1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Export Runtime Configuration Interface Table Version 2 (RCI2)
4 * to sysfs
5 *
6 * Copyright (C) 2019 Dell Inc
7 * by Narendra K <Narendra.K@dell.com>
8 *
9 * System firmware advertises the address of the RCI2 Table via
10 * an EFI Configuration Table entry. This code retrieves the RCI2
11 * table from the address and exports it to sysfs as a binary
12 * attribute 'rci2' under /sys/firmware/efi/tables directory.
13 */
14
15 #include <linux/kobject.h>
16 #include <linux/device.h>
17 #include <linux/sysfs.h>
18 #include <linux/efi.h>
19 #include <linux/types.h>
20 #include <linux/io.h>
21
22 #define RCI_SIGNATURE "_RC_"
23
24 struct rci2_table_global_hdr {
25 u16 type;
26 u16 resvd0;
27 u16 hdr_len;
28 u8 rci2_sig[4];
29 u16 resvd1;
30 u32 resvd2;
31 u32 resvd3;
32 u8 major_rev;
33 u8 minor_rev;
34 u16 num_of_structs;
35 u32 rci2_len;
36 u16 rci2_chksum;
37 } __packed;
38
39 static u8 *rci2_base;
40 static u32 rci2_table_len;
41 unsigned long rci2_table_phys __ro_after_init = EFI_INVALID_TABLE_ADDR;
42
raw_table_read(struct file * file,struct kobject * kobj,struct bin_attribute * attr,char * buf,loff_t pos,size_t count)43 static ssize_t raw_table_read(struct file *file, struct kobject *kobj,
44 struct bin_attribute *attr, char *buf,
45 loff_t pos, size_t count)
46 {
47 memcpy(buf, attr->private + pos, count);
48 return count;
49 }
50
51 static BIN_ATTR(rci2, S_IRUSR, raw_table_read, NULL, 0);
52
checksum(void)53 static u16 checksum(void)
54 {
55 u8 len_is_odd = rci2_table_len % 2;
56 u32 chksum_len = rci2_table_len;
57 u16 *base = (u16 *)rci2_base;
58 u8 buf[2] = {0};
59 u32 offset = 0;
60 u16 chksum = 0;
61
62 if (len_is_odd)
63 chksum_len -= 1;
64
65 while (offset < chksum_len) {
66 chksum += *base;
67 offset += 2;
68 base++;
69 }
70
71 if (len_is_odd) {
72 buf[0] = *(u8 *)base;
73 chksum += *(u16 *)(buf);
74 }
75
76 return chksum;
77 }
78
efi_rci2_sysfs_init(void)79 static int __init efi_rci2_sysfs_init(void)
80 {
81 struct kobject *tables_kobj;
82 int ret = -ENOMEM;
83
84 if (rci2_table_phys == EFI_INVALID_TABLE_ADDR)
85 return 0;
86
87 rci2_base = memremap(rci2_table_phys,
88 sizeof(struct rci2_table_global_hdr),
89 MEMREMAP_WB);
90 if (!rci2_base) {
91 pr_debug("RCI2 table init failed - could not map RCI2 table\n");
92 goto err;
93 }
94
95 if (strncmp(rci2_base +
96 offsetof(struct rci2_table_global_hdr, rci2_sig),
97 RCI_SIGNATURE, 4)) {
98 pr_debug("RCI2 table init failed - incorrect signature\n");
99 ret = -ENODEV;
100 goto err_unmap;
101 }
102
103 rci2_table_len = *(u32 *)(rci2_base +
104 offsetof(struct rci2_table_global_hdr,
105 rci2_len));
106
107 memunmap(rci2_base);
108
109 if (!rci2_table_len) {
110 pr_debug("RCI2 table init failed - incorrect table length\n");
111 goto err;
112 }
113
114 rci2_base = memremap(rci2_table_phys, rci2_table_len, MEMREMAP_WB);
115 if (!rci2_base) {
116 pr_debug("RCI2 table - could not map RCI2 table\n");
117 goto err;
118 }
119
120 if (checksum() != 0) {
121 pr_debug("RCI2 table - incorrect checksum\n");
122 ret = -ENODEV;
123 goto err_unmap;
124 }
125
126 tables_kobj = kobject_create_and_add("tables", efi_kobj);
127 if (!tables_kobj) {
128 pr_debug("RCI2 table - tables_kobj creation failed\n");
129 goto err_unmap;
130 }
131
132 bin_attr_rci2.size = rci2_table_len;
133 bin_attr_rci2.private = rci2_base;
134 ret = sysfs_create_bin_file(tables_kobj, &bin_attr_rci2);
135 if (ret != 0) {
136 pr_debug("RCI2 table - rci2 sysfs bin file creation failed\n");
137 kobject_del(tables_kobj);
138 kobject_put(tables_kobj);
139 goto err_unmap;
140 }
141
142 return 0;
143
144 err_unmap:
145 memunmap(rci2_base);
146 err:
147 pr_debug("RCI2 table - sysfs initialization failed\n");
148 return ret;
149 }
150 late_initcall(efi_rci2_sysfs_init);
151