1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Based on arch/arm/mm/mmap.c 4 * 5 * Copyright (C) 2012 ARM Ltd. 6 */ 7 8 #include <linux/elf.h> 9 #include <linux/fs.h> 10 #include <linux/memblock.h> 11 #include <linux/mm.h> 12 #include <linux/mman.h> 13 #include <linux/export.h> 14 #include <linux/shm.h> 15 #include <linux/sched/signal.h> 16 #include <linux/sched/mm.h> 17 #include <linux/io.h> 18 #include <linux/personality.h> 19 #include <linux/random.h> 20 21 #include <asm/cputype.h> 22 23 /* 24 * You really shouldn't be using read() or write() on /dev/mem. This might go 25 * away in the future. 26 */ 27 int valid_phys_addr_range(phys_addr_t addr, size_t size) 28 { 29 /* 30 * Check whether addr is covered by a memory region without the 31 * MEMBLOCK_NOMAP attribute, and whether that region covers the 32 * entire range. In theory, this could lead to false negatives 33 * if the range is covered by distinct but adjacent memory regions 34 * that only differ in other attributes. However, few of such 35 * attributes have been defined, and it is debatable whether it 36 * follows that /dev/mem read() calls should be able traverse 37 * such boundaries. 38 */ 39 return memblock_is_region_memory(addr, size) && 40 memblock_is_map_memory(addr); 41 } 42 43 /* 44 * Do not allow /dev/mem mappings beyond the supported physical range. 45 */ 46 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) 47 { 48 return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK); 49 } 50 51 #ifdef CONFIG_STRICT_DEVMEM 52 53 #include <linux/ioport.h> 54 55 /* 56 * devmem_is_allowed() checks to see if /dev/mem access to a certain address 57 * is valid. The argument is a physical page number. We mimic x86 here by 58 * disallowing access to system RAM as well as device-exclusive MMIO regions. 59 * This effectively disable read()/write() on /dev/mem. 60 */ 61 int devmem_is_allowed(unsigned long pfn) 62 { 63 if (iomem_is_exclusive(pfn << PAGE_SHIFT)) 64 return 0; 65 if (!page_is_ram(pfn)) 66 return 1; 67 return 0; 68 } 69 70 #endif 71