[Buildroot] [PATCH] package/kvm-unit-tests: really fix build on Arch Linux x86_64

[Matthew Weber]

On Sun, Nov 17, 2019 at 12:41 PM Arnout Vandecappelle (Essensium/Mind)
<arnout at mind.be> wrote:
>
> On x86_64, we use the host compiler instead of the target compiler to
> build kvm-unit-tests, because it is built with -m32 and our target
> compiler doesn't support that.
>
> However, the compiler on Arch Linux is broken: it *always* builds with
> -fstack-protector, even when -ffreestanding is passed. However, when
> -fnostdlib is passed at link time (which is normally the case when
> building with -ffreestanding), it is not linked with the stack-protector
> library. This leads to a link time error:
>
> /usr/bin/ld: x86/realmode.o: in function `print_serial_u32':
> .../x86/realmode.c:104: undefined reference to `__stack_chk_fail'
>
> Since the entire package is built with -ffreestanding, it doesn't
> support stack-protector at all. Therefore, simply pass
> -fno-stack-protector explicitly on x86_64 to work around the bug in Arch
> Linux.
>
> Commit c0ffd16e4 tried to do this, but got the condition wrong:
> -fno-stack-protector was passed in all cases *except* for x86_64. This
> commit fixes that, by inverting the condition and moving the
> --cross-prefix part to the else branch.
>
> Fixes: (no new autobuild failures yet)
>
> Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>
> Cc: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> Cc: Matthew Weber <matthew.weber at rockwellcollins.com>

Oops, I'm pretty sure I tested this with that condition set
incorrectly.  I wonder if we have something else going on that masked
the problem because of commit c0ffd16e4  addition of
"$(KVM_UNIT_TESTS_MAKE_OPTS)" to the build/install cmds.

Reviewed-by: Matthew Weber <matthew.weber at rockwellcollins.com>

> ---
>  package/kvm-unit-tests/kvm-unit-tests.mk | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/package/kvm-unit-tests/kvm-unit-tests.mk b/package/kvm-unit-tests/kvm-unit-tests.mk
> index bb08c0603d..2637066701 100644
> --- a/package/kvm-unit-tests/kvm-unit-tests.mk
> +++ b/package/kvm-unit-tests/kvm-unit-tests.mk
> @@ -35,13 +35,14 @@ KVM_UNIT_TESTS_CONF_OPTS =\
>  # compiler. However, for x86-64, we use the host compiler, as
>  # kvm-unit-tests builds 32 bit code, which Buildroot toolchains for
>  # x86-64 cannot do.
> -ifneq ($(BR2_x86_64),y)
> -KVM_UNIT_TESTS_CONF_OPTS += --cross-prefix="$(TARGET_CROSS)"
> +ifeq ($(BR2_x86_64),y)
>  # Arch Linux adds -fstack-protector even when building with -ffreestanding, but
>  # it doesn't link with the stack-protector library when -nostdlib is passed,
>  # which leads to a link error. Therefore, disable it explicitly to work around
>  # this bug in Arch Linux. https://bugs.archlinux.org/task/64270
>  KVM_UNIT_TESTS_MAKE_OPTS += EXTRA_CFLAGS=-fno-stack-protector
> +else
> +KVM_UNIT_TESTS_CONF_OPTS += --cross-prefix="$(TARGET_CROSS)"
>  endif
>
>  define KVM_UNIT_TESTS_CONFIGURE_CMDS
> --
> 2.21.0
>