[Qemu-devel] [PATCH v8 5/9] module: implement module loading function

[Fam Zheng <famz@redhat.com>]

Added three types of modules:

    typedef enum {
        MODULE_LOAD_BLOCK = 0,
        MODULE_LOAD_UI,
        MODULE_LOAD_NET,
        MODULE_LOAD_MAX,
    } module_load_type;

and their loading function:

    void module_load(module_load_type).

which loads all ".so" files in a subdir under configured ${MODDIR}, e.g.
"/usr/lib/qemu/block". Modules of each type should be loaded before
respective subsystem initialization code.

The init function of dynamic module is no longer with
__attribute__((constructor)) and need to be explicitly called once
loaded. The function name is mangled with per configure fingerprint as:

    init_$(date +%s$$$RANDOM)

Which is known to module_load function: the loading fails if this symbol
is not there. 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>
---
 block.c               |  1 +
 configure             | 29 +++++++++++++------
 include/qemu/module.h | 23 +++++++++++++++
 rules.mak             |  2 +-
 scripts/create_config | 14 ++++++++++
 util/module.c         | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++
 vl.c                  |  2 ++
 7 files changed, 138 insertions(+), 10 deletions(-)

diff --git a/block.c b/block.c
index 26639e8..16ceaaf 100644
--- a/block.c
+++ b/block.c
@@ -4008,6 +4008,7 @@ BlockDriverAIOCB *bdrv_aio_discard(BlockDriverState *bs,
 
 void bdrv_init(void)
 {
+    module_load(MODULE_LOAD_BLOCK);
     module_call_init(MODULE_INIT_BLOCK);
 }
 
diff --git a/configure b/configure
index 5bc7256..3043059 100755
--- a/configure
+++ b/configure
@@ -199,6 +199,7 @@ datadir="\${prefix}/share"
 qemu_docdir="\${prefix}/share/doc/qemu"
 bindir="\${prefix}/bin"
 libdir="\${prefix}/lib"
+moddir="\${prefix}/lib/qemu"
 libexecdir="\${prefix}/libexec"
 includedir="\${prefix}/include"
 sysconfdir="\${prefix}/etc"
@@ -676,6 +677,8 @@ for opt do
   ;;
   --libdir=*) libdir="$optarg"
   ;;
+  --moddir=*) moddir="$optarg"
+  ;;
   --libexecdir=*) libexecdir="$optarg"
   ;;
   --includedir=*) includedir="$optarg"
@@ -1052,6 +1055,7 @@ echo "  --datadir=PATH           install firmware in PATH$confsuffix"
 echo "  --docdir=PATH            install documentation in PATH$confsuffix"
 echo "  --bindir=PATH            install binaries in PATH"
 echo "  --libdir=PATH            install libraries in PATH"
+echo "  --moddir=PATH            install modules in PATH"
 echo "  --sysconfdir=PATH        install config in PATH$confsuffix"
 echo "  --localstatedir=PATH     install local state in PATH (set at runtime on win32)"
 echo "  --with-confsuffix=SUFFIX suffix for QEMU data inside datadir and sysconfdir [$confsuffix]"
@@ -2256,15 +2260,19 @@ 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 required to compile QEMU"
+    fi
+done
+
 
 ##########################################
 # pixman support probe
@@ -3557,6 +3565,7 @@ 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`"
@@ -3680,6 +3689,7 @@ 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" >> $config_host_mak
@@ -3698,6 +3708,7 @@ echo "libs_softmmu=$libs_softmmu" >> $config_host_mak
 
 echo "ARCH=$ARCH" >> $config_host_mak
 
+echo "CONFIG_FINGERPRINT=$(date +%s$$$RANDOM)" >> $config_host_mak
 if test "$modules" = "yes"; then
   echo "CONFIG_MODULES=y" >> $config_host_mak
 fi
diff --git a/include/qemu/module.h b/include/qemu/module.h
index c4ccd57..6458d8f 100644
--- a/include/qemu/module.h
+++ b/include/qemu/module.h
@@ -14,11 +14,25 @@
 #ifndef QEMU_MODULE_H
 #define QEMU_MODULE_H
 
+#ifdef BUILD_DSO
+
+/* For error message, this function is an identification of qemu module */
+void qemu_module_do_init(void (*init)(void));
+
+/* To restrict loading of arbitrary DSO, The init function name is changed per
+ * "./configure" to refuse unknown DSO file */
+void DSO_INIT_FUN(void);
+
+#define module_init(function, type)                                         \
+void qemu_module_do_init(void (*init)(void)) { init(); }                    \
+void DSO_INIT_FUN(void) { qemu_module_do_init(function); }
+#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) {  \
     register_module_init(function, type);                                   \
 }
+#endif
 
 typedef enum {
     MODULE_INIT_BLOCK,
@@ -37,4 +51,13 @@ void register_module_init(void (*fn)(void), module_init_type type);
 
 void module_call_init(module_init_type type);
 
+typedef enum {
+    MODULE_LOAD_BLOCK = 0,
+    MODULE_LOAD_UI,
+    MODULE_LOAD_NET,
+    MODULE_LOAD_MAX,
+} module_load_type;
+
+void module_load(module_load_type type);
+
 #endif
diff --git a/rules.mak b/rules.mak
index 43a502e..0670366 100644
--- a/rules.mak
+++ b/rules.mak
@@ -62,7 +62,7 @@ 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
 	$(call LINK,$^)
diff --git a/scripts/create_config b/scripts/create_config
index b1adbf5..ecc5d4d 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_FINGERPRINT=*)
+    echo "#define DSO_INIT_FUN init_${line#*=}"
+    echo "#define DSO_INIT_FUN_STR \"init_${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..9135c14 100644
--- a/util/module.c
+++ b/util/module.c
@@ -13,6 +13,8 @@
  * GNU GPL, version 2 or (at your option) any later version.
  */
 
+#include <gmodule.h>
+#include <dirent.h>
 #include "qemu-common.h"
 #include "qemu/queue.h"
 #include "qemu/module.h"
@@ -79,3 +81,78 @@ void module_call_init(module_init_type type)
         e->init();
     }
 }
+
+#ifdef CONFIG_MODULES
+static void module_load_file(const char *fname)
+{
+    GModule *g_module;
+    void (*init_fun)(void);
+    const char *dsosuf = HOST_DSOSUF;
+    int len = strlen(fname);
+    int suf_len = strlen(dsosuf);
+
+    if (len <= suf_len || strcmp(&fname[len - suf_len], dsosuf)) {
+        /* wrong suffix */
+        return;
+    }
+    g_module = g_module_open(fname, G_MODULE_BIND_LAZY | G_MODULE_BIND_LOCAL);
+    if (!g_module) {
+        fprintf(stderr, "Failed to open module file %s\n",
+                g_module_error());
+        return;
+    }
+    if (!g_module_symbol(g_module, DSO_INIT_FUN_STR, (gpointer *)&init_fun)) {
+        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_do_init",
+                            (gpointer *)&init_fun)) {
+            fprintf(stderr,
+                    "Note: only modules from the same build can be loaded.\n");
+        }
+        g_module_close(g_module);
+        return;
+    }
+    init_fun();
+}
+#endif
+
+void module_load(module_load_type type)
+{
+#ifdef CONFIG_MODULES
+    const char *path;
+    char *fname = NULL;
+    DIR *dp;
+    struct dirent *ep = NULL;
+
+    if (!g_module_supported()) {
+        return;
+    }
+
+    switch (type) {
+    case MODULE_LOAD_BLOCK:
+        path = CONFIG_MODDIR "/block/";
+        break;
+    case MODULE_LOAD_UI:
+        path = CONFIG_MODDIR "/ui/";
+        break;
+    case MODULE_LOAD_NET:
+        path = CONFIG_MODDIR "/net/";
+        break;
+    default:
+        return;
+    }
+
+    dp = opendir(path);
+    if (!dp) {
+        fprintf(stderr, "Failed to open dir %s\n", path);
+        return;
+    }
+    for (ep = readdir(dp); ep; ep = readdir(dp)) {
+        fname = g_strdup_printf("%s%s", path, ep->d_name);
+        module_load_file(fname);
+        g_free(fname);
+    }
+#endif
+}
diff --git a/vl.c b/vl.c
index b4b119a..659e53a 100644
--- a/vl.c
+++ b/vl.c
@@ -2940,6 +2940,8 @@ int main(int argc, char **argv, char **envp)
 #endif
     }
 
+    module_load(MODULE_LOAD_UI);
+    module_load(MODULE_LOAD_NET);
     module_call_init(MODULE_INIT_QOM);
 
     qemu_add_opts(&qemu_drive_opts);
-- 
1.8.3.1