250 lines
6.5 KiB
C
250 lines
6.5 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/elf-randomize.h>
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#include <linux/personality.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/mm.h>
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#include <linux/random.h>
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#include <linux/compat.h>
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#include <linux/security.h>
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#include <asm/pgalloc.h>
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#include <asm/elf.h>
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static unsigned long stack_maxrandom_size(void)
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{
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if (!(current->flags & PF_RANDOMIZE))
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return 0;
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if (current->personality & ADDR_NO_RANDOMIZE)
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return 0;
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return STACK_RND_MASK << PAGE_SHIFT;
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}
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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 ~32 MB hole.
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*/
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#define MIN_GAP (32*1024*1024)
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#define MAX_GAP (STACK_TOP/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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unsigned long arch_mmap_rnd(void)
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{
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return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
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}
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static unsigned long mmap_base_legacy(unsigned long rnd)
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{
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return TASK_UNMAPPED_BASE + rnd;
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}
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static inline unsigned long mmap_base(unsigned long rnd)
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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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gap &= PAGE_MASK;
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return STACK_TOP - stack_maxrandom_size() - rnd - gap;
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}
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unsigned long
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arch_get_unmapped_area(struct file *filp, unsigned long addr,
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unsigned long len, unsigned long pgoff, unsigned long flags)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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struct vm_unmapped_area_info info;
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if (len > TASK_SIZE - mmap_min_addr)
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return -ENOMEM;
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if (flags & MAP_FIXED)
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return addr;
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if (addr) {
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addr = PAGE_ALIGN(addr);
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vma = find_vma(mm, addr);
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if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
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(!vma || addr + len <= vma->vm_start))
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return addr;
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}
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info.flags = 0;
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info.length = len;
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info.low_limit = mm->mmap_base;
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info.high_limit = TASK_SIZE;
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if (filp || (flags & MAP_SHARED))
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info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
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else
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info.align_mask = 0;
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info.align_offset = pgoff << PAGE_SHIFT;
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return vm_unmapped_area(&info);
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}
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unsigned long
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arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
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const unsigned long len, const unsigned long pgoff,
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const unsigned long flags)
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{
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struct vm_area_struct *vma;
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struct mm_struct *mm = current->mm;
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unsigned long addr = addr0;
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struct vm_unmapped_area_info info;
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/* requested length too big for entire address space */
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if (len > TASK_SIZE - mmap_min_addr)
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return -ENOMEM;
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if (flags & MAP_FIXED)
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return addr;
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/* requesting a specific address */
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if (addr) {
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addr = PAGE_ALIGN(addr);
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vma = find_vma(mm, addr);
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if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
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(!vma || addr + len <= vma->vm_start))
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return addr;
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}
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info.flags = VM_UNMAPPED_AREA_TOPDOWN;
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info.length = len;
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info.low_limit = max(PAGE_SIZE, mmap_min_addr);
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info.high_limit = mm->mmap_base;
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if (filp || (flags & MAP_SHARED))
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info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
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else
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info.align_mask = 0;
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info.align_offset = pgoff << PAGE_SHIFT;
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addr = vm_unmapped_area(&info);
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/*
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* A failed mmap() very likely causes application failure,
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* so fall back to the bottom-up function here. This scenario
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* can happen with large stack limits and large mmap()
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* allocations.
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*/
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if (addr & ~PAGE_MASK) {
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VM_BUG_ON(addr != -ENOMEM);
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info.flags = 0;
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info.low_limit = TASK_UNMAPPED_BASE;
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info.high_limit = TASK_SIZE;
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addr = vm_unmapped_area(&info);
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}
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return addr;
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}
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int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
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{
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if (is_compat_task() || TASK_SIZE >= TASK_MAX_SIZE)
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return 0;
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if (!(flags & MAP_FIXED))
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addr = 0;
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if ((addr + len) >= TASK_SIZE)
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return crst_table_upgrade(current->mm);
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return 0;
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}
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static unsigned long
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s390_get_unmapped_area(struct file *filp, unsigned long addr,
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unsigned long len, unsigned long pgoff, unsigned long flags)
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{
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struct mm_struct *mm = current->mm;
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unsigned long area;
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int rc;
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area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
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if (!(area & ~PAGE_MASK))
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return area;
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if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
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/* Upgrade the page table to 4 levels and retry. */
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rc = crst_table_upgrade(mm);
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if (rc)
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return (unsigned long) rc;
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area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
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}
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return area;
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}
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static unsigned long
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s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
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const unsigned long len, const unsigned long pgoff,
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const unsigned long flags)
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{
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struct mm_struct *mm = current->mm;
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unsigned long area;
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int rc;
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area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
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if (!(area & ~PAGE_MASK))
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return area;
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if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
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/* Upgrade the page table to 4 levels and retry. */
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rc = crst_table_upgrade(mm);
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if (rc)
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return (unsigned long) rc;
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area = arch_get_unmapped_area_topdown(filp, addr, len,
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pgoff, flags);
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}
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return area;
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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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unsigned long random_factor = 0UL;
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if (current->flags & PF_RANDOMIZE)
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random_factor = arch_mmap_rnd();
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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 = mmap_base_legacy(random_factor);
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mm->get_unmapped_area = s390_get_unmapped_area;
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} else {
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mm->mmap_base = mmap_base(random_factor);
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mm->get_unmapped_area = s390_get_unmapped_area_topdown;
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}
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}
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