1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
/* $OpenBSD: pte.h,v 1.13 2011/03/23 16:54:35 pirofti Exp $ */
/* $NetBSD: pte.h,v 1.11 1998/02/06 21:58:05 thorpej Exp $ */
/*
*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgment:
* This product includes software developed by Charles D. Cranor and
* Washington University.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* pte.h rewritten by chuck based on the jolitz version, plus random
* info on the pentium and other processors found on the net. the
* goal of this rewrite is to provide enough documentation on the MMU
* hardware that the reader will be able to understand it without having
* to refer to a hardware manual.
*/
#ifndef _MACHINE_PTE_H_
#define _MACHINE_PTE_H_
/*
* i386 MMU hardware structure:
*
* the i386 MMU is a two-level MMU which maps 4GB of virtual memory.
* the pagesize is 4K (4096 [0x1000] bytes), although newer pentium
* processors can support a 4MB pagesize as well.
*
* the first level table (segment table?) is called a "page directory"
* and it contains 1024 page directory entries (PDEs). each PDE is
* 4 bytes (an int), so a PD fits in a single 4K page. this page is
* the page directory page (PDP). each PDE in a PDP maps 4MB of space
* (1024 * 4MB = 4GB). a PDE contains the physical address of the
* second level table: the page table. or, if 4MB pages are being used,
* then the PDE contains the PA of the 4MB page being mapped.
*
* a page table consists of 1024 page table entries (PTEs). each PTE is
* 4 bytes (an int), so a page table also fits in a single 4K page. a
* 4K page being used as a page table is called a page table page (PTP).
* each PTE in a PTP maps one 4K page (1024 * 4K = 4MB). a PTE contains
* the physical address of the page it maps and some flag bits (described
* below).
*
* the processor has a special register, "cr3", which points to the
* the PDP which is currently controlling the mappings of the virtual
* address space.
*
* the following picture shows the translation process for a 4K page:
*
* %cr3 register [PA of PDP]
* |
* |
* | bits <31-22> of VA bits <21-12> of VA bits <11-0>
* | index the PDP (0 - 1023) index the PTP are the page offset
* | | | |
* | v | |
* +--->+----------+ | |
* | PD Page | PA of v |
* | |---PTP-------->+------------+ |
* | 1024 PDE | | page table |--PTE--+ |
* | entries | | (aka PTP) | | |
* +----------+ | 1024 PTE | | |
* | entries | | |
* +------------+ | |
* | |
* bits <31-12> bits <11-0>
* p h y s i c a l a d d r
*
* the i386 caches PTEs in a TLB. it is important to flush out old
* TLB mappings when making a change to a mappings. writing to the
* %cr3 will flush the entire TLB. newer processors also have an
* instruction that will invalidate the mapping of a single page (which
* is useful if you are changing a single mappings because it preserves
* all the cached TLB entries).
*
* as shows, bits 31-12 of the PTE contain PA of the page being mapped.
* the rest of the PTE is defined as follows:
* bit# name use
* 11 n/a available for OS use, hardware ignores it
* 10 n/a available for OS use, hardware ignores it
* 9 n/a available for OS use, hardware ignores it
* 8 G global bit (see discussion below)
* 7 PS page size [for PDEs] (0=4k, 1=4M <if supported>)
* 6 D dirty (modified) page
* 5 A accessed (referenced) page
* 4 PCD cache disable
* 3 PWT prevent write through (cache)
* 2 U/S user/supervisor bit (0=supervisor only, 1=both u&s)
* 1 R/W read/write bit (0=read only, 1=read-write)
* 0 P present (valid)
*
* notes:
* - on the i386 the R/W bit is ignored if processor is in supervisor
* state (bug!)
* - PS is only supported on newer processors
* - PTEs with the G bit are global in the sense that they are not
* flushed from the TLB when %cr3 is written (to flush, use the
* "flush single page" instruction). this is only supported on
* newer processors. this bit can be used to keep the kernel's
* TLB entries around while context switching. since the kernel
* is mapped into all processes at the same place it does not make
* sense to flush these entries when switching from one process'
* pmap to another.
*/
#if !defined(_LOCORE)
/*
* here we define the data types for PDEs and PTEs
*/
typedef u_int32_t pd_entry_t; /* PDE */
typedef u_int32_t pt_entry_t; /* PTE */
#endif
/*
* now we define various for playing with virtual addresses
*/
#define PDSHIFT 22 /* offset of PD index in VA */
#define NBPD (1 << PDSHIFT) /* # bytes mapped by PD (4MB) */
#define PDOFSET (NBPD-1) /* mask for non-PD part of VA */
#if 0 /* not used? */
#define NPTEPD (NBPD / NBPG) /* # of PTEs in a PD */
#else
#define PTES_PER_PTP (NBPD / NBPG) /* # of PTEs in a PTP */
#endif
#define PD_MASK 0xffc00000 /* page directory address bits */
#define PT_MASK 0x003ff000 /* page table address bits */
/*
* here we define the bits of the PDE/PTE, as described above:
*
* XXXCDC: need to rename these (PG_u == ugly).
*/
#define PG_V 0x00000001 /* valid entry */
#define PG_RO 0x00000000 /* read-only page */
#define PG_RW 0x00000002 /* read-write page */
#define PG_u 0x00000004 /* user accessible page */
#define PG_PROT 0x00000806 /* all protection bits */
#define PG_WT 0x00000008 /* write through */
#define PG_N 0x00000010 /* non-cacheable */
#define PG_U 0x00000020 /* has been used */
#define PG_M 0x00000040 /* has been modified */
#define PG_PAT 0x00000080 /* PAT bit. (on pte) */
#define PG_PS 0x00000080 /* 4MB page size (on pde) */
#define PG_G 0x00000100 /* global, don't TLB flush */
#define PG_AVAIL1 0x00000200 /* ignored by hardware */
#define PG_AVAIL2 0x00000400 /* ignored by hardware */
#define PG_AVAIL3 0x00000800 /* ignored by hardware */
#define PG_PATLG 0x00001000 /* PAT on large pages */
#define PG_FRAME 0xfffff000 /* page frame mask */
#define PG_LGFRAME 0xffc00000 /* large (4M) page frame mask */
/* Cacheability bits when we are using PAT */
#define PG_WB (0) /* The default */
#define PG_WC (PG_WT) /* WT and CD is WC */
#define PG_UCMINUS (PG_N) /* UC but mtrr can override */
#define PG_UC (PG_WT | PG_N) /* hard UC */
/*
* various shorthand protection codes
*/
#define PG_KR 0x00000000 /* kernel read-only */
#define PG_KW 0x00000002 /* kernel read-write */
/*
* page protection exception bits
*/
#define PGEX_P 0x01 /* protection violation (vs. no mapping) */
#define PGEX_W 0x02 /* exception during a write cycle */
#define PGEX_U 0x04 /* exception while in user mode (upl) */
#define PGEX_I 0x10 /* instruction fetch blocked by NX */
#endif /* _MACHINE_PTE_H_ */
|
