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))