[Qemu-devel] [PATCH 5/6] build-sys: Change libqemuutil.a to qemuutil.o and link whole object

[Fam Zheng <famz@redhat.com>]

When an executable is being generated, unused functions from
libqemuutil.a are not linked. This is the linker's convention on
archives (libqemuutil.a).

Now that we have dynamically loaded modules, which may reference
function from libqemuutil.a but not linked in the executable, because
the executable itself didn't reference this symbol. That is a problem
for module build.

We can't link both executable and the dynamic shared object to
libqemuutil.a, because of the risk of inconsistent views of program
variables: DSO module sees a copy of some data because it is linked
against libqemuutil.a, whereas the executable sees another copy. In
other words, they each maintains a copy but with a same name. In this
case, it can be very tricky to notice such a duplication, and make a bug
hard to reason. So it's good to avoid it from the beginning.

This patch solves the above issue by fully linking. Specifically, it
fixes block-iscsi.mo: in block/iscsi.c, util/bitmap.c functions are
used, but qemu-img doesn't link it.

The solution is to link everything in libqemuutil.a. We do this by
changing it to qemuutil.o, which includes all the util objects. This is
easier and also expected to be more portable than "--whole-archive".

Because qemuutil.o is now fully linked and hence make executables
references more symbols than before, some test executables now need
libqemustub.a, so add them as necessary too.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 Makefile        | 17 +++++++++-------
 Makefile.objs   |  2 +-
 Makefile.target |  2 +-
 tests/Makefile  | 60 ++++++++++++++++++++++++++++-----------------------------
 4 files changed, 42 insertions(+), 39 deletions(-)

diff --git a/Makefile b/Makefile
index b33aaac..7cf5e51 100644
--- a/Makefile
+++ b/Makefile
@@ -187,7 +187,7 @@ subdir-dtc:dtc/libfdt dtc/tests
 dtc/%:
 	mkdir -p $@
 
-$(SUBDIR_RULES): libqemuutil.a libqemustub.a $(common-obj-y)
+$(SUBDIR_RULES): qemuutil.o libqemustub.a $(common-obj-y)
 
 ROMSUBDIR_RULES=$(patsubst %,romsubdir-%, $(ROMS))
 romsubdir-%:
@@ -208,7 +208,10 @@ Makefile: $(version-obj-y) $(version-lobj-y)
 # Build libraries
 
 libqemustub.a: $(stub-obj-y)
-libqemuutil.a: $(util-obj-y)
+
+qemuutil.o: CC_REL_FLAGS := -Wl,-r
+qemuutil.o: $(util-obj-y)
+	$(call quiet-command,$(CC) -nostdlib $(CC_REL_FLAGS) -o $@ $^,"  LD -r  $(TARGET_DIR)$@")
 
 block-modules = $(foreach o,$(block-obj-m),"$(basename $(subst /,-,$o))",) NULL
 util/module.o-cflags = -D'CONFIG_BLOCK_MODULES=$(block-modules)'
@@ -217,13 +220,13 @@ util/module.o-cflags = -D'CONFIG_BLOCK_MODULES=$(block-modules)'
 
 qemu-img.o: qemu-img-cmds.h
 
-qemu-img$(EXESUF): qemu-img.o $(block-obj-y) libqemuutil.a libqemustub.a
-qemu-nbd$(EXESUF): qemu-nbd.o $(block-obj-y) libqemuutil.a libqemustub.a
-qemu-io$(EXESUF): qemu-io.o $(block-obj-y) libqemuutil.a libqemustub.a
+qemu-img$(EXESUF): qemu-img.o $(block-obj-y) qemuutil.o libqemustub.a
+qemu-nbd$(EXESUF): qemu-nbd.o $(block-obj-y) qemuutil.o libqemustub.a
+qemu-io$(EXESUF): qemu-io.o $(block-obj-y) qemuutil.o libqemustub.a
 
 qemu-bridge-helper$(EXESUF): qemu-bridge-helper.o
 
-fsdev/virtfs-proxy-helper$(EXESUF): fsdev/virtfs-proxy-helper.o fsdev/virtio-9p-marshal.o libqemuutil.a libqemustub.a
+fsdev/virtfs-proxy-helper$(EXESUF): fsdev/virtfs-proxy-helper.o fsdev/virtio-9p-marshal.o qemuutil.o libqemustub.a
 fsdev/virtfs-proxy-helper$(EXESUF): LIBS += -lcap
 
 qemu-img-cmds.h: $(SRC_PATH)/qemu-img-cmds.hx
@@ -280,7 +283,7 @@ $(qapi-modules) $(SRC_PATH)/scripts/qapi-commands.py $(qapi-py)
 QGALIB_GEN=$(addprefix qga/qapi-generated/, qga-qapi-types.h qga-qapi-visit.h qga-qmp-commands.h)
 $(qga-obj-y) qemu-ga.o: $(QGALIB_GEN)
 
-qemu-ga$(EXESUF): $(qga-obj-y) libqemuutil.a libqemustub.a
+qemu-ga$(EXESUF): $(qga-obj-y) qemuutil.o libqemustub.a
 	$(call LINK, $^)
 
 clean:
diff --git a/Makefile.objs b/Makefile.objs
index 97db978..4847da7 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -109,6 +109,6 @@ target-obj-y += trace/
 # guest agent
 
 # FIXME: a few definitions from qapi-types.o/qapi-visit.o are needed
-# by libqemuutil.a.  These should be moved to a separate .json schema.
+# by qemuutil.o.  These should be moved to a separate .json schema.
 qga-obj-y = qga/
 qga-vss-dll-obj-y = qga/
diff --git a/Makefile.target b/Makefile.target
index 1e8d7ab..48a3089 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -176,7 +176,7 @@ all-obj-y += $(target-obj-y)
 all-obj-$(CONFIG_SOFTMMU) += $(block-obj-y)
 
 # build either PROG or PROGW
-$(QEMU_PROG_BUILD): $(all-obj-y) ../libqemuutil.a ../libqemustub.a
+$(QEMU_PROG_BUILD): $(all-obj-y) ../qemuutil.o ../libqemustub.a
 	$(call LINK,$^)
 
 gdbstub-xml.c: $(TARGET_XML_FILES) $(SRC_PATH)/scripts/feature_to_c.sh
diff --git a/tests/Makefile b/tests/Makefile
index 837e9c8..b79a299 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -226,22 +226,22 @@ qom-core-obj = qom/object.o qom/qom-qobject.o qom/container.o
 
 tests/test-x86-cpuid.o: QEMU_INCLUDES += -I$(SRC_PATH)/target-i386
 
-tests/check-qint$(EXESUF): tests/check-qint.o libqemuutil.a
-tests/check-qstring$(EXESUF): tests/check-qstring.o libqemuutil.a
-tests/check-qdict$(EXESUF): tests/check-qdict.o libqemuutil.a
-tests/check-qlist$(EXESUF): tests/check-qlist.o libqemuutil.a
-tests/check-qfloat$(EXESUF): tests/check-qfloat.o libqemuutil.a
-tests/check-qjson$(EXESUF): tests/check-qjson.o libqemuutil.a libqemustub.a
-tests/check-qom-interface$(EXESUF): tests/check-qom-interface.o $(qom-core-obj) libqemuutil.a libqemustub.a
-tests/test-coroutine$(EXESUF): tests/test-coroutine.o $(block-obj-y) libqemuutil.a libqemustub.a
-tests/test-aio$(EXESUF): tests/test-aio.o $(block-obj-y) libqemuutil.a libqemustub.a
-tests/test-rfifolock$(EXESUF): tests/test-rfifolock.o libqemuutil.a libqemustub.a
-tests/test-throttle$(EXESUF): tests/test-throttle.o $(block-obj-y) libqemuutil.a libqemustub.a
-tests/test-thread-pool$(EXESUF): tests/test-thread-pool.o $(block-obj-y) libqemuutil.a libqemustub.a
-tests/test-iov$(EXESUF): tests/test-iov.o libqemuutil.a
-tests/test-hbitmap$(EXESUF): tests/test-hbitmap.o libqemuutil.a libqemustub.a
+tests/check-qint$(EXESUF): tests/check-qint.o qemuutil.o libqemustub.a
+tests/check-qstring$(EXESUF): tests/check-qstring.o qemuutil.o libqemustub.a
+tests/check-qdict$(EXESUF): tests/check-qdict.o qemuutil.o libqemustub.a
+tests/check-qlist$(EXESUF): tests/check-qlist.o qemuutil.o libqemustub.a
+tests/check-qfloat$(EXESUF): tests/check-qfloat.o qemuutil.o libqemustub.a
+tests/check-qjson$(EXESUF): tests/check-qjson.o qemuutil.o libqemustub.a
+tests/check-qom-interface$(EXESUF): tests/check-qom-interface.o $(qom-core-obj) qemuutil.o libqemustub.a
+tests/test-coroutine$(EXESUF): tests/test-coroutine.o $(block-obj-y) qemuutil.o libqemustub.a
+tests/test-aio$(EXESUF): tests/test-aio.o $(block-obj-y) qemuutil.o libqemustub.a
+tests/test-rfifolock$(EXESUF): tests/test-rfifolock.o qemuutil.o libqemustub.a
+tests/test-throttle$(EXESUF): tests/test-throttle.o $(block-obj-y) qemuutil.o libqemustub.a
+tests/test-thread-pool$(EXESUF): tests/test-thread-pool.o $(block-obj-y) qemuutil.o libqemustub.a
+tests/test-iov$(EXESUF): tests/test-iov.o qemuutil.o libqemustub.a
+tests/test-hbitmap$(EXESUF): tests/test-hbitmap.o qemuutil.o libqemustub.a
 tests/test-x86-cpuid$(EXESUF): tests/test-x86-cpuid.o
-tests/test-xbzrle$(EXESUF): tests/test-xbzrle.o xbzrle.o page_cache.o libqemuutil.a
+tests/test-xbzrle$(EXESUF): tests/test-xbzrle.o xbzrle.o page_cache.o qemuutil.o libqemustub.a
 tests/test-cutils$(EXESUF): tests/test-cutils.o util/cutils.o
 tests/test-int128$(EXESUF): tests/test-int128.o
 tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \
@@ -250,10 +250,10 @@ tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \
 	hw/core/fw-path-provider.o \
 	$(qom-core-obj) \
 	$(test-qapi-obj-y) \
-	libqemuutil.a libqemustub.a
+	qemuutil.o libqemustub.a
 tests/test-vmstate$(EXESUF): tests/test-vmstate.o \
 	vmstate.o qemu-file.o \
-	libqemuutil.a
+	qemuutil.o libqemustub.a
 
 tests/test-qapi-types.c tests/test-qapi-types.h :\
 $(SRC_PATH)/tests/qapi-schema/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-types.py
@@ -276,18 +276,18 @@ $(SRC_PATH)/tests/qapi-schema/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-eve
 		$(gen-out-type) -o tests -p "test-" -i $<, \
 		"  GEN   $@")
 
-tests/test-string-output-visitor$(EXESUF): tests/test-string-output-visitor.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-string-input-visitor$(EXESUF): tests/test-string-input-visitor.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-qmp-event$(EXESUF): tests/test-qmp-event.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-qmp-output-visitor$(EXESUF): tests/test-qmp-output-visitor.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-qmp-input-visitor$(EXESUF): tests/test-qmp-input-visitor.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-qmp-input-strict$(EXESUF): tests/test-qmp-input-strict.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-qmp-commands$(EXESUF): tests/test-qmp-commands.o tests/test-qmp-marshal.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-visitor-serialization$(EXESUF): tests/test-visitor-serialization.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
-tests/test-opts-visitor$(EXESUF): tests/test-opts-visitor.o $(test-qapi-obj-y) libqemuutil.a libqemustub.a
+tests/test-string-output-visitor$(EXESUF): tests/test-string-output-visitor.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-string-input-visitor$(EXESUF): tests/test-string-input-visitor.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-qmp-event$(EXESUF): tests/test-qmp-event.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-qmp-output-visitor$(EXESUF): tests/test-qmp-output-visitor.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-qmp-input-visitor$(EXESUF): tests/test-qmp-input-visitor.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-qmp-input-strict$(EXESUF): tests/test-qmp-input-strict.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-qmp-commands$(EXESUF): tests/test-qmp-commands.o tests/test-qmp-marshal.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-visitor-serialization$(EXESUF): tests/test-visitor-serialization.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
+tests/test-opts-visitor$(EXESUF): tests/test-opts-visitor.o $(test-qapi-obj-y) qemuutil.o libqemustub.a
 
-tests/test-mul64$(EXESUF): tests/test-mul64.o libqemuutil.a
-tests/test-bitops$(EXESUF): tests/test-bitops.o libqemuutil.a
+tests/test-mul64$(EXESUF): tests/test-mul64.o qemuutil.o libqemustub.a
+tests/test-bitops$(EXESUF): tests/test-bitops.o qemuutil.o libqemustub.a
 
 libqos-obj-y = tests/libqos/pci.o tests/libqos/fw_cfg.o
 libqos-obj-y += tests/libqos/i2c.o
@@ -338,7 +338,7 @@ tests/ioh3420-test$(EXESUF): tests/ioh3420-test.o
 tests/usb-hcd-ehci-test$(EXESUF): tests/usb-hcd-ehci-test.o $(libqos-pc-obj-y)
 tests/vhost-user-test$(EXESUF): tests/vhost-user-test.o qemu-char.o qemu-timer.o $(qtest-obj-y)
 tests/qemu-iotests/socket_scm_helper$(EXESUF): tests/qemu-iotests/socket_scm_helper.o
-tests/test-qemu-opts$(EXESUF): tests/test-qemu-opts.o libqemuutil.a libqemustub.a
+tests/test-qemu-opts$(EXESUF): tests/test-qemu-opts.o qemuutil.o libqemustub.a
 
 ifeq ($(CONFIG_POSIX),y)
 LIBS += -lutil
@@ -352,7 +352,7 @@ QTEST_TARGETS=$(foreach TARGET,$(TARGETS), $(if $(check-qtest-$(TARGET)-y), $(TA
 check-qtest-y=$(foreach TARGET,$(TARGETS), $(check-qtest-$(TARGET)-y))
 endif
 
-qtest-obj-y = tests/libqtest.o libqemuutil.a libqemustub.a
+qtest-obj-y = tests/libqtest.o qemuutil.o libqemustub.a
 $(check-qtest-y): $(qtest-obj-y)
 
 .PHONY: check-help
-- 
2.0.3