[mirror_ubuntu-zesty-kernel.git] / arch / powerpc / mm / mmap.c

/*
 *  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/random.h>
#include <linux/sched.h>

/*
 * Top of mmap area (just below the process stack).
 *
 * Leave at least a ~128 MB hole on 32bit applications.
 *
 * On 64bit applications we randomise the stack by 1GB so we need to
 * space our mmap start address by a further 1GB, otherwise there is a
 * chance the mmap area will end up closer to the stack than our ulimit
 * requires.
 */
#define MIN_GAP32 (128*1024*1024)
#define MIN_GAP64 ((128 + 1024)*1024*1024UL)
#define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
#define MAX_GAP (TASK_SIZE/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)
{
	unsigned long rnd;

	/* 8MB for 32bit, 1GB for 64bit */
	if (is_32bit_task())
		rnd = get_random_long() % (1<<(23-PAGE_SHIFT));
	else
		rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT));

	return rnd << PAGE_SHIFT;
}

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;

	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
}

/*
 * 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 = TASK_UNMAPPED_BASE;
		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;
	}
}
Commit	Line	Data
1da177e4	1	/*
1da177e4 LT	2	* flexible mmap layout support
	3	*
	4	* Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
	5	* All Rights Reserved.
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License as published by
	9	* the Free Software Foundation; either version 2 of the License, or
	10	* (at your option) any later version.
	11	*
	12	* This program is distributed in the hope that it will be useful,
	13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	15	* GNU General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU General Public License
	18	* along with this program; if not, write to the Free Software
	19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	20	*
	21	*
	22	* Started by Ingo Molnar <mingo@elte.hu>
	23	*/
	24
	25	#include <linux/personality.h>
	26	#include <linux/mm.h>
9f14c42d	27	#include <linux/random.h>
e8edc6e0	28	#include <linux/sched.h>
1da177e4 LT	29
	30	/*
	31	* Top of mmap area (just below the process stack).
	32	*
002b0ec7 AB	33	* Leave at least a ~128 MB hole on 32bit applications.
	34	*
	35	* On 64bit applications we randomise the stack by 1GB so we need to
	36	* space our mmap start address by a further 1GB, otherwise there is a
	37	* chance the mmap area will end up closer to the stack than our ulimit
	38	* requires.
1da177e4	39	*/
002b0ec7 AB	40	#define MIN_GAP32 (12810241024)
	41	#define MIN_GAP64 ((128 + 1024)10241024UL)
	42	#define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
1da177e4 LT	43	#define MAX_GAP (TASK_SIZE/6*5)
1da177e4 LT	44
13a2cb36 AB	45	static inline int mmap_is_legacy(void)
	46	{
	47	if (current->personality & ADDR_COMPAT_LAYOUT)
	48	return 1;
	49
4bf936b9	50	if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
13a2cb36 AB	51	return 1;
	52
	53	return sysctl_legacy_va_layout;
	54	}
	55
2b68f6ca	56	unsigned long arch_mmap_rnd(void)
9f14c42d	57	{
ed632274 KC	58	unsigned long rnd;
	59
	60	/* 8MB for 32bit, 1GB for 64bit */
	61	if (is_32bit_task())
5ef11c35	62	rnd = get_random_long() % (1<<(23-PAGE_SHIFT));
ed632274	63	else
5ef11c35	64	rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT));
9f14c42d	65
fa8cbaaf	66	return rnd << PAGE_SHIFT;
9f14c42d AB	67	}
9f14c42d AB	68
ed632274	69	static inline unsigned long mmap_base(unsigned long rnd)
1da177e4	70	{
4bf936b9	71	unsigned long gap = rlimit(RLIMIT_STACK);
1da177e4 LT	72
	73	if (gap < MIN_GAP)
	74	gap = MIN_GAP;
	75	else if (gap > MAX_GAP)
	76	gap = MAX_GAP;
	77
ed632274	78	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
1da177e4 LT	79	}
1da177e4 LT	80
1da177e4 LT	81	/*
	82	* This function, called very early during the creation of a new
	83	* process VM image, sets up which VM layout function to use:
	84	*/
	85	void arch_pick_mmap_layout(struct mm_struct *mm)
	86	{
ed632274 KC	87	unsigned long random_factor = 0UL;
	88
	89	if (current->flags & PF_RANDOMIZE)
2b68f6ca	90	random_factor = arch_mmap_rnd();
ed632274	91
1da177e4 LT	92	/*
	93	* Fall back to the standard layout if the personality
	94	* bit is set, or if the expected stack growth is unlimited:
	95	*/
	96	if (mmap_is_legacy()) {
	97	mm->mmap_base = TASK_UNMAPPED_BASE;
	98	mm->get_unmapped_area = arch_get_unmapped_area;
1da177e4	99	} else {
ed632274	100	mm->mmap_base = mmap_base(random_factor);
1da177e4	101	mm->get_unmapped_area = arch_get_unmapped_area_topdown;
1da177e4 LT	102	}
1da177e4 LT	103	}