Khalidi, Y. A. and Nelson, M. N. An implementation of UNIX on an objectoriented operating system. In Proceedings of the Winter '93 USENIX Conference, San Diego, California, USENIX, 469-480, 1993.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....them into the frame store. The frame store device for the Desk Area Network [Barham95a] provides these low level window manager primitives in hardware. Finally, a good indicator that most of the functions of the unix kernel can be performed in the application is given by the Spring SunOS emulator [Khalidi92], which is almost entirely implemented as a client library. Nemesis is designed to make use of these techniques. In addition, most of the engineering for creating and linking new domains, and setting up inter domain communication, is performed in the application. 2.5 Summary Resource control in ....

Yousef A. Khalidi and Michael N. Nelson. An Implementation of UNIX on an Object-oriented Operating System. Technical Report 92-3, Sun Microsystems Laboratories, Inc., December 1992. (p 18) 108

....return the aggregate result. The formal type signature for SetCollector is: ff fi) fi fl) ff fl) 2.5 Garbage Collection Some servers would like to be notified when there are no more senders to their respective ports. Many other systems, such as Mach [Accetta et al. 86] and Spring [Khalidi Nelson 93] provide a no more senders notification. Note that in SPIN, the number of domains that the gateway is mapped to indicates the number of potential connections to the service. The linker already keeps track of this number for safety purposes (a domain that is mapped in more than one domain is ....

Khalidi, Y. A. and Nelson, M. N. An Implementation of UNIX on an Object-Oriented Operating System. In Proceed13 ings of the 1993 Winter USENIX Conference, pages 469--480, San Diego, CA, January 1993.

.... under development [Phelan et al. 93, Hildebrand 92, Rozier et al. 92, Zajcew et al. 93] Current practice is to structure a microkernel operating system as one or more server processes that collectively implement the operating system services [Golub et al. 90, Julin et al. 91, Rozier et al. 92, Khalidi Nelson 93, Hildebrand 92] This approach implicitly models the operating system as a distributed system where services reside in remote server processes that happen to be on the same machine. However, the communication overhead incurred when contacting these servers can result in poor performance. In ....

Khalidi, Y. A. and Nelson, M. N. An Implementation of UNIX on an Object-oriented Operating System. In Proceedings of the Winter 1993 USENIX Conference, pages 469--479, 1993.

....support [Nelson 91] and post processing of binary code [Wahbe 93] Each of these approaches has been used to increase modularity and security and to facilitate debugging of large software systems. Protection has also been used to ease modification or replacement of software components [Pu 95] Khalidi Nelson 93] Orr 92] Most work regarding enforcement of protection boundaries in current operating system software, both user level and kernel level, has been focussed on improving the efficiency of cross domain invocations. Invocation times have been significantly reduced by handoff scheduling [Black 89] ....

Khalidi, Y. A., and Nelson, M. N. "An Implementation of Unix on an Object-Oriented Operating System." In Proceedings of the Winter 1993 USENIX Conference. The USENIX Association, Berkeley, CA, 1993, pp. 469-479.

.... et al. 1988] Loepere 1992] and OSF 1) Amoeba [Mullender et al. 1990] Chorus [Rozier et al. 1988] MOS [Barak and Litman 1985] Cronus [Schantz et al. 1986] Sprite [Ousterhout et al. 1988] Locus [Walker et al. 1983] Clouds [Dasgupta et al. 1991] Choices [Campbell et al. 1993] Spring [Khalidi and Nelson 1993] and Nexus [Tripathi 1989] The design goals of some of these systems have been quite varied. The Locus and Sprite designs were primarily guided by the requirement of providing a network transparent UNIX environment in local area networks of computers. Mach, Chorus, and Spring have used the ....

Yousef A. Khalidi and Michael N. Nelson. Implementation of UNIX on an Object-Oriented Operating System. In Proceedings of the 1993 Winter USENIX, pages 469--479, January 1993.

....the server and calls the handler before returning from the original call. This solution is not ideal (a signal handler can t be called until the program makes a Sprite request) but it was adequate for a prototype. In retrospect, the dedicated thread approach, which is how the V [4] and Spring [12] projects handled this problem, might have been the better choice. 4. Status and code measurements Despite the problems mentioned in the previous section, the Sprite server works and is about 75 complete. This section explains the server s current status and presents some code size ....

Yousef A. Khalidi and Michael N. Nelson. "An Implementation of UNIX on an Object-oriented Operating System", Proceedings of the Winter 1993 USENIX Conference, January 1993, 469--480.

....significant performance improvements from specialized or tuned memory management policies that are accessible through interfaces exposed by the memory management system. Some of these interfaces have made it possible to manipulate large objects, for example entire address spaces [YTR 87, KN93] or to direct expensive operations, for example page7 out [HC91, MA90, CFL94] entirely from user level. Others have enabled control over relatively small objects, for example cache pages [RLB94] or TLB entries [BKW94] entirely from the kernel. None have allowed for fast, fine grained control ....

Yousef A. Khalidi and MichaelN. Nelson. An Implementation of UNIX on an Object-Oriented Operating System. In Proceedings of the 1993 Winter USENIX Conference, pages 469--480, January 1993.

....X server CPU usage jointly. During the measurements, the CPU was never idle. Notes: y includes 42.3 of time actually spent in kernel s stalling graphics FIFO full interrupt handler. z likewise includes 84.0 of time spent in FIFO full interrupt handler. libraries extracted from the kernel proper [11, 14]. The advantage of a client server structuring in separate address spaces is modularity and distributability. The advantage of kernel style structuring is less data transfer and lower context switching overhead for potentially better performance in tightly integrated systems (like local window ....

Yousef Khalidi, Michael Nelson, "An Implementation of Unix on an Object-oriented Operating System," Usenix Conference Proceedings, January 1993.

....in recent literature of services being implemented as client libraries instead of within a kernel or server. Efficient user level threads packages have already been mentioned. Other examples of user level libraries include network protocols [12] window system rendering [13] and Unix emulation [14]. Nemesis is designed to use these techniques. In addition, most of the support for creating and linking new domains, setting up inter domain communication, and networking is performed in the context of the application. The result is a vertically integrated operating system architecture, ....

....be either a simple pointer to library code (and local state) or to a surrogate for a remote interface. In the local case an interface reference and invocation reference have the same representation a pointer to a closure binding is an implicit and trivial operation. In Nemesis, as in Spring [14], all interfaces are strongly typed, and these types are defined in an interface definition language (IDL) The IDL used in Nemesis, called Middl, is similar in functionality to the IDLs used in object based RPC systems, with some additional constructs to handle local and low level operating ....

Yousef A. Khalidi and Michael N. Nelson, "An Implementation of UNIX on an Object-oriented Operating System", Tech. Rep. 92-3, Sun Microsystems Laboratories, Inc., December 1992.

....either expressed or implied, of ARPA, OSF, or the U.S. government. Additional client side code may be used to do additional OS computation. Examples of such architectures can be seen in systems such as IBM s Workplace OS [Phelan 93] OSF1 AD [Zajcew 93] FSF GnuHurd , Sun s Spring [Khalidi Nelson93] and Mach US from Carnegie Mellon University [Julin 91] The goal of this separation is to achieve several kinds of flexibility in system configuration and development. These include: simplified development and debugging of individual services, replaceable system services, support for ....

Y.A. Khalidi and M.N. Nelson. An implementation of Unix on an Object-oriented Operating System. USENIX Winter 1993 Conference Proceedings, January 1993.

.... In the active server model of computation, objects are active entities containing threads of execution that service requests to the object [92, 91] An OSOS supporting passive objects offers an object thread model where a single thread of execution traverses all objects within an invocation chain [68, 128]. One use of object orientation in operating systems is to exploit type hierarchies to achieve operating system configuration (e.g. as done in Choices [47] along with stronger notions of structuring than available in current systems. Another use of this technology is to use object based ....

Y. Khalidi and M. Nelson. An implementation of unix on an object oriented operating system. In Proceedings of the 1993 Winter Usenix Conference, San Diego, January 1993.

....Spring The Spring system [44] was developed in Sun Microsystems Laboratories on 32 bit SPARC V8 machines. Spring is built around a microkernel, the Spring nucleus, has an objectoriented design, and supports distributed applications. A Unix server has also been written on top of the Spring nucleus [55]. One of the main objectives of Spring was to develop strong interfaces between operating system components and to treat all components as replaceable parts [72] Spring can run with all services loaded into separate domains. However, under normal operation related services are clustered into the ....

Yousef A. Khalidi and Michael N. Nelson. An Implementation of Unix on an ObjectOriented Operating System. In Proceedings of the Winter USENIX Conference, January 1993.

....derived abstractions (OS items) such as files, ttys, and pipes. Additional client side code may be used to do additional OS computation. Examples of such architectures can be seen in systems such as IBM s Workplace OS [Phelan 93] OSF1 AD [Zajcew 93] FSF GnuHurd , Sun s Spring [Khalidi Nelson93] and Mach US from Carnegie Mellon University [Julin 91] The goal of this separation is to achieve several kinds of flexibility in system configuration and system development. These include: ffl Rapid development of new or modified subsystems without the potential of crashing or corrupting ....

Y.A. Khalidi and M.N. Nelson. An implementation of UNIX on an Object-oriented Operating System. USENIX Winter 1993 Conference Proceedings, January 1993.

....door identifiers to and from an extended network form. 3.4 Status Spring currently exists as a fairly complete prototype. The operating system is based around a minimal kernel, which provides basic object oriented inter process communication [Hamilton Kougiouris 1993] and memory management [Khalidi Nelson 1993A] Functionality such as naming, paging, file systems, etc. are all provided as user mode services outside of the basic kernel. The system also provides enough Unix emulation to support standard utilities such as make, vi, csh, the X window system, etc. Khalidi Nelson 1993B] All system ....

....memory management [Khalidi Nelson 1993A] Functionality such as naming, paging, file systems, etc. are all provided as user mode services outside of the basic kernel. The system also provides enough Unix emulation to support standard utilities such as make, vi, csh, the X window system, etc. [Khalidi Nelson 1993B] All system interfaces are defined in IDL and all inter process communication uses our subcontract machinery. 4 Where subcontract fits in A Spring object is perceived by a client as consisting of three things: 1) a method table, which contains an entry for each operation implied by the ....

Y. A. Khalidi and M. N. Nelson. "An Implementation of UNIX on an Object-oriented Operating System." Proc. of the 1993 Winter Usenix Conference, San Diego, January 1993.

....changes to a file system, external pager, or device driver can be made with small amounts of effort. Some frameworks however can simplify the construction of an incremental interface. Most notably, object based and delegation based interfaces have been shown to facilitate small changes [Andert 94, Khalidi Nelson 93] when extensions are trusted. Their utility with untrusted extensions remains in question, however as they do not provide a complete solution [Steinberg 94] Incrementality is not a natural by product of a system s overall gross structure. Recently, for example, there have been efforts to migrate ....

Khalidi, Y. A. and Nelson, M. N. An Implementation of UNIX on an Object-Oriented Operating System. In Proceedings of the 1993 Winter USENIX Conference, pages 469--480, January 1993.

....and compare our performance with that of related work. 1.1. Short overview of Spring Spring currently exists as a fairly complete prototype. Two components of the OS run in kernel mode. One of these is the virtual memory manager, which provides the core facilities for paged virtual memory [Khalidi Nelson 1993A] The other is the microkernel proper, known as the nucleus, which provides the basic primitives for domains (the Spring analogue of UNIX processes) and threads. 2 Functionality such as file systems, naming, paging, etc. are all provided as user mode services on top of this basic kernel. ....

....type system with multiple inheritance.The system is inherently distributed and a number of caching techniques are used to boost network performance for key functions. The system provides enough UNIX emulation to support standard utilities such as make, vi, csh, the X window system, etc. [Khalidi Nelson 1993B] 1.2. Related work Many operating systems provide some form of message passing interprocess communication. Recent examples include sockets in Berkeley UNIX [Leffler et al. 1989] ports in Mach [Acetta et al. 1986] and ports in Chorus [Rozier et al. 1992] It is possible to provide a procedural ....

[Article contains additional citation context not shown here]

Y. A. Khalidi, M. N. Nelson. "An implementation of UNIX on an object-oriented operating system." Proceedings of the Winter USENIX Conference, San Diego, January 1993.

.... and quality of microkernels [Phelan et al. 93, Hildebrand 92, Rozier et al. 88] Current practice is to structure a microkernelbased operating system as one or more server address spaces that collectively implement operating system services [Golub et al. 90, Julin et al. 91, Rozier et al. 88, Khalidi Nelson 93, Hildebrand 92] However, it is often as difficult to modify a service in another address space as it is to modify one placed in the kernel, diminishing many of the flexibility advantages that favor microkernel architectures. In addition, the communication overhead incurred when contacting ....

....design, the packet filter is able to support protocol processing for a large number of applications [Yuhara et al. 94] SPIN generalizes on the notion of the packet filter, enabling richer, more complex services to be safely installed into the kernel. Dynamic linking In systems such as Spring [Khalidi Nelson 93] Chorus [Rozier et al. 88] and OSF 1 the kernel can be modified at run time with a new set of interface implementations for heavyweight services like device drivers or the Unix file system. Pure object code is downloaded on the fly from user level into the kernel, exposing the kernel to ....

Khalidi, Y. A. and Nelson, M. N. An Implementation of UNIX on an Object-Oriented Operating System. In Proceedings of the 1993 Winter USENIX Conference, pages 469--480, January 1993.

....any other context allowing arbitrary naming graphs to be created. The naming services are also used to support persistence as described below. Finally, in line with the goal of supporting existing applications, Spring provides a Unix emulation service implemented by a library and associated server [43]. Although binary compatibility with Unix was not a goal of Spring, and is not supported, the Spring Unix emulation supports a large subset of the system calls provided by SunOS 4.1 and runs dynamically linked SunOS 4.1 executables without modification. The goal of the Unix subsystem design was to ....

Yousef A. Khalidi and Michael N. Nelson. An implementation of UNIX on an objectoriented operating system. In Proceedings of the 1993Winter Usenix Conference, pages 469--479. Usenix Association, January 1993.

....of a traditional monolithic system, but sacrifice flexibility. As extensibility has evolved into an important trend in operating system design, Unix functionality has been separated from the kernel and spread among libraries, server applications, and kernel extensions. Library emulations [Khalidi Nelson 92] generally have excellent performance (provided calls to native system services can be minimized) since system calls can be reduced to local procedure calls. However, libraries are inherently unsafe from applications. Errant or malicious applications can corrupt library data, causing ....

....The emulation library is loaded directly into an application s address space, which means that an errant application can corrupt emulation data and cause unpredictable behavior. Also, Mach 3.0 offers no mechanism for applications to define a shortcircuit for calls to the server. The Spring [Khalidi Nelson 92] Unix emulation increases the functionality of the dynamically linked library. The Spring Unix emulation library replaces the dynamically linked libc. Besides providing the traditional services of libc, it contains specialized system call stubs. Rather than generate a system call trap, these ....

Khalidi, Y. A. and Nelson, M. N. An Implementation of Unix on an Object-oriented Operating System. USENIX 1992. Reprinted with permission.

....functions of Mach, Mach itself will be less and less important to us; we expect the embedded operating system we are planning to design to be substantially more modular than Mach, for example. One operating system project that has really focused on modularity is the Spring operating system project [62, 63, 99] underway at Sun. Unlike Spring, we propose to use SML instead of C , and we plan to focus on modularity more than on having an object oriented operating system (see above) Our focus is an operating system which can be assembled out of different modules at compile time with assurance that ....

Yousef A. Khalidi and Michael N. Nelson. An implementation of UNIX on an object-oriented operating system. In Proceedings of Winter '93 USENIX Conference, January 1993.

.... that manages and caches dynamically linked libraries [12] a network proxy that handles remote invocations; a tty server that provides basic terminal handling as well as frame buffer and mouse support; and a UNIX server that provides support for running UNIX binaries on the Spring operating system [13]. FIGURE 1. Spring object The client domain has an object that is implemented by a server domain. The client has a representation for the object that allows the invocations on the object to get to the server domain. The server keeps some state for the object. Server Domain Client Domain Object ....

Khalidi, Y. A. and M. N. Nelson."An Implementation of UNIX on an Object-Oriented Operating System." Proceedings of the 1993 Winter USENIX Conference (January 1993): 469-480.

....and services are requested by invoking objects. Spring is a distributed multi threaded system that is constructed to exploit a range of systems from tightly coupled multiprocessors to more loosely coupled networks. Spring supports traditional UNIX programs through compatibility mechanisms [1], but it is aimed toward new computing requirements, such as transparent distribution, high reliability, and stronger security. The architecture and implementation of the virtual memory system of Spring is presented in this document. The design follows the basic Spring object model and strives to ....

....server; a linker domain that is responsible for managing and caching dynamically linked libraries; a network proxy that handles remote invocations; and a tty server that provides basic terminal handling as well as frame buffer and mouse support. Support for running UNIX binaries is also provided [1] . The Spring file system supports cache coherent files [2] The file object interface inherits from the memory object interface and therefore can be memory mapped. The file system uses the virtual memory system to provide data caching and uses the operators provided by virtual memory caches to ....

Yousef A. Khalidi and Michael N. Nelson, "An Implementation of UNIX on an Object-oriented Operating System," Proceedings of Winter `93 USENIX Conference, January 1993.

....Major system components of a Spring node Kernel storage fs UNIX application process server authentication server type server High Performance Dynamic Linking Through Caching 3 of 14 Related Work 2.1. UNIX Subsystem Spring can run most dynamically linked SunOS binaries using a UNIX subsystem [5]. This includes basic UNIX programs such as cat and csh and more sophisticated programs such as openwindows and most X applications. The UNIX subsystem consists of two parts: a UNIX process server that is responsible for managing process ids, ptys, sockets, and signals between processes, and a ....

Khalidi, Y. A. and Nelson, M. N., "An Implementation of UNIX on an Object-oriented Operating System," USENIX Winter Conference, January 1993.

....inheritance. From the operating system point of view, what matters are the interfaces of the different servers and programs. Specific implementations are free to use implementation inheritance and to reuse code. Spring 4 Extensible File Systems in Spring UNIX binaries is also provided [11]. All services are exported via objects defined using the interface definition language. In general, any collection of servers may reside in the same or in different domains. The decision on where to run a particular server is made for administrative, security, and performance reasons, and is ....

Khalidi, Yousef A. and Michael N. Nelson. "An Implementation of UNIX on an Object-oriented Operating System." Proceedings of the 1993 Winter USENIX Conference (January 1993): 469--480.

....memory management. A typical Spring node runs several servers in addition to the kernel. These include domain, file, tty, network, and VM managers, as well as a linker domain that is responsible for managing and caching shared libraries. Spring can run most dynamically linked SunOS binaries [5]. The SunOS binaries runnable on Spring include everything from cat to openwindows. 3.1.1 Spring Security If the implementor and the client are in different domains, the representation of an object includes an unforgeable nucleus handle that identifies the server domain. These unforgeable ....

Khalidi, Y. A. and Nelson, M. N., "An Implementation of UNIX on an Object-oriented Operating System," Proceedings of Winter `93 USENIX Conference, Jan. 1993, pp. 469-479.

No context found.

Yousef A. Khalidi and Michael N. Nelson, "An Implementation of UNIX on an Object-oriented Operating System," Proceedings of Winter `93 USENIX Conference, January 1993.

....is in daily use for its own development and further experimentation. The name service provides acceptable performance in its various uses, although optimization work is ongoing. The system also supports UNIX compatibility mode binaries (the emulation package is a thin veneer on Spring services[16]) The distinguishing features of the Spring name service are as follows: 25 . Uniform and extensible name service. Name services and name spaces do not need to be segregated by the type of the object in principle, any object could be bound to any name.The name service provides critical ....

Khalidi, Y. A. and Nelson, M. N., "An Implementation of UNIX on an Object--oriented Operating System", USENIX Winter Conference, January 1993.

....and contrast our approach with that of Plan 9; although there are similarities, there are many subtle and important differences. The naming system described in this paper was developed as part of the Spring operating system project. This naming system works together with the Spring UNIX subsystem [3] to provide users and normal UNIX programs uniform naming access to most types of UNIX objects. 2. Spring Operating System Spring is a distributed, multi threaded, extensible operating system that is structured around the notion of objects. A Spring object is an abstraction that contains state ....

.... a linker domain that manages and caches dynamically linked libraries, a network proxy that handles remote invocations, a device server that provides basic terminal handling as well as frame buffer and mouse support, and a UNIX server that provides support for running UNIX binaries on Spring [3]. 3. Spring Naming The Spring name service [6 ] allows any object to be associated with any name. A name to object association is called a name binding. Each name binding is stored in a context. A context is an object that contains a set of name bindings in which each name is unique [7, 8] An ....

Khalidi, Y. A. and Nelson, M. N., "An Implementation of UNIX on an Object-oriented Operating System", Proceedings of the 1993 Winter USENIX Conference, January 1993, pp. 469-479.

.... linker domain that manages and caches dynamically linked libraries [7] a network proxy that handles remote invocations, a device server that provides basic terminal handling as well as frame buffer and mouse support, and a UNIX server that provides support for running UNIX binaries on Spring [8]. 2.1 Spring Security If the server and the client of an object are in different domains, the representation of the object includes an unforgeable handle managed by the kernel that identifies the server domain. These FIGURE 1. Spring Object The client domain has an object that is implemented ....

Khalidi, Y. A. and Nelson, M. N., "An Implementation of UNIX on an Object-oriented Operating System," Proceedings of the 1993 Winter USENIX Conference, Jan. 1993, pp. 469480.

....By default, at start up each domain is passed from its parent a private domain name space, which incorporates the user and system name spaces. A domain can acquire other name spaces and contexts if it desires. 11 UNIX Emulation Spring can run Solaris binaries using the UNIX emulation subsystem [6]. It is implemented entirely by user level code, employs no actual UNIX code, and provides binary compatibility for a large set of Solaris programs. The subsystem uses services already provided by the underlying Spring system and only implements UNIX specific features that have no counterpart in ....

Yousef A. Khalidi and Michael N. Nelson, "An Implementation of UNIX on an Object-oriented Operating System," Proc. Winter 1993 USENIX Conference, pp. 469-479, January 1993.

No context found.

Khalidi, Y. A. and Nelson, M. N. An implementation of UNIX on an objectoriented operating system. In Proceedings of the Winter '93 USENIX Conference, San Diego, California, USENIX, 469-480, 1993.

No context found.

Yousef A. Khalidi andMichael N. Nelson. "An implementation of Unix on an object-oriented operating system". Usenix Conference Proceedings, San Diego, January 1993.

No context found.

Yousef A. Khalidi, Michael N. Nelson. "An implementation of Unix on an object-oriented operating system". Usenix Conference Proceedings, San Diego, January 1993.

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