Changeset 711e1f32 in mainline

Timestamp:

2010-01-13T21:33:58Z (15 years ago)

Author:

Jiri Svoboda <jiri@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

2ffaab5, 990c70e

Parents:

65737d4

Message:

Do some sanity checks when mounting a fat file system.

Location:

uspace/srv/fs/fat

Files:

• fat_fat.c (modified) (4 diffs)
• fat_fat.h (modified) (1 diff)
• fat_ops.c (modified) (2 diffs)

uspace/srv/fs/fat/fat_fat.c

@@ -247 +247 @@
  */
 int
-fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst,
-    fat_cluster_t *value)
+fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
+    fat_cluster_t clst, fat_cluster_t *value)
 {
         block_t *b;
         uint16_t bps;
         uint16_t rscnt;
+        uint16_t sf;
         fat_cluster_t *cp;
         int rc;
@@ -258 +259 @@
         bps = uint16_t_le2host(bs->bps);
         rscnt = uint16_t_le2host(bs->rscnt);
-
-        rc = block_get(&b, dev_handle, rscnt +
+        sf = uint16_t_le2host(bs->sec_per_fat);
+
+        rc = block_get(&b, dev_handle, rscnt + sf * fatno +
             (clst * sizeof(fat_cluster_t)) / bps, BLOCK_FLAGS_NONE);
         if (rc != EOK)
@@ -480 +482 @@
         while (firstc < FAT_CLST_LAST1) {
                 assert(firstc >= FAT_CLST_FIRST && firstc < FAT_CLST_BAD);
-                rc = fat_get_cluster(bs, dev_handle, firstc, &nextc);
+                rc = fat_get_cluster(bs, dev_handle, FAT1, firstc, &nextc);
                 if (rc != EOK)
                         return rc;
@@ -560 +562 @@
                 unsigned fatno;
 
-                rc = fat_get_cluster(bs, dev_handle, lastc, &nextc);
+                rc = fat_get_cluster(bs, dev_handle, FAT1, lastc, &nextc);
                 if (rc != EOK)
                         return rc;

uspace/srv/fs/fat/fat_fat.h

@@ -80 +80 @@
 extern int fat_alloc_shadow_clusters(struct fat_bs *, dev_handle_t,
     fat_cluster_t *, unsigned);
-extern int fat_get_cluster(struct fat_bs *, dev_handle_t, fat_cluster_t,
-    fat_cluster_t *);
+extern int fat_get_cluster(struct fat_bs *, dev_handle_t, unsigned,
+    fat_cluster_t, fat_cluster_t *);
 extern int fat_set_cluster(struct fat_bs *, dev_handle_t, unsigned,
     fat_cluster_t, fat_cluster_t);

uspace/srv/fs/fat/fat_ops.c

@@ -290 +290 @@
 
         *nodepp = nodep;
+        return EOK;
+}
+
+/** Perform basic sanity checks on the file system.
+ *
+ * Verify if values of boot sector fields are sane. Also verify media
+ * descriptor. This is used to rule out cases when a device obviously
+ * does not contain a fat file system.
+ */
+static int fat_sanity_check(fat_bs_t *bs, dev_handle_t dev_handle)
+{
+        fat_cluster_t e0, e1;
+        unsigned fat_no;
+        int rc;
+
+        printf("fatcnt\n");
+        /* Check number of FATs. */
+        if (bs->fatcnt == 0)
+                return ENOTSUP;
+
+        /* Check total number of sectors. */
+
+        printf("totsec\n");
+        if (bs->totsec16 == 0 && bs->totsec32 == 0)
+                return ENOTSUP;
+
+        if (bs->totsec16 != 0 && bs->totsec32 != 0 &&
+            bs->totsec16 != bs->totsec32) 
+                return ENOTSUP;
+
+        printf("mdesc\n");
+        /* Check media descriptor. Must be between 0xf0 and 0xff. */
+        if ((bs->mdesc & 0xf0) != 0xf0)
+                return ENOTSUP;
+
+        printf("sec_per_fat\n");
+        /* Check number of sectors per FAT. */
+        if (bs->sec_per_fat == 0)
+                return ENOTSUP;
+
+        /* Check signature of each FAT. */
+
+        for (fat_no = 0; fat_no < bs->fatcnt; fat_no++) {
+                printf("clst-read\n");
+                rc = fat_get_cluster(bs, dev_handle, fat_no, 0, &e0);
+                if (rc != EOK)
+                        return EIO;
+
+                rc = fat_get_cluster(bs, dev_handle, fat_no, 1, &e1);
+                if (rc != EOK)
+                        return EIO;
+
+                printf("mdesc-fat\n");
+                /* Check that first byte of FAT contains the media descriptor. */
+                if ((e0 & 0xff) != bs->mdesc)
+                        return ENOTSUP;
+
+                printf("fat-signat\n");
+                /*
+                 * Check that remaining bits of the first two entries are
+                 * set to one.
+                 */
+                if ((e0 >> 8) != 0xff || e1 != 0xffff)
+                        return ENOTSUP;
+        }
+
         return EOK;
 }
@@ -981 +1047 @@
         }
 
+        /* Do some simple sanity checks on the boot blocks. */
+        rc = fat_sanity_check(bs, dev_handle);
+        if (rc != EOK) {
+                block_fini(dev_handle);
+                ipc_answer_0(rid, rc);
+                return;
+        }
+
         rc = fat_idx_init_by_dev_handle(dev_handle);
         if (rc != EOK) {