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228 lines
5.5 KiB
228 lines
5.5 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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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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* Started by Ingo Molnar <[email protected]> |
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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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