linux-kernel - [PATCH 1/6] selinux: print sum of chain lengths^2 for hash tables

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Date:   Fri, 18 Aug 2023 17:12:18 +0200
From:   Christian Göttsche <cgzones@...glemail.com>
To:     selinux@...r.kernel.org
Cc:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/6] 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@...glemail.com>
---
 security/selinux/ss/avtab.c    | 2 +-
 security/selinux/ss/hashtab.c  | 5 +++++
 security/selinux/ss/hashtab.h  | 1 +
 security/selinux/ss/policydb.c | 4 ++--
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index 86d98a8e291b..955cfe495606 100644
--- a/security/selinux/ss/avtab.c
+++ b/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);
 }
diff --git a/security/selinux/ss/hashtab.c b/security/selinux/ss/hashtab.c
index ac5cdddfbf78..c05d8346a94a 100644
--- a/security/selinux/ss/hashtab.c
+++ b/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 */
 
diff --git a/security/selinux/ss/hashtab.h b/security/selinux/ss/hashtab.h
index f9713b56d3d0..09b0a3744937 100644
--- a/security/selinux/ss/hashtab.h
+++ b/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;
 };
 
 /*
diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 28bd75dc6f71..84f02d4f8093 100644
--- a/security/selinux/ss/policydb.c
+++ b/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)
-- 
2.40.1