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
24struct 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
39static u8 *rci2_base;
40static u32 rci2_table_len;
41unsigned long rci2_table_phys __ro_after_init = EFI_INVALID_TABLE_ADDR;
42
43static 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
51static BIN_ATTR(rci2, S_IRUSR, raw_table_read, NULL, 0);
52
53static 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
79static 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}
150late_initcall(efi_rci2_sysfs_init);
151