From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.
Date: Thu, 3 Dec 2015 12:17:12 +0000 [thread overview]
Message-ID: <20151203121712.GE11337@arm.com> (raw)
In-Reply-To: <1449000658-11475-4-git-send-email-dcashman@android.com>
Hi Daniel,
On Tue, Dec 01, 2015 at 12:10:57PM -0800, Daniel Cashman wrote:
> From: dcashman <dcashman@google•com>
>
> 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 <dcashman@android•com>
> ---
> arch/arm64/Kconfig | 31 +++++++++++++++++++++++++++++++
> arch/arm64/mm/mmap.c | 8 ++++++--
> 2 files changed, 37 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 871f217..fb57649 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 if MMU
> + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
You can drop the 'if MMU' bits, since we don't support !MMU on arm64.
> select HAVE_ARCH_SECCOMP_FILTER
> select HAVE_ARCH_TRACEHOOK
> select HAVE_BPF_JIT
> @@ -104,6 +106,35 @@ config ARCH_PHYS_ADDR_T_64BIT
> config MMU
> def_bool y
>
> +config ARCH_MMAP_RND_BITS_MIN
> + default 15 if ARM64_64K_PAGES
> + default 17 if ARM64_16K_PAGES
> + default 19
Is this correct? We currently have a mask of 0x3ffff, so that's 18 bits.
> +config ARCH_MMAP_RND_BITS_MAX
> + default 19 if ARM64_VA_BITS=36
> + default 20 if ARM64_64K_PAGES && ARM64_VA_BITS=39
> + default 22 if ARM64_16K_PAGES && ARM64_VA_BITS=39
> + default 24 if ARM64_VA_BITS=39
> + default 23 if ARM64_64K_PAGES && ARM64_VA_BITS=42
> + default 25 if ARM64_16K_PAGES && ARM64_VA_BITS=42
> + default 27 if ARM64_VA_BITS=42
> + default 30 if ARM64_VA_BITS=47
> + default 29 if ARM64_64K_PAGES && ARM64_VA_BITS=48
> + default 31 if ARM64_16K_PAGES && ARM64_VA_BITS=48
> + default 33 if ARM64_VA_BITS=48
> + default 15 if ARM64_64K_PAGES
> + default 17 if ARM64_16K_PAGES
> + default 19
Could you add a comment above this with the formula
(VA_BITS - PAGE_SHIFT - 3), please, so that we can update this easily in
the future if we need to?
Will
next prev parent reply other threads:[~2015-12-03 12:17 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-01 20:10 [PATCH v5 0/4] Allow customizable random offset to mmap_base address Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 1/4] mm: mmap: Add new /proc tunable for mmap_base ASLR Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 2/4] arm: mm: support ARCH_MMAP_RND_BITS Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 3/4] arm64: " Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 4/4] x86: " Daniel Cashman
2015-12-03 12:17 ` Will Deacon [this message]
2015-12-03 16:12 ` [PATCH v5 3/4] arm64: " Daniel Cashman
2015-12-07 10:26 ` Jon Hunter
2015-12-07 11:13 ` Arnd Bergmann
2015-12-07 18:26 ` Daniel Cashman
2015-12-08 10:03 ` Arnd Bergmann
2015-12-01 22:39 ` [PATCH v5 0/4] Allow customizable random offset to mmap_base address Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20151203121712.GE11337@arm.com \
--to=will.deacon@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox