Re: [RFC PATCH 4/7] kconfig: support new special property shell=

[Ulf Magnusson]

On Sun, Feb 11, 2018 at 10:05 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Sun, Feb 11, 2018 at 10:34 AM, Ulf Magnusson <ulfalizer@xxxxxxxxx> wrote:
>> On Sun, Feb 11, 2018 at 6:56 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>>> Old? That's not the case. The check for -fno-stack-protector will
>>> likely be needed forever, as some distro compilers enable
>>> stack-protector by default. So when someone wants to explicitly build
>>> without stack-protector (or if the compiler's stack-protector is
>>> detected as broken), we must force it off for the kernel build.
>>
>> What I meant is whether it makes sense to test if the
>> -fno-stack-protector option is supported. Can we reasonably assume
>> that passing -fno-stack-protector to the compiler won't cause an
>> error?
>
> That isn't something I've tested; but I can check if it's useful.

If it gets rid of a pointless test and symbol, I think it's useful, so
that would be nice. :)

>> Is it possible to build GCC with no "no stack protector" support? Do
>> we need to support any compilers that would choke on the
>> -fno-stack-protector flag itself?
>>
>> If we can reasonably assume that passing -fno-stack-protector is safe,
>> then CC_HAS_STACKPROTECTOR_NONE isn't needed.
>
> Well, there are two situations:
>
> - does the user want to build _without_ stack protector? (which is
> something some people want to do, no matter what I think of it)
>
> - did _AUTO discover that stack protector output is broken?
>
> In both cases, we need to pass -fno-stack-protector in case the distro
> compiler was built with stack protector enabled by default.

Yup, that's already the way it would work. Currently, there's also a
test for whether the compiler supports -fno-stack-protector. It's that
one that I suspect we might be able to get rid of.

Cheers,
Ulf "should merge replies"