X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=extras%2Fvolume_id%2Flib%2Ffat.c;h=c0cfed82c008ccfd9d18c3a37f466f45ea7abbcf;hb=cc02d72c82d4ebc2c0803bae0c94707e9d1eea83;hp=e5a5cc119180b025b59225f7379640867508f309;hpb=0565a00a4cfdabd325bf2e117620d5f15dd46cda;p=elogind.git

diff --git a/extras/volume_id/lib/fat.c b/extras/volume_id/lib/fat.c
index e5a5cc119..c0cfed82c 100644
--- a/extras/volume_id/lib/fat.c
+++ b/extras/volume_id/lib/fat.c
@@ -281,10 +281,6 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size)
 	if (buf == NULL)
 		return -1;
 
-	/* check signature */
-	if (buf[510] != 0x55 || buf[511] != 0xaa)
-		return -1;
-
 	vs = (struct vfat_super_block *) buf;
 	if (memcmp(vs->sysid, "NTFS", 4) == 0)
 		return -1;
@@ -305,12 +301,17 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size)
 	if (memcmp(vs->type.fat.magic, "FAT12   ", 8) == 0)
 		goto magic;
 
+	/* check signature */
+	if (buf[510] != 0x55 || buf[511] != 0xaa)
+		return -1;
+
 	/* some old floppies don't have a magic, expect the boot jump address to match */
 	if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
 	     vs->boot_jump[0] != 0xe9)
 		return -1;
 
 magic:
+	info("magic found\n");
 	/* reserverd sector count */
 	if (!vs->reserved)
 		return -1;
@@ -333,6 +334,7 @@ magic:
 	if (sector_size == 0 || ((sector_size & (sector_size-1)) != 0))
 		return -1;
 
+	info("checks passed\n");
 	dbg("sector_size 0x%x\n", sector_size);
 	dbg("sectors_per_cluster 0x%x\n", vs->sectors_per_cluster);
 
@@ -346,9 +348,9 @@ magic:
 	dbg("sect_count 0x%x\n", sect_count);
 
 	fat_length = le16_to_cpu(vs->fat_length);
-	dbg("fat_length 0x%x\n", fat_length);
+	info("fat_length 0x%x\n", fat_length);
 	fat32_length = le32_to_cpu(vs->type.fat32.fat32_length);
-	dbg("fat32_length 0x%x\n", fat32_length);
+	info("fat32_length 0x%x\n", fat32_length);
 
 	if (fat_length)
 		fat_size = fat_length * vs->fats;
@@ -356,15 +358,15 @@ magic:
 		fat_size = fat32_length * vs->fats;
 	else
 		return -1;
-	dbg("fat_size 0x%x\n", fat_size);
+	info("fat_size 0x%x\n", fat_size);
 
 	dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
 			(sector_size-1)) / sector_size;
-	dbg("dir_size 0x%x\n", dir_size);
+	info("dir_size 0x%x\n", dir_size);
 
 	cluster_count = sect_count - (reserved + fat_size + dir_size);
 	cluster_count /= vs->sectors_per_cluster;
-	dbg("cluster_count 0x%x\n", cluster_count);
+	info("cluster_count 0x%x\n", cluster_count);
 
 	/* must be FAT32 */
 	if (!fat_length && fat32_length)
@@ -408,16 +410,30 @@ magic:
 	goto found;
 
 fat32:
-	/* FAT32 should have a valid signature in the fsinfo block */
+	info("looking for FAT32\n");
+	/*
+	 * FAT32 should have a valid signature in the fsinfo block,
+	 * but also allow all bytes set to '\0', because some volumes
+	 * do not set the signature at all.
+	 */
 	fsinfo_sect = le16_to_cpu(vs->type.fat32.fsinfo_sector);
 	buf = volume_id_get_buffer(id, off + (fsinfo_sect * sector_size), 0x200);
 	if (buf == NULL)
 		return -1;
 	fsinfo = (struct fat32_fsinfo *) buf;
-	if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0)
+	info("signature1: 0x%02x%02x%02x%02x\n",
+	     fsinfo->signature1[0], fsinfo->signature1[1],
+	     fsinfo->signature1[2], fsinfo->signature1[3]);
+	info("signature2: 0x%02x%02x%02x%02x\n",
+	     fsinfo->signature2[0], fsinfo->signature2[1],
+	     fsinfo->signature2[2], fsinfo->signature2[3]);
+	if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0 &&
+	    memcmp(fsinfo->signature1, "\x00\x00\x00\x00", 4) != 0)
 		return -1;
-	if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0)
+	if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0 &&
+	    memcmp(fsinfo->signature2, "\x00\x00\x00\x00", 4) != 0)
 		return -1 ;
+	info("FAT32 signatures ok\n");
 
 	vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
 	if (vs == NULL)
@@ -487,6 +503,7 @@ fat32:
 found:
 	volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
 	id->type = "vfat";
-
+	/* we think this is fat, but we make sure no other signatures are found */
+	id->force_unique_result = 1;
 	return 0;
 }