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
|
/* This file is part of pgtblgen. */
/* SPDX-License-Identifier: GPL-2.0-only */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <inttypes.h>
static void usage(char *argv[])
{
printf("usage: %s -b <addr> -a <arch> -o <file>\n", argv[0]);
printf(" -a\t architecture. Supported: x86_64\n");
printf(" -b\t base address\n");
printf(" -o\t the file to write to\n");
printf(" -h\t show this help text\n");
}
/*
* For reference see "AMD64 ArchitectureProgrammer's Manual Volume 2",
* Document 24593-Rev. 3.31-July 2019 Chapter 5.3.4
*
* Page table attributes: WB, User+Supervisor, Present, Writeable
*/
#define _PRES (1ULL << 0)
#define _RW (1ULL << 1)
#define _US (1ULL << 2)
#define _A (1ULL << 5)
#define _D (1ULL << 6)
#define _PS (1ULL << 7)
#define _GEN_DIR(a) (_PRES | _RW | _US | _A | (a))
#define _GEN_PAGE(a) (_PRES | _RW | _US | _PS | _A | _D | (a))
/*
* Generate x86_64 page tables.
* The page tables needs to be placed at @base_address, and identity map
* the first @size_gib GiB of physical memory.
*/
static int gen_pgtbl_x86_64(const uint64_t base_address,
const size_t size_gib,
void **out_buf,
size_t *out_size)
{
uint64_t *entry;
if (!out_size || !out_buf)
return 1;
*out_size = (size_gib + 2) * 4096;
*out_buf = malloc(*out_size);
if (!*out_buf)
return 1;
memset(*out_buf, 0, *out_size);
entry = (uint64_t *)*out_buf;
/* Generate one PM4LE entry - point to PDPE */
entry[0] = _GEN_DIR(base_address + 4096);
entry += 512;
/* PDPE table - point to PDE */
for (size_t i = 0; i < size_gib; i++)
entry[i] = _GEN_DIR(base_address + 4096 * (i + 2));
entry += 512;
/* PDE tables - identity map 2MiB pages */
for (size_t g = 0; g < size_gib; g++) {
for (size_t i = 0; i < 512; i++) {
uint64_t addr = ((1ULL << (12 + 9)) * i) | ((1ULL << (12 + 9 + 9)) * g);
entry[i] = _GEN_PAGE(addr);
}
entry += 512;
}
return 0;
}
int main(int argc, char *argv[])
{
int ret = 1;
uint64_t base_address = 0;
char *filename = NULL;
char *arch = NULL;
void *buf = NULL;
size_t buf_size = 0;
int c;
while ((c = getopt(argc, argv, "ho:a:b:")) != -1)
switch (c) {
case '?': /* falltrough */
case 'h':
usage(argv);
return 0;
case 'o':
filename = optarg;
break;
case 'a':
arch = optarg;
break;
case 'b':
base_address = strtoull(optarg, NULL, 0);
break;
default:
break;
}
if (!filename) {
fprintf(stderr, "E: Missing filename.\n");
goto done;
}
if (!arch) {
fprintf(stderr, "E: Missing architecture.\n");
goto done;
} else if (strcmp(arch, "x86_64") != 0) {
fprintf(stderr, "E: Unsupported architecture.\n");
goto done;
}
if (base_address & 4095) {
fprintf(stderr, "E: Base address not 4 KiB aligned\n");
goto done;
}
/* FIXME: Identity map 4GiB for now, increase if necessary */
if (strcmp(arch, "x86_64") == 0)
ret = gen_pgtbl_x86_64(base_address, 4, &buf, &buf_size);
if (ret) {
fprintf(stderr, "Failed to generate page tables\n");
goto done;
}
// write the table
FILE *fd = fopen(filename, "wb");
if (!fd) {
fprintf(stderr, "%s open failed: %s\n", filename, strerror(errno));
goto done;
}
if (fwrite(buf, 1, buf_size, fd) != buf_size) {
fprintf(stderr, "%s write failed: %s\n", filename, strerror(errno));
fclose(fd);
goto done;
}
if (fclose(fd)) {
fprintf(stderr, "%s close failed: %s\n", filename, strerror(errno));
goto done;
}
ret = 0;
done:
free(buf);
return ret;
}
|
