[Qemu-devel] [PATCH] Support for loading devices as dynamic libraries

["Dominik Żeromski" <dzeromsk@gmail.com>]

Adding support for loading DSO with -device option.

Example Makefile for out of tree modules:
#v+
DEVICENAME=pcnet2

hw-obj-y=pcnet-pci.o
hw-obj-y+=pcnet.o

include rules.mak

.PHONY: all

QEMU_CFLAGS=-I../qemu-kvm -I../qemu-kvm/hw 
QEMU_CFLAGS+=-I../qemu-kvm/fpu -I../qemu-kvm/include
QEMU_CFLAGS+=-I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include

QEMU_CFLAGS+=-DTARGET_PHYS_ADDR_BITS=64 -fPIC
LDFLAGS+=-shared

LIBNAME=libqemu_$(DEVICENAME).so

all: $(LIBNAME)

$(LIBNAME): $(hw-obj-y)
	$(call LINK,$^)

clean:
	rm -f *.o
	rm -f *.d
	rm -f $(LIBNAME)

# Include automatically generated dependency files
-include $(patsubst %.o, %.d, $(hw-obj-y))

#v-

Signed-off-by: Dominik Żeromski <dzeromsk@gmail.com>
---
 Makefile.target   |    4 +++-
 hw/qdev-monitor.c |   11 +++++++++++
 2 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/Makefile.target b/Makefile.target
index 74f7a4a..7fd9245 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -130,7 +130,9 @@ obj-$(CONFIG_HAVE_GET_MEMORY_MAPPING) += memory_mapping.o
 obj-$(CONFIG_HAVE_CORE_DUMP) += dump.o
 obj-$(CONFIG_NO_GET_MEMORY_MAPPING) += memory_mapping-stub.o
 obj-$(CONFIG_NO_CORE_DUMP) += dump-stub.o
-LIBS+=-lz
+LIBS+=-lz -ldl
+
+LDFLAGS+=-rdynamic
 
 QEMU_CFLAGS += $(VNC_TLS_CFLAGS)
 QEMU_CFLAGS += $(VNC_SASL_CFLAGS)
diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
index 7915b45..3b5b0b0 100644
--- a/hw/qdev-monitor.c
+++ b/hw/qdev-monitor.c
@@ -17,6 +17,8 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <dlfcn.h>
+
 #include "qdev.h"
 #include "monitor.h"
 #include "qmp-commands.h"
@@ -402,6 +404,8 @@ DeviceState *qdev_device_add(QemuOpts *opts)
     const char *driver, *path, *id;
     DeviceState *qdev;
     BusState *bus;
+    void *libhandle;
+    char libname[NAME_MAX];
 
     driver = qemu_opt_get(opts, "driver");
     if (!driver) {
@@ -419,7 +423,14 @@ DeviceState *qdev_device_add(QemuOpts *opts)
             obj = object_class_by_name(driver);
         }
     }
+    if (!obj) {
+        snprintf(libname, sizeof(libname), "libqemu_%s.so", driver);
 
+        libhandle = dlopen(libname, RTLD_NOW);
+        if (libhandle != NULL) {
+            obj = object_class_by_name(driver);
+        }
+    }
     if (!obj) {
         qerror_report(QERR_INVALID_PARAMETER_VALUE, "driver", "device type");
         return NULL;
-- 
1.7.0.4