freebsd-dev/sys/i386/boot/cdboot/asm.S

279 lines
5.8 KiB
ArmAsm
Raw Normal View History

(Part #2, after the Internet link broke totally yesterday.) This is the long-threatened ISO 9660 CD-ROM bootstrap code. This work has been sponsored by Plutotech International, Inc (who paid the initial work), and interface business GmbH (where i did most of the work). A big thanks also goes to Bruce Evans, for his continuing help and answering my stupid questions. The code is basically functioning, with the following caveats: . Rock Ridge attributes are not yet supported. . Only SCSI CD-ROMs are supported, since i fail to see any possibility to determine the drive type using BIOS functions. (Even for hard disks, this determination is done by a big hack only.) . El Torito specifies a lot of crap and useless misfeatures, but crucial things like the ability to figure out the CD TOC have been ``forgotten''. Thus, if you wanna boot a multisession CD, you need to know at which CD block your session starts, and need to speciffy it using the @ clause. . None of the CD-ROM controllers i've seen so far implements the full El Torito specification at all. Adaptec is probably the closest, but they miss on non-emulation booting (which would be the most logical choice for us). Thus, the current code bloats the 7.5 KB boot code up to 1.44 MB, in order to fake a `floppy' image. If you wanna use it, specify this file as the boot image on the command-line of the mksiosfs command (option -b). Caveat emptor: some versions of the Adaptec BIOS might even fail to access the CD-ROM at all, using the BIOS functions. I think i've notice this for ver 1.26, the code has been tested with ver 1.23. The boot string is as follows: [@sess-start] [filename] [-flags] sess-start Extend # where the last session starts, measured in CD-ROM blocks. filename As usual, but the input is case-insensitive by now (since we don't grok RR anyway). flags As usual, but -C (use CDROM root f/s) is default, so specifying -C will decactivate this option (which is probably not what you want :). A lot of cleanup work is probably required, and some of the files could/should be merged back to biosboot, perhaps made conditional on some #ifdef. The malloc implementation that comes with cdboot might also be useful for kzipboot. (I needed a malloc() since the root dir ain't fixed in size on a CD.) I've been testing all this with a 2.2-STABLE as the base for biosboot. I don't expect too many surprises, although i know the biosboot stuff has been changed a lot in -current lately. I'm sure Bruce will comment on all this here anyway. :-)
1997-07-11 05:52:41 +00:00
/*
* Mach Operating System
* Copyright (c) 1992, 1991 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*
* from: Mach, Revision 2.2 92/04/04 11:34:13 rpd
* $Id: asm.S,v 1.9 1996/03/08 07:27:52 bde Exp $
*/
/*
Copyright 1988, 1989, 1990, 1991, 1992
by Intel Corporation, Santa Clara, California.
All Rights Reserved
Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appears in all
copies and that both the copyright notice and this permission notice
appear in supporting documentation, and that the name of Intel
not be used in advertising or publicity pertaining to distribution
of the software without specific, written prior permission.
INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
.file "asm.s"
#include "asm.h"
CR0_PE_ON = 0x1
CR0_PE_OFF = 0xfffffffe
.text
/*
*
* real_to_prot()
* transfer from real mode to protected mode.
*/
ENTRY(real_to_prot)
/* guarantee that interrupt is disabled when in prot mode */
cli
/* load the gdtr */
addr32
data32
lgdt EXT(Gdtr)
/* set the PE bit of CR0 */
mov %cr0, %eax
data32
or $CR0_PE_ON, %eax
mov %eax, %cr0
/*
* make intrasegment jump to flush the processor pipeline and
* reload CS register
*/
data32
ljmp $0x18, $xprot
xprot:
/*
* we are in USE32 mode now
* set up the protected mode segment registers : DS, SS, ES, FS
*/
movw $0x20, %ax /* data segment */
mov %ax, %ds /* gas would waste a prefix byte for movw */
mov %ax, %ss
mov %ax, %es
movw $0x10, %ax /* flat segment */
mov %ax, %fs
#ifdef BDE_DEBUGGER
/* load idtr so we can debug */
lidt EXT(Idtr_prot)
#endif
ret
/*
*
* prot_to_real()
* transfer from protected mode to real mode
*
*/
ENTRY(prot_to_real)
/* Prepare %ax while we're still in a mode that gas understands. */
movw $0x30, %ax
/* Change to use16 mode. */
ljmp $0x28, $x16
x16:
mov %ax, %ds
mov %ax, %ss
mov %ax, %es
mov %ax, %fs
/* clear the PE bit of CR0 */
mov %cr0, %eax
data32
and $CR0_PE_OFF, %eax
mov %eax, %cr0
/*
* make intersegment jmp to flush the processor pipeline
* and reload CS register
*/
data32
ljmp $BOOTSEG, $xreal
xreal:
/*
* we are in real mode now
* set up the real mode segment registers : DS, SS, ES, FS
*/
mov %cs, %ax
mov %ax, %ds
mov %ax, %ss
mov %ax, %es
mov %ax, %fs
#ifdef BDE_DEBUGGER
/* load idtr so we can debug */
addr32
data32
lidt EXT(Idtr_real)
#endif
data32
ret
/*
* startprog(phyaddr)
* start the program on protected mode where phyaddr is the entry point
*
* XXX This whole mess should go away and we should run the boot code in
* flat 32 bit mode with it linked -T BOOTSEG. See the netboot code for
* how this is done.
*/
ENTRY(startprog)
push %ebp
mov %esp, %ebp
movl %esp, %eax /* Use eax as the old stack pointer */
/* convert the current stack to a 32 bit flat model */
movw $0x10, %bx
mov %bx, %ss
addl $(BOOTSEG<<4),%esp
/* copy the arguments from the old stack to the new stack */
pushl 0x14(%eax) /* &bootinfo */
pushl $0 /* was &nfsdiskless */
pushl $0 /* was esym */
pushl $0 /* was cyloffset */
pushl 0x10(%eax) /* bootdev */
pushl 0x0C(%eax) /* howto */
movl $(ourreturn),%ebx
addl $(BOOTSEG<<4),%ebx /* Fix it up for flat segments */
pushl %ebx /* our return address */
/* push on our entry address */
pushl $0x08 /* segment selector */
pushl 0x08(%eax) /* kernel entry address */
/* convert over the other data segs */
movw $0x10, %bx
mov %bx, %ds
mov %bx, %es
/* convert the PC (and code seg) */
lret
ourreturn:
/* For now there is not much we can do, just lock in a loop */
jmp ourreturn
/*
*
* pbzero( dst, cnt)
* where src is a virtual address and dst is a physical address
*/
ENTRY(pbzero)
push %ebp
mov %esp, %ebp
push %es
push %esi
push %edi
push %ecx
cld
/* set %es to point at the flat segment */
movw $0x10, %ax
mov %ax, %es
mov 0x8(%ebp), %edi /* destination */
mov 0xc(%ebp), %ecx /* count */
xorl %eax, %eax /* value 0 */
rep
stosb
pop %ecx
pop %edi
pop %esi
pop %es
pop %ebp
ret
/*
* pcpy(src, dst, cnt)
* where src is a virtual address and dst is a physical address
*/
ENTRY(pcpy)
push %ebp
mov %esp, %ebp
push %es
push %esi
push %edi
push %ecx
cld
/* set %es to point at the flat segment */
movw $0x10, %ax
mov %ax, %es
mov 0x8(%ebp), %esi /* source */
mov 0xc(%ebp), %edi /* destination */
mov 0x10(%ebp), %ecx /* count */
rep
movsb
pop %ecx
pop %edi
pop %esi
pop %es
pop %ebp
ret