From 12e4b1c978975d8cb6f3e13f20b1dbb136166b41 Mon Sep 17 00:00:00 2001
From: Sebastian Schmelzer
Date: Mon, 14 Mar 2011 17:51:16 +0100
Subject: initial commit

---
 .../syslinux-4.03/com32/gpllib/disk/msdos.c        | 162 +++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 contrib/syslinux/syslinux-4.03/com32/gpllib/disk/msdos.c

(limited to 'contrib/syslinux/syslinux-4.03/com32/gpllib/disk/msdos.c')

diff --git a/contrib/syslinux/syslinux-4.03/com32/gpllib/disk/msdos.c b/contrib/syslinux/syslinux-4.03/com32/gpllib/disk/msdos.c
new file mode 100644
index 0000000..affec43
--- /dev/null
+++ b/contrib/syslinux/syslinux-4.03/com32/gpllib/disk/msdos.c
@@ -0,0 +1,162 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2009 Pierre-Alexandre Meyer
+ *
+ *   Some parts borrowed from chain.c32:
+ *
+ *   Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
+ *
+ *   This file is part of Syslinux, and is made available under
+ *   the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+#include <stdlib.h>
+
+#include <disk/common.h>
+#include <disk/geom.h>
+#include <disk/msdos.h>
+#include <disk/partition.h>
+#include <disk/read.h>
+
+static inline int is_extended_partition(struct part_entry *ptab)
+{
+    return (ptab->ostype == 0x05 ||
+	    ptab->ostype == 0x0f || ptab->ostype == 0x85);
+}
+
+static inline int msdos_magic_present(const char *ptab)
+{
+    return (*(uint16_t *) (ptab + 0x1fe) == 0xaa55);
+}
+
+/**
+ * process_extended_partition - execute a callback for each partition contained listed in an ebr
+ * @drive_info:		driveinfo struct describing the drive
+ * @partition_offset:	Absolute start (lba) of the extended partition
+ * @ebr_offset:		Relative start (lba) of the current ebr processed within
+ *			the extended partition
+ * @callback:		Callback to execute
+ * @error:		Buffer for I/O errors
+ * @nb_part_seen:	Number of partitions found on the disk so far
+ **/
+static int process_extended_partition(struct driveinfo *drive_info,
+				      const int partition_offset,
+				      const int ebr_offset,
+				      p_callback callback, int nb_part_seen)
+{
+    int status = 0;
+    /* The ebr is located at the first sector of the extended partition */
+    char *ebr = malloc(SECTOR * sizeof(char));
+
+    if (read_sectors(drive_info, ebr, partition_offset + ebr_offset, 1) == -1)
+	goto abort;
+
+    /* Check msdos magic signature */
+    if (!msdos_magic_present(ebr))
+	goto abort;
+
+    struct part_entry *ptab =
+	(struct part_entry *)(ebr + PARTITION_TABLES_OFFSET);
+
+    for (int i = 0; i < 4; i++) {
+	if (status == -1)
+	    goto abort;
+
+	if (!is_extended_partition(&ptab[i])) {
+	    /*
+	     * This EBR partition table entry points to the
+	     * logical partition associated to that EBR
+	     */
+	    int logical_partition_start = ebr_offset + ptab[i].start_lba;
+
+	    /* Last EBR in the extended partition? */
+	    if (!logical_partition_start)
+		continue;
+
+	    /*
+	     * Check for garbage:
+	     * 3rd and 4th entries in an EBR should be zero
+	     * Some (malformed) partitioning software still add some
+	     * data partitions there.
+	     */
+	    if (ptab[i].start_lba <= 0 || ptab[i].length <= 0)
+		continue;
+
+	    nb_part_seen++;
+	    callback(drive_info,
+		     &ptab[i],
+		     partition_offset + logical_partition_start, nb_part_seen);
+	} else
+	    status = process_extended_partition(drive_info,
+						partition_offset,
+						ptab[i].start_lba,
+						callback, nb_part_seen);
+    }
+
+    free(ebr);
+    return 0;
+
+abort:
+    free(ebr);
+    return -1;
+}
+
+/**
+ * process_mbr - execute a callback for each partition contained in an {m,e}br
+ * @drive_info:	driveinfo struct describing the drive
+ * @ptab:	Pointer to the partition table
+ * @callback:	Callback to execute
+ **/
+static int process_mbr(struct driveinfo *drive_info, struct part_entry *ptab,
+		       p_callback callback)
+{
+    int status = 0;
+
+    for (int i = 0; i < 4; i++) {
+	if (status == -1)
+	    return -1;
+
+	if (ptab[i].start_sect > 0) {
+	    if (is_extended_partition(&ptab[i])) {
+		callback(drive_info, &ptab[i], ptab[i].start_lba, i + 1);
+		status =
+		    process_extended_partition(drive_info, ptab[i].start_lba, 0,
+					       callback, 4);
+	    } else
+		callback(drive_info, &ptab[i], ptab[i].start_lba, i + 1);
+	}
+    }
+
+    return 0;
+}
+
+/**
+ * parse_partition_table - execute a callback for each partition entry
+ * @d:		driveinfo struct describing the drive
+ * @callback:	Callback to execute
+ *
+ * The signature of the callback should be the following:
+ *
+ * void callback(struct driveinfo *drive_info,
+ *		 struct part_entry *ptab,
+ *		 int offset_root,
+ *		 int nb_part_seen)
+ **/
+int parse_partition_table(struct driveinfo *d, p_callback callback)
+{
+    char *mbr = malloc(SECTOR * sizeof(char));
+
+    if (read_mbr(d->disk, mbr) == -1)
+	return -1;
+    else {
+	/* Check msdos magic signature */
+	if (!msdos_magic_present(mbr))
+	    return -1;
+
+	struct part_entry *ptab =
+	    (struct part_entry *)(mbr + PARTITION_TABLES_OFFSET);
+	return process_mbr(d, ptab, callback);
+    }
+}
-- 
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