[Qemu-devel] [PATCH v16 6/9] module: implement module loading

[Fam Zheng <famz@redhat.com>]

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.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 Makefile              |   3 ++
 configure             |  37 ++++++++++-------
 include/qemu/module.h |  18 ++++++++-
 module-common.c       |  10 +++++
 rules.mak             |   7 ++--
 scripts/create_config |  14 +++++++
 util/module.c         | 107 +++++++++++++++++++++++++++++++++++++++++++++++++-
 7 files changed, 176 insertions(+), 20 deletions(-)
 create mode 100644 module-common.c

diff --git a/Makefile b/Makefile
index 9de66cb..670ce44 100644
--- a/Makefile
+++ b/Makefile
@@ -203,6 +203,9 @@ Makefile: $(version-obj-y) $(version-lobj-y)
 libqemustub.a: $(stub-obj-y)
 libqemuutil.a: $(util-obj-y) qapi-types.o qapi-visit.o
 
+block-modules = $(foreach o,$(block-obj-m),"$(basename $(subst /,-,$o))",) NULL
+util/module.o-cflags = -D'CONFIG_BLOCK_MODULES=$(block-modules)'
+
 ######################################################################
 
 qemu-img.o: qemu-img-cmds.h
diff --git a/configure b/configure
index a6a626f..77f09ba 100755
--- a/configure
+++ b/configure
@@ -677,7 +677,8 @@ for opt do
   ;;
   --disable-debug-info)
   ;;
-  --enable-modules) modules="yes"
+  --enable-modules)
+      modules="yes"
   ;;
   --cpu=*)
   ;;
@@ -1130,7 +1131,7 @@ Advanced options (experts only):
   --libdir=PATH            install libraries in PATH
   --sysconfdir=PATH        install config in PATH$confsuffix
   --localstatedir=PATH     install local state in PATH (set at runtime on win32)
-  --with-confsuffix=SUFFIX suffix for QEMU data inside datadir and sysconfdir [$confsuffix]
+  --with-confsuffix=SUFFIX suffix for QEMU data inside datadir/libdir/sysconfdir [$confsuffix]
   --enable-modules         enable modules support
   --enable-debug-tcg       enable TCG debugging
   --disable-debug-tcg      disable TCG debugging (default)
@@ -2346,15 +2347,19 @@ if test "$mingw32" = yes; then
 else
     glib_req_ver=2.12
 fi
-if $pkg_config --atleast-version=$glib_req_ver gthread-2.0; then
-    glib_cflags=`$pkg_config --cflags gthread-2.0`
-    glib_libs=`$pkg_config --libs gthread-2.0`
-    CFLAGS="$glib_cflags $CFLAGS"
-    LIBS="$glib_libs $LIBS"
-    libs_qga="$glib_libs $libs_qga"
-else
-    error_exit "glib-$glib_req_ver required to compile QEMU"
-fi
+
+for i in gthread-2.0 gmodule-2.0; do
+    if $pkg_config --atleast-version=$glib_req_ver $i; then
+        glib_cflags=`$pkg_config --cflags $i`
+        glib_libs=`$pkg_config --libs $i`
+        CFLAGS="$glib_cflags $CFLAGS"
+        LIBS="$glib_libs $LIBS"
+        libs_qga="$glib_libs $libs_qga"
+    else
+        error_exit "glib-$glib_req_ver $i is required to compile QEMU"
+    fi
+done
+
 
 ##########################################
 # pixman support probe
@@ -3628,6 +3633,7 @@ if test "$mingw32" = "yes" ; then
 fi
 
 qemu_confdir=$sysconfdir$confsuffix
+moddir=$libdir$confsuffix
 qemu_datadir=$datadir$confsuffix
 qemu_localedir="$datadir/locale"
 
@@ -3718,6 +3724,7 @@ echo "Install prefix    $prefix"
 echo "BIOS directory    `eval echo $qemu_datadir`"
 echo "binary directory  `eval echo $bindir`"
 echo "library directory `eval echo $libdir`"
+echo "module directory  `eval echo $moddir`"
 echo "libexec directory `eval echo $libexecdir`"
 echo "include directory `eval echo $includedir`"
 echo "config directory  `eval echo $sysconfdir`"
@@ -3849,6 +3856,7 @@ echo all: >> $config_host_mak
 echo "prefix=$prefix" >> $config_host_mak
 echo "bindir=$bindir" >> $config_host_mak
 echo "libdir=$libdir" >> $config_host_mak
+echo "moddir=$moddir" >> $config_host_mak
 echo "libexecdir=$libexecdir" >> $config_host_mak
 echo "includedir=$includedir" >> $config_host_mak
 echo "mandir=$mandir" >> $config_host_mak
@@ -3867,9 +3875,6 @@ echo "libs_softmmu=$libs_softmmu" >> $config_host_mak
 
 echo "ARCH=$ARCH" >> $config_host_mak
 
-if test "$modules" = "yes"; then
-  echo "CONFIG_MODULES=y" >> $config_host_mak
-fi
 if test "$debug_tcg" = "yes" ; then
   echo "CONFIG_DEBUG_TCG=y" >> $config_host_mak
 fi
@@ -3991,6 +3996,10 @@ echo "TARGET_DIRS=$target_list" >> $config_host_mak
 if [ "$docs" = "yes" ] ; then
   echo "BUILD_DOCS=yes" >> $config_host_mak
 fi
+echo "CONFIG_STAMP=`(echo $qemu_version; echo $pkgversion; cat $0) | sha256sum - | cut -f1 -d\ `" >> $config_host_mak
+if test "$modules" = "yes"; then
+  echo "CONFIG_MODULES=y" >> $config_host_mak
+fi
 if test "$sdl" = "yes" ; then
   echo "CONFIG_SDL=y" >> $config_host_mak
   echo "SDL_CFLAGS=$sdl_cflags" >> $config_host_mak
diff --git a/include/qemu/module.h b/include/qemu/module.h
index c4ccd57..d6da64f 100644
--- a/include/qemu/module.h
+++ b/include/qemu/module.h
@@ -14,11 +14,26 @@
 #ifndef QEMU_MODULE_H
 #define QEMU_MODULE_H
 
+#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 +49,7 @@ 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);
 
diff --git a/module-common.c b/module-common.c
new file mode 100644
index 0000000..50c6750
--- /dev/null
+++ b/module-common.c
@@ -0,0 +1,10 @@
+#include "config-host.h"
+#include "qemu/module.h"
+
+void qemu_module_dummy(void)
+{
+}
+
+void DSO_STAMP_FUN(void)
+{
+}
diff --git a/rules.mak b/rules.mak
index fb3482b..b3f7a85 100644
--- a/rules.mak
+++ b/rules.mak
@@ -69,9 +69,9 @@ endif
 %.o: %.dtrace
 	$(call quiet-command,dtrace -o $@ -G -s $<, "  GEN   $(TARGET_DIR)$@")
 
-%$(DSOSUF): QEMU_CFLAGS += -fPIC
+%$(DSOSUF): QEMU_CFLAGS += -fPIC -DBUILD_DSO
 %$(DSOSUF): LDFLAGS += $(LDFLAGS_SHARED)
-%$(DSOSUF): %.mo libqemustub.a
+%$(DSOSUF): %.mo libqemustub.a module-common.o
 	$(call LINK,$^)
 
 .PHONY: modules
@@ -206,7 +206,8 @@ $(foreach o,$(filter %.o,$($1)),
 	$(eval $(patsubst %.o,%.mo,$o)-objs := $o))
 $(foreach o,$(filter %.mo,$($1)),$(eval \
     $o: $($o-objs)))
-$(eval modules-m += $(patsubst %.o,%.mo,$($1)))
+$(eval t := $(patsubst %.o,%.mo,$($1)))
+$(foreach o,$t,$(eval modules-m += $o)))
 endef
 
 define unnest-vars
diff --git a/scripts/create_config b/scripts/create_config
index b1adbf5..d7ba61d 100755
--- a/scripts/create_config
+++ b/scripts/create_config
@@ -26,6 +26,17 @@ case $line in
     # save for the next definitions
     prefix=${line#*=}
     ;;
+ moddir=*)
+    eval "moddir=\"${line#*=}\""
+    echo "#define CONFIG_MODDIR \"$moddir\""
+    ;;
+ CONFIG_STAMP=*)
+    echo "#define DSO_STAMP_FUN qemu_stamp_${line#*=}"
+    echo "#define DSO_STAMP_FUN_STR \"qemu_stamp_${line#*=}\""
+    ;;
+ CONFIG_MODULES=*)
+    echo "#define CONFIG_MODULES \"${line#*=}\""
+    ;;
  CONFIG_AUDIO_DRIVERS=*)
     drivers=${line#*=}
     echo "#define CONFIG_AUDIO_DRIVERS \\"
@@ -104,6 +115,9 @@ case $line in
     value=${line#*=}
     echo "#define $name $value"
     ;;
+ DSOSUF=*)
+    echo "#define HOST_DSOSUF \"${line#*=}\""
+    ;;
 esac
 
 done # read
diff --git a/util/module.c b/util/module.c
index 7acc33d..c4115be 100644
--- a/util/module.c
+++ b/util/module.c
@@ -13,6 +13,7 @@
  * GNU GPL, version 2 or (at your option) any later version.
  */
 
+#include <gmodule.h>
 #include "qemu-common.h"
 #include "qemu/queue.h"
 #include "qemu/module.h"
@@ -21,13 +22,16 @@ typedef struct ModuleEntry
 {
     void (*init)(void);
     QTAILQ_ENTRY(ModuleEntry) node;
+    module_init_type type;
 } ModuleEntry;
 
 typedef QTAILQ_HEAD(, ModuleEntry) ModuleTypeList;
 
 static ModuleTypeList init_type_list[MODULE_INIT_MAX];
 
-static void init_types(void)
+static ModuleTypeList dso_init_list;
+
+static void init_lists(void)
 {
     static int inited;
     int i;
@@ -40,6 +44,8 @@ static void init_types(void)
         QTAILQ_INIT(&init_type_list[i]);
     }
 
+    QTAILQ_INIT(&dso_init_list);
+
     inited = 1;
 }
 
@@ -48,7 +54,7 @@ static ModuleTypeList *find_type(module_init_type type)
 {
     ModuleTypeList *l;
 
-    init_types();
+    init_lists();
 
     l = &init_type_list[type];
 
@@ -62,20 +68,117 @@ void register_module_init(void (*fn)(void), module_init_type type)
 
     e = g_malloc0(sizeof(*e));
     e->init = fn;
+    e->type = type;
 
     l = find_type(type);
 
     QTAILQ_INSERT_TAIL(l, e, node);
 }
 
+void register_dso_module_init(void (*fn)(void), module_init_type type)
+{
+    ModuleEntry *e;
+
+    init_lists();
+
+    e = g_malloc0(sizeof(*e));
+    e->init = fn;
+    e->type = type;
+
+    QTAILQ_INSERT_TAIL(&dso_init_list, e, node);
+}
+
+static void module_load(module_init_type type);
+
 void module_call_init(module_init_type type)
 {
     ModuleTypeList *l;
     ModuleEntry *e;
 
+    module_load(type);
     l = find_type(type);
 
     QTAILQ_FOREACH(e, l, node) {
         e->init();
     }
 }
+
+#ifdef CONFIG_MODULES
+static void module_load_file(const char *fname)
+{
+    GModule *g_module;
+    void (*sym)(void);
+    const char *dsosuf = HOST_DSOSUF;
+    int len = strlen(fname);
+    int suf_len = strlen(dsosuf);
+    ModuleEntry *e, *next;
+
+    if (len <= suf_len || strcmp(&fname[len - suf_len], dsosuf)) {
+        /* wrong suffix */
+        return;
+    }
+    if (access(fname, F_OK)) {
+        return;
+    }
+
+    assert(QTAILQ_EMPTY(&dso_init_list));
+
+    g_module = g_module_open(fname, G_MODULE_BIND_LAZY | G_MODULE_BIND_LOCAL);
+    if (!g_module) {
+        fprintf(stderr, "Failed to load module: %s\n",
+                g_module_error());
+        return;
+    }
+    if (!g_module_symbol(g_module, DSO_STAMP_FUN_STR, (gpointer *)&sym)) {
+        fprintf(stderr, "Failed to initialize module: %s\n",
+                fname);
+        /* Print some info if this is a QEMU module (but from different build),
+         * this will make debugging user problems easier. */
+        if (g_module_symbol(g_module, "qemu_module_dummy", (gpointer *)&sym)) {
+            fprintf(stderr,
+                    "Note: only modules from the same build can be loaded.\n");
+        }
+        g_module_close(g_module);
+    } else {
+        QTAILQ_FOREACH(e, &dso_init_list, node) {
+            register_module_init(e->init, e->type);
+        }
+    }
+
+    QTAILQ_FOREACH_SAFE(e, &dso_init_list, node, next) {
+        QTAILQ_REMOVE(&dso_init_list, e, node);
+        g_free(e);
+    }
+}
+#endif
+
+void module_load(module_init_type type)
+{
+#ifdef CONFIG_MODULES
+    char *fname = NULL;
+    const char **mp;
+    static const char *block_modules[] = {
+        CONFIG_BLOCK_MODULES
+    };
+
+    if (!g_module_supported()) {
+        return;
+    }
+
+    switch (type) {
+    case MODULE_INIT_BLOCK:
+        mp = block_modules;
+        break;
+    /* no other types have dynamic modules for now*/
+    default:
+        return;
+    }
+
+    for ( ; *mp; mp++) {
+        fname = g_strdup_printf("%s/%s%s", CONFIG_MODDIR, *mp, HOST_DSOSUF);
+        module_load_file(fname);
+        g_free(fname);
+    }
+
+#endif
+}
-- 
1.8.5.2