Re: [PATCH v4 2/3] module: add Error arguments to module_load_one and module_load_qom_one

[Claudio Fontana]

On 9/8/22 20:30, Claudio Fontana wrote:
> improve error handling during module load, by changing:
> 
> bool module_load_one(const char *prefix, const char *lib_name);
> void module_load_qom_one(const char *type);
> 
> to:
> 
> bool module_load_one(const char *prefix, const char *name, Error **errp);
> bool module_load_qom_one(const char *type, Error **errp);
> 
> 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.
> 
> Signed-off-by: Claudio Fontana <cfontana@suse.de>
> ---
>  audio/audio.c         |   9 ++-
>  block.c               |  15 ++++-
>  block/dmg.c           |  18 +++++-
>  hw/core/qdev.c        |  10 ++-
>  include/qemu/module.h |  38 ++++++++++--
>  qom/object.c          |  18 +++++-
>  softmmu/qtest.c       |   6 +-
>  ui/console.c          |  18 +++++-
>  util/module.c         | 140 ++++++++++++++++++++++++------------------
>  9 files changed, 194 insertions(+), 78 deletions(-)
> 
> diff --git a/audio/audio.c b/audio/audio.c
> index 76b8735b44..cff7464c07 100644
> --- a/audio/audio.c
> +++ b/audio/audio.c
> @@ -72,6 +72,7 @@ void audio_driver_register(audio_driver *drv)
>  audio_driver *audio_driver_lookup(const char *name)
>  {
>      struct audio_driver *d;
> +    Error *local_err = NULL;
>  
>      QLIST_FOREACH(d, &audio_drivers, next) {
>          if (strcmp(name, d->name) == 0) {
> @@ -79,7 +80,13 @@ audio_driver *audio_driver_lookup(const char *name)
>          }
>      }
>  
> -    audio_module_load_one(name);
> +    if (!audio_module_load_one(name, &local_err)) {
> +        if (local_err) {
> +            error_report_err(local_err);
> +        }
> +        return NULL;
> +    }
> +
>      QLIST_FOREACH(d, &audio_drivers, next) {
>          if (strcmp(name, d->name) == 0) {
>              return d;
> diff --git a/block.c b/block.c
> index bc85f46eed..8b610c6d95 100644
> --- a/block.c
> +++ b/block.c
> @@ -464,7 +464,14 @@ 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_one(block_driver_modules[i].library_name);
> +            Error *local_err = NULL;
> +            if (!block_module_load_one(block_driver_modules[i].library_name,
> +                                       &local_err)) {
> +                if (local_err) {
> +                    error_report_err(local_err);
> +                }
> +                return NULL;
> +            }
>              break;
>          }
>      }
> @@ -976,7 +983,11 @@ 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_one(block_driver_modules[i].library_name);
> +            Error *local_err = NULL;
> +            if (!block_module_load_one(block_driver_modules[i].library_name,
> +                                       &local_err) && local_err) {
> +                error_report_err(local_err);
> +            }
>              break;
>          }
>      }
> diff --git a/block/dmg.c b/block/dmg.c
> index 98db18d82a..11d184d39c 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 +447,21 @@ static int dmg_open(BlockDriverState *bs, QDict 
> *options, int flags,
>          return -EINVAL;
>      }
>  
> -    block_module_load_one("dmg-bz2");
> -    block_module_load_one("dmg-lzfse");
> +    if (!block_module_load_one("dmg-bz2", &local_err)) {
> +        if (local_err) {
> +            error_report_err(local_err);
> +            return -EINVAL;
> +        }
> +        warn_report("dmg-bz2 module not present, bz2 decomp unavailable");
> +    }
> +    local_err = NULL;
> +    if (!block_module_load_one("dmg-lzfse", &local_err)) {
> +        if (local_err) {
> +            error_report_err(local_err);
> +            return -EINVAL;
> +        }
> +        warn_report("dmg-lzfse module not present, lzfse decomp 
> unavailable");
> +    }

Hi Richard, Kevin, does this look ok now?

Thanks,

Claudio

>  
>      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 0806d8fcaa..5902c59c94 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -148,7 +148,15 @@ 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_one(name);
> +        Error *local_err = NULL;
> +        if (!module_load_qom_one(name, &local_err)) {
> +            if (local_err) {
> +                error_report_err(local_err);
> +            } else {
> +                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 8c012bbe03..78d4c4de96 100644
> --- a/include/qemu/module.h
> +++ b/include/qemu/module.h
> @@ -61,16 +61,44 @@ 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_one(lib) module_load_one("block-", lib)
> -#define ui_module_load_one(lib) module_load_one("ui-", lib)
> -#define audio_module_load_one(lib) module_load_one("audio-", lib)
> +#define block_module_load_one(lib, errp) module_load_one("block-", lib, errp)
> +#define ui_module_load_one(lib, errp) module_load_one("ui-", lib, errp)
> +#define audio_module_load_one(lib, errp) module_load_one("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_one(const char *prefix, const char *lib_name);
> -void module_load_qom_one(const char *type);
> +
> +/*
> + * module_load_one: 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:   true on success (found and loaded);
> + *                 if module if found, but load failed, errp will be set.
> + *                 if module is not found, errp will not be set.
> + */
> +bool module_load_one(const char *prefix, const char *name, Error **errp);
> +
> +/*
> + * module_load_qom_one: attempt to load a module to provide a QOM type
> + *
> + * type:           the type to be provided
> + * errp:           error to set.
> + *
> + * Return value:   true on success (found and loaded), false on failure.
> + *                 If a module is simply not found for the type,
> + *                 errp will not be set.
> + */
> +bool module_load_qom_one(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 d34608558e..493e5ce231 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -526,8 +526,14 @@ void object_initialize(void *data, size_t size, const 
> char *typename)
>  
>  #ifdef CONFIG_MODULES
>      if (!type) {
> -        module_load_qom_one(typename);
> -        type = type_get_by_name(typename);
> +        Error *local_err = NULL;
> +        if (!module_load_qom_one(typename, &local_err)) {
> +            if (local_err) {
> +                error_report_err(local_err);
> +            }
> +        } else {
> +            type = type_get_by_name(typename);
> +        }
>      }
>  #endif
>      if (!type) {
> @@ -1033,7 +1039,13 @@ ObjectClass *module_object_class_by_name(const char 
> *typename)
>      oc = object_class_by_name(typename);
>  #ifdef CONFIG_MODULES
>      if (!oc) {
> -        module_load_qom_one(typename);
> +        Error *local_err = NULL;
> +        if (!module_load_qom_one(typename, &local_err)) {
> +            if (local_err) {
> +                error_report_err(local_err);
> +            }
> +            return NULL;
> +        }
>          oc = object_class_by_name(typename);
>      }
>  #endif
> diff --git a/softmmu/qtest.c b/softmmu/qtest.c
> index 76eb7bac56..bb83c7aae9 100644
> --- a/softmmu/qtest.c
> +++ b/softmmu/qtest.c
> @@ -753,12 +753,16 @@ 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;
>          g_assert(words[1] && words[2]);
>  
>          qtest_send_prefix(chr);
> -        if (module_load_one(words[1], words[2])) {
> +        if (module_load_one(words[1], words[2], &local_err)) {
>              qtest_sendf(chr, "OK\n");
>          } else {
> +            if (local_err) {
> +                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 765892f84f..34dd206167 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_one(DisplayType_str(prio[i]));
> +            Error *local_err = NULL;
> +            if (!ui_module_load_one(DisplayType_str(prio[i]), &local_err)
> +                && local_err) {
> +                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_one(DisplayType_str(opts->type));
> +        Error *local_err = NULL;
> +        if (!ui_module_load_one(DisplayType_str(opts->type), &local_err)
> +            && local_err) {
> +            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_one(DisplayType_str(idx));
> +            Error *local_err = NULL;
> +            if (!ui_module_load_one(DisplayType_str(idx), &local_err)
> +                && local_err) {
> +                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 8563edd626..90ea8adf7d 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_one(const char *prefix, const char *lib_name)
> +bool module_load_one(const char *prefix, const char *name, Error **errp)
>  {
>      bool success = false;
> -
> -#ifdef CONFIG_MODULES
> -    char *fname = NULL;
>  #ifdef CONFIG_MODULE_UPGRADES
>      char *version_dir;
>  #endif
> @@ -219,14 +209,13 @@ bool module_load_one(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");
> +        error_setg(errp, "%s", "this platform does not support GLib 
> modules");
>          return false;
>      }
>  
> @@ -234,7 +223,7 @@ bool module_load_one(const char *prefix, const char 
> *lib_name)
>          loaded_modules = g_hash_table_new(g_str_hash, g_str_equal);
>      }
>  
> -    module_name = g_strdup_printf("%s%s", prefix, lib_name);
> +    module_name = g_strdup_printf("%s%s", prefix, name);
>  
>      if (g_hash_table_contains(loaded_modules, module_name)) {
>          g_free(module_name);
> @@ -246,6 +235,8 @@ bool module_load_one(const char *prefix, const char 
> *lib_name)
>          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);
>                      return false;
>                  }
>              }
> @@ -254,7 +245,9 @@ bool module_load_one(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_one("", *sl);
> +                    if (!(module_load_one("", *sl, errp))) {
> +                        return false;
> +                    }
>                  }
>              } else {
>                  for (sl = modinfo->deps; *sl != NULL; sl++) {
> @@ -283,16 +276,26 @@ bool module_load_one(const char *prefix, const char 
> *lib_name)
>      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;
> +        char *fname = g_strdup_printf("%s/%s%s",
> +                                      dirs[i], module_name, 
> CONFIG_HOST_DSOSUF);
> +        int ret = access(fname, F_OK);
> +        if (ret != 0) {
> +            if (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 false in this
> +                 * case, with no error set.
> +                 */
> +                continue;
> +            }
> +            /* most common is EACCES here */
> +            error_setg_errno(errp, errno, "error trying to access %s", 
> fname);
>              break;
>          }
> +        success = module_load_dso(fname, export_symbols, errp);
> +        g_free(fname);
> +        break;
>      }
>  
>      if (!success) {
> @@ -304,21 +307,20 @@ bool module_load_one(const char *prefix, const char 
> *lib_name)
>          g_free(dirs[i]);
>      }
>  
> -#endif
>      return success;
>  }
>  
> -#ifdef CONFIG_MODULES
> -
>  static bool module_loaded_qom_all;
>  
> -void module_load_qom_one(const char *type)
> +bool module_load_qom_one(const char *type, Error **errp)
>  {
> +    bool found = false;
>      const QemuModinfo *modinfo;
>      const char **sl;
>  
>      if (!type) {
> -        return;
> +        error_setg(errp, "%s", "type is NULL");
> +        return false;
>      }
>  
>      trace_module_lookup_object_type(type);
> @@ -331,15 +333,26 @@ void module_load_qom_one(const char *type)
>          }
>          for (sl = modinfo->objs; *sl != NULL; sl++) {
>              if (strcmp(type, *sl) == 0) {
> -                module_load_one("", modinfo->name);
> +                if (found) {
> +                    error_setg(errp, "multiple modules providing '%s'", 
> type);
> +                    found = false;
> +                    break;
> +                }
> +                found = module_load_one("", modinfo->name, errp);
> +                if (!found) {
> +                    /* errp optionally set in module_load_one */
> +                    break;
> +                }
>              }
>          }
>      }
> +    return found;
>  }
>  
>  void module_load_qom_all(void)
>  {
>      const QemuModinfo *modinfo;
> +    Error *local_err = NULL;
>  
>      if (module_loaded_qom_all) {
>          return;
> @@ -352,7 +365,9 @@ void module_load_qom_all(void)
>          if (!module_check_arch(modinfo)) {
>              continue;
>          }
> -        module_load_one("", modinfo->name);
> +        if (!module_load_one("", modinfo->name, &local_err) && local_err) {
> +            error_report_err(local_err);
> +        }
>      }
>      module_loaded_qom_all = true;
>  }
> @@ -368,7 +383,11 @@ void qemu_load_module_for_opts(const char *group)
>          }
>          for (sl = modinfo->opts; *sl != NULL; sl++) {
>              if (strcmp(group, *sl) == 0) {
> -                module_load_one("", modinfo->name);
> +                Error *local_err = NULL;
> +                if (!module_load_one("", modinfo->name, &local_err)
> +                    && local_err) {
> +                    error_report_err(local_err);
> +                }
>              }
>          }
>      }
> @@ -378,7 +397,8 @@ 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_one(const char *type) {}
> +bool module_load_one(const char *prefix, const char *name, Error **errp) { 
> return true; }
> +bool module_load_qom_one(const char *type, Error **errp) { return true; }
>  void module_load_qom_all(void) {}
>  
>  #endif