Hi Pawel,
Oops, thanks for the clue. I have a buffer over-read here leading to undefined
behaviour.
The only solution I see here is to declare uint32_t pointer and evaluate it to
(uint8_t *) data + data_len - (data_len & 0x07). Ideas are welcome. That would
resolve strict-aliasing violation.
_____________________
From: Pawel Wodkowski [pawelx.wodkow...@intel.com]
Sent: Friday, March 20, 2015 18:47
To: ????????? ????? ????????????; dev at dpdk.org
Subject: Re: [dpdk-dev] [PATCH] hash: fix breaking strict-aliasing rules
On 2015-03-18 17:51, Yerden Zhumabekov wrote:
>
> - switch (7 - (data_len & 0x07)) {
> + i = 7 - (data_len & 0x07);
> + switch (i) {
> case 0:
> - temp |= (uint64_t) *((const uint8_t *)p64 + 6) << 48;
> - /* Fallthrough */
> case 1:
> - temp |= (uint64_t) *((const uint8_t *)p64 + 5) << 40;
> - /* Fallthrough */
> case 2:
> - temp |= (uint64_t) *((const uint8_t *)p64 + 4) << 32;
> - temp |= *((const uint32_t *)p64);
> + temp = odd_8byte_mask[i] & *p64;
> init_val = rte_hash_crc_8byte(temp, init_val);
> break;
> case 3:
> - init_val = rte_hash_crc_4byte(*(const uint32_t *)p64, init_val);
> - break;
> case 4:
> - temp |= *((const uint8_t *)p64 + 2) << 16;
> - /* Fallthrough */
> case 5:
> - temp |= *((const uint8_t *)p64 + 1) << 8;
> - /* Fallthrough */
> case 6:
> - temp |= *((const uint8_t *)p64);
> + temp = odd_8byte_mask[i] & *p64;
> init_val = rte_hash_crc_4byte(temp, init_val);
> - /* Fallthrough */
> default:
> break;
> }
>
Second thought: is this not an issue here reading 8 bytes by
dereferencing *p64 if there is less bytes in buffer?
--
Pawel
