[GitHub/mt8127/android_kernel_alcatel_ttab.git] / arch / x86 / mm / mmap.c

/*
 * Flexible mmap layout support
 *
 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
 * as follows:
 *
 * Copyright 2003-2009 Red Hat Inc.
 * All Rights Reserved.
 * Copyright 2005 Andi Kleen, SUSE Labs.
 * Copyright 2007 Jiri Kosina, SUSE Labs.
 *
 * 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
 */

#include <linux/personality.h>
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/limits.h>
#include <linux/sched.h>
#include <asm/elf.h>

static unsigned int stack_maxrandom_size(void)
{
	unsigned int max = 0;
	if ((current->flags & PF_RANDOMIZE) &&
		!(current->personality & ADDR_NO_RANDOMIZE)) {
		max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT;
	}

	return max;
}


/*
 * Top of mmap area (just below the process stack).
 *
 * Leave an at least ~128 MB hole with possible stack randomization.
 */
#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
#define MAX_GAP (TASK_SIZE/6*5)

/*
 * True on X86_32 or when emulating IA32 on X86_64
 */
static int mmap_is_ia32(void)
{
#ifdef CONFIG_X86_32
	return 1;
#endif
#ifdef CONFIG_IA32_EMULATION
	if (test_thread_flag(TIF_IA32))
		return 1;
#endif
	return 0;
}

static 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;
}

static unsigned long mmap_rnd(void)
{
	unsigned long rnd = 0;

	/*
	*  8 bits of randomness in 32bit mmaps, 20 address space bits
	* 28 bits of randomness in 64bit mmaps, 40 address space bits
	*/
	if (current->flags & PF_RANDOMIZE) {
		if (mmap_is_ia32())
			rnd = (long)get_random_int() % (1<<8);
		else
			rnd = (long)(get_random_int() % (1<<28));
	}
	return rnd << PAGE_SHIFT;
}

static 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());
}

/*
 * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
 * does, but not when emulating X86_32
 */
static unsigned long mmap_legacy_base(void)
{
	if (mmap_is_ia32())
		return TASK_UNMAPPED_BASE;
	else
		return TASK_UNMAPPED_BASE + 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)
{
	if (mmap_is_legacy()) {
		mm->mmap_base = mmap_legacy_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
cc503c1b	1	/*
675a0813	2	* Flexible mmap layout support
cc503c1b JK	3	*
	4	* Based on code by Ingo Molnar and Andi Kleen, copyrighted
	5	* as follows:
	6	*
8f47e163	7	* Copyright 2003-2009 Red Hat Inc.
cc503c1b JK	8	* All Rights Reserved.
	9	* Copyright 2005 Andi Kleen, SUSE Labs.
	10	* Copyright 2007 Jiri Kosina, SUSE Labs.
	11	*
	12	* This program is free software; you can redistribute it and/or modify
	13	* it under the terms of the GNU General Public License as published by
	14	* the Free Software Foundation; either version 2 of the License, or
	15	* (at your option) any later version.
	16	*
	17	* This program is distributed in the hope that it will be useful,
	18	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	19	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	20	* GNU General Public License for more details.
	21	*
	22	* You should have received a copy of the GNU General Public License
	23	* along with this program; if not, write to the Free Software
	24	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
8817210d	25	*/
cc503c1b JK	26
cc503c1b JK	27	#include <linux/personality.h>
8817210d	28	#include <linux/mm.h>
8817210d	29	#include <linux/random.h>
cc503c1b JK	30	#include <linux/limits.h>
cc503c1b JK	31	#include <linux/sched.h>
80938332 MH	32	#include <asm/elf.h>
	33
	34	static unsigned int stack_maxrandom_size(void)
	35	{
	36	unsigned int max = 0;
	37	if ((current->flags & PF_RANDOMIZE) &&
	38	!(current->personality & ADDR_NO_RANDOMIZE)) {
	39	max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT;
	40	}
	41
	42	return max;
	43	}
	44
8817210d	45
cc503c1b JK	46	/*
	47	* Top of mmap area (just below the process stack).
	48	*
80938332	49	* Leave an at least ~128 MB hole with possible stack randomization.
cc503c1b	50	*/
80938332	51	#define MIN_GAP (12810241024UL + stack_maxrandom_size())
cc503c1b	52	#define MAX_GAP (TASK_SIZE/6*5)
8817210d	53
675a0813 HH	54	/*
	55	* True on X86_32 or when emulating IA32 on X86_64
	56	*/
	57	static int mmap_is_ia32(void)
8817210d	58	{
675a0813 HH	59	#ifdef CONFIG_X86_32
	60	return 1;
	61	#endif
8817210d	62	#ifdef CONFIG_IA32_EMULATION
cc503c1b JK	63	if (test_thread_flag(TIF_IA32))
cc503c1b JK	64	return 1;
8817210d	65	#endif
cc503c1b JK	66	return 0;
	67	}
	68
954683a2	69	static int mmap_is_legacy(void)
cc503c1b JK	70	{
	71	if (current->personality & ADDR_COMPAT_LAYOUT)
	72	return 1;
	73
	74	if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
	75	return 1;
	76
	77	return sysctl_legacy_va_layout;
	78	}
	79
675a0813 HH	80	static unsigned long mmap_rnd(void)
	81	{
	82	unsigned long rnd = 0;
	83
	84	/*
	85	* 8 bits of randomness in 32bit mmaps, 20 address space bits
	86	* 28 bits of randomness in 64bit mmaps, 40 address space bits
	87	*/
	88	if (current->flags & PF_RANDOMIZE) {
	89	if (mmap_is_ia32())
	90	rnd = (long)get_random_int() % (1<<8);
	91	else
	92	rnd = (long)(get_random_int() % (1<<28));
	93	}
	94	return rnd << PAGE_SHIFT;
	95	}
	96
	97	static unsigned long mmap_base(void)
	98	{
	99	unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
	100
	101	if (gap < MIN_GAP)
	102	gap = MIN_GAP;
	103	else if (gap > MAX_GAP)
	104	gap = MAX_GAP;
	105
	106	return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
	107	}
	108
	109	/*
	110	* Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
	111	* does, but not when emulating X86_32
	112	*/
	113	static unsigned long mmap_legacy_base(void)
	114	{
	115	if (mmap_is_ia32())
	116	return TASK_UNMAPPED_BASE;
	117	else
	118	return TASK_UNMAPPED_BASE + mmap_rnd();
	119	}
	120
cc503c1b JK	121	/*
	122	* This function, called very early during the creation of a new
	123	* process VM image, sets up which VM layout function to use:
	124	*/
	125	void arch_pick_mmap_layout(struct mm_struct *mm)
	126	{
675a0813 HH	127	if (mmap_is_legacy()) {
675a0813 HH	128	mm->mmap_base = mmap_legacy_base();
cc503c1b JK	129	mm->get_unmapped_area = arch_get_unmapped_area;
	130	mm->unmap_area = arch_unmap_area;
	131	} else {
	132	mm->mmap_base = mmap_base();
	133	mm->get_unmapped_area = arch_get_unmapped_area_topdown;
	134	mm->unmap_area = arch_unmap_area_topdown;
cc503c1b	135	}
8817210d	136	}