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, 143 insertions, 2 deletions

diff --git a/util/module.c b/util/module.c
index 7acc33d076..42bc3732c9 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 <stdlib.h>
+#include <gmodule.h>
 #include "qemu-common.h"
 #include "qemu/queue.h"
 #include "qemu/module.h"
@@ -21,13 +23,16 @@ 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 +45,8 @@ static void init_types(void)
         QTAILQ_INIT(&init_type_list[i]);
     }
 
+    QTAILQ_INIT(&dso_init_list);
+
     inited = 1;
 }
 
@@ -48,7 +55,7 @@ static ModuleTypeList *find_type(module_init_type type)
 {
     ModuleTypeList *l;
 
-    init_types();
+    init_lists();
 
     l = &init_type_list[type];
 
@@ -62,20 +69,154 @@ 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 int 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;
+    int ret;
+
+    if (len <= suf_len || strcmp(&fname[len - suf_len], dsosuf)) {
+        /* wrong suffix */
+        ret = -EINVAL;
+        goto out;
+    }
+    if (access(fname, F_OK)) {
+        ret = -ENOENT;
+        goto out;
+    }
+
+    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 open module: %s\n",
+                g_module_error());
+        ret = -EINVAL;
+        goto out;
+    }
+    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);
+        ret = -EINVAL;
+    } else {
+        QTAILQ_FOREACH(e, &dso_init_list, node) {
+            register_module_init(e->init, e->type);
+        }
+        ret = 0;
+    }
+
+    QTAILQ_FOREACH_SAFE(e, &dso_init_list, node, next) {
+        QTAILQ_REMOVE(&dso_init_list, e, node);
+        g_free(e);
+    }
+out:
+    return ret;
+}
+#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
+    };
+    char *exec_dir;
+    char *dirs[3];
+    int i = 0;
+    int ret;
+
+    if (!g_module_supported()) {
+        fprintf(stderr, "Module is not supported by system.\n");
+        return;
+    }
+
+    switch (type) {
+    case MODULE_INIT_BLOCK:
+        mp = block_modules;
+        break;
+    default:
+        /* no other types have dynamic modules for now*/
+        return;
+    }
+
+    exec_dir = qemu_get_exec_dir();
+    dirs[i++] = g_strdup_printf("%s", CONFIG_QEMU_MODDIR);
+    dirs[i++] = g_strdup_printf("%s/..", exec_dir ? : "");
+    dirs[i++] = g_strdup_printf("%s", exec_dir ? : "");
+    assert(i == ARRAY_SIZE(dirs));
+    g_free(exec_dir);
+    exec_dir = NULL;
+
+    for ( ; *mp; mp++) {
+        for (i = 0; i < ARRAY_SIZE(dirs); i++) {
+            fname = g_strdup_printf("%s/%s%s", dirs[i], *mp, HOST_DSOSUF);
+            ret = module_load_file(fname);
+            /* Try loading until loaded a module file */
+            if (!ret) {
+                break;
+            }
+            g_free(fname);
+            fname = NULL;
+        }
+        if (ret == -ENOENT) {
+            fprintf(stderr, "Can't find module: %s\n", *mp);
+        }
+
+        g_free(fname);
+    }
+
+    for (i = 0; i < ARRAY_SIZE(dirs); i++) {
+        g_free(dirs[i]);
+    }
+
+#endif
+}