On Mon, Jan 30, 2017 at 03:04:28PM +0300, Dmitry Safonov wrote:
> I need those arch_{native,compat}_rnd() to compute separately
> random factor for mmap() in compat syscalls for 64-bit binaries
> and vice-versa for native syscall in 32-bit compat binaries.
> They will be used in the following patches.
>
> Signed-off-by: Dmitry Safonov <[email protected]>
> ---
> arch/x86/mm/mmap.c | 25 ++++++++++++++++---------
> 1 file changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
> index d2dc0438d654..42063e787717 100644
> --- a/arch/x86/mm/mmap.c
> +++ b/arch/x86/mm/mmap.c
> @@ -65,20 +65,27 @@ static int mmap_is_legacy(void)
> return sysctl_legacy_va_layout;
> }
>
> -unsigned long arch_mmap_rnd(void)
> +#ifdef CONFIG_COMPAT
> +static unsigned long arch_compat_rnd(void)
> {
> - unsigned long rnd;
> + return (get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1))
> + << PAGE_SHIFT;
> +}
> +#endif
>
> - if (mmap_is_ia32())
> +static unsigned long arch_native_rnd(void)
> +{
> + return (get_random_long() & ((1UL << mmap_rnd_bits) - 1)) << PAGE_SHIFT;
> +}
> +
> +unsigned long arch_mmap_rnd(void)
> +{
> #ifdef CONFIG_COMPAT
> - rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
> -#else
> - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
> + if (mmap_is_ia32())
> + return arch_compat_rnd();
> #endif
I can't say that I'm thrilled about the ifdeffery this is adding.
But I can't think of a cleaner approach at a quick glance, though -
that's generic and arch-specific code intertwined muck. Sad face.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
