[linux-2.6-block.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 an at least ~128 MB hole.
 */
#define MIN_GAP (128*1024*1024)
#define MAX_GAP (TASK_SIZE/6*5)

static inline int mmap_is_legacy(void)
{
	if (current->personality & ADDR_COMPAT_LAYOUT)
		return 1;

	if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
		return 1;

	return sysctl_legacy_va_layout;
}

/*
 * Since get_random_int() returns the same value within a 1 jiffy window,
 * we will almost always get the same randomisation for the stack and mmap
 * region. This will mean the relative distance between stack and mmap will
 * be the same.
 *
 * To avoid this we can shift the randomness by 1 bit.
 */
static unsigned long mmap_rnd(void)
{
	unsigned long rnd = 0;

	if (current->flags & PF_RANDOMIZE) {
		/* 8MB for 32bit, 1GB for 64bit */
		if (is_32bit_task())
			rnd = (long)(get_random_int() % (1<<(22-PAGE_SHIFT)));
		else
			rnd = (long)(get_random_int() % (1<<(29-PAGE_SHIFT)));
	}
	return (rnd << PAGE_SHIFT) * 2;
}

static inline unsigned long mmap_base(void)
{
	unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;

	if (gap < MIN_GAP)
		gap = MIN_GAP;
	else if (gap > MAX_GAP)
		gap = MAX_GAP;

	return PAGE_ALIGN(TASK_SIZE - gap - mmap_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)
{
	/*
	 * 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;
	}
}
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	*
	33	* Leave an at least ~128 MB hole.
	34	*/
	35	#define MIN_GAP (12810241024)
	36	#define MAX_GAP (TASK_SIZE/6*5)
	37
13a2cb36 AB	38	static inline int mmap_is_legacy(void)
	39	{
	40	if (current->personality & ADDR_COMPAT_LAYOUT)
	41	return 1;
	42
	43	if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
	44	return 1;
	45
	46	return sysctl_legacy_va_layout;
	47	}
	48
a5adc91a AB	49	/*
	50	* Since get_random_int() returns the same value within a 1 jiffy window,
	51	* we will almost always get the same randomisation for the stack and mmap
	52	* region. This will mean the relative distance between stack and mmap will
	53	* be the same.
	54	*
	55	* To avoid this we can shift the randomness by 1 bit.
	56	*/
9f14c42d AB	57	static unsigned long mmap_rnd(void)
	58	{
	59	unsigned long rnd = 0;
	60
	61	if (current->flags & PF_RANDOMIZE) {
	62	/* 8MB for 32bit, 1GB for 64bit */
	63	if (is_32bit_task())
a5adc91a	64	rnd = (long)(get_random_int() % (1<<(22-PAGE_SHIFT)));
9f14c42d	65	else
a5adc91a	66	rnd = (long)(get_random_int() % (1<<(29-PAGE_SHIFT)));
9f14c42d	67	}
a5adc91a	68	return (rnd << PAGE_SHIFT) * 2;
9f14c42d AB	69	}
9f14c42d AB	70
1da177e4 LT	71	static inline unsigned long mmap_base(void)
	72	{
	73	unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
	74
	75	if (gap < MIN_GAP)
	76	gap = MIN_GAP;
	77	else if (gap > MAX_GAP)
	78	gap = MAX_GAP;
	79
9f14c42d	80	return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
1da177e4 LT	81	}
1da177e4 LT	82
1da177e4 LT	83	/*
	84	* This function, called very early during the creation of a new
	85	* process VM image, sets up which VM layout function to use:
	86	*/
	87	void arch_pick_mmap_layout(struct mm_struct *mm)
	88	{
	89	/*
	90	* Fall back to the standard layout if the personality
	91	* bit is set, or if the expected stack growth is unlimited:
	92	*/
	93	if (mmap_is_legacy()) {
	94	mm->mmap_base = TASK_UNMAPPED_BASE;
	95	mm->get_unmapped_area = arch_get_unmapped_area;
	96	mm->unmap_area = arch_unmap_area;
	97	} else {
	98	mm->mmap_base = mmap_base();
	99	mm->get_unmapped_area = arch_get_unmapped_area_topdown;
	100	mm->unmap_area = arch_unmap_area_topdown;
	101	}
	102	}