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[S390] Randomize mmap start address

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Randomize mmap start address with 8MB.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2011-01-12 09:55:27 +01:00 committed by Martin Schwidefsky
parent 1060f62ea4
commit df1ca53cba
1 changed files with 11 additions and 2 deletions
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13
arch/s390/mm/mmap.c
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@ -27,6 +27,7 @@
#include <linux/personality.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/random.h>
#include <asm/pgalloc.h>
#include <asm/compat.h>
@ -56,6 +57,14 @@ static inline int mmap_is_legacy(void)
return sysctl_legacy_va_layout;
}
static unsigned long mmap_rnd(void)
{
if (!(current->flags & PF_RANDOMIZE))
return 0;
/* 8MB randomization for mmap_base */
return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
}
static inline unsigned long mmap_base(void)
{
unsigned long gap = rlimit(RLIMIT_STACK);
@ -64,8 +73,8 @@ static inline unsigned long mmap_base(void)
gap = MIN_GAP;
else if (gap > MAX_GAP)
gap = MAX_GAP;
return STACK_TOP - stack_maxrandom_size() - (gap & PAGE_MASK);
gap &= PAGE_MASK;
return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
}
#ifndef CONFIG_64BIT