module: implement module loading

This patch adds loading, stamp checking and initialization of modules.

The init function of dynamic module is no longer directly called as
__attribute__((constructor)) in static linked version, it is called
only after passed the checking of presense of stamp symbol:

    qemu_stamp_$RELEASEHASH

where $RELEASEHASH is generated by hashing version strings and content
of configure script.

With this, modules built from a different tree/version/configure will
not be loaded.

The module loading code requires gmodule-2.0.

Modules are searched under
 - CONFIG_MODDIR
 - executable folder (to allow running qemu-{img,io} in the build
   directory)
 - ../ of executable folder (to allow running system emulator in the
   build directory)

Modules are linked under their subdir respectively, then copied to top
level of build directory for above convinience, e.g.:
    $(BUILD_DIR)/block/curl.so -> $(BUILD_DIR)/block-curl.so

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 22 insertions, 1 deletions

diff --git a/include/qemu/module.h b/include/qemu/module.h
index c4ccd57166..72d94984a2 100644
--- a/include/qemu/module.h
+++ b/include/qemu/module.h
@@ -14,11 +14,31 @@
 #ifndef QEMU_MODULE_H
 #define QEMU_MODULE_H
 
+#include "qemu/osdep.h"
+
+#define DSO_STAMP_FUN         glue(qemu_stamp, CONFIG_STAMP)
+#define DSO_STAMP_FUN_STR     stringify(DSO_STAMP_FUN)
+
+#ifdef BUILD_DSO
+void DSO_STAMP_FUN(void);
+/* This is a dummy symbol to identify a loaded DSO as a QEMU module, so we can
+ * distinguish "version mismatch" from "not a QEMU module", when the stamp
+ * check fails during module loading */
+void qemu_module_dummy(void);
+
+#define module_init(function, type)                                         \
+static void __attribute__((constructor)) do_qemu_init_ ## function(void)    \
+{                                                                           \
+    register_dso_module_init(function, type);                               \
+}
+#else
 /* This should not be used directly.  Use block_init etc. instead.  */
 #define module_init(function, type)                                         \
-static void __attribute__((constructor)) do_qemu_init_ ## function(void) {  \
+static void __attribute__((constructor)) do_qemu_init_ ## function(void)    \
+{                                                                           \
     register_module_init(function, type);                                   \
 }
+#endif
 
 typedef enum {
     MODULE_INIT_BLOCK,
@@ -34,6 +54,7 @@ typedef enum {
 #define type_init(function) module_init(function, MODULE_INIT_QOM)
 
 void register_module_init(void (*fn)(void), module_init_type type);
+void register_dso_module_init(void (*fn)(void), module_init_type type);
 
 void module_call_init(module_init_type type);