2 * Based on arch/arm/mm/mmap.c
4 * Copyright (C) 2012 ARM Ltd.
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.
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.
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/>.
19 #include <linux/elf.h>
22 #include <linux/mman.h>
23 #include <linux/export.h>
24 #include <linux/shm.h>
25 #include <linux/sched.h>
27 #include <linux/personality.h>
28 #include <linux/random.h>
30 #include <asm/cputype.h>
33 * Leave enough space between the mmap area and the stack to honour ulimit in
34 * the face of randomisation.
36 #define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1))
37 #define MAX_GAP (STACK_TOP/6*5)
39 static int mmap_is_legacy(void)
41 if (current->personality & ADDR_COMPAT_LAYOUT)
44 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
47 return sysctl_legacy_va_layout;
50 static unsigned long mmap_rnd(void)
52 unsigned long rnd = 0;
54 if (current->flags & PF_RANDOMIZE)
55 rnd = (long)get_random_int() & STACK_RND_MASK;
57 return rnd << PAGE_SHIFT;
60 static unsigned long mmap_base(void)
62 unsigned long gap = rlimit(RLIMIT_STACK);
66 else if (gap > MAX_GAP)
69 return PAGE_ALIGN(STACK_TOP - gap - mmap_rnd());
73 * This function, called very early during the creation of a new process VM
74 * image, sets up which VM layout function to use:
76 void arch_pick_mmap_layout(struct mm_struct *mm)
79 * Fall back to the standard layout if the personality bit is set, or
80 * if the expected stack growth is unlimited:
82 if (mmap_is_legacy()) {
83 mm->mmap_base = TASK_UNMAPPED_BASE;
84 mm->get_unmapped_area = arch_get_unmapped_area;
86 mm->mmap_base = mmap_base();
87 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
90 EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
94 * You really shouldn't be using read() or write() on /dev/mem. This might go
97 int valid_phys_addr_range(phys_addr_t addr, size_t size)
99 if (addr < PHYS_OFFSET)
101 if (addr + size > __pa(high_memory - 1) + 1)
108 * Do not allow /dev/mem mappings beyond the supported physical range.
110 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
112 return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
115 #ifdef CONFIG_STRICT_DEVMEM
117 #include <linux/ioport.h>
120 * devmem_is_allowed() checks to see if /dev/mem access to a certain address
121 * is valid. The argument is a physical page number. We mimic x86 here by
122 * disallowing access to system RAM as well as device-exclusive MMIO regions.
123 * This effectively disable read()/write() on /dev/mem.
125 int devmem_is_allowed(unsigned long pfn)
127 if (iomem_is_exclusive(pfn << PAGE_SHIFT))
129 if (!page_is_ram(pfn))