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实现getcwd

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p9ya4sf57 2 years ago
parent b4406cb35e
commit 4aa735850c
1 changed files with 569 additions and 0 deletions
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buffer2.c
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#define __LIBRARY__
/*
* linux/fs/buffer.c
*
* (C) 1991 Linus Torvalds
*/
/*
* 'buffer.c' implements the buffer-cache functions. Race-conditions have
* been avoided by NEVER letting a interrupt change a buffer (except for the
* data, of course), but instead letting the caller do it. NOTE! As interrupts
* can wake up a caller, some cli-sti sequences are needed to check for
* sleep-on-calls. These should be extremely quick, though (I hope).
*/
/*
* NOTE! There is one discordant note here: checking floppies for
* disk change. This is where it fits best, I think, as it should
* invalidate changed floppy-disk-caches.
*/
#include <unistd.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/config.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/segment.h>
#define BUF_MAX 4096
#define DIRBUF 8192
#define MAX_ARG_PAGES 32
#define NAME_LEN 14
extern void put_super(int dev);
extern void invalidate_inodes(int dev);
extern int end;
struct buffer_head * start_buffer = (struct buffer_head *) &end;
struct buffer_head * hash_table[NR_HASH];
static struct buffer_head * free_list;
static struct task_struct * buffer_wait = NULL;
int NR_BUFFERS = 0;
static inline void wait_on_buffer(struct buffer_head * bh)
{
cli();
while (bh->b_lock)
sleep_on(&bh->b_wait);
sti();
}
int sys_sync(void)
{
int i;
struct buffer_head * bh;
sync_inodes(); /* write out inodes into buffers */
bh = start_buffer;
for (i=0 ; i<NR_BUFFERS ; i++,bh++) {
wait_on_buffer(bh);
if (bh->b_dirt)
ll_rw_block(WRITE,bh);
}
return 0;
}
int sync_dev(int dev)
{
int i;
struct buffer_head * bh;
bh = start_buffer;
for (i=0 ; i<NR_BUFFERS ; i++,bh++) {
if (bh->b_dev != dev)
continue;
wait_on_buffer(bh);
if (bh->b_dev == dev && bh->b_dirt)
ll_rw_block(WRITE,bh);
}
sync_inodes();
bh = start_buffer;
for (i=0 ; i<NR_BUFFERS ; i++,bh++) {
if (bh->b_dev != dev)
continue;
wait_on_buffer(bh);
if (bh->b_dev == dev && bh->b_dirt)
ll_rw_block(WRITE,bh);
}
return 0;
}
void inline invalidate_buffers(int dev)
{
int i;
struct buffer_head * bh;
bh = start_buffer;
for (i=0 ; i<NR_BUFFERS ; i++,bh++) {
if (bh->b_dev != dev)
continue;
wait_on_buffer(bh);
if (bh->b_dev == dev)
bh->b_uptodate = bh->b_dirt = 0;
}
}
/*
* This routine checks whether a floppy has been changed, and
* invalidates all buffer-cache-entries in that case. This
* is a relatively slow routine, so we have to try to minimize using
* it. Thus it is called only upon a 'mount' or 'open'. This
* is the best way of combining speed and utility, I think.
* People changing diskettes in the middle of an operation deserve
* to loose :-)
*
* NOTE! Although currently this is only for floppies, the idea is
* that any additional removable block-device will use this routine,
* and that mount/open needn't know that floppies/whatever are
* special.
*/
void check_disk_change(int dev)
{
int i;
if (MAJOR(dev) != 2)
return;
if (!floppy_change(dev & 0x03))
return;
for (i=0 ; i<NR_SUPER ; i++)
if (super_block[i].s_dev == dev)
put_super(super_block[i].s_dev);
invalidate_inodes(dev);
invalidate_buffers(dev);
}
#define _hashfn(dev,block) (((unsigned)(dev^block))%NR_HASH)
#define hash(dev,block) hash_table[_hashfn(dev,block)]
static inline void remove_from_queues(struct buffer_head * bh)
{
/* remove from hash-queue */
if (bh->b_next)
bh->b_next->b_prev = bh->b_prev;
if (bh->b_prev)
bh->b_prev->b_next = bh->b_next;
if (hash(bh->b_dev,bh->b_blocknr) == bh)
hash(bh->b_dev,bh->b_blocknr) = bh->b_next;
/* remove from free list */
if (!(bh->b_prev_free) || !(bh->b_next_free))
panic("Free block list corrupted");
bh->b_prev_free->b_next_free = bh->b_next_free;
bh->b_next_free->b_prev_free = bh->b_prev_free;
if (free_list == bh)
free_list = bh->b_next_free;
}
static inline void insert_into_queues(struct buffer_head * bh)
{
/* put at end of free list */
bh->b_next_free = free_list;
bh->b_prev_free = free_list->b_prev_free;
free_list->b_prev_free->b_next_free = bh;
free_list->b_prev_free = bh;
/* put the buffer in new hash-queue if it has a device */
bh->b_prev = NULL;
bh->b_next = NULL;
if (!bh->b_dev)
return;
bh->b_next = hash(bh->b_dev,bh->b_blocknr);
hash(bh->b_dev,bh->b_blocknr) = bh;
bh->b_next->b_prev = bh;
}
static struct buffer_head * find_buffer(int dev, int block)
{
struct buffer_head * tmp;
for (tmp = hash(dev,block) ; tmp != NULL ; tmp = tmp->b_next)
if (tmp->b_dev==dev && tmp->b_blocknr==block)
return tmp;
return NULL;
}
/*
* Why like this, I hear you say... The reason is race-conditions.
* As we don't lock buffers (unless we are readint them, that is),
* something might happen to it while we sleep (ie a read-error
* will force it bad). This shouldn't really happen currently, but
* the code is ready.
*/
struct buffer_head * get_hash_table(int dev, int block)
{
struct buffer_head * bh;
for (;;) {
if (!(bh=find_buffer(dev,block)))
return NULL;
bh->b_count++;
wait_on_buffer(bh);
if (bh->b_dev == dev && bh->b_blocknr == block)
return bh;
bh->b_count--;
}
}
/*
* Ok, this is getblk, and it isn't very clear, again to hinder
* race-conditions. Most of the code is seldom used, (ie repeating),
* so it should be much more efficient than it looks.
*
* The algoritm is changed: hopefully better, and an elusive bug removed.
*/
#define BADNESS(bh) (((bh)->b_dirt<<1)+(bh)->b_lock)
struct buffer_head * getblk(int dev,int block)
{
struct buffer_head * tmp, * bh;
repeat:
if (bh = get_hash_table(dev,block))
return bh;
tmp = free_list;
do {
if (tmp->b_count)
continue;
if (!bh || BADNESS(tmp)<BADNESS(bh)) {
bh = tmp;
if (!BADNESS(tmp))
break;
}
/* and repeat until we find something good */
} while ((tmp = tmp->b_next_free) != free_list);
if (!bh) {
sleep_on(&buffer_wait);
goto repeat;
}
wait_on_buffer(bh);
if (bh->b_count)
goto repeat;
while (bh->b_dirt) {
sync_dev(bh->b_dev);
wait_on_buffer(bh);
if (bh->b_count)
goto repeat;
}
/* NOTE!! While we slept waiting for this block, somebody else might */
/* already have added "this" block to the cache. check it */
if (find_buffer(dev,block))
goto repeat;
/* OK, FINALLY we know that this buffer is the only one of it's kind, */
/* and that it's unused (b_count=0), unlocked (b_lock=0), and clean */
bh->b_count=1;
bh->b_dirt=0;
bh->b_uptodate=0;
remove_from_queues(bh);
bh->b_dev=dev;
bh->b_blocknr=block;
insert_into_queues(bh);
return bh;
}
void brelse(struct buffer_head * buf)
{
if (!buf)
return;
wait_on_buffer(buf);
if (!(buf->b_count--))
panic("Trying to free free buffer");
wake_up(&buffer_wait);
}
/*
* bread() reads a specified block and returns the buffer that contains
* it. It returns NULL if the block was unreadable.
*/
struct buffer_head * bread(int dev,int block)
{
struct buffer_head * bh;
if (!(bh=getblk(dev,block)))
panic("bread: getblk returned NULL\n");
if (bh->b_uptodate)
return bh;
ll_rw_block(READ,bh);
wait_on_buffer(bh);
if (bh->b_uptodate)
return bh;
brelse(bh);
return NULL;
}
#define COPYBLK(from,to) \
__asm__("cld\n\t" \
"rep\n\t" \
"movsl\n\t" \
::"c" (BLOCK_SIZE/4),"S" (from),"D" (to) \
)
/*
* bread_page reads four buffers into memory at the desired address. It's
* a function of its own, as there is some speed to be got by reading them
* all at the same time, not waiting for one to be read, and then another
* etc.
*/
void bread_page(unsigned long address,int dev,int b[4])
{
struct buffer_head * bh[4];
int i;
for (i=0 ; i<4 ; i++)
if (b[i]) {
if (bh[i] = getblk(dev,b[i]))
if (!bh[i]->b_uptodate)
ll_rw_block(READ,bh[i]);
} else
bh[i] = NULL;
for (i=0 ; i<4 ; i++,address += BLOCK_SIZE)
if (bh[i]) {
wait_on_buffer(bh[i]);
if (bh[i]->b_uptodate)
COPYBLK((unsigned long) bh[i]->b_data,address);
brelse(bh[i]);
}
}
/*
* Ok, breada can be used as bread, but additionally to mark other
* blocks for reading as well. End the argument list with a negative
* number.
*/
struct buffer_head * breada(int dev,int first, ...)
{
va_list args;
struct buffer_head * bh, *tmp;
va_start(args,first);
if (!(bh=getblk(dev,first)))
panic("bread: getblk returned NULL\n");
if (!bh->b_uptodate)
ll_rw_block(READ,bh);
while ((first=va_arg(args,int))>=0) {
tmp=getblk(dev,first);
if (tmp) {
if (!tmp->b_uptodate)
ll_rw_block(READA,bh);
tmp->b_count--;
}
}
va_end(args);
wait_on_buffer(bh);
if (bh->b_uptodate)
return bh;
brelse(bh);
return (NULL);
}
void buffer_init(long buffer_end)
{
struct buffer_head * h = start_buffer;
void * b;
int i;
if (buffer_end == 1<<20)
b = (void *) (640*1024);
else
b = (void *) buffer_end;
while ( (b -= BLOCK_SIZE) >= ((void *) (h+1)) ) {
h->b_dev = 0;
h->b_dirt = 0;
h->b_count = 0;
h->b_lock = 0;
h->b_uptodate = 0;
h->b_wait = NULL;
h->b_next = NULL;
h->b_prev = NULL;
h->b_data = (char *) b;
h->b_prev_free = h-1;
h->b_next_free = h+1;
h++;
NR_BUFFERS++;
if (b == (void *) 0x100000)
b = (void *) 0xA0000;
}
h--;
free_list = start_buffer;
free_list->b_prev_free = h;
h->b_next_free = free_list;
for (i=0;i<NR_HASH;i++)
hash_table[i]=NULL;
}
//mygetdents
/*<2A><><EFBFBD>建<EFBFBD><E5BBBA><EFBFBD><EFBFBD><EFBFBD>ṹ*/
struct linux_dirent
{
long d_ino;
off_t d_off;
unsigned short d_reclen;
char d_name[NAME_LEN+1];
};
int sys_getdents(unsigned int fd, struct linux_dirent* dirp, unsigned int
count)
{
struct file* file;
struct linux_dirent mydir;
struct dir_entry* dir;
struct m_inode* inode;
struct buffer_head* bh;
char* buf;
int i, j, dsize, ldsize;
int num = 0;
/*dirp<72><70>СΪ0*/
if (!count)
return -1;
file = current->filp[fd];//<2F><>fd<66><64><EFBFBD><EFBFBD>filp<6C><70><EFBFBD><EFBFBD>õ<EFBFBD><C3B5><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ļ<EFBFBD>file
inode = file->f_inode;//ͨ<><CDA8>file<6C>õ<EFBFBD><C3B5><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڵ<EFBFBD>f_inode
bh = bread(inode->i_dev, inode->i_zone[0]);//<2F><><EFBFBD><EFBFBD>bread<61><64><EFBFBD>豸<EFBFBD><E8B1B8>ȡ<EFBFBD><C8A1><EFBFBD>ļ<EFBFBD><C4BC><EFBFBD><EFBFBD>ݶ<EFBFBD>ӦӲ<D3A6><D3B2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD>
//<2F><><EFBFBD><EFBFBD>buffer_head<61>ṹ<EFBFBD><E1B9B9>ָ<EFBFBD><D6B8>bh
dsize = sizeof(struct dir_entry);//<2F><>ȡdir_entry<72>ṹ<EFBFBD><E1B9B9>Ĵ<EFBFBD>С
ldsize = sizeof(struct linux_dirent);//<2F><>ȡlinux_dirent<6E>ṹ<EFBFBD><E1B9B9>Ĵ<EFBFBD>С
for (j = 0; j < inode->i_size; j += dsize)
{
if (num + ldsize >= count)
return 0;
dir = (struct dir_entry*)(bh->b_data + j);
if (dir->inode)
{
mydir.d_ino = dir->inode;
for (i = 0; i < NAME_LEN; i++)
mydir.d_name[i] = dir->name[i];
mydir.d_off = 0;
mydir.d_reclen = sizeof(mydir);
buf = &mydir;
for (i = 0; i < mydir.d_reclen; i++)
{
put_fs_byte(*(buf + i), ((char*)dirp) + i + num);
}
num += mydir.d_reclen;
}
else
continue;
}
return num;
}
//mygetcwd
typedef struct
{
int d_fd;
int d_off;
int d_size;
char* d_buf;
} DIR;
struct direct {
ino_t d_ino;
char d_name[NAME_LEN];
};
static struct linux_dirent res;
_syscall3(int, read, int, fildes, char*, buf, off_t, count)
_syscall2(int, fstat, int, fildes, struct stat*, stat_buf)
_syscall2(int, stat, const char*, filename, struct stat*, stat_buf)
_syscall1(int, chdir, const char*, filename)
struct linux_dirent* readdir(DIR* dir)
{
struct direct* ptr;
if (!dir) {
errno = EBADF;
return NULL;
}
if (!dir->d_buf)
if (!(dir->d_buf = malloc(DIRBUF)))
return NULL;
else
dir->d_size = dir->d_off = 0;
while (1) {
if (dir->d_size <= dir->d_off) {
dir->d_off = 0;
dir->d_size = read(dir->d_fd, dir->d_buf, DIRBUF);
}
if (dir->d_size <= 0)
return NULL;
ptr = (struct direct*)(dir->d_off + dir->d_buf);
dir->d_off += sizeof(*ptr);
if (!ptr->d_ino)
continue;
res.d_ino = ptr->d_ino;
strncpy(res.d_name, ptr->d_name, NAME_LEN);
res.d_name[NAME_LEN] = 0;
res.d_reclen = strlen(res.d_name);
return &res;
}
}
int closedir(DIR* dir)
{
int fd;
if (!dir) {
errno = EBADF;
return -1;
}
fd = dir->d_fd;
free(dir->d_buf);
free(dir);
return close(fd);
}
DIR* opendir(const char* dirname)
{
int fd;
struct stat stat_buf;
DIR* ptr;
if ((fd = open(dirname, O_RDONLY)) < 0)
return NULL;
if (fstat(fd, &stat_buf) < 0 ||
!S_ISDIR(stat_buf.st_mode) ||
!(ptr = malloc(sizeof(*ptr)))) {
close(fd);
return NULL;
}
memset(ptr, 0, sizeof(*ptr));
ptr->d_fd = fd;
return ptr;
}
char* sys_getcwd(char* buf, size_t size) {
char path[BUF_MAX], cwd[BUF_MAX];
DIR* dirp;
struct linux_dirent* dp;
struct stat state0, state1, state2;
dev_t dev;
ino_t ino;
while (1) {
if (stat(".", &state0 == 0)) {
dev = state0.st_dev;
ino = state0.st_ino;
}
dirp = opendir("..");
stat("..", &state2);
if (state2.st_dev == dev && state2.st_ino == ino)
break;
while ((dp = readdir(dirp)) != NULL) {
memcpy(path, dp->d_name, BUF_MAX);
stat(path, &state1);
if (dev == state1.st_dev && ino == state1.st_ino) {
memset(cwd, 0, sizeof(cwd));
strcat(cwd, "/");
strcat(cwd, dp->d_name);
strcat(cwd, buf);
strncpy(buf, cwd, BUF_MAX);
break;
}
}
closedir(dirp);
chdir("..");
}
return buf;
}
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