Changeset dabe1664 in mainline

Timestamp:

2012-02-21T21:56:11Z (13 years ago)

Author:

Maurizio Lombardi <m.lombardi85@…>

Branches:

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

Children:

9587b37

Parents:

55dbaeb

Message:

mkexfat: Initialize the main extended boot sector and the checksum block

File:

• uspace/app/mkexfat/mkexfat.c (modified) (10 diffs)

uspace/app/mkexfat/mkexfat.c

@@ -56 +56 @@
 #define EBS_SECTOR_START 1
 
+/** First sector of the Main Extended Boot Region Backup */
+#define EBS_BACKUP_SECTOR_START 13
+
+/** First sector of the VBR */
+#define VBR_SECTOR 0
+
+/** First sector if the VBR Backup */
+#define VBR_BACKUP_SECTOR 12
+
 /** Size of the Main Extended Boot Region */
 #define EBS_SIZE 8
@@ -64 +73 @@
 /** The default size of each cluster is 4096 byte */
 #define DEFAULT_CLUSTER_SIZE 4096
-
-static unsigned log2(unsigned n);
 
 typedef struct exfat_cfg {
@@ -78 +85 @@
 } exfat_cfg_t;
 
+
+static unsigned log2(unsigned n);
+
+static uint32_t
+vbr_checksum_start(void const *octets, size_t nbytes);
+
+static void
+vbr_checksum_update(void const *octets, size_t nbytes, uint32_t *checksum);
+
+static int
+ebs_write(service_id_t service_id, exfat_cfg_t *cfg,
+    int base, uint32_t *chksum);
+
 static void usage(void)
 {
@@ -143 +163 @@
  * @param vbr Pointer to the Volume Boot Record structure.
  * @param cfg Pointer to the exFAT configuration structure.
- */
-static void
+ * @return    Initial checksum value.
+ */
+static uint32_t
 vbr_initialize(exfat_bs_t *vbr, exfat_cfg_t *cfg)
 {
@@ -182 +203 @@
         vbr->allocated_percent = 0;
         vbr->signature = host2uint16_t_le(0xAA55);
+
+        return vbr_checksum_start(vbr, sizeof(exfat_bs_t));
+}
+
+static int
+bootsec_write(service_id_t service_id, exfat_cfg_t *cfg)
+{
+        exfat_bs_t vbr;
+        uint32_t vbr_checksum;
+        uint32_t initial_checksum;
+        int rc;
+
+        vbr_checksum = vbr_initialize(&vbr, cfg);
+        initial_checksum = vbr_checksum;
+
+        /* Write the VBR on disk */
+        rc = block_write_direct(service_id, VBR_SECTOR, 1, &vbr);
+        if (rc != EOK)
+                return rc;
+
+        /* Write the VBR backup on disk */
+        rc = block_write_direct(service_id, VBR_BACKUP_SECTOR, 1, &vbr);
+        if (rc != EOK)
+                return rc;
+
+        rc = ebs_write(service_id, cfg, EBS_SECTOR_START, &vbr_checksum);
+        if (rc != EOK)
+                return rc;
+
+        /* Restore the checksum to its initial value */
+        vbr_checksum = initial_checksum;
+
+        return ebs_write(service_id, cfg, EBS_BACKUP_SECTOR_START, &vbr_checksum);
 }
 
@@ -188 +242 @@
  * @param service_id  The service id.
  * @param cfg  Pointer to the exFAT configuration structure.
+ * @param base Base sector of the EBS.
  * @return  EOK on success or a negative error code.
  */
 static int
-ebs_write(service_id_t service_id, exfat_cfg_t *cfg)
+ebs_write(service_id_t service_id, exfat_cfg_t *cfg, int base, uint32_t *chksum)
 {
         uint32_t *ebs = calloc(cfg->sector_size, sizeof(uint8_t));
         int i, rc;
+        unsigned idx;
 
         if (!ebs)
@@ -202 +258 @@
 
         for (i = 0; i < EBS_SIZE; ++i) {
-                rc = block_write_direct(service_id, i + EBS_SECTOR_START,
-                    1, ebs);
+                vbr_checksum_update(ebs, cfg->sector_size, chksum);
+
+                rc = block_write_direct(service_id,
+                    i + EBS_SECTOR_START + base, 1, ebs);
 
                 if (rc != EOK)
                         goto exit;
         }
+
+        /* The OEM record is not yet used
+         * by the official exFAT implementation, we'll fill
+         * it with zeroes.
+         */
+
+        memset(ebs, 0, cfg->sector_size);
+        vbr_checksum_update(ebs, cfg->sector_size, chksum);
+
+        rc = block_write_direct(service_id, i++ + base, 1, ebs);
+        if (rc != EOK)
+                goto exit;
+
+        /* The next sector is reserved, fill it with zeroes too */
+        vbr_checksum_update(ebs, cfg->sector_size, chksum);
+        rc = block_write_direct(service_id, i++ + base, 1, ebs);
+        if (rc != EOK)
+                goto exit;
+
+        /* Write the checksum sector */
+        for (idx = 0; idx < cfg->sector_size / sizeof(uint32_t); ++idx)
+                ebs[idx] = host2uint32_t_le(*chksum);
+
+        rc = block_write_direct(service_id, i + base, 1, ebs);
 
 exit:
@@ -251 +333 @@
 }
 
-/** Given a power-of-two number (n), returns the result of log2(n).
+/** Given a number (n), returns the result of log2(n).
  *
  * It works only if n is a power of two.
@@ -265 +347 @@
 }
 
+/** Initialize the VBR checksum calculation */
+static uint32_t
+vbr_checksum_start(void const *data, size_t nbytes)
+{
+        uint32_t checksum = 0;
+        size_t index;
+        uint8_t const *octets = (uint8_t *) data;
+
+        for (index = 0; index < nbytes; ++index) {
+                if (index == 106 || index == 107 || index == 112) {
+                        /* Skip volume_flags and allocated_percent fields */
+                        continue;
+                }
+
+                checksum = ((checksum << 31) | (checksum >> 1)) + octets[index];
+        }
+
+        return checksum;
+}
+
+/** Update the VBR checksum */
+static void
+vbr_checksum_update(void const *data, size_t nbytes, uint32_t *checksum)
+{
+        size_t index;
+        uint8_t const *octets = (uint8_t *) data;
+
+        for (index = 0; index < nbytes; ++index)
+                *checksum = ((*checksum << 31) | (*checksum >> 1)) + octets[index];
+}
+
 int main (int argc, char **argv)
 {
         exfat_cfg_t cfg;
-        exfat_bs_t  vbr;
         char *dev_path;
         service_id_t service_id;
@@ -323 +435 @@
         cfg_params_initialize(&cfg);
         cfg_print_info(&cfg);
-        vbr_initialize(&vbr, &cfg);
-
-        /* Write the VBR on disk */
-        rc = block_write_direct(service_id, 0, 1, &vbr);
-        if (rc != EOK) {
-                printf(NAME ": Error, failed to write the VBR on disk\n");
-                return 2;
-        }
-
-        /* Write the VBR backup on disk */
-        rc = block_write_direct(service_id, 12, 1, &vbr);
-        if (rc != EOK) {
-                printf(NAME ": Error, failed to write the VBR" \
-                    " backup on disk\n");
-                return 2;
-        }
-
-        rc = ebs_write(service_id, &cfg);
-        if (rc != EOK) {
-                printf(NAME ": Error, failed to write the Main Extended Boot" \
-                    " Sector to disk\n");
+
+        rc = bootsec_write(service_id, &cfg);
+        if (rc != EOK) {
+                printf(NAME ": Error, failed to write the VBR to disk\n");
                 return 2;
         }