mirror of https://gitee.com/openkylin/linux.git
125 lines
3.1 KiB
C
125 lines
3.1 KiB
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>
|
|
|
|
struct va_alignment __read_mostly va_align = {
|
|
.flags = -1,
|
|
};
|
|
|
|
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)
|
|
|
|
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_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 = get_random_int() % (1<<8);
|
|
else
|
|
rnd = get_random_int() % (1<<28);
|
|
}
|
|
return rnd << PAGE_SHIFT;
|
|
}
|
|
|
|
static 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;
|
|
|
|
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)
|
|
{
|
|
mm->mmap_legacy_base = mmap_legacy_base();
|
|
mm->mmap_base = mmap_base();
|
|
|
|
if (mmap_is_legacy()) {
|
|
mm->mmap_base = mm->mmap_legacy_base;
|
|
mm->get_unmapped_area = arch_get_unmapped_area;
|
|
} else {
|
|
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
|
|
}
|
|
}
|