On Tue, Feb 19, 2019 at 01:42:13PM +0900, Masahiro Yamada wrote: [..] > > > > 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 set looks good to me and since the main use case is building bpf progs > > > I can route it via bpf-next tree if there are no objections. > > > Masahiro, could you please ack it? > > > > > > Honestly, I was not tracking this thread > > since I did not know I was responsible for this. > > > > > > I just started to take a closer look, then immediately got scared. > > > > This version is not mature enough for the merge. > > > > > > > > First of all, this patch cannot be compiled out-of-tree (O= option). > > > > > > I do not know why 0-day bot did not catch this apparent breakage. > > > > > > $ make -j8 O=hoge > > make[1]: Entering directory '/home/masahiro/workspace/bsp/linux/hoge' > > GEN Makefile > > Using .. as source for kernel > > DESCEND objtool > > CALL ../scripts/checksyscalls.sh > > CHK include/generated/compile.h > > make[2]: *** No rule to make target 'Module.symvers', needed by > > 'kernel/kheaders_data.txz'. Stop. > > make[2]: *** Waiting for unfinished jobs.... > > /home/masahiro/workspace/bsp/linux/Makefile:1043: recipe for target > > 'kernel' failed > > make[1]: *** [kernel] Error 2 > > make[1]: *** Waiting for unfinished jobs.... > > make[1]: Leaving directory '/home/masahiro/workspace/bsp/linux/hoge' > > Makefile:152: recipe for target 'sub-make' failed > > make: *** [sub-make] Error 2 > > > > > I saw this build error for in-tree building as well. > > We cannot build this from a pristine source tree. > > For example, I observed the build error in the following procedure. > > $ make mrproper > $ make defconfig > Set CONFIG_IKHEADERS_PROC=y > $ make > > > > > Module.symvers is generated in the modpost stage > (the very last stage of build). > > But, vmlinux depends on kernel/kheaders_data.txz, > which includes Module.symvers. > > So, this is not so simple since it is a circular dependency... I guess I was not building a pristine tree either and missed this circular dependency :-/ . Any ideas on how we can fix the Module.symvers issue? One idea is to reserve the space in the binaries, but only populate the space reserved in the binary *after* the modpost stage, once the archive is ready.. thanks, - Joel
