diff options
Diffstat (limited to 'lib/module.c')
| -rw-r--r-- | lib/module.c | 148 |
1 files changed, 148 insertions, 0 deletions
diff --git a/lib/module.c b/lib/module.c new file mode 100644 index 0000000..83ae773 --- /dev/null +++ b/lib/module.c @@ -0,0 +1,148 @@ +/* Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz> + * SPDX-License-Identifier: GPL-3.0-or-later + */ + +#include <stdlib.h> +#include <dlfcn.h> +#include <contrib/cleanup.h> + +#include "kresconfig.h" +#include "lib/defines.h" +#include "lib/utils.h" +#include "lib/module.h" + + +/* List of embedded modules. These aren't (un)loaded. */ +int iterate_init(struct kr_module *self); +int validate_init(struct kr_module *self); +int cache_init(struct kr_module *self); +kr_module_init_cb kr_module_get_embedded(const char *name) +{ + if (strcmp(name, "iterate") == 0) + return iterate_init; + if (strcmp(name, "validate") == 0) + return validate_init; + if (strcmp(name, "cache") == 0) + return cache_init; + return NULL; +} + +/** Load prefixed symbol. */ +static void *load_symbol(void *lib, const char *prefix, const char *name) +{ + auto_free char *symbol = kr_strcatdup(2, prefix, name); + return dlsym(lib, symbol); +} + +static int load_library(struct kr_module *module, const char *name, const char *path) +{ + if (kr_fails_assert(module && name && path)) + return kr_error(EINVAL); + /* Absolute or relative path (then only library search path is used). */ + auto_free char *lib_path = kr_strcatdup(4, path, "/", name, LIBEXT); + if (lib_path == NULL) { + return kr_error(ENOMEM); + } + + /* Workaround for buggy _fini/__attribute__((destructor)) and dlclose(), + * this keeps the library mapped until the program finishes though. */ + module->lib = dlopen(lib_path, RTLD_NOW | RTLD_NODELETE); + if (module->lib) { + return kr_ok(); + } + + return kr_error(ENOENT); +} + +/** Load C module symbols. */ +static int load_sym_c(struct kr_module *module, uint32_t api_required) +{ + module->init = kr_module_get_embedded(module->name); + if (module->init) { + return kr_ok(); + } + #pragma GCC diagnostic push + #pragma GCC diagnostic ignored "-Wpedantic" /* casts after load_symbol() */ + /* Check if it's embedded first */ + /* Load dynamic library module */ + auto_free char *m_prefix = kr_strcatdup(2, module->name, "_"); + + /* Check ABI version, return error on mismatch. */ + module_api_cb *api = load_symbol(module->lib, m_prefix, "api"); + if (api == NULL) { + return kr_error(ENOENT); + } + if (api() != api_required) { + return kr_error(ENOTSUP); + } + + /* Load ABI by symbol names. */ + #define ML(symname) module->symname = \ + load_symbol(module->lib, m_prefix, #symname) + ML(init); + ML(deinit); + ML(config); + #undef ML + if (load_symbol(module->lib, m_prefix, "layer") + || load_symbol(module->lib, m_prefix, "props")) { + /* In case someone re-compiled against new kresd + * but haven't actually changed the symbols. */ + kr_log_error(SYSTEM, "module %s requires upgrade. Please refer to " + "https://knot-resolver.readthedocs.io/en/stable/upgrading.html", + module->name); + return kr_error(ENOTSUP); + } + + return kr_ok(); + #pragma GCC diagnostic pop +} + +int kr_module_load(struct kr_module *module, const char *name, const char *path) +{ + if (module == NULL || name == NULL) { + return kr_error(EINVAL); + } + + /* Initialize, keep userdata */ + void *data = module->data; + memset(module, 0, sizeof(struct kr_module)); + module->data = data; + module->name = strdup(name); + if (module->name == NULL) { + return kr_error(ENOMEM); + } + + /* Search for module library. */ + if (!path || load_library(module, name, path) != 0) { + module->lib = RTLD_DEFAULT; + } + + /* Try to load module ABI. */ + int ret = load_sym_c(module, KR_MODULE_API); + if (ret == 0 && module->init) { + ret = module->init(module); + } + if (ret != 0) { + kr_module_unload(module); + } + + return ret; +} + +void kr_module_unload(struct kr_module *module) +{ + if (module == NULL) { + return; + } + + if (module->deinit) { + module->deinit(module); + } + + if (module->lib && module->lib != RTLD_DEFAULT) { + dlclose(module->lib); + } + + free(module->name); + memset(module, 0, sizeof(struct kr_module)); +} |