1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2020 Western Digital Corporation or its affiliates.
4 * Adapted from arch/arm64/kernel/efi.c
5 */
6
7 #include <linux/efi.h>
8 #include <linux/init.h>
9
10 #include <asm/efi.h>
11 #include <asm/pgtable.h>
12 #include <asm/pgtable-bits.h>
13
14 /*
15 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
16 * executable, everything else can be mapped with the XN bits
17 * set. Also take the new (optional) RO/XP bits into account.
18 */
19 static __init pgprot_t efimem_to_pgprot_map(efi_memory_desc_t *md)
20 {
21 u64 attr = md->attribute;
22 u32 type = md->type;
23
24 if (type == EFI_MEMORY_MAPPED_IO)
25 return PAGE_KERNEL;
26
27 /* R-- */
28 if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
29 (EFI_MEMORY_XP | EFI_MEMORY_RO))
30 return PAGE_KERNEL_READ;
31
32 /* R-X */
33 if (attr & EFI_MEMORY_RO)
34 return PAGE_KERNEL_READ_EXEC;
35
36 /* RW- */
37 if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
38 EFI_MEMORY_XP) ||
39 type != EFI_RUNTIME_SERVICES_CODE)
40 return PAGE_KERNEL;
41
42 /* RWX */
43 return PAGE_KERNEL_EXEC;
44 }
45
46 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
47 {
48 pgprot_t prot = __pgprot(pgprot_val(efimem_to_pgprot_map(md)) &
49 ~(_PAGE_GLOBAL));
50 int i;
51
52 /* RISC-V maps one page at a time */
53 for (i = 0; i < md->num_pages; i++)
54 create_pgd_mapping(mm->pgd, md->virt_addr + i * PAGE_SIZE,
55 md->phys_addr + i * PAGE_SIZE,
56 PAGE_SIZE, prot);
57 return 0;
58 }
59
60 static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
61 {
62 efi_memory_desc_t *md = data;
63 pte_t pte = ptep_get(ptep);
64 unsigned long val;
65
66 if (md->attribute & EFI_MEMORY_RO) {
67 val = pte_val(pte) & ~_PAGE_WRITE;
68 val |= _PAGE_READ;
69 pte = __pte(val);
70 }
71 if (md->attribute & EFI_MEMORY_XP) {
72 val = pte_val(pte) & ~_PAGE_EXEC;
73 pte = __pte(val);
74 }
75 set_pte(ptep, pte);
76
77 return 0;
78 }
79
80 int __init efi_set_mapping_permissions(struct mm_struct *mm,
81 efi_memory_desc_t *md,
82 bool ignored)
83 {
84 BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
85 md->type != EFI_RUNTIME_SERVICES_DATA);
86
87 /*
88 * Calling apply_to_page_range() is only safe on regions that are
89 * guaranteed to be mapped down to pages. Since we are only called
90 * for regions that have been mapped using efi_create_mapping() above
91 * (and this is checked by the generic Memory Attributes table parsing
92 * routines), there is no need to check that again here.
93 */
94 return apply_to_page_range(mm, md->virt_addr,
95 md->num_pages << EFI_PAGE_SHIFT,
96 set_permissions, md);
97 }
98
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.