android_kernel_motorola_sm6225/arch/x86_64/mm/mmap.c
Andi Kleen 8817210d4d [PATCH] x86_64: Flexmap for 32bit and randomized mappings for 64bit
Another try at this.

For 32bit follow the 32bit implementation from Ingo -
mappings are growing down from the end of stack now
and vary randomly by 1GB.

Randomized mappings for 64bit just vary the normal mmap break
by 1TB. I didn't bother implementing full flex mmap for 64bit
because it shouldn't be needed there.

Cc: mingo@elte.hu

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-16 23:18:35 -08:00

30 lines
893 B
C

/* Copyright 2005 Andi Kleen, SuSE Labs.
* Licensed under GPL, v.2
*/
#include <linux/config.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/random.h>
#include <asm/ia32.h>
/* Notebook: move the mmap code from sys_x86_64.c over here. */
void arch_pick_mmap_layout(struct mm_struct *mm)
{
#ifdef CONFIG_IA32_EMULATION
if (current_thread_info()->flags & _TIF_IA32)
return ia32_pick_mmap_layout(mm);
#endif
mm->mmap_base = TASK_UNMAPPED_BASE;
if (current->flags & PF_RANDOMIZE) {
/* Add 28bit randomness which is about 40bits of address space
because mmap base has to be page aligned.
or ~1/128 of the total user VM
(total user address space is 47bits) */
unsigned rnd = get_random_int() & 0xfffffff;
mm->mmap_base += ((unsigned long)rnd) << PAGE_SHIFT;
}
mm->get_unmapped_area = arch_get_unmapped_area;
mm->unmap_area = arch_unmap_area;
}