1/* 2 * flexible mmap layout support 3 * 4 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. 5 * All Rights Reserved. 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 20 * 21 * 22 * Started by Ingo Molnar <mingo@elte.hu> 23 */ 24 25#include <linux/personality.h> 26#include <linux/mm.h> 27#include <linux/sched.h> 28 29/* 30 * Top of mmap area (just below the process stack). 31 * 32 * Leave an at least ~128 MB hole. 33 */ 34#define MIN_GAP (128*1024*1024) 35#define MAX_GAP (TASK_SIZE/6*5) 36 37static inline unsigned long mmap_base(void) 38{ 39 unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur; 40 41 if (gap < MIN_GAP) 42 gap = MIN_GAP; 43 else if (gap > MAX_GAP) 44 gap = MAX_GAP; 45 46 return TASK_SIZE - (gap & PAGE_MASK); 47} 48 49static inline int mmap_is_legacy(void) 50{ 51 /* 52 * Force standard allocation for 64 bit programs. 53 */ 54 if (!test_thread_flag(TIF_32BIT)) 55 return 1; 56 57 if (current->personality & ADDR_COMPAT_LAYOUT) 58 return 1; 59 60 if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) 61 return 1; 62 63 return sysctl_legacy_va_layout; 64} 65 66/* 67 * This function, called very early during the creation of a new 68 * process VM image, sets up which VM layout function to use: 69 */ 70void arch_pick_mmap_layout(struct mm_struct *mm) 71{ 72 /* 73 * Fall back to the standard layout if the personality 74 * bit is set, or if the expected stack growth is unlimited: 75 */ 76 if (mmap_is_legacy()) { 77 mm->mmap_base = TASK_UNMAPPED_BASE; 78 mm->get_unmapped_area = arch_get_unmapped_area; 79 mm->unmap_area = arch_unmap_area; 80 } else { 81 mm->mmap_base = mmap_base(); 82 mm->get_unmapped_area = arch_get_unmapped_area_topdown; 83 mm->unmap_area = arch_unmap_area_topdown; 84 } 85} 86