MmGetPhysicalAddress分析

代码如下：

PHYSICAL_ADDRESS
MmGetPhysicalAddress (
     IN PVOID BaseAddress
     )
{
    PMMPTE PointerPte;
    PHYSICAL_ADDRESS PhysicalAddress;

 //判断是否在[0x80000000,0xA0000000)中，如果是，这段内存被映射到物理内存中[0,20000000)，这段内存采用4MB大小的分页。

    if (MI_IS_PHYSICAL_ADDRESS(BaseAddress)) {
        PhysicalAddress.QuadPart = MI_CONVERT_PHYSICAL_TO_PFN (BaseAddress);
    } else {

        PointerPte = MiGetPteAddress(BaseAddress);

　　//如果PTE的内容为NULL，则不对应任何物理内存。

        if (PointerPte->u.Hard.Valid == 0) {
            KdPrint(("MM:MmGetPhysicalAddressFailed base address was %lx",
                      BaseAddress));
            ZERO_LARGE (PhysicalAddress);
            return PhysicalAddress;
        }

　　//从PTE中读取物理内存地址。
        PhysicalAddress.QuadPart = MI_GET_PAGE_FRAME_FROM_PTE (PointerPte);
    }

    PhysicalAddress.QuadPart = PhysicalAddress.QuadPart << PAGE_SHIFT;
    PhysicalAddress.LowPart += BYTE_OFFSET(BaseAddress);

    return PhysicalAddress;
}