mmu.c

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/*
 * linux/arch/unicore32/mm/mmu.c
 *
 * Code specific to PKUnity SoC and UniCore ISA
 *
 * Copyright (C) 2001-2010 GUAN Xue-tao
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/mman.h>
#include <linux/nodemask.h>
#include <linux/memblock.h>
#include <linux/fs.h>
#include <linux/bootmem.h>
#include <linux/io.h>

#include <asm/cputype.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/sizes.h>
#include <asm/tlb.h>
#include <asm/memblock.h>

#include <mach/map.h>

#include "mm.h"

/*
 * empty_zero_page is a special page that is used for
 * zero-initialized data and COW.
 */
struct page *empty_zero_page;
EXPORT_SYMBOL(empty_zero_page);

/*
 * The pmd table for the upper-most set of pages.
 */
pmd_t *top_pmd;

pgprot_t pgprot_user;
EXPORT_SYMBOL(pgprot_user);

pgprot_t pgprot_kernel;
EXPORT_SYMBOL(pgprot_kernel);

static int __init noalign_setup(char *__unused)
{
    cr_alignment &= ~CR_A;
    cr_no_alignment &= ~CR_A;
    set_cr(cr_alignment);
    return 1;
}
__setup("noalign", noalign_setup);

void adjust_cr(unsigned long mask, unsigned long set)
{
    unsigned long flags;

    mask &= ~CR_A;

    set &= mask;

    local_irq_save(flags);

    cr_no_alignment = (cr_no_alignment & ~mask) | set;
    cr_alignment = (cr_alignment & ~mask) | set;

    set_cr((get_cr() & ~mask) | set);

    local_irq_restore(flags);
}

struct map_desc {
    unsigned long virtual;
    unsigned long pfn;
    unsigned long length;
    unsigned int type;
};

#define PROT_PTE_DEVICE     (PTE_PRESENT | PTE_YOUNG |  \
                PTE_DIRTY | PTE_READ | PTE_WRITE)
#define PROT_SECT_DEVICE    (PMD_TYPE_SECT | PMD_PRESENT |  \
                PMD_SECT_READ | PMD_SECT_WRITE)

static struct mem_type mem_types[] = {
    [MT_DEVICE] = {       /* Strongly ordered */
        .prot_pte   = PROT_PTE_DEVICE,
        .prot_l1    = PMD_TYPE_TABLE | PMD_PRESENT,
        .prot_sect  = PROT_SECT_DEVICE,
    },
    /*
     * MT_KUSER: pte for vecpage -- cacheable,
     *       and sect for unigfx mmap -- noncacheable
     */
    [MT_KUSER] = {
        .prot_pte  = PTE_PRESENT | PTE_YOUNG | PTE_DIRTY |
                PTE_CACHEABLE | PTE_READ | PTE_EXEC,
        .prot_l1   = PMD_TYPE_TABLE | PMD_PRESENT,
        .prot_sect = PROT_SECT_DEVICE,
    },
    [MT_HIGH_VECTORS] = {
        .prot_pte  = PTE_PRESENT | PTE_YOUNG | PTE_DIRTY |
                PTE_CACHEABLE | PTE_READ | PTE_WRITE |
                PTE_EXEC,
        .prot_l1   = PMD_TYPE_TABLE | PMD_PRESENT,
    },
    [MT_MEMORY] = {
        .prot_pte  = PTE_PRESENT | PTE_YOUNG | PTE_DIRTY |
                PTE_WRITE | PTE_EXEC,
        .prot_l1   = PMD_TYPE_TABLE | PMD_PRESENT,
        .prot_sect = PMD_TYPE_SECT | PMD_PRESENT | PMD_SECT_CACHEABLE |
                PMD_SECT_READ | PMD_SECT_WRITE | PMD_SECT_EXEC,
    },
    [MT_ROM] = {
        .prot_sect = PMD_TYPE_SECT | PMD_PRESENT | PMD_SECT_CACHEABLE |
                PMD_SECT_READ,
    },
};

const struct mem_type *get_mem_type(unsigned int type)
{
    return type < ARRAY_SIZE(mem_types) ? &mem_types[type] : NULL;
}
EXPORT_SYMBOL(get_mem_type);

/*
 * Adjust the PMD section entries according to the CPU in use.
 */
static void __init build_mem_type_table(void)
{
    pgprot_user   = __pgprot(PTE_PRESENT | PTE_YOUNG | PTE_CACHEABLE);
    pgprot_kernel = __pgprot(PTE_PRESENT | PTE_YOUNG |
                 PTE_DIRTY | PTE_READ | PTE_WRITE |
                 PTE_EXEC | PTE_CACHEABLE);
}

#define vectors_base()  (vectors_high() ? 0xffff0000 : 0)

static void __init *early_alloc(unsigned long sz)
{
    void *ptr = __va(memblock_alloc(sz, sz));
    memset(ptr, 0, sz);
    return ptr;
}

static pte_t * __init early_pte_alloc(pmd_t *pmd, unsigned long addr,
        unsigned long prot)
{
    if (pmd_none(*pmd)) {
        pte_t *pte = early_alloc(PTRS_PER_PTE * sizeof(pte_t));
        __pmd_populate(pmd, __pa(pte) | prot);
    }
    BUG_ON(pmd_bad(*pmd));
    return pte_offset_kernel(pmd, addr);
}

static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
                  unsigned long end, unsigned long pfn,
                  const struct mem_type *type)
{
    pte_t *pte = early_pte_alloc(pmd, addr, type->prot_l1);
    do {
        set_pte(pte, pfn_pte(pfn, __pgprot(type->prot_pte)));
        pfn++;
    } while (pte++, addr += PAGE_SIZE, addr != end);
}

static void __init alloc_init_section(pgd_t *pgd, unsigned long addr,
                      unsigned long end, unsigned long phys,
                      const struct mem_type *type)
{
    pmd_t *pmd = pmd_offset((pud_t *)pgd, addr);

    /*
     * Try a section mapping - end, addr and phys must all be aligned
     * to a section boundary.
     */
    if (((addr | end | phys) & ~SECTION_MASK) == 0) {
        pmd_t *p = pmd;

        do {
            set_pmd(pmd, __pmd(phys | type->prot_sect));
            phys += SECTION_SIZE;
        } while (pmd++, addr += SECTION_SIZE, addr != end);

        flush_pmd_entry(p);
    } else {
        /*
         * No need to loop; pte's aren't interested in the
         * individual L1 entries.
         */
        alloc_init_pte(pmd, addr, end, __phys_to_pfn(phys), type);
    }
}

/*
 * Create the page directory entries and any necessary
 * page tables for the mapping specified by `md'.  We
 * are able to cope here with varying sizes and address
 * offsets, and we take full advantage of sections.
 */
static void __init create_mapping(struct map_desc *md)
{
    unsigned long phys, addr, length, end;
    const struct mem_type *type;
    pgd_t *pgd;

    if (md->virtual != vectors_base() && md->virtual < TASK_SIZE) {
        printk(KERN_WARNING "BUG: not creating mapping for "
               "0x%08llx at 0x%08lx in user region\n",
               __pfn_to_phys((u64)md->pfn), md->virtual);
        return;
    }

    if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
        md->virtual >= PAGE_OFFSET && md->virtual < VMALLOC_END) {
        printk(KERN_WARNING "BUG: mapping for 0x%08llx at 0x%08lx "
               "overlaps vmalloc space\n",
               __pfn_to_phys((u64)md->pfn), md->virtual);
    }

    type = &mem_types[md->type];

    addr = md->virtual & PAGE_MASK;
    phys = (unsigned long)__pfn_to_phys(md->pfn);
    length = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK));

    if (type->prot_l1 == 0 && ((addr | phys | length) & ~SECTION_MASK)) {
        printk(KERN_WARNING "BUG: map for 0x%08lx at 0x%08lx can not "
               "be mapped using pages, ignoring.\n",
               __pfn_to_phys(md->pfn), addr);
        return;
    }

    pgd = pgd_offset_k(addr);
    end = addr + length;
    do {
        unsigned long next = pgd_addr_end(addr, end);

        alloc_init_section(pgd, addr, next, phys, type);

        phys += next - addr;
        addr = next;
    } while (pgd++, addr != end);
}

static void * __initdata vmalloc_min = (void *)(VMALLOC_END - SZ_128M);

/*
 * vmalloc=size forces the vmalloc area to be exactly 'size'
 * bytes. This can be used to increase (or decrease) the vmalloc
 * area - the default is 128m.
 */
static int __init early_vmalloc(char *arg)
{
    unsigned long vmalloc_reserve = memparse(arg, NULL);

    if (vmalloc_reserve < SZ_16M) {
        vmalloc_reserve = SZ_16M;
        printk(KERN_WARNING
            "vmalloc area too small, limiting to %luMB\n",
            vmalloc_reserve >> 20);
    }

    if (vmalloc_reserve > VMALLOC_END - (PAGE_OFFSET + SZ_32M)) {
        vmalloc_reserve = VMALLOC_END - (PAGE_OFFSET + SZ_32M);
        printk(KERN_WARNING
            "vmalloc area is too big, limiting to %luMB\n",
            vmalloc_reserve >> 20);
    }

    vmalloc_min = (void *)(VMALLOC_END - vmalloc_reserve);
    return 0;
}
early_param("vmalloc", early_vmalloc);

static phys_addr_t lowmem_limit __initdata = SZ_1G;

static void __init sanity_check_meminfo(void)
{
    int i, j;

    lowmem_limit = __pa(vmalloc_min - 1) + 1;
    memblock_set_current_limit(lowmem_limit);

    for (i = 0, j = 0; i < meminfo.nr_banks; i++) {
        struct membank *bank = &meminfo.bank[j];
        *bank = meminfo.bank[i];
        j++;
    }
    meminfo.nr_banks = j;
}

static inline void prepare_page_table(void)
{
    unsigned long addr;
    phys_addr_t end;

    /*
     * Clear out all the mappings below the kernel image.
     */
    for (addr = 0; addr < MODULES_VADDR; addr += PGDIR_SIZE)
        pmd_clear(pmd_off_k(addr));

    for ( ; addr < PAGE_OFFSET; addr += PGDIR_SIZE)
        pmd_clear(pmd_off_k(addr));

    /*
     * Find the end of the first block of lowmem.
     */
    end = memblock.memory.regions[0].base + memblock.memory.regions[0].size;
    if (end >= lowmem_limit)
        end = lowmem_limit;

    /*
     * Clear out all the kernel space mappings, except for the first
     * memory bank, up to the end of the vmalloc region.
     */
    for (addr = __phys_to_virt(end);
         addr < VMALLOC_END; addr += PGDIR_SIZE)
        pmd_clear(pmd_off_k(addr));
}

/*
 * Reserve the special regions of memory
 */
void __init uc32_mm_memblock_reserve(void)
{
    /*
     * Reserve the page tables.  These are already in use,
     * and can only be in node 0.
     */
    memblock_reserve(__pa(swapper_pg_dir), PTRS_PER_PGD * sizeof(pgd_t));
}

/*
 * Set up device the mappings.  Since we clear out the page tables for all
 * mappings above VMALLOC_END, we will remove any debug device mappings.
 * This means you have to be careful how you debug this function, or any
 * called function.  This means you can't use any function or debugging
 * method which may touch any device, otherwise the kernel _will_ crash.
 */
static void __init devicemaps_init(void)
{
    struct map_desc map;
    unsigned long addr;
    void *vectors;

    /*
     * Allocate the vector page early.
     */
    vectors = early_alloc(PAGE_SIZE);

    for (addr = VMALLOC_END; addr; addr += PGDIR_SIZE)
        pmd_clear(pmd_off_k(addr));

    /*
     * Create a mapping for the machine vectors at the high-vectors
     * location (0xffff0000).  If we aren't using high-vectors, also
     * create a mapping at the low-vectors virtual address.
     */
    map.pfn = __phys_to_pfn(virt_to_phys(vectors));
    map.virtual = VECTORS_BASE;
    map.length = PAGE_SIZE;
    map.type = MT_HIGH_VECTORS;
    create_mapping(&map);

    /*
     * Create a mapping for the kuser page at the special
     * location (0xbfff0000) to the same vectors location.
     */
    map.pfn = __phys_to_pfn(virt_to_phys(vectors));
    map.virtual = KUSER_VECPAGE_BASE;
    map.length = PAGE_SIZE;
    map.type = MT_KUSER;
    create_mapping(&map);

    /*
     * Finally flush the caches and tlb to ensure that we're in a
     * consistent state wrt the writebuffer.  This also ensures that
     * any write-allocated cache lines in the vector page are written
     * back.  After this point, we can start to touch devices again.
     */
    local_flush_tlb_all();
    flush_cache_all();
}

static void __init map_lowmem(void)
{
    struct memblock_region *reg;

    /* Map all the lowmem memory banks. */
    for_each_memblock(memory, reg) {
        phys_addr_t start = reg->base;
        phys_addr_t end = start + reg->size;
        struct map_desc map;

        if (end > lowmem_limit)
            end = lowmem_limit;
        if (start >= end)
            break;

        map.pfn = __phys_to_pfn(start);
        map.virtual = __phys_to_virt(start);
        map.length = end - start;
        map.type = MT_MEMORY;

        create_mapping(&map);
    }
}

/*
 * paging_init() sets up the page tables, initialises the zone memory
 * maps, and sets up the zero page, bad page and bad page tables.
 */
void __init paging_init(void)
{
    void *zero_page;

    build_mem_type_table();
    sanity_check_meminfo();
    prepare_page_table();
    map_lowmem();
    devicemaps_init();

    top_pmd = pmd_off_k(0xffff0000);

    /* allocate the zero page. */
    zero_page = early_alloc(PAGE_SIZE);

    bootmem_init();

    empty_zero_page = virt_to_page(zero_page);
    __flush_dcache_page(NULL, empty_zero_page);
}

/*
 * In order to soft-boot, we need to insert a 1:1 mapping in place of
 * the user-mode pages.  This will then ensure that we have predictable
 * results when turning the mmu off
 */
void setup_mm_for_reboot(char mode)
{
    unsigned long base_pmdval;
    pgd_t *pgd;
    int i;

    /*
     * We need to access to user-mode page tables here. For kernel threads
     * we don't have any user-mode mappings so we use the context that we
     * "borrowed".
     */
    pgd = current->active_mm->pgd;

    base_pmdval = PMD_SECT_WRITE | PMD_SECT_READ | PMD_TYPE_SECT;

    for (i = 0; i < FIRST_USER_PGD_NR + USER_PTRS_PER_PGD; i++, pgd++) {
        unsigned long pmdval = (i << PGDIR_SHIFT) | base_pmdval;
        pmd_t *pmd;

        pmd = pmd_off(pgd, i << PGDIR_SHIFT);
        set_pmd(pmd, __pmd(pmdval));
        flush_pmd_entry(pmd);
    }

    local_flush_tlb_all();
}

/*
 * Take care of architecture specific things when placing a new PTE into
 * a page table, or changing an existing PTE.  Basically, there are two
 * things that we need to take care of:
 *
 *  1. If PG_dcache_clean is not set for the page, we need to ensure
 *     that any cache entries for the kernels virtual memory
 *     range are written back to the page.
 *  2. If we have multiple shared mappings of the same space in
 *     an object, we need to deal with the cache aliasing issues.
 *
 * Note that the pte lock will be held.
 */
void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr,
    pte_t *ptep)
{
    unsigned long pfn = pte_pfn(*ptep);
    struct address_space *mapping;
    struct page *page;

    if (!pfn_valid(pfn))
        return;

    /*
     * The zero page is never written to, so never has any dirty
     * cache lines, and therefore never needs to be flushed.
     */
    page = pfn_to_page(pfn);
    if (page == ZERO_PAGE(0))
        return;

    mapping = page_mapping(page);
    if (!test_and_set_bit(PG_dcache_clean, &page->flags))
        __flush_dcache_page(mapping, page);
    if (mapping)
        if (vma->vm_flags & VM_EXEC)
            __flush_icache_all();
}