/* 
 * Copyright 2002 Andi Kleen, SuSE Labs. 
 * Thanks to Ben LaHaise for precious feedback.
 */ 

#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>
#include <asm/pgalloc.h>
#include <asm/sections.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,
                                        pgprot_t ref_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;

        /*
         * page_private is used to track the number of entries in
         * the page table page that have non standard attributes.
         */
        SetPagePrivate(base);
        page_private(base) = 0;

        address = __pa(address);
        addr = address & LARGE_PAGE_MASK; 
        pbase = (pte_t *)page_address(base);
        paravirt_alloc_pt(page_to_pfn(base));
        for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
               set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
                                          addr == address ? prot : ref_prot));
        }
        return base;
} 

static void cache_flush_page(struct page *p)
{ 
        unsigned long adr = (unsigned long)page_address(p);
        int i;
        for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size)
                asm volatile("clflush (%0)" :: "r" (adr + i));
}

static void flush_kernel_map(void *arg)
{
        struct list_head *lh = (struct list_head *)arg;
        struct page *p;

        /* High level code is not ready for clflush yet */
        if (0 && cpu_has_clflush) {
                list_for_each_entry (p, lh, lru)
                        cache_flush_page(p);
        } else if (boot_cpu_data.x86_model >= 4)
                wbinvd();

        /* 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 (SHARED_KERNEL_PMD)
                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)
{
        pgprot_t ref_prot;
        pte_t *linear;

        ref_prot =
        ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
                ? PAGE_KERNEL_LARGE_EXEC : PAGE_KERNEL_LARGE;

        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,
                            ref_prot));
}

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_huge(*kpte)) {
                        set_pte_atomic(kpte, mk_pte(page, prot)); 
                } else {
                        pgprot_t ref_prot;
                        struct page *split;

                        ref_prot =
                        ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
                                ? PAGE_KERNEL_EXEC : PAGE_KERNEL;
                        split = split_large_page(address, prot, ref_prot);
                        if (!split)
                                return -ENOMEM;
                        set_pmd_pte(kpte,address,mk_pte(split, ref_prot));
                        kpte_page = split;
                }
                page_private(kpte_page)++;
        } else if (!pte_huge(*kpte)) {
                set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
                BUG_ON(page_private(kpte_page) == 0);
                page_private(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)) {
                if (cpu_has_pse && (page_private(kpte_page) == 0)) {
                        ClearPagePrivate(kpte_page);
                        paravirt_release_pt(page_to_pfn(kpte_page));
                        list_add(&kpte_page->lru, &df_list);
                        revert_page(kpte_page, address);
                }
        }
        return 0;
} 

static inline void flush_map(struct list_head *l)
{
        on_each_cpu(flush_kernel_map, l, 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)
{
        struct list_head l;
        struct page *pg, *next;

        BUG_ON(irqs_disabled());

        spin_lock_irq(&cpa_lock);
        list_replace_init(&df_list, &l);
        spin_unlock_irq(&cpa_lock);
        flush_map(&l);
        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;
        if (!enable)
                debug_check_no_locks_freed(page_address(page),
                                           numpages * PAGE_SIZE);

        /* 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);