Catalin Marinas | 1d18c47 | 2012-03-05 11:49:27 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Based on arch/arm/mm/mmap.c |
| 3 | * |
| 4 | * Copyright (C) 2012 ARM Ltd. |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License version 2 as |
| 8 | * published by the Free Software Foundation. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
| 14 | * |
| 15 | * You should have received a copy of the GNU General Public License |
| 16 | * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 17 | */ |
| 18 | |
| 19 | #include <linux/elf.h> |
| 20 | #include <linux/fs.h> |
| 21 | #include <linux/mm.h> |
| 22 | #include <linux/mman.h> |
| 23 | #include <linux/export.h> |
| 24 | #include <linux/shm.h> |
| 25 | #include <linux/sched.h> |
| 26 | #include <linux/io.h> |
| 27 | #include <linux/personality.h> |
| 28 | #include <linux/random.h> |
| 29 | |
| 30 | #include <asm/cputype.h> |
| 31 | |
| 32 | /* |
| 33 | * Leave enough space between the mmap area and the stack to honour ulimit in |
| 34 | * the face of randomisation. |
| 35 | */ |
| 36 | #define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1)) |
| 37 | #define MAX_GAP (STACK_TOP/6*5) |
| 38 | |
| 39 | static int mmap_is_legacy(void) |
| 40 | { |
| 41 | if (current->personality & ADDR_COMPAT_LAYOUT) |
| 42 | return 1; |
| 43 | |
| 44 | if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) |
| 45 | return 1; |
| 46 | |
| 47 | return sysctl_legacy_va_layout; |
| 48 | } |
| 49 | |
| 50 | /* |
| 51 | * Since get_random_int() returns the same value within a 1 jiffy window, we |
| 52 | * will almost always get the same randomisation for the stack and mmap |
| 53 | * region. This will mean the relative distance between stack and mmap will be |
| 54 | * the same. |
| 55 | * |
| 56 | * To avoid this we can shift the randomness by 1 bit. |
| 57 | */ |
| 58 | static unsigned long mmap_rnd(void) |
| 59 | { |
| 60 | unsigned long rnd = 0; |
| 61 | |
| 62 | if (current->flags & PF_RANDOMIZE) |
| 63 | rnd = (long)get_random_int() & (STACK_RND_MASK >> 1); |
| 64 | |
| 65 | return rnd << (PAGE_SHIFT + 1); |
| 66 | } |
| 67 | |
| 68 | static unsigned long mmap_base(void) |
| 69 | { |
| 70 | unsigned long gap = rlimit(RLIMIT_STACK); |
| 71 | |
| 72 | if (gap < MIN_GAP) |
| 73 | gap = MIN_GAP; |
| 74 | else if (gap > MAX_GAP) |
| 75 | gap = MAX_GAP; |
| 76 | |
| 77 | return PAGE_ALIGN(STACK_TOP - gap - mmap_rnd()); |
| 78 | } |
| 79 | |
| 80 | /* |
| 81 | * This function, called very early during the creation of a new process VM |
| 82 | * image, sets up which VM layout function to use: |
| 83 | */ |
| 84 | void arch_pick_mmap_layout(struct mm_struct *mm) |
| 85 | { |
| 86 | /* |
| 87 | * Fall back to the standard layout if the personality bit is set, or |
| 88 | * if the expected stack growth is unlimited: |
| 89 | */ |
| 90 | if (mmap_is_legacy()) { |
| 91 | mm->mmap_base = TASK_UNMAPPED_BASE; |
| 92 | mm->get_unmapped_area = arch_get_unmapped_area; |
| 93 | mm->unmap_area = arch_unmap_area; |
| 94 | } else { |
| 95 | mm->mmap_base = mmap_base(); |
| 96 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
| 97 | mm->unmap_area = arch_unmap_area_topdown; |
| 98 | } |
| 99 | } |
| 100 | EXPORT_SYMBOL_GPL(arch_pick_mmap_layout); |
| 101 | |
| 102 | |
| 103 | /* |
| 104 | * You really shouldn't be using read() or write() on /dev/mem. This might go |
| 105 | * away in the future. |
| 106 | */ |
| 107 | int valid_phys_addr_range(unsigned long addr, size_t size) |
| 108 | { |
| 109 | if (addr < PHYS_OFFSET) |
| 110 | return 0; |
| 111 | if (addr + size > __pa(high_memory - 1) + 1) |
| 112 | return 0; |
| 113 | |
| 114 | return 1; |
| 115 | } |
| 116 | |
| 117 | /* |
| 118 | * Do not allow /dev/mem mappings beyond the supported physical range. |
| 119 | */ |
| 120 | int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) |
| 121 | { |
| 122 | return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK); |
| 123 | } |
| 124 | |
| 125 | #ifdef CONFIG_STRICT_DEVMEM |
| 126 | |
| 127 | #include <linux/ioport.h> |
| 128 | |
| 129 | /* |
| 130 | * devmem_is_allowed() checks to see if /dev/mem access to a certain address |
| 131 | * is valid. The argument is a physical page number. We mimic x86 here by |
| 132 | * disallowing access to system RAM as well as device-exclusive MMIO regions. |
| 133 | * This effectively disable read()/write() on /dev/mem. |
| 134 | */ |
| 135 | int devmem_is_allowed(unsigned long pfn) |
| 136 | { |
| 137 | if (iomem_is_exclusive(pfn << PAGE_SHIFT)) |
| 138 | return 0; |
| 139 | if (!page_is_ram(pfn)) |
| 140 | return 1; |
| 141 | return 0; |
| 142 | } |
| 143 | |
| 144 | #endif |