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)					\