[PATCH] coverage: filter out lib{fdt,elf}-temp.o

[Michal Orzel <michal.orzel@xxxxxxx>]

At the moment, trying to run xencov read/reset (calling SYSCTL_coverage_op
under the hood) results in a crash. This is due to an attempt to
access code in the .init.* sections (libfdt for Arm and libelf for x86)
that are stripped after boot. Normally, the build system compiles any
*.init.o file without COV_FLAGS. However, these two libraries are
handled differently as sections will be renamed to init after linking.

This worked until e321576f4047 ("xen/build: start using if_changed")
that added lib{fdt,elf}-temp.o to extra-y. Any file listed there without
*.init.o suffix will be part of non-init-objects for which COV_FLAGS
will be appended. In such case, the solution is to add a file to nocov-y.

Also, for libfdt, append to nocov-y only if CONFIG_OVERLAY_DTB is not
set. Otherwise, there is no section renaming and we should be able to
run the coverage.

Fixes: e321576f4047 ("xen/build: start using if_changed")
Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
---
 xen/common/libelf/Makefile | 2 +-
 xen/common/libfdt/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/common/libelf/Makefile b/xen/common/libelf/Makefile
index 8a4522e4e141..f618f70d5c8e 100644
--- a/xen/common/libelf/Makefile
+++ b/xen/common/libelf/Makefile
@@ -1,5 +1,5 @@
 obj-bin-y := libelf.o
-nocov-y += libelf.o
+nocov-y += libelf.o libelf-temp.o
 libelf-objs := libelf-tools.o libelf-loader.o libelf-dominfo.o
 
 SECTIONS := text data $(SPECIAL_DATA_SECTIONS)
diff --git a/xen/common/libfdt/Makefile b/xen/common/libfdt/Makefile
index d50487aa6e32..fb0d8a48eee2 100644
--- a/xen/common/libfdt/Makefile
+++ b/xen/common/libfdt/Makefile
@@ -5,10 +5,10 @@ SECTIONS := text data $(SPECIAL_DATA_SECTIONS)
 # For CONFIG_OVERLAY_DTB, libfdt functionalities will be needed during runtime.
 ifneq ($(CONFIG_OVERLAY_DTB),y)
 OBJCOPYFLAGS := $(foreach s,$(SECTIONS),--rename-section .$(s)=.init.$(s))
+nocov-y += libfdt.o libfdt-temp.o
 endif
 
 obj-y += libfdt.o
-nocov-y += libfdt.o
 
 CFLAGS-y += -I$(srctree)/include/xen/libfdt/
 
-- 
2.25.1