From: Nathan_Lynch@mentor•com (Nathan Lynch)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v9 4/6] ARM: add vdso user-space code
Date: Wed, 10 Sep 2014 12:25:28 -0500 [thread overview]
Message-ID: <54108988.9050307@mentor.com> (raw)
In-Reply-To: <20140910171014.GF1710@arm.com>
On 09/10/2014 12:10 PM, Will Deacon wrote:
> On Wed, Sep 10, 2014 at 05:52:39PM +0100, Andy Lutomirski wrote:
>> On Wed, Sep 10, 2014 at 9:47 AM, Will Deacon <will.deacon@arm•com> wrote:
>>> On Fri, Aug 22, 2014 at 10:52:29PM +0100, Nathan Lynch wrote:
>>>> Place vdso-related user-space code in arch/arm/kernel/vdso/.
>>>>
>>>> It is almost completely written in C with some assembly helpers to
>>>> load the data page address, sample the counter, and fall back to
>>>> system calls when necessary.
>>>
>>> I'm still a bit puzzled as to how we can implement a compat version of this
>>> for a 32-bit userspace running under a 64-bit kernel. Maybe the answer is
>>> that we don't care enough (programs will still work fine without it), but if
>>> we did want to then we're going to need to build the kernel with two
>>> toolchains and it gets really horrible.
>>>
>>> Do you have any ideas?
>>
>> Convince the gcc and binutils people to add a-m32 option to aarch64?
>> That's how x86_64 pulls this off :) Or you could require a
>> cross-compiler to be available to enable this particular feature.
>
> The compilers have two separate backends, so I think I'll know what they
> say. I guess it's either overhauling kbuild to support two cross compilers,
> or have some shell script to accept an option we make up.
arch/powerpc has addressed this with a CROSS32_COMPILE= variable for
producing 32-bit outputs (compat vdso, bootwrapper) during a 64-bit
kernel build. I think that was used before powerpc toolchains commonly
honored -m32.
next prev parent reply other threads:[~2014-09-10 17:25 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-22 21:52 [PATCH v9 0/6] ARM: VDSO Nathan Lynch
2014-08-22 21:52 ` [PATCH v9 1/6] ARM: use _install_special_mapping for sigpage Nathan Lynch
2014-08-22 21:52 ` [PATCH v9 2/6] ARM: place sigpage at a random offset above stack Nathan Lynch
2014-08-22 21:52 ` [PATCH v9 3/6] ARM: miscellaneous vdso infrastructure, preparation Nathan Lynch
2014-08-22 21:52 ` [PATCH v9 4/6] ARM: add vdso user-space code Nathan Lynch
2014-09-10 16:47 ` Will Deacon
2014-09-10 16:52 ` Andy Lutomirski
2014-09-10 17:10 ` Will Deacon
2014-09-10 17:25 ` Nathan Lynch [this message]
2014-09-12 6:50 ` Nathan Lynch
2014-08-22 21:52 ` [PATCH v9 5/6] ARM: vdso initialization, mapping, and synchronization Nathan Lynch
2014-08-22 21:52 ` [PATCH v9 6/6] ARM: add CONFIG_VDSO Kconfig and Makefile bits Nathan Lynch
2014-08-27 20:49 ` [PATCH v9 0/6] ARM: VDSO Christopher Covington
2014-08-27 21:42 ` Andy Lutomirski
2014-09-03 5:41 ` Nathan Lynch
2014-09-03 13:13 ` Christopher Covington
2014-09-03 16:59 ` Andy Lutomirski
2014-09-03 20:03 ` Nathan Lynch
2014-09-03 20:12 ` Andy Lutomirski
2014-09-06 2:32 ` Nathan Lynch
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