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authorMasahiro Yamada <yamada.masahiro@socionext.com>2019-05-10 15:12:05 +0900
committerMasahiro Yamada <yamada.masahiro@socionext.com>2019-05-11 02:15:49 +0900
commit67424f61f8132215514e03ce1760d30356ac56d7 (patch)
tree9e6c1bf8f665965213eace73da8c50d6839b55e3
parentceb7f3296ea1fa652d68e5ecb0facf5fba19a554 (diff)
kconfig: do not write .config if the content is the same
Kconfig updates the .config when it exits even if its content is exactly the same as before. Since its timestamp becomes newer than that of other build artifacts, additional processing is invoked, which is annoying. - syncconfig is invoked to update include/config/auto.conf, etc. - kernel/configs.o is recompiled if CONFIG_IKCONFIG is enabled, then vmlinux is relinked as well. If the .config is not changed at all, we do not have to even touch it. Just bail out showing "No change to .config". $ make allmodconfig scripts/kconfig/conf --allmodconfig Kconfig # # configuration written to .config # $ make allmodconfig scripts/kconfig/conf --allmodconfig Kconfig # # No change to .config # Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--scripts/kconfig/confdata.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index 9fd6430c93d2..399973e35533 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -3,6 +3,7 @@
* Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
*/
+#include <sys/mman.h>
#include <sys/stat.h>
#include <ctype.h>
#include <errno.h>
@@ -36,6 +37,52 @@ static bool is_dir(const char *path)
return S_ISDIR(st.st_mode);
}
+/* return true if the given two files are the same, false otherwise */
+static bool is_same(const char *file1, const char *file2)
+{
+ int fd1, fd2;
+ struct stat st1, st2;
+ void *map1, *map2;
+ bool ret = false;
+
+ fd1 = open(file1, O_RDONLY);
+ if (fd1 < 0)
+ return ret;
+
+ fd2 = open(file2, O_RDONLY);
+ if (fd2 < 0)
+ goto close1;
+
+ ret = fstat(fd1, &st1);
+ if (ret)
+ goto close2;
+ ret = fstat(fd2, &st2);
+ if (ret)
+ goto close2;
+
+ if (st1.st_size != st2.st_size)
+ goto close2;
+
+ map1 = mmap(NULL, st1.st_size, PROT_READ, MAP_PRIVATE, fd1, 0);
+ if (map1 == MAP_FAILED)
+ goto close2;
+
+ map2 = mmap(NULL, st2.st_size, PROT_READ, MAP_PRIVATE, fd2, 0);
+ if (map2 == MAP_FAILED)
+ goto close2;
+
+ if (bcmp(map1, map2, st1.st_size))
+ goto close2;
+
+ ret = true;
+close2:
+ close(fd2);
+close1:
+ close(fd1);
+
+ return ret;
+}
+
/*
* Create the parent directory of the given path.
*
@@ -888,6 +935,13 @@ next:
fclose(out);
if (*tmpname) {
+ if (is_same(name, tmpname)) {
+ conf_message("No change to %s", name);
+ unlink(tmpname);
+ sym_set_change_count(0);
+ return 0;
+ }
+
snprintf(oldname, sizeof(oldname), "%s.old", name);
rename(name, oldname);
if (rename(tmpname, name))