core: let xfer_buf_seg, real_mode_seg be assigned by the linker

Use the linker to assign xfer_bug_seg and real_mode_seg.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

9 files changed, 50 insertions, 22 deletions

diff --git a/core/com32.inc b/core/com32.inc
index 3fa2d31e..b198dac0 100644
--- a/core/com32.inc
+++ b/core/com32.inc
@@ -86,7 +86,7 @@ com32_start:
 		push dword core_cfarcall	; Cfarcall entry point
 		push dword core_farcall		; Farcall entry point
 		push dword (1 << 16)		; 64K bounce buffer
-		push dword (xfer_buf_seg << 4)	; Bounce buffer address
+		push dword core_xfer_buf	; Bounce buffer address
 		push dword core_intcall		; Intcall entry point
 		push dword command_line		; Command line pointer
 		push dword 7			; Argument count
diff --git a/core/conio.inc b/core/conio.inc
index 60d1fcb2..5157e485 100644
--- a/core/conio.inc
+++ b/core/conio.inc
@@ -15,7 +15,7 @@
 ;; conio.inc
 ;;
 ;; Console I/O code, except:
-;;   writechr, writestr_early		- module-dependent
+;;   writechr, writestr_early	- module-dependent
 ;;   writestr, crlf		- writestr.inc
 ;;   writehex*			- writehex.inc
 ;;
diff --git a/core/init.inc b/core/init.inc
index a3fe3041..90c0293b 100644
--- a/core/init.inc
+++ b/core/init.inc
@@ -64,11 +64,19 @@ check_escapes:
 ; NOTE: Linux doesn't use all of real_mode_seg, but we use the same
 ; segment for COMBOOT images, which can use all 64K
 ;
-dosram_k	equ (real_mode_seg+0x1000) >> 6	; Minimum DOS memory (K)
 		int 12h
-		cmp ax,dosram_k
+		mov dx,real_mode_seg + 0x1000
+		shr dx,6		
+		cmp ax,dx
 		jae enough_ram
+		mov ax,dx
 		mov si,err_noram
+		mov cl,10
+		div cl
+		add [si+err_noram.size-err_noram+2],ah
+		cbw
+		div cl
+		add [si+err_noram.size-err_noram],ax
 		call writestr_early
 		jmp kaboom
 enough_ram:
@@ -76,7 +84,7 @@ skip_checks:
 
 		section .data16
 err_noram	db 'It appears your computer has less than '
-		asciidec dosram_k
+.size		db '000'
 		db 'K of low ("DOS")'
 		db CR, LF
 		db 'RAM.  Syslinux needs at least this amount to boot.  If you get'
@@ -84,8 +92,8 @@ err_noram	db 'It appears your computer has less than '
 		db 'this message in error, hold down the Ctrl key while'
 		db CR, LF
 		db 'booting, and I will take your word for it.', CR, LF, 0
-		section .text16
 
+		section .text16
 ;
 ; The code to decompress the PM code and initialize other segments.
 ;
diff --git a/core/isolinux.asm b/core/isolinux.asm
index d6be7502..4a029c4e 100644
--- a/core/isolinux.asm
+++ b/core/isolinux.asm
@@ -414,7 +414,7 @@ found_file:
 		; address (7C00h) is *not* 2K-sector-aligned, the safest
 		; way to deal with this is to load into the xfer_buf_seg
 		; and then copy the data in place.
-MaxLMA		equ xfer_buf_seg << 4
+MaxLMA		equ core_xfer_buf
 
 		mov bx,(7C00h+SECTOR_SIZE) >> 4
 		mov bp,[ImageSectors]
diff --git a/core/kernel.inc b/core/kernel.inc
index 3ac5af1c..245cd6db 100644
--- a/core/kernel.inc
+++ b/core/kernel.inc
@@ -63,7 +63,7 @@ cmd_line_here	equ $			; F800 Should be out of the way
 		endstruc
 
 		global cmd_line
-cmd_line	equ (real_mode_seg << 4) + cmd_line_here
+cmd_line	equ core_real_mode + cmd_line_here
 
 ;
 ; Old kernel command line signature
diff --git a/core/layout.inc b/core/layout.inc
index baf45b92..b769832f 100644
--- a/core/layout.inc
+++ b/core/layout.inc
@@ -115,13 +115,6 @@ RBFG_brainfuck:	resb 2048		; Bigger than an Ethernet packet...
 ; Keep the low-memory footprint as small as possible... overrun is a hard
 ; failure!
 ;
-; 0000h - main code/data segment (and BIOS segment)
-;
-; This stuff really should come from the linker...
-;
-		global	xfer_buf_seg, core_xfer_buf
-xfer_buf_seg	equ 2000h
-core_xfer_buf	equ xfer_buf_seg << 4
 
 serial_buf_size	equ 4096		; Should be a power of 2
 
@@ -141,8 +134,24 @@ serial_buf_size	equ 4096		; Should be a power of 2
 auxseg		resb aux_size
 
 ;
+; Transfer buffer segment: guaranteed to be aligned 64K, used for disk I/O
+; One symbol for the segment number, one for the absolute address
+;
+		extern	xfer_buf_seg
+		section .xfer_buf	write nobits align=65536
+		global	core_xfer_buf
+core_xfer_buf	resb 65536
+
+;
 ; Segment for the real mode code (needed as long as we have a in-kernel
 ; loader and/or COM16 support.
+; One symbol for the segment number, one for the absolute address
 ;
-real_mode_seg	equ xfer_buf_seg + 1000h
+		extern	real_mode_seg
+		section .real_mode	write nobits align=65536
+		global	core_real_mode
+core_real_mode	resb 65536
+
 comboot_seg	equ real_mode_seg	; COMBOOT image loading zone
+
+		section .text16
diff --git a/core/loadhigh.inc b/core/loadhigh.inc
index 63ab0010..205c3e61 100644
--- a/core/loadhigh.inc
+++ b/core/loadhigh.inc
@@ -87,7 +87,7 @@ load_high:
 		ja .overflow
 
 		push esi			; <D> File handle/cluster pointer
-		mov esi,(xfer_buf_seg << 4)	; Source address
+		mov esi,core_xfer_buf		; Source address
 		call bcopy			; Copy to high memory
 		pop esi				; <D> File handle/cluster pointer
 		popf				; <C> EOF status
diff --git a/core/runkernel.inc b/core/runkernel.inc
index 30177e80..f4dc28ee 100644
--- a/core/runkernel.inc
+++ b/core/runkernel.inc
@@ -259,7 +259,7 @@ read_kernel:
                 shl si,9			; Convert to bytes
                 mov ecx,8000h			; 32K
 		sub ecx,esi			; Number of bytes to copy
-		add esi,(real_mode_seg << 4)	; Pointer to source
+		add esi,core_real_mode		; Pointer to source
                 mov edi,free_high_memory	; Copy to free high memory
 
                 call bcopy			; Transfer to high memory
@@ -359,7 +359,7 @@ setup_command_line:
 		; New cmdline protocol
 		; Store 32-bit (flat) pointer to command line
 		; This is the "high" location, since we have bzImage
-		mov dword [fs:su_cmd_line_ptr],(real_mode_seg << 4)+cmd_line_here
+		mov dword [fs:su_cmd_line_ptr],cmd_line
 		mov word [HeapEnd],linux_stack
 		mov word [fs:su_heapend],linux_stack-512
 		jmp .setup_done
@@ -422,7 +422,7 @@ setup_move:
 ; Loading low: move real_mode stuff to 90000h, then move the kernel down
 		mov eax,90000h
 		stosd
-		mov eax,real_mode_seg << 4
+		mov eax,core_real_mode
 		stosd
 		movzx eax,word [CmdLineEnd]
 		stosd
diff --git a/core/syslinux.ld b/core/syslinux.ld
index df7242e3..f5039204 100644
--- a/core/syslinux.ld
+++ b/core/syslinux.ld
@@ -226,9 +226,20 @@ SECTIONS
 	__high_clear_len = __high_clear_end - __high_clear_start;
 	__high_clear_dwords = (__high_clear_len + 3) >> 2;
 
+	/*
+	 * Special 16-bit segments
+	 */
+	. = ALIGN(65536);
+	.xfer_buf (NOLOAD) : {
+		*(.xfer_buf)
+	}
+	xfer_buf_seg = core_xfer_buf >> 4;
 
-	__assert_high = ASSERT(__high_clear_end <= core_xfer_buf,
-	"auxseg/lowmem region collides with xfer_buf_seg");
+	. = ALIGN(65536);
+	.real_mode (NOLOAD) : {
+		*(.real_mode)
+	}
+	real_mode_seg = core_real_mode >> 4;
 
 	/*
 	 * 32-bit code.  This is a hack for the moment due to the