/*
 *  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 <mingo@elte.hu>
 */

#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 <linux/security.h>
#include <asm/pgalloc.h>

unsigned long mmap_rnd_mask;
unsigned long mmap_align_mask;

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;
}

unsigned long arch_mmap_rnd(void)
{
        if (is_32bit_task())
                return (get_random_int() & 0x7ff) << PAGE_SHIFT;
        else
                return (get_random_int() & mmap_rnd_mask) << PAGE_SHIFT;
}

static unsigned long mmap_base_legacy(unsigned long rnd)
{
        return TASK_UNMAPPED_BASE + rnd;
}

static inline unsigned long mmap_base(unsigned long rnd)
{
        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() - rnd - gap;
}

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;
        struct vm_unmapped_area_info info;
        int do_color_align;
        int rc;

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

        if (flags & MAP_FIXED)
                goto check_asce_limit;

        if (addr) {
                addr = PAGE_ALIGN(addr);
                vma = find_vma(mm, addr);
                if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
                    (!vma || addr + len <= vm_start_gap(vma)))
                        goto check_asce_limit;
        }

        do_color_align = 0;
        if (filp || (flags & MAP_SHARED))
                do_color_align = !is_32bit_task();

        info.flags = 0;
        info.length = len;
        info.low_limit = mm->mmap_base;
        info.high_limit = TASK_SIZE;
        info.align_mask = do_color_align ? (mmap_align_mask << PAGE_SHIFT) : 0;
        info.align_offset = pgoff << PAGE_SHIFT;
        addr = vm_unmapped_area(&info);
        if (addr & ~PAGE_MASK)
                return addr;

check_asce_limit:
        if (addr + len > current->mm->context.asce_limit &&
            addr + len <= TASK_SIZE) {
                rc = crst_table_upgrade(mm);
                if (rc)
                        return (unsigned long) rc;
        }

        return addr;
}

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;
        struct vm_unmapped_area_info info;
        int do_color_align;
        int rc;

        /* requested length too big for entire address space */
        if (len > TASK_SIZE - mmap_min_addr)
                return -ENOMEM;

        if (flags & MAP_FIXED)
                goto check_asce_limit;

        /* requesting a specific address */
        if (addr) {
                addr = PAGE_ALIGN(addr);
                vma = find_vma(mm, addr);
                if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
                                (!vma || addr + len <= vma->vm_start))
                        goto check_asce_limit;
        }

        do_color_align = 0;
        if (filp || (flags & MAP_SHARED))
                do_color_align = !is_32bit_task();

        info.flags = VM_UNMAPPED_AREA_TOPDOWN;
        info.length = len;
        info.low_limit = max(PAGE_SIZE, mmap_min_addr);
        info.high_limit = mm->mmap_base;
        info.align_mask = do_color_align ? (mmap_align_mask << PAGE_SHIFT) : 0;
        info.align_offset = pgoff << PAGE_SHIFT;
        addr = vm_unmapped_area(&info);

        /*
         * 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.
         */
        if (addr & ~PAGE_MASK) {
                VM_BUG_ON(addr != -ENOMEM);
                info.flags = 0;
                info.low_limit = TASK_UNMAPPED_BASE;
                info.high_limit = TASK_SIZE;
                addr = vm_unmapped_area(&info);
                if (addr & ~PAGE_MASK)
                        return addr;
        }

check_asce_limit:
        if (addr + len > current->mm->context.asce_limit &&
            addr + len <= TASK_SIZE) {
                rc = crst_table_upgrade(mm);
                if (rc)
                        return (unsigned long) rc;
        }
        return addr;
}

/*
 * 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)
{
        unsigned long random_factor = 0UL;

        if (current->flags & PF_RANDOMIZE)
                random_factor = arch_mmap_rnd();

        /*
         * 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 = mmap_base_legacy(random_factor);
                mm->get_unmapped_area = arch_get_unmapped_area;
                mm->unmap_area = arch_unmap_area;
        } else {
                mm->mmap_base = mmap_base(random_factor);
                mm->get_unmapped_area = arch_get_unmapped_area_topdown;
                mm->unmap_area = arch_unmap_area_topdown;
        }
}

static int __init setup_mmap_rnd(void)
{
        struct cpuid cpu_id;

        get_cpu_id(&cpu_id);
        switch (cpu_id.machine) {
        case 0x9672:
        case 0x2064:
        case 0x2066:
        case 0x2084:
        case 0x2086:
        case 0x2094:
        case 0x2096:
        case 0x2097:
        case 0x2098:
        case 0x2817:
        case 0x2818:
        case 0x2827:
        case 0x2828:
                mmap_rnd_mask = 0x7ffUL;
                mmap_align_mask = 0UL;
                break;
        case 0x2964:    /* z13 */
        default:
                mmap_rnd_mask = 0x3ff80UL;
                mmap_align_mask = 0x7fUL;
                break;
        }
        return 0;
}
early_initcall(setup_mmap_rnd);