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 mmap_is_legacy(void)39static 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 mmap_rnd(void)50static unsigned long mmap_rnd(void) 51 { 52 unsigned long rnd = 0; 53 54 if (current->flags & PF_RANDOMIZE) { 55 #ifdef CONFIG_COMPAT 56 if (test_thread_flag(TIF_32BIT)) 57 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); 58 else 59 #endif 60 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); 61 } 62 return rnd << PAGE_SHIFT; 63 } 64 mmap_base(void)65static unsigned long mmap_base(void) 66 { 67 unsigned long gap = rlimit(RLIMIT_STACK); 68 69 if (gap < MIN_GAP) 70 gap = MIN_GAP; 71 else if (gap > MAX_GAP) 72 gap = MAX_GAP; 73 74 return PAGE_ALIGN(STACK_TOP - gap - mmap_rnd()); 75 } 76 77 /* 78 * This function, called very early during the creation of a new process VM 79 * image, sets up which VM layout function to use: 80 */ arch_pick_mmap_layout(struct mm_struct * mm)81void arch_pick_mmap_layout(struct mm_struct *mm) 82 { 83 /* 84 * Fall back to the standard layout if the personality bit is set, or 85 * if the expected stack growth is unlimited: 86 */ 87 if (mmap_is_legacy()) { 88 mm->mmap_base = TASK_UNMAPPED_BASE; 89 mm->get_unmapped_area = arch_get_unmapped_area; 90 } else { 91 mm->mmap_base = mmap_base(); 92 mm->get_unmapped_area = arch_get_unmapped_area_topdown; 93 } 94 } 95 EXPORT_SYMBOL_GPL(arch_pick_mmap_layout); 96 97 98 /* 99 * You really shouldn't be using read() or write() on /dev/mem. This might go 100 * away in the future. 101 */ valid_phys_addr_range(phys_addr_t addr,size_t size)102int valid_phys_addr_range(phys_addr_t addr, size_t size) 103 { 104 if (addr < PHYS_OFFSET) 105 return 0; 106 if (addr + size > __pa(high_memory - 1) + 1) 107 return 0; 108 109 return 1; 110 } 111 112 /* 113 * Do not allow /dev/mem mappings beyond the supported physical range. 114 */ valid_mmap_phys_addr_range(unsigned long pfn,size_t size)115int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) 116 { 117 return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK); 118 } 119 120 #ifdef CONFIG_STRICT_DEVMEM 121 122 #include <linux/ioport.h> 123 124 /* 125 * devmem_is_allowed() checks to see if /dev/mem access to a certain address 126 * is valid. The argument is a physical page number. We mimic x86 here by 127 * disallowing access to system RAM as well as device-exclusive MMIO regions. 128 * This effectively disable read()/write() on /dev/mem. 129 */ devmem_is_allowed(unsigned long pfn)130int devmem_is_allowed(unsigned long pfn) 131 { 132 if (iomem_is_exclusive(pfn << PAGE_SHIFT)) 133 return 0; 134 if (!page_is_ram(pfn)) 135 return 1; 136 return 0; 137 } 138 139 #endif 140