[Buildroot] [PATCH 1/1] qemu: explicitly disable SSP support

[Arnout Vandecappelle]

On 10-11-15 18:18, Rodrigo Rebello wrote:
> Even though the QEMU configure script does a full compile and link test
> to detect SSP support, it does so by using the compiler option
> -fstack-protector-strong (and then -fstack-protector-all if that fails).
> 
> The problem with this method is that the test program passes the check
> with -fstack-protector-strong even when SSP support is not available in
> the toolchain, since that option restricts stack protection to only a
> subset of all the functions in a program and (in the case of the test
> program) no "canary" code gets inserted, producing a false-positive.
> This causes a subsequent failure when the probe for pthreads is
> performed.
> 
> To avoid patching the configure script, fix that by simply disabling the
> use of stack protector when SSP is known to be unavailable in the
> toolchain.

 Actually, it doesn't look too hard to patch the configure script, and that
would be upstreamable.

 But if you feel that that is too difficult, I'm OK with this patch.

 Regards,
 Arnout

> 
> Fixes:
> 
>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>   ...and many others.
> 
> Signed-off-by: Rodrigo Rebello <rprebello at gmail.com>
> ---
>  package/qemu/qemu.mk | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
> index 94e1bcf..0161b10 100644
> --- a/package/qemu/qemu.mk
> +++ b/package/qemu/qemu.mk
> @@ -133,6 +133,12 @@ QEMU_VARS = \
>  	PYTHON=$(HOST_DIR)/usr/bin/python2 \
>  	PYTHONPATH=$(TARGET_DIR)/usr/lib/python$(PYTHON_VERSION_MAJOR)/site-packages
>  
> +# Force disable stack protector when SSP isn't available in toolchain as
> +# QEMU configure script fails to properly detect that.
> +ifeq ($(BR2_TOOLCHAIN_HAS_SSP),)
> +QEMU_OPTS += --disable-stack-protector
> +endif
> +
>  # If we want to specify only a subset of targets, we must still enable all
>  # of them, so that QEMU properly builds its list of default targets, from
>  # which it then checks if the specified sub-set is valid. That's what we
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF