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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/version.c
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/version.c')
-rw-r--r--init/version.c36
1 files changed, 13 insertions, 23 deletions
diff --git a/init/version.c b/init/version.c
index 3391c4051bf3..01d4ab05f0ba 100644
--- a/init/version.c
+++ b/init/version.c
@@ -18,24 +18,6 @@
#include <generated/utsrelease.h>
#include <linux/proc_ns.h>
-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
-};
-EXPORT_SYMBOL_GPL(init_uts_ns);
-
static int __init early_hostname(char *arg)
{
size_t bufsize = sizeof(init_uts_ns.name.nodename);
@@ -51,11 +33,6 @@ static int __init early_hostname(char *arg)
}
early_param("hostname", early_hostname);
-/* FIXED STRINGS! Don't touch! */
-const char linux_banner[] =
- "Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
- LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";
-
const char linux_proc_banner[] =
"%s version %s"
" (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ")"
@@ -63,3 +40,16 @@ const char linux_proc_banner[] =
BUILD_SALT;
BUILD_LTO_INFO;
+
+/*
+ * init_uts_ns and linux_banner contain the build version and timestamp,
+ * which are really fixed at the very last step of build process.
+ * They are compiled with __weak first, and without __weak later.
+ */
+
+struct uts_namespace init_uts_ns __weak;
+const char linux_banner[] __weak;
+
+#include "version-timestamp.c"
+
+EXPORT_SYMBOL_GPL(init_uts_ns);