2 * Copyright (c) 1997 Jonathan Lemon
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * $FreeBSD: src/sys/i386/i386/bioscall.s,v 1.6.2.1 2000/07/07 00:38:46 obrien Exp $
30 * Functions for calling x86 BIOS functions from the BSD kernel
33 #include <machine/asmacros.h>
37 #define data16 .byte 0x66
41 bioscall_frame: .long 0
42 bioscall_stack: .long 0
46 * bios32(regs, offset, segment)
47 * struct bios_regs *regs;
54 mov %bp,_bioscall_vector+4
56 movl %ebp,_bioscall_vector
68 lcall *_bioscall_vector
76 movl $0,%eax /* presume success */
78 movl $1,%eax /* nope */
88 * bios16_call(regs, stack)
89 * struct bios_regs *regs;
95 addl $4,%ebp /* frame pointer */
96 movl %ebp,bioscall_frame /* ... save it */
101 * the problem with a full 32-bit stack segment is that 16-bit code
102 * tends to do a pushf, which only pushes %sp, not %esp. This value
103 * is then popped off (into %esp) which causes a page fault because
104 * it is the wrong address.
106 * the reverse problem happens for 16-bit stack addresses; the kernel
107 * code attempts to get the address of something on the stack, and the
108 * value returned is the address relative to %ss, not %ds.
110 * we fix this by installing a temporary stack at page 0, so the
111 * addresses are always valid in both 32 bit and 16 bit modes.
113 movl %esp,bioscall_stack /* save current stack location */
114 movl 8(%ebp),%esp /* switch to page 0 stack */
116 movl 4(%ebp),%ebp /* regs */
126 leal CNAME(bios16_jmp),%ebp
128 pushl %ebp /* reload %cs and */
129 lret /* ...continue below */
130 .globl CNAME(bios16_jmp)
133 lcall *_bioscall_vector /* 16-bit call */
136 pushl $0 /* success */
139 pushl $1 /* failure */
141 movl bioscall_frame,%ebp
143 movl 4(%ebp),%ebp /* regs */
152 popl %eax /* recover return value */
153 movl bioscall_stack,%esp /* return to normal stack */
161 pushl %ecx /* return address */
163 lret /* reload %cs on the way out */