![Sai Praneeth](/assets/img/avatar_default.png)
UEFI v2.6 introduces EFI_MEMORY_ATTRIBUTES_TABLE which describes memory protections that may be applied to the EFI Runtime code and data regions by the kernel. This enables the kernel to map these regions more strictly thereby increasing security. Presently, the only valid bits for the attribute field of a memory descriptor are EFI_MEMORY_RO and EFI_MEMORY_XP, hence use these bits to update the mappings in efi_pgd. The UEFI specification recommends to use this feature instead of EFI_PROPERTIES_TABLE and hence while updating EFI mappings we first check for EFI_MEMORY_ATTRIBUTES_TABLE and if it's present we update the mappings according to this table and hence disregarding EFI_PROPERTIES_TABLE even if it's published by the firmware. We consider EFI_PROPERTIES_TABLE only when EFI_MEMORY_ATTRIBUTES_TABLE is absent. Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Lee, Chun-Yi <jlee@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Shankar <ravi.v.shankar@intel.com> Cc: Ricardo Neri <ricardo.neri@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1485868902-20401-6-git-send-email-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
187 lines
4.9 KiB
C
187 lines
4.9 KiB
C
/*
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* Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#define pr_fmt(fmt) "efi: memattr: " fmt
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#include <linux/efi.h>
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#include <linux/init.h>
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#include <linux/io.h>
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#include <linux/memblock.h>
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#include <asm/early_ioremap.h>
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static int __initdata tbl_size;
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/*
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* Reserve the memory associated with the Memory Attributes configuration
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* table, if it exists.
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*/
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int __init efi_memattr_init(void)
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{
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efi_memory_attributes_table_t *tbl;
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if (efi.mem_attr_table == EFI_INVALID_TABLE_ADDR)
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return 0;
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tbl = early_memremap(efi.mem_attr_table, sizeof(*tbl));
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if (!tbl) {
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pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
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efi.mem_attr_table);
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return -ENOMEM;
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}
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if (tbl->version > 1) {
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pr_warn("Unexpected EFI Memory Attributes table version %d\n",
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tbl->version);
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goto unmap;
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}
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tbl_size = sizeof(*tbl) + tbl->num_entries * tbl->desc_size;
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memblock_reserve(efi.mem_attr_table, tbl_size);
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set_bit(EFI_MEM_ATTR, &efi.flags);
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unmap:
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early_memunmap(tbl, sizeof(*tbl));
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return 0;
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}
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/*
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* Returns a copy @out of the UEFI memory descriptor @in if it is covered
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* entirely by a UEFI memory map entry with matching attributes. The virtual
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* address of @out is set according to the matching entry that was found.
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*/
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static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out)
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{
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u64 in_paddr = in->phys_addr;
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u64 in_size = in->num_pages << EFI_PAGE_SHIFT;
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efi_memory_desc_t *md;
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*out = *in;
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if (in->type != EFI_RUNTIME_SERVICES_CODE &&
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in->type != EFI_RUNTIME_SERVICES_DATA) {
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pr_warn("Entry type should be RuntimeServiceCode/Data\n");
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return false;
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}
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if (!(in->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))) {
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pr_warn("Entry attributes invalid: RO and XP bits both cleared\n");
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return false;
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}
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if (PAGE_SIZE > EFI_PAGE_SIZE &&
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(!PAGE_ALIGNED(in->phys_addr) ||
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!PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {
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/*
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* Since arm64 may execute with page sizes of up to 64 KB, the
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* UEFI spec mandates that RuntimeServices memory regions must
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* be 64 KB aligned. We need to validate this here since we will
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* not be able to tighten permissions on such regions without
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* affecting adjacent regions.
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*/
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pr_warn("Entry address region misaligned\n");
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return false;
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}
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for_each_efi_memory_desc(md) {
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u64 md_paddr = md->phys_addr;
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u64 md_size = md->num_pages << EFI_PAGE_SHIFT;
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if (!(md->attribute & EFI_MEMORY_RUNTIME))
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continue;
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if (md->virt_addr == 0) {
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/* no virtual mapping has been installed by the stub */
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break;
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}
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if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)
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continue;
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/*
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* This entry covers the start of @in, check whether
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* it covers the end as well.
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*/
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if (md_paddr + md_size < in_paddr + in_size) {
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pr_warn("Entry covers multiple EFI memory map regions\n");
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return false;
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}
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if (md->type != in->type) {
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pr_warn("Entry type deviates from EFI memory map region type\n");
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return false;
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}
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out->virt_addr = in_paddr + (md->virt_addr - md_paddr);
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return true;
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}
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pr_warn("No matching entry found in the EFI memory map\n");
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return false;
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}
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/*
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* To be called after the EFI page tables have been populated. If a memory
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* attributes table is available, its contents will be used to update the
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* mappings with tightened permissions as described by the table.
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* This requires the UEFI memory map to have already been populated with
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* virtual addresses.
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*/
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int __init efi_memattr_apply_permissions(struct mm_struct *mm,
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efi_memattr_perm_setter fn)
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{
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efi_memory_attributes_table_t *tbl;
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int i, ret;
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if (tbl_size <= sizeof(*tbl))
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return 0;
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/*
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* We need the EFI memory map to be setup so we can use it to
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* lookup the virtual addresses of all entries in the of EFI
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* Memory Attributes table. If it isn't available, this
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* function should not be called.
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*/
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if (WARN_ON(!efi_enabled(EFI_MEMMAP)))
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return 0;
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tbl = memremap(efi.mem_attr_table, tbl_size, MEMREMAP_WB);
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if (!tbl) {
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pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
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efi.mem_attr_table);
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return -ENOMEM;
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}
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if (efi_enabled(EFI_DBG))
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pr_info("Processing EFI Memory Attributes table:\n");
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for (i = ret = 0; ret == 0 && i < tbl->num_entries; i++) {
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efi_memory_desc_t md;
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unsigned long size;
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bool valid;
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char buf[64];
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valid = entry_is_valid((void *)tbl->entry + i * tbl->desc_size,
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&md);
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size = md.num_pages << EFI_PAGE_SHIFT;
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if (efi_enabled(EFI_DBG) || !valid)
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pr_info("%s 0x%012llx-0x%012llx %s\n",
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valid ? "" : "!", md.phys_addr,
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md.phys_addr + size - 1,
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efi_md_typeattr_format(buf, sizeof(buf), &md));
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if (valid) {
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ret = fn(mm, &md);
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if (ret)
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pr_err("Error updating mappings, skipping subsequent md's\n");
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}
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}
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memunmap(tbl);
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return ret;
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}
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