243 lines
6.2 KiB
C
243 lines
6.2 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/signal.h>
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#include <linux/sched/mm.h>
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#include <linux/elf-randomize.h>
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#include <linux/security.h>
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#include <linux/mman.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.
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*/
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#define MIN_GAP (128*1024*1024)
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#define MAX_GAP (TASK_SIZE/6*5)
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static inline int mmap_is_legacy(struct rlimit *rlim_stack)
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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 (rlim_stack->rlim_cur == 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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unsigned long shift, rnd;
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shift = mmap_rnd_bits;
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#ifdef CONFIG_COMPAT
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if (is_32bit_task())
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shift = mmap_rnd_compat_bits;
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#endif
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rnd = get_random_long() % (1ul << shift);
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return rnd << PAGE_SHIFT;
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}
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static inline 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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/* 8MB for 32bit, 1GB for 64bit */
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if (is_32bit_task())
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return (1<<23);
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else
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return (1<<30);
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}
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static inline unsigned long mmap_base(unsigned long rnd,
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struct rlimit *rlim_stack)
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{
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unsigned long gap = rlim_stack->rlim_cur;
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unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
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/* Values close to RLIM_INFINITY can overflow. */
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if (gap + pad > gap)
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gap += pad;
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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(DEFAULT_MAP_WINDOW - gap - rnd);
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}
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#ifdef CONFIG_PPC_RADIX_MMU
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/*
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* Same function as generic code used only for radix, because we don't need to overload
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* the generic one. But we will have to duplicate, because hash select
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* HAVE_ARCH_UNMAPPED_AREA
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*/
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static unsigned long
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radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
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unsigned long len, unsigned long pgoff,
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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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int fixed = (flags & MAP_FIXED);
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unsigned long high_limit;
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struct vm_unmapped_area_info info;
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high_limit = DEFAULT_MAP_WINDOW;
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if (addr >= high_limit || (fixed && (addr + len > high_limit)))
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high_limit = TASK_SIZE;
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if (len > high_limit)
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return -ENOMEM;
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if (fixed) {
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if (addr > high_limit - len)
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return -ENOMEM;
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return addr;
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}
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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 (high_limit - len >= addr && addr >= mmap_min_addr &&
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(!vma || addr + len <= vm_start_gap(vma)))
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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 = high_limit;
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info.align_mask = 0;
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return vm_unmapped_area(&info);
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}
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static unsigned long
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radix__arch_get_unmapped_area_topdown(struct file *filp,
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const unsigned long addr0,
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const unsigned long len,
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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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int fixed = (flags & MAP_FIXED);
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unsigned long high_limit;
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struct vm_unmapped_area_info info;
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high_limit = DEFAULT_MAP_WINDOW;
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if (addr >= high_limit || (fixed && (addr + len > high_limit)))
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high_limit = TASK_SIZE;
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if (len > high_limit)
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return -ENOMEM;
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if (fixed) {
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if (addr > high_limit - len)
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return -ENOMEM;
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return addr;
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}
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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 (high_limit - len >= addr && addr >= mmap_min_addr &&
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(!vma || addr + len <= vm_start_gap(vma)))
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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 + (high_limit - DEFAULT_MAP_WINDOW);
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info.align_mask = 0;
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addr = vm_unmapped_area(&info);
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if (!(addr & ~PAGE_MASK))
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return addr;
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VM_BUG_ON(addr != -ENOMEM);
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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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return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
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}
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static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
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unsigned long random_factor,
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struct rlimit *rlim_stack)
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{
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if (mmap_is_legacy(rlim_stack)) {
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mm->mmap_base = TASK_UNMAPPED_BASE;
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mm->get_unmapped_area = radix__arch_get_unmapped_area;
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} else {
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mm->mmap_base = mmap_base(random_factor, rlim_stack);
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mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
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}
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}
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#else
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/* dummy */
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extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,
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unsigned long random_factor,
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struct rlimit *rlim_stack);
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#endif
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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, struct rlimit *rlim_stack)
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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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if (radix_enabled())
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return radix__arch_pick_mmap_layout(mm, random_factor,
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rlim_stack);
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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(rlim_stack)) {
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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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} else {
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mm->mmap_base = mmap_base(random_factor, rlim_stack);
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mm->get_unmapped_area = arch_get_unmapped_area_topdown;
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}
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}
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