127 lines
3.7 KiB
C
127 lines
3.7 KiB
C
/*
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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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* 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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*/
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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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/*
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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 (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
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"UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
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/*
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* If the region is not aligned to the page size of the OS, we
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* can not use strict permissions, since that would also affect
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* the mapping attributes of the adjacent regions.
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*/
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return pgprot_val(PAGE_KERNEL_EXEC);
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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_XP || 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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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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if (!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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* If the end address of this region is not aligned to page
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* size, the mapping is rounded up, and may end up sharing a
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* page frame with the next UEFI memory region. If we create
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* a block entry now, we may need to split it again when mapping
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* the next region, and support for that is going to be removed
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* from the MMU routines. So avoid block mappings altogether in
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* that case.
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*/
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page_mappings_only = true;
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}
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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, pgtable_t token,
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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 = *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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/*
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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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