lkml.org 
[lkml]   [2018]   [Feb]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] tcp_lp: use 64-bit arithmetic instead of 32-bit
Hi Andrew,

Quoting Andrew Lunn <andrew@lunn.ch>:

> On Wed, Jan 31, 2018 at 07:07:49PM -0600, Gustavo A. R. Silva wrote:
>>
>> Hi Alan,
>>
>> Quoting Alan Cox <gnomes@lxorguk.ukuu.org.uk>:
>>
>> >On Wed, 31 Jan 2018 18:24:07 -0600
>> >"Gustavo A. R. Silva" <gustavo@embeddedor.com> wrote:
>> >
>> >>Cast to s64 some variables and a macro in order to give the
>> >>compiler complete information about the proper arithmetic to
>> >>use. Notice that these elements are used in contexts that
>> >>expect expressions of type s64 (64 bits, signed).
>> >>
>> >>Currently such expression are being evaluated using 32-bit
>> >>arithmetic.
>> >
>> >The question you need to ask is 'can it overflow 32bit maths', otherwise
>> >you are potentially making the system do extra work for no reason.
>> >
>>
>> Yeah, I get your point and it seems that in this particular case there is no
>> risk of a 32bit overflow, but in general and IMHO as the code evolves, the
>> use of incorrect arithmetic may have security implications in the future, so
>> I advocate for code correctness in this case.
>
> Hi Gustavo
>
> Is this on the hotpath? How much overhead does it add to 32 bit
> architectures which don't have 64 bit arithmetic in hardware? There
> are a lot of embedded systems which are 32 bit.
>

I'm sorry, I don't have access to 32-bit hardware at the moment.

Thanks
--
Gustavo




\
 
 \ /
  Last update: 2018-02-02 03:37    [W:0.075 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site