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/kmemleak.h>
 13#include <linux/screen_info.h>
 14#include <linux/vmalloc.h>
 15
 16#include <asm/efi.h>
 17#include <asm/stacktrace.h>
 18
 19static bool region_is_misaligned(const efi_memory_desc_t *md)
 20{
 21	if (PAGE_SIZE == EFI_PAGE_SIZE)
 22		return false;
 23	return !PAGE_ALIGNED(md->phys_addr) ||
 24	       !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
 25}
 26
 27/*
 28 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
 29 * executable, everything else can be mapped with the XN bits
 30 * set. Also take the new (optional) RO/XP bits into account.
 31 */
 32static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
 33{
 34	u64 attr = md->attribute;
 35	u32 type = md->type;
 36
 37	if (type == EFI_MEMORY_MAPPED_IO) {
 38		pgprot_t prot = __pgprot(PROT_DEVICE_nGnRE);
 39
 40		if (arm64_is_protected_mmio(md->phys_addr,
 41					    md->num_pages << EFI_PAGE_SHIFT))
 42			prot = pgprot_encrypted(prot);
 43		else
 44			prot = pgprot_decrypted(prot);
 45		return pgprot_val(prot);
 46	}
 47
 48	if (region_is_misaligned(md)) {
 49		static bool __initdata code_is_misaligned;
 50
 51		/*
 52		 * Regions that are not aligned to the OS page size cannot be
 53		 * mapped with strict permissions, as those might interfere
 54		 * with the permissions that are needed by the adjacent
 55		 * region's mapping. However, if we haven't encountered any
 56		 * misaligned runtime code regions so far, we can safely use
 57		 * non-executable permissions for non-code regions.
 58		 */
 59		code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
 60
 61		return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
 62					  : pgprot_val(PAGE_KERNEL);
 63	}
 64
 65	/* R-- */
 66	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
 67	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
 68		return pgprot_val(PAGE_KERNEL_RO);
 69
 70	/* R-X */
 71	if (attr & EFI_MEMORY_RO)
 72		return pgprot_val(PAGE_KERNEL_ROX);
 73
 74	/* RW- */
 75	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
 76	     EFI_MEMORY_XP) ||
 77	    type != EFI_RUNTIME_SERVICES_CODE)
 78		return pgprot_val(PAGE_KERNEL);
 79
 80	/* RWX */
 81	return pgprot_val(PAGE_KERNEL_EXEC);
 82}
 83
 84int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
 85{
 86	pteval_t prot_val = create_mapping_protection(md);
 87	bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
 88				   md->type == EFI_RUNTIME_SERVICES_DATA);
 89
 90	/*
 91	 * If this region is not aligned to the page size used by the OS, the
 92	 * mapping will be rounded outwards, and may end up sharing a page
 93	 * frame with an adjacent runtime memory region. Given that the page
 94	 * table descriptor covering the shared page will be rewritten when the
 95	 * adjacent region gets mapped, we must avoid block mappings here so we
 96	 * don't have to worry about splitting them when that happens.
 97	 */
 98	if (region_is_misaligned(md))
 99		page_mappings_only = true;
100
101	create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
102			   md->num_pages << EFI_PAGE_SHIFT,
103			   __pgprot(prot_val | PTE_NG), page_mappings_only);
104	return 0;
105}
106
107struct set_perm_data {
108	const efi_memory_desc_t	*md;
109	bool			has_bti;
110};
111
112static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
113{
114	struct set_perm_data *spd = data;
115	const efi_memory_desc_t *md = spd->md;
116	pte_t pte = __ptep_get(ptep);
117
118	if (md->attribute & EFI_MEMORY_RO)
119		pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
120	if (md->attribute & EFI_MEMORY_XP)
121		pte = set_pte_bit(pte, __pgprot(PTE_PXN));
122	else if (system_supports_bti_kernel() && spd->has_bti)
123		pte = set_pte_bit(pte, __pgprot(PTE_GP));
124	__set_pte(ptep, pte);
125	return 0;
126}
127
128int __init efi_set_mapping_permissions(struct mm_struct *mm,
129				       efi_memory_desc_t *md,
130				       bool has_bti)
131{
132	struct set_perm_data data = { md, has_bti };
133
134	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
135	       md->type != EFI_RUNTIME_SERVICES_DATA);
136
137	if (region_is_misaligned(md))
138		return 0;
139
140	/*
141	 * Calling apply_to_page_range() is only safe on regions that are
142	 * guaranteed to be mapped down to pages. Since we are only called
143	 * for regions that have been mapped using efi_create_mapping() above
144	 * (and this is checked by the generic Memory Attributes table parsing
145	 * routines), there is no need to check that again here.
146	 */
147	return apply_to_page_range(mm, md->virt_addr,
148				   md->num_pages << EFI_PAGE_SHIFT,
149				   set_permissions, &data);
150}
151
152/*
153 * UpdateCapsule() depends on the system being shutdown via
154 * ResetSystem().
155 */
156bool efi_poweroff_required(void)
157{
158	return efi_enabled(EFI_RUNTIME_SERVICES);
159}
160
161asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
162{
163	pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
164	return s;
165}
166
167static DEFINE_RAW_SPINLOCK(efi_rt_lock);
168
169void arch_efi_call_virt_setup(void)
170{
171	efi_virtmap_load();
172	__efi_fpsimd_begin();
173	raw_spin_lock(&efi_rt_lock);
174}
175
176void arch_efi_call_virt_teardown(void)
177{
178	raw_spin_unlock(&efi_rt_lock);
179	__efi_fpsimd_end();
180	efi_virtmap_unload();
181}
182
183asmlinkage u64 *efi_rt_stack_top __ro_after_init;
184
185asmlinkage efi_status_t __efi_rt_asm_recover(void);
186
187bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
188{
189	 /* Check whether the exception occurred while running the firmware */
190	if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
191		return false;
192
193	pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
194	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
195	clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
196
197	regs->regs[0]	= EFI_ABORTED;
198	regs->regs[30]	= efi_rt_stack_top[-1];
199	regs->pc	= (u64)__efi_rt_asm_recover;
200
201	if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
202		regs->regs[18] = efi_rt_stack_top[-2];
203
204	return true;
205}
206
207/* EFI requires 8 KiB of stack space for runtime services */
208static_assert(THREAD_SIZE >= SZ_8K);
209
210static int __init arm64_efi_rt_init(void)
211{
212	void *p;
213
214	if (!efi_enabled(EFI_RUNTIME_SERVICES))
215		return 0;
216
217	p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
218			   NUMA_NO_NODE, &&l);
219l:	if (!p) {
220		pr_warn("Failed to allocate EFI runtime stack\n");
221		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
222		return -ENOMEM;
223	}
224
225	kmemleak_not_leak(p);
226	efi_rt_stack_top = p + THREAD_SIZE;
227	return 0;
228}
229core_initcall(arm64_efi_rt_init);