drivers/firmware/efi/memattr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.org>
   4  */
   5
   6 #define pr_fmt(fmt)     "efi: memattr: " fmt
   7
   8 #include <linux/efi.h>
   9 #include <linux/init.h>
  10 #include <linux/io.h>
  11 #include <linux/memblock.h>
  12
  13 #include <asm/early_ioremap.h>
  14
  15 static int __initdata tbl_size;
  16 unsigned long __ro_after_init efi_mem_attr_table = EFI_INVALID_TABLE_ADDR;
  17
  18 /*
  19  * Reserve the memory associated with the Memory Attributes configuration
  20  * table, if it exists.
  21  */
  22 int __init efi_memattr_init(void)
  23 {
  24         efi_memory_attributes_table_t *tbl;
  25
  26         if (efi_mem_attr_table == EFI_INVALID_TABLE_ADDR)
  27                 return 0;
  28
  29         tbl = early_memremap(efi_mem_attr_table, sizeof(*tbl));
  30         if (!tbl) {
  31                 pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
  32                        efi_mem_attr_table);
  33                 return -ENOMEM;
  34         }
  35
  36         if (tbl->version > 2) {
  37                 pr_warn("Unexpected EFI Memory Attributes table version %d\n",
  38                         tbl->version);
  39                 goto unmap;
  40         }
  41
  42         tbl_size = sizeof(*tbl) + tbl->num_entries * tbl->desc_size;
  43         memblock_reserve(efi_mem_attr_table, tbl_size);
  44         set_bit(EFI_MEM_ATTR, &efi.flags);
  45
  46 unmap:
  47         early_memunmap(tbl, sizeof(*tbl));
  48         return 0;
  49 }
  50
  51 /*
  52  * Returns a copy @out of the UEFI memory descriptor @in if it is covered
  53  * entirely by a UEFI memory map entry with matching attributes. The virtual
  54  * address of @out is set according to the matching entry that was found.
  55  */
  56 static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out)
  57 {
  58         u64 in_paddr = in->phys_addr;
  59         u64 in_size = in->num_pages << EFI_PAGE_SHIFT;
  60         efi_memory_desc_t *md;
  61
  62         *out = *in;
  63
  64         if (in->type != EFI_RUNTIME_SERVICES_CODE &&
  65             in->type != EFI_RUNTIME_SERVICES_DATA) {
  66                 pr_warn("Entry type should be RuntimeServiceCode/Data\n");
  67                 return false;
  68         }
  69
  70         if (PAGE_SIZE > EFI_PAGE_SIZE &&
  71             (!PAGE_ALIGNED(in->phys_addr) ||
  72              !PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {
  73                 /*
  74                  * Since arm64 may execute with page sizes of up to 64 KB, the
  75                  * UEFI spec mandates that RuntimeServices memory regions must
  76                  * be 64 KB aligned. We need to validate this here since we will
  77                  * not be able to tighten permissions on such regions without
  78                  * affecting adjacent regions.
  79                  */
  80                 pr_warn("Entry address region misaligned\n");
  81                 return false;
  82         }
  83
  84         for_each_efi_memory_desc(md) {
  85                 u64 md_paddr = md->phys_addr;
  86                 u64 md_size = md->num_pages << EFI_PAGE_SHIFT;
  87
  88                 if (!(md->attribute & EFI_MEMORY_RUNTIME))
  89                         continue;
  90                 if (md->virt_addr == 0 && md->phys_addr != 0) {
  91                         /* no virtual mapping has been installed by the stub */
  92                         break;
  93                 }
  94
  95                 if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)
  96                         continue;
  97
  98                 /*
  99                  * This entry covers the start of @in, check whether
 100                  * it covers the end as well.
 101                  */
 102                 if (md_paddr + md_size < in_paddr + in_size) {
 103                         pr_warn("Entry covers multiple EFI memory map regions\n");
 104                         return false;
 105                 }
 106
 107                 if (md->type != in->type) {
 108                         pr_warn("Entry type deviates from EFI memory map region type\n");
 109                         return false;
 110                 }
 111
 112                 out->virt_addr = in_paddr + (md->virt_addr - md_paddr);
 113
 114                 return true;
 115         }
 116
 117         pr_warn("No matching entry found in the EFI memory map\n");
 118         return false;
 119 }
 120
 121 /*
 122  * To be called after the EFI page tables have been populated. If a memory
 123  * attributes table is available, its contents will be used to update the
 124  * mappings with tightened permissions as described by the table.
 125  * This requires the UEFI memory map to have already been populated with
 126  * virtual addresses.
 127  */
 128 int __init efi_memattr_apply_permissions(struct mm_struct *mm,
 129                                          efi_memattr_perm_setter fn)
 130 {
 131         efi_memory_attributes_table_t *tbl;
 132         bool has_bti = false;
 133         int i, ret;
 134
 135         if (tbl_size <= sizeof(*tbl))
 136                 return 0;
 137
 138         /*
 139          * We need the EFI memory map to be setup so we can use it to
 140          * lookup the virtual addresses of all entries in the  of EFI
 141          * Memory Attributes table. If it isn't available, this
 142          * function should not be called.
 143          */
 144         if (WARN_ON(!efi_enabled(EFI_MEMMAP)))
 145                 return 0;
 146
 147         tbl = memremap(efi_mem_attr_table, tbl_size, MEMREMAP_WB);
 148         if (!tbl) {
 149                 pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
 150                        efi_mem_attr_table);
 151                 return -ENOMEM;
 152         }
 153
 154         if (tbl->version > 1 &&
 155             (tbl->flags & EFI_MEMORY_ATTRIBUTES_FLAGS_RT_FORWARD_CONTROL_FLOW_GUARD))
 156                 has_bti = true;
 157
 158         if (efi_enabled(EFI_DBG))
 159                 pr_info("Processing EFI Memory Attributes table:\n");
 160
 161         for (i = ret = 0; ret == 0 && i < tbl->num_entries; i++) {
 162                 efi_memory_desc_t md;
 163                 unsigned long size;
 164                 bool valid;
 165                 char buf[64];
 166
 167                 valid = entry_is_valid(efi_memdesc_ptr(tbl->entry, tbl->desc_size, i),
 168                                        &md);
 169                 size = md.num_pages << EFI_PAGE_SHIFT;
 170                 if (efi_enabled(EFI_DBG) || !valid)
 171                         pr_info("%s 0x%012llx-0x%012llx %s\n",
 172                                 valid ? "" : "!", md.phys_addr,
 173                                 md.phys_addr + size - 1,
 174                                 efi_md_typeattr_format(buf, sizeof(buf), &md));
 175
 176                 if (valid) {
 177                         ret = fn(mm, &md, has_bti);
 178                         if (ret)
 179                                 pr_err("Error updating mappings, skipping subsequent md's\n");
 180                 }
 181         }
 182         memunmap(tbl);
 183         return ret;
 184 }