From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f44.google.com (mail-pa0-f44.google.com [209.85.220.44]) by kanga.kvack.org (Postfix) with ESMTP id 4AA636B0038 for ; Mon, 14 Dec 2015 06:19:49 -0500 (EST) Received: by pabur14 with SMTP id ur14so102879537pab.0 for ; Mon, 14 Dec 2015 03:19:49 -0800 (PST) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id rr8si7888358pab.51.2015.12.14.03.19.48 for ; Mon, 14 Dec 2015 03:19:48 -0800 (PST) Date: Mon, 14 Dec 2015 11:19:49 +0000 From: Will Deacon Subject: Re: [PATCH v6 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. Message-ID: <20151214111949.GD6992@arm.com> References: <1449856338-30984-1-git-send-email-dcashman@android.com> <1449856338-30984-2-git-send-email-dcashman@android.com> <1449856338-30984-3-git-send-email-dcashman@android.com> <1449856338-30984-4-git-send-email-dcashman@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1449856338-30984-4-git-send-email-dcashman@android.com> Sender: owner-linux-mm@kvack.org List-ID: 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, arnd@arndb.de, jonathanh@nvidia.com Hi Daniel, On Fri, Dec 11, 2015 at 09:52:17AM -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 | 33 +++++++++++++++++++++++++++++++++ > arch/arm64/mm/mmap.c | 8 ++++++-- > 2 files changed, 39 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 871f217..0cc9c24 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 && !(ARM64_16K_PAGES && ARM64_VA_BITS_48) > 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 +106,37 @@ config ARCH_PHYS_ADDR_T_64BIT > config MMU > def_bool y > > +config ARCH_MMAP_RND_BITS_MIN > + default 14 if ARM64_64K_PAGES > + default 16 if ARM64_16K_PAGES > + default 18 > + > +# max bits determined by the following formula: > +# VA_BITS - PAGE_SHIFT - 3 Now that we have this comment, I think we can drop the unsupported combinations from the list below. That means we just end up with: > +config ARCH_MMAP_RND_BITS_MAX > + default 19 if ARM64_VA_BITS=36 > + default 24 if ARM64_VA_BITS=39 > + default 27 if ARM64_VA_BITS=42 > + default 30 if ARM64_VA_BITS=47 > + default 29 if ARM64_VA_BITS=48 && ARM64_64K_PAGES > + default 31 if ARM64_VA_BITS=48 && ARM64_16K_PAGES > + default 33 if ARM64_VA_BITS=48 With that: Acked-by: Will Deacon Will -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org