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