[LEDE-DEV] [PATCH 2/2] toolchain: gcc: drop MIPS patch

[Syrone Wong]

Hi,

Based on my test, it works well even if you keep this mips patch,
upstream already update libtommath and libtomcrypt
to latest, and I can confirm the update to these two libs fixes
dropbear misbehavior on mips.

https://github.com/mkj/dropbear/commit/a79b61517bc7123250d0e2dc21dc18deccf0bb64
https://github.com/mkj/dropbear/commit/364fb6019c1931de3d181f21ea491ec112161577


Best Regards,
Syrone Wong


On Wed, Aug 23, 2017 at 4:50 PM, Kevin Darbyshire-Bryant
<kevin at darbyshire-bryant.me.uk> wrote:
>
>
> On 23/08/17 09:20, Felix Fietkau wrote:
>>
>> On 2017-08-22 12:01, Kevin Darbyshire-Bryant wrote:
>>>
>>> Drop 300-mips_Os_cpu_rtx_cost_model.patch for gcc 7.2
>>>
>>> This was causing mis-compilation of dropbear with the default '-Os' size
>>> optimization as reported in FS#814
>>>
>>> Tested on ar71xx, archer C7 v2.  For size comparison of my whole build:
>>>
>>> 12058628 O2-withoutpatch-dropbearworks.bin
>>> 12058628 O2-withpatch-dropbearworks.bin
>>> 11468804 Os-withoutpatch-dropbearworks.bin
>>> 11468804 Os-withpatch-dropbearfails.bin
>>>
>>> Signed-off-by: Kevin Darbyshire-Bryant <kevin at darbyshire-bryant.me.uk>
>>
>> I strongly suspect that this change is hiding the real bug instead of
>> fixing it. Please double-check that the mis-compilation also does not
>> happen with -O2 instead of -Os.
>
>
> Hi Felix,
>
> The symptom of dropbear not responding (it goes into a tight loop) *only*
> occurs for me with the patch installed and with '-Os'.  As documented in the
> FS report, starting with gcc 7.1, dropbear (and for some uhttpd) go AWOL
> when built with '-Os'.  Initially I did not experience that issue because I
> always build with '-O2', however by switching to '-Os' I was able to
> reproduce the behaviour.
>
> As part of my bump to gcc 7.2 and 'cargo culting/refreshing' the 7.1 patches
> across, I thought I would investigate if the same erroneous behaviour
> existed - it did.  So questions:  Why MIPS only, why only with '-Os' and not
> '-O2', why is no one else screaming about this?  Many experiments and 'make
> dirclean' (to ensure gcc and the whole router image rebuilt) later I reached
> my conclusions with 300-mips_Os_cpu_rtx_cost_model.patch.
>
> What I have not done is check to see if removal of
> 300-mips_Os_cpu_rtx_cost_model.patch on gcc 7.1 solves the problem there, it
> could be that gcc 7.1 also had a bug.
>
> Cheers,
>
> Kevin
>
>
>
>
>>
>> - Felix
>>
>
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