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 */
efi_memattr_init(void)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 */
entry_is_valid(const efi_memory_desc_t * in,efi_memory_desc_t * out)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 */
efi_memattr_apply_permissions(struct mm_struct * mm,efi_memattr_perm_setter fn)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((void *)tbl->entry + i * tbl->desc_size,
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 }
185