Re: [PATCH v3] hash: add XOR32 hash function

[Medvedkin, Vladimir]

Hi Bill,

On 15/02/2023 11:06, Bili Dong wrote:
An XOR32 hash is needed in the Software Switch (SWX) Pipeline for its
use case in P4. We implement it in this patch so it could be easily
registered in the pipeline later.
Signed-off-by: Bili Dong <qobili...@gmail.com>
---
+static inline uint32_t
+rte_hash_xor(const void *data, uint32_t data_len, uint32_t init_val)
+{
+       uint32_t i;
+       uintptr_t pd = (uintptr_t) data;
+       init_val = rte_cpu_to_be_32(init_val);
+
+       for (i = 0; i < data_len / 4; i++) {
+               init_val ^= *(const uint32_t *)pd;
+               pd += 4;
+       }
+
+       if (data_len & 0x2) {
+               init_val ^= *(const uint32_t *)pd & LEFT16b_MASK;

Here you are reading 2 bytes after the data buffer, which can sometimes 
lead to segfault. I think it would be better just to:

init_val ^= *(const uint16_t *)pd << 16;

The same with the section bellow

+               pd += 2;
+       }
+
+       if (data_len & 0x1)
+               init_val ^= *(const uint32_t *)pd & LEFT8b_MASK;
+
+       init_val = rte_be_to_cpu_32(init_val);
+       return init_val;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_HASH_XOR_H_ */

--
Regards,
Vladimir