linux/scripts/build-version

#!/bin/sh
# SPDX-License-Identifier: GPL-2.0-only

prev_ver=$(cat .version 2>/dev/null) &&
ver=$(expr ${prev_ver} + 1 2>/dev/null) ||
ver=1

echo ${ver} > .version

echo ${ver}
kbuild: build init/built-in.a just once Kbuild builds init/built-in.a twice; first during the ordinary directory descending, second from scripts/link-vmlinux.sh. We do this because UTS_VERSION contains the build version and the timestamp. We cannot update it during the normal directory traversal since we do not yet know if we need to update vmlinux. UTS_VERSION is temporarily calculated, but omitted from the update check. Otherwise, vmlinux would be rebuilt every time. When Kbuild results in running link-vmlinux.sh, it increments the version number in the .version file and takes the timestamp at that time to really fix UTS_VERSION. However, updating the same file twice is a footgun. To avoid nasty timestamp issues, all build artifacts that depend on init/built-in.a are atomically generated in link-vmlinux.sh, where some of them do not need 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 <masahiroy@kernel.org> 2022-08-28 11:39:53 +09:00			`#!/bin/sh`
			`# SPDX-License-Identifier: GPL-2.0-only`

			`prev_ver=$(cat .version 2>/dev/null) &&`
			`ver=$(expr ${prev_ver} + 1 2>/dev/null) \|\|`
			`ver=1`

			`echo ${ver} > .version`

			`echo ${ver}`