s390/kaslr: avoid mixing valid random value and an error code

0 is a valid random value. To avoid mixing it with error code 0 as an
return code make get_random() take extra argument to output random
value and return an error code.

Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Reviewed-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/boot/kaslr.c b/arch/s390/boot/kaslr.c
index d444216..c8549a0 100644 (file)
--- a/arch/s390/boot/kaslr.c
+++ b/arch/s390/boot/kaslr.c
@@ -42,7 +42,7 @@ static int check_prng(void)
                return PRNG_MODE_TDES;
 }
 
-static unsigned long get_random(unsigned long limit)
+static int get_random(unsigned long limit, unsigned long *value)
 {
        struct prng_parm prng = {
                /* initial parameter block for tdes mode, copied from libica */
@@ -84,9 +84,10 @@ static unsigned long get_random(unsigned long limit)
                          (u8 *) &random, sizeof(random));
                break;
        default:
-               random = 0;
+               return -1;
        }
-       return random % limit;
+       *value = random % limit;
+       return 0;
 }
 
 unsigned long get_random_base(unsigned long safe_addr)
@@ -143,8 +144,7 @@ unsigned long get_random_base(unsigned long safe_addr)
                return 0;
        }
 
-       base = get_random(block_sum);
-       if (base == 0)
+       if (get_random(block_sum, &base))
                return 0;
        if (base < safe_addr)
                base = safe_addr;