falcon randint # make clean && cp /usr/src/linux/drivers/char/random.o . && cp /usr/src/linux/lib/sha1.o . && make && insmod ./randtest.ko && rmmod randtest
rm -f Module.symvers *.o *~ .\#* .*.cmd *.mod.c *.ko
rm -rf .tmp_versions
make -C /lib/modules/2.6.21.5/build/ SUBDIRS=/root/randint modules
make[1]: Entering directory `/usr/src/linux-2.6.21.5'
  CC [M]  /root/randint/randint.o
  LD [M]  /root/randint/randtest.o
  Building modules, stage 2.
  MODPOST 1 modules
WARNING: /root/randint/randtest: 'sha_transform' exported twice. Previous export was in vmlinux
WARNING: /root/randint/randtest: 'add_input_randomness' exported twice. Previous export was in vmlinux
WARNING: /root/randint/randtest: 'add_disk_randomness' exported twice. Previous export was in vmlinux
WARNING: /root/randint/randtest: 'get_random_bytes' exported twice. Previous export was in vmlinux
WARNING: /root/randint/randtest: 'generate_random_uuid' exported twice. Previous export was in vmlinux
WARNING: /root/randint/randtest: 'secure_tcpv6_sequence_number' exported twice. Previous export was in vmlinux
WARNING: /root/randint/randtest: 'secure_tcp_sequence_number' exported twice. Previous export was in vmlinux
  CC      /root/randint/randtest.mod.o
  LD [M]  /root/randint/randtest.ko
make[1]: Leaving directory `/usr/src/linux-2.6.21.5'
insmod: error inserting './randtest.ko': -1 Invalid module format


falcon randint # cat Kbuild 
obj-m := randtest.o
randtest-objs := sha1.o random.o randint.o

falcon randint # cat Makefile 

default:

        make -C /lib/modules/$(shell uname -r)/build/ SUBDIRS=$(PWD) modules

clean:

        rm -f Module.symvers *.o *~ .\#* .*.cmd *.mod.c *.ko
        rm -rf .tmp_versions


falcon randint # cat randint.c 
/*-
  solar,pappy@gentoo.org
  Tue Jun 19 00:39:29
*/

#include <linux/init.h>  
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/random.h>


static int randint_init(void) {
  unsigned int seed[2];
  seed[0] = 0x0; // get_random_int();
  seed[1] = 0x0; // get_random_int();

  if (seed[0] == seed[1]) {
    printk(KERN_ALERT "Possible Security Problem: Fast repeated calls to the function get_random_int() is not cryptographically safe: 0x%0*x=0x%0*x\n"
,
      sizeof(long), seed[0], sizeof(long), seed[1]);
    return 1;
  } else {
    printk(KERN_INFO "Checking randomization: Fast repeated calls to the function get_random_int(): 0x%0*x=0x%0*x\n",
      sizeof(long), seed[0], sizeof(long), seed[1]);
    return 0;
  }
}

static void randint_exit(void) {
  return;
}

module_init(randint_init);
module_exit(randint_exit);

MODULE_LICENSE("GPL");