glibc源码分析之文件的创建与删除

glibc中与文件创建与删除有关的函数有creat,open,unlink,mkdir,rmdir,mknod,symlink,link。

文件类型 创建 删除 普通文件 creat/mknod unlink 目录文件 mkdir rmdir 字符设备文件 mknod unlink 块设备文件 mknod unlink 管道文件 mknod unlink 套接字文件 mknod unlink 符号链接文件 symlink unlink

这些函数都有对应的系统调用，函数对它们进行了封装。

其中unlink,mkdir,rmdir,symlink,link是用脚本生成的。它们生成的.S文件如下：

#define SYSCALL_NAME unlink#define SYSCALL_NARGS 1#define SYSCALL_SYMBOL __unlink#define SYSCALL_CANCELLABLE 0#define SYSCALL_NOERRNO 0#define SYSCALL_ERRVAL 0#include <syscall-template.S>weak_alias (__unlink, unlink)hidden_weak (unlink)

#define SYSCALL_NAME mkdir#define SYSCALL_NARGS 2#define SYSCALL_SYMBOL __mkdir#define SYSCALL_CANCELLABLE 0#define SYSCALL_NOERRNO 0#define SYSCALL_ERRVAL 0#include <syscall-template.S>weak_alias (__mkdir, mkdir)hidden_weak (mkdir)

#define SYSCALL_NAME rmdir#define SYSCALL_NARGS 1#define SYSCALL_SYMBOL __rmdir#define SYSCALL_CANCELLABLE 0#define SYSCALL_NOERRNO 0#define SYSCALL_ERRVAL 0#include <syscall-template.S>weak_alias (__rmdir, rmdir)hidden_weak (rmdir)

#define SYSCALL_NAME symlink#define SYSCALL_NARGS 2#define SYSCALL_SYMBOL __symlink#define SYSCALL_CANCELLABLE 0#define SYSCALL_NOERRNO 0#define SYSCALL_ERRVAL 0#include <syscall-template.S>weak_alias (__symlink, symlink)hidden_weak (symlink)

#define SYSCALL_NAME link#define SYSCALL_NARGS 2#define SYSCALL_SYMBOL __link#define SYSCALL_CANCELLABLE 0#define SYSCALL_NOERRNO 0#define SYSCALL_ERRVAL 0#include <syscall-template.S>weak_alias (__link, link)hidden_weak (link)

creat,open,mknod是.c文件生成。

open函数位于sysdeps/unix/sysv/linux/open.c文件中。

int__libc_open (const char *file, int oflag, ...){  int mode = 0;  if (__OPEN_NEEDS_MODE (oflag))    {      va_list arg;      va_start (arg, oflag);      mode = va_arg (arg, int);      va_end (arg);    }  return SYSCALL_CANCEL (openat, AT_FDCWD, file, oflag, mode);}libc_hidden_def (__libc_open)weak_alias (__libc_open, __open)libc_hidden_weak (__open)weak_alias (__libc_open, open)

open函数调用openat系统调用完成封装。如果需要model参数，则从栈中取出。

creat函数位于sysdeps/unix/sysv/linux/creat.c文件中。

int__creat (const char *file, mode_t mode){  return SYSCALL_CANCEL (creat, file, mode);}weak_alias (__creat, creat)

creat函数调用creat系统调用完成封装。

mknod函数位于io/mknod.c文件中

intattribute_hidden__mknod (const char *path, mode_t mode, dev_t dev){  return __xmknod (_MKNOD_VER, path, mode, &dev);}weak_hidden_alias (__mknod, mknod)

__mknod函数调用了__xmknod 函数，__xmknod 函数位于sysdeps/unix/sysv/linux/xmknod.c文件中。

int__xmknod (int vers, const char *path, mode_t mode, dev_t *dev){  unsigned long long int k_dev;  if (vers != _MKNOD_VER)    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);  /* We must convert the value to dev_t type used by the kernel.  */  k_dev =  (*dev) & ((1ULL << 32) - 1);  if (k_dev != *dev)    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);  return INLINE_SYSCALL (mknod, 3, path, mode, (unsigned int) k_dev);}weak_alias (__xmknod, _xmknod)libc_hidden_def (__xmknod)

__xmknod 调用了mknod系统调用完成封装。