summaryrefslogtreecommitdiffstats
path: root/arch/arm64/kernel/efi.c
blob: e1be6c429810d0d583b645fcc6e0b3cbb2ea06a4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Extensible Firmware Interface
 *
 * Based on Extensible Firmware Interface Specification version 2.4
 *
 * Copyright (C) 2013, 2014 Linaro Ltd.
 */

#include <linux/efi.h>
#include <linux/init.h>

#include <asm/efi.h>

/*
 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
 * executable, everything else can be mapped with the XN bits
 * set. Also take the new (optional) RO/XP bits into account.
 */
static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
{
	u64 attr = md->attribute;
	u32 type = md->type;

	if (type == EFI_MEMORY_MAPPED_IO)
		return PROT_DEVICE_nGnRE;

	if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
		      "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
		/*
		 * If the region is not aligned to the page size of the OS, we
		 * can not use strict permissions, since that would also affect
		 * the mapping attributes of the adjacent regions.
		 */
		return pgprot_val(PAGE_KERNEL_EXEC);

	/* R-- */
	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
		return pgprot_val(PAGE_KERNEL_RO);

	/* R-X */
	if (attr & EFI_MEMORY_RO)
		return pgprot_val(PAGE_KERNEL_ROX);

	/* RW- */
	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
	     EFI_MEMORY_XP) ||
	    type != EFI_RUNTIME_SERVICES_CODE)
		return pgprot_val(PAGE_KERNEL);

	/* RWX */
	return pgprot_val(PAGE_KERNEL_EXEC);
}

/* we will fill this structure from the stub, so don't put it in .bss */
struct screen_info screen_info __section(".data");
EXPORT_SYMBOL(screen_info);

int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
{
	pteval_t prot_val = create_mapping_protection(md);
	bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
				   md->type == EFI_RUNTIME_SERVICES_DATA);

	if (!PAGE_ALIGNED(md->phys_addr) ||
	    !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
		/*
		 * If the end address of this region is not aligned to page
		 * size, the mapping is rounded up, and may end up sharing a
		 * page frame with the next UEFI memory region. If we create
		 * a block entry now, we may need to split it again when mapping
		 * the next region, and support for that is going to be removed
		 * from the MMU routines. So avoid block mappings altogether in
		 * that case.
		 */
		page_mappings_only = true;
	}

	create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
			   md->num_pages << EFI_PAGE_SHIFT,
			   __pgprot(prot_val | PTE_NG), page_mappings_only);
	return 0;
}

static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
{
	efi_memory_desc_t *md = data;
	pte_t pte = READ_ONCE(*ptep);

	if (md->attribute & EFI_MEMORY_RO)
		pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
	if (md->attribute & EFI_MEMORY_XP)
		pte = set_pte_bit(pte, __pgprot(PTE_PXN));
	set_pte(ptep, pte);
	return 0;
}

int __init efi_set_mapping_permissions(struct mm_struct *mm,
				       efi_memory_desc_t *md)
{
	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
	       md->type != EFI_RUNTIME_SERVICES_DATA);

	/*
	 * Calling apply_to_page_range() is only safe on regions that are
	 * guaranteed to be mapped down to pages. Since we are only called
	 * for regions that have been mapped using efi_create_mapping() above
	 * (and this is checked by the generic Memory Attributes table parsing
	 * routines), there is no need to check that again here.
	 */
	return apply_to_page_range(mm, md->virt_addr,
				   md->num_pages << EFI_PAGE_SHIFT,
				   set_permissions, md);
}

/*
 * UpdateCapsule() depends on the system being shutdown via
 * ResetSystem().
 */
bool efi_poweroff_required(void)
{
	return efi_enabled(EFI_RUNTIME_SERVICES);
}

asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
{
	pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
	return s;
}