1 files changed, 99 insertions, 0 deletions
diff --git a/fs/adfs/map.c b/fs/adfs/map.c
index f44d12cef5be..120e01451e75 100644
--- a/fs/adfs/map.c
+++ b/fs/adfs/map.c
@@ -4,6 +4,7 @@
  *
  *  Copyright (C) 1997-2002 Russell King
  */
+#include <linux/slab.h>
 #include <asm/unaligned.h>
 #include "adfs.h"
 
@@ -280,3 +281,101 @@ bad_fragment:
 		   frag_id, zone, asb->s_map_size);
 	return 0;
 }
+
+static unsigned char adfs_calczonecheck(struct super_block *sb, unsigned char *map)
+{
+	unsigned int v0, v1, v2, v3;
+	int i;
+
+	v0 = v1 = v2 = v3 = 0;
+	for (i = sb->s_blocksize - 4; i; i -= 4) {
+		v0 += map[i]     + (v3 >> 8);
+		v3 &= 0xff;
+		v1 += map[i + 1] + (v0 >> 8);
+		v0 &= 0xff;
+		v2 += map[i + 2] + (v1 >> 8);
+		v1 &= 0xff;
+		v3 += map[i + 3] + (v2 >> 8);
+		v2 &= 0xff;
+	}
+	v0 +=           v3 >> 8;
+	v1 += map[1] + (v0 >> 8);
+	v2 += map[2] + (v1 >> 8);
+	v3 += map[3] + (v2 >> 8);
+
+	return v0 ^ v1 ^ v2 ^ v3;
+}
+
+static int adfs_checkmap(struct super_block *sb, struct adfs_discmap *dm)
+{
+	unsigned char crosscheck = 0, zonecheck = 1;
+	int i;
+
+	for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) {
+		unsigned char *map;
+
+		map = dm[i].dm_bh->b_data;
+
+		if (adfs_calczonecheck(sb, map) != map[0]) {
+			adfs_error(sb, "zone %d fails zonecheck", i);
+			zonecheck = 0;
+		}
+		crosscheck ^= map[3];
+	}
+	if (crosscheck != 0xff)
+		adfs_error(sb, "crosscheck != 0xff");
+	return crosscheck == 0xff && zonecheck;
+}
+
+struct adfs_discmap *adfs_read_map(struct super_block *sb, struct adfs_discrecord *dr)
+{
+	struct adfs_discmap *dm;
+	unsigned int map_addr, zone_size, nzones;
+	int i, zone;
+	struct adfs_sb_info *asb = ADFS_SB(sb);
+
+	nzones    = asb->s_map_size;
+	zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare);
+	map_addr  = (nzones >> 1) * zone_size -
+		     ((nzones > 1) ? ADFS_DR_SIZE_BITS : 0);
+	map_addr  = signed_asl(map_addr, asb->s_map2blk);
+
+	asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1);
+
+	dm = kmalloc_array(nzones, sizeof(*dm), GFP_KERNEL);
+	if (dm == NULL) {
+		adfs_error(sb, "not enough memory");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	for (zone = 0; zone < nzones; zone++, map_addr++) {
+		dm[zone].dm_startbit = 0;
+		dm[zone].dm_endbit   = zone_size;
+		dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS;
+		dm[zone].dm_bh       = sb_bread(sb, map_addr);
+
+		if (!dm[zone].dm_bh) {
+			adfs_error(sb, "unable to read map");
+			goto error_free;
+		}
+	}
+
+	/* adjust the limits for the first and last map zones */
+	i = zone - 1;
+	dm[0].dm_startblk = 0;
+	dm[0].dm_startbit = ADFS_DR_SIZE_BITS;
+	dm[i].dm_endbit   = (adfs_disc_size(dr) >> dr->log2bpmb) +
+			    (ADFS_DR_SIZE_BITS - i * zone_size);
+
+	if (adfs_checkmap(sb, dm))
+		return dm;
+
+	adfs_error(sb, "map corrupted");
+
+error_free:
+	while (--zone >= 0)
+		brelse(dm[zone].dm_bh);
+
+	kfree(dm);
+	return ERR_PTR(-EIO);
+}