dir.c

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

/*
 *  linux/fs/fat/dir.c
 *
 *  directory handling functions for fat-based filesystems
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  Hidden files 1995 by Albert Cahalan <[e-mail]> <[e-mail]>
 *
 *  VFAT extensions by Gordon Chaffee <[e-mail]>
 *  Merged with msdos fs by Henrik Storner <[e-mail]>
 *  Rewritten for constant inumbers. Plugged buffer overrun in readdir(). AV
 *  Short name translation 1999 by Wolfram Pienkoss <[e-mail]>
 */

#define ASC_LINUX_VERSION(V, P, S)	(((V) * 65536) + ((P) * 256) + (S))

#include <linux/version.h>
#include <linux/fs.h>
#include <linux/msdos_fs.h>
#include <linux/nls.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/ioctl.h>
#include <linux/dirent.h>
#include <linux/mm.h>
#include <linux/ctype.h>

#include <asm/uaccess.h>

#include "msbuffer.h"

#define PRINTK(X)

struct file_operations fat_dir_operations = {
	read:		generic_read_dir,
	readdir:	fat_readdir,
	ioctl:		fat_dir_ioctl,
	fsync:		file_fsync,
};

/*
 * Convert Unicode 16 to UTF8, translated Unicode, or ASCII.
 * If uni_xlate is enabled and we can't get a 1:1 conversion, use a
 * colon as an escape character since it is normally invalid on the vfat
 * filesystem. The following four characters are the hexadecimal digits
 * of Unicode value. This lets us do a full dump and restore of Unicode
 * filenames. We could get into some trouble with long Unicode names,
 * but ignore that right now.
 * Ahem... Stack smashing in ring 0 isn't fun. Fixed.
 */
static int
uni16_to_x8(unsigned char *ascii, wchar_t *uni, int uni_xlate,
	    struct nls_table *nls)
{
	wchar_t *ip, ec;
	unsigned char *op, nc;
	int charlen;
	int k;

	ip = uni;
	op = ascii;

	while (*ip) {
		ec = *ip++;
		if ( (charlen = nls->uni2char(ec, op, 3)) > 0) {
			op += charlen;
		} else {
			if (uni_xlate == 1) {
				*op = ':';
				for (k = 4; k > 0; k--) {
					nc = ec & 0xF;
					op[k] = nc > 9	? nc + ('a' - 10)
							: nc + '0';
					ec >>= 4;
				}
				op += 5;
			} else {
				*op++ = '?';
			}
		}
		/* We have some slack there, so it's OK */
		if (op>ascii+256) {
			op = ascii + 256;
			break;
		}
	}
	*op = 0;
	return (op - ascii);
}

#if 0
static void dump_de(struct msdos_dir_entry *de)
{
	int i;
	unsigned char *p = (unsigned char *) de;
	printk("[");

	for (i = 0; i < 32; i++, p++) {
		printk("%02x ", *p);
	}
	printk("]\n");
}
#endif

static inline unsigned char
fat_tolower(struct nls_table *t, unsigned char c)
{
	unsigned char nc = t->charset2lower[c];

	return nc ? nc : c;
}

static inline int
fat_short2lower_uni(struct nls_table *t, unsigned char c, wchar_t *uni)
{
	int charlen;
	unsigned char nc = t->charset2lower[c];
	
	if (!nc)
		nc = c;

	if ( (charlen = t->char2uni(&nc, 1, uni)) < 0) {
		*uni = 0x003f;	/* a question mark */
	}
	return charlen;
}

static int
fat_strnicmp(struct nls_table *t, const unsigned char *s1,
					const unsigned char *s2, int len)
{
	while(len--)
		if (fat_tolower(t, *s1++) != fat_tolower(t, *s2++))
			return 1;

	return 0;
}

/*
 * Return values: negative -> error, 0 -> not found, positive -> found,
 * value is the total amount of slots, including the shortname entry.
 */
int fat_search_long(struct inode *inode, const char *name, int name_len,
			int anycase, loff_t *spos, loff_t *lpos)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh = NULL;
	struct msdos_dir_entry *de;
	struct nls_table *nls_io = MSDOS_SB(sb)->nls_io;
	struct nls_table *nls_disk = MSDOS_SB(sb)->nls_disk;
	wchar_t bufuname[14];
	unsigned char xlate_len, long_slots, *unicode = NULL;
	char c, bufname[260];	/* 256 + 4 */
	int uni_xlate = MSDOS_SB(sb)->options.unicode_xlate;
	int utf8 = MSDOS_SB(sb)->options.utf8;
	int ino, i, i2, last, res = 0;
	loff_t cpos = 0;

	while(1) {
		if (fat_get_entry(inode,&cpos,&bh,&de,&ino) == -1)
			goto EODir;
parse_record:
		long_slots = 0;
		if (de->name[0] == (__s8) DELETED_FLAG)
			continue;
		if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
			continue;
		if (de->attr != ATTR_EXT && IS_FREE(de->name))
			continue;
		if (de->attr == ATTR_EXT) {
			struct msdos_dir_slot *ds;
			int offset;
			unsigned char id;
			unsigned char slot;
			unsigned char slots;
			unsigned char sum;
			unsigned char alias_checksum;

			if (!unicode) {
				unicode = (unsigned char *)
					__get_free_page(GFP_KERNEL);
				if (!unicode) {
					fat_brelse(sb, bh);
					return -ENOMEM;
				}
			}
parse_long:
			slots = 0;
			offset = 0;
			ds = (struct msdos_dir_slot *) de;
			id = ds->id;
			if (!(id & 0x40))
				continue;
			slots = id & ~0x40;
			if (slots > 20 || !slots)	/* ceil(256 * 2 / 26) */
				continue;
			long_slots = slots;
			alias_checksum = ds->alias_checksum;

			slot = slots;
			while (1) {
				slot--;
				offset = slot * 26;
				memcpy(&unicode[offset], ds->name0_4, 10);
				memcpy(&unicode[offset+10], ds->name5_10, 12);
				memcpy(&unicode[offset+22], ds->name11_12, 4);
				offset += 26;

				if (ds->id & 0x40) {
					unicode[offset] = 0;
					unicode[offset+1] = 0;
				}
				if (fat_get_entry(inode,&cpos,&bh,&de,&ino)<0)
					goto EODir;
				if (slot == 0)
					break;
				ds = (struct msdos_dir_slot *) de;
				if (ds->attr !=  ATTR_EXT)
					goto parse_record;
				if ((ds->id & ~0x40) != slot)
					goto parse_long;
				if (ds->alias_checksum != alias_checksum)
					goto parse_long;
			}
			if (de->name[0] == (__s8) DELETED_FLAG)
				continue;
			if (de->attr ==  ATTR_EXT)
				goto parse_long;
			if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME))
				continue;
			for (sum = 0, i = 0; i < 11; i++)
				sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i];
			if (sum != alias_checksum)
				long_slots = 0;
		}

		for (i = 0, last = 0; i < 8;) {
			if (!(c = de->name[i])) break;
			if (c == 0x05) c = 0xE5;
			fat_short2lower_uni(nls_disk, c, &bufuname[i++]);
			if (c != ' ')
				last = i;
		}
		i = last;
		fat_short2lower_uni(nls_disk, '.', &bufuname[i++]);
		for (i2 = 0; i2 < 3; i2++) {
			if (!(c = de->ext[i2])) break;
			fat_short2lower_uni(nls_disk, c, &bufuname[i++]);
			if (c != ' ')
				last = i;
		}
		if (!last)
			continue;

		memset(&bufuname[last], 0, sizeof(wchar_t));
		xlate_len = utf8
			?utf8_wcstombs(bufname, bufuname, 260)
			:uni16_to_x8(bufname, bufuname, uni_xlate, nls_io);
		if (xlate_len == name_len)
			if ((!anycase && !memcmp(name, bufname, xlate_len)) ||
			    (anycase && !fat_strnicmp(nls_io, name, bufname,
								xlate_len)))
				goto Found;

		if (long_slots) {
			xlate_len = utf8
				?utf8_wcstombs(bufname, (wchar_t *) unicode, 260)
				:uni16_to_x8(bufname, (wchar_t *) unicode, uni_xlate, nls_io);
			if (xlate_len != name_len)
				continue;
			if ((!anycase && !memcmp(name, bufname, xlate_len)) ||
			    (anycase && !fat_strnicmp(nls_io, name, bufname,
								xlate_len)))
				goto Found;
		}
	}

Found:
	res = long_slots + 1;
	*spos = cpos - sizeof(struct msdos_dir_entry);
	*lpos = cpos - res*sizeof(struct msdos_dir_entry);
EODir:
	fat_brelse(sb, bh);
	if (unicode) {
		free_page((unsigned long) unicode);
	}
	return res;
}

static int fat_readdirx(struct inode *inode, struct file *filp, void *dirent,
			filldir_t filldir, int shortnames, int both)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh;
	struct msdos_dir_entry *de;
	struct nls_table *nls_io = MSDOS_SB(sb)->nls_io;
	struct nls_table *nls_disk = MSDOS_SB(sb)->nls_disk;
	wchar_t bufuname[14], *ptuname = &bufuname[0];
	unsigned char long_slots, *unicode = NULL;
	char c, bufname[56], *ptname = bufname;
	unsigned long lpos, dummy, *furrfu = &lpos;
	int uni_xlate = MSDOS_SB(sb)->options.unicode_xlate;
	int isvfat = MSDOS_SB(sb)->options.isvfat;
	int utf8 = MSDOS_SB(sb)->options.utf8;
	int nocase = MSDOS_SB(sb)->options.nocase;
	int ino,inum,i,i2,last, dotoffset = 0;
	loff_t cpos;

	cpos = filp->f_pos;
/* Fake . and .. for the root directory. */
	if (inode->i_ino == MSDOS_ROOT_INO) {
		while (cpos < 2) {
			if (filldir(dirent, "..", cpos+1, cpos, MSDOS_ROOT_INO, DT_DIR) < 0)
				return 0;
			cpos++;
			filp->f_pos++;
		}
		if (cpos == 2) {
			dummy = 2;
			furrfu = &dummy;
			cpos = 0;
		}
	}
	if (cpos & (sizeof(struct msdos_dir_entry)-1))
		return -ENOENT;

 	bh = NULL;
GetNew:
	long_slots = 0;
	if (fat_get_entry(inode,&cpos,&bh,&de,&ino) == -1)
		goto EODir;
	/* Check for long filename entry */
	if (isvfat) {
		if (de->name[0] == (__s8) DELETED_FLAG)
			goto RecEnd;
		if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
			goto RecEnd;
		if (de->attr != ATTR_EXT && IS_FREE(de->name))
			goto RecEnd;
	} else {
		if ((de->attr & ATTR_VOLUME) || IS_FREE(de->name))
			goto RecEnd;
	}

	if (isvfat && de->attr == ATTR_EXT) {
		struct msdos_dir_slot *ds;
		int offset;
		unsigned char id;
		unsigned char slot;
		unsigned char slots;