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[PATCH] bootstrapping NT with grub tweak


From: Jeremy Katz
Subject: [PATCH] bootstrapping NT with grub tweak
Date: 20 May 2002 16:40:15 -0400

This was originally reported in Red Hat's bugzilla as 
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=65034 by
address@hidden

To quote the original bug report 
"""
The version of grub included with RH 7.3 won't boot windows NT 4.0 SP3
on my system. NT boot fails with bluescreen "INACCESSIBLE_BOOT_DEVICE".
Before upgrade to RH 7.3 my system worked fine as a triple boot setup:
/dev/sda1 WinNT; /dev/sda2 Win95; /dev/sda3 RH Linux. Before upgrade
system was running RH 7.0 and triple boot with Lilo was working fine.

Research on web indicated that WinNT expects bootstrap loader to begin
with a CLI instruction. Checking grub sources shows it starts with a JMP
followed by a CLI. Solution: Change 1st instruction to a CLI, remove a
NOP and JMP to main part of bootstrap code. Rebuild and reinstall grub.
Tested on my triple boot system and a normal single boot RH 7.3 system
and works.
"""

The reporter attached the following patch which says improves the
situation for them.  Any comments?

Thanks,

Jeremy

--- grub-0.91/stage1/stage1.S.orig      Wed May 15 16:51:40 2002
+++ grub-0.91/stage1/stage1.S   Wed May 15 16:52:56 2002
@@ -53,8 +53,8 @@
         * parameter block.
         */
 
+       cli     /* NT requires this to be the first instruction */
        jmp     after_BPB
-       nop     /* do I care about this ??? */
 
        /*
         * This space is for the BIOS parameter block!!!!  Don't change
@@ -105,7 +105,6 @@
 after_BPB:
 
 /* general setup */
-       cli             /* we're not safe here! */
 
        /*
         * ljmp to the next instruction because some bogus BIOSes



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