[PATCH 2/5] [ARM] add address randomization to mmap()

[Kyungmin Park]

Hi,

On Thu, Jun 17, 2010 at 5:33 AM, Nicolas Pitre <nico at fluxnic.net> wrote:
> Signed-off-by: Nicolas Pitre <nicolas.pitre at linaro.org>
> ---
>  arch/arm/mm/mmap.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
> index f5abc51..4f5b396 100644
> --- a/arch/arm/mm/mmap.c
> +++ b/arch/arm/mm/mmap.c
> @@ -7,6 +7,7 @@
>  #include <linux/shm.h>
>  #include <linux/sched.h>
>  #include <linux/io.h>
> +#include <linux/random.h>
>  #include <asm/cputype.h>
>  #include <asm/system.h>
>
> @@ -80,6 +81,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
>                start_addr = addr = TASK_UNMAPPED_BASE;
>                mm->cached_hole_size = 0;
>        }
> +       /* 8 bits of randomness in 20 address space bits */
> +       if (current->flags & PF_RANDOMIZE)
> +               addr += (get_random_int() % (1 << 8)) << PAGE_SHIFT;

Doesn't better to use mask operation?
                   addr += (get_random_int() & ((1 << 8) - 1)) << PAGE_SHIFT;

Thank you,
Kyungmin Park
>
>  full_search:
>        if (do_align)
> --
> 1.7.1.337.gbd0bc
>
>
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