block-vvfat.c

qemu虚拟机代码

	const char* dirname)
{
    bootsector_t* bootsector;
    mapping_t* mapping;
    unsigned int i;
    unsigned int cluster;

    memset(&(s->first_sectors[0]),0,0x40*0x200);

    s->cluster_size=s->sectors_per_cluster*0x200;
    s->cluster_buffer=malloc(s->cluster_size);
    assert(s->cluster_buffer);

    /*
     * The formula: sc = spf+1+spf*spc*(512*8/fat_type),
     * where sc is sector_count,
     * spf is sectors_per_fat,
     * spc is sectors_per_clusters, and
     * fat_type = 12, 16 or 32.
     */
    i = 1+s->sectors_per_cluster*0x200*8/s->fat_type;
    s->sectors_per_fat=(s->sector_count+i)/i; /* round up */
    
    array_init(&(s->mapping),sizeof(mapping_t));
    array_init(&(s->directory),sizeof(direntry_t));

    /* add volume label */
    {
	direntry_t* entry=array_get_next(&(s->directory));
	entry->attributes=0x28; /* archive | volume label */
	snprintf(entry->name,11,"QEMU VVFAT");
    }

    /* Now build FAT, and write back information into directory */
    init_fat(s);

    s->faked_sectors=s->first_sectors_number+s->sectors_per_fat*2;
    s->cluster_count=sector2cluster(s, s->sector_count);

    mapping = array_get_next(&(s->mapping));
    mapping->begin = 0;
    mapping->dir_index = 0;
    mapping->info.dir.parent_mapping_index = -1;
    mapping->first_mapping_index = -1;
    mapping->path = strdup(dirname);
    i = strlen(mapping->path);
    if (i > 0 && mapping->path[i - 1] == '/')
	mapping->path[i - 1] = '\0';
    mapping->mode = MODE_DIRECTORY;
    mapping->read_only = 0;
    s->path = mapping->path;

    for (i = 0, cluster = 0; i < s->mapping.next; i++) {
	int j;
	/* MS-DOS expects the FAT to be 0 for the root directory 
	 * (except for the media byte). */
	/* LATER TODO: still true for FAT32? */
	int fix_fat = (i != 0);
	mapping = array_get(&(s->mapping), i);

        if (mapping->mode & MODE_DIRECTORY) {
	    mapping->begin = cluster;
	    if(read_directory(s, i)) {
		fprintf(stderr, "Could not read directory %s\n",
			mapping->path);
		return -1;
	    }
	    mapping = array_get(&(s->mapping), i);
	} else {
	    assert(mapping->mode == MODE_UNDEFINED);
	    mapping->mode=MODE_NORMAL;
	    mapping->begin = cluster;
	    if (mapping->end > 0) {
		direntry_t* direntry = array_get(&(s->directory),
			mapping->dir_index);

		mapping->end = cluster + 1 + (mapping->end-1)/s->cluster_size;
		set_begin_of_direntry(direntry, mapping->begin);
	    } else {
		mapping->end = cluster + 1;
		fix_fat = 0;
	    }
	}

	assert(mapping->begin < mapping->end);

	/* fix fat for entry */
	if (fix_fat) {
	    for(j = mapping->begin; j < mapping->end - 1; j++)
		fat_set(s, j, j+1);
	    fat_set(s, mapping->end - 1, s->max_fat_value);
	}

	/* next free cluster */
	cluster = mapping->end;

	if(cluster > s->cluster_count) {
	    fprintf(stderr,"Directory does not fit in FAT%d\n",s->fat_type);
	    return -1;
	}
    }

    mapping = array_get(&(s->mapping), 0);
    s->sectors_of_root_directory = mapping->end * s->sectors_per_cluster;
    s->last_cluster_of_root_directory = mapping->end;

    /* the FAT signature */
    fat_set(s,0,s->max_fat_value);
    fat_set(s,1,s->max_fat_value);

    s->current_mapping = NULL;

    bootsector=(bootsector_t*)(s->first_sectors+(s->first_sectors_number-1)*0x200);
    bootsector->jump[0]=0xeb;
    bootsector->jump[1]=0x3e;
    bootsector->jump[2]=0x90;
    memcpy(bootsector->name,"QEMU    ",8);
    bootsector->sector_size=cpu_to_le16(0x200);
    bootsector->sectors_per_cluster=s->sectors_per_cluster;
    bootsector->reserved_sectors=cpu_to_le16(1);
    bootsector->number_of_fats=0x2; /* number of FATs */
    bootsector->root_entries=cpu_to_le16(s->sectors_of_root_directory*0x10);
    bootsector->total_sectors16=s->sector_count>0xffff?0:cpu_to_le16(s->sector_count);
    bootsector->media_type=(s->fat_type!=12?0xf8:s->sector_count==5760?0xf9:0xf8); /* media descriptor */
    s->fat.pointer[0] = bootsector->media_type;
    bootsector->sectors_per_fat=cpu_to_le16(s->sectors_per_fat);
    bootsector->sectors_per_track=cpu_to_le16(s->bs->secs);
    bootsector->number_of_heads=cpu_to_le16(s->bs->heads);
    bootsector->hidden_sectors=cpu_to_le32(s->first_sectors_number==1?0:0x3f);
    bootsector->total_sectors=cpu_to_le32(s->sector_count>0xffff?s->sector_count:0);

    /* LATER TODO: if FAT32, this is wrong */
    bootsector->u.fat16.drive_number=s->fat_type==12?0:0x80; /* assume this is hda (TODO) */
    bootsector->u.fat16.current_head=0;
    bootsector->u.fat16.signature=0x29;
    bootsector->u.fat16.id=cpu_to_le32(0xfabe1afd);

    memcpy(bootsector->u.fat16.volume_label,"QEMU VVFAT ",11);
    memcpy(bootsector->fat_type,(s->fat_type==12?"FAT12   ":s->fat_type==16?"FAT16   ":"FAT32   "),8);
    bootsector->magic[0]=0x55; bootsector->magic[1]=0xaa;

    return 0;
}

static BDRVVVFATState *vvv = NULL;

static int enable_write_target(BDRVVVFATState *s);
static int is_consistent(BDRVVVFATState *s);

static int vvfat_open(BlockDriverState *bs, const char* dirname)
{
    BDRVVVFATState *s = bs->opaque;
    int floppy = 0;
    int i;

    vvv = s;

DLOG(if (stderr == NULL) {
    stderr = fopen("vvfat.log", "a");
    setbuf(stderr, NULL);
})

    s->bs = bs;

    s->fat_type=16;
    /* LATER TODO: if FAT32, adjust */
    s->sector_count=0xec04f;
    s->sectors_per_cluster=0x10;
    /* LATER TODO: this could be wrong for FAT32 */
    bs->cyls=1023; bs->heads=15; bs->secs=63;

    s->current_cluster=0xffffffff;

    s->first_sectors_number=0x40;
    /* read only is the default for safety */
    bs->read_only = 1;
    s->qcow = s->write_target = NULL;
    s->qcow_filename = NULL;
    s->fat2 = NULL;
    s->downcase_short_names = 1;
    
    if (!strstart(dirname, "fat:", NULL))
	return -1;

    if (strstr(dirname, ":rw:")) {
	if (enable_write_target(s))
	    return -1;
	bs->read_only = 0;
    }

    if (strstr(dirname, ":floppy:")) {
	floppy = 1;
	s->fat_type = 12;
	s->first_sectors_number = 1;
	s->sectors_per_cluster=2;
	bs->cyls = 80; bs->heads = 2; bs->secs = 36;
    }

    if (strstr(dirname, ":32:")) {
	fprintf(stderr, "Big fat greek warning: FAT32 has not been tested. You are welcome to do so!\n");
	s->fat_type = 32;
    } else if (strstr(dirname, ":16:")) {
	s->fat_type = 16;
    } else if (strstr(dirname, ":12:")) {
	s->fat_type = 12;
	s->sector_count=2880;
    }

    i = strrchr(dirname, ':') - dirname;
    assert(i >= 3);
    if (dirname[i-2] == ':' && isalpha(dirname[i-1]))
	/* workaround for DOS drive names */
	dirname += i-1;
    else
	dirname += i+1;

    bs->total_sectors=bs->cyls*bs->heads*bs->secs;
    if (s->sector_count > bs->total_sectors)
	s->sector_count = bs->total_sectors;
    if(init_directories(s, dirname))
	return -1;

    if(s->first_sectors_number==0x40)
	init_mbr(s);

    /* for some reason or other, MS-DOS does not like to know about CHS... */
    if (floppy)
	bs->heads = bs->cyls = bs->secs = 0;

    //    assert(is_consistent(s));

    return 0;
}

static inline void vvfat_close_current_file(BDRVVVFATState *s)
{
    if(s->current_mapping) {
	s->current_mapping = NULL;
	if (s->current_fd) {
		close(s->current_fd);
		s->current_fd = 0;
	}
    }
    s->current_cluster = -1;
}

/* mappings between index1 and index2-1 are supposed to be ordered
 * return value is the index of the last mapping for which end>cluster_num
 */
static inline int find_mapping_for_cluster_aux(BDRVVVFATState* s,int cluster_num,int index1,int index2)
{
    int index3=index1+1;
    while(1) {
	mapping_t* mapping;
	index3=(index1+index2)/2;
	mapping=array_get(&(s->mapping),index3);
	assert(mapping->begin < mapping->end);
	if(mapping->begin>=cluster_num) {
	    assert(index2!=index3 || index2==0);
	    if(index2==index3)
		return index1;
	    index2=index3;
	} else {
	    if(index1==index3)
		return mapping->end<=cluster_num ? index2 : index1;
	    index1=index3;
	}
	assert(index1<=index2);
	DLOG(mapping=array_get(&(s->mapping),index1);
	assert(mapping->begin<=cluster_num);
	assert(index2 >= s->mapping.next || 
		((mapping = array_get(&(s->mapping),index2)) &&
		mapping->end>cluster_num)));
    }
}

static inline mapping_t* find_mapping_for_cluster(BDRVVVFATState* s,int cluster_num)
{
    int index=find_mapping_for_cluster_aux(s,cluster_num,0,s->mapping.next);
    mapping_t* mapping;
    if(index>=s->mapping.next)
	return 0;
    mapping=array_get(&(s->mapping),index);
    if(mapping->begin>cluster_num)
	return 0;
    assert(mapping->begin<=cluster_num && mapping->end>cluster_num);
    return mapping;
}

/*
 * This function simply compares path == mapping->path. Since the mappings
 * are sorted by cluster, this is expensive: O(n).
 */
static inline mapping_t* find_mapping_for_path(BDRVVVFATState* s,
	const char* path)
{
    int i;

    for (i = 0; i < s->mapping.next; i++) {
	mapping_t* mapping = array_get(&(s->mapping), i);
	if (mapping->first_mapping_index < 0 &&
		!strcmp(path, mapping->path))
	    return mapping;
    }

    return NULL;
}

static int open_file(BDRVVVFATState* s,mapping_t* mapping)
{
    if(!mapping)
	return -1;
    if(!s->current_mapping ||
	    strcmp(s->current_mapping->path,mapping->path)) {
	/* open file */
	int fd = open(mapping->path, O_RDONLY | O_BINARY | O_LARGEFILE);
	if(fd<0)
	    return -1;
	vvfat_close_current_file(s);
	s->current_fd = fd;
	s->current_mapping = mapping;
    }
    return 0;
}

static inline int read_cluster(BDRVVVFATState *s,int cluster_num)
{
    if(s->current_cluster != cluster_num) {
	int result=0;
	off_t offset;
	assert(!s->current_mapping || s->current_fd || (s->current_mapping->mode & MODE_DIRECTORY));
	if(!s->current_mapping
		|| s->current_mapping->begin>cluster_num
		|| s->current_mapping->end<=cluster_num) {
	    /* binary search of mappings for file */
	    mapping_t* mapping=find_mapping_for_cluster(s,cluster_num);

	    assert(!mapping || (cluster_num>=mapping->begin && cluster_num<mapping->end));

	    if (mapping && mapping->mode & MODE_DIRECTORY) {
		vvfat_close_current_file(s);
		s->current_mapping = mapping;
read_cluster_directory:
		offset = s->cluster_size*(cluster_num-s->current_mapping->begin);
		s->cluster = s->directory.pointer+offset
			+ 0x20*s->current_mapping->info.dir.first_dir_index;
		assert(((s->cluster-(unsigned char*)s->directory.pointer)%s->cluster_size)==0);
		assert((char*)s->cluster+s->cluster_size <= s->directory.pointer+s->directory.next*s->directory.item_size);
		s->current_cluster = cluster_num;
		return 0;
	    }

	    if(open_file(s,mapping))
		return -2;
	} else if (s->current_mapping->mode & MODE_DIRECTORY)
	    goto read_cluster_directory;

	assert(s->current_fd);

	offset=s->cluster_size*(cluster_num-s->current_mapping->begin)+s->current_mapping->info.file.offset;
	if(lseek(s->current_fd, offset, SEEK_SET)!=offset)
	    return -3;
	s->cluster=s->cluster_buffer;
	result=read(s->current_fd,s->cluster,s->cluster_size);
	if(result<0) {
	    s->current_cluster = -1;
	    return -1;
	}
	s->current_cluster = cluster_num;
    }
    return 0;
}

#ifdef DEBUG
static void hexdump(const void* address, uint32_t len)
{
    const unsigned char* p = address;
    int i, j;

    for (i = 0; i < len; i += 16) {
	for (j = 0; j < 16 && i + j < len; j++)
	    fprintf(stderr, "%02x ", p[i + j]);
	for (; j < 16; j++)
	    fprintf(stderr, "   ");
	fprintf(stderr, " ");
	for (j = 0; j < 16 && i + j < len; j++)
	    fprintf(stderr, "%c", (p[i + j] < ' ' || p[i + j] > 0x7f) ? '.' : p[i + j]);
	fprintf(stderr, "\n");
    }
}

static void print_direntry(const direntry_t* direntry)
{
    int j = 0;
    char buffer[1024];

    fprintf(stderr, "direntry 0x%x: ", (int)direntry);
    if(!direntry)
	return;
    if(is_long_name(direntry)) {
	unsigned char* c=(unsigned char*)direntry;
	int i;
	for(i=1;i<11 && c[i] && c[i]!=0xff;i+=2)
#define ADD_CHAR(c) {buffer[j] = (c); if (buffer[j] < ' ') buffer[j] = '