From 2df8220cc511326508ec4da2f43ef69311bdd7b9 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 28 Aug 2022 11:39:53 +0900 Subject: 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 --- init/version-timestamp.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 init/version-timestamp.c (limited to 'init/version-timestamp.c') diff --git a/init/version-timestamp.c b/init/version-timestamp.c new file mode 100644 index 000000000000..179e93bae539 --- /dev/null +++ b/init/version-timestamp.c @@ -0,0 +1,31 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include +#include +#include +#include +#include +#include +#include + +struct uts_namespace init_uts_ns = { + .ns.count = REFCOUNT_INIT(2), + .name = { + .sysname = UTS_SYSNAME, + .nodename = UTS_NODENAME, + .release = UTS_RELEASE, + .version = UTS_VERSION, + .machine = UTS_MACHINE, + .domainname = UTS_DOMAINNAME, + }, + .user_ns = &init_user_ns, + .ns.inum = PROC_UTS_INIT_INO, +#ifdef CONFIG_UTS_NS + .ns.ops = &utsns_operations, +#endif +}; + +/* FIXED STRINGS! Don't touch! */ +const char linux_banner[] = + "Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@" + LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n"; -- cgit v1.2.3