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 BIN_ATTR_SIMPLE_ADMIN_RO(rci2); 44 45 static u16 checksum(void) 46 { 47 u8 len_is_odd = rci2_table_len % 2; 48 u32 chksum_len = rci2_table_len; 49 u16 *base = (u16 *)rci2_base; 50 u8 buf[2] = {0}; 51 u32 offset = 0; 52 u16 chksum = 0; 53 54 if (len_is_odd) 55 chksum_len -= 1; 56 57 while (offset < chksum_len) { 58 chksum += *base; 59 offset += 2; 60 base++; 61 } 62 63 if (len_is_odd) { 64 buf[0] = *(u8 *)base; 65 chksum += *(u16 *)(buf); 66 } 67 68 return chksum; 69 } 70 71 static int __init efi_rci2_sysfs_init(void) 72 { 73 struct kobject *tables_kobj; 74 int ret = -ENOMEM; 75 76 if (rci2_table_phys == EFI_INVALID_TABLE_ADDR) 77 return 0; 78 79 rci2_base = memremap(rci2_table_phys, 80 sizeof(struct rci2_table_global_hdr), 81 MEMREMAP_WB); 82 if (!rci2_base) { 83 pr_debug("RCI2 table init failed - could not map RCI2 table\n"); 84 goto err; 85 } 86 87 if (strncmp(rci2_base + 88 offsetof(struct rci2_table_global_hdr, rci2_sig), 89 RCI_SIGNATURE, 4)) { 90 pr_debug("RCI2 table init failed - incorrect signature\n"); 91 ret = -ENODEV; 92 goto err_unmap; 93 } 94 95 rci2_table_len = *(u32 *)(rci2_base + 96 offsetof(struct rci2_table_global_hdr, 97 rci2_len)); 98 99 memunmap(rci2_base); 100 101 if (!rci2_table_len) { 102 pr_debug("RCI2 table init failed - incorrect table length\n"); 103 goto err; 104 } 105 106 rci2_base = memremap(rci2_table_phys, rci2_table_len, MEMREMAP_WB); 107 if (!rci2_base) { 108 pr_debug("RCI2 table - could not map RCI2 table\n"); 109 goto err; 110 } 111 112 if (checksum() != 0) { 113 pr_debug("RCI2 table - incorrect checksum\n"); 114 ret = -ENODEV; 115 goto err_unmap; 116 } 117 118 tables_kobj = kobject_create_and_add("tables", efi_kobj); 119 if (!tables_kobj) { 120 pr_debug("RCI2 table - tables_kobj creation failed\n"); 121 goto err_unmap; 122 } 123 124 bin_attr_rci2.size = rci2_table_len; 125 bin_attr_rci2.private = rci2_base; 126 ret = sysfs_create_bin_file(tables_kobj, &bin_attr_rci2); 127 if (ret != 0) { 128 pr_debug("RCI2 table - rci2 sysfs bin file creation failed\n"); 129 kobject_del(tables_kobj); 130 kobject_put(tables_kobj); 131 goto err_unmap; 132 } 133 134 return 0; 135 136 err_unmap: 137 memunmap(rci2_base); 138 err: 139 pr_debug("RCI2 table - sysfs initialization failed\n"); 140 return ret; 141 } 142 late_initcall(efi_rci2_sysfs_init); 143