root/arch/x86/mm/highmem_32.c

DEFINITIONS

1. kmap
2. kunmap
3. debug_kmap_atomic_prot
4. kmap_atomic_prot
5. kmap_atomic
6. kunmap_atomic
7. kmap_atomic_pfn
8. kmap_atomic_to_page

#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);