2 * linux/arch/i386/mm/mmap.c
4 * flexible mmap layout support
6 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 * Started by Ingo Molnar <mingo@elte.hu>
27 #include <linux/personality.h>
29 #include <linux/random.h>
30 #include <linux/sched.h>
33 * Top of mmap area (just below the process stack).
35 * Leave an at least ~128 MB hole.
37 #define MIN_GAP (128*1024*1024)
38 #define MAX_GAP (TASK_SIZE/6*5)
40 static inline unsigned long mmap_base(struct mm_struct
*mm
)
42 unsigned long gap
= current
->signal
->rlim
[RLIMIT_STACK
].rlim_cur
;
43 unsigned long random_factor
= 0;
45 if (current
->flags
& PF_RANDOMIZE
)
46 random_factor
= get_random_int() % (1024*1024);
50 else if (gap
> MAX_GAP
)
53 return PAGE_ALIGN(TASK_SIZE
- gap
- random_factor
);
57 * This function, called very early during the creation of a new
58 * process VM image, sets up which VM layout function to use:
61 void arch_pick_mmap_layout(struct mm_struct
*mm
)
63 void ia32_pick_mmap_layout(struct mm_struct
*mm
)
67 * Fall back to the standard layout if the personality
68 * bit is set, or if the expected stack growth is unlimited:
70 if (sysctl_legacy_va_layout
||
71 (current
->personality
& ADDR_COMPAT_LAYOUT
) ||
72 current
->signal
->rlim
[RLIMIT_STACK
].rlim_cur
== RLIM_INFINITY
) {
73 mm
->mmap_base
= TASK_UNMAPPED_BASE
;
74 mm
->get_unmapped_area
= arch_get_unmapped_area
;
75 mm
->unmap_area
= arch_unmap_area
;
77 mm
->mmap_base
= mmap_base(mm
);
78 mm
->get_unmapped_area
= arch_get_unmapped_area_topdown
;
79 mm
->unmap_area
= arch_unmap_area_topdown
;