Syslinux - Oct 2007 - Adding a "boot from local hard disk" option to syslinux menu, booted from USB

Hi all, 

I use XP on my laptop PC, with 30 GB HD (single
partition), and a 3.5" hard drive (not a stick),
accessed through a USB encasing, partitioned as five
logical drives. 

I have successfully set up syslinux to boot several
Ubuntu versions from the primary USB hard drive
partition, and no problems there. The problem is, I
would like to have an entry in the menu, like "Boot
from first hard disk", in which case, I would boot XP
from the laptop hard drive. 

I'm not very knowledgeable about booting, but I read
that I would have to chainload, so I tried to use
chain.c32 and the following entries: 

LABEL hd
  menu label ^hd - boot IDE0 hd0 0
  kernel chain.c32
  append hd0 0
  
and 

LABEL hd2
  menu label ^Boot from first hard disk
  localboot 0x80
  append -

but unfortunately nothing seems to happen (the first
option says "illegal argument" or something, exits and
shows boot menu again, the other simply show the boot
menu again) - it seems as if chain.c32 interprets "hd0
0" to be a partition on the USB hard drive, instead of
the local one? 

I tried to modify the source code of chain.c32 (the
function is included below, compiled through
DSL-embedded, with gcc package) where I tried to scan
through possible hard disks (that is, loop through
drive and partition indexes) and print out info, in
hope that I'd spot the main (C) drive on the laptop.
But apart from the USB drive itself, nothing seems to
have an MBR, no matter how much I look? (it could be
easier if I could save a text report, but the file
open operation fails - I'm guessing because at the
moment, it is not known what the default drive is??).

Well, in any case, I would really appreciate if
someone can let me know if what I want to do is
possible at all with syslinux; and possibly how to do
it... 

Thanks,
Cheers


///


int main(int argc, char *argv[])
{
  char *mbr, *boot_sector = NULL;
  struct part_entry *partinfo;
  char *drivename, *partition, *endds, *endps,
*waittotals;
  int hd, drive, whichpart;
  static com32sys_t inreg;	/* In bss, so zeroed
automatically */
  int idd, idp, endd, endp; 
  FILE *f;
  char *log = "/chsdlog.txt";
  char logsc[1024];
  char *logs = &logsc;
  char logrc[10240];
  char *logr = &logrc;
  char inch[20];
  int ix = 0; 
  int waittotal; 
  char cc; 
  FILE *pFile = NULL;
  
  openconsole(&dev_null_r, &dev_stdcon_w);

  /*if ( argc < 2 ) {
    error("Usage: chain.c32 (hd|fd)# [partition]\n");
    goto bail;
  }*/

  strcpy (logrc, "Log: ");
  sprintf(logs, "Starting chainsd - chain see disk
only.\n");
  printf(logs);
  
  strcat(logrc, logs);
  
	  //drivename = argv[1];
	  //partition = argv[2];		/* Possibly null */

  endds = argv[1];
  endps = argv[2];		/* Possibly null */
  waittotals = argv[3];		/* Possibly null */

  if ( endds )
	endd = strtoul(endds, NULL, 0);
  else endd = 1; 

  if ( endps )
	endp = strtoul(endps, NULL, 0);
  else endp = 3; 
  
  if ( waittotals )
	waittotal = strtoul(waittotals, NULL, 0);
  else waittotal = 500;   
  
  sprintf(logs, "Probing hard disks: %d first disks -
%d first partitions each\n", endd, endp);
  printf(logs);
  strcat(logrc, logs);
  
  drivename = "hd0";
  partition = "0";
  
  // loop through drives and partitions
  for (idd=0; idd<=endd; idd++)
   for (idp=0; idp<=endp; idp++)
  {
	  //partition = NULL; 
	  
	  drivename[2] = 48+idd; //ascii 0 or 1
	  partition[0] = 48+idp;
	  
	  sprintf(logs, "Current: drivename %s, partition %s,
idd %d, idp %d\n", drivename, partition, idd, idp);
	  
	  printf(logs);
	  strcat(logrc, logs);	  
	  
	  hd = 0;
	  if ( (drivename[0] == 'h' || drivename[0] == 'f')
&&
		   drivename[1] == 'd' ) {
		hd = drivename[0] == 'h';
		drivename += 2;
	  }
	  drive = (hd ? 0x80 : 0) | strtoul(drivename, NULL,
0);
	  //whichpart = 0;		/* Default */
	  //whichpart = ip;
	
	  if ( partition )
		whichpart = strtoul(partition, NULL, 0);
	
	  if ( !(drive & 0x80) && whichpart ) {
		//error();
		  sprintf(logs, "Warning: Partitions of floppy
devices may not work\n");
		  error(logs);
		  strcat(logrc, logs);

	  }
	  
	  
	  sprintf(logs, "Current: %s, whichpart(ition) %d,
drive %d\n", drivename, whichpart, drive);
	  printf(logs);
	  strcat(logrc, logs);
		  
	  /* Divvy up the bounce buffer.  To keep things
sector-
		 aligned, give the EBIOS DAPA the first sector, then
		 the MBR next, and the rest is used for the
partition-
		 chasing stack. */
	  dapa = (struct ebios_dapa *)__com32.cs_bounce;
	  mbr  = (char *)__com32.cs_bounce + SECTOR;
	
	  /* Get the disk geometry (not needed for MBR) */

	  sprintf(logs, "Get the disk geometry - Calling
get_disk_params\n");
	  printf(logs);
	  strcat(logrc, logs);
	  
	  if ( get_disk_params(drive) && whichpart ) {
		//error();
		  sprintf(logs, "Cannot get disk parameters\n");
		  error(logs);
		  strcat(logrc, logs);
		goto endloop;
	  }
	
  	 
	  sprintf(logs, "disk_info: disk %d, ebios %d, cbios
%d, head %d, sect %d\n", disk_info.disk,
disk_info.ebios, disk_info.cbios, disk_info.head,
disk_info.sect);
	  printf(logs);
	  strcat(logrc, logs);
	  
	  /* Get MBR */
	  sprintf(logs, "Get MBR - Calling read_sector\n");
	  printf(logs);
	  strcat(logrc, logs);
	  
	  if ( read_sector(mbr, 0) ) {
		//error();
		  sprintf(logs, "Cannot read Master Boot Record\n");
		  error(logs);
			strcat(logrc, logs);		
		goto endloop;
	  }
	
	  sprintf(logs, "mbr: %s ...\n", mbr);
	  printf(logs);
	  strcat(logrc, logs);
	  
	  if ( whichpart == 0 ) {
		/* Boot the MBR */

		  sprintf(logs, "whichpart == 0 Boot the MBR\n");
		  printf(logs);
		  strcat(logrc, logs);
		
		partinfo = NULL;
		boot_sector = mbr;
	  } else if ( whichpart <= 4 ) {
		/* Boot a primary partition */

		  sprintf(logs, "whichpart <= 4 Boot a primary
partition\n");
		  printf(logs);
		  strcat(logrc, logs);
		
		partinfo = &((struct part_entry *)(mbr +
0x1be))[whichpart-1];
		if ( partinfo->ostype == 0 ) {
		  //error();
		  sprintf(logs, "Invalid primary partition\n");
		  error(logs);
		  strcat(logrc, logs);
		  		  
		  goto endloop;
		}
	  } else {
		/* Boot a logical partition */

		  sprintf(logs, "whichpart > 4 Boot a logical
partition \n");
		  printf(logs);
		  strcat(logrc, logs);
		
		nextpart = 5;
		partinfo = find_logical_partition(whichpart, mbr,
NULL, NULL);
	
		if ( !partinfo || partinfo->ostype == 0 ) {
		  //error();

		  sprintf(logs, "Requested logical partition not
found\n");
		  error(logs);
		  strcat(logrc, logs);
		  
		  goto endloop;
		}
	  }


	  /* Do the actual chainloading */
	  if ( partinfo ) {
		/* Actually read the boot sector */
		/* Pick the first buffer that isn't already in use
*/

		boot_sector = (char *)(((unsigned long)partinfo +
511) & ~511);
		
		  sprintf(logs, "partinfo: active_flag %d,
start_head %d, start_sect %d, start_cyl %d, ostype %d,
end_head %d, end_sect %d, end_cyl %d, start_lba %d,
length %d, boot_sector %s\n", partinfo->active_flag,
partinfo->start_head, partinfo->start_sect,
partinfo->start_cyl, partinfo->ostype,
partinfo->end_head, partinfo->end_sect,
partinfo->end_cyl, partinfo->start_lba,
partinfo->length, boot_sector);
		  printf(logs);
			strcat(logrc, logs);		
		
		
		if ( read_sector(boot_sector, partinfo->start_lba) )
{
		  //error();
		  sprintf(logs, "Cannot read boot sector\n");
		  error(logs);
		  strcat(logrc, logs);
		  
		  goto endloop;
		}
	
		/* 0x7BE is the canonical place for the first
partition entry. */
		inreg.esi.w[0] = 0x7be;
		memcpy((char *)0x7be, partinfo, sizeof(*partinfo));
	  }
  
  printf("NO Press dot . -waiting 100000 ticks\n\n");

  
  endloop:
   
  // cannot find a way to wait for a keypress, so this
way to make a pause
  ix = 0; 
  while (ix < waittotal)
  { printf("\r%d/%d waiting ticks.. ", ix, waittotal);
	ix += 1; }
  printf("\n\n");

  } //end for loops
  
  fputs("Booting...not\n", stdout);

  pFile = fopen("chreport.txt", "a");
  if(pFile == NULL)
  {
    printf("Error opening for writing. Program
terminated.");
    abort();
  }
  else
  {
	fprintf(pFile, logrc);
	fclose(pFile);
  }
  //inreg.eax.w[0] = 0x000d;	/* Clean up and chain
boot */
  //inreg.edx.w[0] = 0;		/* Should be 3 for "keeppxe"
*/
  //inreg.edi.l    = (uint32_t)boot_sector;
  //inreg.ecx.l    = SECTOR;	/* One sector */
  //inreg.ebx.b[0] = drive;	/* DL = drive no */

  //__intcall(0x22, &inreg, NULL);

  /* If we get here, badness happened */
  /*f = fopen(log, "wb");
  fwrite(logr, sizeof(char), strlen(logr), f);
  fclose(f);*/
  
  error("Chainboot failed! not - all fine, come to
end... \n");

bail:
  return 255;
}


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bobby digital wrote:
> I use XP on my laptop PC, with 30 GB HD (single
> partition), and a 3.5" hard drive (not a stick),
> accessed through a USB encasing, partitioned as five
> logical drives. 
> 
> I have successfully set up syslinux to boot several
> Ubuntu versions from the primary USB hard drive
> partition, and no problems there. The problem is, I
> would like to have an entry in the menu, like "Boot
> from first hard disk", in which case, I would boot XP
> from the laptop hard drive. 
The "first" drive -- as seen be your BIOS -- when booting from
a USB disk or stick, isn't your laptop's HD but the USB disk/stick.

... otherwise it would have booted from the laptop's HD.

- Axel

bobby digital wrote:
> Hi all, 
> 
> I use XP on my laptop PC, with 30 GB HD (single
> partition), and a 3.5" hard drive (not a stick),
> accessed through a USB encasing, partitioned as five
> logical drives. 
> 
> I have successfully set up syslinux to boot several
> Ubuntu versions from the primary USB hard drive
> partition, and no problems there. The problem is, I
> would like to have an entry in the menu, like "Boot
> from first hard disk", in which case, I would boot XP
> from the laptop hard drive. 
> 
> I'm not very knowledgeable about booting, but I read
> that I would have to chainload, so I tried to use
> chain.c32 and the following entries: 
> 
> LABEL hd
>   menu label ^hd - boot IDE0 hd0 0
>   kernel chain.c32
>   append hd0 0
>   
> and 
> 
> LABEL hd2
>   menu label ^Boot from first hard disk
>   localboot 0x80
>   append -
> 
> but unfortunately nothing seems to happen (the first
> option says "illegal argument" or something, exits and
> shows boot menu again, the other simply show the boot
> menu again) - it seems as if chain.c32 interprets "hd0
> 0" to be a partition on the USB hard drive, instead of
> the local one? 
> 
> I tried to modify the source code of chain.c32 (the
> function is included below, compiled through
> DSL-embedded, with gcc package) where I tried to scan
> through possible hard disks (that is, loop through
> drive and partition indexes) and print out info, in
> hope that I'd spot the main (C) drive on the laptop.
> But apart from the USB drive itself, nothing seems to
> have an MBR, no matter how much I look? (it could be
> easier if I could save a text report, but the file
> open operation fails - I'm guessing because at the
> moment, it is not known what the default drive is??).
> 
It sounds like when your BIOS boots from the USB disk, it hides the 
primary hard disk.  This is pretty braindead behaviour, but I could see 
how it would "make sense" to someone as they implemented it.  The 
problem is, if it doesn't make the proper hard disk available as another 
drive number, the only way out would be to invoke the BIOS Boot 
Specification interfaces, to boot a different device.

Right now I don't have code for that.

	-hpa

Hi Axel, hpa, 

Thanks so much for your responses. 
> The "first" drive -- as seen be your BIOS -- when
booting from
> a USB disk or stick, isn't your laptop's HD but the
USB disk/stick.
> ... otherwise it would have booted from the laptop's
HD.

That is what I also thought - since "chain.c32 hd0 0"
seemed to boot from the USB disk, I asummed I'd find
the C drive at "hd1 0" but it failed, and so did "hd2
0" etc etc. Therefore I modified the chain.c32 code,
so it accepts max drive and partition number and loops
through them all, hoping to reveal an MBR - but I
couldn't see any (partly because the text dissapears
from screen very fast, and I couldn't get a report to
save on disk :) ) 
> It sounds like when your BIOS boots from the USB
disk, it hides the 
> primary hard disk.  This is pretty braindead
behaviour, but I could see
>  
> how it would "make sense" to someone as they
implemented it.  

Wow :) Never heard of this, but does make sense to me
too (the laptop's a Compaq) - thanks .. 
> The problem is, if it doesn't make the proper hard
disk available as
> another drive number, the only way out would be to
invoke the BIOS 
> Boot Specification interfaces, to boot a different
device.
> Right now I don't have code for that.
Thanks for the info.. Maybe you'd have a link where
something like that is discussed? 

Well, any suggestions on how to make this work would
be greatly appreciated.. 

Thanks again
b.



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