Messages in this thread | | | Subject | Re: [PATCH v2 1/2] Provide in-kernel headers for making it easy to extend the kernel | From | Karim Yaghmour <> | Date | Wed, 13 Feb 2019 17:50:10 -0500 |
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On 2/11/19 9:35 AM, Joel Fernandes (Google) wrote: > Introduce in-kernel headers and other artifacts which are made available > as an archive through proc (/proc/kheaders.txz file). This archive makes > it possible to build kernel modules, run eBPF programs, and other > tracing programs that need to extend the kernel for tracing purposes > without any dependency on the file system having headers and build > artifacts. > > On Android and embedded systems, it is common to switch kernels but not > have kernel headers available on the file system. Raw kernel headers > also cannot be copied into the filesystem like they can be on other > distros, due to licensing and other issues. There's no linux-headers > package on Android. Further once a different kernel is booted, any > headers stored on the file system will no longer be useful. By storing > the headers as a compressed archive within the kernel, we can avoid these > issues that have been a hindrance for a long time. > > The feature is also buildable as a module just in case the user desires > it not being part of the kernel image. This makes it possible to load > and unload the headers on demand. A tracing program, or a kernel module > builder can load the module, do its operations, and then unload the > module to save kernel memory. The total memory needed is 3.8MB. > > The code to read the headers is based on /proc/config.gz code and uses > the same technique to embed the headers. > > To build a module, the below steps have been tested on an x86 machine: > modprobe kheaders > rm -rf $HOME/headers > mkdir -p $HOME/headers > tar -xvf /proc/kheaders.txz -C $HOME/headers >/dev/null > cd my-kernel-module > make -C $HOME/headers M=$(pwd) modules > rmmod kheaders > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Karim Yaghmour <karim.yaghmour@opersys.com>
> --- > > Changes since v1: > - removed IKH_EXTRA variable, not needed (Masahiro Yamada) > - small fix ups to selftest > - added target to main Makefile etc > - added MODULE_LICENSE to test module > - made selftest more quiet > > Changes since RFC: > Both changes bring size down to 3.8MB: > - use xz for compression > - strip comments except SPDX lines > - Call out the module name in Kconfig > - Also added selftests in second patch to ensure headers are always > working. > > Documentation/dontdiff | 1 + > init/Kconfig | 11 ++++++ > kernel/.gitignore | 2 ++ > kernel/Makefile | 27 ++++++++++++++ > kernel/kheaders.c | 74 +++++++++++++++++++++++++++++++++++++++ > scripts/gen_ikh_data.sh | 19 ++++++++++ > scripts/strip-comments.pl | 8 +++++ > 7 files changed, 142 insertions(+) > create mode 100644 kernel/kheaders.c > create mode 100755 scripts/gen_ikh_data.sh > create mode 100755 scripts/strip-comments.pl
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-- Karim Yaghmour CEO - Opersys inc. / www.opersys.com http://twitter.com/karimyaghmour
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