Support for writing MBR in the system area, to make hybrid boot images.

With the specified isolinux option, a MBR is written to the system area, and this 
allows the image to boot from either CD/DVD or USB sticks.

This is also supported on overwriteable media (note that system area is always
overwritten), but it should not work on multisession media.

Makefile.am

@@ -52,6 +52,8 @@ libisofs_libisofs_la_SOURCES = \
 	libisofs/joliet.c \
 	libisofs/eltorito.h \
 	libisofs/eltorito.c \
+	libisofs/system_area.h \
+	libisofs/system_area.c \
 	libisofs/make_isohybrid_mbr.c \
 	libisofs/iso1999.h \
 	libisofs/iso1999.c \

libisofs/ecma119.c

@@ -19,6 +19,7 @@
 #include "messages.h"
 #include "rockridge.h"
 #include "util.h"
+#include "system_area.h"
 
 #include "libburn/libburn.h"
 
@@ -784,10 +785,14 @@ void *write_function(void *arg)
     target->bytes_written = (off_t) 0;
     target->percent_written = 0;
 
-    /* Write System Area, 16 blocks of zeros (ECMA-119, 6.2.1) */
-    memset(buf, 0, BLOCK_SIZE);
-    for (i = 0; i < 16; ++i) {
-        res = iso_write(target, buf, BLOCK_SIZE);
+    /* Write System Area (ECMA-119, 6.2.1) */
+    {
+        uint8_t sa[16 * BLOCK_SIZE];
+        res = iso_write_system_area(target, sa);
+        if (res < 0) {
+            goto write_error;
+        }
+        res = iso_write(target, sa, 16 * BLOCK_SIZE);
         if (res < 0) {
             goto write_error;
         }
@@ -1054,6 +1059,14 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
             }
         }
 
+        /* write the system area */
+        ret = iso_write_system_area(target, opts->overwrite);
+        if (ret < 0) {
+            iso_msg_debug(target->image->id,
+                          "Error writing system area to overwrite buffer");
+            goto target_cleanup;
+        }
+
         /* skip the first 16 blocks (system area) */
         buf = opts->overwrite + 16 * BLOCK_SIZE;
         voldesc_size *= BLOCK_SIZE;

libisofs/eltorito.h

@@ -35,7 +35,12 @@ struct el_torito_boot_image {
     IsoFile *image;
 
     unsigned int bootable:1; /**< If the entry is bootable. */
-    unsigned int isolinux:1; /**< If the image will be patched */
+    /**
+     * isolinux options
+     * bit 0 -> whether to patch image
+     * bit 1 -> whether to create isolinux image
+     */
+    unsigned int isolinux_options:2;
     unsigned char type; /**< The type of image */
     unsigned char partition_type; /**< type of partition for HD-emul images */
     short load_seg; /**< Load segment for the initial boot image. */
@@ -100,21 +105,4 @@ int el_torito_catalog_file_src_create(Ecma119Image *target, IsoFileSrc **src);
  */
 int eltorito_writer_create(Ecma119Image *target);
 
-/*
- * Create a MBR for an isohybrid enabled ISOLINUX boot image.
- *
- * It is assumed that the caller has verified the readiness of the boot image
- * by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin.
- *
- * @param bin_lba    The predicted LBA of isolinux.bin within the emerging ISO.
- * @param img_blocks The predicted number of 2048 byte blocks in the ISO.
- *                   It will get rounded up to full MBs and that many blocks
- *                   must really be written as ISO 9660 image.
- * @param mbr        A buffer of at least 512 bytes to take the result which is
- *                   to be written as the very beginning of the ISO.
- * @param flag    unused yet, submit 0
- * @return  <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning
- */
-int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
-
 #endif /* LIBISO_ELTORITO_H */

libisofs/system_area.c

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2008 Vreixo Formoso
+ *
+ * This file is part of the libisofs project; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation. See COPYING file for details.
+ */
+
+#include "system_area.h"
+#include "eltorito.h"
+#include "filesrc.h"
+
+#include <string.h>
+
+
+
+/*
+ * Create a MBR for an isohybrid enabled ISOLINUX boot image.
+ *
+ * It is assumed that the caller has verified the readiness of the boot image
+ * by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin.
+ *
+ * @param bin_lba    The predicted LBA of isolinux.bin within the emerging ISO.
+ * @param img_blocks The predicted number of 2048 byte blocks in the ISO.
+ *                   It will get rounded up to full MBs and that many blocks
+ *                   must really be written as ISO 9660 image.
+ * @param mbr        A buffer of at least 512 bytes to take the result which is
+ *                   to be written as the very beginning of the ISO.
+ * @param flag    unused yet, submit 0
+ * @return  <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning
+ */
+int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
+
+int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
+{
+    if ((t == NULL) || (buf == NULL)) {
+        return ISO_NULL_POINTER;
+    }
+
+    /* set buf to 0s */
+    memset(buf, 0, 16 * BLOCK_SIZE);
+
+    if (t->catalog != NULL && t->catalog->image->isolinux_options & 0x02) {
+        /* We need to write a MBR for an hybrid image */
+        int ret;
+        int img_blocks;
+
+        img_blocks = t->curblock;
+        ret = make_isohybrid_mbr(t->bootimg->sections[0].block, &img_blocks, (char*)buf, 0);
+
+        // FIXME the new img_blocks size should be taken into account
+
+        if (ret != 1) {
+            /* error, it should never happen */
+            return ISO_ASSERT_FAILURE;
+        }
+    }
+    return ISO_SUCCESS;
+}

libisofs/system_area.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2008 Vreixo Formoso
+ *
+ * This file is part of the libisofs project; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation. See COPYING file for details.
+ */
+
+/*
+ * Functions for dealing with the system area, this is, the first 16 blocks
+ * of the image.
+ *
+ * At this time, this is only used for hybrid boot images with isolinux.
+ */
+
+#ifndef SYSTEM_AREA_H_
+#define SYSTEM_AREA_H_
+
+#include "ecma119.h"
+
+/*
+ * Create a MBR for an isohybrid enabled ISOLINUX boot image.
+ *
+ * It is assumed that the caller has verified the readiness of the boot image
+ * by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin.
+ *
+ * @param bin_lba    The predicted LBA of isolinux.bin within the emerging ISO.
+ * @param img_blocks The predicted number of 2048 byte blocks in the ISO.
+ *                   It will get rounded up to full MBs and that many blocks
+ *                   must really be written as ISO 9660 image.
+ * @param mbr        A buffer of at least 512 bytes to take the result which is
+ *                   to be written as the very beginning of the ISO.
+ * @param flag    unused yet, submit 0
+ * @return  <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning
+ */
+int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
+
+/**
+ * Write the system area for the given image to the given buffer.
+ *
+ * @param buf
+ *      A buffer with at least 32 K allocated
+ * @return
+ *      1 if success, < 0 on error
+ */
+int iso_write_system_area(Ecma119Image *t, uint8_t *buf);
+
+#endif /* SYSTEM_AREA_H_ */