cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

efi.c (2513B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Copyright (C) 2020 Western Digital Corporation or its affiliates.
      4 * Adapted from arch/arm64/kernel/efi.c
      5 */
      6
      7#include <linux/efi.h>
      8#include <linux/init.h>
      9
     10#include <asm/efi.h>
     11#include <asm/pgtable.h>
     12#include <asm/pgtable-bits.h>
     13
     14/*
     15 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
     16 * executable, everything else can be mapped with the XN bits
     17 * set. Also take the new (optional) RO/XP bits into account.
     18 */
     19static __init pgprot_t efimem_to_pgprot_map(efi_memory_desc_t *md)
     20{
     21	u64 attr = md->attribute;
     22	u32 type = md->type;
     23
     24	if (type == EFI_MEMORY_MAPPED_IO)
     25		return PAGE_KERNEL;
     26
     27	/* R-- */
     28	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
     29	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
     30		return PAGE_KERNEL_READ;
     31
     32	/* R-X */
     33	if (attr & EFI_MEMORY_RO)
     34		return PAGE_KERNEL_READ_EXEC;
     35
     36	/* RW- */
     37	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
     38	     EFI_MEMORY_XP) ||
     39	    type != EFI_RUNTIME_SERVICES_CODE)
     40		return PAGE_KERNEL;
     41
     42	/* RWX */
     43	return PAGE_KERNEL_EXEC;
     44}
     45
     46int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
     47{
     48	pgprot_t prot = __pgprot(pgprot_val(efimem_to_pgprot_map(md)) &
     49				~(_PAGE_GLOBAL));
     50	int i;
     51
     52	/* RISC-V maps one page at a time */
     53	for (i = 0; i < md->num_pages; i++)
     54		create_pgd_mapping(mm->pgd, md->virt_addr + i * PAGE_SIZE,
     55				   md->phys_addr + i * PAGE_SIZE,
     56				   PAGE_SIZE, prot);
     57	return 0;
     58}
     59
     60static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
     61{
     62	efi_memory_desc_t *md = data;
     63	pte_t pte = READ_ONCE(*ptep);
     64	unsigned long val;
     65
     66	if (md->attribute & EFI_MEMORY_RO) {
     67		val = pte_val(pte) & ~_PAGE_WRITE;
     68		val |= _PAGE_READ;
     69		pte = __pte(val);
     70	}
     71	if (md->attribute & EFI_MEMORY_XP) {
     72		val = pte_val(pte) & ~_PAGE_EXEC;
     73		pte = __pte(val);
     74	}
     75	set_pte(ptep, pte);
     76
     77	return 0;
     78}
     79
     80int __init efi_set_mapping_permissions(struct mm_struct *mm,
     81				       efi_memory_desc_t *md)
     82{
     83	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
     84	       md->type != EFI_RUNTIME_SERVICES_DATA);
     85
     86	/*
     87	 * Calling apply_to_page_range() is only safe on regions that are
     88	 * guaranteed to be mapped down to pages. Since we are only called
     89	 * for regions that have been mapped using efi_create_mapping() above
     90	 * (and this is checked by the generic Memory Attributes table parsing
     91	 * routines), there is no need to check that again here.
     92	 */
     93	return apply_to_page_range(mm, md->virt_addr,
     94				   md->num_pages << EFI_PAGE_SHIFT,
     95				   set_permissions, md);
     96}