Aether
LICENSE: AETHER OPERATING SYSTEM
The Aether project currently uses a singular license GPLv2.0.
The project maintainer(s) reserves the right to change the license in the future without prior notice.
Note that all licenses used by this project are available in the LICENSES/ directory in the source code.
Copyright (c) 2026 Richard Tichý
Used licenses
These are the licenses used by this project.
GPLv2.0
Valid-License-Identifier: GPL-2.0
Valid-License-Identifier: GPL-2.0-only
Valid-License-Identifier: GPL-2.0+
Valid-License-Identifier: GPL-2.0-or-later
SPDX-URL: https://spdx.org/licenses/GPL-2.0.html
Usage-Guide:
To use this license in source code, put one of the following SPDX
tag/value pairs into a comment according to the placement
guidelines in the licensing rules documentation.
For 'GNU General Public License (GPL) version 2 only' use:
SPDX-License-Identifier: GPL-2.0
or
SPDX-License-Identifier: GPL-2.0-only
For 'GNU General Public License (GPL) version 2 or any later version' use:
SPDX-License-Identifier: GPL-2.0+
or
SPDX-License-Identifier: GPL-2.0-or-later
License-Text:
GNU GENERAL PUBLIC LICENSE
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
<https://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
Preamble
The licenses for most software are designed to take away your
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We protect your rights with two steps: (1) copyright the software, and
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The precise terms and conditions for copying, distribution and
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GNU GENERAL PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
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NO WARRANTY
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END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, see <https://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) year name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, the commands you use may
be called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items--whatever suits your program.
You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program
`Gnomovision' (which makes passes at compilers) written by James Hacker.
<signature of Ty Coon>, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your program into
proprietary programs. If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library. If this is what you want to do, use the GNU Library General
Public License instead of this License.
Aether docs
Note that due to the ongoing kernel rewrite, the docs are not up to date right now.
- architecture.md
- building.md
- development.md
- hardware-interrupts.md
- kernel/init_contract.md
- syscalls.md
Aether Architecture
Overview
Aether is a microkernel-inspired operating system kernel targeting x86_64 and aarch64. The kernel itself is small: it manages physical and virtual memory, provides a preemptive scheduler, routes hardware interrupts to userspace tasks, and exposes a minimal syscall interface. Everything else — device drivers, program loading, IPC — lives in userspace.
Boot Flow
- The Limine bootloader loads the kernel ELF image and an
initrd(tar archive) as a module. It also provides a framebuffer, memory map, RSDP, and command-line string to the kernel via the Limine protocol. kernel/entry— the Rust entry point (start.rs) is called by Limine. It sets up a two-phase allocator (early bump allocator → paged allocator) and callskernel_core::main(...).kernel/coremain()initializes subsystems in order:- Virtual address allocator
- Physical memory manager
- Virtual memory manager (HHDM-aware)
- Early serial console
- Platform-specific initialization (ACPI parsing, APIC/GIC setup)
- Framebuffer terminal
- Interrupt controller (APIC on x86_64, GIC on aarch64)
- Paged memory allocator (replaces the early bump allocator)
- Task registry and scheduler
- Syscall dispatcher
- Timer (preemption tick at 100 Hz)
- The kernel loads the
initELF binary from the initrd using its own ELF loader, creates a new address space, mapsboot_infoand the initrd into it, and spawns theinittask. - The kernel disables its early console and switches to the scheduler. From this point on the kernel runs only in response to interrupts and syscalls.
Component Map
┌────────────────────────────────────────────────────────────────────┐
│ Workspace │
│ │
│ kernel/entry ──► kernel/core ──► kernel/hal ──► kernel/platform │
│ │ │
│ └──► kernel/api (syscall ABI + boot_info) │
│ │
│ init ──► libs/libsyscall (C stubs) │
│ ──► kernel/api/init/boot_info.h │
│ │
│ hello_world ──► libs/aether_rt (Rust runtime) │
│ ──► libs/aether_sys (Rust syscall wrappers) │
│ │
│ image/ ──► initrd (tar) + ISO/raw disk image │
└────────────────────────────────────────────────────────────────────┘
kernel/entry
The bootloader-facing crate (#![no_std], #![no_main]). Registers Limine
requests (framebuffer, memory map, HHDM offset, modules, RSDP, command line)
and implements the two-phase allocator hand-off:
- Early allocator — a simple bump allocator backed by a static buffer, used before page-frame allocation is available.
- Proxy allocator — a
#[global_allocator]wrapper that delegates to whichever allocator is currently active and supports an atomic hand-off.
kernel/core
The heart of the kernel. Key modules:
| Module | Responsibility |
|---|---|
scheduler | Round-robin preemptive scheduler; supports null/idle task, IRQ wake-up, task exit |
syscall_handler | Dispatches syscalls to per-syscall handlers |
task_registry | Stores and manages all tasks (kernel threads and userspace processes) |
allocator | Paged kernel heap (allocation only; deallocation not yet implemented) |
elf | Loads ELF64 binaries into a new address space |
init_process | Reads the initrd, finds the init binary, and spawns the init process |
tarball_parsing | Minimal ustar tarball parser used to locate files in the initrd |
ticker | Configures the hardware timer to fire at a fixed Hz and drive the scheduler |
platform/* | Trait-based abstraction layer consumed by kernel_core |
The platform/ sub-module contains Rust traits (e.g. EarlyConsole,
PhysicalMemoryManager, Interrupts, Syscalls, VirtualMemoryManager)
whose implementations live in kernel/hal.
kernel/hal
The Hardware Abstraction Layer. Contains two sub-modules — arch/x86_64 and
arch/aarch64 — selected at compile time via cfg(target_arch = …).
Each implementation covers:
- CPU — core initialization, per-CPU data structures, halting
- Early console — UART-based serial output used before the terminal is up
- Emergency console — fallback output used during kernel panics
- Interrupts — IDT/GDT (x86_64), exception vectors (aarch64), IRQ masking
- MMU — page table management, address space switching
- Syscalls —
syscall/sysret(x86_64),svc(aarch64) entry/exit - Tasks — task frame layout, context switching
- Timer — LAPIC timer (x86_64), ARM Generic Timer (aarch64)
kernel/platform
Low-level C and assembly code that kernel_hal calls into. Includes:
- ACPI table parsing and APIC/IOAPIC/GIC discovery
- Page table structures for both architectures
- Physical memory map processing
- String and memory utilities
kernel/api
Shared ABI between the kernel and userspace.
init/boot_info.h— theboot_infostruct passed by the kernel to theinitprocess at startup (initrd pointer and size).syscalls/syscalls.toml— machine-readable syscall definitions (number, return type, argument names and types).syscalls/errors.toml— error codes returned by syscalls.syscalls/syscall_parser.py— shared Python library that parses the TOML definitions and drives code generators.syscalls/syscall_kernel_gen.py(inkernel/syscalls/) — generates the kernel-side dispatch glue.libs/libsyscall/syscall_c_stubs.py— generatessyscalls.hfor C userspace.libs/aether_sys/syscall_aether_sys_gen.py— generates the Rustaether_syscrate.
init
The first userspace process (written in C). Its responsibilities are:
- Initialize the serial port and use it as stdout.
- Parse the initrd tarball and locate the
bin/hello_worldELF binary. - Load the ELF binary into a new address space via
proc_create/proc_mmap/proc_mprotsyscalls. - Spawn the loaded process using
proc_spawn. - Optionally handle keyboard input (driver in
src/drivers/keyboard/).
hello_world
A minimal Rust binary that prints a message via the write syscall and loops.
It exercises the aether_rt runtime and aether_sys syscall library.
libs/aether_rt
The Rust userspace runtime crate. Provides:
_startentry point — sets up the heap and callsmain- A heap allocator (linked-list allocator over a static buffer)
- Panic handler
libc-style shims (memcpy,memmove,memset,memcmp,__errno_location)__rust_probestack/_Unwind_Resumestubs required by the Rust compiler
libs/aether_sys
Auto-generated Rust bindings for every syscall and constant defined in
syscalls.toml / errors.toml. Regenerated by cargo build—see build.rs.
libs/libsyscall
Auto-generated C header (syscalls.h) and stubs for every syscall. Used by the
init program.
Memory Layout
Kernel
The kernel is loaded by Limine into the higher half of the virtual address space. Limine provides a Higher-Half Direct Map (HHDM) offset so the kernel can access all physical memory through a fixed virtual offset.
Userspace
The lower half of the virtual address space is available to userspace processes.
Kernel-provided data (boot info, initrd, bootstrap stack) is mapped at the high
end of the lower half, growing downward. See
kernel/init_contract.md for the exact layout
convention used for the init process.
Syscall ABI
All syscalls follow a consistent convention:
- Each syscall has a unique number (0–255).
- The kernel returns an error code in one register and an optional return value in another.
- Using the return value when the error code is non-zero is undefined behavior.
- Up to 5 arguments are supported.
See syscalls.md for the full reference.
Building Aether
Host Prerequisites
- GNU Make — Used for orchestrating builds. Doesn’t have to be in
PATH. - QEMU — Required for running:
qemu-system-x86_64(x86_64) and/orqemu-system-aarch64(aarch64). - Python 3 — Required by code-generation scripts.
- Clang / LLVM — Used for compiling C/ASM code, for linking, and binutils.
- Rust — Used for compiling Rust code.
Architecture Configuration
All build and run commands accept an ARCH variable that selects the target
architecture:
ARCH=x86_64— 64-bit x86ARCH=aarch64— 64-bit ARM
Building
Build everything for x86_64:
make all ARCH=x86_64
Build everything for aarch64:
make all ARCH=aarch64
You can also build individual targets, for example:
# Build only the kernel ELF
make pkg/kernel/install ARCH=x86_64
# Build the init binary
make pkg/init/install ARCH=x86_64
# Build the hello_world binary
make pkg/hello_world/install ARCH=x86_64
# Build the bootable ISO image
make dist/aether-x86_64.iso ARCH=x86_64
# or
make dist/aether-aarch64.img ARCH=aarch64
Development Guide
IDE Support
Aether supports two language servers:
- Rust — Two Cargo workspaces (
/and/kernel/) consumed byrust-analyzer. - C/C++ —
compile_commands.jsonconsumed byclangd.
VS Code
The repository includes .vscode/ configuration:
- Recommended extensions — see
.vscode/extensions.json. Install them via Extensions → … → Show Recommended Extensions. The key extensions arerust-lang.rust-analyzer(Rust) andllvm-vs-code-extensions.vscode-clangd(C/C++). - Settings (
.vscode/settings.json) — pre-configuresrust-analyzerto load Cargo workspaces, andclangdwith the correct compile-commands directory. - Tasks — the default build task (Terminal → Run Build Task,
Ctrl+Shift+B) runs theSync Project (C + Rust)command and prompts you to pick an architecture.
Zed
The repository includes .zed/ configuration:
- Tasks (
.zed/tasks.json) — preconfigured tasks:- Sync Project for x86_64 (C + Rust) — regenerates project files
- Qemu run x86_64 / Qemu run aarch64 — run in QEMU
- Qemu debug aarch64 — start QEMU with debugger stub
- Debug (
.zed/debug.json) — a Qemu debug configuration usingCodeLLDBto attach to127.0.0.1:1234.
Hardware Interrupts
IRQ
Interrupt Requests (IRQs) are used to identify hardware events.
They are represented as uint8_t values.
Userspace programs (such as a driver) can use syscalls to wait for an IRQ.
Before waiting for an IRQ, a userspace task must unmask it by calling
irq_unmask(irq). Afterwards, irq_wait(irq) blocks the task until the
hardware raises the interrupt. See syscalls.md for the full
syscall reference.
x86_64
Since APIC is exclusively in use (meaning no legacy PIC), there have been set some conventions for IRQ numbers. For each IOAPIC pin, there is a corresponding IRQ number. The pin’s number is always identical to the IRQ number.
The interrupt vectors in range 0x00-0x1F are used for CPU exceptions.
Due to legacy PIC and its conventions, 0x20-0x2F are not used,
as it could lead to some undesired behavior.
Therefore, 0x30 has been chosen as the vector offset for the IRQs.
That means for every IRQ, its interrupt vector is 0x30 + the IRQ number.
aarch64
On aarch64 (that is, 64-bit ARM architecture),
IRQs are used to represent shared peripheral interrupts (SPIs).
It has been decided that the IRQ numbers correspond to the SPI numbers.
Because interrupt ids (INTIDs) of SPIs start from 0x20,
as the range 0x00-0x0F is used for software generated interrupts (SGIs),
and 0x10-0x1F is used for private peripheral interrupts (PPIs),
the IRQ number of an SPI is 0x20 + INTID.
Syscall ABI Reference
Overview
Syscalls are the interface between userspace processes and the kernel. The
Aether syscall ABI is defined in TOML files under kernel/api/syscalls/:
syscalls.toml— the current list of all defined syscalls.errors.toml— all possible syscall error codes.
These files are used to automatically generate C headers and Rust bindings for userspace consumers.
The list of syscalls and their functionality will change as the project evolves. Refer to
syscalls.tomlanderrors.tomlfor the current authoritative definition rather than any derived documentation.
Calling Convention
Syscall number and arguments
The syscall number and arguments are passed in CPU registers:
x86_64
- Syscall number:
rax - Arguments (in order):
rdi,rsi,rdx,r10,r8
aarch64
- Syscall number:
x8 - Arguments (in order):
x0,x1,x2,x3,x4
Up to 5 arguments per syscall are currently supported. This limit may be increased in the future.
Return values
Every syscall returns two values:
- An error code — always present.
- A return value — present only if the syscall produces one.
An error code of 0 means success. Using the return value when the error
code is non-zero is undefined behavior.
All possible error codes for the current syscall set are defined in
kernel/api/syscalls/errors.toml.
Adding a New Syscall
-
Define the syscall in
kernel/api/syscalls/syscalls.toml:[syscalls.my_syscall] number = 0x0C # unique number 0–255 return_type = "uint64" # one of the valid types args = [ { name = "foo", type = "uint32" }, ] -
Implement the handler in
kernel/core/src/syscall_handler/. Create a new filesys_my_syscall.rsand implement the logic. Register the handler inkernel/core/src/syscall_handler/mod.rs. -
Add error codes (if needed) in
kernel/api/syscalls/errors.toml.
Aether Kernel and the Init Program Contract
Data provided by the kernel and initial stack
Upon process entry, the kernel provides the following resources mapped into the init address space:
- The
boot_infostructure. - The
initrd(tarball archive). - A single page-sized (4096 bytes) bootstrap stack.
Memory Layout Convention
All kernel-provided data shall reside at the high end of the userspace virtual address range (the “Top of the Lower Half”).
- Growth Direction: Data blocks are placed contiguously, starting from the highest available canonical address (e.g.,
0x00007FFFFFFFF000) and growing downwards. - Bootstrap Stack: The one-page initial stack is placed as the final (lowest address) item in this kernel-provided data block.
- Allocation Boundary: The lowest address of the bootstrap stack serves as the Stack Limit. The
initprogram can rely on this address as the hard upper bound for its own self-allocated “real” stack.
Execution State at Entry
- RSP/SP: Shall point to the top of the bootstrap stack.
- RDI/X0: Shall contain the virtual address of the
boot_infostructure. - Alignment: The initial stack pointer must be 16-byte aligned to satisfy the SysV ABI before the first function call.