Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755819AbbKCSKY (ORCPT ); Tue, 3 Nov 2015 13:10:24 -0500 Received: from mail-pa0-f51.google.com ([209.85.220.51]:33867 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755704AbbKCSKU (ORCPT ); Tue, 3 Nov 2015 13:10:20 -0500 From: Daniel Cashman To: linux-kernel@vger.kernel.org Cc: 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, dcashman Subject: [PATCH v2 2/2] arm: mm: support ARCH_MMAP_RND_BITS. Date: Tue, 3 Nov 2015 10:10:04 -0800 Message-Id: <1446574204-15567-2-git-send-email-dcashman@android.com> X-Mailer: git-send-email 2.6.0.rc2.230.g3dd15c0 In-Reply-To: <1446574204-15567-1-git-send-email-dcashman@android.com> References: <1446574204-15567-1-git-send-email-dcashman@android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2463 Lines: 70 From: dcashman arm: arch_mmap_rnd() uses a hard-code value of 8 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 8 as the minimum acceptable value. Signed-off-by: Daniel Cashman --- Changes in v2: - Changed arch/arm/Kconfig and arch/arm/mm/mmap.c to reflect changes in [PATCH v2 1/2], specifically the movement of variables to global rather than arch-specific files. arch/arm/Kconfig | 10 ++++++++++ arch/arm/mm/mmap.c | 3 +-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 639411f..47d7561 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -35,6 +35,7 @@ config ARM select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6 select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 + select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT) select HAVE_ARCH_TRACEHOOK select HAVE_BPF_JIT @@ -306,6 +307,15 @@ config MMU Select if you want MMU-based virtualised addressing space support by paged memory management. If unsure, say 'Y'. +config ARCH_MMAP_RND_BITS_MIN + default 8 + +config ARCH_MMAP_RND_BITS_MAX + default 14 if MMU && PAGE_OFFSET=0x40000000 + default 15 if MMU && PAGE_OFFSET=0x80000000 + default 16 if MMU + default 8 + # # The "ARM system type" choice list is ordered alphabetically by option # text. Please add new entries in the option alphabetic order. diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c index 407dc78..c938693 100644 --- a/arch/arm/mm/mmap.c +++ b/arch/arm/mm/mmap.c @@ -173,8 +173,7 @@ unsigned long arch_mmap_rnd(void) { unsigned long rnd; - /* 8 bits of randomness in 20 address space bits */ - rnd = (unsigned long)get_random_int() % (1 << 8); + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits); return rnd << PAGE_SHIFT; } -- 2.6.0.rc2.230.g3dd15c0 -- 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/