x86, vdso: Error out if the vdso contains external references
The vdso is a piece of userspace code which is supposed to be fully
self-contained. Any external (undefined) reference is an error, and
should be caught at compile time. This was giving us trouble when
compiling with -Os on gcc 4.5.0, for example (failed inline).
The need to do a buildtime check was pointed out by Andi Kleen.
Reported-by: Andi Kleen <andi@firstfloor.org>
LKML-Reference: <tip-*@vger.kernel.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
index 6b4ffed..4a2afa1 100644
--- a/arch/x86/vdso/Makefile
+++ b/arch/x86/vdso/Makefile
@@ -120,7 +120,8 @@
quiet_cmd_vdso = VDSO $@
cmd_vdso = $(CC) -nostdlib -o $@ \
$(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
- -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^)
+ -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \
+ sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
GCOV_PROFILE := n