mmap.c

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/*
 *  flexible mmap layout support
 *
 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *
 * Started by Ingo Molnar <[email protected]>
 */

#include <linux/personality.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/compat.h>
#include <asm/pgalloc.h>

static unsigned long stack_maxrandom_size(void)
{
    if (!(current->flags & PF_RANDOMIZE))
        return 0;
    if (current->personality & ADDR_NO_RANDOMIZE)
        return 0;
    return STACK_RND_MASK << PAGE_SHIFT;
}

/*
 * Top of mmap area (just below the process stack).
 *
 * Leave at least a ~32 MB hole.
 */
#define MIN_GAP (32*1024*1024)
#define MAX_GAP (STACK_TOP/6*5)

static inline int mmap_is_legacy(void)
{
    if (current->personality & ADDR_COMPAT_LAYOUT)
        return 1;
    if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
        return 1;
    return sysctl_legacy_va_layout;
}

static unsigned long mmap_rnd(void)
{
    if (!(current->flags & PF_RANDOMIZE))
        return 0;
    /* 8MB randomization for mmap_base */
    return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
}

static inline unsigned long mmap_base(void)
{
    unsigned long gap = rlimit(RLIMIT_STACK);

    if (gap < MIN_GAP)
        gap = MIN_GAP;
    else if (gap > MAX_GAP)
        gap = MAX_GAP;
    gap &= PAGE_MASK;
    return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
}

#ifndef CONFIG_64BIT

/*
 * This function, called very early during the creation of a new
 * process VM image, sets up which VM layout function to use:
 */
void arch_pick_mmap_layout(struct mm_struct *mm)
{
    /*
     * Fall back to the standard layout if the personality
     * bit is set, or if the expected stack growth is unlimited:
     */
    if (mmap_is_legacy()) {
        mm->mmap_base = TASK_UNMAPPED_BASE;
        mm->get_unmapped_area = arch_get_unmapped_area;
        mm->unmap_area = arch_unmap_area;
    } else {
        mm->mmap_base = mmap_base();
        mm->get_unmapped_area = arch_get_unmapped_area_topdown;
        mm->unmap_area = arch_unmap_area_topdown;
    }
}

#else

int s390_mmap_check(unsigned long addr, unsigned long len)
{
    int rc;

    if (!is_compat_task() &&
        len >= TASK_SIZE && TASK_SIZE < (1UL << 53)) {
        rc = crst_table_upgrade(current->mm, 1UL << 53);
        if (rc)
            return rc;
        update_mm(current->mm, current);
    }
    return 0;
}

static unsigned long
s390_get_unmapped_area(struct file *filp, unsigned long addr,
        unsigned long len, unsigned long pgoff, unsigned long flags)
{
    struct mm_struct *mm = current->mm;
    unsigned long area;
    int rc;

    area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
    if (!(area & ~PAGE_MASK))
        return area;
    if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
        /* Upgrade the page table to 4 levels and retry. */
        rc = crst_table_upgrade(mm, 1UL << 53);
        if (rc)
            return (unsigned long) rc;
        update_mm(mm, current);
        area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
    }
    return area;
}

static unsigned long
s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
              const unsigned long len, const unsigned long pgoff,
              const unsigned long flags)
{
    struct mm_struct *mm = current->mm;
    unsigned long area;
    int rc;

    area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
    if (!(area & ~PAGE_MASK))
        return area;
    if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
        /* Upgrade the page table to 4 levels and retry. */
        rc = crst_table_upgrade(mm, 1UL << 53);
        if (rc)
            return (unsigned long) rc;
        update_mm(mm, current);
        area = arch_get_unmapped_area_topdown(filp, addr, len,
                              pgoff, flags);
    }
    return area;
}
/*
 * This function, called very early during the creation of a new
 * process VM image, sets up which VM layout function to use:
 */
void arch_pick_mmap_layout(struct mm_struct *mm)
{
    /*
     * Fall back to the standard layout if the personality
     * bit is set, or if the expected stack growth is unlimited:
     */
    if (mmap_is_legacy()) {
        mm->mmap_base = TASK_UNMAPPED_BASE;
        mm->get_unmapped_area = s390_get_unmapped_area;
        mm->unmap_area = arch_unmap_area;
    } else {
        mm->mmap_base = mmap_base();
        mm->get_unmapped_area = s390_get_unmapped_area_topdown;
        mm->unmap_area = arch_unmap_area_topdown;
    }
}

#endif