From 42306a155d227ba90624c190a28344d61d566f46 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 10 May 2019 15:12:05 +0900 Subject: [PATCH] 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 config/conf --allmodconfig Kconfig # # configuration written to .config # $ make allmodconfig config/conf --allmodconfig Kconfig # # No change to .config # Reported-by: Linus Torvalds Signed-off-by: Masahiro Yamada Reviewed-by: Greg Kroah-Hartman Signed-off-by: Christian Lamparter --- config/confdata.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/config/confdata.c b/config/confdata.c index da98566..da208c4 100644 --- a/config/confdata.c +++ b/config/confdata.c @@ -3,6 +3,7 @@ * Copyright (C) 2002 Roman Zippel */ +#include #include #include #include @@ -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. * @@ -934,6 +981,13 @@ 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)) -- 2.31.1