The Windows Operating System.ppt

The Windows Operating System Goals Hardware-portable Used to support MIPS, PowerPC and Alpha Currently supports x86, ia64, and amd64 Multiple vendors build hardware Software-portable POSIX, OS2, and Win32 subsystems OS2 is dead POSIX is still supported—separate product Lots of Win32 software out there in the world Goals High performance Anticipated PC speeds approaching minicomputers and mainframes Async IO model is standard Support for large physical memories SMP was an early design goal Designed to support multi-threaded processes Kernel has to be reentrant Process Model Threads and processes are distinct Process: Address space Handle table (Handles = file descriptors) Process default security token Thread: Execution Context Optional thread-specific security token Tokens “Who you are”—list of identities Each identity is a SID Also contains Privileges Shutdown, Load drivers, Backup, Debug… Can be passed through LPC ports and named pipe requests Server side can use this to selectively impersonate the client. Object Manager Uniform interface to kernel mode objects. Handles are 32bit opaque integers Per-process handle table maps handles to objects and permissions on the objects Implements refcount GC Pointer count—total number of references Handle count—number of open handles Object Manager Implements an object namespace Win32 objects are under \BaseNamedObjects Devices under \Device This includes filesystems Drive letters are symbolic links \??\C: = the appropriate filesystem device Some things have other names Processes and threads are opened by specifying a CID: (Process.Thread) Standard operations on handles CloseHandle() DuplicateHandle() Takes source and destination process Very useful for servers WaitForSingleObject(), WaitForMultipleObjects() Wait for something to happen Can wait on up to 64 handles at once Security Descriptors Each object has a Security Descriptor Owner—special SID, CREATOR_OWNER Group—special SID, CREATOR_GROUP DACL Discretionary Access Cont