Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753443AbbKWPFI (ORCPT ); Mon, 23 Nov 2015 10:05:08 -0500 Received: from foss.arm.com ([217.140.101.70]:56508 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751563AbbKWPFG (ORCPT ); Mon, 23 Nov 2015 10:05:06 -0500 Date: Mon, 23 Nov 2015 15:04:59 +0000 From: Will Deacon To: Daniel Cashman Cc: linux-kernel@vger.kernel.org, linux@arm.linux.org.uk, akpm@linux-foundation.org, keescook@chromium.org, mingo@kernel.org, linux-arm-kernel@lists.infradead.org, corbet@lwn.net, dzickus@redhat.com, ebiederm@xmission.com, xypron.glpk@gmx.de, jpoimboe@redhat.com, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, aarcange@redhat.com, mgorman@suse.de, tglx@linutronix.de, rientjes@google.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, salyzyn@android.com, jeffv@google.com, nnk@google.com, catalin.marinas@arm.com, hpa@zytor.com, x86@kernel.org, hecmargi@upv.es, bp@suse.de, dcashman@google.com Subject: Re: [PATCH v3 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Message-ID: <20151123150459.GD4236@arm.com> References: <1447888808-31571-1-git-send-email-dcashman@android.com> <1447888808-31571-2-git-send-email-dcashman@android.com> <1447888808-31571-3-git-send-email-dcashman@android.com> <1447888808-31571-4-git-send-email-dcashman@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1447888808-31571-4-git-send-email-dcashman@android.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2270 Lines: 61 On Wed, Nov 18, 2015 at 03:20:07PM -0800, Daniel Cashman wrote: > From: dcashman > > arm64: arch_mmap_rnd() uses STACK_RND_MASK to generate the > random offset for the mmap base address. This value represents a > compromise between increased ASLR effectiveness and avoiding > address-space fragmentation. Replace it with a Kconfig option, which > is sensibly bounded, so that platform developers may choose where to > place this compromise. Keep default values as new minimums. > > Signed-off-by: Daniel Cashman > --- > arch/arm64/Kconfig | 23 +++++++++++++++++++++++ > arch/arm64/mm/mmap.c | 6 ++++-- > 2 files changed, 27 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 9ac16a4..be38e4c 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -51,6 +51,8 @@ config ARM64 > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP > select HAVE_ARCH_KGDB > + select HAVE_ARCH_MMAP_RND_BITS > + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_TRACEHOOK > select HAVE_BPF_JIT > @@ -104,6 +106,27 @@ config ARCH_PHYS_ADDR_T_64BIT > config MMU > def_bool y > > +config ARCH_MMAP_RND_BITS_MIN > + default 15 if ARM64_64K_PAGES > + default 19 > + > +config ARCH_MMAP_RND_BITS_MAX > + default 20 if ARM64_64K_PAGES && ARCH_VA_BITS=39 > + default 24 if ARCH_VA_BITS=39 > + default 23 if ARM64_64K_PAGES && ARCH_VA_BITS=42 > + default 27 if ARCH_VA_BITS=42 > + default 29 if ARM64_64K_PAGES && ARCH_VA_BITS=48 > + default 33 if ARCH_VA_BITS=48 > + default 15 if ARM64_64K_PAGES > + default 19 > + > +config ARCH_MMAP_RND_COMPAT_BITS_MIN > + default 7 if ARM64_64K_PAGES > + default 11 FYI: we now support 16k pages too, so this might need updating. It would be much nicer if this was somehow computed rather than have the results all open-coded like this. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/