fa8cbaaf5a
Since commit8a0a9bd4db, this comment in mmap_rnd() does not hold true as the value returned by get_random_int() will in fact be different every single call. Remove the comment and simplify the code back to its original desired form. This reverts commita5adc91a4bwhich is no longer necessary and also fixes the sparc code that copied this same adjustment. Signed-off-by: Dan McGee <dpmcgee@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
101 lines
2.8 KiB
C
101 lines
2.8 KiB
C
/*
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* flexible mmap layout support
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*
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* Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*
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* Started by Ingo Molnar <mingo@elte.hu>
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*/
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#include <linux/personality.h>
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#include <linux/mm.h>
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#include <linux/random.h>
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#include <linux/sched.h>
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/*
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* Top of mmap area (just below the process stack).
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*
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* Leave at least a ~128 MB hole on 32bit applications.
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*
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* On 64bit applications we randomise the stack by 1GB so we need to
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* space our mmap start address by a further 1GB, otherwise there is a
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* chance the mmap area will end up closer to the stack than our ulimit
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* requires.
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*/
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#define MIN_GAP32 (128*1024*1024)
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#define MIN_GAP64 ((128 + 1024)*1024*1024UL)
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#define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
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#define MAX_GAP (TASK_SIZE/6*5)
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static inline int mmap_is_legacy(void)
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{
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if (current->personality & ADDR_COMPAT_LAYOUT)
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return 1;
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if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
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return 1;
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return sysctl_legacy_va_layout;
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}
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static unsigned long mmap_rnd(void)
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{
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unsigned long rnd = 0;
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if (current->flags & PF_RANDOMIZE) {
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/* 8MB for 32bit, 1GB for 64bit */
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if (is_32bit_task())
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rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
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else
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rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
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}
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return rnd << PAGE_SHIFT;
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}
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static inline unsigned long mmap_base(void)
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{
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unsigned long gap = rlimit(RLIMIT_STACK);
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if (gap < MIN_GAP)
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gap = MIN_GAP;
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else if (gap > MAX_GAP)
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gap = MAX_GAP;
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return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
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}
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/*
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* This function, called very early during the creation of a new
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* process VM image, sets up which VM layout function to use:
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*/
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void arch_pick_mmap_layout(struct mm_struct *mm)
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{
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/*
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* Fall back to the standard layout if the personality
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* bit is set, or if the expected stack growth is unlimited:
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*/
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if (mmap_is_legacy()) {
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mm->mmap_base = TASK_UNMAPPED_BASE;
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mm->get_unmapped_area = arch_get_unmapped_area;
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mm->unmap_area = arch_unmap_area;
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} else {
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mm->mmap_base = mmap_base();
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mm->get_unmapped_area = arch_get_unmapped_area_topdown;
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mm->unmap_area = arch_unmap_area_topdown;
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}
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}
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