Support making the disk readonly

3 files changed, 23 insertions, 7 deletions

diff --git a/memdisk/memdisk.asm b/memdisk/memdisk.asm
index 053fa41d..00a5f12b 100644
--- a/memdisk/memdisk.asm
+++ b/memdisk/memdisk.asm
@@ -7,7 +7,7 @@
 ;  A program to emulate an INT 13h disk BIOS from a "disk" in extended
 ;  memory.
 ;
-;   Copyright (C) 2001-2003  H. Peter Anvin
+;   Copyright (C) 2001-2004  H. Peter Anvin
 ;
 ;  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
@@ -234,9 +234,13 @@ do_copy:
 		ret
 
 Write:
+		test byte [ConfigFlags],01h
+		jnz .readonly
 		call setup_regs
 		xchg esi,edi		; Opposite direction of a Read!
 		jmp short do_copy
+.readonly:	mov ah,03h		; Write protected medium
+		ret
 
 		; Verify integrity; just bounds-check
 Verify:
@@ -559,7 +563,8 @@ Mem16MB		dd 0			; 16MB-4G memory amount (64K)
 DriveNo		db 0			; Our drive number
 DriveType	db 0			; Our drive type (floppies)
 DriveCnt	db 0			; Drive count (from the BIOS)
-		db 0			; Pad
+
+ConfigFlags	db 0			; Bit 0 - readonly
 
 MyStack		dw 0			; Offset of stack
 StatusPtr	dw 0			; Where to save status (zeroseg ptr)
diff --git a/memdisk/memdisk.doc b/memdisk/memdisk.doc
index c01ae5e1..d69e51cf 100644
--- a/memdisk/memdisk.doc
+++ b/memdisk/memdisk.doc
@@ -61,9 +61,12 @@ line options (currently untested):
 [*] MS-DOS only allows max 255 heads, and only allows 255 cylinders
     on floppy disks.
 
-If you want to recompile it from sources, you will need to make sure that
-you have a fairly recent binutils installed.  I have been using the
-binutils-2.11.90.0.8-9 RPM from RedHat.
+c) The disk is normally writable (although, of course, there is
+nothing backing it up, so it only lasts until reset.)  If you want,
+you can mimic a write-protected disk by specifying the command line
+option:
+
+   ro		Disk is readonly
 
 
 Some interesting things to note:
diff --git a/memdisk/setup.c b/memdisk/setup.c
index d52e11cd..92721e0e 100644
--- a/memdisk/setup.c
+++ b/memdisk/setup.c
@@ -1,7 +1,7 @@
 #ident "$Id$"
 /* ----------------------------------------------------------------------- *
  *   
- *   Copyright 2001-2003 H. Peter Anvin - All Rights Reserved
+ *   Copyright 2001-2004 H. Peter Anvin - All Rights Reserved
  *
  *   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
@@ -82,7 +82,8 @@ struct patch_area {
   uint8_t  driveno;
   uint8_t  drivetype;
   uint8_t  drivecnt;
-  uint8_t  _pad1;
+  uint8_t  configflags;
+#define CONFIG_READONLY	0x01
 
   uint16_t mystack;
   uint16_t statusptr;
@@ -568,6 +569,13 @@ uint32_t setup(syscall_t cs_syscall, void *cs_bounce)
   pptr->disksize  = geometry->sectors;
   pptr->diskbuf   = ramdisk_image + geometry->offset;
   pptr->statusptr = (geometry->driveno & 0x80) ? 0x474 : 0x441;
+  pptr->configflags = 0;
+
+  /* Readonly? */
+  if ( getcmditem("ro") != CMD_NOTFOUND ) {
+    printf("Marking disk readonly\n");
+    pptr->configflags |= CONFIG_READONLY;
+  }
 
   /* Set up a drive parameter table */
   if ( geometry->driveno & 0x80 ) {