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Diffstat (limited to 'util-linux/volume_id/fat.c')
-rw-r--r--util-linux/volume_id/fat.c128
1 files changed, 62 insertions, 66 deletions
diff --git a/util-linux/volume_id/fat.c b/util-linux/volume_id/fat.c
index 9ab1cef..816d69d 100644
--- a/util-linux/volume_id/fat.c
+++ b/util-linux/volume_id/fat.c
@@ -20,8 +20,11 @@
#include "volume_id_internal.h"
-#define FAT12_MAX 0xff5
-#define FAT16_MAX 0xfff5
+/* linux/msdos_fs.h says: */
+#define FAT12_MAX 0xff4
+#define FAT16_MAX 0xfff4
+#define FAT32_MAX 0x0ffffff6
+
#define FAT_ATTR_VOLUME_ID 0x08
#define FAT_ATTR_DIR 0x10
#define FAT_ATTR_LONG_NAME 0x0f
@@ -31,9 +34,9 @@
struct vfat_super_block {
uint8_t boot_jump[3];
uint8_t sysid[8];
- uint16_t sector_size;
+ uint16_t sector_size_bytes;
uint8_t sectors_per_cluster;
- uint16_t reserved;
+ uint16_t reserved_sct;
uint8_t fats;
uint16_t dir_entries;
uint16_t sectors;
@@ -84,32 +87,30 @@ struct vfat_dir_entry {
uint32_t size;
} __attribute__((__packed__));
-static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
+static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count)
{
- unsigned i;
-
- for (i = 0; i < count; i++) {
+ for (;--count >= 0; dir++) {
/* end marker */
- if (dir[i].name[0] == 0x00) {
+ if (dir->name[0] == 0x00) {
dbg("end of dir");
break;
}
/* empty entry */
- if (dir[i].name[0] == FAT_ENTRY_FREE)
+ if (dir->name[0] == FAT_ENTRY_FREE)
continue;
/* long name */
- if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
+ if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
continue;
- if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
+ if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
/* labels do not have file data */
- if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
+ if (dir->cluster_high != 0 || dir->cluster_low != 0)
continue;
dbg("found ATTR_VOLUME_ID id in root dir");
- return dir[i].name;
+ return dir->name;
}
dbg("skip dir entry");
@@ -118,31 +119,29 @@ static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
return NULL;
}
-int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
+int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
{
struct vfat_super_block *vs;
struct vfat_dir_entry *dir;
- uint16_t sector_size;
+ uint16_t sector_size_bytes;
uint16_t dir_entries;
uint32_t sect_count;
- uint16_t reserved;
- uint32_t fat_size;
+ uint16_t reserved_sct;
+ uint32_t fat_size_sct;
uint32_t root_cluster;
- uint32_t dir_size;
+ uint32_t dir_size_sct;
uint32_t cluster_count;
- uint32_t fat_length;
- uint64_t root_start;
- uint32_t start_data_sect;
- uint16_t root_dir_entries;
+ uint64_t root_start_off;
+ uint32_t start_data_sct;
uint8_t *buf;
uint32_t buf_size;
uint8_t *label = NULL;
- uint32_t next;
+ uint32_t next_cluster;
int maxloop;
- dbg("probing at offset 0x%llx", (unsigned long long) off);
+ dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
- vs = volume_id_get_buffer(id, off, 0x200);
+ vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
if (vs == NULL)
return -1;
@@ -196,34 +195,34 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
valid:
/* sector size check */
- sector_size = le16_to_cpu(vs->sector_size);
- if (sector_size != 0x200 && sector_size != 0x400 &&
- sector_size != 0x800 && sector_size != 0x1000)
+ sector_size_bytes = le16_to_cpu(vs->sector_size_bytes);
+ if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400 &&
+ sector_size_bytes != 0x800 && sector_size_bytes != 0x1000)
return -1;
- dbg("sector_size 0x%x", sector_size);
+ dbg("sector_size_bytes 0x%x", sector_size_bytes);
dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
- dir_entries = le16_to_cpu(vs->dir_entries);
- reserved = le16_to_cpu(vs->reserved);
- dbg("reserved 0x%x", reserved);
+ reserved_sct = le16_to_cpu(vs->reserved_sct);
+ dbg("reserved_sct 0x%x", reserved_sct);
sect_count = le16_to_cpu(vs->sectors);
if (sect_count == 0)
sect_count = le32_to_cpu(vs->total_sect);
dbg("sect_count 0x%x", sect_count);
- fat_length = le16_to_cpu(vs->fat_length);
- if (fat_length == 0)
- fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
- dbg("fat_length 0x%x", fat_length);
+ fat_size_sct = le16_to_cpu(vs->fat_length);
+ if (fat_size_sct == 0)
+ fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
+ fat_size_sct *= vs->fats;
+ dbg("fat_size_sct 0x%x", fat_size_sct);
- fat_size = fat_length * vs->fats;
- dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
- (sector_size-1)) / sector_size;
- dbg("dir_size 0x%x", dir_size);
+ dir_entries = le16_to_cpu(vs->dir_entries);
+ dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
+ (sector_size_bytes-1)) / sector_size_bytes;
+ dbg("dir_size_sct 0x%x", dir_size_sct);
- cluster_count = sect_count - (reserved + fat_size + dir_size);
+ cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
cluster_count /= vs->sectors_per_cluster;
dbg("cluster_count 0x%x", cluster_count);
@@ -239,21 +238,18 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
goto fat32;
/* the label may be an attribute in the root directory */
- root_start = (reserved + fat_size) * sector_size;
- dbg("root dir start 0x%llx", (unsigned long long) root_start);
- root_dir_entries = le16_to_cpu(vs->dir_entries);
- dbg("expected entries 0x%x", root_dir_entries);
+ root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
+ dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
+ dbg("expected entries 0x%x", dir_entries);
- buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
- buf = volume_id_get_buffer(id, off + root_start, buf_size);
+ buf_size = dir_entries * sizeof(struct vfat_dir_entry);
+ buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
if (buf == NULL)
goto found;
- dir = (struct vfat_dir_entry*) buf;
-
- label = get_attr_volume_id(dir, root_dir_entries);
+ label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
- vs = volume_id_get_buffer(id, off, 0x200);
+ vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
if (vs == NULL)
return -1;
@@ -269,26 +265,25 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
fat32:
/* FAT32 root dir is a cluster chain like any other directory */
- buf_size = vs->sectors_per_cluster * sector_size;
+ buf_size = vs->sectors_per_cluster * sector_size_bytes;
root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
- dbg("root dir cluster %u", root_cluster);
- start_data_sect = reserved + fat_size;
+ start_data_sct = reserved_sct + fat_size_sct;
- next = root_cluster;
+ next_cluster = root_cluster;
maxloop = 100;
while (--maxloop) {
- uint32_t next_sect_off;
+ uint32_t next_off_sct;
uint64_t next_off;
uint64_t fat_entry_off;
int count;
- dbg("next cluster %u", next);
- next_sect_off = (next - 2) * vs->sectors_per_cluster;
- next_off = (start_data_sect + next_sect_off) * sector_size;
+ dbg("next_cluster 0x%x", (unsigned)next_cluster);
+ next_off_sct = (next_cluster - 2) * vs->sectors_per_cluster;
+ next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
dbg("cluster offset 0x%llx", (unsigned long long) next_off);
/* get cluster */
- buf = volume_id_get_buffer(id, off + next_off, buf_size);
+ buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
if (buf == NULL)
goto found;
@@ -301,20 +296,21 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
break;
/* get FAT entry */
- fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
- buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
+ fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
+ dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
+ buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
if (buf == NULL)
goto found;
/* set next cluster */
- next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
- if (next == 0)
+ next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
+ if (next_cluster < 2 || next_cluster > FAT32_MAX)
break;
}
if (maxloop == 0)
dbg("reached maximum follow count of root cluster chain, give up");
- vs = volume_id_get_buffer(id, off, 0x200);
+ vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
if (vs == NULL)
return -1;
generated by cgit v1.1 at 2024-12-24 18:23:21 +0000