/*
 * 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.
 *
 * Copyright (C) 2011 Wind River Systems,
 *   written by Ralf Baechle <ralf@linux-mips.org>
 */
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/export.h>
#include <linux/personality.h>
#include <linux/random.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>

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

/* gap between mmap and stack */
#define MIN_GAP (128*1024*1024UL)
#define MAX_GAP ((TASK_SIZE)/6*5)

static 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_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;

        return PAGE_ALIGN(TASK_SIZE - gap - rnd);
}

#define COLOUR_ALIGN(addr, pgoff)                               \
        ((((addr) + shm_align_mask) & ~shm_align_mask) +        \
         (((pgoff) << PAGE_SHIFT) & shm_align_mask))

enum mmap_allocation_direction {UP, DOWN};

static unsigned long arch_get_unmapped_area_common(struct file *filp,
        unsigned long addr0, unsigned long len, unsigned long pgoff,
        unsigned long flags, enum mmap_allocation_direction dir)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long addr = addr0;
        int do_color_align;
        struct vm_unmapped_area_info info;

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

        if (flags & MAP_FIXED) {
                /* Even MAP_FIXED mappings must reside within TASK_SIZE */
                if (TASK_SIZE - len < addr)
                        return -EINVAL;

                /*
                 * 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;
        }

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

        /* requesting a specific address */
        if (addr) {
                if (do_color_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;
        }

        info.length = len;
        info.align_mask = do_color_align ? (PAGE_MASK & shm_align_mask) : 0;
        info.align_offset = pgoff << PAGE_SHIFT;

        if (dir == DOWN) {
                info.flags = VM_UNMAPPED_AREA_TOPDOWN;
                info.low_limit = PAGE_SIZE;
                info.high_limit = mm->mmap_base;
                addr = vm_unmapped_area(&info);

                if (!(addr & ~PAGE_MASK))
                        return addr;

                /*
                 * 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.
                 */
        }

        info.flags = 0;
        info.low_limit = mm->mmap_base;
        info.high_limit = TASK_SIZE;
        return vm_unmapped_area(&info);
}

unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0,
        unsigned long len, unsigned long pgoff, unsigned long flags)
{
        return arch_get_unmapped_area_common(filp,
                        addr0, len, pgoff, flags, UP);
}

/*
 * There is no need to export this but sched.h declares the function as
 * extern so making it static here results in an error.
 */
unsigned long arch_get_unmapped_area_topdown(struct file *filp,
        unsigned long addr0, unsigned long len, unsigned long pgoff,
        unsigned long flags)
{
        return arch_get_unmapped_area_common(filp,
                        addr0, len, pgoff, flags, DOWN);
}

unsigned long arch_mmap_rnd(void)
{
        unsigned long rnd;

#ifdef CONFIG_COMPAT
        if (TASK_IS_32BIT_ADDR)
                rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
        else
#endif /* CONFIG_COMPAT */
                rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);

        return rnd << PAGE_SHIFT;
}

void arch_pick_mmap_layout(struct mm_struct *mm)
{
        unsigned long random_factor = 0UL;

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

        if (mmap_is_legacy()) {
                mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
                mm->get_unmapped_area = arch_get_unmapped_area;
        } else {
                mm->mmap_base = mmap_base(random_factor);
                mm->get_unmapped_area = arch_get_unmapped_area_topdown;
        }
}

static inline unsigned long brk_rnd(void)
{
        unsigned long rnd = get_random_long();

        rnd = rnd << PAGE_SHIFT;
        /* 8MB for 32bit, 256MB for 64bit */
        if (TASK_IS_32BIT_ADDR)
                rnd = rnd & 0x7ffffful;
        else
                rnd = rnd & 0xffffffful;

        return rnd;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
        unsigned long base = mm->brk;
        unsigned long ret;

        ret = PAGE_ALIGN(base + brk_rnd());

        if (ret < mm->brk)
                return mm->brk;

        return ret;
}

int __virt_addr_valid(const volatile void *kaddr)
{
        return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
}
EXPORT_SYMBOL_GPL(__virt_addr_valid);