[PATCH v6 3/5] module: add Error arguments to module_load and module_load_qom

[Claudio Fontana]

improve error handling during module load, by changing:

bool module_load(const char *prefix, const char *lib_name);
void module_load_qom(const char *type);

to:

int module_load(const char *prefix, const char *name, Error **errp);
int module_load_qom(const char *type, Error **errp);

where the return value is:

 -1 on module load error, and errp is set with the error
  0 on module or one of its dependencies are not installed
  1 on module load success
  2 on module load success (module already loaded or built-in)

module_load_qom_one has been introduced in:

commit 28457744c345 ("module: qom module support"), which built on top of
module_load_one, but discarded the bool return value. Restore it.

Adapt all callers to emit errors, or ignore them, or fail hard,
as appropriate in each context.

Some memory leaks also fixed as part of the module_load changes.

audio: when attempting to load an audio module, report module load errors.
block: when attempting to load a block module, report module load errors.
console: when attempting to load a display module, report module load errors.

qdev: when creating a new qdev Device object (DeviceState), report load errors.
      If a module cannot be loaded to create that device, now abort execution.

qom/object.c: when initializing a QOM object, or looking up class_by_name,
              report module load errors.

qtest: when processing the "module_load" qtest command, report errors
       in the load of the module.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
---
 audio/audio.c         |  16 ++--
 block.c               |  21 ++++-
 block/dmg.c           |  12 ++-
 hw/core/qdev.c        |   5 +-
 include/qemu/module.h |  37 +++++++-
 qom/object.c          |  18 +++-
 softmmu/qtest.c       |   8 +-
 ui/console.c          |  18 +++-
 util/module.c         | 211 +++++++++++++++++++++++-------------------
 9 files changed, 223 insertions(+), 123 deletions(-)

diff --git a/audio/audio.c b/audio/audio.c
index 0a682336a0..ea51793843 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -72,20 +72,24 @@ void audio_driver_register(audio_driver *drv)
 audio_driver *audio_driver_lookup(const char *name)
 {
     struct audio_driver *d;
+    Error *local_err = NULL;
+    int rv;
 
     QLIST_FOREACH(d, &audio_drivers, next) {
         if (strcmp(name, d->name) == 0) {
             return d;
         }
     }
-
-    audio_module_load(name);
-    QLIST_FOREACH(d, &audio_drivers, next) {
-        if (strcmp(name, d->name) == 0) {
-            return d;
+    rv = audio_module_load(name, &local_err);
+    if (rv > 0) {
+        QLIST_FOREACH(d, &audio_drivers, next) {
+            if (strcmp(name, d->name) == 0) {
+                return d;
+            }
         }
+    } else if (rv < 0) {
+        error_report_err(local_err);
     }
-
     return NULL;
 }
 
diff --git a/block.c b/block.c
index 72c7f6d47d..0390ece056 100644
--- a/block.c
+++ b/block.c
@@ -464,12 +464,18 @@ BlockDriver *bdrv_find_format(const char *format_name)
     /* The driver isn't registered, maybe we need to load a module */
     for (i = 0; i < (int)ARRAY_SIZE(block_driver_modules); ++i) {
         if (!strcmp(block_driver_modules[i].format_name, format_name)) {
-            block_module_load(block_driver_modules[i].library_name);
+            Error *local_err = NULL;
+            int rv = block_module_load(block_driver_modules[i].library_name,
+                                       &local_err);
+            if (rv > 0) {
+                return bdrv_do_find_format(format_name);
+            } else if (rv < 0) {
+                error_report_err(local_err);
+            }
             break;
         }
     }
-
-    return bdrv_do_find_format(format_name);
+    return NULL;
 }
 
 static int bdrv_format_is_whitelisted(const char *format_name, bool read_only)
@@ -976,12 +982,17 @@ BlockDriver *bdrv_find_protocol(const char *filename,
     for (i = 0; i < (int)ARRAY_SIZE(block_driver_modules); ++i) {
         if (block_driver_modules[i].protocol_name &&
             !strcmp(block_driver_modules[i].protocol_name, protocol)) {
-            block_module_load(block_driver_modules[i].library_name);
+            Error *local_err = NULL;
+            int rv = block_module_load(block_driver_modules[i].library_name, 
&local_err);
+            if (rv > 0) {
+                drv1 = bdrv_do_find_protocol(protocol);
+            } else if (rv < 0) {
+                error_report_err(local_err);
+            }
             break;
         }
     }
 
-    drv1 = bdrv_do_find_protocol(protocol);
     if (!drv1) {
         error_setg(errp, "Unknown protocol '%s'", protocol);
     }
diff --git a/block/dmg.c b/block/dmg.c
index 007b8d9996..a422cf8d5b 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -434,6 +434,7 @@ static int dmg_open(BlockDriverState *bs, QDict *options, 
int flags,
     uint64_t plist_xml_offset, plist_xml_length;
     int64_t offset;
     int ret;
+    Error *local_err = NULL;
 
     ret = bdrv_apply_auto_read_only(bs, NULL, errp);
     if (ret < 0) {
@@ -446,8 +447,15 @@ static int dmg_open(BlockDriverState *bs, QDict *options, 
int flags,
         return -EINVAL;
     }
 
-    block_module_load("dmg-bz2");
-    block_module_load("dmg-lzfse");
+    if (block_module_load("dmg-bz2", &local_err) < 0) {
+        error_report_err(local_err);
+        return -EINVAL;
+    }
+    local_err = NULL;
+    if (block_module_load("dmg-lzfse", &local_err) < 0) {
+        error_report_err(local_err);
+        return -EINVAL;
+    }
 
     s->n_chunks = 0;
     s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 25dfc08468..06a4bce145 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -147,8 +147,9 @@ bool qdev_set_parent_bus(DeviceState *dev, BusState *bus, 
Error **errp)
 
 DeviceState *qdev_new(const char *name)
 {
-    if (!object_class_by_name(name)) {
-        module_load_qom(name);
+    if (!module_object_class_by_name(name)) {
+        error_report("could not find a module for type '%s'", name);
+        abort();
     }
     return DEVICE(object_new(name));
 }
diff --git a/include/qemu/module.h b/include/qemu/module.h
index b7911ce791..c37ce74b16 100644
--- a/include/qemu/module.h
+++ b/include/qemu/module.h
@@ -61,16 +61,43 @@ typedef enum {
 #define fuzz_target_init(function) module_init(function, \
                                                MODULE_INIT_FUZZ_TARGET)
 #define migration_init(function) module_init(function, MODULE_INIT_MIGRATION)
-#define block_module_load(lib) module_load("block-", lib)
-#define ui_module_load(lib) module_load("ui-", lib)
-#define audio_module_load(lib) module_load("audio-", lib)
+#define block_module_load(lib, errp) module_load("block-", lib, errp)
+#define ui_module_load(lib, errp) module_load("ui-", lib, errp)
+#define audio_module_load(lib, errp) module_load("audio-", lib, errp)
 
 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);
-bool module_load(const char *prefix, const char *lib_name);
-void module_load_qom(const char *type);
+
+/*
+ * module_load: attempt to load a module from a set of directories
+ *
+ * directories searched are:
+ * - getenv("QEMU_MODULE_DIR")
+ * - get_relocated_path(CONFIG_QEMU_MODDIR);
+ * - /var/run/qemu/${version_dir}
+ *
+ * prefix:         a subsystem prefix, or the empty string ("audio-", ..., "")
+ * name:           name of the module
+ * errp:           error to set in case the module is found, but load failed.
+ *
+ * Return value:   -1 on error (errp set if not NULL).
+ *                 0 if module or one of its dependencies are not installed,
+ *                 1 if the module is found and loaded,
+ *                 2 if the module is already loaded, or module is built-in.
+ */
+int module_load(const char *prefix, const char *name, Error **errp);
+
+/*
+ * module_load_qom: attempt to load a module to provide a QOM type
+ *
+ * type:           the type to be provided
+ * errp:           error to set.
+ *
+ * Return value:   as per module_load.
+ */
+int module_load_qom(const char *type, Error **errp);
 void module_load_qom_all(void);
 void module_allow_arch(const char *arch);
 
diff --git a/qom/object.c b/qom/object.c
index 4f834f3bf6..35ced55282 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -526,8 +526,13 @@ void object_initialize(void *data, size_t size, const char 
*typename)
 
 #ifdef CONFIG_MODULES
     if (!type) {
-        module_load_qom(typename);
-        type = type_get_by_name(typename);
+        Error *local_err = NULL;
+        int rv = module_load_qom(typename, &local_err);
+        if (rv > 0) {
+            type = type_get_by_name(typename);
+        } else if (rv < 0) {
+            error_report_err(local_err);
+        }
     }
 #endif
     if (!type) {
@@ -1033,8 +1038,13 @@ ObjectClass *module_object_class_by_name(const char 
*typename)
     oc = object_class_by_name(typename);
 #ifdef CONFIG_MODULES
     if (!oc) {
-        module_load_qom(typename);
-        oc = object_class_by_name(typename);
+        Error *local_err = NULL;
+        int rv = module_load_qom(typename, &local_err);
+        if (rv > 0) {
+            oc = object_class_by_name(typename);
+        } else if (rv < 0) {
+            error_report_err(local_err);
+        }
     }
 #endif
     return oc;
diff --git a/softmmu/qtest.c b/softmmu/qtest.c
index fc5b733c63..36e28609ff 100644
--- a/softmmu/qtest.c
+++ b/softmmu/qtest.c
@@ -753,12 +753,18 @@ static void qtest_process_command(CharBackend *chr, gchar 
**words)
         qtest_sendf(chr, "OK %"PRIi64"\n",
                     (int64_t)qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
     } else if (strcmp(words[0], "module_load") == 0) {
+        Error *local_err = NULL;
+        int rv;
         g_assert(words[1] && words[2]);
 
         qtest_send_prefix(chr);
-        if (module_load(words[1], words[2])) {
+        rv = module_load(words[1], words[2], &local_err);
+        if (rv > 0) {
             qtest_sendf(chr, "OK\n");
         } else {
+            if (rv < 0) {
+                error_report_err(local_err);
+            }
             qtest_sendf(chr, "FAIL\n");
         }
     } else if (qtest_enabled() && strcmp(words[0], "clock_set") == 0) {
diff --git a/ui/console.c b/ui/console.c
index 4913c55684..4e53c3c71b 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -2632,7 +2632,11 @@ bool qemu_display_find_default(DisplayOptions *opts)
 
     for (i = 0; i < (int)ARRAY_SIZE(prio); i++) {
         if (dpys[prio[i]] == NULL) {
-            ui_module_load(DisplayType_str(prio[i]));
+            Error *local_err = NULL;
+            int rv = ui_module_load(DisplayType_str(prio[i]), &local_err);
+            if (rv < 0) {
+                error_report_err(local_err);
+            }
         }
         if (dpys[prio[i]] == NULL) {
             continue;
@@ -2650,7 +2654,11 @@ void qemu_display_early_init(DisplayOptions *opts)
         return;
     }
     if (dpys[opts->type] == NULL) {
-        ui_module_load(DisplayType_str(opts->type));
+        Error *local_err = NULL;
+        int rv = ui_module_load(DisplayType_str(opts->type), &local_err);
+        if (rv < 0) {
+            error_report_err(local_err);
+        }
     }
     if (dpys[opts->type] == NULL) {
         error_report("Display '%s' is not available.",
@@ -2680,7 +2688,11 @@ void qemu_display_help(void)
     printf("none\n");
     for (idx = DISPLAY_TYPE_NONE; idx < DISPLAY_TYPE__MAX; idx++) {
         if (!dpys[idx]) {
-            ui_module_load(DisplayType_str(idx));
+            Error *local_err = NULL;
+            int rv = ui_module_load(DisplayType_str(idx), &local_err);
+            if (rv < 0) {
+                error_report_err(local_err);
+            }
         }
         if (dpys[idx]) {
             printf("%s\n",  DisplayType_str(dpys[idx]->type));
diff --git a/util/module.c b/util/module.c
index ad89cd50dc..b67923a986 100644
--- a/util/module.c
+++ b/util/module.c
@@ -21,6 +21,7 @@
 #include "qemu/module.h"
 #include "qemu/cutils.h"
 #include "qemu/config-file.h"
+#include "qapi/error.h"
 #ifdef CONFIG_MODULE_UPGRADES
 #include "qemu-version.h"
 #endif
@@ -144,25 +145,22 @@ static bool module_check_arch(const QemuModinfo *modinfo)
     return true;
 }
 
-static int module_load_file(const char *fname, bool export_symbols)
+/*
+ * module_load_dso: attempt to load an existing dso file
+ *
+ * fname:          full pathname of the file to load
+ * export_symbols: if true, add the symbols to the global name space
+ * errp:           error to set.
+ *
+ * Return value:   true on success, false on error, and errp will be set.
+ */
+static bool module_load_dso(const char *fname, bool export_symbols,
+                            Error **errp)
 {
     GModule *g_module;
     void (*sym)(void);
-    const char *dsosuf = CONFIG_HOST_DSOSUF;
-    int len = strlen(fname);
-    int suf_len = strlen(dsosuf);
     ModuleEntry *e, *next;
-    int ret, flags;
-
-    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;
-    }
+    int flags;
 
     assert(QTAILQ_EMPTY(&dso_init_list));
 
@@ -172,46 +170,38 @@ static int module_load_file(const char *fname, bool 
export_symbols)
     }
     g_module = g_module_open(fname, flags);
     if (!g_module) {
-        fprintf(stderr, "Failed to open module: %s\n",
-                g_module_error());
-        ret = -EINVAL;
-        goto out;
+        error_setg(errp, "failed to open module: %s", g_module_error());
+        return false;
     }
     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. */
+        error_setg(errp, "failed to initialize module: %s", 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");
+            error_append_hint(errp,
+                "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) {
-            e->init();
-            register_module_init(e->init, e->type);
-        }
-        ret = 0;
+        return false;
     }
 
+    QTAILQ_FOREACH(e, &dso_init_list, node) {
+        e->init();
+        register_module_init(e->init, e->type);
+    }
     trace_module_load_module(fname);
     QTAILQ_FOREACH_SAFE(e, &dso_init_list, node, next) {
         QTAILQ_REMOVE(&dso_init_list, e, node);
         g_free(e);
     }
-out:
-    return ret;
+    return true;
 }
-#endif
 
-bool module_load(const char *prefix, const char *lib_name)
+int module_load(const char *prefix, const char *name, Error **errp)
 {
-    bool success = false;
-
-#ifdef CONFIG_MODULES
-    char *fname = NULL;
+    int rv = -1;
 #ifdef CONFIG_MODULE_UPGRADES
     char *version_dir;
 #endif
@@ -219,54 +209,29 @@ bool module_load(const char *prefix, const char *lib_name)
     char *dirs[5];
     char *module_name;
     int i = 0, n_dirs = 0;
-    int ret;
     bool export_symbols = false;
     static GHashTable *loaded_modules;
     const QemuModinfo *modinfo;
     const char **sl;
 
     if (!g_module_supported()) {
-        fprintf(stderr, "Module is not supported by system.\n");
-        return false;
+        error_setg(errp, "%s", "this platform does not support GLib modules");
+        return -1;
     }
 
     if (!loaded_modules) {
         loaded_modules = g_hash_table_new(g_str_hash, g_str_equal);
     }
 
-    module_name = g_strdup_printf("%s%s", prefix, lib_name);
+    /* allocate all resources managed by the out: label here */
+    module_name = g_strdup_printf("%s%s", prefix, name);
 
     if (g_hash_table_contains(loaded_modules, module_name)) {
         g_free(module_name);
-        return true;
+        return 2; /* module already loaded */
     }
     g_hash_table_add(loaded_modules, module_name);
 
-    for (modinfo = module_info; modinfo->name != NULL; modinfo++) {
-        if (modinfo->arch) {
-            if (strcmp(modinfo->name, module_name) == 0) {
-                if (!module_check_arch(modinfo)) {
-                    return false;
-                }
-            }
-        }
-        if (modinfo->deps) {
-            if (strcmp(modinfo->name, module_name) == 0) {
-                /* we depend on other module(s) */
-                for (sl = modinfo->deps; *sl != NULL; sl++) {
-                    module_load("", *sl);
-                }
-            } else {
-                for (sl = modinfo->deps; *sl != NULL; sl++) {
-                    if (strcmp(module_name, *sl) == 0) {
-                        /* another module depends on us */
-                        export_symbols = true;
-                    }
-                }
-            }
-        }
-    }
-
     search_dir = getenv("QEMU_MODULE_DIR");
     if (search_dir != NULL) {
         dirs[n_dirs++] = g_strdup_printf("%s", search_dir);
@@ -279,46 +244,87 @@ bool module_load(const char *prefix, const char *lib_name)
                              '_');
     dirs[n_dirs++] = g_strdup_printf("/var/run/qemu/%s", version_dir);
 #endif
-
     assert(n_dirs <= ARRAY_SIZE(dirs));
 
-    for (i = 0; i < n_dirs; i++) {
-        fname = g_strdup_printf("%s/%s%s",
-                dirs[i], module_name, CONFIG_HOST_DSOSUF);
-        ret = module_load_file(fname, export_symbols);
-        g_free(fname);
-        fname = NULL;
-        /* Try loading until loaded a module file */
-        if (!ret) {
-            success = true;
-            break;
+    /* end of resources managed by the out: label */
+
+    for (modinfo = module_info; modinfo->name != NULL; modinfo++) {
+        if (modinfo->arch) {
+            if (strcmp(modinfo->name, module_name) == 0) {
+                if (!module_check_arch(modinfo)) {
+                    error_setg(errp, "module arch does not match: "
+                        "expected '%s', got '%s'", module_arch, modinfo->arch);
+                    goto out;
+                }
+            }
+        }
+        if (modinfo->deps) {
+            if (strcmp(modinfo->name, module_name) == 0) {
+                /* we depend on other module(s) */
+                for (sl = modinfo->deps; *sl != NULL; sl++) {
+                    int subrv = module_load("", *sl, errp);
+                    if (subrv <= 0) {
+                        rv = subrv;
+                        goto out;
+                    }
+                }
+            } else {
+                for (sl = modinfo->deps; *sl != NULL; sl++) {
+                    if (strcmp(module_name, *sl) == 0) {
+                        /* another module depends on us */
+                        export_symbols = true;
+                    }
+                }
+            }
         }
     }
 
-    if (!success) {
-        g_hash_table_remove(loaded_modules, module_name);
-        g_free(module_name);
+    for (i = 0; i < n_dirs; i++) {
+        char *fname = g_strdup_printf("%s/%s%s",
+                                      dirs[i], module_name, 
CONFIG_HOST_DSOSUF);
+        int ret = access(fname, F_OK);
+        if (ret != 0 && (errno == ENOENT || errno == ENOTDIR)) {
+            /*
+             * if we don't find the module in this dir, try the next one.
+             * If we don't find it in any dir, that can be fine too: user
+             * did not install the module. We will return 0 in this case
+             * with no error set.
+             */
+            g_free(fname);
+            continue;
+        } else if (ret != 0) {
+            /* most common is EACCES here */
+            error_setg_errno(errp, errno, "error trying to access %s", fname);
+        } else if (module_load_dso(fname, export_symbols, errp)) {
+            rv = 1; /* module successfully loaded */
+        }
+        g_free(fname);
+        goto out;
     }
+    rv = 0; /* module not found */
 
+out:
+    if (rv <= 0) {
+        g_hash_table_remove(loaded_modules, module_name);
+    }
+    g_free(module_name);
     for (i = 0; i < n_dirs; i++) {
         g_free(dirs[i]);
     }
-
-#endif
-    return success;
+    return rv;
 }
 
-#ifdef CONFIG_MODULES
-
 static bool module_loaded_qom_all;
 
-void module_load_qom(const char *type)
+int module_load_qom(const char *type, Error **errp)
 {
     const QemuModinfo *modinfo;
     const char **sl;
+    int rv = 0;
 
     if (!type) {
-        return;
+        error_setg(errp, "%s", "type is NULL");
+        return -1;
     }
 
     trace_module_lookup_object_type(type);
@@ -331,15 +337,24 @@ void module_load_qom(const char *type)
         }
         for (sl = modinfo->objs; *sl != NULL; sl++) {
             if (strcmp(type, *sl) == 0) {
-                module_load("", modinfo->name);
+                if (rv > 0) {
+                    error_setg(errp, "multiple modules providing '%s'", type);
+                    return -1;
+                }
+                rv = module_load("", modinfo->name, errp);
+                if (rv < 0) {
+                    return rv;
+                }
             }
         }
     }
+    return rv;
 }
 
 void module_load_qom_all(void)
 {
     const QemuModinfo *modinfo;
+    Error *local_err = NULL;
 
     if (module_loaded_qom_all) {
         return;
@@ -352,7 +367,9 @@ void module_load_qom_all(void)
         if (!module_check_arch(modinfo)) {
             continue;
         }
-        module_load("", modinfo->name);
+        if (module_load("", modinfo->name, &local_err) < 0) {
+            error_report_err(local_err);
+        }
     }
     module_loaded_qom_all = true;
 }
@@ -368,7 +385,10 @@ void qemu_load_module_for_opts(const char *group)
         }
         for (sl = modinfo->opts; *sl != NULL; sl++) {
             if (strcmp(group, *sl) == 0) {
-                module_load("", modinfo->name);
+                Error *local_err = NULL;
+                if (module_load("", modinfo->name, &local_err) < 0) {
+                    error_report_err(local_err);
+                }
             }
         }
     }
@@ -378,7 +398,8 @@ void qemu_load_module_for_opts(const char *group)
 
 void module_allow_arch(const char *arch) {}
 void qemu_load_module_for_opts(const char *group) {}
-void module_load_qom(const char *type) {}
+int module_load(const char *prefix, const char *name, Error **errp) { return 
2; }
+int module_load_qom(const char *type, Error **errp) { return 2; }
 void module_load_qom_all(void) {}
 
 #endif
-- 
2.26.2