module: add Error arguments to module_load and module_load_qom

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.

Replace the previous emission of errors via fprintf in _some_ error
conditions with Error and error_report, so as to emit to the appropriate
target.

A memory leak is also fixed as part of the module_load changes.

audio: when attempting to load an audio module, report module load errors.
Note that still for some callers, a single issue may generate multiple
error reports, and this could be improved further.
Regarding the audio code itself, audio_add() seems to ignore errors,
and this should probably be improved.

block: when attempting to load a block module, report module load errors.
For the code paths that already use the Error API, take advantage of those
to report module load errors into the Error parameter.
For the other code paths, we currently emit the error, but this could be
improved further by adding Error parameters to all possible code paths.

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
      (if no CONFIG_MODULE) or exit (if CONFIG_MODULE).

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>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220929093035.4231-4-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 105 insertions, 84 deletions

diff --git a/util/module.c b/util/module.c
index ad89cd50dc..32e263163c 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
@@ -219,34 +209,52 @@ 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);
 
+    search_dir = getenv("QEMU_MODULE_DIR");
+    if (search_dir != NULL) {
+        dirs[n_dirs++] = g_strdup_printf("%s", search_dir);
+    }
+    dirs[n_dirs++] = get_relocated_path(CONFIG_QEMU_MODDIR);
+
+#ifdef CONFIG_MODULE_UPGRADES
+    version_dir = g_strcanon(g_strdup(QEMU_PKGVERSION),
+                             G_CSET_A_2_Z G_CSET_a_2_z G_CSET_DIGITS "+-.~",
+                             '_');
+    dirs[n_dirs++] = g_strdup_printf("/var/run/qemu/%s", version_dir);
+#endif
+    assert(n_dirs <= ARRAY_SIZE(dirs));
+
+    /* 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)) {
-                    return false;
+                    error_setg(errp, "module arch does not match: "
+                        "expected '%s', got '%s'", module_arch, modinfo->arch);
+                    goto out;
                 }
             }
         }
@@ -254,7 +262,11 @@ bool module_load(const char *prefix, const char *lib_name)
             if (strcmp(modinfo->name, module_name) == 0) {
                 /* we depend on other module(s) */
                 for (sl = modinfo->deps; *sl != NULL; sl++) {
-                    module_load("", *sl);
+                    int subrv = module_load("", *sl, errp);
+                    if (subrv <= 0) {
+                        rv = subrv;
+                        goto out;
+                    }
                 }
             } else {
                 for (sl = modinfo->deps; *sl != NULL; sl++) {
@@ -267,58 +279,52 @@ bool module_load(const char *prefix, const char *lib_name)
         }
     }
 
-    search_dir = getenv("QEMU_MODULE_DIR");
-    if (search_dir != NULL) {
-        dirs[n_dirs++] = g_strdup_printf("%s", search_dir);
-    }
-    dirs[n_dirs++] = get_relocated_path(CONFIG_QEMU_MODDIR);
-
-#ifdef CONFIG_MODULE_UPGRADES
-    version_dir = g_strcanon(g_strdup(QEMU_PKGVERSION),
-                             G_CSET_A_2_Z G_CSET_a_2_z G_CSET_DIGITS "+-.~",
-                             '_');
-    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;
+        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 */
 
-    if (!success) {
+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