白话 StackCount StackSize CurrentLocation

先说结论 细节再补充

        StackCount = StackSize

        StackCount 是 StackLocation的数目

        StackSize 是 DeviceObjectStack的数目

CurrentLocation 指的是 现在所处的StackLocation的位置

由于申请IRP者本身不具有irp空间，所以初始化时CurrentLocation = StackCount+1;

IoCallDriver 中

    Irp->CurrentLocation--;  
  
    if (Irp->CurrentLocation <= 0) {  
        KiBugCheck3( NO_MORE_IRP_STACK_LOCATIONS, (ULONG_PTR) Irp, 0, 0 );  
    }  
  

CurrentLocation会减1，然后使用IRP的空间

CurrentLocation至少为1；

在WRK源码中找到了充足的证据

#define IopInitializeIrp( Irp, PacketSize, StackSize ) {          \
    RtlZeroMemory( (Irp), (PacketSize) );                         \
    (Irp)->Type = (CSHORT) IO_TYPE_IRP;                           \
    (Irp)->Size = (USHORT) ((PacketSize));                        \
    (Irp)->StackCount = (CCHAR) ((StackSize));                    \
    (Irp)->CurrentLocation = (CCHAR) ((StackSize) + 1);           \
    (Irp)->ApcEnvironment = KeGetCurrentApcEnvironment();         \
    InitializeListHead (&(Irp)->ThreadListEntry);                 \
    (Irp)->Tail.Overlay.CurrentStackLocation =                    \
        ((PIO_STACK_LOCATION) ((UCHAR *) (Irp) +                  \
            sizeof( IRP ) +                                       \
            ( (StackSize) * sizeof( IO_STACK_LOCATION )))); }