| Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2010 Tilera Corporation. All Rights Reserved. |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or |
| 5 | * modify it under the terms of the GNU General Public License |
| 6 | * as published by the Free Software Foundation, version 2. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, but |
| 9 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or |
| 11 | * NON INFRINGEMENT. See the GNU General Public License for |
| 12 | * more details. |
| 13 | * |
| 14 | * Taken from the i386 architecture and simplified. |
| 15 | */ |
| 16 | |
| 17 | #include <linux/mm.h> |
| 18 | #include <linux/random.h> |
| 19 | #include <linux/limits.h> |
| 20 | #include <linux/sched.h> |
| 21 | #include <linux/mman.h> |
| 22 | #include <linux/compat.h> |
| 23 | |
| 24 | /* |
| 25 | * Top of mmap area (just below the process stack). |
| 26 | * |
| 27 | * Leave an at least ~128 MB hole. |
| 28 | */ |
| 29 | #define MIN_GAP (128*1024*1024) |
| 30 | #define MAX_GAP (TASK_SIZE/6*5) |
| 31 | |
| 32 | static inline unsigned long mmap_base(struct mm_struct *mm) |
| 33 | { |
| 34 | unsigned long gap = rlimit(RLIMIT_STACK); |
| 35 | unsigned long random_factor = 0; |
| 36 | |
| 37 | if (current->flags & PF_RANDOMIZE) |
| 38 | random_factor = get_random_int() % (1024*1024); |
| 39 | |
| 40 | if (gap < MIN_GAP) |
| 41 | gap = MIN_GAP; |
| 42 | else if (gap > MAX_GAP) |
| 43 | gap = MAX_GAP; |
| 44 | |
| 45 | return PAGE_ALIGN(TASK_SIZE - gap - random_factor); |
| 46 | } |
| 47 | |
| 48 | /* |
| 49 | * This function, called very early during the creation of a new |
| 50 | * process VM image, sets up which VM layout function to use: |
| 51 | */ |
| 52 | void arch_pick_mmap_layout(struct mm_struct *mm) |
| 53 | { |
| 54 | #if !defined(__tilegx__) |
| 55 | int is_32bit = 1; |
| 56 | #elif defined(CONFIG_COMPAT) |
| 57 | int is_32bit = is_compat_task(); |
| 58 | #else |
| 59 | int is_32bit = 0; |
| 60 | #endif |
| 61 | |
| 62 | /* |
| 63 | * Use standard layout if the expected stack growth is unlimited |
| 64 | * or we are running native 64 bits. |
| 65 | */ |
| 66 | if (!is_32bit || rlimit(RLIMIT_STACK) == RLIM_INFINITY) { |
| 67 | mm->mmap_base = TASK_UNMAPPED_BASE; |
| 68 | mm->get_unmapped_area = arch_get_unmapped_area; |
| 69 | mm->unmap_area = arch_unmap_area; |
| 70 | } else { |
| 71 | mm->mmap_base = mmap_base(mm); |
| 72 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
| 73 | mm->unmap_area = arch_unmap_area_topdown; |
| 74 | } |
| 75 | } |