Commit | Line | Data |
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e561bc45 MW |
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> | |
cb887591 | 18 | #include <linux/io.h> |
e561bc45 MW |
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 | ||
24 | struct 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 | ||
cb887591 | 45 | static u32 memconsole_baseaddr; |
e561bc45 MW |
46 | static size_t memconsole_length; |
47 | ||
48 | static 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 | { | |
cb887591 ML |
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; | |
e561bc45 MW |
64 | } |
65 | ||
66 | static struct bin_attribute memconsole_bin_attr = { | |
67 | .attr = {.name = "log", .mode = 0444}, | |
68 | .read = memconsole_read, | |
69 | }; | |
70 | ||
71 | ||
cb887591 | 72 | static void __init found_v1_header(struct biosmemcon_ebda *hdr) |
e561bc45 | 73 | { |
cb887591 ML |
74 | pr_info("BIOS console v1 EBDA structure found at %p\n", hdr); |
75 | pr_info("BIOS console buffer at 0x%.8x, " | |
e561bc45 MW |
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; | |
cb887591 | 81 | memconsole_baseaddr = hdr->v1.buffer_addr; |
e561bc45 MW |
82 | } |
83 | ||
cb887591 | 84 | static void __init found_v2_header(struct biosmemcon_ebda *hdr) |
e561bc45 | 85 | { |
cb887591 ML |
86 | pr_info("BIOS console v2 EBDA structure found at %p\n", hdr); |
87 | pr_info("BIOS console buffer at 0x%.8x, " | |
e561bc45 MW |
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; | |
cb887591 | 93 | memconsole_baseaddr = hdr->v2.buffer_addr + hdr->v2.start; |
e561bc45 MW |
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 | */ | |
cb887591 | 100 | static bool __init found_memconsole(void) |
e561bc45 MW |
101 | { |
102 | unsigned int address; | |
103 | size_t length, cur; | |
104 | ||
105 | address = get_bios_ebda(); | |
106 | if (!address) { | |
cb887591 | 107 | pr_info("BIOS EBDA non-existent.\n"); |
e561bc45 MW |
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 | ||
cb887591 | 135 | pr_info("BIOS console EBDA structure not found!\n"); |
e561bc45 MW |
136 | return false; |
137 | } | |
138 | ||
139 | static 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 | }; | |
148 | MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table); | |
149 | ||
150 | static int __init memconsole_init(void) | |
151 | { | |
e561bc45 MW |
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; | |
cb887591 | 159 | return sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr); |
e561bc45 MW |
160 | } |
161 | ||
162 | static void __exit memconsole_exit(void) | |
163 | { | |
164 | sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr); | |
165 | } | |
166 | ||
167 | module_init(memconsole_init); | |
168 | module_exit(memconsole_exit); | |
169 | ||
170 | MODULE_AUTHOR("Google, Inc."); | |
171 | MODULE_LICENSE("GPL"); |