[RFC PATCH 06/10] landlock/domain: Define landlock_domain

[Tingmao Wang]

This will eventually take the role of landlock_ruleset (and maybe
landlock_hirearchy?), but for now it is just the inode rules hashtable.

Signed-off-by: Tingmao Wang <m at maowtm.org>
---
 security/landlock/domain.c | 36 ++++++++++++++++++++++++++++++++++++
 security/landlock/domain.h | 27 +++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/security/landlock/domain.c b/security/landlock/domain.c
index a647b68e8d06..180ed75da9e2 100644
--- a/security/landlock/domain.c
+++ b/security/landlock/domain.c
@@ -5,6 +5,7 @@
  * Copyright © 2016-2020 Mickaël Salaün <mic at digikod.net>
  * Copyright © 2018-2020 ANSSI
  * Copyright © 2024-2025 Microsoft Corporation
+ * Copyright © 2025      Tingmao Wang <m at maowtm.org>
  */
 
 #include <kunit/test.h>
@@ -24,6 +25,41 @@
 #include "domain.h"
 #include "id.h"
 
+struct landlock_domain *landlock_alloc_domain(size_t num_inode_entries,
+					      u16 num_layers)
+{
+	struct landlock_domain *new_domain =
+		kzalloc(sizeof(struct landlock_domain), GFP_KERNEL_ACCOUNT);
+
+	if (!new_domain)
+		return NULL;
+	refcount_set(&new_domain->usage, 1);
+	new_domain->num_layers = num_layers;
+	if (landlock_hash_init(num_inode_entries, &new_domain->inode_table)) {
+		kfree(new_domain);
+		return NULL;
+	}
+
+	return new_domain;
+}
+
+static void free_domain(struct landlock_domain *const domain)
+{
+	might_sleep();
+
+	landlock_hash_free(&domain->inode_table, LANDLOCK_KEY_INODE);
+	kfree(domain);
+}
+
+void landlock_put_domain(struct landlock_domain *const domain)
+{
+	might_sleep();
+
+	if (domain && refcount_dec_and_test(&domain->usage)) {
+		free_domain(domain);
+	}
+}
+
 #ifdef CONFIG_AUDIT
 
 /**
diff --git a/security/landlock/domain.h b/security/landlock/domain.h
index 7fb70b25f85a..ed685f8ad52e 100644
--- a/security/landlock/domain.h
+++ b/security/landlock/domain.h
@@ -5,6 +5,7 @@
  * Copyright © 2016-2020 Mickaël Salaün <mic at digikod.net>
  * Copyright © 2018-2020 ANSSI
  * Copyright © 2024-2025 Microsoft Corporation
+ * Copyright © 2025      Tingmao Wang <m at maowtm.org>
  */
 
 #ifndef _SECURITY_LANDLOCK_DOMAIN_H
@@ -20,6 +21,32 @@
 
 #include "access.h"
 #include "audit.h"
+#include "hash.h"
+
+struct landlock_domain {
+	struct landlock_hashtable inode_table;
+
+	/**
+	 * @usage: Reference count for this struct.
+	 */
+	refcount_t usage;
+
+	/**
+	 * @num_layers: Number of layers in this domain.
+	 */
+	u16 num_layers;
+};
+
+struct landlock_domain *landlock_alloc_domain(size_t num_inode_entries,
+					      u16 num_layers);
+
+static inline void landlock_get_domain(struct landlock_domain *const domain)
+{
+	if (domain)
+		refcount_inc(&domain->usage);
+}
+
+void landlock_put_domain(struct landlock_domain *const domain);
 
 enum landlock_log_status {
 	LANDLOCK_LOG_PENDING = 0,
-- 
2.49.0