/*
* 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_
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linux源码.zip (135个子文件)
bootsect 544B
namei.c 16KB
console.c 14KB
floppy.c 11KB
memory.c 11KB
exec.c 9KB
buffer.c 9KB
sched.c 8KB
hd.c 8KB
tty_io.c 7KB
malloc.c 7KB
inode.c 7KB
super.c 5KB
main.c 5KB
tty_ioctl.c 5KB
traps.c 5KB
vsprintf.c 5KB
build.c 4KB
open.c 4KB
exit.c 4KB
bitmap.c 4KB
sys.c 4KB
fork.c 4KB
ll_rw_blk.c 3KB
read_write.c 3KB
ramdisk.c 3KB
signal.c 3KB
pipe.c 2KB
char_dev.c 2KB
file_dev.c 2KB
mktime.c 1KB
fcntl.c 1KB
block_dev.c 1KB
serial.c 1KB
ctype.c 1KB
stat.c 1KB
truncate.c 1KB
math_emulate.c 1023B
ioctl.c 977B
printk.c 734B
panic.c 448B
open.c 389B
wait.c 253B
_exit.c 198B
string.c 177B
execve.c 170B
write.c 160B
close.c 131B
setsid.c 128B
dup.c 127B
file_table.c 122B
errno.c 73B
string.h 7KB
unistd.h 6KB
a.out.h 6KB
sched.h 6KB
fs.h 5KB
termios.h 5KB
blk.h 3KB
sys.h 3KB
fdreg.h 2KB
tty.h 2KB
hdreg.h 2KB
signal.h 2KB
system.h 2KB
segment.h 1KB
fcntl.h 1KB
stat.h 1KB
config.h 1KB
errno.h 1KB
ctype.h 1KB
types.h 805B
stdarg.h 780B
kernel.h 734B
time.h 734B
wait.h 560B
memory.h 507B
io.h 477B
const.h 321B
head.h 304B
stddef.h 286B
utsname.h 234B
utime.h 225B
mm.h 219B
times.h 200B
linux0.11.IAB 80KB
linux0.11.IAD 1KB
linux0.11.IMB 48KB
linux0.11.IMD 808B
Makefile 5KB
Makefile 3KB
Makefile 3KB
Makefile 3KB
Makefile 2KB
Makefile 2KB
Makefile 936B
Makefile 840B
kernel.o 31KB
head.o 26KB
sched.o 13KB
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