On 08/11/2019 05:02, Hajime Tazaki wrote:
This RFC patchset is to ask opinions from folks, whether LKL codes is good to integrate into UML code base. We wish to have any kind of feedback from your kind reviews. There are numbers of commits which should be asked for reviews to other mailing lists; we will do it later once we got discussed in this mailing list. # sorry for the long list of patches: we can make it smaller by only including basic set of LKL (e.g., removing foreign OS support, etc) if you wish. rfc v2: - use UMMODE instead of SUBARCH to switch UML or LKL - tools/lkl directory is still there. I confirmed we can move under arch/um (e.g., arch/um/lkl/hosts). I will move it IF this is preferable. - drop several patches involved non-uml directory - drop several patches which are not required - refine commit logs - document updated 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 originally implemented as an architecture port in arch/lkl, but this series of commits tries to integrate this into arch/um as one of the mode of UML. This was discussed during RFC email of LKL (*1). The latest LKL version can be found at https://github.com/lkl/linux Milestone ========= This patches is just a first step toward upstreaming *library mode* of Linux kernel, but we think we need to have several steps toward our goal, describing in the below. 1. Put LKL code under arch/um (arch/um/lkl), and build it in a separate way from UML. 2. Share common parts of implementation between UML and LKL. 3. Reimplement UML features with LKL API (if we wish) For the step 1, we put LKL as one of UMMODE in order to make less effort to integrate (make ARCH=um UMMODE=library). The modification to existing UML code is trying to be minimized. The RFC patches also includes and a bit of step 2 as a proof of possibility to share the code. For this, we used the virtio device code of LKL and use it from UML by enabling virtio-mmio driver with UML code. Building LKL the host library and LKL applications ================================================== % cd tools/lkl % make will build LKL as a object file, it will install it in tools/lkl/lib together with the headers files in tools/lkl/include then will build the host library, tests and a few of application examples: * tests/boot - a simple applications that uses LKL and exercises the basic LKL APIs * tests/net-test - a simple applications that uses network feature of LKL and exercises the basic network-related APIs * fs2tar - a tool that converts a filesystem image to a tar archive * cptofs/cpfromfs - a tool that copies files to/from a filesystem image % make run-tests should run the above `tests/boot` and `tests/net-test` and report errors if there are any. Supported hosts =============== Currently LKL supports POSIX and Windows userspace applications. New hosts can be added relatively easy if the host supports gcc and GNU ld. Previous versions of LKL supported Windows kernel and Haiku kernel hosts, and we also have WIP patches (not included in this RFC) with rump-hypercall interface, used in UEFI, as well as macOS userspace (part of POSIX?). There is also musl-libc port for LKL, which might be interested in for some folks. Further readings about LKL ========================= - Discussion in github LKL issue https://github.com/lkl/linux/issues/304 - LKL (an article) https://www.researchgate.net/profile/Nicolae_Tapus2/publication/224164682_LKL_The_Linux_kernel_library/links/02bfe50fd921ab4f7c000000.pdf *1 RFC email to LKML (back in 2015) https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1012277.html Please review the following changes for suitability for inclusion. If you have any objections or suggestions for improvement, please respond to the patches. If you agree with the changes, please provide your Acked-by. The following changes since commit 73625ed66389d4c620520058d828f43a93ab4d0c: um: irq: Fix LAST_IRQ usage in init_IRQ() (2019-09-16 08:38:58 +0200) are available in the Git repository at: git://github.com/thehajime/linux 61b15bfb52c7f1f066685c90a1cfe8346b3faec9 https://github.com/thehajime/linux/tree/upstream-to-uml-5.5-rc1-v2 Andreas Abel (1): kallsyms: Add a config option to select section for kallsyms Hajime Tazaki (6): lkl: add system call hijack support scripts: revert CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX patches lkl: Android ARM (arm/arm64) support um lkl: add CI tests um: use lkl virtio_net_tap device as UML device um: add lkl virtio-blk device Octavian Purdila (29): asm-generic: atomic64: allow using generic atomic64 on 64bit platforms arch: add __SYSCALL_DEFINE_ARCH lkl: architecture skeleton for Linux kernel library lkl: host interface lkl: memory handling lkl: kernel threads support lkl: interrupt support lkl: system call interface and application API lkl: timers, time and delay support lkl: memory mapped I/O support lkl: basic kernel console support lkl: initialization and cleanup lkl: plug in the build system lkl tools: skeleton for host side library, tests and tools lkl tools: host lib: add utilities functions lkl tools: host lib: memory mapped I/O helpers lkl tools: host lib: virtio devices lkl tools: host lib: virtio block device lkl tools: host lib: filesystem helpers lkl tools: host lib: posix host operations lkl tools: "boot" test lkl tools: tool that reads/writes to/from a filesystem image lkl tools: tool that converts a filesystem image to tar lkl tools: virtio: add network device support checkpatch: avoid showing BIT_ULL warnings for tools/ files lkl tools: add lklfuse lkl: add documentation lkl: add support for Windows hosts lkl tools: add support for Windows host Thomas Liebetraut (1): tools: Add the lkl host library to the common tools Makefile .circleci/config.yml | 276 ++++++ Documentation/virt/uml/lkl.txt | 453 ++++++++++ MAINTAINERS | 8 + Makefile | 4 +- arch/Kconfig | 6 + arch/um/Kconfig | 32 +- arch/um/Makefile | 151 +--- arch/um/Makefile.um | 152 ++++ arch/um/configs/x86_64_defconfig | 6 + arch/um/include/asm/Kbuild | 1 + arch/um/include/asm/io.h | 4 + arch/um/kernel/syscall.c | 53 ++ arch/um/lkl/.gitignore | 2 + arch/um/lkl/Kconfig | 91 ++ arch/um/lkl/Kconfig.debug | 0 arch/um/lkl/Makefile | 69 ++ arch/um/lkl/auto.conf | 1 + arch/um/lkl/configs/lkl_defconfig | 91 ++ arch/um/lkl/include/asm/Kbuild | 80 ++ arch/um/lkl/include/asm/bitsperlong.h | 11 + arch/um/lkl/include/asm/byteorder.h | 7 + arch/um/lkl/include/asm/cpu.h | 14 + arch/um/lkl/include/asm/elf.h | 15 + arch/um/lkl/include/asm/host_ops.h | 10 + arch/um/lkl/include/asm/io.h | 104 +++ arch/um/lkl/include/asm/irq.h | 15 + arch/um/lkl/include/asm/mutex.h | 7 + arch/um/lkl/include/asm/page.h | 14 + arch/um/lkl/include/asm/pgtable.h | 62 ++ arch/um/lkl/include/asm/processor.h | 60 ++ arch/um/lkl/include/asm/ptrace.h | 25 + arch/um/lkl/include/asm/sched.h | 23 + 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scripts/adjust_autoksyms.sh | 6 + scripts/basic/.gitignore | 1 + scripts/checkpatch.pl | 13 +- scripts/depmod.sh | 25 +- scripts/genksyms/genksyms.c | 11 +- scripts/kallsyms.c | 54 +- scripts/kconfig/.gitignore | 1 + scripts/link-vmlinux.sh | 10 + scripts/mod/.gitignore | 1 + scripts/mod/modpost.c | 30 +- tools/Makefile | 11 +- tools/lkl/.gitignore | 15 + tools/lkl/Build | 6 + tools/lkl/Makefile | 130 +++ tools/lkl/Makefile.autoconf | 114 +++ tools/lkl/Targets | 25 + tools/lkl/bin/lkl-hijack.sh | 23 + tools/lkl/cptofs.c | 635 ++++++++++++++ tools/lkl/fs2tar.c | 410 +++++++++ tools/lkl/include/.gitignore | 1 + tools/lkl/include/lkl.h | 928 +++++++++++++++++++++ tools/lkl/include/lkl_config.h | 61 ++ tools/lkl/include/lkl_host.h | 160 ++++ tools/lkl/include/mingw32/sys/socket.h | 4 + tools/lkl/lib/.gitignore | 3 + tools/lkl/lib/Build | 26 + tools/lkl/lib/Makefile | 33 + tools/lkl/lib/config.c | 793 ++++++++++++++++++ tools/lkl/lib/dbg.c | 300 +++++++ tools/lkl/lib/dbg_handler.c | 44 + 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create mode 100644 tools/lkl/tests/test.c create mode 100644 tools/lkl/tests/test.h create mode 100644 tools/lkl/tests/test.sh create mode 100644 tools/lkl/tests/valgrind.supp create mode 100755 tools/lkl/tests/valgrind2xunit.py
I am reading the patch-set and I have a recurring question as I read it. It applies to IRQ, mmap IO, timers, devices, etc
The question is: "What is the unerlying req to replace the existing UML code for the library".
F.e timers in UML have been moved to an underlying POSIX timers call now and that can probably work on any system that offers it. If there is some presentation/documentation/etc material which I can read which goes through the actual choices it will be very helpful.
The same question applies the other way around too. I like the hostops approach, we can probably adopt some of that in UML proper to make it more portable and easier to have alternative implementations for the underlying host side operations.
-- Anton R. Ivanov Cambridgegreys Limited. Registered in England. Company Number 10273661 https://www.cambridgegreys.com/
