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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * memconsole.c
4 *
5 * Architecture-independent parts of the memory based BIOS console.
6 *
7 * Copyright 2017 Google Inc.
8 */
9
10#include <linux/sysfs.h>
11#include <linux/kobject.h>
12#include <linux/module.h>
13
14#include "memconsole.h"
15
16static ssize_t memconsole_read(struct file *filp, struct kobject *kobp,
17 struct bin_attribute *bin_attr, char *buf,
18 loff_t pos, size_t count)
19{
20 ssize_t (*memconsole_read_func)(char *, loff_t, size_t);
21
22 memconsole_read_func = bin_attr->private;
23 if (WARN_ON_ONCE(!memconsole_read_func))
24 return -EIO;
25
26 return memconsole_read_func(buf, pos, count);
27}
28
29static struct bin_attribute memconsole_bin_attr = {
30 .attr = {.name = "log", .mode = 0444},
31 .read = memconsole_read,
32};
33
34void memconsole_setup(ssize_t (*read_func)(char *, loff_t, size_t))
35{
36 memconsole_bin_attr.private = read_func;
37}
38EXPORT_SYMBOL(memconsole_setup);
39
40int memconsole_sysfs_init(void)
41{
42 return sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
43}
44EXPORT_SYMBOL(memconsole_sysfs_init);
45
46void memconsole_exit(void)
47{
48 sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr);
49}
50EXPORT_SYMBOL(memconsole_exit);
51
52MODULE_AUTHOR("Google, Inc.");
53MODULE_DESCRIPTION("Architecture-independent parts of the memory based BIOS console");
54MODULE_LICENSE("GPL");
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 <linux/io.h>
19#include <asm/bios_ebda.h>
20
21#define BIOS_MEMCONSOLE_V1_MAGIC 0xDEADBABE
22#define BIOS_MEMCONSOLE_V2_MAGIC (('M')|('C'<<8)|('O'<<16)|('N'<<24))
23
24struct biosmemcon_ebda {
25 u32 signature;
26 union {
27 struct {
28 u8 enabled;
29 u32 buffer_addr;
30 u16 start;
31 u16 end;
32 u16 num_chars;
33 u8 wrapped;
34 } __packed v1;
35 struct {
36 u32 buffer_addr;
37 /* Misdocumented as number of pages! */
38 u16 num_bytes;
39 u16 start;
40 u16 end;
41 } __packed v2;
42 };
43} __packed;
44
45static u32 memconsole_baseaddr;
46static size_t memconsole_length;
47
48static ssize_t memconsole_read(struct file *filp, struct kobject *kobp,
49 struct bin_attribute *bin_attr, char *buf,
50 loff_t pos, size_t count)
51{
52 char *memconsole;
53 ssize_t ret;
54
55 memconsole = ioremap_cache(memconsole_baseaddr, memconsole_length);
56 if (!memconsole) {
57 pr_err("memconsole: ioremap_cache failed\n");
58 return -ENOMEM;
59 }
60 ret = memory_read_from_buffer(buf, count, &pos, memconsole,
61 memconsole_length);
62 iounmap(memconsole);
63 return ret;
64}
65
66static struct bin_attribute memconsole_bin_attr = {
67 .attr = {.name = "log", .mode = 0444},
68 .read = memconsole_read,
69};
70
71
72static void __init found_v1_header(struct biosmemcon_ebda *hdr)
73{
74 pr_info("BIOS console v1 EBDA structure found at %p\n", hdr);
75 pr_info("BIOS console buffer at 0x%.8x, "
76 "start = %d, end = %d, num = %d\n",
77 hdr->v1.buffer_addr, hdr->v1.start,
78 hdr->v1.end, hdr->v1.num_chars);
79
80 memconsole_length = hdr->v1.num_chars;
81 memconsole_baseaddr = hdr->v1.buffer_addr;
82}
83
84static void __init found_v2_header(struct biosmemcon_ebda *hdr)
85{
86 pr_info("BIOS console v2 EBDA structure found at %p\n", hdr);
87 pr_info("BIOS console buffer at 0x%.8x, "
88 "start = %d, end = %d, num_bytes = %d\n",
89 hdr->v2.buffer_addr, hdr->v2.start,
90 hdr->v2.end, hdr->v2.num_bytes);
91
92 memconsole_length = hdr->v2.end - hdr->v2.start;
93 memconsole_baseaddr = hdr->v2.buffer_addr + hdr->v2.start;
94}
95
96/*
97 * Search through the EBDA for the BIOS Memory Console, and
98 * set the global variables to point to it. Return true if found.
99 */
100static bool __init found_memconsole(void)
101{
102 unsigned int address;
103 size_t length, cur;
104
105 address = get_bios_ebda();
106 if (!address) {
107 pr_info("BIOS EBDA non-existent.\n");
108 return false;
109 }
110
111 /* EBDA length is byte 0 of EBDA (in KB) */
112 length = *(u8 *)phys_to_virt(address);
113 length <<= 10; /* convert to bytes */
114
115 /*
116 * Search through EBDA for BIOS memory console structure
117 * note: signature is not necessarily dword-aligned
118 */
119 for (cur = 0; cur < length; cur++) {
120 struct biosmemcon_ebda *hdr = phys_to_virt(address + cur);
121
122 /* memconsole v1 */
123 if (hdr->signature == BIOS_MEMCONSOLE_V1_MAGIC) {
124 found_v1_header(hdr);
125 return true;
126 }
127
128 /* memconsole v2 */
129 if (hdr->signature == BIOS_MEMCONSOLE_V2_MAGIC) {
130 found_v2_header(hdr);
131 return true;
132 }
133 }
134
135 pr_info("BIOS console EBDA structure not found!\n");
136 return false;
137}
138
139static struct dmi_system_id memconsole_dmi_table[] __initdata = {
140 {
141 .ident = "Google Board",
142 .matches = {
143 DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."),
144 },
145 },
146 {}
147};
148MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table);
149
150static int __init memconsole_init(void)
151{
152 if (!dmi_check_system(memconsole_dmi_table))
153 return -ENODEV;
154
155 if (!found_memconsole())
156 return -ENODEV;
157
158 memconsole_bin_attr.size = memconsole_length;
159 return sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
160}
161
162static void __exit memconsole_exit(void)
163{
164 sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr);
165}
166
167module_init(memconsole_init);
168module_exit(memconsole_exit);
169
170MODULE_AUTHOR("Google, Inc.");
171MODULE_LICENSE("GPL");