cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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efi.c (3878B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Extensible Firmware Interface
      4 *
      5 * Based on Extensible Firmware Interface Specification version 2.4
      6 *
      7 * Copyright (C) 2013, 2014 Linaro Ltd.
      8 */
      9
     10#include <linux/efi.h>
     11#include <linux/init.h>
     12
     13#include <asm/efi.h>
     14
     15/*
     16 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
     17 * executable, everything else can be mapped with the XN bits
     18 * set. Also take the new (optional) RO/XP bits into account.
     19 */
     20static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
     21{
     22	u64 attr = md->attribute;
     23	u32 type = md->type;
     24
     25	if (type == EFI_MEMORY_MAPPED_IO)
     26		return PROT_DEVICE_nGnRE;
     27
     28	if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
     29		      "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
     30		/*
     31		 * If the region is not aligned to the page size of the OS, we
     32		 * can not use strict permissions, since that would also affect
     33		 * the mapping attributes of the adjacent regions.
     34		 */
     35		return pgprot_val(PAGE_KERNEL_EXEC);
     36
     37	/* R-- */
     38	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
     39	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
     40		return pgprot_val(PAGE_KERNEL_RO);
     41
     42	/* R-X */
     43	if (attr & EFI_MEMORY_RO)
     44		return pgprot_val(PAGE_KERNEL_ROX);
     45
     46	/* RW- */
     47	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
     48	     EFI_MEMORY_XP) ||
     49	    type != EFI_RUNTIME_SERVICES_CODE)
     50		return pgprot_val(PAGE_KERNEL);
     51
     52	/* RWX */
     53	return pgprot_val(PAGE_KERNEL_EXEC);
     54}
     55
     56/* we will fill this structure from the stub, so don't put it in .bss */
     57struct screen_info screen_info __section(".data");
     58EXPORT_SYMBOL(screen_info);
     59
     60int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
     61{
     62	pteval_t prot_val = create_mapping_protection(md);
     63	bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
     64				   md->type == EFI_RUNTIME_SERVICES_DATA);
     65
     66	if (!PAGE_ALIGNED(md->phys_addr) ||
     67	    !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
     68		/*
     69		 * If the end address of this region is not aligned to page
     70		 * size, the mapping is rounded up, and may end up sharing a
     71		 * page frame with the next UEFI memory region. If we create
     72		 * a block entry now, we may need to split it again when mapping
     73		 * the next region, and support for that is going to be removed
     74		 * from the MMU routines. So avoid block mappings altogether in
     75		 * that case.
     76		 */
     77		page_mappings_only = true;
     78	}
     79
     80	create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
     81			   md->num_pages << EFI_PAGE_SHIFT,
     82			   __pgprot(prot_val | PTE_NG), page_mappings_only);
     83	return 0;
     84}
     85
     86static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
     87{
     88	efi_memory_desc_t *md = data;
     89	pte_t pte = READ_ONCE(*ptep);
     90
     91	if (md->attribute & EFI_MEMORY_RO)
     92		pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
     93	if (md->attribute & EFI_MEMORY_XP)
     94		pte = set_pte_bit(pte, __pgprot(PTE_PXN));
     95	set_pte(ptep, pte);
     96	return 0;
     97}
     98
     99int __init efi_set_mapping_permissions(struct mm_struct *mm,
    100				       efi_memory_desc_t *md)
    101{
    102	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
    103	       md->type != EFI_RUNTIME_SERVICES_DATA);
    104
    105	/*
    106	 * Calling apply_to_page_range() is only safe on regions that are
    107	 * guaranteed to be mapped down to pages. Since we are only called
    108	 * for regions that have been mapped using efi_create_mapping() above
    109	 * (and this is checked by the generic Memory Attributes table parsing
    110	 * routines), there is no need to check that again here.
    111	 */
    112	return apply_to_page_range(mm, md->virt_addr,
    113				   md->num_pages << EFI_PAGE_SHIFT,
    114				   set_permissions, md);
    115}
    116
    117/*
    118 * UpdateCapsule() depends on the system being shutdown via
    119 * ResetSystem().
    120 */
    121bool efi_poweroff_required(void)
    122{
    123	return efi_enabled(EFI_RUNTIME_SERVICES);
    124}
    125
    126asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
    127{
    128	pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
    129	return s;
    130}