1/*
  2 * Extensible Firmware Interface
  3 *
  4 * Based on Extensible Firmware Interface Specification version 2.4
  5 *
  6 * Copyright (C) 2013, 2014 Linaro Ltd.
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License version 2 as
 10 * published by the Free Software Foundation.
 11 *
 12 */
 13
 14#include <linux/efi.h>
 15#include <linux/init.h>
 16
 17#include <asm/efi.h>
 18
 19/*
 20 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
 21 * executable, everything else can be mapped with the XN bits
 22 * set. Also take the new (optional) RO/XP bits into account.
 23 */
 24static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
 25{
 26	u64 attr = md->attribute;
 27	u32 type = md->type;
 28
 29	if (type == EFI_MEMORY_MAPPED_IO)
 30		return PROT_DEVICE_nGnRE;
 31
 32	if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
 33		      "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
 34		/*
 35		 * If the region is not aligned to the page size of the OS, we
 36		 * can not use strict permissions, since that would also affect
 37		 * the mapping attributes of the adjacent regions.
 38		 */
 39		return pgprot_val(PAGE_KERNEL_EXEC);
 40
 41	/* R-- */
 42	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
 43	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
 44		return pgprot_val(PAGE_KERNEL_RO);
 45
 46	/* R-X */
 47	if (attr & EFI_MEMORY_RO)
 48		return pgprot_val(PAGE_KERNEL_ROX);
 49
 50	/* RW- */
 51	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
 52	     EFI_MEMORY_XP) ||
 53	    type != EFI_RUNTIME_SERVICES_CODE)
 54		return pgprot_val(PAGE_KERNEL);
 55
 56	/* RWX */
 57	return pgprot_val(PAGE_KERNEL_EXEC);
 58}
 59
 60/* we will fill this structure from the stub, so don't put it in .bss */
 61struct screen_info screen_info __section(.data);
 62
 63int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
 64{
 65	pteval_t prot_val = create_mapping_protection(md);
 66	bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
 67				   md->type == EFI_RUNTIME_SERVICES_DATA);
 68
 69	if (!PAGE_ALIGNED(md->phys_addr) ||
 70	    !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
 71		/*
 72		 * If the end address of this region is not aligned to page
 73		 * size, the mapping is rounded up, and may end up sharing a
 74		 * page frame with the next UEFI memory region. If we create
 75		 * a block entry now, we may need to split it again when mapping
 76		 * the next region, and support for that is going to be removed
 77		 * from the MMU routines. So avoid block mappings altogether in
 78		 * that case.
 79		 */
 80		page_mappings_only = true;
 81	}
 82
 83	create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
 84			   md->num_pages << EFI_PAGE_SHIFT,
 85			   __pgprot(prot_val | PTE_NG), page_mappings_only);
 86	return 0;
 87}
 88
 89static int __init set_permissions(pte_t *ptep, pgtable_t token,
 90				  unsigned long addr, void *data)
 91{
 92	efi_memory_desc_t *md = data;
 93	pte_t pte = READ_ONCE(*ptep);
 94
 95	if (md->attribute & EFI_MEMORY_RO)
 96		pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
 97	if (md->attribute & EFI_MEMORY_XP)
 98		pte = set_pte_bit(pte, __pgprot(PTE_PXN));
 99	set_pte(ptep, pte);
100	return 0;
101}
102
103int __init efi_set_mapping_permissions(struct mm_struct *mm,
104				       efi_memory_desc_t *md)
105{
106	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
107	       md->type != EFI_RUNTIME_SERVICES_DATA);
108
109	/*
110	 * Calling apply_to_page_range() is only safe on regions that are
111	 * guaranteed to be mapped down to pages. Since we are only called
112	 * for regions that have been mapped using efi_create_mapping() above
113	 * (and this is checked by the generic Memory Attributes table parsing
114	 * routines), there is no need to check that again here.
115	 */
116	return apply_to_page_range(mm, md->virt_addr,
117				   md->num_pages << EFI_PAGE_SHIFT,
118				   set_permissions, md);
119}
120
121/*
122 * UpdateCapsule() depends on the system being shutdown via
123 * ResetSystem().
124 */
125bool efi_poweroff_required(void)
126{
127	return efi_enabled(EFI_RUNTIME_SERVICES);
128}
129
130asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
131{
132	pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
133	return s;
134}