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
 13#include <asm/efi.h>
 14
 15/*
 16 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
 17 * executable, everything else can be mapped with the XN bits
 18 * set. Also take the new (optional) RO/XP bits into account.
 19 */
 20static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
 21{
 22	u64 attr = md->attribute;
 23	u32 type = md->type;
 24
 25	if (type == EFI_MEMORY_MAPPED_IO)
 26		return PROT_DEVICE_nGnRE;
 27
 28	if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
 29		      "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
 30		/*
 31		 * If the region is not aligned to the page size of the OS, we
 32		 * can not use strict permissions, since that would also affect
 33		 * the mapping attributes of the adjacent regions.
 34		 */
 35		return pgprot_val(PAGE_KERNEL_EXEC);
 36
 37	/* R-- */
 38	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
 39	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
 40		return pgprot_val(PAGE_KERNEL_RO);
 41
 42	/* R-X */
 43	if (attr & EFI_MEMORY_RO)
 44		return pgprot_val(PAGE_KERNEL_ROX);
 45
 46	/* RW- */
 47	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
 48	     EFI_MEMORY_XP) ||
 49	    type != EFI_RUNTIME_SERVICES_CODE)
 50		return pgprot_val(PAGE_KERNEL);
 51
 52	/* RWX */
 53	return pgprot_val(PAGE_KERNEL_EXEC);
 54}
 55
 56/* we will fill this structure from the stub, so don't put it in .bss */
 57struct screen_info screen_info __section(.data);
 58
 59int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
 60{
 61	pteval_t prot_val = create_mapping_protection(md);
 62	bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
 63				   md->type == EFI_RUNTIME_SERVICES_DATA);
 64
 65	if (!PAGE_ALIGNED(md->phys_addr) ||
 66	    !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
 67		/*
 68		 * If the end address of this region is not aligned to page
 69		 * size, the mapping is rounded up, and may end up sharing a
 70		 * page frame with the next UEFI memory region. If we create
 71		 * a block entry now, we may need to split it again when mapping
 72		 * the next region, and support for that is going to be removed
 73		 * from the MMU routines. So avoid block mappings altogether in
 74		 * that case.
 75		 */
 76		page_mappings_only = true;
 77	}
 78
 79	create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
 80			   md->num_pages << EFI_PAGE_SHIFT,
 81			   __pgprot(prot_val | PTE_NG), page_mappings_only);
 82	return 0;
 83}
 84
 85static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
 86{
 87	efi_memory_desc_t *md = data;
 88	pte_t pte = READ_ONCE(*ptep);
 89
 90	if (md->attribute & EFI_MEMORY_RO)
 91		pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
 92	if (md->attribute & EFI_MEMORY_XP)
 93		pte = set_pte_bit(pte, __pgprot(PTE_PXN));
 94	set_pte(ptep, pte);
 95	return 0;
 96}
 97
 98int __init efi_set_mapping_permissions(struct mm_struct *mm,
 99				       efi_memory_desc_t *md)
100{
101	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
102	       md->type != EFI_RUNTIME_SERVICES_DATA);
103
104	/*
105	 * Calling apply_to_page_range() is only safe on regions that are
106	 * guaranteed to be mapped down to pages. Since we are only called
107	 * for regions that have been mapped using efi_create_mapping() above
108	 * (and this is checked by the generic Memory Attributes table parsing
109	 * routines), there is no need to check that again here.
110	 */
111	return apply_to_page_range(mm, md->virt_addr,
112				   md->num_pages << EFI_PAGE_SHIFT,
113				   set_permissions, md);
114}
115
116/*
117 * UpdateCapsule() depends on the system being shutdown via
118 * ResetSystem().
119 */
120bool efi_poweroff_required(void)
121{
122	return efi_enabled(EFI_RUNTIME_SERVICES);
123}
124
125asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
126{
127	pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
128	return s;
129}