[PATCH 7/8] kconfig: allow specifying the seed for randconfig

Yann E. MORIN
2013-04-24T22:30:48Z

From: "Yann E. MORIN" <yann.morin.1998@free.fr>

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>
---
Documentation/kbuild/kconfig.txt | 9 +++++++++
scripts/kconfig/conf.c | 12 +++++++++++-
2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Documentation/kbuild/kconfig.txt b/Documentation/kbuild/kconfig.txt
index b8b77bb..dbf746b 100644
--- a/Documentation/kbuild/kconfig.txt
+++ b/Documentation/kbuild/kconfig.txt
@@ -90,6 +90,15 @@ disable the options that are explicitly listed in the specified
mini-config files.

______________________________________________________________________
+Environment variables for 'randconfig'
+
+KCONFIG_SEED
+--------------------------------------------------
+You can set this to the integer value used to seed the RNG, if you want
+to somehow debug the behaviour of the kconfig parser/frontends.
+If not set, the current time will be used.
+
+______________________________________________________________________
Environment variables for 'silentoldconfig'

KCONFIG_NOSILENTUPDATE
diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
index e39fcd8..bde5b95 100644
--- a/scripts/kconfig/conf.c
+++ b/scripts/kconfig/conf.c
@@ -13,6 +13,7 @@
#include <getopt.h>
#include <sys/stat.h>
#include <sys/time.h>
+#include <errno.h>

#include "lkc.h"

@@ -514,14 +515,23 @@ 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;
}
--
1.7.10.4