/* * flexible mmap layout support * * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. * All Rights Reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * 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, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * * * Started by Ingo Molnar <mingo@elte.hu> */ #include <linux/personality.h> #include <linux/mm.h> /* * Top of mmap area (just below the process stack). * * Leave an at least ~128 MB hole. */ #define MIN_GAP (128*1024*1024) #define MAX_GAP (TASK_SIZE/6*5) static inline unsigned long mmap_base(void) { unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur; if (gap < MIN_GAP) gap = MIN_GAP; else if (gap > MAX_GAP) gap = MAX_GAP; return TASK_SIZE - (gap & PAGE_MASK); } static inline int mmap_is_legacy(void) { /* * Force standard allocation for 64 bit programs. */ if (!test_thread_flag(TIF_32BIT)) return 1; if (current->personality & ADDR_COMPAT_LAYOUT) return 1; if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY) return 1; return sysctl_legacy_va_layout; } /* * 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; mm->unmap_area = arch_unmap_area; } else { mm->mmap_base = mmap_base(); mm->get_unmapped_area = arch_get_unmapped_area_topdown; mm->unmap_area = arch_unmap_area_topdown; } }