drivers/firmware/efi/memattr.c

   1 /*
   2  * Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #define pr_fmt(fmt)     "efi: memattr: " fmt
  10
  11 #include <linux/efi.h>
  12 #include <linux/init.h>
  13 #include <linux/io.h>
  14 #include <linux/memblock.h>
  15
  16 #include <asm/early_ioremap.h>
  17
  18 static int __initdata tbl_size;
  19
  20 /*
  21  * Reserve the memory associated with the Memory Attributes configuration
  22  * table, if it exists.
  23  */
  24 int __init efi_memattr_init(void)
  25 {
  26         efi_memory_attributes_table_t *tbl;
  27
  28         if (efi.mem_attr_table == EFI_INVALID_TABLE_ADDR)
  29                 return 0;
  30
  31         tbl = early_memremap(efi.mem_attr_table, sizeof(*tbl));
  32         if (!tbl) {
  33                 pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
  34                        efi.mem_attr_table);
  35                 return -ENOMEM;
  36         }
  37
  38         if (tbl->version > 1) {
  39                 pr_warn("Unexpected EFI Memory Attributes table version %d\n",
  40                         tbl->version);
  41                 goto unmap;
  42         }
  43
  44         tbl_size = sizeof(*tbl) + tbl->num_entries * tbl->desc_size;
  45         memblock_reserve(efi.mem_attr_table, tbl_size);
  46         set_bit(EFI_MEM_ATTR, &efi.flags);
  47
  48 unmap:
  49         early_memunmap(tbl, sizeof(*tbl));
  50         return 0;
  51 }
  52
  53 /*
  54  * Returns a copy @out of the UEFI memory descriptor @in if it is covered
  55  * entirely by a UEFI memory map entry with matching attributes. The virtual
  56  * address of @out is set according to the matching entry that was found.
  57  */
  58 static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out)
  59 {
  60         u64 in_paddr = in->phys_addr;
  61         u64 in_size = in->num_pages << EFI_PAGE_SHIFT;
  62         efi_memory_desc_t *md;
  63
  64         *out = *in;
  65
  66         if (in->type != EFI_RUNTIME_SERVICES_CODE &&
  67             in->type != EFI_RUNTIME_SERVICES_DATA) {
  68                 pr_warn("Entry type should be RuntimeServiceCode/Data\n");
  69                 return false;
  70         }
  71
  72         if (!(in->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))) {
  73                 pr_warn("Entry attributes invalid: RO and XP bits both cleared\n");
  74                 return false;
  75         }
  76
  77         if (PAGE_SIZE > EFI_PAGE_SIZE &&
  78             (!PAGE_ALIGNED(in->phys_addr) ||
  79              !PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {
  80                 /*
  81                  * Since arm64 may execute with page sizes of up to 64 KB, the
  82                  * UEFI spec mandates that RuntimeServices memory regions must
  83                  * be 64 KB aligned. We need to validate this here since we will
  84                  * not be able to tighten permissions on such regions without
  85                  * affecting adjacent regions.
  86                  */
  87                 pr_warn("Entry address region misaligned\n");
  88                 return false;
  89         }
  90
  91         for_each_efi_memory_desc(md) {
  92                 u64 md_paddr = md->phys_addr;
  93                 u64 md_size = md->num_pages << EFI_PAGE_SHIFT;
  94
  95                 if (!(md->attribute & EFI_MEMORY_RUNTIME))
  96                         continue;
  97                 if (md->virt_addr == 0) {
  98                         /* no virtual mapping has been installed by the stub */
  99                         break;
 100                 }
 101
 102                 if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)
 103                         continue;
 104
 105                 /*
 106                  * This entry covers the start of @in, check whether
 107                  * it covers the end as well.
 108                  */
 109                 if (md_paddr + md_size < in_paddr + in_size) {
 110                         pr_warn("Entry covers multiple EFI memory map regions\n");
 111                         return false;
 112                 }
 113
 114                 if (md->type != in->type) {
 115                         pr_warn("Entry type deviates from EFI memory map region type\n");
 116                         return false;
 117                 }
 118
 119                 out->virt_addr = in_paddr + (md->virt_addr - md_paddr);
 120
 121                 return true;
 122         }
 123
 124         pr_warn("No matching entry found in the EFI memory map\n");
 125         return false;
 126 }
 127
 128 /*
 129  * To be called after the EFI page tables have been populated. If a memory
 130  * attributes table is available, its contents will be used to update the
 131  * mappings with tightened permissions as described by the table.
 132  * This requires the UEFI memory map to have already been populated with
 133  * virtual addresses.
 134  */
 135 int __init efi_memattr_apply_permissions(struct mm_struct *mm,
 136                                          efi_memattr_perm_setter fn)
 137 {
 138         efi_memory_attributes_table_t *tbl;
 139         int i, ret;
 140
 141         if (tbl_size <= sizeof(*tbl))
 142                 return 0;
 143
 144         /*
 145          * We need the EFI memory map to be setup so we can use it to
 146          * lookup the virtual addresses of all entries in the  of EFI
 147          * Memory Attributes table. If it isn't available, this
 148          * function should not be called.
 149          */
 150         if (WARN_ON(!efi_enabled(EFI_MEMMAP)))
 151                 return 0;
 152
 153         tbl = memremap(efi.mem_attr_table, tbl_size, MEMREMAP_WB);
 154         if (!tbl) {
 155                 pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
 156                        efi.mem_attr_table);
 157                 return -ENOMEM;
 158         }
 159
 160         if (efi_enabled(EFI_DBG))
 161                 pr_info("Processing EFI Memory Attributes table:\n");
 162
 163         for (i = ret = 0; ret == 0 && i < tbl->num_entries; i++) {
 164                 efi_memory_desc_t md;
 165                 unsigned long size;
 166                 bool valid;
 167                 char buf[64];
 168
 169                 valid = entry_is_valid((void *)tbl->entry + i * tbl->desc_size,
 170                                        &md);
 171                 size = md.num_pages << EFI_PAGE_SHIFT;
 172                 if (efi_enabled(EFI_DBG) || !valid)
 173                         pr_info("%s 0x%012llx-0x%012llx %s\n",
 174                                 valid ? "" : "!", md.phys_addr,
 175                                 md.phys_addr + size - 1,
 176                                 efi_md_typeattr_format(buf, sizeof(buf), &md));
 177
 178                 if (valid) {
 179                         ret = fn(mm, &md);
 180                         if (ret)
 181                                 pr_err("Error updating mappings, skipping subsequent md's\n");
 182                 }
 183         }
 184         memunmap(tbl);
 185         return ret;
 186 }