[PATCH v2 2/5] security: Count the LSMs enabled at compile time

[KP Singh <kpsingh@kernel.org>]

These macros are a clever trick to determine a count of the number of
LSMs that are enabled in the config to ascertain the maximum number of
static calls that need to be configured per LSM hook.

Without this one would need to generate static calls for (number of
possible LSMs * number of LSM hooks) which ends up being quite wasteful
especially when some LSMs are not compiled into the kernel.

Suggested-by: Kui-Feng Lee <sinquersw@gmail.com>
Signed-off-by: KP Singh <kpsingh@kernel.org>
---
 include/linux/lsm_count.h | 131 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 include/linux/lsm_count.h

diff --git a/include/linux/lsm_count.h b/include/linux/lsm_count.h
new file mode 100644
index 000000000000..818f62ffa723
--- /dev/null
+++ b/include/linux/lsm_count.h
@@ -0,0 +1,131 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (C) 2023 Google LLC.
+ */
+
+#ifndef __LINUX_LSM_COUNT_H
+#define __LINUX_LSM_COUNT_H
+
+#include <linux/kconfig.h>
+
+/*
+ * Macros to count the number of LSMs enabled in the kernel at compile time.
+ */
+
+#define __LSM_COUNT_15(x, y...) 15
+#define __LSM_COUNT_14(x, y...) 14
+#define __LSM_COUNT_13(x, y...) 13
+#define __LSM_COUNT_12(x, y...) 12
+#define __LSM_COUNT_11(x, y...) 11
+#define __LSM_COUNT_10(x, y...) 10
+#define __LSM_COUNT_9(x, y...) 9
+#define __LSM_COUNT_8(x, y...) 8
+#define __LSM_COUNT_7(x, y...) 7
+#define __LSM_COUNT_6(x, y...) 6
+#define __LSM_COUNT_5(x, y...) 5
+#define __LSM_COUNT_4(x, y...) 4
+#define __LSM_COUNT_3(x, y...) 3
+#define __LSM_COUNT_2(x, y...) 2
+#define __LSM_COUNT_1(x, y...) 1
+#define __LSM_COUNT_0(x, y...) 0
+
+#define __LSM_COUNT1_15(x, y...) __LSM_COUNT ## x ## _15(y)
+#define __LSM_COUNT1_14(x, y...) __LSM_COUNT ## x ## _14(y)
+#define __LSM_COUNT1_13(x, y...) __LSM_COUNT ## x ## _13(y)
+#define __LSM_COUNT1_12(x, y...) __LSM_COUNT ## x ## _12(y)
+#define __LSM_COUNT1_10(x, y...) __LSM_COUNT ## x ## _11(y)
+#define __LSM_COUNT1_9(x, y...) __LSM_COUNT ## x ## _10(y)
+#define __LSM_COUNT1_8(x, y...) __LSM_COUNT ## x ## _9(y)
+#define __LSM_COUNT1_7(x, y...) __LSM_COUNT ## x ## _8(y)
+#define __LSM_COUNT1_6(x, y...) __LSM_COUNT ## x ## _7(y)
+#define __LSM_COUNT1_5(x, y...) __LSM_COUNT ## x ## _6(y)
+#define __LSM_COUNT1_4(x, y...) __LSM_COUNT ## x ## _5(y)
+#define __LSM_COUNT1_3(x, y...) __LSM_COUNT ## x ## _4(y)
+#define __LSM_COUNT1_2(x, y...) __LSM_COUNT ## x ## _3(y)
+#define __LSM_COUNT1_1(x, y...) __LSM_COUNT ## x ## _2(y)
+#define __LSM_COUNT1_0(x, y...) __LSM_COUNT ## x ## _1(y)
+#define __LSM_COUNT(x, y...) __LSM_COUNT ## x ## _0(y)
+
+#define __LSM_COUNT_EXPAND(x...) __LSM_COUNT(x)
+
+#if IS_ENABLED(CONFIG_SECURITY)
+#define CAPABILITIES_ENABLED 1,
+#else
+#define CAPABILITIES_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_SELINUX)
+#define SELINUX_ENABLED 1,
+#else
+#define SELINUX_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_SMACK)
+#define SMACK_ENABLED 1,
+#else
+#define SMACK_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_APPARMOR)
+#define APPARMOR_ENABLED 1,
+#else
+#define APPARMOR_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_TOMOYO)
+#define TOMOYO_ENABLED 1,
+#else
+#define TOMOYO_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_YAMA)
+#define YAMA_ENABLED 1,
+#else
+#define YAMA_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_LOADPIN)
+#define LOADPIN_ENABLED 1,
+#else
+#define LOADPIN_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_LOCKDOWN_LSM)
+#define LOCKDOWN_ENABLED 1,
+#else
+#define LOCKDOWN_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_BPF_LSM)
+#define BPF_LSM_ENABLED 1,
+#else
+#define BPF_LSM_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_BPF_LSM)
+#define BPF_LSM_ENABLED 1,
+#else
+#define BPF_LSM_ENABLED
+#endif
+
+#if IS_ENABLED(CONFIG_SECURITY_LANDLOCK)
+#define LANDLOCK_ENABLED 1,
+#else
+#define LANDLOCK_ENABLED
+#endif
+
+#define MAX_LSM_COUNT			\
+	__LSM_COUNT_EXPAND(		\
+		CAPABILITIES_ENABLED	\
+		SELINUX_ENABLED		\
+		SMACK_ENABLED		\
+		APPARMOR_ENABLED	\
+		TOMOYO_ENABLED		\
+		YAMA_ENABLED		\
+		LOADPIN_ENABLED		\
+		LOCKDOWN_ENABLED	\
+		BPF_LSM_ENABLED		\
+		LANDLOCK_ENABLED)
+
+#endif  /* __LINUX_LSM_COUNT_H */
-- 
2.41.0.162.gfafddb0af9-goog