drivers/firmware/google/coreboot_table.c

   1 /*
   2  * coreboot_table.c
   3  *
   4  * Module providing coreboot table access.
   5  *
   6  * Copyright 2017 Google Inc.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License v2.0 as published by
  10  * the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  */
  17
  18 #include <linux/err.h>
  19 #include <linux/init.h>
  20 #include <linux/io.h>
  21 #include <linux/kernel.h>
  22 #include <linux/module.h>
  23
  24 #include "coreboot_table.h"
  25
  26 struct coreboot_table_entry {
  27         u32 tag;
  28         u32 size;
  29 };
  30
  31 static struct coreboot_table_header __iomem *ptr_header;
  32
  33 /*
  34  * This function parses the coreboot table for an entry that contains the base
  35  * address of the given entry tag. The coreboot table consists of a header
  36  * directly followed by a number of small, variable-sized entries, which each
  37  * contain an identifying tag and their length as the first two fields.
  38  */
  39 int coreboot_table_find(int tag, void *data, size_t data_size)
  40 {
  41         struct coreboot_table_header header;
  42         struct coreboot_table_entry entry;
  43         void *ptr_entry;
  44         int i;
  45
  46         if (!ptr_header)
  47                 return -EPROBE_DEFER;
  48
  49         memcpy_fromio(&header, ptr_header, sizeof(header));
  50
  51         if (strncmp(header.signature, "LBIO", sizeof(header.signature))) {
  52                 pr_warn("coreboot_table: coreboot table missing or corrupt!\n");
  53                 return -ENODEV;
  54         }
  55
  56         ptr_entry = (void *)ptr_header + header.header_bytes;
  57
  58         for (i = 0; i < header.table_entries; i++) {
  59                 memcpy_fromio(&entry, ptr_entry, sizeof(entry));
  60                 if (entry.tag == tag) {
  61                         if (data_size < entry.size)
  62                                 return -EINVAL;
  63
  64                         memcpy_fromio(data, ptr_entry, entry.size);
  65
  66                         return 0;
  67                 }
  68
  69                 ptr_entry += entry.size;
  70         }
  71
  72         return -ENOENT;
  73 }
  74 EXPORT_SYMBOL(coreboot_table_find);
  75
  76 int coreboot_table_init(void __iomem *ptr)
  77 {
  78         ptr_header = ptr;
  79
  80         return 0;
  81 }
  82 EXPORT_SYMBOL(coreboot_table_init);
  83
  84 int coreboot_table_exit(void)
  85 {
  86         if (ptr_header)
  87                 iounmap(ptr_header);
  88
  89         return 0;
  90 }
  91 EXPORT_SYMBOL(coreboot_table_exit);
  92
  93 MODULE_AUTHOR("Google, Inc.");
  94 MODULE_LICENSE("GPL");