chain: Allow booting the Syslinux partition with "fs"

We will now accept an "fs" option which instructs us to
chain-load whatever partition we were booted from.  Not
useful for PXELINUX, for obvious reasons.  Can be used
in combination with a "file=" option, to boot something
other than Syslinux.

Signed-off-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>

diff --git a/NEWS b/NEWS
index d3f43ca..fdf33cf 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,7 @@ to all derivatives.
 
 Changes in 4.00:
        * chain.c32: support booting GPT partitions by index
+       * chain.c32: support booting the Syslinux partition with "fs"
 Changes in 3.86:
        * chain.c32: fix chainloading the MBR of a hard disk (broken
          in 3.85).

diff --git a/com32/modules/chain.c b/com32/modules/chain.c
index 97a7086..2652de8 100644 (file)
--- a/com32/modules/chain.c
+++ b/com32/modules/chain.c
@@ -3,7 +3,7 @@
  *   Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
  *   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
  *   Significant portions copyright (C) 2010 Shao Miller
- *                                     [partition iteration, GPT]
+ *                                     [partition iteration, GPT, "fs"]
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -28,7 +28,7 @@
  * filesystem.  "chain hd0 1" will boot the first partition on the first hard
  * disk.
  *
- * When none of the "hdX", "fdX", "mbr:" or "boot" options are specified,
+ * When none of the "hdX", "fdX", "mbr:", "boot" or "fs" options are specified,
  * the default behaviour is equivalent to "boot".  "boot" means to use the
  * current Syslinux drive, and you can also specify a partition.
  *
@@ -37,6 +37,9 @@
  *
  * Partitions 1-4 are primary, 5+ logical, 0 = boot MBR (default.)
  *
+ * "fs" will use the current Syslinux filesystem as the boot drive/partition.
+ * When booting from PXELINUX, you will most likely wish to specify a disk.
+ *
  * Options:
  *
  * file=<loader>:
@@ -1080,6 +1083,7 @@ Usage:   chain.c32 [options]\n\
          chain.c32 fd<disk#> [options]\n\
          chain.c32 mbr:<id> [<partition>] [options]\n\
          chain.c32 boot [<partition>] [options]\n\
+         chain.c32 fs [options]\n\
 Options: file=<loader>      Load and execute file, instead of boot sector\n\
          isolinux=<loader>  Load another version of ISOLINUX\n\
          ntldr=<loader>     Load Windows NTLDR, SETUPLDR.BIN or BOOTMGR\n\
@@ -1103,8 +1107,9 @@ int main(int argc, char *argv[])
     struct disk_part_iter *cur_part = NULL;
     struct syslinux_rm_regs regs;
     char *drivename, *partition;
-    int hd, drive, whichpart;
+    int hd, drive, whichpart = 0;      /* MBR by default */
     int i;
+    uint64_t fs_lba = 0;       /* Syslinux partition */
     uint32_t file_lba = 0;
     unsigned char *isolinux_bin;
     uint32_t *checksum, *chkhead, *chktail;
@@ -1175,7 +1180,8 @@ int main(int argc, char *argv[])
                   || !strncmp(argv[i], "mbr:", 4)
                   || !strncmp(argv[i], "mbr=", 4)
                   || !strcmp(argv[i], "boot")
-                  || !strncmp(argv[i], "boot,", 5)) {
+                  || !strncmp(argv[i], "boot,", 5)
+                  || !strncmp(argv[i], "fs", 2)) {
            drivename = argv[i];
            p = strchr(drivename, ',');
            if (p) {
@@ -1209,13 +1215,19 @@ int main(int argc, char *argv[])
        hd = drivename[0] == 'h';
        drivename += 2;
        drive = (hd ? 0x80 : 0) | strtoul(drivename, NULL, 0);
-    } else if (!strcmp(drivename, "boot")) {
+    } else if (!strcmp(drivename, "boot") || !strcmp(drivename, "fs")) {
        const union syslinux_derivative_info *sdi;
+
        sdi = syslinux_derivative_info();
        if (sdi->c.filesystem == SYSLINUX_FS_PXELINUX)
            drive = 0x80;       /* Boot drive not available */
        else
            drive = sdi->disk.drive_number;
+       if (!strcmp(drivename, "fs")
+           && (sdi->c.filesystem == SYSLINUX_FS_SYSLINUX
+               || sdi->c.filesystem == SYSLINUX_FS_EXTLINUX))
+           /* We should lookup the Syslinux partition number and use it */
+           fs_lba = ((struct part_entry *)sdi->disk.ptab_ptr)->start_lba;
     } else {
        error("Unparsable drive specification\n");
        goto bail;
@@ -1224,22 +1236,6 @@ int main(int argc, char *argv[])
     /* DOS kernels want the drive number in BL instead of DL.  Indulge them. */
     regs.ebx.b[0] = regs.edx.b[0] = drive;
 
-    whichpart = 0;             /* Default */
-    if (partition)
-       whichpart = strtoul(partition, NULL, 0);
-
-    if (!(drive & 0x80) && whichpart) {
-       error("Warning: Partitions of floppy devices may not work\n");
-    }
-
-    /* 
-     * GRLDR of GRUB4DOS wants the partition number in DH:
-     * -1:   whole drive (default)
-     * 0-3:  primary partitions
-     * 4-*:  logical partitions
-     */
-    regs.edx.b[1] = whichpart - 1;
-
     /* Get the disk geometry and disk access setup */
     if (get_disk_params(drive)) {
        error("Cannot get disk parameters\n");
@@ -1248,23 +1244,20 @@ int main(int argc, char *argv[])
 
     /* Get MBR */
     if (!(mbr = read_sectors(0, 1))) {
-       error("Cannot read Master Boot Record\n");
+       error("Cannot read Master Boot Record or sector 0\n");
        goto bail;
     }
 
-    if (opt.hide) {
-       if (whichpart < 1 || whichpart > 4)
-           error("WARNING: hide specified without a non-primary partition\n");
-       if (hide_unhide(mbr, whichpart))
-           error("WARNING: failed to write MBR for 'hide'\n");
-    }
+    if (partition)
+       whichpart = strtoul(partition, NULL, 0);
 
     /* Boot the MBR by default */
-    if (whichpart) {
-       /* Boot a partition */
+    if (whichpart || fs_lba) {
+       /* Boot a partition, possibly the Syslinux partition itself */
        cur_part = get_first_partition(NULL);
        while (cur_part) {
-           if (cur_part->index == whichpart)
+           if ((cur_part->index == whichpart)
+               || (cur_part->lba_data == fs_lba))
                /* Found the partition to boot */
                break;
            cur_part = cur_part->next(cur_part);
@@ -1273,6 +1266,26 @@ int main(int argc, char *argv[])
            error("Requested partition not found!\n");
            goto bail;
        }
+       whichpart = cur_part->index;
+    }
+
+    if (!(drive & 0x80) && whichpart) {
+       error("Warning: Partitions of floppy devices may not work\n");
+    }
+
+    /* 
+     * GRLDR of GRUB4DOS wants the partition number in DH:
+     * -1:   whole drive (default)
+     * 0-3:  primary partitions
+     * 4-*:  logical partitions
+     */
+    regs.edx.b[1] = whichpart - 1;
+
+    if (opt.hide) {
+       if (whichpart < 1 || whichpart > 4)
+           error("WARNING: hide specified without a non-primary partition\n");
+       if (hide_unhide(mbr, whichpart))
+           error("WARNING: failed to write MBR for 'hide'\n");
     }
 
     /* Do the actual chainloading */