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250 lines
6.1 KiB
Plaintext
250 lines
6.1 KiB
Plaintext
Welcome to the documentation for your
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KittenOS NEO system.
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These documents are written to a 37-
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column standard, in order to match
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the Neolithic text editor.
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If editing them, please set a right
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margin of 37, or an equivalent,
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in order to ensure that the
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documents do not require horizontal
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scroll in order to read.
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This documentation is aimed at those
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who wish to develop things for the
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KittenOS NEO system.
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Due to the size of the system, it is
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divided into several sections,
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each section being a file.
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This section will cover an overview
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of the KittenOS NEO system.
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It is an abstract overview, but one
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that will give you a framework in
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which the components make sense,
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should you simply skip to them.
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The KittenOS NEO system is divided
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into three things - the kernel,
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libraries, and the processes.
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The kernel is always loaded at all
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times, and is the root of all system
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activity.
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The libraries are essentially Lua
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values that are kept in memory by a
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weak-valued table.
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This allows them to be reused,
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and memory saved, if possible,
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while also allowing unloading.
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This is a critical memory management
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technique in KittenOS NEO, as it
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allows certain libraries to be
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loaded only when in active use.
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(This also means libraries can have
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security side-effects, but they
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always can in any system, arguably,
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and it's worth it for the memory.
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Notably, library values get
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wrapMeta'd automatically since R2,
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in order to reduce NEO-specific
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code.)
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The processes are applications and
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services, that communicate with the
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kernel via the NEO Kernel API, and
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that communicate with others via
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Lua values and tables shared between
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the processes, that also constitute
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a form of API.
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These APIs are shared and retrieved
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via Accesses - anything that causes
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a permissions check is an Access.
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Accesses are easy to replace in the
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system, should you wish to heavily
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customize the system in some way.
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The ability to receive given events,
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is also an Access, though all "k."
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events are always accessible for
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simplicity reasons.
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"All components are replacable, as
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long as you implement it correctly."
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Regarding the KittenOS NEO system
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that you are now possibly running,
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it likely has 3 critical services.
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I refer to these as the Trinity, just
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because it seemed to fit.
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The following list notes which APIs
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they provide and require, but only
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from those in the "x." space.
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Anything else is an implementation
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detail, subject to change - indeed,
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these are only listed for the sake
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of those who need to find code for
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a given API.
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-------------------------------------
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Glacier: sys-glacier
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* formerly sys-donkonit
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Shell-independent parts of NEO, such
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as screen management and settings,
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and the "saving throw" recovery
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mechanism.
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Provides x.neo.sys.manage
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x.neo.sys.screens
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x.neo.pub.globals
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Everest: sys-everest
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This is the default shell.
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Provides x.neo.sys.session
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x.neo.pub.window
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Requires x.neo.sys.screens
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Prefers x.neo.sys.manage
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Icecap: sys-icecap
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Shell-dependent component that
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gains k.root and uses Everest
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to implement the security policy.
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Provides x.neo.pub.base
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Requires x.neo.sys.manage
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Prefers x.neo.pub.window
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-------------------------------------
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The bootup process, meanwhile, is
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rather simple.
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The kernel first designates the
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primaryDisk based on the boot disk,
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via the "deprecated" computer API
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that has no replacement and is thus
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nowhere near safe to remove.
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The primaryDisk is *the*
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KittenOS NEO system disk - it holds
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the system, in full.
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Inelegance here falls to the greater
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power of practicality, as a VFS is
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an unnecessary component here.
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After moving its many globals into
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place, it then immediately loads and
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runs sys-init.
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sys-init's job is to firstly display
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the KittenOS NEO boot screen -
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this is where it got its original
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name from, s-bristol (see: Plymouth)
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It chooses the screen / GPU based on
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the best combination it can find.
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The screen that it displays on is
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then noted as the primary screen.
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During this boot screen, it firstly
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starts Glacier, which is always a
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necessary component for sys-init to
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operate correctly.
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It then starts all services that have
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"run." entries set to "yes".
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By default this means sys-icecap.
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Note that sys- entries occur first.
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This allows a security policy to be
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installed, typically by sys-icecap,
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that allows non-sys- parts to
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perform useful operations.
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Finally, screen control is passed to
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Glacier, and sys-init resets the
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screens to their login-screen-state.
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If the settings daemon is not around
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by this point, sys-init fails-safe
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and allows login & safe-mode.
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(If you happen to be able to cause a
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sys-glacier error, during early boot
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in a way that does not require any
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permissions with other ways of
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creating havoc, then, this may be a
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flaw in the system security model.
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The risk is considered worth the
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ability to theoretically use the
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system.)
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If the setting "sys-init.nologin" is
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set to "yes", then the login screen
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is skipped.
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If the password is not empty, then
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a password prompt is used.
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If Lua 5.2 is in use, the usual set
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of instructions are replaced with a
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warning to use Lua 5.3.
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After the login screen finishes,
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sys-init disclaims the primary
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screen, and runs the shell, dictated
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by the setting "sys-init.shell" -
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if settings are not available, then
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sys-everest is used as a guess.
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Up to 5 seconds later, sys-init
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confirms that "x.neo.sys.session" is
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an existing API, and thus a shell is
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currently running.
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If this does not occur in time,
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then sys-init provides the:
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"That wasn't a shell. Try Safe Mode."
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message, and causes a reboot.
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If it does, then sys-init finally
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exits, with the "Trinity" in place,
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and all screens automatically
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disclaimed by sys-init's quit.
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(NOTE: If your particularly beady
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service happens to get ahold of a
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screen during startup, then that
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screen is of course unaffected,
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unless your service dies. This is of
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course intentional in case you want
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a service to control a screen.)
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This should summarize the system.
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Good luck. - 20kdc
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-- This is released into
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the public domain.
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-- No warranty is provided,
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implied or otherwise.
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