1 files changed, 89 insertions, 0 deletions

diff --git a/arch/i386/mm/highmem.c b/arch/i386/mm/highmem.c
new file mode 100644
index 000000000000..fc4c4cad4e98
--- /dev/null
+++ b/arch/i386/mm/highmem.c
@@ -0,0 +1,89 @@
+#include <linux/highmem.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);
+}
+
+/*
+ * 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(struct page *page, enum km_type type)
+{
+        enum fixed_addresses idx;
+        unsigned long vaddr;
+
+        /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
+        inc_preempt_count();
+        if (!PageHighMem(page))
+                return page_address(page);
+
+        idx = type + KM_TYPE_NR*smp_processor_id();
+        vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+#ifdef CONFIG_DEBUG_HIGHMEM
+        if (!pte_none(*(kmap_pte-idx)))
+                BUG();
+#endif
+        set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
+        __flush_tlb_one(vaddr);
+
+        return (void*) vaddr;
+}
+
+void kunmap_atomic(void *kvaddr, enum km_type type)
+{
+#ifdef CONFIG_DEBUG_HIGHMEM
+        unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
+        enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
+
+        if (vaddr < FIXADDR_START) { // FIXME
+                dec_preempt_count();
+                preempt_check_resched();
+                return;
+        }
+
+        if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
+                BUG();
+
+        /*
+         * force other mappings to Oops if they'll try to access
+         * this pte without first remap it
+         */
+        pte_clear(&init_mm, vaddr, kmap_pte-idx);
+        __flush_tlb_one(vaddr);
+#endif
+
+        dec_preempt_count();
+        preempt_check_resched();
+}
+
+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);
+}
+