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
|
/*
* memconsole-x86-legacy.c
*
* EBDA specific parts of the memory based BIOS console.
*
* Copyright 2017 Google Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License v2.0 as published by
* the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/dmi.h>
#include <linux/mm.h>
#include <asm/bios_ebda.h>
#include <linux/acpi.h>
#include "memconsole.h"
#define BIOS_MEMCONSOLE_V1_MAGIC 0xDEADBABE
#define BIOS_MEMCONSOLE_V2_MAGIC (('M')|('C'<<8)|('O'<<16)|('N'<<24))
struct biosmemcon_ebda {
u32 signature;
union {
struct {
u8 enabled;
u32 buffer_addr;
u16 start;
u16 end;
u16 num_chars;
u8 wrapped;
} __packed v1;
struct {
u32 buffer_addr;
/* Misdocumented as number of pages! */
u16 num_bytes;
u16 start;
u16 end;
} __packed v2;
};
} __packed;
static char *memconsole_baseaddr;
static size_t memconsole_length;
static ssize_t memconsole_read(char *buf, loff_t pos, size_t count)
{
return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr,
memconsole_length);
}
static void found_v1_header(struct biosmemcon_ebda *hdr)
{
pr_info("memconsole: BIOS console v1 EBDA structure found at %p\n",
hdr);
pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num = %d\n",
hdr->v1.buffer_addr, hdr->v1.start,
hdr->v1.end, hdr->v1.num_chars);
memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr);
memconsole_length = hdr->v1.num_chars;
memconsole_setup(memconsole_read);
}
static void found_v2_header(struct biosmemcon_ebda *hdr)
{
pr_info("memconsole: BIOS console v2 EBDA structure found at %p\n",
hdr);
pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num_bytes = %d\n",
hdr->v2.buffer_addr, hdr->v2.start,
hdr->v2.end, hdr->v2.num_bytes);
memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr + hdr->v2.start);
memconsole_length = hdr->v2.end - hdr->v2.start;
memconsole_setup(memconsole_read);
}
/*
* Search through the EBDA for the BIOS Memory Console, and
* set the global variables to point to it. Return true if found.
*/
static bool memconsole_ebda_init(void)
{
unsigned int address;
size_t length, cur;
address = get_bios_ebda();
if (!address) {
pr_info("memconsole: BIOS EBDA non-existent.\n");
return false;
}
/* EBDA length is byte 0 of EBDA (in KB) */
length = *(u8 *)phys_to_virt(address);
length <<= 10; /* convert to bytes */
/*
* Search through EBDA for BIOS memory console structure
* note: signature is not necessarily dword-aligned
*/
for (cur = 0; cur < length; cur++) {
struct biosmemcon_ebda *hdr = phys_to_virt(address + cur);
/* memconsole v1 */
if (hdr->signature == BIOS_MEMCONSOLE_V1_MAGIC) {
found_v1_header(hdr);
return true;
}
/* memconsole v2 */
if (hdr->signature == BIOS_MEMCONSOLE_V2_MAGIC) {
found_v2_header(hdr);
return true;
}
}
pr_info("memconsole: BIOS console EBDA structure not found!\n");
return false;
}
static struct dmi_system_id memconsole_dmi_table[] __initdata = {
{
.ident = "Google Board",
.matches = {
DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."),
},
},
{}
};
MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table);
static bool __init memconsole_find(void)
{
if (!dmi_check_system(memconsole_dmi_table))
return false;
return memconsole_ebda_init();
}
static int __init memconsole_x86_init(void)
{
if (!memconsole_find())
return -ENODEV;
return memconsole_sysfs_init();
}
static void __exit memconsole_x86_exit(void)
{
memconsole_exit();
}
module_init(memconsole_x86_init);
module_exit(memconsole_x86_exit);
MODULE_AUTHOR("Google, Inc.");
MODULE_LICENSE("GPL");
|
