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authorMasahiro Yamada <masahiroy@kernel.org>2022-08-28 11:39:53 +0900
committerMasahiro Yamada <masahiroy@kernel.org>2022-09-29 04:40:15 +0900
commit2df8220cc511326508ec4da2f43ef69311bdd7b9 (patch)
treea28de6a06de6fb9353f6bb7e7fd91cee01027305 /init/.gitignore
parent561daaacb45eee3ccbe581da38c34ece77496312 (diff)
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>
Diffstat (limited to 'init/.gitignore')
-rw-r--r--init/.gitignore2
1 files changed, 2 insertions, 0 deletions
diff --git a/init/.gitignore b/init/.gitignore
new file mode 100644
index 000000000000..cbbe270cec00
--- /dev/null
+++ b/init/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+/utsversion-tmp.h