xref: /openbmc/linux/drivers/firmware/efi/memattr.c (revision 4bb1eb3c)
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 > 1) {
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 (!(in->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))) {
71 		pr_warn("Entry attributes invalid: RO and XP bits both cleared\n");
72 		return false;
73 	}
74 
75 	if (PAGE_SIZE > EFI_PAGE_SIZE &&
76 	    (!PAGE_ALIGNED(in->phys_addr) ||
77 	     !PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {
78 		/*
79 		 * Since arm64 may execute with page sizes of up to 64 KB, the
80 		 * UEFI spec mandates that RuntimeServices memory regions must
81 		 * be 64 KB aligned. We need to validate this here since we will
82 		 * not be able to tighten permissions on such regions without
83 		 * affecting adjacent regions.
84 		 */
85 		pr_warn("Entry address region misaligned\n");
86 		return false;
87 	}
88 
89 	for_each_efi_memory_desc(md) {
90 		u64 md_paddr = md->phys_addr;
91 		u64 md_size = md->num_pages << EFI_PAGE_SHIFT;
92 
93 		if (!(md->attribute & EFI_MEMORY_RUNTIME))
94 			continue;
95 		if (md->virt_addr == 0 && md->phys_addr != 0) {
96 			/* no virtual mapping has been installed by the stub */
97 			break;
98 		}
99 
100 		if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)
101 			continue;
102 
103 		/*
104 		 * This entry covers the start of @in, check whether
105 		 * it covers the end as well.
106 		 */
107 		if (md_paddr + md_size < in_paddr + in_size) {
108 			pr_warn("Entry covers multiple EFI memory map regions\n");
109 			return false;
110 		}
111 
112 		if (md->type != in->type) {
113 			pr_warn("Entry type deviates from EFI memory map region type\n");
114 			return false;
115 		}
116 
117 		out->virt_addr = in_paddr + (md->virt_addr - md_paddr);
118 
119 		return true;
120 	}
121 
122 	pr_warn("No matching entry found in the EFI memory map\n");
123 	return false;
124 }
125 
126 /*
127  * To be called after the EFI page tables have been populated. If a memory
128  * attributes table is available, its contents will be used to update the
129  * mappings with tightened permissions as described by the table.
130  * This requires the UEFI memory map to have already been populated with
131  * virtual addresses.
132  */
133 int __init efi_memattr_apply_permissions(struct mm_struct *mm,
134 					 efi_memattr_perm_setter fn)
135 {
136 	efi_memory_attributes_table_t *tbl;
137 	int i, ret;
138 
139 	if (tbl_size <= sizeof(*tbl))
140 		return 0;
141 
142 	/*
143 	 * We need the EFI memory map to be setup so we can use it to
144 	 * lookup the virtual addresses of all entries in the  of EFI
145 	 * Memory Attributes table. If it isn't available, this
146 	 * function should not be called.
147 	 */
148 	if (WARN_ON(!efi_enabled(EFI_MEMMAP)))
149 		return 0;
150 
151 	tbl = memremap(efi_mem_attr_table, tbl_size, MEMREMAP_WB);
152 	if (!tbl) {
153 		pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
154 		       efi_mem_attr_table);
155 		return -ENOMEM;
156 	}
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);
178 			if (ret)
179 				pr_err("Error updating mappings, skipping subsequent md's\n");
180 		}
181 	}
182 	memunmap(tbl);
183 	return ret;
184 }
185