On Tue, Apr 09, 2019 at 04:00:34PM +0100, Qais Yousef wrote: > On 04/08/19 17:28, Joel Fernandes (Google) wrote: > > Introduce in-kernel headers which are made available as an archive > > through proc (/proc/kheaders.tar.xz file). This archive makes it > > possible to run eBPF and other tracing programs tracing programs that > > need to extend the kernel for tracing purposes without any dependency on > > the file system having headers. > > > > On Android and embedded systems, it is common to switch kernels but not > > have kernel headers available on the file system. 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 best way to use this feature is by building it in. Several users > > have a need for this, when they switch debug kernels, they donot want to > > update the filesystem or worry about it where to store the headers on > > it. However, the feature is also buildable as a module in case the user > > desires it not being part of the kernel image. This makes it possible to > > load and unload the headers from memory 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. > > > > By having the archive available at a fixed location independent of > > filesystem dependencies and conventions, all debugging tools can > > directly refer to the fixed location for the archive, without concerning > > with where the headers on a typical filesystem which significantly > > simplifies tooling that needs kernel headers. > > > > The code to read the headers is based on /proc/config.gz code and uses > > the same technique to embed the headers. > > > > IKHD_ST and IKHD_ED markers as is to facilitate future patches that > > would extract the headers from a kernel or module image. > > > > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> > > I applied both patches on 5.1-rc2 and managed to compile and run several > eBPF programs using the untarred headers from /proc/kheaders.tar.xz on my juno. > > Tested-by: Qais Yousef <qais.yousef@xxxxxxx> Thank you Qais! Masahiro, if Ok with you now could you give your tag? thanks, - Joel > > --- > > > > v5 -> v6: (Masahiro Yamada suggestions mostly) > > - Dropped support for module building. > > - Rebuild archive if script changes. > > - Move archive file list to script. > > - Move build script to kernel directory. > > > > v4 -> v5: > > (v4 was Tested-by the following folks) > > Tested-by: qais.yousef@xxxxxxx > > Tested-by: dietmar.eggemann@xxxxxxx > > Tested-by: linux@xxxxxxxxxxxxxxxx > > Thanks! > > -- > Qais Yousef
