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

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  highmem.c: virtual kernel memory mappings for high memory
   4 *
   5 *  Provides kernel-static versions of atomic kmap functions originally
   6 *  found as inlines in include/asm-sparc/highmem.h.  These became
   7 *  needed as kmap_atomic() and kunmap_atomic() started getting
   8 *  called from within modules.
   9 *  -- Tomas Szepe <szepe@pinerecords.com>, September 2002
  10 *
  11 *  But kmap_atomic() and kunmap_atomic() cannot be inlined in
  12 *  modules because they are loaded with btfixup-ped functions.
  13 */
  14
  15/*
  16 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  17 * gives a more generic (and caching) interface. But kmap_atomic can
  18 * be used in IRQ contexts, so in some (very limited) cases we need it.
  19 *
  20 * XXX This is an old text. Actually, it's good to use atomic kmaps,
  21 * provided you remember that they are atomic and not try to sleep
  22 * with a kmap taken, much like a spinlock. Non-atomic kmaps are
  23 * shared by CPUs, and so precious, and establishing them requires IPI.
  24 * Atomic kmaps are lightweight and we may have NCPUS more of them.
  25 */
  26#include <linux/highmem.h>
  27#include <linux/export.h>
  28#include <linux/mm.h>
  29
  30#include <asm/cacheflush.h>
  31#include <asm/tlbflush.h>
  32#include <asm/pgalloc.h>
  33#include <asm/vaddrs.h>
  34
  35pgprot_t kmap_prot;
  36
  37static pte_t *kmap_pte;
  38
  39void __init kmap_init(void)
  40{
  41        unsigned long address;
  42        pmd_t *dir;
  43
  44        address = __fix_to_virt(FIX_KMAP_BEGIN);
  45        dir = pmd_offset(pgd_offset_k(address), address);
  46
  47        /* cache the first kmap pte */
  48        kmap_pte = pte_offset_kernel(dir, address);
  49        kmap_prot = __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE);
  50}
  51
  52void *kmap_atomic(struct page *page)
  53{
  54        unsigned long vaddr;
  55        long idx, type;
  56
  57        preempt_disable();
  58        pagefault_disable();
  59        if (!PageHighMem(page))
  60                return page_address(page);
  61
  62        type = kmap_atomic_idx_push();
  63        idx = type + KM_TYPE_NR*smp_processor_id();
  64        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  65
  66/* XXX Fix - Anton */
  67#if 0
  68        __flush_cache_one(vaddr);
  69#else
  70        flush_cache_all();
  71#endif
  72
  73#ifdef CONFIG_DEBUG_HIGHMEM
  74        BUG_ON(!pte_none(*(kmap_pte-idx)));
  75#endif
  76        set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  77/* XXX Fix - Anton */
  78#if 0
  79        __flush_tlb_one(vaddr);
  80#else
  81        flush_tlb_all();
  82#endif
  83
  84        return (void*) vaddr;
  85}
  86EXPORT_SYMBOL(kmap_atomic);
  87
  88void __kunmap_atomic(void *kvaddr)
  89{
  90        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  91        int type;
  92
  93        if (vaddr < FIXADDR_START) { // FIXME
  94                pagefault_enable();
  95                preempt_enable();
  96                return;
  97        }
  98
  99        type = kmap_atomic_idx();
 100
 101#ifdef CONFIG_DEBUG_HIGHMEM
 102        {
 103                unsigned long idx;
 104
 105                idx = type + KM_TYPE_NR * smp_processor_id();
 106                BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 107
 108                /* XXX Fix - Anton */
 109#if 0
 110                __flush_cache_one(vaddr);
 111#else
 112                flush_cache_all();
 113#endif
 114
 115                /*
 116                 * force other mappings to Oops if they'll try to access
 117                 * this pte without first remap it
 118                 */
 119                pte_clear(&init_mm, vaddr, kmap_pte-idx);
 120                /* XXX Fix - Anton */
 121#if 0
 122                __flush_tlb_one(vaddr);
 123#else
 124                flush_tlb_all();
 125#endif
 126        }
 127#endif
 128
 129        kmap_atomic_idx_pop();
 130        pagefault_enable();
 131        preempt_enable();
 132}
 133EXPORT_SYMBOL(__kunmap_atomic);
 134