Differences among mdladdress, userbuffer and systembuffer of IRP structure

MdlAddress (Memory Descriptor Link). take Ring3 Address to Ring0 In virtual memory . Use Direct I/O The driver , Supported operations ：IRP_MJ_READ,IRP_MJ_WRITE,IRP_MJ_DEVICE_CONTROL,IRP_MJ_INTERNAL_DEVICE_CONTROL.

UserBuffer. User space address , After process switching , invalid . Used only for IRP_MJ_DEVICE_CONTROL,IRP_MJ_INTERNAL_DEVICE_CONTROL, And the function code uses METHOD_NEITHER or METHOD_BUFFERED. And this memory is read-only for the driver , That is, the user I/O Control the contents of the output buffer specified in .

SystemBuffer. Use buffered I/O The driver . stay Ring3 and Ring0 Copy between . Supported operations ：IRP_MJ_READ,IRP_MJ_WRITE,IRP_MJ_DEVICE_CONTROL,IRP_MJ_INTERNAL_DEVICE_CONTROL. about IO control , It refers to the cache specified by the access permission （READ Then point to the input cache ,WRITE Cache for output ）.