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 
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 
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 
79 int __init efi_rci2_sysfs_init(void)
80 {
81 	struct kobject *tables_kobj;
82 	int ret = -ENOMEM;
83 
84 	rci2_base = memremap(rci2_table_phys,
85 			     sizeof(struct rci2_table_global_hdr),
86 			     MEMREMAP_WB);
87 	if (!rci2_base) {
88 		pr_debug("RCI2 table init failed - could not map RCI2 table\n");
89 		goto err;
90 	}
91 
92 	if (strncmp(rci2_base +
93 		    offsetof(struct rci2_table_global_hdr, rci2_sig),
94 		    RCI_SIGNATURE, 4)) {
95 		pr_debug("RCI2 table init failed - incorrect signature\n");
96 		ret = -ENODEV;
97 		goto err_unmap;
98 	}
99 
100 	rci2_table_len = *(u32 *)(rci2_base +
101 				  offsetof(struct rci2_table_global_hdr,
102 				  rci2_len));
103 
104 	memunmap(rci2_base);
105 
106 	if (!rci2_table_len) {
107 		pr_debug("RCI2 table init failed - incorrect table length\n");
108 		goto err;
109 	}
110 
111 	rci2_base = memremap(rci2_table_phys, rci2_table_len, MEMREMAP_WB);
112 	if (!rci2_base) {
113 		pr_debug("RCI2 table - could not map RCI2 table\n");
114 		goto err;
115 	}
116 
117 	if (checksum() != 0) {
118 		pr_debug("RCI2 table - incorrect checksum\n");
119 		ret = -ENODEV;
120 		goto err_unmap;
121 	}
122 
123 	tables_kobj = kobject_create_and_add("tables", efi_kobj);
124 	if (!tables_kobj) {
125 		pr_debug("RCI2 table - tables_kobj creation failed\n");
126 		goto err_unmap;
127 	}
128 
129 	bin_attr_rci2.size = rci2_table_len;
130 	bin_attr_rci2.private = rci2_base;
131 	ret = sysfs_create_bin_file(tables_kobj, &bin_attr_rci2);
132 	if (ret != 0) {
133 		pr_debug("RCI2 table - rci2 sysfs bin file creation failed\n");
134 		kobject_del(tables_kobj);
135 		kobject_put(tables_kobj);
136 		goto err_unmap;
137 	}
138 
139 	return 0;
140 
141  err_unmap:
142 	memunmap(rci2_base);
143  err:
144 	pr_debug("RCI2 table - sysfs initialization failed\n");
145 	return ret;
146 }
147 late_initcall(efi_rci2_sysfs_init);
148