A document describing brief introduction of LKL, why it is needed, and how it is used is added. The document is located under uml/ directory. Signed-off-by: Octavian Purdila <tavi.purdila@xxxxxxxxx> Signed-off-by: Hajime Tazaki <thehajime@xxxxxxxxx> --- Documentation/virt/uml/lkl.txt | 48 ++++++++++++++++++++++++++++++++++ MAINTAINERS | 10 +++++++ 2 files changed, 58 insertions(+) create mode 100644 Documentation/virt/uml/lkl.txt diff --git a/Documentation/virt/uml/lkl.txt b/Documentation/virt/uml/lkl.txt new file mode 100644 index 000000000000..4942b7f093c5 --- /dev/null +++ b/Documentation/virt/uml/lkl.txt @@ -0,0 +1,48 @@ + +Introduction +============ + +Library mode of UML, a.k.a. LKL (Linux Kernel Library), is aiming to allow +reusing the Linux kernel code as extensively as possible with minimal effort and +reduced maintenance overhead. + +Examples of how LKL can be used are: creating userspace applications (running on +Linux and other operating systems) that can read or write Linux filesystems or +can use the Linux networking stack, creating kernel drivers for other operating +systems that can read Linux filesystems, bootloaders support for reading/writing +Linux filesystems, etc. + +With LKL, the kernel code is compiled into an object file that can be directly +linked by applications. The API offered by LKL is based on the Linux system call +interface. + +LKL is implemented as one of the mode of UML (arch/um), and it internally uses +sub-architecture (SUBARCH) of UML (SUBARCH=lkl). It uses host operations +defined by the application or a host library (tools/um). + + +Supported hosts +=============== + +The supported host for now is Linux (x86 architecture) userspace applications. + + +Building LKL the host library and LKL applications +================================================== + + $ make ARCH=um SUBARCH=lkl defconfig + $ make ARCH=um SUBARCH=lkl + +will build LKL as a object file, it will install it in tools/um together with +the headers files in tools/um/include then will build the host library, tests +and a few of application examples: + +* tools/testing/selftests/um/boot.c - a simple applications that uses LKL and + exercises the basic LKL APIs + +* tools/testing/selftests/um/disk.c - a simple applications that tests LKL and + exercises the basic filesystem-related LKL APIs + +Those tests can run with the following kselftest command: + + $ make ARCH=um SUBARCH=lkl TARGETS="um" kselftest diff --git a/MAINTAINERS b/MAINTAINERS index 00836f6452f0..8587a9715020 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18613,6 +18613,16 @@ F: arch/um/ F: arch/x86/um/ F: fs/hostfs/ +USER-MODE LINUX (UML) LIBRARY MODE +M: Octavian Purdila <tavi.purdila@xxxxxxxxx> +M: Hajime Tazaki <thehajime@xxxxxxxxx> +L: linux-um@xxxxxxxxxxxxxxxxxxx +S: Maintained +T: https://github.com/lkl/linux +F: arch/um/lkl/ +F: tools/testing/selftests/um/ +F: tools/um/ + USERSPACE COPYIN/COPYOUT (UIOVEC) M: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> S: Maintained -- 2.21.0 (Apple Git-122.2)
