2df8220c - kbuild: build init/built-in.a just once

Sun, 28 Aug 2022 02:39:53 +0000

kbuild: build init/built-in.a just onceKbuild builds init/built-in.a twice; first during the ordinarydirectory descending, second from scripts/link-vmlinux.sh.We do this because UTS_VERSION contains the build version and thetimestamp. We cannot update it during the normal directory traversalsince we do not yet know if we need to update vmlinux. UTS_VERSION istemporarily calculated, but omitted from the update check. Otherwise,vmlinux would be rebuilt every time.When Kbuild results in running link-vmlinux.sh, it increments theversion number in the .version file and takes the timestamp at thattime to really fix UTS_VERSION.However, updating the same file twice is a footgun. To avoid nastytimestamp issues, all build artifacts that depend on init/built-in.aare atomically generated in link-vmlinux.sh, where some of them do notneed rebuilding.To fix this issue, this commit changes as follows:[1] Split UTS_VERSION out to include/generated/utsversion.h from include/generated/compile.h include/generated/utsversion.h is generated just before the vmlinux link. It is generated under include/generated/ because some decompressors (s390, x86) use UTS_VERSION.[2] Split init_uts_ns and linux_banner out to init/version-timestamp.c from init/version.c init_uts_ns and linux_banner contain UTS_VERSION. During the ordinary directory descending, they are compiled with __weak and used to determine if vmlinux needs relinking. Just before the vmlinux link, they are compiled without __weak to embed the real version and timestamp.Signed-off-by: Masahiro Yamada List of files: /linux-6.15/init/.gitignore

Changes in .gitignore

2df8220c - kbuild: build init/built-in.a just once