[LEDE-DEV] dropbear & gcc 7.1.0

[Kevin Darbyshire-Bryant]

On 29/05/17 16:54, e9hack wrote:
> Am 29.05.2017 um 10:13 schrieb Bastian Bittorf:
>> * Syrone Wong <wong.syrone at gmail.com> [29.05.2017 10:03]:
>>>> have you tried to '/etc/init.d/dropbear'?
>>>
>>> The problem is you cannot access the router, which means you cannot
>>> execute any commands.
>>
>> ok, maybe you can execute a command with LuCI?
>> (i'am not familiar with LuCI)
>> maybe you can try serial console.
>> maybe you can put that into /etc/rc.local
>>
>> i wanted to write: '/etc/init.d/dropbear restart', sorry for that.
>>
> 
> I did try it already with custom commands from LuCI. It doesn't help. Dropbear is still running but to connect isn't
> possible.

Had a really quick play with this and as I suspected it's related to 
compiler optimization flags.  In essence, if I compile with '-Os' then 
dropbear plays dumb, with my usual (but different from default) of '-O2' 
then dropbear, gcc 7 & mips get on fine, irrespective of target -march 
settings.

So as further totally wild guesses and on the basis 'ssh -vvv' shows 
things hanging during the initial ECDH key exchange, I'm going to guess 
this is happening somewhere in the libtommath/crypt libraries.

Kevin