VxWorks romStar函数分析

以下对romStart进行了必要的删减，主要去掉了一些预编译选项。

void romStart
    (
    FAST int startType        /* start type */
    )
{
    volatile                  /* to force absolute adressing */
FUNCPTR absEntry;        /* to avoid PC Relative Jump Subroutine */
$$<<
       注释：volatile关键字的作用是使编译器不对被指定的变量做优化，这样可以确保该变量每次被取到新的值。Volatile经常用来修饰全局的或者静态的或者在多任务环境下允许被改变的变量。
>>$$
   /*
     * Copy from ROM to RAM, minus the compressed image
     * if compressed boot ROM which relies on binArray
     * appearing last in DATA segment.
     */
      
    ((FUNCPTR)ROM_OFFSET(copyLongs)) (ROM_TEXT_ADRS, (UINT)romInit,
              ((UINT)binArrayStart - (UINT)romInit) / sizeof (long));
$$<<
              注释：该段代码将ROM中非压缩的部分拷贝到RAM中。ROM_OFFSET(copyLongs)计算出copyLongs在ROM中的地址，然后调有该函数。BinArrayStart地址以后装的是压缩的代码和数据。
>>$$
    /* clear all memory if cold booting */
  
    if (startType & BOOT_CLEAR)
       {
$$<<
              注释：如果是冷启动则将0－（romInit - STACK_SAVE）以及binArrayStart之后的RAM清0。
>>$$
       fillLongs ((UINT *)(SYS_MEM_BOTTOM),
              ((UINT)romInit - STACK_SAVE - (UINT)SYS_MEM_BOTTOM) /
             sizeof(long), 0);

       fillLongs ((UINT *)binArrayStart,
              ((UINT)SYS_MEM_TOP - (UINT)binArrayStart) / sizeof (long), 0);

       /*
        * Ensure the boot line is null. This is necessary for those
        * targets whose boot line is excluded from cleaning.
        */
$$<<
              注释：将BOOT_LINE_ADRS中的内容清0，保证bootline的正确。
>>$$
       *(BOOT_LINE_ADRS) = EOS;
       }
      
        /* jump to VxWorks entry point (after uncompressing) */
    {
$$<<
              注释：将压缩内容解压缩到RAM_DST_ADRS，即RAM_HIGH_ADRS。
>>$$
    if (UNCMP_RTN ((UCHAR *)ROM_OFFSET(binArrayStart),
                   (UCHAR *)RAM_DST_ADRS, &binArrayEnd - binArrayStart) != OK)
           return;              /* if we return then ROM's will halt */
    absEntry = (FUNCPTR)RAM_DST_ADRS;                     /* compressedEntry () */
      
}
$$<<
       注释：转移到RAM中执行。
>>$$
    (absEntry) (startType);
}