LXR linux/arch/powerpc/mm/highmem.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * highmem.c: virtual kernel memory mappings for high memory
   4 *
   5 * PowerPC version, stolen from the i386 version.
   6 *
   7 * Used in CONFIG_HIGHMEM systems for memory pages which
   8 * are not addressable by direct kernel virtual addresses.
   9 *
  10 * Copyright (C) 1999 Gerhard Wichert, Siemens AG
  11 *                    Gerhard.Wichert@pdb.siemens.de
  12 *
  13 *
  14 * Redesigned the x86 32-bit VM architecture to deal with
  15 * up to 16 Terrabyte physical memory. With current x86 CPUs
  16 * we now support up to 64 Gigabytes physical RAM.
  17 *
  18 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
  19 *
  20 * Reworked for PowerPC by various contributors. Moved from
  21 * highmem.h by Benjamin Herrenschmidt (c) 2009 IBM Corp.
  22 */
  23
  24#include <linux/highmem.h>
  25#include <linux/module.h>
  26
  27/*
  28 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  29 * gives a more generic (and caching) interface. But kmap_atomic can
  30 * be used in IRQ contexts, so in some (very limited) cases we need
  31 * it.
  32 */
  33void *kmap_atomic_prot(struct page *page, pgprot_t prot)
  34{
  35        unsigned long vaddr;
  36        int idx, type;
  37
  38        preempt_disable();
  39        pagefault_disable();
  40        if (!PageHighMem(page))
  41                return page_address(page);
  42
  43        type = kmap_atomic_idx_push();
  44        idx = type + KM_TYPE_NR*smp_processor_id();
  45        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  46#ifdef CONFIG_DEBUG_HIGHMEM
  47        BUG_ON(!pte_none(*(kmap_pte-idx)));
  48#endif
  49        __set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot), 1);
  50        local_flush_tlb_page(NULL, vaddr);
  51
  52        return (void*) vaddr;
  53}
  54EXPORT_SYMBOL(kmap_atomic_prot);
  55
  56void __kunmap_atomic(void *kvaddr)
  57{
  58        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  59        int type __maybe_unused;
  60
  61        if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
  62                pagefault_enable();
  63                preempt_enable();
  64                return;
  65        }
  66
  67        type = kmap_atomic_idx();
  68
  69#ifdef CONFIG_DEBUG_HIGHMEM
  70        {
  71                unsigned int idx;
  72
  73                idx = type + KM_TYPE_NR * smp_processor_id();
  74                BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
  75
  76                /*
  77                 * force other mappings to Oops if they'll try to access
  78                 * this pte without first remap it
  79                 */
  80                pte_clear(&init_mm, vaddr, kmap_pte-idx);
  81                local_flush_tlb_page(NULL, vaddr);
  82        }
  83#endif
  84
  85        kmap_atomic_idx_pop();
  86        pagefault_enable();
  87        preempt_enable();
  88}
  89EXPORT_SYMBOL(__kunmap_atomic);
  90