9ed24653f7
Add code to the boot blocks to allow the user to place default boot strings on block 1 of the disk (2nd block), should the correct magic numbers be present. If the correct options are used it will 'delete' the name used from block1, thereby assuring that if the boot fails it won't be stuck in an infinite loop. the boot strings are set by the utility "nextboot" (not yet checked in, but being tested.) By default these changes should have no effect on existing installations and if compiled without the NAMEBLOCK option should be essentially identical to the old ones.
177 lines
3.8 KiB
ArmAsm
177 lines
3.8 KiB
ArmAsm
/*
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* Mach Operating System
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* Copyright (c) 1992, 1991 Carnegie Mellon University
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* All Rights Reserved.
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*
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* Permission to use, copy, modify and distribute this software and its
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* documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
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* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie Mellon
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* the rights to redistribute these changes.
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*
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* from: Mach, Revision 2.2 92/04/04 11:35:26 rpd
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* $Id: boot2.S,v 1.6 1995/01/25 21:37:40 bde Exp $
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*/
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#include "asm.h"
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/* Conventional GDT indexes. */
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#define BOOT_CS_INDEX 3
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#define BOOT_CS16_INDEX 5
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#define BOOT_DS_INDEX 4
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#ifdef BDE_DEBUGGER
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#define DB_CS_INDEX 14
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#define DB_CS16_INDEX 15
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#define DB_DS_INDEX 16
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#define GDT_INDEX 17
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#endif
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/* Vector numbers. */
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#define BREAKPOINT_VECTOR 3
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#define DEBUG_VECTOR 1
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/*
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* boot2() -- second stage boot
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* SP points to default string if found
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*/
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ENTRY(boot2)
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data32
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subl %eax, %eax
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mov %cs, %ax
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mov %ax, %ds
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mov %ax, %es
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data32
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shll $4, %eax
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addr32
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data32
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movl %esp, EXT(dflt_name)
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/* fix up GDT entries for bootstrap */
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#define FIXUP(gdt_index) \
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addr32; \
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movl %eax, EXT(Gdt)+(8*gdt_index)+2; /* actually movw %ax */ \
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addr32; \
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movb %bl, EXT(Gdt)+(8*gdt_index)+4
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data32
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shld $16, %eax, %ebx
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FIXUP(BOOT_CS_INDEX)
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FIXUP(BOOT_CS16_INDEX)
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FIXUP(BOOT_DS_INDEX)
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/* fix up GDT pointer */
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data32
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movl %eax, %ecx
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data32
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addl $ EXT(Gdt), %eax
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addr32
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data32
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movl %eax, EXT(Gdtr)+2
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#ifdef BDE_DEBUGGER
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/* fix up GDT entry for GDT */
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data32
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shld $16, %eax, %ebx
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FIXUP(GDT_INDEX)
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/* fix up IDT pointer */
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data32
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addl $ EXT(Idt), %ecx
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addr32
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data32
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movl %ecx, EXT(Idtr_prot)+2
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/* %es = vector table segment for a while */
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push %es
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data32
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subl %eax, %eax
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mov %ax, %es
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/* fix up GDT entries for bdb */
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data32
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movl $4*DEBUG_VECTOR, %esi
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addr32
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movl %es: 2(%esi), %eax /* actually movw to %ax */
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data32
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shll $4, %eax
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data32
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shld $16, %eax, %ebx
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FIXUP(DB_CS_INDEX)
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FIXUP(DB_CS16_INDEX)
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FIXUP(DB_DS_INDEX)
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/* Fetch entry points of bdb's protected mode trap handlers. These
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* are stored at 2 before the corresponding entry points for real mode.
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*/
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data32
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subl %ebx, %ebx
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addr32
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movl %es: (%esi), %ebx /* actually movw to %bx */
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data32
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subl %ecx, %ecx
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addr32
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movl %es: 4*(BREAKPOINT_VECTOR-DEBUG_VECTOR)(%esi), %ecx
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/* actually movw to %cx */
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/* %es = bdb segment for a while */
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data32
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shrl $4, %eax
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mov %ax, %es
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/* fix up IDT entries for bdb */
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data32
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subl $2, %ebx /* calculate EA to check it */
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jb 1f /* give up if it would trap */
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addr32
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movl %es: (%ebx), %eax /* actually movw to %ax */
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addr32
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movl %eax, EXT(Idt)+8*DEBUG_VECTOR /* actually movw %ax */
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1:
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data32
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subl $2, %ecx
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jb 1f
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addr32
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movl %es: (%ecx), %eax /* actually movw to %ax */
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addr32
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movl %eax, EXT(Idt)+8*BREAKPOINT_VECTOR /* actually movw %ax */
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1:
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/* finished with groping in real mode segments */
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pop %es
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#endif /* BDE_DEBUGGER */
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/* change to protected mode */
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data32
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call EXT(real_to_prot)
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/* clear the bss */
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movl $ EXT(edata), %edi /* no EXT(_edata) - krufty ld */
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movl $ EXT(end), %ecx /* or EXT(_end) */
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subl %edi, %ecx
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subb %al, %al
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rep
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stosb
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movzbl %dl, %edx /* discard head (%dh) and random high bits */
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pushl %edx
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call EXT(boot)
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oops:
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hlt
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jmp oops
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