ProjectOZ 源码

Copyright (c) Microsoft Corporation Overview -------- ProjectOZ is an experimental environment based on the SPACE abstractions for the CPU, MMU, and trap mechanisms (search: probert bruno SPACE). ProjectOZ implements these abstractions using the native NTAPI of the Windows kernel, including features specific to building user-mode operating system personalities (aka NT subsystems). Because there is a real OS underneath handling the hardware details rather than a simulator, students should find it easier to explore kernels at the algorithm and data structure level rather than worrying about so many low-level details. ProjectOZ is provided in source form to universities worldwide. ProjectOZ is continuing to evolve as contributors join the project. Information on downloading the latest version is available at: http://www.msdnaacr.net/curriculum/pfv.aspx?ID=6547 There is also a community forum for discussions related to ProjectOZ: http://forums.microsoft.com/WindowsAcademic/ShowForum.aspx?ForumID=196&SiteID=8 The Windows Kernel and the Windows Academic Program teams can be contacted at compsci@microsoft.com Architecture ------------ The SPACE abstractions are implemented in a user-mode program (SPACE.exe) which runs as a native subsystem process under Windows. Students run BasicOZ on top of SPACE, using SPACE to provide the basic hardware abstractions. By modifying BasicOZ students implement various projects which improve the rather simple capabilities of BasicOZ. Multiple instances of SPACE.exe can run on a single machine, effectively implementing a multicomputer upon which students can experiment with distributed algorithms. SPACE.exe supports an extensible set of emulated devices. Each device is presented to BasicOZ as a set of registers. The device emulations can cause interrupts and perform DMA operations to memory SPACE Primitives ---------------- SPACE is based on the idea that threads, virtual memory, and IPC are a bad semantic match as the low-level abstractions in a system. What actually exists in the hardware is the CPU, MMU, and trap/interrupt mechanism. Threads, virtual memory, etc, should be higher-level abstractions built on top of fundamental abstractions representing the hardware: CPU - sequences through instructions while referencing memory. MMU - maps CPU virtual addresses into physical addresses, for valid mappings TRAP - an interruption in the normal sequencing of a CPU due to an invalid memory mapping, a trap, exception, or an external interrupt. CONTEXT - a set of MMU mappings is represented by a CONTEXT value (e.g. a hardware contextid, or the root of the page table (CR3 on x86). The permissible operations for each mapping are determined by the CPU MODE. MODE - the current CPU MODE selects how permission bits are applied from each mapping in the current CONTEXT (analogous to Ring0..Ring3 on x86 hardware). PORTAL - for each CONTEXT maps hardware TRAPs to a handler, including specification of a new CONTEXT and MODE as well as the handler itself PCB - when a CPU traverses a PORTAL, the previous execution environment (CONTEXT, MODE, Program Counter, and CPU registers) are recorded in a PCB (Processor Control Block). PCBs are normally chained each time a new TRAP occurs. SPACE Operations ---------------- The basic operations implemented by SPACE.exe manipulate the SPACE primitives. MapMemory(ctx, virtual, phys, modeaccess) MapPortal(ctx, trap, pctx, pmode, ppc, modeaccess) Resume() token = Suspend() Unsuspend(token) MapMemory() and MapPortal() set CONTEXT and PORTAL mappings for a specific CONTEXT. Portal traversal is implicit in response to a TRAP (including deliberately executing an instruction that causes a TRAP). The interrupt execution environment is recorded in a PCB and subsequent portal traversals chain PCBs as a stack. Resume() restores the most recent PCB (analogous to a return-from-interrupt instruction). Suspend() breaks the current chain by assigning a token to it and creating a new chain. Unsuspend() restores a previous chain. NT Facilities used to implement SPACE ------------------------------------- Objects Threads - NT unit of CPU scheduling Processes - NT virtual address space container Sections - NT sharable memory objects Exception port - NT mechanism for subsystem fault handling Functions MapView - Map process addresses to section offsets Wait/Reply port - Receive/Send message to port SPACE Implementation -------------------- CPUs are implemented using NT threads. MMUs are built using NT processes. Because NT threads are bound to processes, each SPACE CONTEXT/MODE is represented as an NT process with an NT thread for each SPACE CPU. SPACE.exe listens on the exception port for the NT processes, which allows it to manipulate the state of the NT threads to chain PCBs, implement portal traversal (including for memory faults) and other SPACE operations. BasicOZ is loaded by SPACE.exe, and then communicates by causing traps which SPACE.exe handles to implement the SPACE 'hardware' emulation. Workloads, Instrumentation, Community ------------------------------------- If ProjectOZ proves to be a useful environment for teaching operating systems, then over time much of the support will come from the academic community itself. ProjectOZ will be extended to improve the accuracy of the instrumentation available to students, and workloads will be developed that allow student projects to be more accurately contrasted & compared. Using WRK, the Windows Kernel itself may be extended to provide some of the facilities that are currently not available to ProjectOZ (such as thread-virtual time, reference & dirty bits for the shared memory section, 64KB pages). PREVIEW INFORMATION ------------------- The ProjectOZ preview makes information about the NTAPI mechanisms used by ProjectOZ available to interested faculty and our collaborators. There is prototype code for SPACE.exe which implements the SPACE primitives. It will boot the skeletal BasicOZ and demonstrate how the trap, MMU, and CPU mechanisms work. There will be a continuous stream of drops of ProjectOZ over the summer with increasing amount of functionality in BasicOZ, as well as development of the first projects. If you want to build and play with the code, you need the July WRK for the tools: set wrk=the WRK directory set projectoz=the ProjectOZ directory path %wrk%\tools\x86;%path% nmake -nologo x86= To get on the list for notification of updates contact me directly, or if you'd rather poll -- just check the curriculum website periodically. http://www.msdnaacr.net/curriculum/pfv.aspx?ID=6547 - DavePr@microsoft.com Updated: 2006/07/14