LSM: Convert from initcall to struct lsm_info

In preparation for doing more interesting LSM init probing, this converts
the existing initcall system into an explicit call into a function pointer
from a section-collected struct lsm_info array.
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: James Morris <james.morris@microsoft.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

include/linux/init.h

@@ -133,7 +133,6 @@ static inline initcall_t initcall_from_entry(initcall_entry_t *entry)
 #endif
 
 extern initcall_entry_t __con_initcall_start[], __con_initcall_end[];
-extern initcall_entry_t __start_lsm_info[], __end_lsm_info[];
 
 /* Used for contructor calls. */
 typedef void (*ctor_fn_t)(void);
@@ -236,7 +235,6 @@ extern bool initcall_debug;
 	static exitcall_t __exitcall_##fn __exit_call = fn
 
 #define console_initcall(fn)	___define_initcall(fn,, .con_initcall)
-#define security_initcall(fn)	___define_initcall(fn,, .lsm_info)
 
 struct obs_kernel_param {
 	const char *str;

include/linux/lsm_hooks.h

@@ -2039,6 +2039,18 @@ extern char *lsm_names;
 extern void security_add_hooks(struct security_hook_list *hooks, int count,
 				char *lsm);
 
+struct lsm_info {
+	int (*init)(void);	/* Required. */
+};
+
+extern struct lsm_info __start_lsm_info[], __end_lsm_info[];
+
+#define security_initcall(lsm)						\
+	static struct lsm_info __lsm_##lsm				\
+		__used __section(.lsm_info.init)			\
+		__aligned(sizeof(unsigned long))			\
+		= { .init = lsm, }
+
 #ifdef CONFIG_SECURITY_SELINUX_DISABLE
 /*
  * Assuring the safety of deleting a security module is up to

include/linux/module.h

@@ -123,7 +123,6 @@ extern void cleanup_module(void);
 #define late_initcall_sync(fn)		module_init(fn)
 
 #define console_initcall(fn)		module_init(fn)
-#define security_initcall(fn)		module_init(fn)
 
 /* Each module must use one module_init(). */
 #define module_init(initfn)					\

security/integrity/iint.c

@@ -22,6 +22,7 @@
 #include <linux/file.h>
 #include <linux/uaccess.h>
 #include <linux/security.h>
+#include <linux/lsm_hooks.h>
 #include "integrity.h"
 
 static struct rb_root integrity_iint_tree = RB_ROOT;

security/security.c

@@ -43,16 +43,12 @@ char *lsm_names;
 static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
 	CONFIG_DEFAULT_SECURITY;
 
-static void __init do_security_initcalls(void)
+static void __init major_lsm_init(void)
 {
-	initcall_t call;
-	initcall_entry_t *ce;
+	struct lsm_info *lsm;
 
-	ce = __start_lsm_info;
-	while (ce < __end_lsm_info) {
-		call = initcall_from_entry(ce);
-		call();
-		ce++;
+	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+		lsm->init();
 	}
 }
 
@@ -82,7 +78,7 @@ int __init security_init(void)
 	/*
 	 * Load all the remaining security modules.
 	 */
-	do_security_initcalls();
+	major_lsm_init();
 
 	return 0;
 }