THE KERNEL

• execution levels
• modules

The kernel is a monolithic design. There are some core routines that comprise the majority of the kernel. I suppose if someone were to make this a microkernel, these routines would be what you would put there (along with any necessary support).

• oz_knl_event.c - event flags, a thread can wait for an event flag (or any one of a group of event flags) to be set
• oz_knl_process.c - processes are basically a set of pagetables
• oz_knl_section.c - sections are chunks of virtual memory (a stack, a mapping of a file) that get mapped to processes
• oz_knl_thread.c - threads are "virtual cpu's" that execute instructions

• oz_knl_ast.c - ast objects

  An ast is an 'asynchronous system trap'. VMS programmers know them well. Unix programmers can think of them as sort of like SIGIO's, but they are specifically tied to a particular I/O. Like you start an asynchronous read and you specify an particular ast routine to be called when that particular read completes. They may also be thought of as a user-mode equivalent of an interrupt.

  There are several flavors of ast's:

  • user mode normal - these are what you get when a user-mode initiated I/O completes (they can be masked).
  • user mode express - these are used by the debugger to 'halt' threads in a process (they cannot be masked).
  • kernel mode normal - you would get one of these from a kernel-mode initiated I/O. They are also used to abort threads (they can be masked).
  • kernel mode express - these are used at the end of an I/O operation to complete things like returning the status and lengths back to the proper place (they cannot be masked).

• oz_knl_boot.c - boot startup routine

  This routine initializes the pool areas, creates the system user, job and process, creates the system logical names, starts the other cpu's running and initializes the device drivers

• oz_knl_cache.c - generic caching routines

  These routines use otherwise unused physical memory pages to store data that can be reconstructed, like exact copies of disk blocks, or name to ip address translations

• oz_knl_crtl.c/oz_knl_crtl_486.s - some C runtime library routines linked into the kernel
• oz_knl_dcache.c - disk cache routines
• oz_knl_debug.c - kernel debugger
• oz_knl_devio.c - device objects and I/O utility routines
• oz_knl_diag.c - system diagnostic routines
• oz_knl_event.c - event flag objects

  These are basically the only thing a thread can wait for (except for an available cpu). They normally get set when an I/O operation completes or a thread exits, etc, but they can also be used for things like inter-thread/process communication/synchronization.

• oz_knl_handle.c - handle table manipulation routines
• oz_knl_image.c - image loader routines
• oz_knl_image_oz.c - ozone image loader
• oz_knl_kmalloc.c - kernel memory (nonpaged and paged pool) allocation
• oz_knl_kthread.c - kernel thread objects
• oz_knl_logname.c - logical name objects
• oz_knl_logon.c - logon startup routines

  These routines start the logon process running on a terminal when the terminal driver calls them

• oz_knl_lowipl.c - lowipl objects

  These routines are how a driver operating at interrupt level can call a routine at softint (low ipl) level

• oz_knl_malloc_binned.c - general memory allocator
• oz_knl_phymem.c - physical memory allocator
• oz_knl_printinstr.c - disassembler
• oz_knl_printk.c - kernel mode console print routines
• oz_knl_process.c - process objects
• oz_knl_sdata.c - shared data (kernel global data)
• oz_knl_section.c - memory section objects
• oz_knl_security.c - security objects
• oz_knl_spte.c - system page table entry routines
• oz_knl_startup.c - mount system disk and spawn startup process
• oz_knl_thread.c - thread objects
• oz_knl_userjob.c - user and job objects