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
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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
30 * Functions for calling x86 BIOS functions from the BSD kernel
33 #include <machine/asmacros.h>
39 bioscall_frame: .long 0
40 bioscall_stack: .long 0
44 * bios32(regs, offset, segment)
45 * struct bios_regs *regs;
52 mov %bp,bioscall_vector+4
54 movl %ebp,bioscall_vector
66 lcall *bioscall_vector
74 movl $0,%eax /* presume success */
76 movl $1,%eax /* nope */
86 * bios16_call(regs, stack)
87 * struct bios_regs *regs;
93 addl $4,%ebp /* frame pointer */
94 movl %ebp,bioscall_frame /* ... save it */
99 * the problem with a full 32-bit stack segment is that 16-bit code
100 * tends to do a pushf, which only pushes %sp, not %esp. This value
101 * is then popped off (into %esp) which causes a page fault because
102 * it is the wrong address.
104 * the reverse problem happens for 16-bit stack addresses; the kernel
105 * code attempts to get the address of something on the stack, and the
106 * value returned is the address relative to %ss, not %ds.
108 * we fix this by installing a temporary stack at page 0, so the
109 * addresses are always valid in both 32 bit and 16 bit modes.
111 movl %esp,bioscall_stack /* save current stack location */
112 movl 8(%ebp),%esp /* switch to page 0 stack */
114 movl 4(%ebp),%ebp /* regs */
124 leal CNAME(bios16_jmp),%ebp
126 pushl %ebp /* reload %cs and */
127 lret /* ...continue below */
128 .globl CNAME(bios16_jmp)
130 lcallw *bioscall_vector /* 16-bit call */
133 pushl $0 /* success */
136 pushl $1 /* failure */
138 movl bioscall_frame,%ebp
140 movl 4(%ebp),%ebp /* regs */
149 popl %eax /* recover return value */
150 movl bioscall_stack,%esp /* return to normal stack */
158 pushl %ecx /* return address */
160 lret /* reload %cs on the way out */