mbr_ho.bin: Handoff MBR

This mbr code entity shows DL, DS, SI, 16 bytes of [DS:SI], ES, DI,
4 bytes of [ES:DI], and scans F0000h-FFFFFh on 16 byte alignment for $PnP.

This is useful for testing when MBR or VBR/PBR handoff goes awry.

1 files changed, 271 insertions, 0 deletions

diff --git a/mbr/mbr_ho.S b/mbr/mbr_ho.S
new file mode 100644
index 00000000..993b0c3c
--- /dev/null
+++ b/mbr/mbr_ho.S
@@ -0,0 +1,271 @@
+/* -----------------------------------------------------------------------
+ *
+ *   Copyright 2010 Gene Cumm
+ *
+ *   Portions from mbr.S:
+ *   Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
+ *
+ *   Permission is hereby granted, free of charge, to any person
+ *   obtaining a copy of this software and associated documentation
+ *   files (the "Software"), to deal in the Software without
+ *   restriction, including without limitation the rights to use,
+ *   copy, modify, merge, publish, distribute, sublicense, and/or
+ *   sell copies of the Software, and to permit persons to whom
+ *   the Software is furnished to do so, subject to the following
+ *   conditions:
+ *
+ *   The above copyright notice and this permission notice shall
+ *   be included in all copies or substantial portions of the Software.
+ *
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ *   OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * mbr_ho.S: MBR-like codeblock to display handoff data
+ *
+ * Displays the values of DL, DS, SI, the contents of [DS:SI] (16 bytes),
+ * the values of ES, DI then the contents of [ES:DI] (4 bytes) then reports
+ * a boot failure.
+ */
+
+#define DEBUG_MARKER1
+#define DEBUG_START
+#define DEBUG_LOADE
+#define DEBUG_PNP
+
+#ifdef DEBUG_MARKER1
+	.macro ASCII_MARKER1 s:vararg
+	.ascii \s
+	.endm
+#else	/* DEBUG_MARKER1 */
+	.macro ASCII_MARKER1 s
+	.endm
+#endif	/* DEBUG_MARKER1 */
+
+#ifdef DEBUG_LOADE
+	.macro LOADE r:req, t:req
+	movw	(e_\r), %\t
+	.endm
+#else	/* DEBUG_LOADE */
+	.macro LOADE r:req, t:req
+	popw %\t
+	.endm
+#endif	/* DEBUG_LOADE */
+
+	.code16
+	.text
+
+entry		= 0x7c00
+pnps		= (entry)
+pnpi		= (pnps-2)
+stack		= (pnpi-2)
+e_di		= (stack-2)
+e_es		= (stack-4)
+e_si		= (stack-6)
+e_ds		= (stack-8)
+
+BIOS_page	= 0x462
+
+	.globl	_start
+_start:
+	cli
+	xorw	%ax, %ax
+	movw	%ax, %ss
+	movw	$stack, %sp
+	sti
+	cld
+	pushw	%di		/* es:di -> $PnP header */
+	pushw	%es
+	pushw	%si
+	pushw	%ds
+	push	%cs
+	pop	%ds
+
+#ifdef DEBUG_START
+	pushw	%dx
+	call	crlf
+	movw	$(_start),%dx	/* 0x0600 mbr.ld .text address */
+	call	wrhexw
+	call	crlf
+//	movw	$(entry - _start),%dx	/* 0x7C00 */
+	call	caddr
+caddr:	popw	%ax
+	sub	$(caddr - _start), %ax
+	movw	%ax, %dx	/* Same size as pushw %ax;popw %dx */
+	call	wrhexw
+	call	crlf
+	popw	%dx
+#endif	/* DEBUG_START */
+
+	/* write DL */
+pr_dl:	call	wrstr
+	.ascii	"DL: \0"
+	call	wrhexb
+	/* DS */
+pr_ds:	call	wrstr
+	.ascii	"  DS: \0"
+//	popw	%dx
+	LOADE	ds, dx
+	pushw	%dx
+	popw	%es
+	call	wrhexw
+	/* SI */
+pr_si:	call	wrstr
+	.ascii	"  SI: \0"
+//	popw	%dx
+	LOADE	si, dx
+	pushw	%dx
+	popw	%di
+	call	wrhexw
+	call	crlf
+	/* DS:SI */
+	movw	$16, %cx
+	call	wrhexbses
+	call	crlf
+
+	/* ES */
+pr_es:	call	wrstr
+	.ascii	"ES: \0"
+//	popw	%dx
+	LOADE	es, dx
+	pushw	%dx
+	popw	%es
+	call	wrhexw
+pr_di:	call	wrstr
+	.ascii	"  DI: \0"
+//	popw	%dx
+	LOADE	di, dx
+	pushw	%dx
+	popw	%di
+	call	wrhexw
+	call	crlf
+	/* ES:DI */	/* %es:0(%di) */
+	movw	$4, %cx
+	call	wrhexbses
+	call	crlf
+
+	/* $PnP Scan */
+	movw	$0xf000, %dx
+	pushw	%dx
+	popw	%es
+	movw	$0, %si
+	movw	$0x1000, %cx
+	/* 0x506E5024 */
+	movw	$0x5024, %dx
+	movw	$0x506E, %bx
+ch_pnp:	es lodsw
+	cmp	%dx, %ax
+	jne	ch_pnp_l
+	es lodsw
+	cmp	%bx, %ax
+	je	pr_pnp
+ch_pnp_l:
+	addw	$14, %si
+	andw	$0xFFF0, %si
+	loopw	ch_pnp
+	jmp	end
+pr_pnp:
+	call	wrstr
+	.ascii	"$PnP-\0"
+	movw	%es, %dx
+	call	wrhexw
+	movb	$':, %al
+	call	wrchr
+	movw	%si, %dx
+	andw	$0xFFF0, %dx
+	call	wrhexw
+	call	crlf
+
+end:
+	jmp	bootfail
+
+	ASCII_MARKER1	"wc"
+wrchr:
+	movb	$0x0e, %ah
+	movb	(BIOS_page), %bh
+	movb	$0x07, %bl
+	int	$0x10		/* May destroy %bp */
+	ret
+
+	ASCII_MARKER1	"ws"
+wrstr:
+	pop	%si
+wrstr_l:
+	lodsb
+	cmpb	$0, %al
+	je	wrstr_d
+	call	wrchr
+	jmp	wrstr_l
+wrstr_d:
+	push	%si
+	ret
+
+crlf:
+	call wrstr
+	.ascii "\r\n\0"
+	ret
+
+	ASCII_MARKER1	"hx"
+wrhexn:
+	and	$0x0F, %al
+	cmpb	$10, %al
+	jae	.alph
+	addb	$'0, %al
+	jmp	.wc
+.alph:
+	addb	$('A - 10), %al
+.wc:
+	call wrchr
+	ret
+
+wrhexb:
+	movb	%dl, %al
+	pushw	%ax
+	rorw	$4, %ax
+	call	wrhexn
+	popw	%ax
+	call	wrhexn
+	ret
+
+wrhexw:
+	rorw	$8, %dx
+	call wrhexb
+	rorw	$8, %dx
+	call wrhexb
+	ret
+
+	ASCII_MARKER1	"HE"
+wrhexbses:
+	pushw	%di
+	popw	%si
+wrhexbses_l:
+	movb	$' , %al
+	call	wrchr
+	es lodsb
+	movw	%ax, %dx
+	call	wrhexb
+	loop	wrhexbses_l
+	ret
+
+data:
+	ASCII_MARKER1	"bf"
+bootfail:
+	int	$0x18		/* Boot failure */
+die:
+	hlt
+	jmp	die
+
+zerob:		/* Begin zeroing block to fill to desired length */
+		/* 420 bytes for FAT32 */
+zeroln		= (420 - (zerob - _start))
+	.=.+zeroln	/* prevents overflow */
+zeroe: