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# The Little Kernel Embedded Operating System
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2013-02-09 13:25:38 -08:00
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2021-05-29 16:58:11 -07:00
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The LK kernel is an SMP-aware kernel designed for small systems ported to a variety of platforms and cpu architectures.
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2015-06-25 14:31:13 -07:00
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2016-02-20 11:47:50 -08:00
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See https://github.com/littlekernel/lk for the latest version.
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### High Level Features
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- Fully-reentrant multi-threaded preemptive kernel
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- Portable to many 32 and 64 bit architectures
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- Support for wide variety of embedded and larger platforms
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- Powerful modular build system
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- Large number of utility components selectable at build time
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### Supported architectures
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- ARM32
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- Cortex-M class cores (armv6m - armv8m)
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- ARMv7+ Cortex-A class cores
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- ARM64
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- ARMv8 and ARMv9 cores
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- RISC-V 32 and 64bit bit in machine and supervisor mode
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- x86-32 and x86-64
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- Motorola 68000
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- Microblaze
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- MIPS
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- OpenRISC 1000
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- VAX (experimental)
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### [TODO](docs/todo.md)
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### To build and test for ARM64 on linux
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2015-10-13 10:12:26 -07:00
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1. install or build qemu. v2.4 and above is recommended.
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2. install gcc for arm64 (see note 1)
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3. run scripts/do-qemuarm -6 (from the lk directory)
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4. you should see 'welcome to lk/MP'
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This will get you a interactive prompt into LK which is running in qemu
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arm64 machine 'virt' emulation. type 'help' for commands.
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Note: for ubuntu x86-64
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sudo apt-get install gcc-aarch64-linux-gnu
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or fetch a prebuilt toolchain from
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https://newos.org/toolchains/aarch64-elf-14.1.0-Linux-x86_64.tar.xz
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2025-01-08 10:33:34 -08:00
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### Building with LLVM-based toolchains
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To build LK with a LLVM-based toolchain you will have to manually specify the compiler and linker in the environemnt.
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Unlike GCC clang is a cross-compiler by default, so the target needs to be specified as part of the CC/CXX/CPP variables.
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For example, assuming LLVM is in `/opt/llvm/bin/`, the following command will work to build for 64-bit RISC-V:
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```
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gmake qemu-virt-riscv64-test 'CC=/opt/llvm/bin/clang --target=riscv64-unknown-elf' 'CPP=/opt/llvm/bin/clang-cpp --target=riscv64-unknown-elf' 'CXX=/opt/llvm/bin/clang++ --target=riscv64-unknown-elf' 'LD=/opt/llvm/bin/ld.lld' TOOLCHAIN_PREFIX=/opt/llvm/bin/llvm- CPPFILT=/opt/llvm/bin/llvm-cxxfilt
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```
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TOOLCHAIN_PREFIX can be set to use the LLVM binutils, but due to the different naming of `llvm-cxxfilt` vs `c++filt` it needs to be set explicitly.
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To build for AArch64 the command looks similar, just with a different `--target=` flag.
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```
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gmake qemu-virt-arm64-test 'CC=/opt/llvm/bin/clang --target=aarch64-unknown-elf' 'CPP=/opt/llvm/bin/clang-cpp --target=aarch64-unknown-elf' 'CXX=/opt/llvm/bin/clang++ --target=aarch64-unknown-elf' 'LD=/opt/llvm/bin/ld.lld' TOOLCHAIN_PREFIX=/opt/llvm/bin/llvm- CPPFILT=/opt/llvm/bin/llvm-cxxfilt
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```
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