From 3050a9253437f4a4b5ad4bf3b3efdc3c660a5137 Mon Sep 17 00:00:00 2001
From: Sebastian Schmelzer
Date: Mon, 25 Oct 2010 16:53:54 +0200
Subject: initial import of sc2010 scripts ..

---
 .../gpxe/src/arch/i386/prefix/bootpart.S           | 218 +++++++++++++++++++++
 1 file changed, 218 insertions(+)
 create mode 100644 contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S

(limited to 'contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S')

diff --git a/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S b/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S
new file mode 100644
index 0000000..968da1a
--- /dev/null
+++ b/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/bootpart.S
@@ -0,0 +1,218 @@
+FILE_LICENCE ( GPL2_OR_LATER )
+
+#define BOOT_SEG	0x07c0
+#define EXEC_SEG	0x0100
+#define STACK_SEG 	0x0200
+#define STACK_SIZE	0x2000
+	
+	.text
+	.arch i386
+	.section ".prefix", "awx", @progbits
+	.code16
+
+/*
+ * Find active partition
+ *
+ * Parameters:
+ *   %dl	: BIOS drive number
+ *   %bp	: Active partition handler routine
+ */
+find_active_partition:
+	/* Set up stack at STACK_SEG:STACK_SIZE */
+	movw	$STACK_SEG, %ax
+	movw	%ax, %ss
+	movw	$STACK_SIZE, %sp
+
+	/* Relocate self to EXEC_SEG */
+	pushw	$BOOT_SEG
+	popw	%ds
+	pushw	$EXEC_SEG
+	popw	%es
+	xorw	%si, %si
+	xorw	%di, %di
+	movw	$0x200, %cx
+	rep movsb
+	ljmp	$EXEC_SEG, $1f
+1:	pushw	%ds
+	popw	%es
+	pushw	%cs
+	popw	%ds
+
+	/* Check for LBA extensions */
+	movb	$0x41, %ah
+	movw	$0x55aa, %bx
+	stc
+	int	$0x13
+	jc	1f
+	cmpw	$0xaa55, %bx
+	jne	1f
+	movw	$read_lba, read_sectors
+1:	
+	/* Read and process root partition table */
+	xorb	%dh, %dh
+	movw	$0x0001, %cx
+	xorl	%esi, %esi
+	xorl	%edi, %edi
+	call	process_table
+
+	/* Print failure message */
+	movw	$10f, %si
+	jmp	boot_error
+10:	.asciz	"Could not locate active partition\r\n"
+
+/*
+ * Print failure message and boot next device
+ *
+ * Parameters:
+ *   %si	: Failure string
+ */
+boot_error:
+	cld
+	movw	$0x0007, %bx
+	movb	$0x0e, %ah
+1:	lodsb
+	testb	%al, %al
+	je	99f
+	int	$0x10
+	jmp	1b
+99:	/* Boot next device */
+	int	$0x18
+
+/*
+ * Process partition table
+ *
+ * Parameters:
+ *   %dl	: BIOS drive number
+ *   %dh	: Head
+ *   %cl	: Sector (bits 0-5), high two bits of cylinder (bits 6-7)
+ *   %ch	: Low eight bits of cylinder
+ *   %esi:%edi	: LBA address
+ *   %bp	: Active partition handler routine
+ *
+ * Returns:
+ *   CF set on error
+ */
+process_table:
+	pushal
+	call	read_boot_sector
+	jc	99f
+	movw	$446, %bx
+1:	call	process_partition
+	addw	$16, %bx
+	cmpw	$510, %bx
+	jne	1b
+99:	popal
+	ret
+
+/*
+ * Process partition
+ *
+ * Parameters:
+ *   %dl	: BIOS drive number
+ *   %dh	: Head
+ *   %cl	: Sector (bits 0-5), high two bits of cylinder (bits 6-7)
+ *   %ch	: Low eight bits of cylinder
+ *   %esi:%edi	: LBA address
+ *   %bx	: Offset within partition table
+ *   %bp	: Active partition handler routine
+ */
+process_partition:
+	pushal
+	/* Load C/H/S values from partition entry */
+	movb	%es:1(%bx), %dh
+	movw	%es:2(%bx), %cx
+	/* Update LBA address from partition entry */
+	addl	%es:8(%bx), %edi
+	adcl	$0, %esi
+	/* Check active flag */
+	testb	$0x80, %es:(%bx)
+	jz	1f
+	call	read_boot_sector
+	jc	99f
+	jmp	*%bp
+1:	/* Check for extended partition */
+	movb	%es:4(%bx), %al
+	cmpb	$0x05, %al
+	je	2f
+	cmpb	$0x0f, %al
+	je	2f
+	cmpb	$0x85, %al
+	jne	99f
+2:	call	process_table
+99:	popal
+	/* Reload original partition table */
+	call	read_boot_sector
+	ret
+
+/*
+ * Read single sector to %es:0000 and verify 0x55aa signature
+ *
+ * Parameters:
+ *   %dl	: BIOS drive number
+ *   %dh	: Head
+ *   %cl	: Sector (bits 0-5), high two bits of cylinder (bits 6-7)
+ *   %ch	: Low eight bits of cylinder
+ *   %esi:%edi	: LBA address
+ *
+ * Returns:
+ *   CF set on error
+ */
+read_boot_sector:
+	pushw	%ax
+	movw	$1, %ax
+	call	*read_sectors
+	jc	99f
+	cmpw	$0xaa55, %es:(510)
+	je	99f
+	stc	
+99:	popw	%ax
+	ret
+	
+/*
+ * Read sectors to %es:0000
+ *
+ * Parameters:
+ *   %dl	: BIOS drive number
+ *   %dh	: Head
+ *   %cl	: Sector (bits 0-5), high two bits of cylinder (bits 6-7)
+ *   %ch	: Low eight bits of cylinder
+ *   %esi:%edi	: LBA address
+ *   %ax	: Number of sectors (max 127)
+ *
+ * Returns:
+ *   CF set on error
+ */
+read_sectors:	.word	read_chs
+
+read_chs:
+	/* Read sectors using C/H/S address */
+	pushal
+	xorw	%bx, %bx
+	movb	$0x02, %ah
+	stc
+	int	$0x13
+	sti
+	popal
+	ret
+
+read_lba:
+	/* Read sectors using LBA address */
+	pushal
+	movw	%ax, (lba_desc + 2)
+	pushw	%es
+	popw	(lba_desc + 6)
+	movl	%edi, (lba_desc + 8)
+	movl	%esi, (lba_desc + 12)
+	movw	$lba_desc, %si
+	movb	$0x42, %ah
+	int	$0x13
+	popal
+	ret
+
+lba_desc:
+	.byte	0x10
+	.byte	0
+	.word	1
+	.word	0x0000
+	.word	0x0000
+	.long	0, 0
-- 
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