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Diffstat (limited to 'sys/i386/boot/biosboot/asm.S')
| -rw-r--r-- | sys/i386/boot/biosboot/asm.S | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/sys/i386/boot/biosboot/asm.S b/sys/i386/boot/biosboot/asm.S new file mode 100644 index 0000000..b291428 --- /dev/null +++ b/sys/i386/boot/biosboot/asm.S @@ -0,0 +1,260 @@ +/* + * 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 + * $Id$ + */ + + +/* + 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 + +.globl _ouraddr + .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 + mov $0x20, %eax + movw %ax, %ds + movw %ax, %ss + movw %ax, %es + + # load idtr so we can debug + lidt EXT(Idtr_prot) + + ret + +/* +# +# prot_to_real() +# transfer from protected mode to real mode +# +*/ + +ENTRY(prot_to_real) + + # set up a dummy stack frame for the second seg change. + movl _ouraddr, %eax + sarl $4, %eax + pushw %ax + movw $xreal, %ax # gas botches pushw $xreal - extra bytes 0, 0 + pushw %ax # decode to add %al, (%eax) (%al usually 0) + + # Change to use16 mode. + ljmp $0x28, $x16 + +x16: + # 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 + # using the fake stack frame set up earlier + # and reload CS register + lret + +xreal: + # we are in real mode now + # set up the real mode segment registers : DS, SS, ES + movw %cs, %ax + movw %ax, %ds + movw %ax, %ss + movw %ax, %es + + # load idtr so we can debug + addr32 + data32 + lidt EXT(Idtr_real) + + data32 + ret + +/* +# +# startprog(phyaddr) +# start the program on protected mode where phyaddr is the entry point +# +*/ + +ENTRY(startprog) + push %ebp + mov %esp, %ebp + + # get things we need into registers + movl 0x8(%ebp), %ecx # entry offset + movl 0x0c(%ebp), %eax # &argv + + # make a new stack at 0:0xa0000 (big segs) + mov $0x10, %ebx + movw %bx, %ss + movl $0xa0000, %ebx + movl %ebx, %esp + + # push some number of args onto the stack + pushl $0 # nominally a cyl offset in the boot. + pushl 0x8(%eax) # argv[2] = bootdev + pushl 0x4(%eax) # argv[1] = howto + pushl $0 # dummy 'return' address + + # push on our entry address + mov $0x08, %ebx # segment + pushl %ebx + pushl %ecx + + # convert over the other data segs + mov $0x10, %ebx + movw %bx, %ds + movw %bx, %es + + # convert the PC (and code seg) + lret +/* +# +# 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 + mov $0x10, %eax + movw %ax, %es + + mov 0x8(%ebp), %edi # destination + mov 0xc(%ebp), %ecx # count + mov $0x0, %eax # value + + 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 + mov $0x10, %eax + movw %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 + |
