More factoring of common code

1 files changed, 414 insertions, 0 deletions

diff --git a/bcopy32.inc b/bcopy32.inc
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index 00000000..daa061e9
--- /dev/null
+++ b/bcopy32.inc
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+;; $Id$
+;; -----------------------------------------------------------------------
+;;   
+;;   Copyright 1994-2002 H. Peter Anvin - All Rights Reserved
+;;
+;;   This program is free software; you can redistribute it and/or modify
+;;   it under the terms of the GNU General Public License as published by
+;;   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+;;   Bostom MA 02111-1307, USA; either version 2 of the License, or
+;;   (at your option) any later version; incorporated herein by reference.
+;;
+;; -----------------------------------------------------------------------
+
+;;
+;; bcopy32.inc
+;; 
+;; 32-bit bcopy routine for real mode
+;;
+
+;
+; 32-bit bcopy routine for real mode
+;
+; We enter protected mode, set up a flat 32-bit environment, run rep movsd
+; and then exit.  IMPORTANT: This code assumes cs == 0.
+;
+; This code is probably excessively anal-retentive in its handling of
+; segments, but this stuff is painful enough as it is without having to rely
+; on everything happening "as it ought to."
+;
+; IMPORTANT: This code must be capable of operating when copied to the
+; trackbuf area (1000h).  The routine bcopy_over_self handles this mode
+; of operation, including any necessary adjustments.
+;
+		align 4
+__bcopy_start:
+
+bcopy_gdt:	dw bcopy_gdt_size-1	; Null descriptor - contains GDT
+.adj1:		dd bcopy_gdt		; pointer for LGDT instruction
+		dw 0
+		dd 0000ffffh		; Code segment, use16, readable,
+		dd 00009b00h		; present, dpl 0, cover 64K
+		dd 0000ffffh		; Data segment, use16, read/write,
+		dd 008f9300h		; present, dpl 0, cover all 4G
+		dd 0000ffffh		; Data segment, use16, read/write,
+		dd 00009300h		; present, dpl 0, cover 64K
+bcopy_gdt_size:	equ $-bcopy_gdt
+
+bcopy:		push eax
+		pushf			; Saves, among others, the IF flag
+		push gs
+		push fs
+		push ds
+		push es
+		mov [cs:SavedSSSP],sp
+		mov ax,ss
+		mov [cs:SavedSSSP+2],ax
+
+		cli
+		call enable_a20
+
+.adj2:		o32 lgdt [cs:bcopy_gdt]
+		mov eax,cr0
+		or al,1
+		mov cr0,eax		; Enter protected mode
+		jmp 08h:.in_pm
+
+.in_pm:		mov ax,10h		; Data segment selector
+		mov es,ax
+		mov ds,ax
+
+		mov al,18h		; "Real-mode-like" data segment
+		mov ss,ax
+		mov fs,ax
+		mov gs,ax	
+	
+		a32 rep movsd		; Do our business
+		
+		mov es,ax		; Set to "real-mode-like"
+		mov ds,ax
+	
+		mov eax,cr0
+		and al,~1
+		mov cr0,eax		; Disable protected mode
+.adj3:		jmp 0:.in_rm
+
+.in_rm:		; Back in real mode
+		lss sp,[cs:SavedSSSP]
+		pop es
+		pop ds
+		pop fs
+		pop gs
+		call disable_a20
+
+		popf			; Re-enables interrupts
+		pop eax
+		ret
+
+;
+; Routines to enable and disable (yuck) A20.  These routines are gathered
+; from tips from a couple of sources, including the Linux kernel and
+; http://www.x86.org/.  The need for the delay to be as large as given here
+; is indicated by Donnie Barnes of RedHat, the problematic system being an
+; IBM ThinkPad 760EL.
+;
+; We typically toggle A20 twice for every 64K transferred.
+; 
+%define	io_delay	call _io_delay
+%define IO_DELAY_PORT	80h		; Invalid port (we hope!)
+%define disable_wait 	32		; How long to wait for a disable
+
+%define A20_DUNNO	0		; A20 type unknown
+%define A20_NONE	1		; A20 always on?
+%define A20_BIOS	2		; A20 BIOS enable
+%define A20_KBC		3		; A20 through KBC
+%define A20_FAST	4		; A20 through port 92h
+
+		align 2
+A20List		dw a20_dunno, a20_none, a20_bios, a20_kbc, a20_fast
+A20DList	dw a20d_dunno, a20d_none, a20d_bios, a20d_kbc, a20d_fast
+a20_adjust_cnt	equ ($-A20List)/2
+A20Type		dw A20_DUNNO		; A20 type unknown
+
+slow_out:	out dx, al		; Fall through
+
+_io_delay:	out IO_DELAY_PORT,al
+		out IO_DELAY_PORT,al
+		ret
+
+enable_a20:
+		pushad
+		mov byte [cs:A20Tries],255 ; Times to try to make this work
+
+try_enable_a20:
+;
+; Flush the caches
+;
+;		call try_wbinvd
+
+;
+; If the A20 type is known, jump straight to type
+;
+		mov bp,[cs:A20Type]
+		add bp,bp			; Convert to word offset
+.adj4:		jmp word [cs:bp+A20List]
+
+;
+; First, see if we are on a system with no A20 gate
+;
+a20_dunno:
+a20_none:
+		mov byte [cs:A20Type], A20_NONE
+		call a20_test
+		jnz a20_done
+
+;
+; Next, try the BIOS (INT 15h AX=2401h)
+;
+a20_bios:
+		mov byte [cs:A20Type], A20_BIOS
+		mov ax,2401h
+		pushf				; Some BIOSes muck with IF
+		int 15h
+		popf
+
+		call a20_test
+		jnz a20_done
+
+;
+; Enable the keyboard controller A20 gate
+;
+a20_kbc:
+		mov dl, 1			; Allow early exit
+		call empty_8042
+		jnz a20_done			; A20 live, no need to use KBC
+
+		mov byte [cs:A20Type], A20_KBC	; Starting KBC command sequence
+
+		mov al,0D1h			; Command write
+		out 064h, al
+		call empty_8042_uncond
+
+		mov al,0DFh			; A20 on
+		out 060h, al
+		call empty_8042_uncond
+
+		; Verify that A20 actually is enabled.  Do that by
+		; observing a word in low memory and the same word in
+		; the HMA until they are no longer coherent.  Note that
+		; we don't do the same check in the disable case, because
+		; we don't want to *require* A20 masking (SYSLINUX should
+		; work fine without it, if the BIOS does.)
+.kbc_wait:	push cx
+		xor cx,cx
+.kbc_wait_loop:
+		call a20_test
+		jnz a20_done_pop
+		loop .kbc_wait_loop
+
+		pop cx
+;
+; Running out of options here.  Final attempt: enable the "fast A20 gate"
+;
+a20_fast:
+		mov byte [cs:A20Type], A20_FAST	; Haven't used the KBC yet
+		in al, 092h
+		or al,02h
+		and al,~01h			; Don't accidentally reset the machine!
+		out 092h, al
+
+.fast_wait:	push cx
+		xor cx,cx
+.fast_wait_loop:
+		call a20_test
+		jnz a20_done_pop
+		loop .fast_wait_loop
+
+		pop cx
+
+;
+; Oh bugger.  A20 is not responding.  Try frobbing it again; eventually give up
+; and report failure to the user.
+;
+
+
+		dec byte [cs:A20Tries]
+		jnz try_enable_a20
+
+		mov si, err_a20
+		jmp abort_load
+;
+; A20 unmasked, proceed...
+;
+a20_done_pop:	pop cx
+a20_done:	popad
+		ret
+
+;
+; This routine tests if A20 is enabled (ZF = 0).  This routine
+; must not destroy any register contents.
+;
+a20_test:
+		push es
+		push cx
+		push ax
+		mov cx,0FFFFh		; HMA = segment 0FFFFh
+		mov es,cx
+		mov cx,32		; Loop count
+		mov ax,[cs:A20Test]
+.a20_wait:	inc ax
+		mov [cs:A20Test],ax
+		io_delay		; Serialize, and fix delay
+		cmp ax,[es:A20Test+10h]
+		loopz .a20_wait
+.a20_done:	pop ax
+		pop cx
+		pop es
+		ret
+
+disable_a20:
+		pushad
+;
+; Flush the caches
+;
+;		call try_wbinvd
+
+		mov bp,[cs:A20Type]
+		add bp,bp			; Convert to word offset
+.adj5:		jmp word [cs:bp+A20DList]
+
+a20d_bios:
+		mov ax,2400h
+		pushf				; Some BIOSes muck with IF
+		int 15h
+		popf
+		jmp short a20d_snooze
+
+;
+; Disable the "fast A20 gate"
+;
+a20d_fast:
+		in al, 092h
+		and al,~03h
+		out 092h, al
+		jmp short a20d_snooze
+
+;
+; Disable the keyboard controller A20 gate
+;
+a20d_kbc:
+		call empty_8042_uncond
+		mov al,0D1h
+		out 064h, al		; Command write
+		call empty_8042_uncond
+		mov al,0DDh		; A20 off
+		out 060h, al
+		call empty_8042_uncond
+		; Wait a bit for it to take effect
+a20d_snooze:
+		push cx
+		mov cx, disable_wait
+.delayloop:	call a20_test
+		jz .disabled
+		loop .delayloop
+.disabled:	pop cx
+a20d_dunno:
+a20d_none:
+		popad
+		ret
+
+;
+; Routine to empty the 8042 KBC controller.  If dl != 0
+; then we will test A20 in the loop and exit if A20 is
+; suddenly enabled.
+;
+empty_8042_uncond:
+		xor dl,dl
+empty_8042:
+		call a20_test
+		jz .a20_on
+		and dl,dl
+		jnz .done
+.a20_on:	io_delay
+		in al, 064h		; Status port
+		test al,1
+		jz .no_output
+		io_delay
+		in al, 060h		; Read input
+		jmp short empty_8042
+.no_output:
+		test al,2
+		jnz empty_8042
+		io_delay
+.done:		ret	
+
+;
+; WBINVD instruction; gets auto-eliminated on 386 CPUs
+;
+try_wbinvd:
+		wbinvd
+		ret
+
+;
+; bcopy_over_self:
+;
+; This routine is used to copy large blocks of code on top of
+; conventional memory (to 0:7c00).  We therefore have to move
+; necessary code into the trackbuf area before doing the copy,
+; and do adjustments to anything except BSS area references.
+;
+; After performing the copy, this routine resets the stack and
+; jumps to 0:7c00.
+;
+; Inputs:
+;	ESI, EDI, ECX	- same as bcopy
+;	EDX		- edx on invocation
+;	EAX		- esi on invocation
+;
+%define ADJUST	(__bcopy_start - trackbuf)
+
+		align 2
+adjlist		dw bcopy_gdt.adj1 - ADJUST
+		dw bcopy.adj2 + 5 - ADJUST
+		dw bcopy.adj3 + 1 - ADJUST
+		dw try_enable_a20.adj4 + 3 - ADJUST
+		dw disable_a20.adj5 + 3 - ADJUST
+adjlist_cnt	equ ($-adjlist)/2
+
+bcopy_over_self:
+		cli
+		cld
+		xor bx,bx
+		mov ds,bx
+		mov es,bx
+		mov ss,bx
+		mov sp,7c00h
+
+		push eax
+		push edx
+		push esi	
+		push edi
+		push ecx
+
+		mov si,__bcopy_start
+		mov di,trackbuf
+		mov cx,(__bcopy_end - __bcopy_start + 3) >> 2
+		rep movsd
+
+		mov si,A20List - ADJUST
+		mov cx,a20_adjust_cnt
+.adjust1:
+		sub word [si], ADJUST
+		inc si
+		inc si
+		loop .adjust1
+
+		mov si, adjlist
+		mov cx, adjlist_cnt
+.adjust2:
+		lodsw
+		xchg di,ax
+		sub word [di], ADJUST
+		loop .adjust2
+
+		jmp .next-ADJUST
+.next:
+		pop ecx
+		pop edi
+		pop esi
+		call bcopy
+		
+		pop edx
+		pop esi
+		jmp 0:7c00h
+__bcopy_end: