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
15static int __initdata tbl_size;
16unsigned 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 */
22int __init efi_memattr_init(void)
23{
24 efi_memory_attributes_table_t *tbl;
25 unsigned long size;
26
27 if (efi_mem_attr_table == EFI_INVALID_TABLE_ADDR)
28 return 0;
29
30 tbl = early_memremap(phys_addr: efi_mem_attr_table, size: sizeof(*tbl));
31 if (!tbl) {
32 pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
33 efi_mem_attr_table);
34 return -ENOMEM;
35 }
36
37 if (tbl->version > 2) {
38 pr_warn("Unexpected EFI Memory Attributes table version %d\n",
39 tbl->version);
40 goto unmap;
41 }
42
43
44 /*
45 * Sanity check: the Memory Attributes Table contains up to 3 entries
46 * for each entry of type EfiRuntimeServicesCode in the EFI memory map.
47 * So if the size of the table exceeds 3x the size of the entire EFI
48 * memory map, there is clearly something wrong, and the table should
49 * just be ignored altogether.
50 */
51 size = tbl->num_entries * tbl->desc_size;
52 if (size > 3 * efi.memmap.nr_map * efi.memmap.desc_size) {
53 pr_warn(FW_BUG "Corrupted EFI Memory Attributes Table detected! (version == %u, desc_size == %u, num_entries == %u)\n",
54 tbl->version, tbl->desc_size, tbl->num_entries);
55 goto unmap;
56 }
57
58 tbl_size = sizeof(*tbl) + size;
59 memblock_reserve(base: efi_mem_attr_table, size: tbl_size);
60 set_bit(EFI_MEM_ATTR, addr: &efi.flags);
61
62unmap:
63 early_memunmap(addr: tbl, size: sizeof(*tbl));
64 return 0;
65}
66
67/*
68 * Returns a copy @out of the UEFI memory descriptor @in if it is covered
69 * entirely by a UEFI memory map entry with matching attributes. The virtual
70 * address of @out is set according to the matching entry that was found.
71 */
72static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out)
73{
74 u64 in_paddr = in->phys_addr;
75 u64 in_size = in->num_pages << EFI_PAGE_SHIFT;
76 efi_memory_desc_t *md;
77
78 *out = *in;
79
80 if (in->type != EFI_RUNTIME_SERVICES_CODE &&
81 in->type != EFI_RUNTIME_SERVICES_DATA) {
82 pr_warn("Entry type should be RuntimeServiceCode/Data\n");
83 return false;
84 }
85
86 if (PAGE_SIZE > EFI_PAGE_SIZE &&
87 (!PAGE_ALIGNED(in->phys_addr) ||
88 !PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {
89 /*
90 * Since arm64 may execute with page sizes of up to 64 KB, the
91 * UEFI spec mandates that RuntimeServices memory regions must
92 * be 64 KB aligned. We need to validate this here since we will
93 * not be able to tighten permissions on such regions without
94 * affecting adjacent regions.
95 */
96 pr_warn("Entry address region misaligned\n");
97 return false;
98 }
99
100 for_each_efi_memory_desc(md) {
101 u64 md_paddr = md->phys_addr;
102 u64 md_size = md->num_pages << EFI_PAGE_SHIFT;
103
104 if (!(md->attribute & EFI_MEMORY_RUNTIME))
105 continue;
106 if (md->virt_addr == 0 && md->phys_addr != 0) {
107 /* no virtual mapping has been installed by the stub */
108 break;
109 }
110
111 if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)
112 continue;
113
114 /*
115 * This entry covers the start of @in, check whether
116 * it covers the end as well.
117 */
118 if (md_paddr + md_size < in_paddr + in_size) {
119 pr_warn("Entry covers multiple EFI memory map regions\n");
120 return false;
121 }
122
123 if (md->type != in->type) {
124 pr_warn("Entry type deviates from EFI memory map region type\n");
125 return false;
126 }
127
128 out->virt_addr = in_paddr + (md->virt_addr - md_paddr);
129
130 return true;
131 }
132
133 pr_warn("No matching entry found in the EFI memory map\n");
134 return false;
135}
136
137/*
138 * To be called after the EFI page tables have been populated. If a memory
139 * attributes table is available, its contents will be used to update the
140 * mappings with tightened permissions as described by the table.
141 * This requires the UEFI memory map to have already been populated with
142 * virtual addresses.
143 */
144int __init efi_memattr_apply_permissions(struct mm_struct *mm,
145 efi_memattr_perm_setter fn)
146{
147 efi_memory_attributes_table_t *tbl;
148 bool has_bti = false;
149 int i, ret;
150
151 if (tbl_size <= sizeof(*tbl))
152 return 0;
153
154 /*
155 * We need the EFI memory map to be setup so we can use it to
156 * lookup the virtual addresses of all entries in the of EFI
157 * Memory Attributes table. If it isn't available, this
158 * function should not be called.
159 */
160 if (WARN_ON(!efi_enabled(EFI_MEMMAP)))
161 return 0;
162
163 tbl = memremap(offset: efi_mem_attr_table, size: tbl_size, flags: MEMREMAP_WB);
164 if (!tbl) {
165 pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
166 efi_mem_attr_table);
167 return -ENOMEM;
168 }
169
170 if (tbl->version > 1 &&
171 (tbl->flags & EFI_MEMORY_ATTRIBUTES_FLAGS_RT_FORWARD_CONTROL_FLOW_GUARD))
172 has_bti = true;
173
174 if (efi_enabled(EFI_DBG))
175 pr_info("Processing EFI Memory Attributes table:\n");
176
177 for (i = ret = 0; ret == 0 && i < tbl->num_entries; i++) {
178 efi_memory_desc_t md;
179 unsigned long size;
180 bool valid;
181 char buf[64];
182
183 valid = entry_is_valid(efi_memdesc_ptr(tbl->entry, tbl->desc_size, i),
184 out: &md);
185 size = md.num_pages << EFI_PAGE_SHIFT;
186 if (efi_enabled(EFI_DBG) || !valid)
187 pr_info("%s 0x%012llx-0x%012llx %s\n",
188 valid ? "" : "!", md.phys_addr,
189 md.phys_addr + size - 1,
190 efi_md_typeattr_format(buf, sizeof(buf), &md));
191
192 if (valid) {
193 ret = fn(mm, &md, has_bti);
194 if (ret)
195 pr_err("Error updating mappings, skipping subsequent md's\n");
196 }
197 }
198 memunmap(addr: tbl);
199 return ret;
200}
201