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);