memattr.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.org>
  4 */
  5
  6#define pr_fmt(fmt)	"efi: memattr: " fmt
  7
  8#include <linux/efi.h>
  9#include <linux/init.h>
 10#include <linux/io.h>
 11#include <linux/memblock.h>
 12
 13#include <asm/early_ioremap.h>
 14
 15static int __initdata tbl_size;
 16unsigned long __ro_after_init efi_mem_attr_table = EFI_INVALID_TABLE_ADDR;
 17
 18/*
 19 * Reserve the memory associated with the Memory Attributes configuration
 20 * table, if it exists.
 21 */
 22void __init efi_memattr_init(void)
 23{
 24	efi_memory_attributes_table_t *tbl;
 25	unsigned long size;
 26
 27	if (efi_mem_attr_table == EFI_INVALID_TABLE_ADDR)
 28		return;
 29
 30	tbl = early_memremap(efi_mem_attr_table, sizeof(*tbl));
 31	if (!tbl) {
 32		pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
 33		       efi_mem_attr_table);
 34		return;
 35	}
 36
 37	if (tbl->version > 2) {
 38		pr_warn("Unexpected EFI Memory Attributes table version %d\n",
 39			tbl->version);
 40		goto unmap;
 41	}
 42
 43
 44	/*
 45	 * Sanity check: the Memory Attributes Table contains up to 3 entries
 46	 * for each entry of type EfiRuntimeServicesCode in the EFI memory map.
 47	 * So if the size of the table exceeds 3x the size of the entire EFI
 48	 * memory map, there is clearly something wrong, and the table should
 49	 * just be ignored altogether.
 50	 */
 51	size = tbl->num_entries * tbl->desc_size;
 52	if (size > 3 * efi.memmap.nr_map * efi.memmap.desc_size) {
 53		pr_warn(FW_BUG "Corrupted EFI Memory Attributes Table detected! (version == %u, desc_size == %u, num_entries == %u)\n",
 54			tbl->version, tbl->desc_size, tbl->num_entries);
 55		goto unmap;
 56	}
 57
 58	tbl_size = sizeof(*tbl) + size;
 59	memblock_reserve(efi_mem_attr_table, tbl_size);
 60	set_bit(EFI_MEM_ATTR, &efi.flags);
 61
 62unmap:
 63	early_memunmap(tbl, sizeof(*tbl));
 64}
 65
 66/*
 67 * Returns a copy @out of the UEFI memory descriptor @in if it is covered
 68 * entirely by a UEFI memory map entry with matching attributes. The virtual
 69 * address of @out is set according to the matching entry that was found.
 70 */
 71static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out)
 72{
 73	u64 in_paddr = in->phys_addr;
 74	u64 in_size = in->num_pages << EFI_PAGE_SHIFT;
 75	efi_memory_desc_t *md;
 76
 77	*out = *in;
 78
 79	if (in->type != EFI_RUNTIME_SERVICES_CODE &&
 80	    in->type != EFI_RUNTIME_SERVICES_DATA) {
 81		pr_warn("Entry type should be RuntimeServiceCode/Data\n");
 82		return false;
 83	}
 84
 85	if (PAGE_SIZE > EFI_PAGE_SIZE &&
 86	    (!PAGE_ALIGNED(in->phys_addr) ||
 87	     !PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {
 88		/*
 89		 * Since arm64 may execute with page sizes of up to 64 KB, the
 90		 * UEFI spec mandates that RuntimeServices memory regions must
 91		 * be 64 KB aligned. We need to validate this here since we will
 92		 * not be able to tighten permissions on such regions without
 93		 * affecting adjacent regions.
 94		 */
 95		pr_warn("Entry address region misaligned\n");
 96		return false;
 97	}
 98
 99	for_each_efi_memory_desc(md) {
100		u64 md_paddr = md->phys_addr;
101		u64 md_size = md->num_pages << EFI_PAGE_SHIFT;
102
103		if (!(md->attribute & EFI_MEMORY_RUNTIME))
104			continue;
105		if (md->virt_addr == 0 && md->phys_addr != 0) {
106			/* no virtual mapping has been installed by the stub */
107			break;
108		}
109
110		if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)
111			continue;
112
113		/*
114		 * This entry covers the start of @in, check whether
115		 * it covers the end as well.
116		 */
117		if (md_paddr + md_size < in_paddr + in_size) {
118			pr_warn("Entry covers multiple EFI memory map regions\n");
119			return false;
120		}
121
122		if (md->type != in->type) {
123			pr_warn("Entry type deviates from EFI memory map region type\n");
124			return false;
125		}
126
127		out->virt_addr = in_paddr + (md->virt_addr - md_paddr);
128
129		return true;
130	}
131
132	pr_warn("No matching entry found in the EFI memory map\n");
133	return false;
134}
135
136/*
137 * To be called after the EFI page tables have been populated. If a memory
138 * attributes table is available, its contents will be used to update the
139 * mappings with tightened permissions as described by the table.
140 * This requires the UEFI memory map to have already been populated with
141 * virtual addresses.
142 */
143int __init efi_memattr_apply_permissions(struct mm_struct *mm,
144					 efi_memattr_perm_setter fn)
145{
146	efi_memory_attributes_table_t *tbl;
147	bool has_bti = false;
148	int i, ret;
149
150	if (tbl_size <= sizeof(*tbl))
151		return 0;
152
153	/*
154	 * We need the EFI memory map to be setup so we can use it to
155	 * lookup the virtual addresses of all entries in the  of EFI
156	 * Memory Attributes table. If it isn't available, this
157	 * function should not be called.
158	 */
159	if (WARN_ON(!efi_enabled(EFI_MEMMAP)))
160		return 0;
161
162	tbl = memremap(efi_mem_attr_table, tbl_size, MEMREMAP_WB);
163	if (!tbl) {
164		pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
165		       efi_mem_attr_table);
166		return -ENOMEM;
167	}
168
169	if (tbl->version > 1 &&
170	    (tbl->flags & EFI_MEMORY_ATTRIBUTES_FLAGS_RT_FORWARD_CONTROL_FLOW_GUARD))
171		has_bti = true;
172
173	if (efi_enabled(EFI_DBG))
174		pr_info("Processing EFI Memory Attributes table:\n");
175
176	for (i = ret = 0; ret == 0 && i < tbl->num_entries; i++) {
177		efi_memory_desc_t md;
178		unsigned long size;
179		bool valid;
180		char buf[64];
181
182		valid = entry_is_valid(efi_memdesc_ptr(tbl->entry, tbl->desc_size, i),
183				       &md);
184		size = md.num_pages << EFI_PAGE_SHIFT;
185		if (efi_enabled(EFI_DBG) || !valid)
186			pr_info("%s 0x%012llx-0x%012llx %s\n",
187				valid ? "" : "!", md.phys_addr,
188				md.phys_addr + size - 1,
189				efi_md_typeattr_format(buf, sizeof(buf), &md));
190
191		if (valid) {
192			ret = fn(mm, &md, has_bti);
193			if (ret)
194				pr_err("Error updating mappings, skipping subsequent md's\n");
195		}
196	}
197	memunmap(tbl);
198	return ret;
199}