1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Extensible Firmware Interface
4 *
5 * Based on Extensible Firmware Interface Specification version 2.4
6 *
7 * Copyright (C) 2013, 2014 Linaro Ltd.
8 */
9
10#include <linux/efi.h>
11#include <linux/init.h>
12#include <linux/screen_info.h>
13
14#include <asm/efi.h>
15#include <asm/stacktrace.h>
16
17static bool region_is_misaligned(const efi_memory_desc_t *md)
18{
19	if (PAGE_SIZE == EFI_PAGE_SIZE)
20		return false;
21	return !PAGE_ALIGNED(md->phys_addr) ||
22	       !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
23}
24
25/*
26 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
27 * executable, everything else can be mapped with the XN bits
28 * set. Also take the new (optional) RO/XP bits into account.
29 */
30static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
31{
32	u64 attr = md->attribute;
33	u32 type = md->type;
34
35	if (type == EFI_MEMORY_MAPPED_IO)
36		return PROT_DEVICE_nGnRE;
37
38	if (region_is_misaligned(md)) {
39		static bool __initdata code_is_misaligned;
40
41		/*
42		 * Regions that are not aligned to the OS page size cannot be
43		 * mapped with strict permissions, as those might interfere
44		 * with the permissions that are needed by the adjacent
45		 * region's mapping. However, if we haven't encountered any
46		 * misaligned runtime code regions so far, we can safely use
47		 * non-executable permissions for non-code regions.
48		 */
49		code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
50
51		return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
52					  : pgprot_val(PAGE_KERNEL);
53	}
54
55	/* R-- */
56	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
57	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
58		return pgprot_val(PAGE_KERNEL_RO);
59
60	/* R-X */
61	if (attr & EFI_MEMORY_RO)
62		return pgprot_val(PAGE_KERNEL_ROX);
63
64	/* RW- */
65	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
66	     EFI_MEMORY_XP) ||
67	    type != EFI_RUNTIME_SERVICES_CODE)
68		return pgprot_val(PAGE_KERNEL);
69
70	/* RWX */
71	return pgprot_val(PAGE_KERNEL_EXEC);
72}
73
74int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
75{
76	pteval_t prot_val = create_mapping_protection(md);
77	bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
78				   md->type == EFI_RUNTIME_SERVICES_DATA);
79
80	/*
81	 * If this region is not aligned to the page size used by the OS, the
82	 * mapping will be rounded outwards, and may end up sharing a page
83	 * frame with an adjacent runtime memory region. Given that the page
84	 * table descriptor covering the shared page will be rewritten when the
85	 * adjacent region gets mapped, we must avoid block mappings here so we
86	 * don't have to worry about splitting them when that happens.
87	 */
88	if (region_is_misaligned(md))
89		page_mappings_only = true;
90
91	create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
92			   md->num_pages << EFI_PAGE_SHIFT,
93			   __pgprot(prot_val | PTE_NG), page_mappings_only);
94	return 0;
95}
96
97struct set_perm_data {
98	const efi_memory_desc_t	*md;
99	bool			has_bti;
100};
101
102static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
103{
104	struct set_perm_data *spd = data;
105	const efi_memory_desc_t *md = spd->md;
106	pte_t pte = __ptep_get(ptep);
107
108	if (md->attribute & EFI_MEMORY_RO)
109		pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
110	if (md->attribute & EFI_MEMORY_XP)
111		pte = set_pte_bit(pte, __pgprot(PTE_PXN));
112	else if (system_supports_bti_kernel() && spd->has_bti)
113		pte = set_pte_bit(pte, __pgprot(PTE_GP));
114	__set_pte(ptep, pte);
115	return 0;
116}
117
118int __init efi_set_mapping_permissions(struct mm_struct *mm,
119				       efi_memory_desc_t *md,
120				       bool has_bti)
121{
122	struct set_perm_data data = { md, has_bti };
123
124	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
125	       md->type != EFI_RUNTIME_SERVICES_DATA);
126
127	if (region_is_misaligned(md))
128		return 0;
129
130	/*
131	 * Calling apply_to_page_range() is only safe on regions that are
132	 * guaranteed to be mapped down to pages. Since we are only called
133	 * for regions that have been mapped using efi_create_mapping() above
134	 * (and this is checked by the generic Memory Attributes table parsing
135	 * routines), there is no need to check that again here.
136	 */
137	return apply_to_page_range(mm, md->virt_addr,
138				   md->num_pages << EFI_PAGE_SHIFT,
139				   set_permissions, &data);
140}
141
142/*
143 * UpdateCapsule() depends on the system being shutdown via
144 * ResetSystem().
145 */
146bool efi_poweroff_required(void)
147{
148	return efi_enabled(EFI_RUNTIME_SERVICES);
149}
150
151asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
152{
153	pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
154	return s;
155}
156
157static DEFINE_RAW_SPINLOCK(efi_rt_lock);
158
159void arch_efi_call_virt_setup(void)
160{
161	efi_virtmap_load();
162	__efi_fpsimd_begin();
163	raw_spin_lock(&efi_rt_lock);
164}
165
166void arch_efi_call_virt_teardown(void)
167{
168	raw_spin_unlock(&efi_rt_lock);
169	__efi_fpsimd_end();
170	efi_virtmap_unload();
171}
172
173asmlinkage u64 *efi_rt_stack_top __ro_after_init;
174
175asmlinkage efi_status_t __efi_rt_asm_recover(void);
176
177bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
178{
179	 /* Check whether the exception occurred while running the firmware */
180	if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
181		return false;
182
183	pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
184	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
185	clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
186
187	regs->regs[0]	= EFI_ABORTED;
188	regs->regs[30]	= efi_rt_stack_top[-1];
189	regs->pc	= (u64)__efi_rt_asm_recover;
190
191	if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
192		regs->regs[18] = efi_rt_stack_top[-2];
193
194	return true;
195}
196
197/* EFI requires 8 KiB of stack space for runtime services */
198static_assert(THREAD_SIZE >= SZ_8K);
199
200static int __init arm64_efi_rt_init(void)
201{
202	void *p;
203
204	if (!efi_enabled(EFI_RUNTIME_SERVICES))
205		return 0;
206
207	p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
208			   NUMA_NO_NODE, &&l);
209l:	if (!p) {
210		pr_warn("Failed to allocate EFI runtime stack\n");
211		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
212		return -ENOMEM;
213	}
214
215	efi_rt_stack_top = p + THREAD_SIZE;
216	return 0;
217}
218core_initcall(arm64_efi_rt_init);
219