LXR linux/drivers/firmware/efi/rci2-table.c

   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