Re: [Qemu-devel] [PATCH v4 2/2] Build usermode targets as PIE

[Arnaud Patard (Rtp) <arnaud.patard@rtp-net.org>]

"Kirill A. Shutemov" <kirill@shutemov.name> writes:

Hi,

[...]

> +cat > $TMPC <<EOF
> +int main() {
> +	static __thread int i = 0;
> +	i++;
> +	return 0;
> +}
> +EOF
> +
> +if test "$user_pie" != "no" ; then
> +    if compile_prog "-fpie" "-pie -Wl,--fatal-warnings -Wl,--warn-shared-textrel"; then
> +        user_pie="yes"
> +    else
> +        if test "$user_pie" = "yes"; then
> +            echo "Toolchain has no proper PIE support"
> +            exit 1
> +        else
> +            user_pie="no"
> +        fi
> +    fi
> +fi

Unfortunately, the broken mips toolchain pass this test. When you
compile, you're getting no warning at all. Moreover, the failure is
triggered at run-time (and this test doesn't trigger it). See
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=526961 if you want
something which segfault with pie.
I don't know if there are some other non-mips toolchains with broken pie
and what's their behaviour. I hope it's crashing too...


Arnaud