mmap.c

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/*
 * arch/sh/mm/mmap.c
 *
 * Copyright (C) 2008 - 2009  Paul Mundt
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/module.h>
#include <asm/page.h>
#include <asm/processor.h>

unsigned long shm_align_mask = PAGE_SIZE - 1;   /* Sane caches */
EXPORT_SYMBOL(shm_align_mask);

#ifdef CONFIG_MMU
/*
 * To avoid cache aliases, we map the shared page with same color.
 */
static inline unsigned long COLOUR_ALIGN(unsigned long addr,
                     unsigned long pgoff)
{
    unsigned long base = (addr + shm_align_mask) & ~shm_align_mask;
    unsigned long off = (pgoff << PAGE_SHIFT) & shm_align_mask;

    return base + off;
}

static inline unsigned long COLOUR_ALIGN_DOWN(unsigned long addr,
                          unsigned long pgoff)
{
    unsigned long base = addr & ~shm_align_mask;
    unsigned long off = (pgoff << PAGE_SHIFT) & shm_align_mask;

    if (base + off <= addr)
        return base + off;

    return base - off;
}

unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
    unsigned long len, unsigned long pgoff, unsigned long flags)
{
    struct mm_struct *mm = current->mm;
    struct vm_area_struct *vma;
    unsigned long start_addr;
    int do_colour_align;

    if (flags & MAP_FIXED) {
        /* We do not accept a shared mapping if it would violate
         * cache aliasing constraints.
         */
        if ((flags & MAP_SHARED) &&
            ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
            return -EINVAL;
        return addr;
    }

    if (unlikely(len > TASK_SIZE))
        return -ENOMEM;

    do_colour_align = 0;
    if (filp || (flags & MAP_SHARED))
        do_colour_align = 1;

    if (addr) {
        if (do_colour_align)
            addr = COLOUR_ALIGN(addr, pgoff);
        else
            addr = PAGE_ALIGN(addr);

        vma = find_vma(mm, addr);
        if (TASK_SIZE - len >= addr &&
            (!vma || addr + len <= vma->vm_start))
            return addr;
    }

    if (len > mm->cached_hole_size) {
        start_addr = addr = mm->free_area_cache;
    } else {
            mm->cached_hole_size = 0;
        start_addr = addr = TASK_UNMAPPED_BASE;
    }

full_search:
    if (do_colour_align)
        addr = COLOUR_ALIGN(addr, pgoff);
    else
        addr = PAGE_ALIGN(mm->free_area_cache);

    for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
        /* At this point:  (!vma || addr < vma->vm_end). */
        if (unlikely(TASK_SIZE - len < addr)) {
            /*
             * Start a new search - just in case we missed
             * some holes.
             */
            if (start_addr != TASK_UNMAPPED_BASE) {
                start_addr = addr = TASK_UNMAPPED_BASE;
                mm->cached_hole_size = 0;
                goto full_search;
            }
            return -ENOMEM;
        }
        if (likely(!vma || addr + len <= vma->vm_start)) {
            /*
             * Remember the place where we stopped the search:
             */
            mm->free_area_cache = addr + len;
            return addr;
        }
        if (addr + mm->cached_hole_size < vma->vm_start)
                mm->cached_hole_size = vma->vm_start - addr;

        addr = vma->vm_end;
        if (do_colour_align)
            addr = COLOUR_ALIGN(addr, pgoff);
    }
}

unsigned long
arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
              const unsigned long len, const unsigned long pgoff,
              const unsigned long flags)
{
    struct vm_area_struct *vma;
    struct mm_struct *mm = current->mm;
    unsigned long addr = addr0;
    int do_colour_align;

    if (flags & MAP_FIXED) {
        /* We do not accept a shared mapping if it would violate
         * cache aliasing constraints.
         */
        if ((flags & MAP_SHARED) &&
            ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
            return -EINVAL;
        return addr;
    }

    if (unlikely(len > TASK_SIZE))
        return -ENOMEM;

    do_colour_align = 0;
    if (filp || (flags & MAP_SHARED))
        do_colour_align = 1;

    /* requesting a specific address */
    if (addr) {
        if (do_colour_align)
            addr = COLOUR_ALIGN(addr, pgoff);
        else
            addr = PAGE_ALIGN(addr);

        vma = find_vma(mm, addr);
        if (TASK_SIZE - len >= addr &&
            (!vma || addr + len <= vma->vm_start))
            return addr;
    }

    /* check if free_area_cache is useful for us */
    if (len <= mm->cached_hole_size) {
            mm->cached_hole_size = 0;
        mm->free_area_cache = mm->mmap_base;
    }

    /* either no address requested or can't fit in requested address hole */
    addr = mm->free_area_cache;
    if (do_colour_align) {
        unsigned long base = COLOUR_ALIGN_DOWN(addr-len, pgoff);

        addr = base + len;
    }

    /* make sure it can fit in the remaining address space */
    if (likely(addr > len)) {
        vma = find_vma(mm, addr-len);
        if (!vma || addr <= vma->vm_start) {
            /* remember the address as a hint for next time */
            return (mm->free_area_cache = addr-len);
        }
    }

    if (unlikely(mm->mmap_base < len))
        goto bottomup;

    addr = mm->mmap_base-len;
    if (do_colour_align)
        addr = COLOUR_ALIGN_DOWN(addr, pgoff);

    do {
        /*
         * Lookup failure means no vma is above this address,
         * else if new region fits below vma->vm_start,
         * return with success:
         */
        vma = find_vma(mm, addr);
        if (likely(!vma || addr+len <= vma->vm_start)) {
            /* remember the address as a hint for next time */
            return (mm->free_area_cache = addr);
        }

        /* remember the largest hole we saw so far */
        if (addr + mm->cached_hole_size < vma->vm_start)
                mm->cached_hole_size = vma->vm_start - addr;

        /* try just below the current vma->vm_start */
        addr = vma->vm_start-len;
        if (do_colour_align)
            addr = COLOUR_ALIGN_DOWN(addr, pgoff);
    } while (likely(len < vma->vm_start));

bottomup:
    /*
     * A failed mmap() very likely causes application failure,
     * so fall back to the bottom-up function here. This scenario
     * can happen with large stack limits and large mmap()
     * allocations.
     */
    mm->cached_hole_size = ~0UL;
    mm->free_area_cache = TASK_UNMAPPED_BASE;
    addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
    /*
     * Restore the topdown base:
     */
    mm->free_area_cache = mm->mmap_base;
    mm->cached_hole_size = ~0UL;

    return addr;
}
#endif /* CONFIG_MMU */

/*
 * You really shouldn't be using read() or write() on /dev/mem.  This
 * might go away in the future.
 */
int valid_phys_addr_range(unsigned long addr, size_t count)
{
    if (addr < __MEMORY_START)
        return 0;
    if (addr + count > __pa(high_memory))
        return 0;

    return 1;
}

int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
{
    return 1;
}