[XEN PATCH v8 25/47] build: rework coverage and ubsan CFLAGS handling

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

When assigning a value a target-specific variable, that also affect
prerequisite of the target. This is mostly fine, but there is one case
where we will not want the COV_FLAGS added to the CFLAGS.

In arch/x86/boot, we have "head.o" with "cmdline.S" as prerequisite
and ultimately "cmdline.o", we don't want COV_FLAGS to that last one.

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---

Notes:
    v8:
    - reorder target-specific assignments
    - fix typo in comment
    - reviewed

 xen/Rules.mk | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/xen/Rules.mk b/xen/Rules.mk
index 9eb3093f43fb..d6eabd3415b5 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -126,19 +126,31 @@ targets += $(targets-for-builtin)
 
 $(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS-y += 
-DINIT_SECTIONS_ONLY
 
+non-init-objects = $(filter-out %.init.o, $(obj-y) $(obj-bin-y) $(extra-y))
+
 ifeq ($(CONFIG_COVERAGE),y)
 ifeq ($(CONFIG_CC_IS_CLANG),y)
     COV_FLAGS := -fprofile-instr-generate -fcoverage-mapping
 else
     COV_FLAGS := -fprofile-arcs -ftest-coverage
 endif
-$(filter-out %.init.o $(nocov-y),$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS-y 
+= $(COV_FLAGS)
+
+# Reset COV_FLAGS in cases where an objects has another one as prerequisite
+$(nocov-y) $(filter %.init.o, $(obj-y) $(obj-bin-y) $(extra-y)): \
+    COV_FLAGS :=
+
+$(non-init-objects): _c_flags += $(COV_FLAGS)
 endif
 
 ifeq ($(CONFIG_UBSAN),y)
 # Any -fno-sanitize= options need to come after any -fsanitize= options
-$(filter-out %.init.o $(noubsan-y),$(obj-y) $(obj-bin-y) $(extra-y)): \
-CFLAGS-y += $(filter-out -fno-%,$(CFLAGS_UBSAN)) $(filter 
-fno-%,$(CFLAGS_UBSAN))
+UBSAN_FLAGS := $(filter-out -fno-%,$(CFLAGS_UBSAN)) $(filter 
-fno-%,$(CFLAGS_UBSAN))
+
+# Reset UBSAN_FLAGS in cases where an objects has another one as prerequisite
+$(noubsan-y) $(filter %.init.o, $(obj-y) $(obj-bin-y) $(extra-y)): \
+    UBSAN_FLAGS :=
+
+$(non-init-objects): _c_flags += $(UBSAN_FLAGS)
 endif
 
 ifeq ($(CONFIG_LTO),y)
@@ -167,6 +179,9 @@ a_flags = -MMD -MP -MF $(depfile) $(XEN_AFLAGS)
 
 include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
 
+c_flags += $(_c_flags)
+a_flags += $(_c_flags)
+
 c_flags += $(CFLAGS-y)
 a_flags += $(CFLAGS-y) $(AFLAGS-y)
 
-- 
Anthony PERARD