From f805675eef4b2119d252465a211b643f79d17c7e Mon Sep 17 00:00:00 2001
From: hpa <hpa>
Date: Fri, 25 Oct 2002 06:47:20 +0000
Subject: LDLINUX: Fix "kaboom" bug when booting off hard disk

Provide an API call for "perform final cleanup"
---
 comboot.doc | 35 +++++++++++++++++++++++++++++++++++
 comboot.inc | 22 ++++++++++++++++++++++
 ldlinux.asm | 10 ++++++++--
 3 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/comboot.doc b/comboot.doc
index 2f5f247c..f427246f 100644
--- a/comboot.doc
+++ b/comboot.doc
@@ -292,6 +292,10 @@ AX=0007h	Read file
 	aligned.  SYSLINUX guarantees at least this alignment for the
 	COMBOOT load segment or the COM32 bounce buffer.
 
+	Keep in mind that a "file" may be a TFTP connection, and that
+	leaving a file open for an extended period of time may result
+	in a timeout.
+
 	WARNING: Calling this function with an invalid file handle
 	will probably crash the system.
 
@@ -377,3 +381,34 @@ AX=000Bh	Get Serial Console Configuration
 
 	If no serial port is configured, DX will be set to 0 and the
 	other registers are undefined.
+
+
+AX=000Ch	Perform final cleanup
+	Input:	AX	000Ch
+		DX	derivative-specific flags (0000h = clean up all)
+	Output:	None
+
+	This routine performs any "final cleanup" the boot loader
+	would normally perform before loading a kernel, such as
+	unloading the PXE stack in the case of PXELINUX.  AFTER
+	INVOKING THIS CALL, NO OTHER API CALLS MAY BE INVOKED, NOR MAY
+	THE PROGRAM TERMINATE AND RETURN TO THE BOOT LOADER.  This
+	call basically tells the boot loader "get out of the way, I'll
+	handle it from here."  The boot loader will continue to
+	provide interrupt and BIOS call thunking services as long its
+	memory areas (0x1000-0xffff, 0x100000-0x100fff) are not
+	overwritten.  MAKE SURE TO DISABLE INTERRUPTS BEFORE
+	OVERWRITING THESE MEMORY AREAS.
+
+	The permissible values for DX are as follows:
+
+	SYSLINUX:	0000h	Normal cleanup
+
+	PXELINUX:	0000h	Normal cleanup
+			0003h	Keep UNDI and PXE stacks loaded
+
+	ISOLINUX:	0000h	Normal cleanup
+
+	All other values are undefined, and may have different
+	meanings in future versions of SYSLINUX.
+
diff --git a/comboot.inc b/comboot.inc
index d7b03a70..15b25fce 100644
--- a/comboot.inc
+++ b/comboot.inc
@@ -478,6 +478,27 @@ comapi_serialcfg:
 		clc
 		ret
 
+;
+; INT 22h AX=000Ch	Perform final cleanup
+;
+comapi_cleanup:
+%if IS_PXELINUX
+		; Unload PXE if requested
+		test dl,3
+		setnz [KeepPXE]
+		call unload_pxe
+%elif IS_SYSLINUX
+		; Restore original FDC table
+		mov eax,[OrigFDCTabPtr]
+		mov [fdctab],eax
+%endif
+		; Reset the floppy disk subsystem
+		xor ax,ax
+		xor dx,dx
+		int 13h
+		clc
+		ret
+
 ;
 ; This stuff should really be in the data section...
 ;
@@ -513,6 +534,7 @@ int22_table:
 		dw comapi_pxecall		; 0009 call PXE stack
 		dw comapi_derinfo		; 000A derivative-specific info
 		dw comapi_serialcfg		; 000B get serial port config
+		dw comapi_cleanup		; 000C perform final cleanup
 int22_count	equ ($-int22_table)/2
 
 APIKeyWait	db 0
diff --git a/ldlinux.asm b/ldlinux.asm
index 73803308..6de92f1e 100644
--- a/ldlinux.asm
+++ b/ldlinux.asm
@@ -294,8 +294,6 @@ start:
 		mov ds,ax		; Now we can initialize DS...
 
 		mov [di+bsDriveNumber-FloppyTable],dl
-		and dl,dl		; If floppy disk (00-7F), assume no
-		js harddisk		; partition table
 ;
 ; Now sautee the BIOS floppy info block to that it will support decent-
 ; size transfers; the floppy block is 11 bytes and is stored in the
@@ -308,6 +306,14 @@ start:
 		lfs si,[bx]		; FS:SI -> original fdctab
 		push fs			; Save on stack in case we need to bail
 		push si
+
+		; Save the old fdctab even if hard disk so the stack layout
+		; is the same.  The instructions above do not change the flags
+		and dl,dl		; If floppy disk (00-7F), assume no
+					; partition table
+		js harddisk
+
+floppy:
 		mov cl,6		; 12 bytes (CX == 0)
 		; es:di -> FloppyTable already
 		; This should be safe to do now, interrupts are off...
-- 
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