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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* flexible mmap layout support
*
* Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
* All Rights Reserved.
*
* Started by Ingo Molnar <mingo@elte.hu>
*/
#include <linux/personality.h>
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/elf-randomize.h>
#include <linux/security.h>
#include <linux/mman.h>
/*
* Top of mmap area (just below the process stack).
*
* Leave at least a ~128 MB hole.
*/
#define MIN_GAP (128*1024*1024)
#define MAX_GAP (TASK_SIZE/6*5)
static inline int mmap_is_legacy(struct rlimit *rlim_stack)
{
if (current->personality & ADDR_COMPAT_LAYOUT)
return 1;
if (rlim_stack->rlim_cur == RLIM_INFINITY)
return 1;
return sysctl_legacy_va_layout;
}
unsigned long arch_mmap_rnd(void)
{
unsigned long shift, rnd;
shift = mmap_rnd_bits;
#ifdef CONFIG_COMPAT
if (is_32bit_task())
shift = mmap_rnd_compat_bits;
#endif
rnd = get_random_long() % (1ul << shift);
return rnd << PAGE_SHIFT;
}
static inline unsigned long stack_maxrandom_size(void)
{
if (!(current->flags & PF_RANDOMIZE))
return 0;
/* 8MB for 32bit, 1GB for 64bit */
if (is_32bit_task())
return (1<<23);
else
return (1<<30);
}
static inline unsigned long mmap_base(unsigned long rnd,
struct rlimit *rlim_stack)
{
unsigned long gap = rlim_stack->rlim_cur;
unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
/* Values close to RLIM_INFINITY can overflow. */
if (gap + pad > gap)
gap += pad;
if (gap < MIN_GAP)
gap = MIN_GAP;
else if (gap > MAX_GAP)
gap = MAX_GAP;
return PAGE_ALIGN(DEFAULT_MAP_WINDOW - gap - rnd);
}
#ifdef CONFIG_PPC_RADIX_MMU
/*
* Same function as generic code used only for radix, because we don't need to overload
* the generic one. But we will have to duplicate, because hash select
* HAVE_ARCH_UNMAPPED_AREA
*/
static unsigned long
radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
int fixed = (flags & MAP_FIXED);
unsigned long high_limit;
struct vm_unmapped_area_info info;
high_limit = DEFAULT_MAP_WINDOW;
if (addr >= high_limit || (fixed && (addr + len > high_limit)))
high_limit = TASK_SIZE;
if (len > high_limit)
return -ENOMEM;
if (fixed) {
if (addr > high_limit - len)
return -ENOMEM;
return addr;
}
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (high_limit - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vm_start_gap(vma)))
return addr;
}
info.flags = 0;
info.length = len;
info.low_limit = mm->mmap_base;
info.high_limit = high_limit;
info.align_mask = 0;
return vm_unmapped_area(&info);
}
static unsigned long
radix__arch_get_unmapped_area_topdown(struct file *filp,
const unsigned long addr0,
const unsigned long len,
const unsigned long pgoff,
const unsigned long flags)
{
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long addr = addr0;
int fixed = (flags & MAP_FIXED);
unsigned long high_limit;
struct vm_unmapped_area_info info;
high_limit = DEFAULT_MAP_WINDOW;
if (addr >= high_limit || (fixed && (addr + len > high_limit)))
high_limit = TASK_SIZE;
if (len > high_limit)
return -ENOMEM;
if (fixed) {
if (addr > high_limit - len)
return -ENOMEM;
return addr;
}
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (high_limit - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vm_start_gap(vma)))
return addr;
}
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = max(PAGE_SIZE, mmap_min_addr);
info.high_limit = mm->mmap_base + (high_limit - DEFAULT_MAP_WINDOW);
info.align_mask = 0;
addr = vm_unmapped_area(&info);
if (!(addr & ~PAGE_MASK))
return addr;
VM_BUG_ON(addr != -ENOMEM);
/*
* A failed mmap() very likely causes application failure,
* so fall back to the bottom-up function here. This scenario
* can happen with large stack limits and large mmap()
* allocations.
*/
return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
}
static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
unsigned long random_factor,
struct rlimit *rlim_stack)
{
if (mmap_is_legacy(rlim_stack)) {
mm->mmap_base = TASK_UNMAPPED_BASE;
mm->get_unmapped_area = radix__arch_get_unmapped_area;
} else {
mm->mmap_base = mmap_base(random_factor, rlim_stack);
mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
}
}
#else
/* dummy */
extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,
unsigned long random_factor,
struct rlimit *rlim_stack);
#endif
/*
* 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, struct rlimit *rlim_stack)
{
unsigned long random_factor = 0UL;
if (current->flags & PF_RANDOMIZE)
random_factor = arch_mmap_rnd();
if (radix_enabled())
return radix__arch_pick_mmap_layout(mm, random_factor,
rlim_stack);
/*
* Fall back to the standard layout if the personality
* bit is set, or if the expected stack growth is unlimited:
*/
if (mmap_is_legacy(rlim_stack)) {
mm->mmap_base = TASK_UNMAPPED_BASE;
mm->get_unmapped_area = arch_get_unmapped_area;
} else {
mm->mmap_base = mmap_base(random_factor, rlim_stack);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
}
}
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