[Xen-devel] [XTF PATCH] build: disable PIE during linking if necessary

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Starting from ee3e265688, $(CC) is used for linking. That means all
default $(CC) flags coming from distro takes effect.

On Debian Stretch, gcc contains -pie by default, which makes the final
object fail to link. We need to explicitly disable PIE when linking.
Since not all versions of gcc support -no-pie, test its availability
before adding.

Example error message:

/usr/bin/ld: /local/work/xtf.git/arch/x86/boot/head_pv64.o: relocation 
R_X86_64_32S against symbol `start_info' can not be used when making a shared 
object;
recompile with -fPIC
/usr/bin/ld: /local/work/xtf.git/arch/x86/entry_64-pv64.o: relocation 
R_X86_64_32S against `.text' can not be used when making a shared object; 
recompile with
-fPIC
/usr/bin/ld: final link failed: Nonrepresentable section on output
collect2: error: ld returned 1 exit status

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 build/common.mk | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/build/common.mk b/build/common.mk
index 7c4870e..8e08c7e 100644
--- a/build/common.mk
+++ b/build/common.mk
@@ -50,6 +50,15 @@ obj-perarch :=
 obj-perenv  :=
 include $(ROOT)/build/files.mk
 
+
+cc-option = $(shell if [ -z "`echo 'int p=1;' | $(CC) $(1) -S -o /dev/null -x 
c - 2>&1`" ]; \
+                       then echo y; else echo n; fi)
+
+# Disable PIE, but need to check if compiler supports it
+ifeq ($(call cc-option,-no-pie),y)
+DISABLE_PIE_LDFLAGS := -no-pie
+endif
+
 # Run once per environment to set up some common bits & pieces
 define PERENV_setup
 
@@ -61,7 +70,7 @@ CFLAGS_$(1) := $$(CFLAGS_$($(1)_arch)) $$(COMMON_CFLAGS-$(1)) 
-DCONFIG_ENV_$(1)
 
 link-$(1) := $(ROOT)/arch/x86/link-$(1).lds
 
-LDFLAGS_$(1) := -Wl,-T,$$(link-$(1)) -nostdlib
+LDFLAGS_$(1) := -Wl,-T,$$(link-$(1)) -nostdlib $(DISABLE_PIE_LDFLAGS)
 
 # Needs to pick up test-provided obj-perenv and obj-perarch
 DEPS-$(1) = $(head-$(1)) \
-- 
2.11.0


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