On Thu, Feb 9, 2017 at 5:55 AM, Borislav Petkov <bp@xxxxxxxxx> wrote: > 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 <dsafonov@xxxxxxxxxxxxx> >> --- >> 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. I can, but it could be considerably more churn: get rid of the compat/native split and do a 32-bit/64-bit split instead. > > -- > Regards/Gruss, > Boris. > > Good mailing practices for 400: avoid top-posting and trim the reply. -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>