arch/x86/mm/highmem_32.c

#include <linux/highmem.h>
#include <linux/module.h>

void *kmap(struct page *page)
{
	might_sleep();
	if (!PageHighMem(page))
		return page_address(page);
	return kmap_high(page);
}

void kunmap(struct page *page)
{
	if (in_interrupt())
		BUG();
	if (!PageHighMem(page))
		return;
	kunmap_high(page);
}

static void debug_kmap_atomic_prot(enum km_type type)
{
#ifdef CONFIG_DEBUG_HIGHMEM
	static unsigned warn_count = 10;

	if (unlikely(warn_count == 0))
		return;

	if (unlikely(in_interrupt())) {
		if (in_irq()) {
			if (type != KM_IRQ0 && type != KM_IRQ1 &&
			    type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
			    type != KM_BOUNCE_READ) {
				WARN_ON(1);
				warn_count--;
			}
		} else if (!irqs_disabled()) {	/* softirq */
			if (type != KM_IRQ0 && type != KM_IRQ1 &&
			    type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
			    type != KM_SKB_SUNRPC_DATA &&
			    type != KM_SKB_DATA_SOFTIRQ &&
			    type != KM_BOUNCE_READ) {
				WARN_ON(1);
				warn_count--;
			}
		}
	}

	if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
			type == KM_BIO_SRC_IRQ || type == KM_BIO_DST_IRQ) {
		if (!irqs_disabled()) {
			WARN_ON(1);
			warn_count--;
		}
	} else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
		if (irq_count() == 0 && !irqs_disabled()) {
			WARN_ON(1);
			warn_count--;
		}
	}
#endif
}

/*
 * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
 * no global lock is needed and because the kmap code must perform a global TLB
 * invalidation when the kmap pool wraps.
 *
 * However when holding an atomic kmap is is not legal to sleep, so atomic
 * kmaps are appropriate for short, tight code paths only.
 */
void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
{
	enum fixed_addresses idx;
	unsigned long vaddr;

	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
	pagefault_disable();

	if (!PageHighMem(page))
		return page_address(page);

	debug_kmap_atomic_prot(type);

	idx = type + KM_TYPE_NR*smp_processor_id();
	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
	BUG_ON(!pte_none(*(kmap_pte-idx)));
	set_pte(kmap_pte-idx, mk_pte(page, prot));
	arch_flush_lazy_mmu_mode();

	return (void *)vaddr;
}

void *kmap_atomic(struct page *page, enum km_type type)
{
	return kmap_atomic_prot(page, type, kmap_prot);
}

void kunmap_atomic(void *kvaddr, enum km_type type)
{
	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
	enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();

	/*
	 * Force other mappings to Oops if they'll try to access this pte
	 * without first remap it.  Keeping stale mappings around is a bad idea
	 * also, in case the page changes cacheability attributes or becomes
	 * a protected page in a hypervisor.
	 */
	if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
		kpte_clear_flush(kmap_pte-idx, vaddr);
	else {
#ifdef CONFIG_DEBUG_HIGHMEM
		BUG_ON(vaddr < PAGE_OFFSET);
		BUG_ON(vaddr >= (unsigned long)high_memory);
#endif
	}

	arch_flush_lazy_mmu_mode();
	pagefault_enable();
}

/* This is the same as kmap_atomic() but can map memory that doesn't
 * have a struct page associated with it.
 */
void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
{
	enum fixed_addresses idx;
	unsigned long vaddr;

	pagefault_disable();

	idx = type + KM_TYPE_NR*smp_processor_id();
	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
	set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
	arch_flush_lazy_mmu_mode();

	return (void*) vaddr;
}

struct page *kmap_atomic_to_page(void *ptr)
{
	unsigned long idx, vaddr = (unsigned long)ptr;
	pte_t *pte;

	if (vaddr < FIXADDR_START)
		return virt_to_page(ptr);

	idx = virt_to_fix(vaddr);
	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
	return pte_page(*pte);
}

EXPORT_SYMBOL(kmap);
EXPORT_SYMBOL(kunmap);
EXPORT_SYMBOL(kmap_atomic);
EXPORT_SYMBOL(kunmap_atomic);