Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1/*
2 * memconsole.c
3 *
4 * Infrastructure for importing the BIOS memory based console
5 * into the kernel log ringbuffer.
6 *
7 * Copyright 2010 Google Inc. All rights reserved.
8 */
9
10#include <linux/ctype.h>
11#include <linux/init.h>
12#include <linux/kernel.h>
13#include <linux/string.h>
14#include <linux/sysfs.h>
15#include <linux/kobject.h>
16#include <linux/module.h>
17#include <linux/dmi.h>
18#include <asm/bios_ebda.h>
19
20#define BIOS_MEMCONSOLE_V1_MAGIC 0xDEADBABE
21#define BIOS_MEMCONSOLE_V2_MAGIC (('M')|('C'<<8)|('O'<<16)|('N'<<24))
22
23struct biosmemcon_ebda {
24 u32 signature;
25 union {
26 struct {
27 u8 enabled;
28 u32 buffer_addr;
29 u16 start;
30 u16 end;
31 u16 num_chars;
32 u8 wrapped;
33 } __packed v1;
34 struct {
35 u32 buffer_addr;
36 /* Misdocumented as number of pages! */
37 u16 num_bytes;
38 u16 start;
39 u16 end;
40 } __packed v2;
41 };
42} __packed;
43
44static char *memconsole_baseaddr;
45static size_t memconsole_length;
46
47static ssize_t memconsole_read(struct file *filp, struct kobject *kobp,
48 struct bin_attribute *bin_attr, char *buf,
49 loff_t pos, size_t count)
50{
51 return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr,
52 memconsole_length);
53}
54
55static struct bin_attribute memconsole_bin_attr = {
56 .attr = {.name = "log", .mode = 0444},
57 .read = memconsole_read,
58};
59
60
61static void found_v1_header(struct biosmemcon_ebda *hdr)
62{
63 printk(KERN_INFO "BIOS console v1 EBDA structure found at %p\n", hdr);
64 printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
65 "start = %d, end = %d, num = %d\n",
66 hdr->v1.buffer_addr, hdr->v1.start,
67 hdr->v1.end, hdr->v1.num_chars);
68
69 memconsole_length = hdr->v1.num_chars;
70 memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr);
71}
72
73static void found_v2_header(struct biosmemcon_ebda *hdr)
74{
75 printk(KERN_INFO "BIOS console v2 EBDA structure found at %p\n", hdr);
76 printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
77 "start = %d, end = %d, num_bytes = %d\n",
78 hdr->v2.buffer_addr, hdr->v2.start,
79 hdr->v2.end, hdr->v2.num_bytes);
80
81 memconsole_length = hdr->v2.end - hdr->v2.start;
82 memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr
83 + hdr->v2.start);
84}
85
86/*
87 * Search through the EBDA for the BIOS Memory Console, and
88 * set the global variables to point to it. Return true if found.
89 */
90static bool found_memconsole(void)
91{
92 unsigned int address;
93 size_t length, cur;
94
95 address = get_bios_ebda();
96 if (!address) {
97 printk(KERN_INFO "BIOS EBDA non-existent.\n");
98 return false;
99 }
100
101 /* EBDA length is byte 0 of EBDA (in KB) */
102 length = *(u8 *)phys_to_virt(address);
103 length <<= 10; /* convert to bytes */
104
105 /*
106 * Search through EBDA for BIOS memory console structure
107 * note: signature is not necessarily dword-aligned
108 */
109 for (cur = 0; cur < length; cur++) {
110 struct biosmemcon_ebda *hdr = phys_to_virt(address + cur);
111
112 /* memconsole v1 */
113 if (hdr->signature == BIOS_MEMCONSOLE_V1_MAGIC) {
114 found_v1_header(hdr);
115 return true;
116 }
117
118 /* memconsole v2 */
119 if (hdr->signature == BIOS_MEMCONSOLE_V2_MAGIC) {
120 found_v2_header(hdr);
121 return true;
122 }
123 }
124
125 printk(KERN_INFO "BIOS console EBDA structure not found!\n");
126 return false;
127}
128
129static struct dmi_system_id memconsole_dmi_table[] __initdata = {
130 {
131 .ident = "Google Board",
132 .matches = {
133 DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."),
134 },
135 },
136 {}
137};
138MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table);
139
140static int __init memconsole_init(void)
141{
142 int ret;
143
144 if (!dmi_check_system(memconsole_dmi_table))
145 return -ENODEV;
146
147 if (!found_memconsole())
148 return -ENODEV;
149
150 memconsole_bin_attr.size = memconsole_length;
151
152 ret = sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
153
154 return ret;
155}
156
157static void __exit memconsole_exit(void)
158{
159 sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr);
160}
161
162module_init(memconsole_init);
163module_exit(memconsole_exit);
164
165MODULE_AUTHOR("Google, Inc.");
166MODULE_LICENSE("GPL");