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 <christophe.jaillet@wanadoo.fr>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/9d17587639195ee94b74ff06a11ef97d1833ee52.1720973710.git.christophe.jaillet@wanadoo.frSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/llc_s_st.h

@@ -30,7 +30,7 @@ struct llc_sap_state_trans {
 
 struct llc_sap_state {
 	u8				 curr_state;
-	struct llc_sap_state_trans **transitions;
+	const struct llc_sap_state_trans **transitions;
 };
 
 /* only access to SAP state table */

net/llc/llc_s_st.c

@@ -24,7 +24,7 @@
  * 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
@@ -34,14 +34,14 @@ static const llc_sap_action_t llc_sap_inactive_state_actions_1[] = {
 	[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,
 };
@@ -52,7 +52,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_1[] = {
 	[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,
@@ -64,7 +64,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_2[] = {
 	[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,
@@ -76,7 +76,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_3[] = {
 	[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,
@@ -88,7 +88,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_4[] = {
 	[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,
@@ -100,7 +100,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_5[] = {
 	[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,
@@ -112,7 +112,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_6[] = {
 	[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,
@@ -124,7 +124,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_7[] = {
 	[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
@@ -136,7 +136,7 @@ static const llc_sap_action_t llc_sap_active_state_actions_8[] = {
 	[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,
@@ -150,14 +150,14 @@ static const llc_sap_action_t llc_sap_active_state_actions_9[] = {
 	[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

@@ -114,12 +114,12 @@ void llc_sap_rtn_pdu(struct llc_sap *sap, struct sk_buff *skb)
  *	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,
+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
@@ -143,7 +143,7 @@ static struct llc_sap_state_trans *llc_find_sap_trans(struct llc_sap *sap,
  *	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;
@@ -166,8 +166,8 @@ static int llc_exec_sap_trans_actions(struct llc_sap *sap,
  */
 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;