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Diffstat (limited to 'arch/powerpc/mm/mmap_64.c')
| -rw-r--r-- | arch/powerpc/mm/mmap_64.c | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/arch/powerpc/mm/mmap_64.c b/arch/powerpc/mm/mmap_64.c new file mode 100644 index 000000000000..0d957a4c70fe --- /dev/null +++ b/arch/powerpc/mm/mmap_64.c @@ -0,0 +1,109 @@ +/* + * 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> +#include <linux/random.h> +#include <linux/sched.h> + +/* + * Top of mmap area (just below the process stack). + * + * Leave at least a ~128 MB hole on 32bit applications. + * + * On 64bit applications we randomise the stack by 1GB so we need to + * space our mmap start address by a further 1GB, otherwise there is a + * chance the mmap area will end up closer to the stack than our ulimit + * requires. + */ +#define MIN_GAP32 (128*1024*1024) +#define MIN_GAP64 ((128 + 1024)*1024*1024UL) +#define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64) +#define MAX_GAP (TASK_SIZE/6*5) + +static inline int mmap_is_legacy(void) +{ + 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; +} + +/* + * Since get_random_int() returns the same value within a 1 jiffy window, + * we will almost always get the same randomisation for the stack and mmap + * region. This will mean the relative distance between stack and mmap will + * be the same. + * + * To avoid this we can shift the randomness by 1 bit. + */ +static unsigned long mmap_rnd(void) +{ + unsigned long rnd = 0; + + if (current->flags & PF_RANDOMIZE) { + /* 8MB for 32bit, 1GB for 64bit */ + if (is_32bit_task()) + rnd = (long)(get_random_int() % (1<<(22-PAGE_SHIFT))); + else + rnd = (long)(get_random_int() % (1<<(29-PAGE_SHIFT))); + } + return (rnd << PAGE_SHIFT) * 2; +} + +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 PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd()); +} + +/* + * 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; + } +} |