/*所有事件的名称列表*/ static const char *kobject_actions[] = { [KOBJ_ADD] = "add", [KOBJ_REMOVE] = "remove", [KOBJ_CHANGE] = "change", [KOBJ_MOVE] = "move", [KOBJ_ONLINE] = "online", [KOBJ_OFFLINE] = "offline", }; /*用于事件处理的函数列表*/ struct kset_uevent_ops { /*事件过滤器,返回0表示不用向用户空间报告事件*/ int (* const filter)(struct kset *kset, struct kobject *kobj); /*返回子系统的名字*/ const char *(* const name)(struct kset *kset, struct kobject *kobj); /*添加子系统特有的环境变量*/ int (* const uevent)(struct kset *kset, struct kobject *kobj, struct kobj_uevent_env *env); } /*内核表示的环境*/ struct kobj_uevent_env { //环境变量/值数组 char *envp[UEVENT_NUM_ENVP]; //当前环境变量值索引 int envp_idx; //环境数据缓冲区 char buf[UEVENT_BUFFER_SIZE]; //环境数据缓冲区的长度 int buflen; }; /** * kobject_uevent_env - send an uevent with environmental data * * @action: action that is happening * @kobj: struct kobject that the action is happening to * @envp_ext: pointer to environmental data * * Returns 0 if kobject_uevent() is completed with success or the * corresponding error when it fails. */ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action, char *envp_ext[]) { struct kobj_uevent_env *env; //获得事件的名称 const char *action_string = kobject_actions[action]; const char *devpath = NULL; const char *subsystem; struct kobject *top_kobj; struct kset *kset; const struct kset_uevent_ops *uevent_ops; u64 seq; int i = 0; int retval = 0; pr_debug("kobject: '%s' (%p): %s\n", kobject_name(kobj), kobj, __func__); /* search the kset we belong to */ /*向上寻找所属的kset*/ top_kobj = kobj; while (!top_kobj->kset && top_kobj->parent) top_kobj = top_kobj->parent; if (!top_kobj->kset) { pr_debug("kobject: '%s' (%p): %s: attempted to send uevent " "without kset!\n", kobject_name(kobj), kobj, __func__); return -EINVAL; } /*找到了kset获得事件处理列表*/ kset = top_kobj->kset; uevent_ops = kset->uevent_ops; /* skip the event, if uevent_suppress is set*/ /*事件被抑制*/ if (kobj->uevent_suppress) { pr_debug("kobject: '%s' (%p): %s: uevent_suppress " "caused the event to drop!\n", kobject_name(kobj), kobj, __func__); return 0; } /* skip the event, if the filter returns zero. */ /*事件被过滤掉*/ if (uevent_ops && uevent_ops->filter) if (!uevent_ops->filter(kset, kobj)) { pr_debug("kobject: '%s' (%p): %s: filter function " "caused the event to drop!\n", kobject_name(kobj), kobj, __func__); return 0; } /* originating subsystem */ /*获得当前子系统的名字*/ if (uevent_ops && uevent_ops->name) subsystem = uevent_ops->name(kset, kobj); else subsystem = kobject_name(&kset->kobj); /*无法获得子系统的名字*/ if (!subsystem) { pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the " "event to drop!\n", kobject_name(kobj), kobj, __func__); return 0; } /* environment buffer */ env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL); if (!env) return -ENOMEM; /* complete object path */ /*获得kobject的路径*/ devpath = kobject_get_path(kobj, GFP_KERNEL); if (!devpath) { retval = -ENOENT; goto exit; } /* default keys */ /*来,开始添加环境变量/值对*/ retval = add_uevent_var(env, "ACTION=%s", action_string); if (retval) goto exit; retval = add_uevent_var(env, "DEVPATH=%s", devpath); if (retval) goto exit; retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem); if (retval) goto exit; /* keys passed in from the caller */ if (envp_ext) { for (i = 0; envp_ext[i]; i++) { retval = add_uevent_var(env, "%s", envp_ext[i]); if (retval) goto exit; } } /* let the kset specific function add its stuff */ /*添加外部环境变量*/ if (uevent_ops && uevent_ops->uevent) { retval = uevent_ops->uevent(kset, kobj, env); if (retval) { pr_debug("kobject: '%s' (%p): %s: uevent() returned " "%d\n", kobject_name(kobj), kobj, __func__, retval); goto exit; } } /* * Mark "add" and "remove" events in the object to ensure proper * events to userspace during automatic cleanup. If the object did * send an "add" event, "remove" will automatically generated by * the core, if not already done by the caller. */ /*添加标记啊*/ if (action == KOBJ_ADD) kobj->state_add_uevent_sent = 1; else if (action == KOBJ_REMOVE) kobj->state_remove_uevent_sent = 1; /* we will send an event, so request a new sequence number */ /*来一个序列号,正版无忧*/ spin_lock(&sequence_lock); seq = ++uevent_seqnum; spin_unlock(&sequence_lock); retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)seq); if (retval) goto exit; //来,使用netlink机制,广播到到用户空间 #if defined(CONFIG_NET) /* send netlink message */ if (uevent_sock) { struct sk_buff *skb; size_t len; /* allocate message with the maximum possible size */ len = strlen(action_string) + strlen(devpath) + 2; skb = alloc_skb(len + env->buflen, GFP_KERNEL); if (skb) { char *scratch; /* add header */ scratch = skb_put(skb, len); sprintf(scratch, "%s@%s", action_string, devpath); /* copy keys to our continuous event payload buffer */ for (i = 0; i < env->envp_idx; i++) { len = strlen(env->envp[i]) + 1; scratch = skb_put(skb, len); strcpy(scratch, env->envp[i]); } NETLINK_CB(skb).dst_group = 1; retval = netlink_broadcast(uevent_sock, skb, 0, 1, GFP_KERNEL); /* ENOBUFS should be handled in userspace */ if (retval == -ENOBUFS) retval = 0; } else retval = -ENOMEM; } #endif /* call uevent_helper, usually only enabled during early boot */ if (uevent_helper[0]) { char *argv [3]; argv [0] = uevent_helper; argv [1] = (char *)subsystem; argv [2] = NULL; retval = add_uevent_var(env, "HOME=/"); if (retval) goto exit; retval = add_uevent_var(env, "PATH=/sbin:/bin:/usr/sbin:/usr/bin"); if (retval) goto exit; retval = call_usermodehelper(argv[0], argv, env->envp, UMH_WAIT_EXEC); } exit: kfree(devpath); kfree(env); return retval; }