/*
   *  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 <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 unsigned long mmap_base_legacy(void)
  {
  	return TASK_UNMAPPED_BASE + mmap_rnd();
  }
  
  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 = mmap_base_legacy();
  		mm->get_unmapped_area = arch_get_unmapped_area;
  	} else {
  		mm->mmap_base = mmap_base();
  		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
  	}
  }
  
  #else
  
  int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
  {
  	if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
  		return 0;
  	if (!(flags & MAP_FIXED))
  		addr = 0;
  	if ((addr + len) >= TASK_SIZE)
  		return crst_table_upgrade(current->mm, 1UL << 53);
  	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;
  		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;
  		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 = mmap_base_legacy();
  		mm->get_unmapped_area = s390_get_unmapped_area;
  	} else {
  		mm->mmap_base = mmap_base();
  		mm->get_unmapped_area = s390_get_unmapped_area_topdown;
  	}
  }
  
  #endif