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SubjectRe: [PATCH] tcp: fix tcp_fastopen unaligned access complaints on sparc
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On 01/12/2017 01:13 PM, Eric Dumazet wrote:
> On Thu, 2017-01-12 at 11:59 -0800, Shannon Nelson wrote:
>> Fix up a data alignment issue on sparc by swapping the order
>> of the cookie byte array field with the length field in
>> struct tcp_fastopen_cookie
>>
>> This addresses log complaints like these:
>> log_unaligned: 113 callbacks suppressed
>> Kernel unaligned access at TPC[976490] tcp_try_fastopen+0x2d0/0x360
>> Kernel unaligned access at TPC[9764ac] tcp_try_fastopen+0x2ec/0x360
>> Kernel unaligned access at TPC[9764c8] tcp_try_fastopen+0x308/0x360
>> Kernel unaligned access at TPC[9764e4] tcp_try_fastopen+0x324/0x360
>> Kernel unaligned access at TPC[976490] tcp_try_fastopen+0x2d0/0x360
>>
>> Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
>> ---
>> include/linux/tcp.h | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
>> index fc5848d..95cda75 100644
>> --- a/include/linux/tcp.h
>> +++ b/include/linux/tcp.h
>> @@ -62,8 +62,8 @@ static inline unsigned int tcp_optlen(const struct sk_buff *skb)
>>
>> /* TCP Fast Open Cookie as stored in memory */
>> struct tcp_fastopen_cookie {
>> - s8 len;
>> u8 val[TCP_FASTOPEN_COOKIE_MAX];
>> + s8 len;
>> bool exp; /* In RFC6994 experimental option format */
>> };
>>
> Strange... Do you have an explanation of why this patch would be
> needed ? A compiler issue ?
>
>
> s8 and u8 are bytes after all.
>
>


I suspect that someplace, somebody is casting val to an int * or
something like that.

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