add the command map.

ChangeLog

@@ -1,3 +1,27 @@
+1999-10-21  OKUJI Yoshinori  <okuji@kuicr.kyoto-u.ac.jp>
+
+	Add BIOS drive remapping support for chain-loading some foolish
+	operating systems.
+	
+	* stage2/builtins.c (bios_drive_map): New variable.
+	(boot_func): If KERNEL_TYPE is KERNEL_TYPE_CHAINLOADER, check
+	if BIOS_DRIVE_MAP contains meaningful values. If so, search for
+	SAVED_DRIVE in BIOS_DRIVE_MAP and exchange SAVED_DRIVE with the
+	mapped drive if found. And then call set_int13_handler.
+	(map_func): New function.
+	(builtin_map): New variable.
+	(builtin_table): Added a pointer to BUILTIN_MAP.
+	* stage2/asm.S (ABS): New macro.
+	[!STAGE1_5] (set_int13_handler): New function.
+	[!STAGE1_5] (int13_handler): New interrupt handler for the real
+	mode.
+	[!STAGE1_5] (drive_map): New variable.
+	[!STAGE1_5] (int13_handler_end): New label used for just
+	computing the end address of int13_handler.
+	* stage2/shared.h (DRIVE_MAP_SIZE): New macro.
+	(set_int13_handler): Declared.
+	* grub/asmstub.c (set_int13_handler): New function. Do nothing.
+	
 1999-10-20  OKUJI Yoshinori  <okuji@kuicr.kyoto-u.ac.jp>
 
 	* stage2/builtins.c (find_func): Print only the device names.

NEWS

@@ -15,6 +15,9 @@ New in 0.5.94:
   added.
 * The command "find" searches for a filename in all devices and print
   the list of the device which contain the file.
+* The command "map" maps a drive to another drive so that we can
+  chain-load some foolish operating systems (such as DOS) even if such
+  an operating system resides at a non-first drive.
 
 New in 0.5.93:
 * ELF format of FreeBSD kernel is supported.

grub/asmstub.c

@@ -597,6 +597,12 @@ gateA20 (int linear)
   /* Nothing to do in the simulator. */
 }
 
+/* Copy MAP to the drive map and set up the int13 handler.  */
+void
+set_int13_handler (unsigned short *map)
+{
+  /* Nothing to do in the simulator.  */
+}
 
 int
 get_code_end (void)

stage2/asm.S

@@ -22,6 +22,12 @@
 
 #include "shared.h"
 
+#ifdef STAGE1_5
+#define	ABS(x)	((x) - EXT_C(main) + 0x2200)
+#else
+#define	ABS(x)	((x) - EXT_C(main) + 0x8200)
+#endif
+	
 	.file	"asm.S"
 
 	.text
@@ -46,11 +52,7 @@ ENTRY(main)
 	 *  Guarantee that "main" is loaded at 0x0:0x8200 in stage2 and
 	 *  at 0x0:0x2200 in stage1.5.
 	 */
-#ifndef STAGE1_5
+	ljmp $0, $ABS(codestart)
-	ljmp $0, $(codestart - EXT_C(main) + 0x8200)
-#else
-	ljmp $0, $(codestart - EXT_C(main) + 0x2200)
-#endif
 
 	/*
 	 *  Compatibility version number
@@ -153,6 +155,135 @@ ENTRY(stop_floppy)
 	outb	%al, %dx
 	ret
 
+/*
+ * set_int13_handler(map)
+ *
+ * Copy MAP to the drive map and set up int13_handler.
+ */
+ENTRY(set_int13_handler)
+	pushl	%ebp
+	movl	%esp, %ebp
+
+	pushl	%ecx
+	pushl	%edi
+	pushl	%esi
+
+	/* copy MAP to the drive map */
+	movl	$DRIVE_MAP_SIZE, %ecx
+	movl	$ABS(drive_map), %edi
+	movl	4(%ebp), %esi
+	cld
+	rep
+	movsb
+
+	/* save the original int13 handler */
+	movw	0x13 * 4, %ax
+	movw	%ax, int13_offset
+	movw	0x13 * 4 + 2, %ax
+	movw	%ax, int13_segment
+	
+	/* get the lower memory size */
+	movl	$EXT_C(mbi), %edi
+	movl	4(%edi), %eax
+	/* decrease the lower memory size and set it to the BIOS memory */
+	decl	%eax
+	movw	%ax, 0x413
+	/* compute the segment */
+	shll	$6, %eax
+
+	/* save the new int13 handler */
+	movw	%ax, 0x13 * 4 + 2
+	xorw	%ax, %ax
+	movw	%ax, 0x13 * 4
+
+	/* copy int13_handler to the reserved area */
+	shll	$4, %eax
+	movl	%eax, %edi
+	movl	$ABS(int13_handler), %esi
+	movl	$(int13_handler_end - int13_handler), %ecx
+	rep
+	movsb
+
+	popl	%esi
+	popl	%edi
+	popl	%ecx
+	popl	%ebp
+	ret
+	
+	
+/* 
+ * Map a drive to another drive.
+ */
+	
+	.code16
+	
+int13_handler:
+	pushw	%ax
+	pushw	%bp
+	movw	%sp, %bp
+	
+	pushw	%ds
+	pushw	%si
+
+	/* set %ds to %cs */	
+	movw	%cs, %ax
+	movw	%ax, %ds
+	/* set %si to the drive map */
+	movw	$(drive_map - int13_handler), %si
+	/* find the drive number from the drive map */
+1:	
+	lodsw
+	/* check if this is the end */
+	testw	%ax, %ax
+	jz	2f
+	/* check if this matches the drive number */
+	cmpb	%al, %dl
+	jne	1b
+	/* if so, perform the mapping */
+	movb	%ah, %dl
+2:
+	/* restore %si and %ds */
+	popw	%si
+	popw	%ds
+	/* save %ax in the stack */
+	pushw	%ax
+	/* set %ax and %bp to the original values */
+	movw	2(%bp), %ax
+	movw	(%bp), %bp
+	/* simulate the interrupt call */
+	pushf
+	/* ljmp */
+	.byte	0x9a
+int13_offset:	.word	0
+int13_segment:	.word	0
+	/* restore %bp */
+	movw	%sp, %bp
+	/* save %ax */
+	pushw	%ax
+	/* check if should map the drive number */
+	movw	4(%bp), %ax
+	cmpw	$0x8, %ax
+	jne	3f
+	cmpw	$0x15, %ax
+	jne	3f
+	/* check if the mapping was performed */
+	movw	(%bp), %ax
+	testw	%ax, %ax
+	jz	3f
+	/* perform the mapping */
+	movb	%al, %dl
+3:
+	popw	%ax
+	movw	2(%bp), %bp
+	addw	$6, %sp
+	iret
+
+drive_map:	.space	(DRIVE_MAP_SIZE + 1) * 2
+int13_handler_end:
+	
+	.code32
+	
+	
 /*
  * chain_stage1(segment, offset, part_table_addr)
  *

stage2/builtins.c

@@ -46,6 +46,8 @@ int normal_color;
 int highlight_color;
 /* The timeout.  */
 int grub_timeout = -1;
+/* The BIOS drive map.  */
+static unsigned short bios_drive_map[DRIVE_MAP_SIZE + 1];
 
 /* Initialize the data for builtins.  */
 void
@@ -101,6 +103,29 @@ boot_func (char *arg, int flags)
 
     case KERNEL_TYPE_CHAINLOADER:
       /* Chainloader */
+
+      /* Check if we should set the int13 handler.  */
+      if (bios_drive_map[0] != 0)
+	{
+	  int i;
+
+	  /* Search for SAVED_DRIVE.  */
+	  for (i = 0; i <= DRIVE_MAP_SIZE; i++)
+	    {
+	      if (! bios_drive_map[i])
+		break;
+	      else if ((bios_drive_map[i] & 0xFF) == saved_drive)
+		{
+		  /* Exchage SAVED_DRIVE with the mapped drive.  */
+		  saved_drive = (bios_drive_map[i] >> 8) & 0xFF;
+		  break;
+		}
+	    }
+
+	  /* Set the handler. This is somewhat dangerous.  */
+	  set_int13_handler (bios_drive_map);
+	}
+      
       gateA20 (0);
       boot_drive = saved_drive;
       chain_stage1 (0, BOOTSEC_LOCATION, BOOTSEC_LOCATION - 16);
@@ -1432,6 +1457,62 @@ static struct builtin builtin_makeactive =
   " This command is limited to _primary_ PC partitions on a hard disk."
 };
 
+
+/* map */
+/* Map FROM_DRIVE to TO_DRIVE.  */
+static int
+map_func (char *arg, int flags)
+{
+  char *to_drive;
+  char *from_drive;
+  unsigned long to, from;
+  int i;
+  
+  to_drive = arg;
+  from_drive = skip_to (0, arg);
+
+  /* Get the drive number for TO_DRIVE.  */
+  set_device (to_drive);
+  if (errnum)
+    return 1;
+  to = current_drive;
+
+  /* Get the drive number for FROM_DRIVE.  */
+  set_device (from_drive);
+  if (errnum)
+    return 1;
+  from = current_drive;
+
+  /* If TO and FROM is the same, do nothing.  */
+  if (to == from)
+    return 0;
+  
+  /* Search for an empty slot in BIOS_DRIVE_MAP.  */
+  for (i = 0; i <= DRIVE_MAP_SIZE; i++)
+    if (! bios_drive_map[i])
+      break;
+
+  if (i > DRIVE_MAP_SIZE)
+    {
+      errnum = ERR_WONT_FIT;
+      return 1;
+    }
+
+  bios_drive_map[i] = from | (to << 8);
+  return 0;
+}
+
+static struct builtin builtin_map =
+{
+  "map",
+  map_func,
+  BUILTIN_CMDLINE,
+  "map TO_DRIVE FROM_DRIVE",
+  "Map the drive FROM_DRIVE to the drive TO_DRIVE. This is necessary"
+  " when you chain-load some operating systems, such as DOS, if such a"
+  " OS resides at a non-first drive."
+};
+  
 
 /* module */
 static int
@@ -2101,6 +2182,7 @@ struct builtin *builtin_table[] =
   &builtin_install,
   &builtin_kernel,
   &builtin_makeactive,
+  &builtin_map,
   &builtin_module,
   &builtin_modulenounzip,
   &builtin_password,

stage2/shared.h

@@ -117,6 +117,9 @@ extern char *grub_scratch_mem;
 #define MENU_BUF		(UNIQUE_BUF + UNIQUE_BUFLEN)
 #define MENU_BUFLEN		(0x8000 + PASSWORD_BUF - UNIQUE_BUF)
 
+/* The size of the drive map.  */
+#define DRIVE_MAP_SIZE		8
+
 /*
  *  Linux setup parameters
  */
@@ -494,6 +497,9 @@ void cmain (void);
 /* Halt the processor (called after an unrecoverable error). */
 void stop (void) __attribute__ ((noreturn));
 
+/* Copy MAP to the drive map and set up int13_handler.  */
+void set_int13_handler (unsigned short *map);
+
 /* calls for direct boot-loader chaining */
 void chain_stage1 (int segment, int offset, int part_table_addr)
      __attribute__ ((noreturn));