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 | 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(offset: rci2_table_phys, |
88 | size: sizeof(struct rci2_table_global_hdr), |
89 | flags: 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(addr: 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(offset: rci2_table_phys, size: rci2_table_len, flags: 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(name: "tables" , parent: 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(kobj: tables_kobj, attr: &bin_attr_rci2); |
135 | if (ret != 0) { |
136 | pr_debug("RCI2 table - rci2 sysfs bin file creation failed\n" ); |
137 | kobject_del(kobj: tables_kobj); |
138 | kobject_put(kobj: tables_kobj); |
139 | goto err_unmap; |
140 | } |
141 | |
142 | return 0; |
143 | |
144 | err_unmap: |
145 | memunmap(addr: 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 | |