Changes in uspace/srv/fs/fat/fat_fat.c [3a8faba:7efc517] in mainline

File:

• uspace/srv/fs/fat/fat_fat.c (modified) (7 diffs)

uspace/srv/fs/fat/fat_fat.c

@@ -46 +46 @@
 #include <align.h>
 #include <assert.h>
-#include <fibril_sync.h>
+#include <fibril_synch.h>
 #include <mem.h>
 
@@ -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)
@@ -398 +400 @@
                          * from the size of the file allocation table.
                          */
-                        if ((cl - 2) * bs->spc + ssa >= ts) {
+                        if ((cl >= 2) && ((cl - 2) * bs->spc + ssa >= ts)) {
                                 rc = block_put(blk);
                                 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;
@@ -606 +608 @@
 }
 
+/** 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.
+ */
+int fat_sanity_check(fat_bs_t *bs, dev_handle_t dev_handle)
+{
+        fat_cluster_t e0, e1;
+        unsigned fat_no;
+        int rc;
+
+        /* Check number of FATs. */
+        if (bs->fatcnt == 0)
+                return ENOTSUP;
+
+        /* Check total number of sectors. */
+
+        if (bs->totsec16 == 0 && bs->totsec32 == 0)
+                return ENOTSUP;
+
+        if (bs->totsec16 != 0 && bs->totsec32 != 0 &&
+            bs->totsec16 != bs->totsec32) 
+                return ENOTSUP;
+
+        /* Check media descriptor. Must be between 0xf0 and 0xff. */
+        if ((bs->mdesc & 0xf0) != 0xf0)
+                return ENOTSUP;
+
+        /* Check number of sectors per FAT. */
+        if (bs->sec_per_fat == 0)
+                return ENOTSUP;
+
+        /*
+         * Check that the root directory entries take up whole blocks.
+         * This check is rather strict, but it allows us to treat the root
+         * directory and non-root directories uniformly in some places.
+         * It can be removed provided that functions such as fat_read() are
+         * sanitized to support file systems with this property.
+         */
+        if ((uint16_t_le2host(bs->root_ent_max) * sizeof(fat_dentry_t)) %
+            uint16_t_le2host(bs->bps) != 0)
+                return ENOTSUP;
+
+        /* Check signature of each FAT. */
+
+        for (fat_no = 0; fat_no < bs->fatcnt; fat_no++) {
+                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;
+
+                /* Check that first byte of FAT contains the media descriptor. */
+                if ((e0 & 0xff) != bs->mdesc)
+                        return ENOTSUP;
+
+                /*
+                 * Check that remaining bits of the first two entries are
+                 * set to one.
+                 */
+                if ((e0 >> 8) != 0xff || e1 != 0xffff)
+                        return ENOTSUP;
+        }
+
+        return EOK;
+}
+
 /**
  * @}