fdisk: better fallback for get_random_id()

When /dev/urandom is not available, we have to use some kind of a hack
to generate a random MBR identifier.  Use a better fallback that
incorporates the clock down to microsecond granularity.

Signed-off-by: H. Peter Anvin" <hpa@zytor.com>

diff --git a/fdisk/fdisk.c b/fdisk/fdisk.c
index cc71c5c4928a0095ed5694628f4c585fcfc06702..ede41b3e60dea4bf90fe10552fc4ce1c378fbcf0 100644 (file)
--- a/fdisk/fdisk.c
+++ b/fdisk/fdisk.c
@@ -18,6 +18,7 @@
 #include <errno.h>
 #include <getopt.h>
 #include <sys/stat.h>
+#include <sys/time.h>
 #include <time.h>
 
 #include "nls.h"
@@ -148,6 +149,7 @@ get_random_id(void) {
        int fd;
        unsigned int v;
        ssize_t rv = -1;
+       struct timeval tv;
 
        fd = open("/dev/urandom", O_RDONLY);
        if (fd >= 0) {
@@ -159,7 +161,8 @@ get_random_id(void) {
                return v;
 
        /* Fallback: sucks, but better than nothing */
-       return (unsigned int)(getpid() + time(NULL));
+       gettimeofday(&tv, NULL);
+       return (unsigned int)(tv.tv_sec + (tv.tv_usec << 12) + getpid());
 }
 
 /* normally O_RDWR, -l option gives O_RDONLY */