调用mmap系统调用，将文件映射到用户空间，mmap系统调用只是建立这个映射，真正读写文件是由seg_vn段驱动来实现的。seg_vn通过调用保存在struct seg中的vnode的getpage，putpage方法来实现文件读写。\r\n\r\n我现在在做通过重定向read/write系统调用来实现文件的加密解密。但是对于文件的mmap操作就不知道该如何处理了。有没有可能对mmap的page in/out进行处理做如下处理：\r\npage in的时候对getpage取得的数据进行解密处理；\r\n...

一、自己画了个图，不知正确？ 这是我的理解 注意 1.所有的物理内存要使用都要映射到内核空间 2.物理内存划分为页 3.页扩展机制，支持大于4G的物理内存，这时要用到三级分页（pgd 页全局目录page Global Directory，pmd页中间目录 (page Middle Directory)，pte页表条目 (page Table Entry)），不 需支持时，只需将 pmd 定义成“1”，返回两级分页机制 4.page_OFFSET宏代表3G page_SHIFT、PMD_SHIFT、PGD_SHIF...

Another advantage of semaphores is in situations where the developer would need to restrict the number of times an executable can execute or be mapped in memory. Let's see a simple example: #include #include #include #include #include #define KEY 0x100 typedef union semun { int val; struct semid_ds *st; ushort * array; }semun_t; int main() { int semid,count; struct sembuf op; sem...

Understanding the Utility of Semaphores The advantage of semaphores over other synchronization mechanisms is that they can be used to synchronize two related or unrelated processes trying to access the same resource. Related Process The processes are said to be related if the new process is created from within an existing process, which ends up in duplicating the resources of the creating process...

NOTE: System V semaphores are controlled by the user, but can be a problem to the developer is the permissions on the semaphore. The structure that maintains this information is struct semid_ds. struct semid_ds { struct ipc_perm sem_per; /* operation's permission structure */ struct sem * sem_base; /* pointer to first sem in a set */ ushort sem_nsems; /* number of sem in a set */ time...

The IPC_RMID flag here signifies the type of operation that needs to be carried out on the semaphore identified by semid. The following working example uses these concepts: File: sysvsem_demo.c #include #include #include #include //create user defined semun for initializing the semaphores void *Thread1(void *arg) { int semid; semid = (int)arg; //in order to perform the operations on s...

Once a semaphore is created, System V semaphores require that those semaphores that were created in a set be initialized. Creation and initialization of semaphore is not an atomic operation, and initialization needs to be done separately by the user. The function that does this is: int semctl(int semid, int semnum, int cmd, ...); semidThe semaphore identifier.semnumThe n'th semaphore in the s...

http://linux.die.net/man/ 本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u2/86021/showart_1431894.html

Module CosNotification - This module export functions which return QoS and Admin Properties constants. Description To get access to all definitions include necessary hrl files by using: -include_lib("cosNotification/include/*.hrl"). Exports 'EventReliability'() -> string() This function returns the EventReliability QoS identifier 'BestEffort'() -> short() This fun...

sudo apt-get install manpages-dev 本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u2/61800/showart_1133932.html