build: Added support for building QEMU as a shared library

Makefile

@@ -558,6 +558,16 @@ Makefile: $(version-obj-y)
 libqemuutil.a: $(util-obj-y) $(trace-obj-y) $(stub-obj-y)
 libvhost-user.a: $(libvhost-user-obj-y) $(util-obj-y) $(stub-obj-y)
 
+ifdef CONFIG_DARWIN
+QEMU_IMG_SHARED_LIBRARY=libqemu-img.dylib
+else
+QEMU_IMG_SHARED_LIBRARY=libqemu-img.so
+endif
+SOBJS=$(QEMU_IMG_SHARED_LIBRARY)
+ifdef CONFIG_SHARED_LIB
+all: $(SOBJS)
+endif
+
 ######################################################################
 
 COMMON_LDADDS = libqemuutil.a
@@ -565,6 +575,11 @@ COMMON_LDADDS = libqemuutil.a
 qemu-img.o: qemu-img-cmds.h
 
 qemu-img$(EXESUF): qemu-img.o $(authz-obj-y) $(block-obj-y) $(crypto-obj-y) $(io-obj-y) $(qom-obj-y) $(COMMON_LDADDS)
+
+$(QEMU_IMG_SHARED_LIBRARY): LDFLAGS += $(LDFLAGS_SHARED)
+$(QEMU_IMG_SHARED_LIBRARY): qemu-img.o $(authz-obj-y) $(block-obj-y) $(crypto-obj-y) $(io-obj-y) $(qom-obj-y) $(COMMON_LDADDS)
+	$(call LINK, $(filter-out %.mak, $^))
+
 qemu-nbd$(EXESUF): qemu-nbd.o $(authz-obj-y) $(block-obj-y) $(crypto-obj-y) $(io-obj-y) $(qom-obj-y) $(COMMON_LDADDS)
 qemu-io$(EXESUF): qemu-io.o $(authz-obj-y) $(block-obj-y) $(crypto-obj-y) $(io-obj-y) $(qom-obj-y) $(COMMON_LDADDS)
 
@@ -712,6 +727,7 @@ clean: recurse-clean
 		-exec rm {} +
 	rm -f $(edk2-decompressed)
 	rm -f $(filter-out %.tlb,$(TOOLS)) $(HELPERS-y) TAGS cscope.* *.pod *~ */*~
+	rm -f $(SOBJS)
 	rm -f fsdev/*.pod scsi/*.pod
 	rm -f qemu-img-cmds.h
 	rm -f ui/shader/*-vert.h ui/shader/*-frag.h
@@ -873,6 +889,11 @@ install: all $(if $(BUILD_DOCS),install-doc) \
 ifneq ($(TOOLS),)
 	$(call install-prog,$(TOOLS),$(DESTDIR)$(bindir))
 endif
+ifdef CONFIG_SHARED_LIB
+ifneq ($(SOBJS),)
+	$(call install-so,$(SOBJS),$(DESTDIR)$(libdir))
+endif
+endif
 ifneq ($(CONFIG_MODULES),)
 	$(INSTALL_DIR) "$(DESTDIR)$(qemu_moddir)"
 	for s in $(modules-m:.mo=$(DSOSUF)); do \

Makefile.target

@@ -37,6 +37,14 @@ endif
 endif
 
 PROGS=$(QEMU_PROG) $(QEMU_PROGW)
+
+ifdef CONFIG_DARWIN
+QEMU_SHARED_LIBRARY=lib$(QEMU_PROG).dylib
+else
+QEMU_SHARED_LIBRARY=lib$(QEMU_PROG).so
+endif
+SOBJS=$(QEMU_SHARED_LIBRARY)
+
 STPFILES=
 
 config-target.h: config-target.h-timestamp
@@ -98,7 +106,11 @@ stap:
 endif
 .PHONY: stap
 
+ifdef CONFIG_SHARED_LIB
+all: $(SOBJS) stap
+else
 all: $(PROGS) stap
+endif
 
 # Dummy command so that make thinks it has done something
 	@true
@@ -211,6 +223,10 @@ ifdef CONFIG_DARWIN
 	$(call quiet-command,SetFile -a C $@,"SETFILE","$(TARGET_DIR)$@")
 endif
 
+$(QEMU_SHARED_LIBRARY): LDFLAGS += $(LDFLAGS_SHARED)
+$(QEMU_SHARED_LIBRARY): $(all-obj-y) $(COMMON_LDADDS)
+	$(call LINK, $(filter-out %.mak, $^))
+
 gdbstub-xml.c: $(TARGET_XML_FILES) $(SRC_PATH)/scripts/feature_to_c.sh
 	$(call quiet-command,rm -f $@ && $(SHELL) $(SRC_PATH)/scripts/feature_to_c.sh $@ $(TARGET_XML_FILES),"GEN","$(TARGET_DIR)$@")
 
@@ -221,7 +237,7 @@ hmp-commands-info.h: $(SRC_PATH)/hmp-commands-info.hx $(SRC_PATH)/scripts/hxtool
 	$(call quiet-command,sh $(SRC_PATH)/scripts/hxtool -h < $< > $@,"GEN","$(TARGET_DIR)$@")
 
 clean: clean-target
-	rm -f *.a *~ $(PROGS)
+	rm -f *.a *~ $(PROGS) $(SOBJS)
 	rm -f $(shell find . -name '*.[od]')
 	rm -f hmp-commands.h gdbstub-xml.c
 	rm -f trace/generated-helpers.c trace/generated-helpers.c-timestamp
@@ -230,9 +246,15 @@ ifdef CONFIG_TRACE_SYSTEMTAP
 endif
 
 install: all
+ifdef CONFIG_SHARED_LIB
+ifneq ($(SOBJS),)
+	$(call install-so,$(SOBJS),$(DESTDIR)$(libdir))
+endif
+else
 ifneq ($(PROGS),)
 	$(call install-prog,$(PROGS),$(DESTDIR)$(bindir))
 endif
+endif
 ifdef CONFIG_TRACE_SYSTEMTAP
 	$(INSTALL_DIR) "$(DESTDIR)$(qemu_datadir)/../systemtap/tapset"
 	$(INSTALL_DATA) $(QEMU_PROG).stp-installed "$(DESTDIR)$(qemu_datadir)/../systemtap/tapset/$(QEMU_PROG).stp"

configure

@@ -505,6 +505,7 @@ libpmem=""
 default_devices="yes"
 plugins="no"
 host_device_support="yes"
+shared_lib="no"
 
 supported_cpu="no"
 supported_os="no"
@@ -859,6 +860,7 @@ Darwin)
   darwin="yes"
   hax="yes"
   hvf="yes"
+  DSOSUF=".dylib"
   LDFLAGS_SHARED="-bundle -undefined dynamic_lookup"
   if [ "$cpu" = "x86_64" ] ; then
     QEMU_CFLAGS="-arch x86_64 $QEMU_CFLAGS"
@@ -881,7 +883,8 @@ iOS)
   ios="yes"
   hax="yes"
   hvf="yes"
-  LDFLAGS_SHARED="-bundle -undefined dynamic_lookup"
+  DSOSUF=".dylib"
+  LDFLAGS_SHARED="-dynamiclib"
   if [ "$cpu" = "x86_64" ] ; then
     QEMU_CFLAGS="-arch x86_64 $QEMU_CFLAGS"
     LDFLAGS="-arch x86_64 $LDFLAGS"
@@ -1578,6 +1581,14 @@ for opt do
   ;;
   --disable-plugins) plugins="no"
   ;;
+  --enable-shared-lib)
+      shared_lib=yes
+      want_tools=no
+      QEMU_CFLAGS="$QEMU_CFLAGS -fPIC"
+      DSOSUF="-module$DSOSUF" # fix for make 2.81 not building target order correctly
+  ;;
+  --disable-shared-lib) shared_lib=no
+  ;;
   *)
       echo "ERROR: unknown option $opt"
       echo "Try '$0 --help' for more information"
@@ -1761,6 +1772,7 @@ Advanced options (experts only):
                            track the maximum stack usage of stacks created by qemu_alloc_stack
   --enable-plugins
                            enable plugins via shared library loading
+  --enable-shared-lib      build QEMU as a shared library instead of an application
 
 Optional features, enabled with --enable-FEATURE and
 disabled with --disable-FEATURE, default is enabled if available:
@@ -6639,6 +6651,7 @@ echo "libudev           $libudev"
 echo "default devices   $default_devices"
 echo "plugin support    $plugins"
 echo "host device support  $host_device_support"
+echo "build shared lib  $shared_lib"
 
 if test "$supported_cpu" = "no"; then
     echo
@@ -6718,6 +6731,9 @@ fi
 if test "$host_device_support" = "yes" ; then
   echo "CONFIG_HOST_DEVICE=y" >> $config_host_mak
 fi
+if test "$shared_lib" = "yes" ; then
+  echo "CONFIG_SHARED_LIB=y" >> $config_host_mak
+fi
 if test "$debug_tcg" = "yes" ; then
   echo "CONFIG_DEBUG_TCG=y" >> $config_host_mak
 fi

qemu-img.c

@@ -49,6 +49,11 @@
 #include "crypto/init.h"
 #include "trace/control.h"
 
+#if defined(CONFIG_SHARED_LIB)
+#undef main
+#define main qemu_img_main
+#endif
+
 #define QEMU_IMG_VERSION "qemu-img version " QEMU_FULL_VERSION \
                           "\n" QEMU_COPYRIGHT "\n"
 

rules.mak

@@ -154,6 +154,12 @@ define install-prog
 	$(if $(STRIP),$(STRIP) $(foreach T,$1,"$2/$(notdir $T)"),)
 endef
 
+# install-so list, dir
+define install-so
+    $(INSTALL_DIR) "$2"
+    $(INSTALL_LIB) $1 "$2"
+endef
+
 # find-in-path
 # Usage: $(call find-in-path, prog)
 # Looks in the PATH if the argument contains no slash, else only considers one

vl.c

@@ -49,7 +49,7 @@ int main(int argc, char **argv)
 #endif
 #endif /* CONFIG_SDL */
 
-#ifdef CONFIG_COCOA
+#if defined(CONFIG_COCOA) || defined(CONFIG_SHARED_LIB)
 #undef main
 #define main qemu_main
 #endif /* CONFIG_COCOA */