56 lines
2.7 KiB
Markdown
56 lines
2.7 KiB
Markdown
# Architecture Outline
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Gila is a microkernel, and almost all functionality of the OS is relegated to
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"server" processes. A server is a process that provides a specific
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functionality, using a kernel-provided interface, and it is given a "seat" by
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the kernel which processes may query to reference it and invoke its functions.
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# Boot Process
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Gila initializes as a bare kernel, with the bootloader providing an init RAM
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filesystem in the form of a .tar.lzma archive. The kernel reads this file, and
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launches an init process (`/system/bin/init`). The init process has its own
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configuration file located at `/system/cfg/init.toml`, which should detail the
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steps needed to bring the system up to a multi-user status.
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If the init system needs to access a filesystem, it must first get the handle
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of the filesystem server. If the filesystem server is not running when this
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handle request is made, the kernel will launch the server before returning its
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handle. From there, the filesystem server will request the handle of the disk
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driver that corresponds to the requested filesystem. The kernel then launches
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the disk driver server, and assigns it a seat based on the device it drives,
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granting it access to the memory region responsible for that device.
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The benefit of this approach is threefold:
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- The system does not need to include a filesystem OR disk driver, if neither
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the disk nor the filesystem are read or written.
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- The driver or filesystem server can crash, and the whole stack can recover.
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- The user or developer can trivially introduce new drivers without a reboot.
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This goes for filesystem drivers AND disk device drivers.
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The system, hence, can be configured in two ways:
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- The drivers can all be included in the initramfs for diskless operation.
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- The bare minimum drivers needed for disk access are included in the
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initramfs, and all other drivers are included in the root filesystem.
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# APIs
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Processes access services similarly to the way the init process accesses
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data from the file system. The process requests the ID of the server that
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performs the function, and then communicates with it via IPC and shared
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memory regions. APIs are to be defined in the standard library.
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# Device Drivers
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Device driver assignment is performed like so:
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- The kernel obtains necessary hardware topology info from ACPI or the DTB.
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- For each device, the kernel spawns a driver process based on a compatibility
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list that details which drivers work for which devices.
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- The driver process, when it initializes, requests information from the
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kernel about the device. The kernel maps relevant regions of physical memory
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into the process's memory space, and returns information on the new mappings
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to the process.
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- The driver then makes its functions available via IPC and shared memory. |