1 files changed, 221 insertions, 0 deletions

diff --git a/arch/i386/mm/pageattr.c b/arch/i386/mm/pageattr.c
new file mode 100644
index 000000000000..cb3da6baa704
--- /dev/null
+++ b/arch/i386/mm/pageattr.c
@@ -0,0 +1,221 @@
+/* 
+ * Copyright 2002 Andi Kleen, SuSE Labs. 
+ * Thanks to Ben LaHaise for precious feedback.
+ */ 
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <asm/uaccess.h>
+#include <asm/processor.h>
+#include <asm/tlbflush.h>
+
+static DEFINE_SPINLOCK(cpa_lock);
+static struct list_head df_list = LIST_HEAD_INIT(df_list);
+
+
+pte_t *lookup_address(unsigned long address) 
+{ 
+        pgd_t *pgd = pgd_offset_k(address);
+        pud_t *pud;
+        pmd_t *pmd;
+        if (pgd_none(*pgd))
+                return NULL;
+        pud = pud_offset(pgd, address);
+        if (pud_none(*pud))
+                return NULL;
+        pmd = pmd_offset(pud, address);
+        if (pmd_none(*pmd))
+                return NULL;
+        if (pmd_large(*pmd))
+                return (pte_t *)pmd;
+        return pte_offset_kernel(pmd, address);
+} 
+
+static struct page *split_large_page(unsigned long address, pgprot_t prot)
+{ 
+        int i; 
+        unsigned long addr;
+        struct page *base;
+        pte_t *pbase;
+
+        spin_unlock_irq(&cpa_lock);
+        base = alloc_pages(GFP_KERNEL, 0);
+        spin_lock_irq(&cpa_lock);
+        if (!base) 
+                return NULL;
+
+        address = __pa(address);
+        addr = address & LARGE_PAGE_MASK; 
+        pbase = (pte_t *)page_address(base);
+        for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
+                pbase[i] = pfn_pte(addr >> PAGE_SHIFT, 
+                                   addr == address ? prot : PAGE_KERNEL);
+        }
+        return base;
+} 
+
+static void flush_kernel_map(void *dummy) 
+{ 
+        /* Could use CLFLUSH here if the CPU supports it (Hammer,P4) */
+        if (boot_cpu_data.x86_model >= 4) 
+                asm volatile("wbinvd":::"memory"); 
+        /* Flush all to work around Errata in early athlons regarding 
+         * large page flushing. 
+         */
+        __flush_tlb_all();      
+}
+
+static void set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte) 
+{ 
+        struct page *page;
+        unsigned long flags;
+
+        set_pte_atomic(kpte, pte);      /* change init_mm */
+        if (PTRS_PER_PMD > 1)
+                return;
+
+        spin_lock_irqsave(&pgd_lock, flags);
+        for (page = pgd_list; page; page = (struct page *)page->index) {
+                pgd_t *pgd;
+                pud_t *pud;
+                pmd_t *pmd;
+                pgd = (pgd_t *)page_address(page) + pgd_index(address);
+                pud = pud_offset(pgd, address);
+                pmd = pmd_offset(pud, address);
+                set_pte_atomic((pte_t *)pmd, pte);
+        }
+        spin_unlock_irqrestore(&pgd_lock, flags);
+}
+
+/* 
+ * No more special protections in this 2/4MB area - revert to a
+ * large page again. 
+ */
+static inline void revert_page(struct page *kpte_page, unsigned long address)
+{
+        pte_t *linear = (pte_t *) 
+                pmd_offset(pud_offset(pgd_offset_k(address), address), address);
+        set_pmd_pte(linear,  address,
+                    pfn_pte((__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT,
+                            PAGE_KERNEL_LARGE));
+}
+
+static int
+__change_page_attr(struct page *page, pgprot_t prot)
+{ 
+        pte_t *kpte; 
+        unsigned long address;
+        struct page *kpte_page;
+
+        BUG_ON(PageHighMem(page));
+        address = (unsigned long)page_address(page);
+
+        kpte = lookup_address(address);
+        if (!kpte)
+                return -EINVAL;
+        kpte_page = virt_to_page(kpte);
+        if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) { 
+                if ((pte_val(*kpte) & _PAGE_PSE) == 0) { 
+                        set_pte_atomic(kpte, mk_pte(page, prot)); 
+                } else {
+                        struct page *split = split_large_page(address, prot); 
+                        if (!split)
+                                return -ENOMEM;
+                        set_pmd_pte(kpte,address,mk_pte(split, PAGE_KERNEL));
+                        kpte_page = split;
+                }       
+                get_page(kpte_page);
+        } else if ((pte_val(*kpte) & _PAGE_PSE) == 0) { 
+                set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
+                __put_page(kpte_page);
+        } else
+                BUG();
+
+        /*
+         * If the pte was reserved, it means it was created at boot
+         * time (not via split_large_page) and in turn we must not
+         * replace it with a largepage.
+         */
+        if (!PageReserved(kpte_page)) {
+                /* memleak and potential failed 2M page regeneration */
+                BUG_ON(!page_count(kpte_page));
+
+                if (cpu_has_pse && (page_count(kpte_page) == 1)) {
+                        list_add(&kpte_page->lru, &df_list);
+                        revert_page(kpte_page, address);
+                }
+        }
+        return 0;
+} 
+
+static inline void flush_map(void)
+{
+        on_each_cpu(flush_kernel_map, NULL, 1, 1);
+}
+
+/*
+ * Change the page attributes of an page in the linear mapping.
+ *
+ * This should be used when a page is mapped with a different caching policy
+ * than write-back somewhere - some CPUs do not like it when mappings with
+ * different caching policies exist. This changes the page attributes of the
+ * in kernel linear mapping too.
+ * 
+ * The caller needs to ensure that there are no conflicting mappings elsewhere.
+ * This function only deals with the kernel linear map.
+ * 
+ * Caller must call global_flush_tlb() after this.
+ */
+int change_page_attr(struct page *page, int numpages, pgprot_t prot)
+{
+        int err = 0; 
+        int i; 
+        unsigned long flags;
+
+        spin_lock_irqsave(&cpa_lock, flags);
+        for (i = 0; i < numpages; i++, page++) { 
+                err = __change_page_attr(page, prot);
+                if (err) 
+                        break; 
+        }       
+        spin_unlock_irqrestore(&cpa_lock, flags);
+        return err;
+}
+
+void global_flush_tlb(void)
+{ 
+        LIST_HEAD(l);
+        struct page *pg, *next;
+
+        BUG_ON(irqs_disabled());
+
+        spin_lock_irq(&cpa_lock);
+        list_splice_init(&df_list, &l);
+        spin_unlock_irq(&cpa_lock);
+        flush_map();
+        list_for_each_entry_safe(pg, next, &l, lru)
+                __free_page(pg);
+} 
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void kernel_map_pages(struct page *page, int numpages, int enable)
+{
+        if (PageHighMem(page))
+                return;
+        /* the return value is ignored - the calls cannot fail,
+         * large pages are disabled at boot time.
+         */
+        change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
+        /* we should perform an IPI and flush all tlbs,
+         * but that can deadlock->flush only current cpu.
+         */
+        __flush_tlb_all();
+}
+#endif
+
+EXPORT_SYMBOL(change_page_attr);
+EXPORT_SYMBOL(global_flush_tlb);