On Fri, Feb 15, 2019 at 11:48 PM Alexei Starovoitov alexei.starovoitov@gmail.com wrote:
On Mon, Feb 11, 2019 at 09:35:59AM -0500, Joel Fernandes (Google) wrote:
Introduce in-kernel headers and other artifacts which are made available as an archive through proc (/proc/kheaders.txz file).
The extension '.txz' is not used in kernel code.
'.tar.xz' is used for 'tarxz-pkg', 'perf-tarxz-src-pkg' etc.
$ git grep '.txz' $ git grep '.tar.xz' Documentation/admin-guide/README.rst: xz -cd linux-4.X.tar.xz | tar xvf - arch/x86/crypto/camellia-aesni-avx-asm_64.S: * http://koti.mbnet.fi/axh/crypto/camellia-BSD-1.2.0-aesni1.tar.xz crypto/testmgr.h: * https://bench.cr.yp.to/supercop/supercop-20170228.tar.xz crypto/testmgr.h: * https://bench.cr.yp.to/supercop/supercop-20170228.tar.xz crypto/testmgr.h: * https://bench.cr.yp.to/supercop/supercop-20170228.tar.xz crypto/testmgr.h: * https://bench.cr.yp.to/supercop/supercop-20170228.tar.xz crypto/testmgr.h: * https://bench.cr.yp.to/supercop/supercop-20170228.tar.xz scripts/package/Makefile: @echo ' perf-tarxz-src-pkg - Build $(perf-tar).tar.xz source tarball' tools/testing/selftests/gen_kselftest_tar.sh: ext=".tar.xz"
I prefer '.tar.xz' for consistency.
BTW, have you ever looked at scripts/extract-ikconfig?
You added IKHD_ST and IKHD_ED just to mimic kernel/configs.c
It is currently pointless without the extracting tool, but you might think it is useful to extract headers from vmlinux or the module without mounting procfs.
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 was able to compile it in-tree but it makes the incremental build extremely slow.
(Here, the incremental build means "make" without changing any code after the full build.)
Before this patch, "make -j8" took 11 sec on my machine.
real 0m11.777s user 0m16.608s sys 0m5.164s
After this patch, x86_64_defconfig + CONFIG_IKHEADERS_PROC=y takes 53 sec for me since kernel/kheaders_data.txz is regenerated every time even when you did not touch any source file.
$ time make -j8 DESCEND objtool CALL scripts/checksyscalls.sh CHK include/generated/compile.h GEN kernel/kheaders_data.txz UPD kernel/kheaders_data.h CC kernel/kheaders.o AR kernel/built-in.a GEN .version CHK include/generated/compile.h UPD include/generated/compile.h CC init/version.o AR init/built-in.a AR built-in.a LD vmlinux.o MODPOST vmlinux.o KSYM .tmp_kallsyms1.o KSYM .tmp_kallsyms2.o LD vmlinux SORTEX vmlinux SYSMAP System.map Building modules, stage 2. CC arch/x86/boot/version.o MODPOST 17 modules VOFFSET arch/x86/boot/compressed/../voffset.h OBJCOPY arch/x86/boot/compressed/vmlinux.bin RELOCS arch/x86/boot/compressed/vmlinux.relocs CC arch/x86/boot/compressed/kaslr.o GZIP arch/x86/boot/compressed/vmlinux.bin.gz CC arch/x86/boot/compressed/misc.o MKPIGGY arch/x86/boot/compressed/piggy.S AS arch/x86/boot/compressed/piggy.o LD arch/x86/boot/compressed/vmlinux ZOFFSET arch/x86/boot/zoffset.h OBJCOPY arch/x86/boot/vmlinux.bin AS arch/x86/boot/header.o LD arch/x86/boot/setup.elf OBJCOPY arch/x86/boot/setup.bin BUILD arch/x86/boot/bzImage Setup is 15612 bytes (padded to 15872 bytes). System is 12673 kB CRC 697aaf88 Kernel: arch/x86/boot/bzImage is ready (#6)
real 0m53.024s user 0m32.076s sys 0m9.296s
Also, I notice $(ARCH) must be fixed to $(SRCARCH), but that is one of minor issues.
We should take time for careful review and test.
Please give me more time for thorough review.
-- Best Regards Masahiro Yamada