mirror of
https://github.com/torvalds/linux.git
synced 2024-12-22 19:01:37 +00:00
d6c763afab
Since commit8a0a9bd4db('random: make get_random_int() more random'), get_random_int() returns a random value for each call, so comment and hack introduced in mmap_rnd() as part of commit1d18c47c73('arm64: MMU fault handling and page table management') are incorrects. Commit1d18c47c73seems to use the same hack introduced by commita5adc91a4b('powerpc: Ensure random space between stack and mmaps'), latter copied in commit5a0efea09f('sparc64: Sharpen address space randomization calculations.'). But both architectures were cleaned up as part of commitfa8cbaaf5a('powerpc+sparc64/mm: Remove hack in mmap randomize layout') as hack is no more needed since commit8a0a9bd4db. So the present patch removes the comment and the hack around get_random_int() on AArch64's mmap_rnd(). Cc: David S. Miller <davem@davemloft.net> Cc: Anton Blanchard <anton@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Dan McGee <dpmcgee@gmail.com> Signed-off-by: Yann Droneaud <ydroneaud@opteya.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
135 lines
3.2 KiB
C
135 lines
3.2 KiB
C
/*
|
|
* Based on arch/arm/mm/mmap.c
|
|
*
|
|
* Copyright (C) 2012 ARM Ltd.
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <linux/elf.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/mman.h>
|
|
#include <linux/export.h>
|
|
#include <linux/shm.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/io.h>
|
|
#include <linux/personality.h>
|
|
#include <linux/random.h>
|
|
|
|
#include <asm/cputype.h>
|
|
|
|
/*
|
|
* Leave enough space between the mmap area and the stack to honour ulimit in
|
|
* the face of randomisation.
|
|
*/
|
|
#define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1))
|
|
#define MAX_GAP (STACK_TOP/6*5)
|
|
|
|
static int mmap_is_legacy(void)
|
|
{
|
|
if (current->personality & ADDR_COMPAT_LAYOUT)
|
|
return 1;
|
|
|
|
if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
|
|
return 1;
|
|
|
|
return sysctl_legacy_va_layout;
|
|
}
|
|
|
|
static unsigned long mmap_rnd(void)
|
|
{
|
|
unsigned long rnd = 0;
|
|
|
|
if (current->flags & PF_RANDOMIZE)
|
|
rnd = (long)get_random_int() & STACK_RND_MASK;
|
|
|
|
return rnd << PAGE_SHIFT;
|
|
}
|
|
|
|
static unsigned long mmap_base(void)
|
|
{
|
|
unsigned long gap = rlimit(RLIMIT_STACK);
|
|
|
|
if (gap < MIN_GAP)
|
|
gap = MIN_GAP;
|
|
else if (gap > MAX_GAP)
|
|
gap = MAX_GAP;
|
|
|
|
return PAGE_ALIGN(STACK_TOP - gap - mmap_rnd());
|
|
}
|
|
|
|
/*
|
|
* This function, called very early during the creation of a new process VM
|
|
* image, sets up which VM layout function to use:
|
|
*/
|
|
void arch_pick_mmap_layout(struct mm_struct *mm)
|
|
{
|
|
/*
|
|
* Fall back to the standard layout if the personality bit is set, or
|
|
* if the expected stack growth is unlimited:
|
|
*/
|
|
if (mmap_is_legacy()) {
|
|
mm->mmap_base = TASK_UNMAPPED_BASE;
|
|
mm->get_unmapped_area = arch_get_unmapped_area;
|
|
} else {
|
|
mm->mmap_base = mmap_base();
|
|
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
|
|
|
|
|
|
/*
|
|
* You really shouldn't be using read() or write() on /dev/mem. This might go
|
|
* away in the future.
|
|
*/
|
|
int valid_phys_addr_range(phys_addr_t addr, size_t size)
|
|
{
|
|
if (addr < PHYS_OFFSET)
|
|
return 0;
|
|
if (addr + size > __pa(high_memory - 1) + 1)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Do not allow /dev/mem mappings beyond the supported physical range.
|
|
*/
|
|
int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
|
|
{
|
|
return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
|
|
}
|
|
|
|
#ifdef CONFIG_STRICT_DEVMEM
|
|
|
|
#include <linux/ioport.h>
|
|
|
|
/*
|
|
* devmem_is_allowed() checks to see if /dev/mem access to a certain address
|
|
* is valid. The argument is a physical page number. We mimic x86 here by
|
|
* disallowing access to system RAM as well as device-exclusive MMIO regions.
|
|
* This effectively disable read()/write() on /dev/mem.
|
|
*/
|
|
int devmem_is_allowed(unsigned long pfn)
|
|
{
|
|
if (iomem_is_exclusive(pfn << PAGE_SHIFT))
|
|
return 0;
|
|
if (!page_is_ram(pfn))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
#endif
|