[PATCH net 1/2] mlxsw: spectrum_acl_bloom_filter: Expand chunk_key_offsets[chunk_index]

[WangYuli]

This is a workaround to mitigate a compiler anomaly.

During LLVM toolchain compilation of this driver on s390x architecture, an
unreasonable __write_overflow_field warning occurs.

Contextually, chunk_index is restricted to 0, 1 or 2. By expanding these
possibilities, the compile warning is suppressed.

Fix follow error with clang-19 when -Werror:
  In file included from drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c:5:
  In file included from ./include/linux/gfp.h:7:
  In file included from ./include/linux/mmzone.h:8:
  In file included from ./include/linux/spinlock.h:63:
  In file included from ./include/linux/lockdep.h:14:
  In file included from ./include/linux/smp.h:13:
  In file included from ./include/linux/cpumask.h:12:
  In file included from ./include/linux/bitmap.h:13:
  In file included from ./include/linux/string.h:392:
  ./include/linux/fortify-string.h:571:4: error: call to '__write_overflow_field' declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror,-Wattribute-warning]
    571 |                         __write_overflow_field(p_size_field, size);
        |                         ^
  1 error generated.

Co-developed-by: Zijian Chen <czj2441@xxxxxxx>
Signed-off-by: Zijian Chen <czj2441@xxxxxxx>
Co-developed-by: Wentao Guan <guanwentao@xxxxxxxxxxxxx>
Signed-off-by: Wentao Guan <guanwentao@xxxxxxxxxxxxx>
Signed-off-by: WangYuli <wangyuli@xxxxxxxxxxxxx>
---
 .../mlxsw/spectrum_acl_bloom_filter.c         | 39 ++++++++++++-------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c
index a54eedb69a3f..96105bab680b 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c
@@ -203,17 +203,6 @@ static const u8 mlxsw_sp4_acl_bf_crc6_tab[256] = {
 0x2f, 0x02, 0x18, 0x35, 0x2c, 0x01, 0x1b, 0x36,
 };
 
-/* Each chunk contains 4 key blocks. Chunk 2 uses key blocks 11-8,
- * and we need to populate it with 4 key blocks copied from the entry encoded
- * key. The original keys layout is same for Spectrum-{2,3,4}.
- * Since the encoded key contains a 2 bytes padding, key block 11 starts at
- * offset 2. block 7 that is used in chunk 1 starts at offset 20 as 4 key blocks
- * take 18 bytes. See 'MLXSW_SP2_AFK_BLOCK_LAYOUT' for more details.
- * This array defines key offsets for easy access when copying key blocks from
- * entry key to Bloom filter chunk.
- */
-static const u8 chunk_key_offsets[MLXSW_BLOOM_KEY_CHUNKS] = {2, 20, 38};
-
 static u16 mlxsw_sp2_acl_bf_crc16_byte(u16 crc, u8 c)
 {
 	return (crc << 8) ^ mlxsw_sp2_acl_bf_crc16_tab[(crc >> 8) ^ c];
@@ -237,6 +226,7 @@ __mlxsw_sp_acl_bf_key_encode(struct mlxsw_sp_acl_atcam_region *aregion,
 	struct mlxsw_afk_key_info *key_info = aregion->region->key_info;
 	u8 chunk_index, chunk_count, block_count;
 	char *chunk = output;
+	char *enc_key_src_ptr;
 	__be16 erp_region_id;
 
 	block_count = mlxsw_afk_key_info_blocks_count_get(key_info);
@@ -248,9 +238,30 @@ __mlxsw_sp_acl_bf_key_encode(struct mlxsw_sp_acl_atcam_region *aregion,
 		memset(chunk, 0, pad_bytes);
 		memcpy(chunk + pad_bytes, &erp_region_id,
 		       sizeof(erp_region_id));
-		memcpy(chunk + key_offset,
-		       &aentry->ht_key.enc_key[chunk_key_offsets[chunk_index]],
-		       chunk_key_len);
+/* Each chunk contains 4 key blocks. Chunk 2 uses key blocks 11-8,
+ * and we need to populate it with 4 key blocks copied from the entry encoded
+ * key. The original keys layout is same for Spectrum-{2,3,4}.
+ * Since the encoded key contains a 2 bytes padding, key block 11 starts at
+ * offset 2. block 7 that is used in chunk 1 starts at offset 20 as 4 key blocks
+ * take 18 bytes. See 'MLXSW_SP2_AFK_BLOCK_LAYOUT' for more details.
+ * This array defines key offsets for easy access when copying key blocks from
+ * entry key to Bloom filter chunk.
+ *
+ * Define the acceptable values for chunk_index to prevent LLVM from failing
+ * compilation in certain circumstances.
+ */
+		switch (chunk_index) {
+		case 0:
+			enc_key_src_ptr = &aentry->ht_key.enc_key[2];
+			break;
+		case 1:
+			enc_key_src_ptr = &aentry->ht_key.enc_key[20];
+			break;
+		case 2:
+			enc_key_src_ptr = &aentry->ht_key.enc_key[38];
+			break;
+		}
+		memcpy(chunk + key_offset, enc_key_src_ptr, chunk_key_len);
 		chunk += chunk_len;
 	}
 	*len = chunk_count * chunk_len;
-- 
2.47.2