On Mon, Feb 11, 2019 at 10:39:43AM +0900, Masahiro Yamada wrote: > On Fri, Feb 8, 2019 at 6:13 AM Joel Fernandes (Google) > <joel@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx> > > --- > > 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 + > > arch/x86/Makefile | 2 ++ > > init/Kconfig | 11 ++++++ > > kernel/.gitignore | 2 ++ > > kernel/Makefile | 29 +++++++++++++++ > > kernel/kheaders.c | 74 +++++++++++++++++++++++++++++++++++++++ > > scripts/gen_ikh_data.sh | 19 ++++++++++ > > scripts/strip-comments.pl | 8 +++++ > > 8 files changed, 146 insertions(+) > > create mode 100644 kernel/kheaders.c > > create mode 100755 scripts/gen_ikh_data.sh > > create mode 100755 scripts/strip-comments.pl > > > > diff --git a/Documentation/dontdiff b/Documentation/dontdiff > > index 2228fcc8e29f..05a2319ee2a2 100644 > > --- a/Documentation/dontdiff > > +++ b/Documentation/dontdiff > > @@ -151,6 +151,7 @@ int8.c > > kallsyms > > kconfig > > keywords.c > > +kheaders_data.h* > > ksym.c* > > ksym.h* > > kxgettext > > diff --git a/arch/x86/Makefile b/arch/x86/Makefile > > index 88398fdf8129..ad176d669da4 100644 > > --- a/arch/x86/Makefile > > +++ b/arch/x86/Makefile > > @@ -240,6 +240,8 @@ archmacros: > > ASM_MACRO_FLAGS = -Wa,arch/x86/kernel/macros.s > > export ASM_MACRO_FLAGS > > KBUILD_CFLAGS += $(ASM_MACRO_FLAGS) > > +IKH_EXTRA += arch/x86/kernel/macros.s > > +export IKH_EXTRA > > > This does not exist in any of released kernels. > > See commit 6ac389346e6 Ok, thanks fixed it in v2 which I just sent and rebased on linus master branch. - Joel
