kconfig: allow specifying the seed for randconfig

For reproducibility, it can be useful to be able to specify the
seed to use to seed the RNG.

Add a new KCONFIG_SEED environment variable which can be set to
the seed to use:
    $ make KCONFIG_SEED=42 randconfig
    $ sha1sum .config
    70a128c8dcc61303069e1be352cce64114dfcbca  .config
    $ make KCONFIG_SEED=42 randconfig
    $ sha1sum .config
    70a128c8dcc61303069e1be352cce64114dfcbca  .config

It's very usefull for eg. debugging the kconfig parser.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>

diff --git a/config/conf.c b/config/conf.c
index cdbdb1129eeb3067b26451c0851d014d709a4ad2..ea4080d6eaab0b93b3752cd858604571547ad353 100644 (file)
--- a/config/conf.c
+++ b/config/conf.c
@@ -13,6 +13,7 @@
 #include <getopt.h>
 #include <sys/stat.h>
 #include <sys/time.h>
+#include <errno.h>
 
 #include "lkc.h"
 
@@ -498,14 +499,23 @@ int main(int ac, char **av)
                {
                        struct timeval now;
                        unsigned int seed;
+                       char *seed_env;
 
                        /*
                         * Use microseconds derived seed,
                         * compensate for systems where it may be zero
                         */
                        gettimeofday(&now, NULL);
-
                        seed = (unsigned int)((now.tv_sec + 1) * (now.tv_usec + 1));
+
+                       seed_env = getenv("KCONFIG_SEED");
+                       if( seed_env && *seed_env ) {
+                               char *endp;
+                               int tmp = (int)strtol(seed_env, &endp, 10);
+                               if (*endp == '\0') {
+                                       seed = tmp;
+                               }
+                       }
                        srand(seed);
                        break;
                }