selinux: print sum of chain lengths^2 for hash tables

Print the sum of chain lengths squared as a metric for hash tables to
provide more insights, similar to avtabs.

While on it add a comma in the avtab message to improve readability of
the output.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Reviewed-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: cgzones

security/selinux/ss/avtab.c

@@ -349,7 +349,7 @@ void avtab_hash_eval(struct avtab *h, const char *tag)
 	}
 
 	pr_debug("SELinux: %s:  %d entries and %d/%d buckets used, "
-	       "longest chain length %d sum of chain length^2 %llu\n",
+	       "longest chain length %d, sum of chain length^2 %llu\n",
 	       tag, h->nel, slots_used, h->nslot, max_chain_len,
 	       chain2_len_sum);
 }

security/selinux/ss/hashtab.c

@@ -107,10 +107,12 @@ int hashtab_map(struct hashtab *h,
 void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
 {
 	u32 i, chain_len, slots_used, max_chain_len;
+	u64 chain2_len_sum;
 	struct hashtab_node *cur;
 
 	slots_used = 0;
 	max_chain_len = 0;
+	chain2_len_sum = 0;
 	for (i = 0; i < h->size; i++) {
 		cur = h->htable[i];
 		if (cur) {
@@ -123,11 +125,14 @@ void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
 
 			if (chain_len > max_chain_len)
 				max_chain_len = chain_len;
+
+			chain2_len_sum += (u64)chain_len * chain_len;
 		}
 	}
 
 	info->slots_used = slots_used;
 	info->max_chain_len = max_chain_len;
+	info->chain2_len_sum = chain2_len_sum;
 }
 #endif /* CONFIG_SECURITY_SELINUX_DEBUG */
 

security/selinux/ss/hashtab.h

@@ -38,6 +38,7 @@ struct hashtab {
 struct hashtab_info {
 	u32 slots_used;
 	u32 max_chain_len;
+	u64 chain2_len_sum;
 };
 
 /*

security/selinux/ss/policydb.c

@@ -684,9 +684,9 @@ static void hash_eval(struct hashtab *h, const char *hash_name)
 	struct hashtab_info info;
 
 	hashtab_stat(h, &info);
-	pr_debug("SELinux: %s:  %d entries and %d/%d buckets used, longest chain length %d\n",
+	pr_debug("SELinux: %s:  %d entries and %d/%d buckets used, longest chain length %d, sum of chain length^2 %llu\n",
 		 hash_name, h->nel, info.slots_used, h->size,
-		 info.max_chain_len);
+		 info.max_chain_len, info.chain2_len_sum);
 }
 
 static void symtab_hash_eval(struct symtab *s)