/*
* linux/fs/namei.c
*
* (C) 1991 Linus Torvalds
*/
/*
* Some corrections by tytso.
*/
#include <linux/sched.h>
#include <linux/kernel.h>
#include <asm/segment.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <const.h>
#include <sys/stat.h>
#define ACC_MODE(x) ("\004\002\006\377"[(x)&O_ACCMODE])
/*
* comment out this line if you want names > NAME_LEN chars to be
* truncated. Else they will be disallowed.
*/
/* #define NO_TRUNCATE */
#define MAY_EXEC 1
#define MAY_WRITE 2
#define MAY_READ 4
/*
* permission()
*
* is used to check for read/write/execute permissions on a file.
* I don't know if we should look at just the euid or both euid and
* uid, but that should be easily changed.
*/
static int permission(struct m_inode * inode,int mask)
{
int mode = inode->i_mode;
/* special case: not even root can read/write a deleted file */
if (inode->i_dev && !inode->i_nlinks)
return 0;
else if (current->euid==inode->i_uid)
mode >>= 6;
else if (current->egid==inode->i_gid)
mode >>= 3;
if (((mode & mask & 0007) == mask) || suser())
return 1;
return 0;
}
/*
* ok, we cannot use strncmp, as the name is not in our data space.
* Thus we'll have to use match. No big problem. Match also makes
* some sanity tests.
*
* NOTE! unlike strncmp, match returns 1 for success, 0 for failure.
*/
static int match(int len,const char * name,struct dir_entry * de)
{
register int same __asm__("ax");
if (!de || !de->inode || len > NAME_LEN)
return 0;
if (len < NAME_LEN && de->name[len])
return 0;
__asm__("cld\n\t"
"fs ; repe ; cmpsb\n\t"
"setz %%al"
:"=a" (same)
:"0" (0),"S" ((long) name),"D" ((long) de->name),"c" (len)
:"cx","di","si");
return same;
}
/*
* find_entry()
*
* finds an entry in the specified directory with the wanted name. It
* returns the cache buffer in which the entry was found, and the entry
* itself (as a parameter - res_dir). It does NOT read the inode of the
* entry - you'll have to do that yourself if you want to.
*
* This also takes care of the few special cases due to '..'-traversal
* over a pseudo-root and a mount point.
*/
static struct buffer_head * find_entry(struct m_inode ** dir,
const char * name, int namelen, struct dir_entry ** res_dir)
{
int entries;
int block,i;
struct buffer_head * bh;
struct dir_entry * de;
struct super_block * sb;
#ifdef NO_TRUNCATE
if (namelen > NAME_LEN)
return NULL;
#else
if (namelen > NAME_LEN)
namelen = NAME_LEN;
#endif
entries = (*dir)->i_size / (sizeof (struct dir_entry));
*res_dir = NULL;
if (!namelen)
return NULL;
/* check for '..', as we might have to do some "magic" for it */
if (namelen==2 && get_fs_byte(name)=='.' && get_fs_byte(name+1)=='.') {
/* '..' in a pseudo-root results in a faked '.' (just change namelen) */
if ((*dir) == current->root)
namelen=1;
else if ((*dir)->i_num == ROOT_INO) {
/* '..' over a mount-point results in 'dir' being exchanged for the mounted
directory-inode. NOTE! We set mounted, so that we can iput the new dir */
sb=get_super((*dir)->i_dev);
if (sb->s_imount) {
iput(*dir);
(*dir)=sb->s_imount;
(*dir)->i_count++;
}
}
}
if (!(block = (*dir)->i_zone[0]))
return NULL;
if (!(bh = bread((*dir)->i_dev,block)))
return NULL;
i = 0;
de = (struct dir_entry *) bh->b_data;
while (i < entries) {
if ((char *)de >= BLOCK_SIZE+bh->b_data) {
brelse(bh);
bh = NULL;
if (!(block = bmap(*dir,i/DIR_ENTRIES_PER_BLOCK)) ||
!(bh = bread((*dir)->i_dev,block))) {
i += DIR_ENTRIES_PER_BLOCK;
continue;
}
de = (struct dir_entry *) bh->b_data;
}
if (match(namelen,name,de)) {
*res_dir = de;
return bh;
}
de++;
i++;
}
brelse(bh);
return NULL;
}
/*
* add_entry()
*
* adds a file entry to the specified directory, using the same
* semantics as find_entry(). It returns NULL if it failed.
*
* NOTE!! The inode part of 'de' is left at 0 - which means you
* may not sleep between calling this and putting something into
* the entry, as someone else might have used it while you slept.
*/
static struct buffer_head * add_entry(struct m_inode * dir,
const char * name, int namelen, struct dir_entry ** res_dir)
{
int block,i;
struct buffer_head * bh;
struct dir_entry * de;
*res_dir = NULL;
#ifdef NO_TRUNCATE
if (namelen > NAME_LEN)
return NULL;
#else
if (namelen > NAME_LEN)
namelen = NAME_LEN;
#endif
if (!namelen)
return NULL;
if (!(block = dir->i_zone[0]))
return NULL;
if (!(bh = bread(dir->i_dev,block)))
return NULL;
i = 0;
de = (struct dir_entry *) bh->b_data;
while (1) {
if ((char *)de >= BLOCK_SIZE+bh->b_data) {
brelse(bh);
bh = NULL;
block = create_block(dir,i/DIR_ENTRIES_PER_BLOCK);
if (!block)
return NULL;
if (!(bh = bread(dir->i_dev,block))) {
i += DIR_ENTRIES_PER_BLOCK;
continue;
}
de = (struct dir_entry *) bh->b_data;
}
if (i*sizeof(struct dir_entry) >= dir->i_size) {
de->inode=0;
dir->i_size = (i+1)*sizeof(struct dir_entry);
dir->i_dirt = 1;
dir->i_ctime = CURRENT_TIME;
}
if (!de->inode) {
dir->i_mtime = CURRENT_TIME;
for (i=0; i < NAME_LEN ; i++)
de->name[i]=(i<namelen)?get_fs_byte(name+i):0;
bh->b_dirt = 1;
*res_dir = de;
return bh;
}
de++;
i++;
}
brelse(bh);
return NULL;
}
/*
* get_dir()
*
* Getdir traverses the pathname until it hits the topmost directory.
* It returns NULL on failure.
*/
static struct m_inode * get_dir(const char * pathname)
{
char c;
const char * thisname;
struct m_inode * inode;
struct buffer_head * bh;
int namelen,inr,idev;
struct dir_entry * de;
if (!current->root || !current->root->i_count)
panic("No root inode");
if (!current->pwd || !current->pwd->i_count)
panic("No cwd inode");
if ((c=get_fs_byte(pathname))=='/') {
inode = current->root;
pathname++;
} else if (c)
inode = current->pwd;
else
return NULL; /* empty name is bad */
inode->i_count++;
while (1) {
thisname = pathname;
if (!S_ISDIR(inode->i_mode) || !permission(inode,MAY_EXEC)) {
iput(inode);
return NULL;
}
for(namelen=0;(c=get_fs_byte(pathname++))&&(c!='/');namelen++)
/* nothing */ ;
if (!c)
return inode;
if (!(bh = find_entry(&inode,thisname,namelen,&de))) {
iput(inode);
return NULL;
}
inr = de->inode;
idev = inode->i_dev;
brelse(bh);
iput(inode);
if (!(inode = iget(idev,inr)))
return NULL;
}
}
/*
* dir_namei()
*
* dir_namei() returns the inode of the directory of the
* specified name, and the name within that directory.
*/
static struct m_inode * dir_namei(const char * pathname,
int * namelen, const char ** name)
{
char c;
const char * basename;
struct m_inode * dir;
if (!(dir = get_dir(pathname)))
return NULL;
basename = pathname;
while (c=get_fs_byte(pathname++))
if (c=='/')
basename=pathname;
*namelen = pathname-basename-1;
*name = basename;
return dir;
}
/*
* namei()
*
* is used by most simple commands to get the inode of a specified name.
* Open, link etc use their own routines, but this is enough for things
* like 'chmod' etc.
*/
struct m_inode * namei(const char * pathname)
{
const char * basename;
int inr,dev,namelen;
struct m_inode * dir;
struct buffer_head * bh;
struct dir_entry * de;
if (!(dir = dir_namei(pathname,&namelen,&basename)))
return NULL;
if (!namelen) /* special case: '/usr/' etc */
return dir;
bh = find_entry(&dir,basename,namelen,&de);
if (!bh) {
iput(dir);
return NULL;
}
inr = de->inode;
dev = dir->i_dev;
brelse(bh);
iput(dir);
dir=iget(dev,inr);
if (dir) {
dir->i_atime=CURRENT_TIME;
dir->i_dirt=1;
}
return dir;
}
/*
* open_namei()
*
* namei for open - this is in fact almost the whole open-routine.
*/
int open_namei(const char * pathname, int flag, int mode,
struct m_inode ** res_inode)
{
const char * basename;
int inr,dev,namelen;
struct m_inode * dir, *inode;
struct buffer_head * bh;
struct dir_entry * de;
if ((flag & O_TRUNC) && !(flag & O_
没有合适的资源?快使用搜索试试~ 我知道了~
资源推荐
资源详情
资源评论
收起资源包目录
基于 Docker/Qemu/Bochs 的极速 Linux 0.11 内核学习和开发环境 (534个子文件)
libncurses.so.5 146KB
libform.so.5 72KB
libmenu.so.5 43KB
libpanel.so.5 22KB
libncurses.so.5.9 146KB
libform.so.5.9 72KB
libmenu.so.5.9 43KB
libpanel.so.5.9 22KB
ar 2KB
bios.bin 128KB
vgabios.bin 38KB
vgabios-cirrus.bin 35KB
bochs 1.77MB
bochs-debugger 2MB
.boot_gdbinit 415B
bootlace 2KB
bochsrc-hd.bxrc 439B
bochsrc-fda.bxrc 387B
bochsrc-fdb.bxrc 387B
namei.c 16KB
namei.c 16KB
namei.c 16KB
namei.c 16KB
laceup.c 14KB
console.c 14KB
console.c 14KB
console.c 14KB
console.c 14KB
floppy.c 11KB
floppy.c 11KB
floppy.c 11KB
floppy.c 11KB
memory.c 11KB
memory.c 11KB
memory.c 11KB
memory.c 11KB
exec.c 9KB
exec.c 9KB
exec.c 9KB
exec.c 9KB
buffer.c 9KB
buffer.c 9KB
buffer.c 9KB
buffer.c 9KB
sched.c 8KB
sched.c 8KB
sched.c 8KB
sched.c 8KB
hd.c 8KB
hd.c 8KB
hd.c 8KB
hd.c 8KB
tty_io.c 7KB
tty_io.c 7KB
tty_io.c 7KB
tty_io.c 7KB
malloc.c 7KB
malloc.c 7KB
malloc.c 7KB
malloc.c 7KB
inode.c 7KB
inode.c 7KB
inode.c 7KB
inode.c 7KB
super.c 5KB
super.c 5KB
super.c 5KB
super.c 5KB
main.c 5KB
main.c 5KB
main.c 5KB
main.c 5KB
tty_ioctl.c 5KB
tty_ioctl.c 5KB
tty_ioctl.c 5KB
tty_ioctl.c 5KB
traps.c 5KB
traps.c 5KB
traps.c 5KB
traps.c 5KB
vsprintf.c 5KB
vsprintf.c 5KB
vsprintf.c 5KB
vsprintf.c 5KB
build.c 4KB
build.c 4KB
build.c 4KB
sys.c 4KB
sys.c 4KB
open.c 4KB
open.c 4KB
open.c 4KB
open.c 4KB
exit.c 4KB
exit.c 4KB
exit.c 4KB
exit.c 4KB
bitmap.c 4KB
bitmap.c 4KB
bitmap.c 4KB
共 534 条
- 1
- 2
- 3
- 4
- 5
- 6
资源评论
Java程序员-张凯
- 粉丝: 1w+
- 资源: 6649
上传资源 快速赚钱
- 我的内容管理 展开
- 我的资源 快来上传第一个资源
- 我的收益 登录查看自己的收益
- 我的积分 登录查看自己的积分
- 我的C币 登录后查看C币余额
- 我的收藏
- 我的下载
- 下载帮助
安全验证
文档复制为VIP权益,开通VIP直接复制
信息提交成功