net: macb: Add __nonstring annotations for unterminated strings

When a character array without a terminating NUL character has a static initializer, GCC 15's -Wunterminated-string-initialization will only warn if the array lacks the "nonstring" attribute[1]. Mark the arrays with __nonstring to correctly identify the char array as "not a C string" and thereby eliminate the warning:

In file included from ../drivers/net/ethernet/cadence/macb_main.c:42:
../drivers/net/ethernet/cadence/macb.h:1070:35: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (33 chars into 32 available) [-Wunterminated-string-initialization]
1070 | GEM_STAT_TITLE(TX1519CNT, "tx_greater_than_1518_byte_frames"),

      |                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

../drivers/net/ethernet/cadence/macb.h:1050:24: note: in definition of macro 'GEM_STAT_TITLE_BITS'
1050 | .stat_string = title, \
| ^~~~~
../drivers/net/ethernet/cadence/macb.h:1070:9: note: in expansion of macro 'GEM_STAT_TITLE'

 1070 |         GEM_STAT_TITLE(TX1519CNT, "tx_greater_than_1518_byte_frames"),
      |         ^~~~~~~~~~~~~~
../drivers/net/ethernet/cadence/macb.h:1097:35: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (33 chars into 32 available) [-Wunterminated-string-initialization]
 1097 |         GEM_STAT_TITLE(RX1519CNT, "rx_greater_than_1518_byte_frames"),
      |                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

../drivers/net/ethernet/cadence/macb.h:1050:24: note: in definition of macro 'GEM_STAT_TITLE_BITS'
1050 | .stat_string = title, \
| ^~~~~
../drivers/net/ethernet/cadence/macb.h:1097:9: note: in expansion of macro 'GEM_STAT_TITLE'

 1097 |         GEM_STAT_TITLE(RX1519CNT, "rx_greater_than_1518_byte_frames"),
      |         ^~~~~~~~~~~~~~

Since these strings are copied with memcpy() they do not need to be NUL terminated, and can use __nonstring:

                        memcpy(p, gem_statistics[i].stat_string,
                               ETH_GSTRING_LEN);

Link https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]

Signed-off-by Kees Cook <[email protected]>

---

v3: improve commit message (Bill), drop whitespace change (Bill)
v2: https://lore.kernel.org/lkml/[email protected]/
v1: https://lore.kernel.org/lkml/[email protected]/
Cc: Nicolas Ferre <[email protected]>
Cc: Claudiu Beznea <[email protected]>
Cc: Andrew Lunn <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: [email protected]

---
 drivers/net/ethernet/cadence/macb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/net/ethernet/cadence/macb.h +1 -1

index 2847278d9cd4..d2a4c180d6a6 100644
@@ -1027,7 +1027,7 @@ struct gem_stats {
  * this register should contribute to.
  */
 struct gem_statistic {
-	char stat_string[ETH_GSTRING_LEN];
+	char stat_string[ETH_GSTRING_LEN] __nonstring;
 	int offset;
 	u32 stat_bits;
 };

drivers/net/ethernet/cadence/macb.h struct gem_stats { · line 1030

Quoted 3 lines

struct gem_statistic {

drivers/net/ethernet/cadence/macb.h +1 -1

-	char stat_string[ETH_GSTRING_LEN];
+	char stat_string[ETH_GSTRING_LEN] __nonstring;

This general pattern of a char foo[ETH_GSTRING_LEN]' will appear throughout drivers/net/ethernet. Maybe Coccinelle can find them all and add the __nonstring ?