On 3/12/2025 1:07 PM, Kees Cook wrote:
> 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]>
> ---
Reviewed-by: Jacob Keller <[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(-)
>
> diff --git a/drivers/net/ethernet/cadence/macb.h
> b/drivers/net/ethernet/cadence/macb.h
> index 2847278d9cd4..d2a4c180d6a6 100644
> --- a/drivers/net/ethernet/cadence/macb.h
> +++ b/drivers/net/ethernet/cadence/macb.h
> @@ -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;
> };
