147 lines
4.2 KiB
C
147 lines
4.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Extensible Firmware Interface
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*
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* Based on Extensible Firmware Interface Specification version 2.4
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*
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* Copyright (C) 2013, 2014 Linaro Ltd.
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*/
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#include <linux/efi.h>
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#include <linux/init.h>
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#include <asm/efi.h>
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static bool region_is_misaligned(const efi_memory_desc_t *md)
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{
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if (PAGE_SIZE == EFI_PAGE_SIZE)
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return false;
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return !PAGE_ALIGNED(md->phys_addr) ||
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!PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
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}
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/*
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* Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
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* executable, everything else can be mapped with the XN bits
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* set. Also take the new (optional) RO/XP bits into account.
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*/
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static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
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{
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u64 attr = md->attribute;
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u32 type = md->type;
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if (type == EFI_MEMORY_MAPPED_IO)
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return PROT_DEVICE_nGnRE;
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if (region_is_misaligned(md)) {
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static bool __initdata code_is_misaligned;
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/*
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* Regions that are not aligned to the OS page size cannot be
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* mapped with strict permissions, as those might interfere
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* with the permissions that are needed by the adjacent
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* region's mapping. However, if we haven't encountered any
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* misaligned runtime code regions so far, we can safely use
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* non-executable permissions for non-code regions.
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*/
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code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);
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return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
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: pgprot_val(PAGE_KERNEL);
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}
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/* R-- */
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if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
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(EFI_MEMORY_XP | EFI_MEMORY_RO))
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return pgprot_val(PAGE_KERNEL_RO);
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/* R-X */
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if (attr & EFI_MEMORY_RO)
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return pgprot_val(PAGE_KERNEL_ROX);
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/* RW- */
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if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
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EFI_MEMORY_XP) ||
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type != EFI_RUNTIME_SERVICES_CODE)
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return pgprot_val(PAGE_KERNEL);
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/* RWX */
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return pgprot_val(PAGE_KERNEL_EXEC);
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}
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/* we will fill this structure from the stub, so don't put it in .bss */
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struct screen_info screen_info __section(".data");
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EXPORT_SYMBOL(screen_info);
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int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
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{
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pteval_t prot_val = create_mapping_protection(md);
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bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
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md->type == EFI_RUNTIME_SERVICES_DATA);
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/*
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* If this region is not aligned to the page size used by the OS, the
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* mapping will be rounded outwards, and may end up sharing a page
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* frame with an adjacent runtime memory region. Given that the page
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* table descriptor covering the shared page will be rewritten when the
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* adjacent region gets mapped, we must avoid block mappings here so we
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* don't have to worry about splitting them when that happens.
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*/
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if (region_is_misaligned(md))
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page_mappings_only = true;
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create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
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md->num_pages << EFI_PAGE_SHIFT,
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__pgprot(prot_val | PTE_NG), page_mappings_only);
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return 0;
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}
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static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
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{
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efi_memory_desc_t *md = data;
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pte_t pte = READ_ONCE(*ptep);
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if (md->attribute & EFI_MEMORY_RO)
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pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
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if (md->attribute & EFI_MEMORY_XP)
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pte = set_pte_bit(pte, __pgprot(PTE_PXN));
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set_pte(ptep, pte);
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return 0;
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}
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int __init efi_set_mapping_permissions(struct mm_struct *mm,
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efi_memory_desc_t *md)
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{
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BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
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md->type != EFI_RUNTIME_SERVICES_DATA);
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if (region_is_misaligned(md))
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return 0;
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/*
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* Calling apply_to_page_range() is only safe on regions that are
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* guaranteed to be mapped down to pages. Since we are only called
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* for regions that have been mapped using efi_create_mapping() above
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* (and this is checked by the generic Memory Attributes table parsing
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* routines), there is no need to check that again here.
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*/
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return apply_to_page_range(mm, md->virt_addr,
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md->num_pages << EFI_PAGE_SHIFT,
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set_permissions, md);
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}
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/*
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* UpdateCapsule() depends on the system being shutdown via
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* ResetSystem().
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*/
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bool efi_poweroff_required(void)
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{
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return efi_enabled(EFI_RUNTIME_SERVICES);
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}
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asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
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{
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pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
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return s;
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}
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