1.2.3 Component Libraries

Finally, the OSKit's component libraries provide generally higher-level functionality in a more standard, coarse-grained, object-oriented ``black box'' design philosophy. Although the OSKit's ``components'' are also packaged into ordinary link libraries by default, their structure represents more of a component-oriented design than a traditional C function-oriented design. In contrast with the OSKit's function libraries, the component libraries typically export relatively few public entrypoints in comparison to the amount of functionality provided. For example, in the Linux and BSD device driver component libraries (see Chapters 29 and  30), each entire device driver is represented by a single function entrypoint which is used to initialize and register the driver as a whole. The client OS generally interacts with these components through the OSKit's object-oriented COM interfaces, allowing many components and instances of components to coexist and interact as defined by the OS developer. This design strategy has proven to be most appropriate when incorporating large chunks of existing code from existing systems such as BSD and Linux, where it is more important to hide the details of the original environment than to provide the most flexibility.

Following is a summary of the component libraries currently provided by the OSKit along with the chapter numbers in which each is described:

• POSIX emulation and libraries

  13

  liboskit_freebsd_c: Complete POSIX-like C library derived from FreeBSD, providing both single- and multithreaded configurations. This library is an alternative to the minimal C library liboskit_c (above), intended for programs that use substantial POSIX-like functionality or need thread-safety. The FreeBSD ``system call'' layer is replaced with glue code that uses the OSKit COM interfaces, while the higher-level code is mostly unchanged from that found in FreeBSD.

  14

  liboskit_freebsd_m: Complete standard math library (taken from FreeBSD's libm). The functions in this library will commonly be needed by programs that use floating point.

• Memory management

  15

  liboskit_lmm: A flexible memory management library that can be used to manage either physical or virtual memory. This library supports many special features needed by OS-level code, such as multiple memory types, allocation priorities, and arbitrary alignment and placement constraints for allocated blocks.

  16

  liboskit_amm: The Address Map Manager library manages collections of resources where each element of a collection has a name (address) and some set of attributes. Examples of resources that might be managed by address maps include swap space and process virtual address space.

  17

  liboskit_svm: The Simple Virtual Memory library uses the AMM library to define a simple virtual-memory interface for a single address space that can provide memory protection and paging to a block device such as a disk partition. (unsupported/redzone.c provides a stack redzone for single-threaded kernels, without all of SVM.)

• Threads, synchronization, and scheduling

  18

  liboskit_threads: This library provides support for multithreaded kernels, including POSIX threads, synchronization, scheduling, and stack guards. Scheduling policies are the standard POSIX Round-Robin and FIFO. Experimental support for CPU inheritance scheduling, a hierarchical framework for arbitrary scheduling policies, is also provided, although not integrated or robust. Provided policies include rate-monotonic, stride (WFQ), and lottery scheduling.

• Development aids

  19

  liboskit_memdebug: This library provides debugging versions of malloc et al that check for a variety of bugs related to memory-allocation (overruns, use of freed blocks, etc).

  20

  liboskit_gprof: Run-time support code for an OSKit kernel to collect profiling data about itself and report it at the end of a run. Profiling data can be collected for kernel code compiled with the ``-pg'' option (as for use with Unix gprof), and profiled ``_p'' versions of all OSKit libraries are provided to profile OSKit code used by the application kernel.

• Simple disk/file reading and loading

  21

  liboskit_diskpart: A generic library that recognizes various common disk partitioning schemes and produces a complete ``map'' of the organization of any disk. This library provides a simple way for the OS to find relevant or ``interesting'' disk partitions, as well as to easily provide high-level access to arbitrary disk partitions through various naming schemes; BSD- and Linux-compatible naming mechanisms are provided as defaults.

  22

  liboskit_fsread: A simple read-only file system interpretation library supporting various common types of file systems including BSD FFS, Linux ext2fs, and MINIX file systems. This library is typically used in conjunction with the partition library to provide a convenient way for the OS to read programs and data off of hard disks or floppies. Again, this functionality is often needed at boot time even in operating systems that otherwise would not require it. This code is also extremely useful in constructing boot loaders.

  23

  liboskit_exec: A generic executable interpreter and loader that supports popular executable formats such as a.out and ELF, either during bootstrap or during general operation. (Even microkernel systems, which normally don't load executables, generally must have a way to load the first user-level program; the OSKit's small, simple executable interpreter is ideally suited to this purpose.)

• Filesystem implementations

  24

  liboskit_linux_fs: Encapsulated Linux 2.0.29 filesystem code. Includes the Linux VFS layer supporting ext2fs, the primary Linux filesystem, as well as numerous other PC filesystems supported under Linux.

  25

  liboskit_netbsd_fs: Encapsulated NetBSD 1.2 filesystem code. Includes the BSD VFS layer supporting the local FFS filesystem.

• Networking implementations

  26

  liboskit_freebsd_net: Encapsulated FreeBSD 2.1.7.1 networking code. Includes socket layer and protocol support wrapped to use the OSKit's framework.

  27

  liboskit_bootp: This library provides a simple interface for performing the BOOTP protocol (RFC 1048/1533) on Ethernet devices to retrieve a canonical set of parameters from a server, based on the client's Ethernet hardware address.

  28

  liboskit_hpfq: This library provides hierarchical proportional-share control of outgoing network link bandwidth, described in the Bennet/Zhang SIGCOMM'96 paper.

• Device driver implementations

  29

  liboskit_linux_dev: Encapsulated Linux 2.0.29 device driver set. Currently includes over 50 block (SCSI, IDE) and network drivers wrapped to use the OSKit's device driver framework. See the source file linux/dev/README for a list of devices and their status.

  30

  liboskit_freebsd_dev: Encapsulated FreeBSD 2.1.7.1 device driver set. Currently includes eight TTY (virtual console and serial line, including mouse) drivers wrapped to use the OSKit's device driver framework.

• Video and window manager implementations

  31

  liboskit_wimpi: Simple hierarchical windowing system based on MGR, with only simple drawing and window management operations.

  32

  liboskit_*video*: Basic video support, with two implementations: one encapsulating all of SVGALIB 1.3.0, and one based on XFree86 3.3.1, but with only the S3 driver currently supported. We also provide support for X11 clients.