llc: Constify struct llc_sap_state_trans

'struct llc_sap_state_trans' are not modified in this driver.

Constifying this structure moves some data to a read-only section, so
increase overall security.

On a x86_64, with allmodconfig, as an example:
Before:
======
text data bss dec hex filename
339 456 24 819 333 net/llc/llc_s_st.o

After:
=====
text data bss dec hex filename
683 144 0 827 33b net/llc/llc_s_st.o

Signed-off-by: Christophe JAILLET <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Link: https://patch.msgid.link/9d17587639[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/llc_s_st.h

···
 };
 
 struct llc_sap_state {
-	u8			   curr_state;
-	struct llc_sap_state_trans **transitions;
+	u8				 curr_state;
+	const struct llc_sap_state_trans **transitions;
 };
 
 /* only access to SAP state table */

net/llc/llc_s_st.c

···
  * last entry for this state
  * all members are zeros, .bss zeroes it
  */
-static struct llc_sap_state_trans llc_sap_state_trans_end;
+static const struct llc_sap_state_trans llc_sap_state_trans_end;
 
 /* state LLC_SAP_STATE_INACTIVE transition for
  * LLC_SAP_EV_ACTIVATION_REQ event
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_inactive_state_trans_1 = {
+static const struct llc_sap_state_trans llc_sap_inactive_state_trans_1 = {
 	.ev =		llc_sap_ev_activation_req,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_inactive_state_actions_1,
 };
 
 /* array of pointers; one to each transition */
-static struct llc_sap_state_trans *llc_sap_inactive_state_transitions[] = {
+static const struct llc_sap_state_trans *llc_sap_inactive_state_transitions[] = {
 	[0] = &llc_sap_inactive_state_trans_1,
 	[1] = &llc_sap_state_trans_end,
 };
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_1 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_1 = {
 	.ev =		llc_sap_ev_rx_ui,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_1,
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_2 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_2 = {
 	.ev =		llc_sap_ev_unitdata_req,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_2,
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_3 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_3 = {
 	.ev =		llc_sap_ev_xid_req,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_3,
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_4 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_4 = {
 	.ev =		llc_sap_ev_rx_xid_c,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_4,
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_5 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_5 = {
 	.ev =		llc_sap_ev_rx_xid_r,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_5,
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_6 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_6 = {
 	.ev =		llc_sap_ev_test_req,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_6,
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_7 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_7 = {
 	.ev =		llc_sap_ev_rx_test_c,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_7
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_8 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_8 = {
 	.ev =		llc_sap_ev_rx_test_r,
 	.next_state =	LLC_SAP_STATE_ACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_8,
···
 	[1] = NULL,
 };
 
-static struct llc_sap_state_trans llc_sap_active_state_trans_9 = {
+static const struct llc_sap_state_trans llc_sap_active_state_trans_9 = {
 	.ev =		llc_sap_ev_deactivation_req,
 	.next_state =	LLC_SAP_STATE_INACTIVE,
 	.ev_actions =	llc_sap_active_state_actions_9
 };
 
 /* array of pointers; one to each transition */
-static struct llc_sap_state_trans *llc_sap_active_state_transitions[] = {
+static const struct llc_sap_state_trans *llc_sap_active_state_transitions[] = {
 	[0] = &llc_sap_active_state_trans_2,
 	[1] = &llc_sap_active_state_trans_1,
 	[2] = &llc_sap_active_state_trans_3,

net/llc/llc_sap.c

···
  *	Returns the pointer to found transition on success or %NULL for
  *	failure.
  */
-static struct llc_sap_state_trans *llc_find_sap_trans(struct llc_sap *sap,
-						      struct sk_buff *skb)
+static const struct llc_sap_state_trans *llc_find_sap_trans(struct llc_sap *sap,
+							    struct sk_buff *skb)
 {
 	int i = 0;
-	struct llc_sap_state_trans *rc = NULL;
-	struct llc_sap_state_trans **next_trans;
+	const struct llc_sap_state_trans *rc = NULL;
+	const struct llc_sap_state_trans **next_trans;
 	struct llc_sap_state *curr_state = &llc_sap_state_table[sap->state - 1];
 	/*
 	 * Search thru events for this state until list exhausted or until
···
  *	Returns 0 for success and 1 for failure of at least one action.
  */
 static int llc_exec_sap_trans_actions(struct llc_sap *sap,
-				      struct llc_sap_state_trans *trans,
+				      const struct llc_sap_state_trans *trans,
 				      struct sk_buff *skb)
 {
 	int rc = 0;
···
  */
 static int llc_sap_next_state(struct llc_sap *sap, struct sk_buff *skb)
 {
+	const struct llc_sap_state_trans *trans;
 	int rc = 1;
-	struct llc_sap_state_trans *trans;
 
 	if (sap->state > LLC_NR_SAP_STATES)
 		goto out;