[PATCH 7/7] RFC: Use correct addresses, eliminate manual relocations

[Pavel Roskin <proski@gnu.org>]

ChangeLog:

	* boot/i386/pc/boot.S: Declare 0x0-0x7c00 as a discardable .bss
	segment.  Eliminate ABS, rely on the assembler knowing correct
	addresses.  Eliminate .bss segment for the kernel, use direct
	jump to the kernel address.
---
 boot/i386/pc/boot.S |   72 +++++++++------------------------------------------
 1 files changed, 12 insertions(+), 60 deletions(-)

diff --git a/boot/i386/pc/boot.S b/boot/i386/pc/boot.S
index e3f5228..0002773 100644
--- a/boot/i386/pc/boot.S
+++ b/boot/i386/pc/boot.S
@@ -24,20 +24,13 @@
  *  defines for the code go here
  */
 
-	/* Absolute addresses
-	   This makes the assembler generate the address without support
-	   from the linker. (ELF can't relocate 16-bit addresses!) */
-#define ABS(x) (x-_start+0x7c00)
-
 	/* Print message string */
-#ifdef APPLE_CC
-#define MSG(x)	x ## _abs = ABS(x); movw $x ## _abs, %si; call message
-#else
-#define MSG(x)	movw $ABS(x), %si; call message
-#endif
+#define MSG(x)	movw $x, %si; call message
 
 	.file	"boot.S"
 
+	.bss
+	. = 0x7c00
 	.text
 
 	/* Tell GAS to generate 16-bit instructions so that this code works
@@ -126,12 +119,7 @@ boot_drive_check:
 	 * ljmp to the next instruction because some bogus BIOSes
 	 * jump to 07C0:0000 instead of 0000:7C00.
 	 */
-#ifdef APPLE_CC
-	real_start_abs = ABS(real_start)
-	ljmp	$0, $(real_start_abs)
-#else
-	ljmp	$0, $ABS(real_start)
-#endif
+	ljmp	$0, $real_start
 
 real_start:
 
@@ -148,12 +136,7 @@ real_start:
 	/*
 	 *  Check if we have a forced disk reference here
 	 */
-#ifdef APPLE_CC
-	boot_drive_abs = ABS (boot_drive)
-	movb    boot_drive_abs, %al
-#else
-	movb   ABS(boot_drive), %al
-#endif
+	movb	boot_drive, %al
 	cmpb	$0xff, %al
 	je	1f
 	movb	%al, %dl
@@ -165,12 +148,7 @@ real_start:
 	MSG(notification_string)
 
 	/* set %si to the disk address packet */
-#ifdef APPLE_CC
-	disk_address_packet_abs = ABS (disk_address_packet)
-	movw	$disk_address_packet_abs, %si
-#else
-	movw	$ABS(disk_address_packet), %si
-#endif
+	movw	$disk_address_packet, %si
 
 	/* do not probe LBA if the drive is a floppy */
 	testb	$GRUB_BOOT_MACHINE_BIOS_HD_FLAG, %dl
@@ -211,18 +189,10 @@ lba_mode:
 	movw	$0x0010, (%si)
 
 	/* the absolute address */
-#ifdef APPLE_CC
-	kernel_sector_abs = ABS (kernel_sector)
-	movl	(kernel_sector_abs), %ebx
-	movl	%ebx, 8(%si)
-	movl	(kernel_sector_abs + 4), %ebx
-	movl	%ebx, 12(%si)
-#else
-	movl	ABS(kernel_sector), %ebx
+	movl	kernel_sector, %ebx
 	movl	%ebx, 8(%si)
-	movl	ABS(kernel_sector + 4), %ebx
+	movl	kernel_sector + 4, %ebx
 	movl	%ebx, 12(%si)
-#endif
 
 	/* the segment of buffer address */
 	movw	$GRUB_BOOT_MACHINE_BUFFER_SEG, 6(%si)
@@ -289,22 +259,13 @@ final_init:
 
 setup_sectors:
 	/* load logical sector start (top half) */
-#ifdef APPLE_CC
-	kernel_sector_abs = ABS (kernel_sector)
-	movl	(kernel_sector_abs + 4), %eax
-#else
-	movl	ABS(kernel_sector + 4), %eax
-#endif
+	movl	kernel_sector + 4, %eax
 
 	orl	%eax, %eax
 	jnz	geometry_error
 
 	/* load logical sector start (bottom half) */
-#ifdef APPLE_CC
-	movl	(kernel_sector_abs), %eax
-#else
-	movl	ABS(kernel_sector), %eax
-#endif
+	movl	kernel_sector, %eax
 
 	/* zero %edx */
 	xorl	%edx, %edx
@@ -389,7 +350,7 @@ copy_buffer:
 	popa
 
 	/* boot kernel */
-	jmp	kernel_entry
+	jmp	GRUB_BOOT_MACHINE_KERNEL_ADDR
 
 /* END OF MAIN LOOP */
 
@@ -475,12 +436,7 @@ floppy_probe:
  *  Perform floppy probe.
  */
 
-#ifdef APPLE_CC
-	probe_values_abs = ABS (probe_values)
-	movw	$(probe_values_abs-1), %si
-#else
-	movw	$ABS(probe_values-1), %si
-#endif
+	movw	$probe_values - 1, %si
 
 probe_loop:
 	/* reset floppy controller INT 13h AH=0 */
@@ -524,7 +480,3 @@ fd_probe_error_string:	.asciz "Floppy"
 
 /* the last 2 bytes in the sector 0 contain the signature */
 	.word	GRUB_BOOT_MACHINE_SIGNATURE
-
-	.bss
-	. = . + 0x200
-kernel_entry: