Buildresult: kbuild/x86_64-defconfig/x86_64-gcc8 built on Apr 8 2020, 01:50

kisskb

Revisions | Branches | Compilers | Configs | Build Results | Build Failures |

Status:	OK
Date/Time:	Apr 8 2020, 01:50
Duration:	0:02:21.848527
Builder:	ka2
Revision:	kbuild: link lib-y objects to vmlinux forcibly when CONFIG_MODULES=y (`58bb4f7d4970e92c2400208a1b48aae3b2853e5c)`
Target:	kbuild/x86_64-defconfig/x86_64-gcc8
Branch:	kbuild
Compiler:	x86_64-gcc8 (x86_64-linux-gcc (GCC) 8.1.0 / GNU ld (GNU Binutils) 2.30)
Config:	defconfig (download)
Log:	Download original No warnings found in log. Full Log # git rev-parse -q --verify 58bb4f7d4970e92c2400208a1b48aae3b2853e5c^{commit} 58bb4f7d4970e92c2400208a1b48aae3b2853e5c already have revision, skipping fetch # git checkout -q -f -B kisskb 58bb4f7d4970e92c2400208a1b48aae3b2853e5c # git clean -qxdf # < git log -1 # commit 58bb4f7d4970e92c2400208a1b48aae3b2853e5c # Author: Masahiro Yamada <masahiroy@kernel.org> # Date: Thu Mar 12 07:37:25 2020 +0900 # # kbuild: link lib-y objects to vmlinux forcibly when CONFIG_MODULES=y # # Kbuild supports not only obj-y but also lib-y to list objects linked to # vmlinux. # # The difference between them is that all the objects from obj-y are # forcibly linked to vmlinux, whereas the objects from lib-y are linked # as needed; if there is no user of a lib-y object, it is not linked. # # lib-y is intended to list utility functions that may be called from all # over the place (and may be unused at all), but it is a problem for # EXPORT_SYMBOL(). Even if there is no call-site in the vmlinux, we need # to keep exported symbols for the use from loadable modules. # # Commit 7f2084fa55e6 ("[kbuild] handle exports in lib-y objects reliably") # worked around it by linking a dummy object, lib-ksyms.o, which contains # references to all the symbols exported from lib.a in that directory. # It uses the linker script command, EXTERN. Unfortunately, the meaning of # EXTERN of ld.lld is different from that of ld.bfd. Therefore, this does # not work with LD=ld.lld (CBL issue #515). # # Anyway, the build rule of lib-ksyms.o is somewhat tricky. So, I want to # get rid of it. # # At first, I was thinking of accumulating lib-y objects into obj-y # (or even replacing lib-y with obj-y entirely), but the lib-y syntax # is used beyond the ordinary use in lib/ and arch/*/lib/. # # Examples: # # - drivers/firmware/efi/libstub/Makefile builds lib.a, which is linked # into vmlinux in the own way (arm64), or linked to the decompressor # (arm, x86). # # - arch/alpha/lib/Makefile builds lib.a which is linked not only to # vmlinux, but also to bootloaders in arch/alpha/boot/Makefile. # # - arch/xtensa/boot/lib/Makefile builds lib.a for use from # arch/xtensa/boot/boot-redboot/Makefile. # # One more thing, adding everything to obj-y would increase the vmlinux # size of allnoconfig (or tinyconfig). # # For less impact, I tweaked the destination of lib.a at the top Makefile; # when CONFIG_MODULES=y, lib.a goes to KBUILD_VMLINUX_OBJS, which is # forcibly linked to vmlinux, otherwise lib.a goes to KBUILD_VMLINUX_LIBS # as before. # # The size impact for normal usecases is quite small since at lease one # symbol in every lib-y object is eventually called by someone. In case # you are intrested, here are the figures. # # x86_64_defconfig: # # text data bss dec hex filename # 19566602 5422072 1589328 26578002 1958c52 vmlinux.before # 19566932 5422104 1589328 26578364 1958dbc vmlinux.after # # The case with the biggest impact is allnoconfig + CONFIG_MODULES=y. # # ARCH=x86 allnoconfig + CONFIG_MODULES=y: # # text data bss dec hex filename # 1175162 254740 1220608 2650510 28718e vmlinux.before # 1177974 254836 1220608 2653418 287cea vmlinux.after # # Hopefully this is still not a big deal. The per-file trimming with the # static library is not so effective after all. # # If fine-grained optimization is desired, some architectures support # CONFIG_LD_DEAD_CODE_DATA_ELIMINATION, which trims dead code per-symbol # basis. When LTO is supported in mainline, even better optimization will # be possible. # # Link: https://github.com/ClangBuiltLinux/linux/issues/515 # Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> # Reported-by: kbuild test robot <lkp@intel.com> # Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> # < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux-ld --version # < git log --format=%s --max-count=1 58bb4f7d4970e92c2400208a1b48aae3b2853e5c # < make -s -j 48 ARCH=x86 O=/kisskb/build/kbuild_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux- x86_64_defconfig # < make -s -j 48 ARCH=x86 O=/kisskb/build/kbuild_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux- help # make -s -j 48 ARCH=x86 O=/kisskb/build/kbuild_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux- olddefconfig # make -s -j 48 ARCH=x86 O=/kisskb/build/kbuild_x86_64_defconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux- Completed OK # rm -rf /kisskb/build/kbuild_x86_64_defconfig_x86_64-gcc8 # Build took: 0:02:21.848527

© Michael Ellerman 2006-2018.