[Buildroot] [PATCH 1/1] package/ruby: disable use of stack protector when not available

[Thomas Petazzoni]

Brendan,

On Wed, 16 Sep 2015 22:29:01 +0100, Brendan Heading wrote:

> Yes I agree. This is a toolchain compilation issue and the right place
> to solve it is there.
> 
> By way of an update, during the host-gcc-final build there is a check
> for the symbol __stack_chk_fail. Under glibc and uclibc this test
> fails, as expected. But under uclibc-ng, this test passes (ie returns
> "yes") when it should actually fail, even though the symbol is
> definitely not present. Inside the configure script there is some
> logic that can cause it to return "yes" (for example, buildroot added
> a patch such that when musl is detected it's hardcoded to always
> return yes) so I'm trying to work out what code path in there is doing
> this.
> 
> The presence of this symbol leads, ultimately, to slightly different
> GCC specs. If it thinks that the target C library does not provide
> SSP, GCC tries to link in its own SSP support libraries. This is the
> path that is supposed to be executed. However, in the uclibc-ng case
> we are wrongly detecting that the C library *does* have SSP even
> though it doesn't. This causes the specs *not* to link the SSP support
> libraries.
> 
> The reason why configure doesn't flag up a linker error in these
> circumstances is because the conftest.c program is too simple. A
> "hello world" type program does no stack operations and hence GCC
> never emits any of the stack checking calls. So the problem slips
> through the configure script.
> 
> So, once I've found out why uclibc-ng is triggering the false positive
> in the GCC build I'll send in a patch.

Thanks for the update. However, notice that the toolchain at
http://autobuild.buildroot.org/toolchains/tarballs/br-arm-full-2015.08-rc1-38-gad0f85e.tar.bz2
is capable of building sudo and ruby, even if:

 1/ It is using uClibc-ng 1.0.5
 2/ It has SSP disabled: #undef __UCLIBC_HAS_SSP__

So it's not simply a matter of uClibc vs. uClibc-ng, since one
uClibc-ng toolchains works fine.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com