vm86bios.s revision 282065 
1/*-
2 * Copyright (c) 1998 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: stable/10/sys/i386/i386/vm86bios.s 282065 2015-04-27 08:02:12Z kib $
27 */
28
29#include "opt_npx.h"
30
31#include <machine/asmacros.h>		/* miscellaneous asm macros */
32#include <machine/trap.h>
33
34#include "assym.s"
35
36#define SCR_NEWPTD	PCB_ESI		/* readability macros */
37#define SCR_VMFRAME	PCB_EBP		/* see vm86.c for explanation */
38#define SCR_STACK	PCB_ESP
39#define SCR_PGTABLE	PCB_EBX
40#define SCR_ARGFRAME	PCB_EIP
41#define SCR_TSS0	PCB_VM86
42#define SCR_TSS1	(PCB_VM86+4)
43
44	.data
45	ALIGN_DATA
46
47	.globl	vm86pcb
48
49vm86pcb:		.long	0
50
51	.text
52
53/*
54 * vm86_bioscall(struct trapframe_vm86 *vm86)
55 */
56ENTRY(vm86_bioscall)
57	movl	vm86pcb,%edx		/* scratch data area */
58	movl	4(%esp),%eax
59	movl	%eax,SCR_ARGFRAME(%edx)	/* save argument pointer */
60	pushl	%ebx
61	pushl	%ebp
62	pushl	%esi
63	pushl	%edi
64	pushl	%gs
65
66#ifdef DEV_NPX
67	pushfl
68	cli
69	movl	PCPU(CURTHREAD),%ecx
70	cmpl	%ecx,PCPU(FPCURTHREAD)	/* do we need to save fp? */
71	jne	1f
72	testl	%ecx,%ecx
73	je 	1f			/* no curproc/npxproc */
74	pushl	%edx
75	movl	TD_PCB(%ecx),%ecx
76	pushl	PCB_SAVEFPU(%ecx)
77	call	npxsave
78	addl	$4,%esp
79	popl	%edx			/* recover our pcb */
801:
81	popfl
82#endif
83
84	movl	SCR_VMFRAME(%edx),%ebx	/* target frame location */
85	movl	%ebx,%edi		/* destination */
86	movl    SCR_ARGFRAME(%edx),%esi	/* source (set on entry) */
87	movl	$VM86_FRAMESIZE/4,%ecx	/* sizeof(struct vm86frame)/4 */
88	cld
89	rep
90	movsl				/* copy frame to new stack */
91
92	movl	PCPU(CURPCB),%eax
93	pushl	%eax			/* save curpcb */
94	movl	%edx,PCPU(CURPCB)	/* set curpcb to vm86pcb */
95
96	movl	PCPU(TSS_GDT),%ebx	/* entry in GDT */
97	movl	0(%ebx),%eax
98	movl	%eax,SCR_TSS0(%edx)	/* save first word */
99	movl	4(%ebx),%eax
100	andl    $~0x200, %eax		/* flip 386BSY -> 386TSS */
101	movl	%eax,SCR_TSS1(%edx)	/* save second word */
102
103	movl	PCB_EXT(%edx),%edi	/* vm86 tssd entry */
104	movl	0(%edi),%eax
105	movl	%eax,0(%ebx)
106	movl	4(%edi),%eax
107	movl	%eax,4(%ebx)
108	movl	$GPROC0_SEL*8,%esi	/* GSEL(entry, SEL_KPL) */
109	ltr	%si
110
111	movl	%cr3,%eax
112	pushl	%eax			/* save address space */
113	movl	IdlePTD,%ecx
114	movl	%ecx,%ebx
115	addl	$KERNBASE,%ebx		/* va of Idle PTD */
116	movl	0(%ebx),%eax
117	pushl	%eax			/* old ptde != 0 when booting */
118	pushl	%ebx			/* keep for reuse */
119
120	movl	%esp,SCR_STACK(%edx)	/* save current stack location */
121
122	movl	SCR_NEWPTD(%edx),%eax	/* mapping for vm86 page table */
123	movl	%eax,0(%ebx)		/* ... install as PTD entry 0 */
124
125#if defined(PAE) || defined(PAE_TABLES)
126	movl	IdlePDPT,%ecx
127#endif
128	movl	%ecx,%cr3		/* new page tables */
129	movl	SCR_VMFRAME(%edx),%esp	/* switch to new stack */
130
131	pushl	%esp
132	call	vm86_prepcall		/* finish setup */
133	add	$4, %esp
134
135	/*
136	 * Return via doreti
137	 */
138	MEXITCOUNT
139	jmp	doreti
140
141
142/*
143 * vm86_biosret(struct trapframe_vm86 *vm86)
144 */
145ENTRY(vm86_biosret)
146	movl	vm86pcb,%edx		/* data area */
147
148	movl	4(%esp),%esi		/* source */
149	movl	SCR_ARGFRAME(%edx),%edi	/* destination */
150	movl	$VM86_FRAMESIZE/4,%ecx	/* size */
151	cld
152	rep
153	movsl				/* copy frame to original frame */
154
155	movl	SCR_STACK(%edx),%esp	/* back to old stack */
156	popl	%ebx			/* saved va of Idle PTD */
157	popl	%eax
158	movl	%eax,0(%ebx)		/* restore old pte */
159	popl	%eax
160	movl	%eax,%cr3		/* install old page table */
161
162	movl	PCPU(TSS_GDT),%ebx		/* entry in GDT */
163	movl	SCR_TSS0(%edx),%eax
164	movl	%eax,0(%ebx)		/* restore first word */
165	movl	SCR_TSS1(%edx),%eax
166	movl	%eax,4(%ebx)		/* restore second word */
167	movl	$GPROC0_SEL*8,%esi	/* GSEL(entry, SEL_KPL) */
168	ltr	%si
169
170	popl	PCPU(CURPCB)		/* restore curpcb/curproc */
171	movl	SCR_ARGFRAME(%edx),%edx	/* original stack frame */
172	movl	TF_TRAPNO(%edx),%eax	/* return (trapno) */
173
174	popl	%gs
175	popl	%edi
176	popl	%esi
177	popl	%ebp
178	popl	%ebx
179	ret				/* back to our normal program */
180