1 /*-
2 * Copyright (c) 1997 Jonathan Lemon
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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.
13 *
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
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: releng/6.1/sys/i386/i386/bioscall.s 158179 2006-04-30 16:44:43Z cvs2svn $
27 */
28
29 /*
30 * Functions for calling x86 BIOS functions from the BSD kernel
31 */
32
33 #include <machine/asmacros.h>
34
35 #include "assym.s"
36
37 .data
38 ALIGN_DATA
39 bioscall_frame: .long 0
40 bioscall_stack: .long 0
41
42 .text
43 /*
44 * bios32(regs, offset, segment)
45 * struct bios_regs *regs;
46 * u_int offset;
47 * u_short segment;
48 */
49 ENTRY(bios32)
50 pushl %ebp
51 movl 16(%esp),%ebp
52 mov %bp,bioscall_vector+4
53 movl 12(%esp),%ebp
54 movl %ebp,bioscall_vector
55 movl 8(%esp),%ebp
56 pushl %ebx
57 pushl %esi
58 pushl %edi
59 movl 0(%ebp),%eax
60 movl 4(%ebp),%ebx
61 movl 8(%ebp),%ecx
62 movl 12(%ebp),%edx
63 movl 16(%ebp),%esi
64 movl 20(%ebp),%edi
65 pushl %ebp
66 lcall *bioscall_vector
67 popl %ebp
68 movl %eax,0(%ebp)
69 movl %ebx,4(%ebp)
70 movl %ecx,8(%ebp)
71 movl %edx,12(%ebp)
72 movl %esi,16(%ebp)
73 movl %edi,20(%ebp)
74 movl $0,%eax /* presume success */
75 jnc 1f
76 movl $1,%eax /* nope */
77 1:
78 popl %edi
79 popl %esi
80 popl %ebx
81 popl %ebp
82 ret
83
84
85 /*
86 * bios16_call(regs, stack)
87 * struct bios_regs *regs;
88 * char *stack;
89 */
90 ENTRY(bios16_call)
91 pushl %ebp
92 movl %esp,%ebp
93 addl $4,%ebp /* frame pointer */
94 movl %ebp,bioscall_frame /* ... save it */
95 pushl %ebx
96 pushl %esi
97 pushl %edi
98 /*
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.
103 *
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.
107 *
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.
110 */
111 movl %esp,bioscall_stack /* save current stack location */
112 movl 8(%ebp),%esp /* switch to page 0 stack */
113
114 movl 4(%ebp),%ebp /* regs */
115
116 movl 0(%ebp),%eax
117 movl 4(%ebp),%ebx
118 movl 8(%ebp),%ecx
119 movl 12(%ebp),%edx
120 movl 16(%ebp),%esi
121 movl 20(%ebp),%edi
122
123 pushl $BC32SEL
124 leal CNAME(bios16_jmp),%ebp
125 andl $PAGE_MASK,%ebp
126 pushl %ebp /* reload %cs and */
127 lret /* ...continue below */
128 .globl CNAME(bios16_jmp)
129 CNAME(bios16_jmp):
130 lcallw *bioscall_vector /* 16-bit call */
131
132 jc 1f
133 pushl $0 /* success */
134 jmp 2f
135 1:
136 pushl $1 /* failure */
137 2:
138 movl bioscall_frame,%ebp
139
140 movl 4(%ebp),%ebp /* regs */
141
142 movl %eax,0(%ebp)
143 movl %ebx,4(%ebp)
144 movl %ecx,8(%ebp)
145 movl %edx,12(%ebp)
146 movl %esi,16(%ebp)
147 movl %edi,20(%ebp)
148
149 popl %eax /* recover return value */
150 movl bioscall_stack,%esp /* return to normal stack */
151
152 popl %edi
153 popl %esi
154 popl %ebx
155 popl %ebp
156
157 movl (%esp),%ecx
158 pushl %ecx /* return address */
159 movl $KCSEL,4(%esp)
160 lret /* reload %cs on the way out */
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