 * SOFTWARE GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * For additional information see http://www.ethernut.de/
 *
 */

/*
 * $Log: context.c,v $
 * Revision 1.3  2005/10/24 09:09:41  haraldkipp
 * Switch frame reduced.
 * NutThreadEntry included in the execution path.
 * The 'cc' globber had been removed from the context switching asm macro,
 * after Michael Fischer found out that this fixes a problem with optimized
 * compilation. Unfortunately, compiler optimized binaries still seem to
 * run unreliable.
 *
 * Revision 1.2  2005/08/02 17:46:45  haraldkipp
 * Major API documentation update.
 *
 * Revision 1.1  2005/07/26 18:10:48  haraldkipp
 * Moved from os/thread.c
 *
 * Revision 1.1  2005/05/27 17:16:40  drsung
 * Moved the file.
 *
 * Revision 1.4  2005/04/05 17:54:36  haraldkipp
 * Moved from user mode to system mode. Probably breaks the GBA port.
 *
 * Revision 1.3  2004/11/08 19:15:33  haraldkipp
 * Made assembly includes look nicer.
 * Changed mode from supervisory to user supervisory, which seems to work
 * with the GBA.
 * Skipped entry frame, because it simply confuses me. :-)
 *
 * Revision 1.2  2004/09/08 10:19:31  haraldkipp
 * Tyou's support for the ARM7
 *
 * Revision 1.1  2004/03/16 16:48:46  haraldkipp
 * Added Jan Dubiec's H8/300 port.
 *
 * Revision 1.2  2004/02/18 16:32:48  drsung
 * Bugfix in NutThreadCreate. Thanks to Mike Cornelius.
 *
 * Revision 1.1  2004/02/01 18:49:48  haraldkipp
 * Added CPU family support
 *
 */

#include <cfg/os.h>

#include <string.h>

#include <sys/atom.h>
#include <sys/heap.h>
#include <sys/thread.h>

/*!
 * \addtogroup xgNutArchArmOsContext
 */
/*@{*/


/*!
 * \brief ARM7TDMI GCC context switch frame layout.
 *
 * This is the layout of the stack after a thread's context has been
 * switched-out. The stack pointer is stored in the thread info and
 * points to this structure.
 */
typedef struct {
    u_long csf_cpsr;
    u_long csf_r4;
    u_long csf_r5;
    u_long csf_r6;
    u_long csf_r7;
    u_long csf_r8;
    u_long csf_r9;
    u_long csf_r10;
    u_long csf_r11;             /* AKA fp */
    u_long csf_lr;
} SWITCHFRAME;

/*!
 * \brief Thread entry frame layout.
 *
 * This is the stack layout being build to enter a new thread.
 */
typedef struct {
    u_long cef_r0;
    u_long cef_pc;
} ENTERFRAME;

/*!
 * \brief Enter a new thread.
 */
static void NutThreadEntry(void) __attribute__ ((naked));
void NutThreadEntry(void)
{
    /* Load argument in r0 and jump to thread entry. */
    asm volatile ("ldmfd   sp!, {r0, pc}");
}


/*!
 * \brief Switch to another thread.
 *
 * Stop the current thread, saving its context. Then start the
 * one with the highest priority, which is ready to run.
 *
 * Application programs typically do not call this function.
 *
 * \note CPU interrupts must be disabled before calling this function.
 *
 */
void NutThreadSwitch(void) __attribute__ ((naked));
void NutThreadSwitch(void)
{
    /* Save CPU context. */
    asm volatile (              /* */
                     "@ Save context\n\t"       /* */
                     "stmfd   sp!, {r4-r11, lr}\n\t"    /* Save registers. */
                     "mrs     r4, cpsr\n\t"     /* Save status. */
                     "stmfd   sp!, {r4}\n\t"    /* */
                     "str     sp, %0"   /* Save stack pointer. */
                     ::"m" (runningThread->td_sp)       /* */
        );

    /* Entry point for newly created threads. */
    asm volatile (".global thread_start\n" "thread_start:");

    /* Select thread on top of the run queue. */
    runningThread = runQueue;
    runningThread->td_state = TDS_RUNNING;

    /* Restore context. */
    __asm__ __volatile__(       /* */
                            "@ Load context\n\t"        /* */
                            "ldr     sp, %0\n\t"        /* Restore stack pointer. */
                            "ldmfd   sp!, {r4}\n\t"     /* Get saved status... */
                            "bic     r4, r4, #0xC0" "\n\t"      /* ...enable interrupts */
                            "msr     spsr, r4\n\t"      /* ...and save in spsr. */
                            "ldmfd   sp!, {r4-r11, lr}\n\t"     /* Restore registers. */
                            "movs    pc, lr"    /* Restore status and return. */
                            ::"m"(runningThread->td_sp) /* */
        );
}

/*!
 * \brief Create a new thread.
 *
 * If the current thread's priority is lower or equal than the default
 * priority (64), then the current thread is stopped and the new one
 * is started.
 *
 * \param name      String containing the symbolic name of the new thread,
 *                  up to 8 characters long.
 * \param fn        The thread's entry point, typically created by the
 *                  THREAD macro.
 * \param arg       Argument pointer passed to the new thread.
 * \param stackSize Number of bytes of the stack space allocated for
 *                  the new thread.
 *
 * \note The thread must run in ARM mode. Thumb mode is not supported.
 *
 * \return Pointer to the NUTTHREADINFO structure or 0 to indicate an
 *         error.
 */
HANDLE NutThreadCreate(u_char * name, void (*fn) (void *), void *arg, size_t stackSize)
{
    u_char *threadMem;
    SWITCHFRAME *sf;
    ENTERFRAME *ef;
    NUTTHREADINFO *td;

    /*
     * Allocate stack and thread info structure in one block.
     * We sill setup the following layout:
     *
     * Upper memory addresses.
     *
     *              +--------------------+
     *              I                    I
     *              I   NUTTHREADINFO    I
     *              I                    I
     * td ->        +-----+--------------+ <- Stack top
     *              I     I              I
     *              I  T  I   ENTERFRAME I
     *              I  H  I              I
     * ef ->        I  R  +--------------+
     *              I  E  I              I    ^
     *              I  A  I  SWITCHFRAME I    I
     *              I  D  I              I    I  pop moves up
     * sf ->        I     +--------------+ <- Initial stack pointer
     *              I  S  I              I    I  push moves down
     *              I  T  I Application  I    I
     *              I  A  I Stack        I    V
     *              I  C  I              I
     *              I  K  I              I
     * threadMem -> +-----+--------------+ <- Stack bottom
     *
     * Lower memory addresses.
     */
    if ((threadMem = NutHeapAlloc(stackSize + sizeof(NUTTHREADINFO))) == 0) {
        return 0;
    }
    td = (NUTTHREADINFO *) (threadMem + stackSize);
    ef = (ENTERFRAME *) ((uptr_t) td - sizeof(ENTERFRAME));
    sf = (SWITCHFRAME *) ((uptr_t) ef - sizeof(SWITCHFRAME));

    /* 
     * Set predefined values at the stack bottom. May be used to detect
     * stack overflows.
     */
    *((u_long *) threadMem) = DEADBEEF;
    *((u_long *) (threadMem + 4)) = DEADBEEF;
    *((u_long *) (threadMem + 8)) = DEADBEEF;
    *((u_long *) (threadMem + 12)) = DEADBEEF;

    /*
     * Setup the entry frame to simulate C function entry.
     */
    ef->cef_pc = (uptr_t) fn;
    ef->cef_r0 = (uptr_t) arg;

    /*
     * Setup the switch frame.
     */
    sf->csf_lr = (uptr_t) NutThreadEntry;
    sf->csf_cpsr = I_BIT | F_BIT | ARM_MODE_SVC;

    /*
     * Initialize the thread info structure and insert it into the 
     * thread list and the run queue.
     */
    memcpy(td->td_name, name, sizeof(td->td_name) - 1);
    td->td_name[sizeof(td->td_name) - 1] = 0;
    td->td_state = TDS_READY;
    td->td_sp = (uptr_t) sf;
    td->td_priority = 64;
    td->td_memory = threadMem;
    td->td_timer = 0;
    td->td_queue = 0;

    NutEnterCritical();
    td->td_next = nutThreadList;
    nutThreadList = td;
    NutThreadAddPriQueue(td, (NUTTHREADINFO **) & runQueue);

    /*
     * If no thread is running, then this is the first thread ever 
     * created. In Nut/OS, the idle thread is created first.
     */
    if (runningThread == 0) {
        /* This will never return. */
        asm volatile ("\n\tb thread_start\n\t");
    }

    /*
     * If current context is not in front of the run queue (highest 
     * priority), then switch to the thread in front.
     */
    if (runningThread != runQueue) {
        runningThread->td_state = TDS_READY;
        NutThreadSwitch();
    }
    NutExitCritical();

    return td;
}

/*@}*/