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/vaddrs.h>
 33
 34static pte_t *kmap_pte;
 35
 36void __init kmap_init(void)
 37{
 38	unsigned long address = __fix_to_virt(FIX_KMAP_BEGIN);
 39
 40        /* cache the first kmap pte */
 41        kmap_pte = virt_to_kpte(address);
 42}
 43
 44void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
 45{
 46	unsigned long vaddr;
 47	long idx, type;
 48
 49	type = kmap_atomic_idx_push();
 50	idx = type + KM_TYPE_NR*smp_processor_id();
 51	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 52
 53/* XXX Fix - Anton */
 54#if 0
 55	__flush_cache_one(vaddr);
 56#else
 57	flush_cache_all();
 58#endif
 59
 60#ifdef CONFIG_DEBUG_HIGHMEM
 61	BUG_ON(!pte_none(*(kmap_pte-idx)));
 62#endif
 63	set_pte(kmap_pte-idx, mk_pte(page, prot));
 64/* XXX Fix - Anton */
 65#if 0
 66	__flush_tlb_one(vaddr);
 67#else
 68	flush_tlb_all();
 69#endif
 70
 71	return (void*) vaddr;
 72}
 73EXPORT_SYMBOL(kmap_atomic_high_prot);
 74
 75void kunmap_atomic_high(void *kvaddr)
 76{
 77	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 78	int type;
 79
 80	if (vaddr < FIXADDR_START)
 81		return;
 82
 83	type = kmap_atomic_idx();
 84
 85#ifdef CONFIG_DEBUG_HIGHMEM
 86	{
 87		unsigned long idx;
 88
 89		idx = type + KM_TYPE_NR * smp_processor_id();
 90		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 91
 92		/* XXX Fix - Anton */
 93#if 0
 94		__flush_cache_one(vaddr);
 95#else
 96		flush_cache_all();
 97#endif
 98
 99		/*
100		 * force other mappings to Oops if they'll try to access
101		 * this pte without first remap it
102		 */
103		pte_clear(&init_mm, vaddr, kmap_pte-idx);
104		/* XXX Fix - Anton */
105#if 0
106		__flush_tlb_one(vaddr);
107#else
108		flush_tlb_all();
109#endif
110	}
111#endif
112
113	kmap_atomic_idx_pop();
114}
115EXPORT_SYMBOL(kunmap_atomic_high);