Re: [LinuxBIOS] [PATCH] Support other than 0xC000 ROMs in VM86

[Carl-Daniel Hailfinger]

Stefan? I think you wanted to Ack this as well. Alex will then commit.

Alex Beregszaszi wrote:
> If you say ack, let me commit this, as I missed my last opportunity to
> commit :)
> this patch changes the real_mode_switch_call_vga() function to jump to
> the addr given as an argument instead the hardcoded 0xc000.
>
> Also it changes the function to inline assembly and passes the arguments
> through that.

Can you commit the changes above as separate revisions? First the inline
assembly change, then the variable addr stuff. This makes the changes
easier to follow.
> Signed-off-by: Alex Beregszaszi

Acked-by: Carl-Daniel Hailfinger

Carl-Daniel
> Index: util/x86emu/vm86.c
>
> --- util/x86emu/vm86.c	(revision 494)
> +++ util/x86emu/vm86.c	(working copy)
> @@ -5,6 +5,7 @@
> Copyright (C) 2001 University of California.  LA-CC Number 01-67.
> Copyright (C) 2005 [e-mail]
> Copyright (C) 2007 coresystems GmbH
> Copyright (C) 2007 Siqon Ltd. (written by Alex Beregszaszi)
> 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
>
> @@ -98,7 +99,7 @@
>  );
>
> /* The address arguments to this function are PHYSICAL ADDRESSES */ 
> -static void real_mode_switch_call_vga(unsigned long devfn)
> +static void real_mode_switch_call_vga(unsigned long devfn, unsigned long addr)
>  {
>    __asm__ __volatile__ (
>    	/* paranoia -- does ecx get saved? not sure. 
> @@ -106,16 +107,12 @@
>    	 */
>    	"	pushal			\n"
>    	/* save the stack */
> "	mov 	%esp, __stack	\n"
> "	mov 	%%esp, __stack	\n"
> "	jmp 	1f		\n"
> "__stack: .long 0		\n"
> "1:\n"
> /* get devfn into %ecx */
> "	movl    %esp, %ebp	\n"
> // FIXME: why is this 8? 
> "	movl    8(%ebp), %ecx	\n"
> /* load 'our' gdt */
> "	lgdt	%cs:__mygdtaddr	\n"
> "	lgdt	%%cs:__mygdtaddr	\n"
>
> /*  This configures CS properly for real mode. */
> "	ljmp	$0x28, $__rms_16bit\n"
>
> @@ -128,17 +125,17 @@
>    	 * configurations (limits, writability, etc.) once 
>    	 * protected mode is turned off. 
>    	 */
> "	mov	$0x30, %ax	\n"
> "	mov	%ax, %ds       	\n"
> "	mov	%ax, %es       	\n"
> "	mov	%ax, %fs       	\n"
> "	mov	%ax, %gs       	\n"
> "	mov	%ax, %ss       	\n"
> "	mov	$0x30, %%ax	\n"
> "	mov	%%ax, %%ds       	\n"
> "	mov	%%ax, %%es       	\n"
> "	mov	%%ax, %%fs       	\n"
> "	mov	%%ax, %%gs       	\n"
> "	mov	%%ax, %%ss       	\n"
>
> /* Turn off protection (bit 0 in CR0) */
> "	movl	%cr0, %eax	\n"
> "	andl	$0xFFFFFFFE, %eax \n"
> "	movl	%eax, %cr0	\n"
> "	movl	%%cr0, %%eax	\n"
> "	andl	$0xFFFFFFFE, %%eax \n"
> "	movl	%%eax, %%cr0	\n"
>
> /* Now really going into real mode */
> "	ljmp	$0,  $__rms_real\n"
>
> @@ -148,33 +145,49 @@
>    	 * That way we can easily share it between real and
>    	 * protected, since the 16-bit ESP at segment 0 will 
>    	 * work for any case. */
> "	mov	$0x0, %ax	\n"
> "	mov	%ax, %ss	\n"
> "	movl	$0x1000, %eax	\n"
> "	movl	%eax, %esp	\n"
> "	mov	$0x0, %%ax	\n"
> "	mov	%%ax, %%ss	\n"
> "	movl	$0x1000, %%eax	\n"
> "	movl	%%eax, %%esp	\n"
>
> /* Load our 16 it idt */
> "	xor	%ax, %ax	\n"
> "	mov	%ax, %ds	\n"
> "	xor	%%ax, %%ax	\n"
> "	mov	%%ax, %%ds	\n"
>
> "	lidt	__myidt		\n"
>
> /* Dump zeros in the other segment registers */
> "	mov	%ax, %es       	\n"
> "	mov	%ax, %fs       	\n"
> "	mov	%ax, %gs       	\n"
> "	mov	$0x40, %ax	\n"
> "	mov	%ax, %ds	\n"
> "	mov	%cx, %ax	\n"
> "	mov	%%ax, %%es       	\n"
> "	mov	%%ax, %%fs       	\n"
> "	mov	%%ax, %%gs       	\n"
> "	mov	$0x40, %%ax	\n"
> "	mov	%%ax, %%ds	\n"
> "	mov	%%cx, %%ax	\n"
>
> /* run VGA BIOS at 0xc000:0003 */
> "	lcall	$0xc000, $0x0003\n"
>
> +/*		"	lcall	$0xc000, $0x0003   \n"*/
> /* calculate addr */
> "       mov     %%edx, %%ebx      \n"
> "       add     $3, %%ebx        \n"
> "       and     $0xffff, %%ebx   \n"
> /* calculate segment */
> "       and     $0xf0000, %%edx  \n"
> "       shr     $4, %%edx        \n"
> "       pushw   %%dx             \n"
> "       pushw   %%bx             \n"
> "       mov     %%esp, %%ebp      \n"
> /* idea from bochs bios' rom_scan */
> /* call far ss:[bp+0] */
> "       .byte 0xff, 0x5e, 0x00   \n"
> "       add     $4, %%esp         \n"
> /* If we got here, just about done.
> Need to get back to protected mode
> */
> "	movl	%cr0, %eax	\n"
> "	orl	$0x0000001, %eax\n" /* PE = 1 */
> "	movl	%eax, %cr0	\n"
> "	movl	%%cr0, %%eax	\n"
> "	orl	$0x0000001, %%eax\n" /* PE = 1 */
> "	movl	%%eax, %%cr0	\n"
>
> /* Now that we are in protected mode
> jump to a 32 bit code segment.
>
> @@ -182,21 +195,23 @@
>    	"	data32	ljmp	$0x10, $vgarestart\n"
>    	"vgarestart:\n"
>    	"	.code32\n"
> "	movw	$0x18, %ax     	\n"
> "	mov	%ax, %ds       	\n"
> "	mov	%ax, %es	\n"
> "	mov	%ax, %fs	\n"
> "	mov	%ax, %gs	\n"
> "	mov	%ax, %ss	\n"
> "	movw	$0x18, %%ax     	\n"
> "	mov	%%ax, %%ds       	\n"
> "	mov	%%ax, %%es	\n"
> "	mov	%%ax, %%fs	\n"
> "	mov	%%ax, %%gs	\n"
> "	mov	%%ax, %%ss	\n"
>
> /* restore proper gdt and idt */
> "	lgdt	%cs:gdtarg	\n"
> "	lgdt	%%cs:gdtarg	\n"
>
> "	lidt	idtarg		\n"
>
> ".globl vga_exit		\n"
> "vga_exit:			\n"
> "	mov	__stack, %esp	\n"
> "	mov	__stack, %%esp	\n"
> "	popal			\n"
> :
> : "c" (devfn), "d" (addr)
> );
>
> }
>
> @@ -315,8 +330,8 @@
>    for (i = 0x400; i < 0x500; i++) {
>    	*(unsigned char *) i = 0;
>    }
> real_mode_switch_call_vga((dev->bus->secondary << 8) | dev->path.u.pci.devfn);
> real_mode_switch_call_vga((dev->bus->secondary << 8) | dev->path.u.pci.devfn, addr);
>
> }