Re: [uml-devel] [PATCH] checkstack: use $UTS_MACHINE as target architecture

From: Konstantin Khlebnikov
Date: Tue Jul 08 2014 - 04:30:30 EST

On Tue, Jul 8, 2014 at 12:20 PM, Richard Weinberger <richard@xxxxxx> wrote:
> Am 08.07.2014 10:16, schrieb Konstantin Khlebnikov:
>> On Tue, Jul 8, 2014 at 12:01 PM, Richard Weinberger
>> <richard.weinberger@xxxxxxxxx> wrote:
>>> On Tue, Jul 8, 2014 at 7:48 AM, Konstantin Khlebnikov <koct9i@xxxxxxxxx> wrote:
>>>> On Tue, Jul 8, 2014 at 2:05 AM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>>>>> On Sat, 05 Jul 2014 15:22:38 +0400 Konstantin Khlebnikov <koct9i@xxxxxxxxx> wrote:
>>>>>> This fixes command # make checkstack for i386/x86_64.
>>>>>> Looks like $UTS_MACHINE is exactly what scripts/ needs.
>>>>>> By default $UTS_MACHINE is equal to $ARCH, but some arch/${ARCH}/Makefile
>>>>>> overrides it. This patch updates it also in arch/x86/
>>>>>> broken in ffee0de ("x86: Default to ARCH=x86 to avoid overriding CONFIG_64BIT")
>>>>> The changelog doesn't describe the bug which is being fixed. It should
>>>>> do so please. If there are any compiler/make error messages then those
>>>>> should be included.
>>>> Oh, ok. needs either i386 or x86_64, x86 isn't enough.
>>>> $ make checkstack
>>>> objdump -d vmlinux $(find . -name '*.ko') | \
>>>> perl /home/blind/src/linux-stable/scripts/ x86
>>>> wrong or unknown architecture "x86"
>>> And now we need ARCH, SUBARCH and UTS_MACHINE on UML? :-(
>> Nope UTS_MACHINE is autodetected, see hunk Makefile.x86 in my patch.
>> I thought about cleaning this part of UML.
>> For example we could move arch/x86/um into arch/um/x86 and use # make
>> ARCH=um/x86
> No way. We moved the x86 stuff to arch/x86/ a few Years ago by design.

Ok, fine. We could leave it in arch/x86/um and use make ARCH=x86/um

>> after collecting this stuff together it woud be easier to get rid of
>> forever-broken parts.
>> As I see UML has been designed to work everywhere but SMP seem never worked
>> as well as any host os except of linux or other arch except x86.
> Currently UML runs only on x86_32/64.
> Adding/fixing SMP support should be doable.

This might be quite difficult on top of current ptrace-based design.
I thought about running userspace in kvm context, this might be much
faster than ptrace but requires indirect uaccess like for 4gb-split.
But it's very unlikely that I'll find time for that.

> Thanks,
> //richard
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