模块信息
- 初始化及其清理函数：<init.h>中的module_init和module_exit宏定义于定义init函数和exit函数
- 导出符号：内核为导出符号提供两个宏：EXPORT_SYMBOL和EXPORT_SYMBOL_GPL。顾明思义，二者分别用于一般的号出符号和只用于GPL兼容代码的导出符号。同样，具目的在于将对应的符号放到模块二进制映象的适当段中。
/* For every exported symbol, place a struct in the __ksymtab section */ //导出符号 #define __EXPORT_SYMBOL(sym, sec) \ extern typeof(sym) sym; \ __CRC_SYMBOL(sym, sec) \ static const char __kstrtab_##sym[] \ __attribute__((section("__ksymtab_strings"), aligned(1))) \ = VMLINUX_SYMBOL_STR(sym); \ extern const struct kernel_symbol __ksymtab_##sym; \ __visible const struct kernel_symbol __ksymtab_##sym \ __used \ __attribute__((section("___ksymtab" sec "+" #sym), unused)) \ = { (unsigned long)&sym, __kstrtab_##sym } #define EXPORT_SYMBOL(sym) \ __EXPORT_SYMBOL(sym, "") #define EXPORT_SYMBOL_GPL(sym) \ __EXPORT_SYMBOL(sym, "_gpl") #define EXPORT_SYMBOL_GPL_FUTURE(sym) \ __EXPORT_SYMBOL(sym, "_gpl_future") #ifdef CONFIG_UNUSED_SYMBOLS #define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused") #define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl") #else #define EXPORT_UNUSED_SYMBOL(sym) #define EXPORT_UNUSED_SYMBOL_GPL(sym) #endif #endif /* __GENKSYMS__ */
- 一般模块信息：模块许可证，开发者和描述，备选名称，基本版本控制
/* Generic info of form tag = "info" */ #define MODULE_INFO(tag, info) __MODULE_INFO(tag, tag, info) /* For userspace: you can also call me... */ #define MODULE_ALIAS(_alias) MODULE_INFO(alias, _alias) /* Soft module dependencies. See man modprobe.d for details. * Example: MODULE_SOFTDEP("pre: module-foo module-bar post: module-baz") */ #define MODULE_SOFTDEP(_softdep) MODULE_INFO(softdep, _softdep) /* * The following license idents are currently accepted as indicating free * software modules * * "GPL" [GNU Public License v2 or later] * "GPL v2" [GNU Public License v2] * "GPL and additional rights" [GNU Public License v2 rights and more] * "Dual BSD/GPL" [GNU Public License v2 * or BSD license choice] * "Dual MIT/GPL" [GNU Public License v2 * or MIT license choice] * "Dual MPL/GPL" [GNU Public License v2 * or Mozilla license choice] * * The following other idents are available * * "Proprietary" [Non free products] * * There are dual licensed components, but when running with Linux it is the * GPL that is relevant so this is a non issue. Similarly LGPL linked with GPL * is a GPL combined work. * * This exists for several reasons * 1. So modinfo can show license info for users wanting to vet their setup * is free * 2. So the community can ignore bug reports including proprietary modules * 3. So vendors can do likewise based on their own policies */ #define MODULE_LICENSE(_license) MODULE_INFO(license, _license) /* * Author(s), use "Name <email>" or just "Name", for multiple * authors use multiple MODULE_AUTHOR() statements/lines. */ #define MODULE_AUTHOR(_author) MODULE_INFO(author, _author) /* What your module does. */ #define MODULE_DESCRIPTION(_description) MODULE_INFO(description, _description) #ifdef MODULE /* Creates an alias so file2alias.c can find device table. */ #define MODULE_DEVICE_TABLE(type, name) \ extern const typeof(name) __mod_##type##__##name##_device_table \ __attribute__ ((unused, alias(__stringify(name)))) #else /* !MODULE */ #define MODULE_DEVICE_TABLE(type, name) #endif
内核与模块存储字符串匹配成功时，模块才能加载。
SMP配置（是否启用）；抢占配置（是否启用）；使用编译器版本；特定于体系结构的常数。
插入模块
init_module系统调用是用户空间和内孩之间用于装载新模块的接口，通过load_module函数将二进制数据传输到内核地址空间中，具体源码如下：
/* Allocate and load the module: note that size of section 0 is always zero, and we rely on this for optional sections. */ //二进制数据使用load_module传输到内核地址空间中，锁有需要的重定位都会完成，所有iny都会解决 //在load_module中创建module实例已近添加到全局的modues链表后，内核内需要调用模块的初始化函数并释放 //初始化数据占用的内存空间 static int load_module(struct load_info *info, const char __user *uargs, int flags) { struct module *mod; long err; char *after_dashes; err = module_sig_check(info); if (err) goto free_copy; err = elf_header_check(info); if (err) goto free_copy; /* Figure out module layout, and allocate all the memory. */ mod = layout_and_allocate(info, flags); if (IS_ERR(mod)) { err = PTR_ERR(mod); goto free_copy; } /* Reserve our place in the list. */ err = add_unformed_module(mod); if (err) goto free_module; #ifdef CONFIG_MODULE_SIG mod->sig_ok = info->sig_ok; if (!mod->sig_ok) { pr_notice_once("%s: module verification failed: signature " "and/or required key missing - tainting " "kernel\n", mod->name); add_taint_module(mod, TAINT_UNSIGNED_MODULE, LOCKDEP_STILL_OK); } #endif /* To avoid stressing percpu allocator, do this once we're unique. */ err = percpu_modalloc(mod, info); if (err) goto unlink_mod; /* Now module is in final location, initialize linked lists, etc. */ err = module_unload_init(mod); if (err) goto unlink_mod; /* Now we've got everything in the final locations, we can * find optional sections. */ err = find_module_sections(mod, info); if (err) goto free_unload; err = check_module_license_and_versions(mod); if (err) goto free_unload; /* Set up MODINFO_ATTR fields */ setup_modinfo(mod, info); /* Fix up syms, so that st_value is a pointer to location. */ err = simplify_symbols(mod, info); if (err < 0) goto free_modinfo; err = apply_relocations(mod, info); if (err < 0) goto free_modinfo; err = post_relocation(mod, info); if (err < 0) goto free_modinfo; flush_module_icache(mod); /* Now copy in args */ mod->args = strndup_user(uargs, ~0UL >> 1); if (IS_ERR(mod->args)) { err = PTR_ERR(mod->args); goto free_arch_cleanup; } dynamic_debug_setup(info->debug, info->num_debug); /* Ftrace init must be called in the MODULE_STATE_UNFORMED state */ ftrace_module_init(mod); /* Finally it's fully formed, ready to start executing. */ err = complete_formation(mod, info); if (err) goto ddebug_cleanup; /* Module is ready to execute: parsing args may do that. */ after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, -32768, 32767, unknown_module_param_cb); if (IS_ERR(after_dashes)) { err = PTR_ERR(after_dashes); goto bug_cleanup; } else if (after_dashes) { pr_warn("%s: parameters '%s' after `--' ignored\n", mod->name, after_dashes); } /* Link in to syfs. */ err = mod_sysfs_setup(mod, info, mod->kp, mod->num_kp); if (err < 0) goto bug_cleanup; /* Get rid of temporary copy. */ free_copy(info); /* Done! */ trace_module_load(mod); return do_init_module(mod); bug_cleanup: /* module_bug_cleanup needs module_mutex protection */ mutex_lock(&module_mutex); module_bug_cleanup(mod); mutex_unlock(&module_mutex); blocking_notifier_call_chain(&module_notify_list, MODULE_STATE_GOING, mod); /* we can't deallocate the module until we clear memory protection */ unset_module_init_ro_nx(mod); unset_module_core_ro_nx(mod); ddebug_cleanup: dynamic_debug_remove(info->debug); synchronize_sched(); kfree(mod->args); free_arch_cleanup: module_arch_cleanup(mod); free_modinfo: free_modinfo(mod); free_unload: module_unload_free(mod); unlink_mod: mutex_lock(&module_mutex); /* Unlink carefully: kallsyms could be walking list. */ list_del_rcu(&mod->list); wake_up_all(&module_wq); /* Wait for RCU synchronizing before releasing mod->list. */ synchronize_rcu(); mutex_unlock(&module_mutex); free_module: /* Free lock-classes; relies on the preceding sync_rcu() */ lockdep_free_key_range(mod->module_core, mod->core_size); module_deallocate(mod, info); free_copy: free_copy(info); return err; }
在实现load_module时会出现异常，内核源代码中该函数：完成所有碰到异常问题，此函数可以完成任务如下：
- 从用户空间复制模块数据到内核地址空间中的一个临时内存位置
- 查找各个段位置
- 确保内核和模块版本控制字符串和struct module的定义匹配问题
- 将存在的各个段分配到其在内存中的最终位置
- 重定位符号并解决引用，链接到模块符号任何版本控制信息的都会注意到
- 处理模块的参数。
删除模块
从内垓移除块比入模块简单得多，系统调delete_module函数来实现移除模块，具体源码如下：
asmlinkage long sys_init_module(void __user *umod, unsigned long len, const char __user *uargs); asmlinkage long sys_delete_module(const char __user *name_user, unsigned int flags);
