linux-kernel - Re: [PATCH 1/8] um: Create defconfigs for i386 and x86

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Date:	Thu, 26 Sep 2013 12:35:12 +0200
From:	Richard Weinberger <richard@....at>
To:	Ramkumar Ramachandra <artagnon@...il.com>
CC:	linux-arch@...r.kernel.org, Michal Marek <mmarek@...e.cz>,
	geert@...ux-m68k.org, ralf@...ux-mips.org, lethal@...ux-sh.org,
	Jeff Dike <jdike@...toit.com>, gxt@...c.pku.edu.cn,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kbuild@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	linux-m68k@...ts.linux-m68k.org, linux-mips@...ux-mips.org,
	linux-sh@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net,
	Toralf Förster <toralf.foerster@....de>
Subject: Re: [PATCH 1/8] um: Create defconfigs for i386 and x86_64

Am 26.09.2013 12:20, schrieb Ramkumar Ramachandra:
> Richard Weinberger wrote:
>> This patch is based on: https://lkml.org/lkml/2013/7/4/396
>>
>> Cc: Ramkumar Ramachandra <artagnon@...il.com>
>> Signed-off-by: Richard Weinberger <richard@....at>
>> ---
>>  arch/um/configs/i386_defconfig   | 954 +++++++++++++++++++++++++++++++++++++++
>>  arch/um/configs/x86_64_defconfig | 943 ++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 1897 insertions(+)
>>  create mode 100644 arch/um/configs/i386_defconfig
>>  create mode 100644 arch/um/configs/x86_64_defconfig
> 
> First, I'm pissed that the upstream tree doesn't build and run out of
> the box months after I submitted a fix in July (and it's September
> now). Fact that you dropped my sane patches aside and decided to write
> a much larger series aside, user-mode Linux in upstream is broken.
> This means that any user who does:
> 
> $ ARCH=um make defconfig
> $ ARCH=um make
> 
> will end up with a *broken* Linux _today_. Unless the user is living
> in the Stone Age with a 32-bit computer, this is what she will see
> when she attempts to boot up Linux:

Not here.

> $ file linux
> linux: ELF 32-bit LSB  executable, Intel 80386, version 1 (SYSV),
> dynamically linked (uses shared libs), for GNU/Linux 2.6.32, not
> stripped
> $ ./linux ubd0=busybox-rootfs
> [...]
> Kernel panic - not syncing: No init found.  Try passing init= option
> to kernel. See Linux Documentation/init.txt for guidance.

I don't know that rootfs but it looks like there is no init.

> CPU: 0 PID: 1 Comm: swapper Not tainted 3.12.0-rc2-00083-g4b97280 #1
> 0b869fbc 08272f87 0b869fdc 0820c5cd 00000001 00000000 00000000 00000000
>        0b869fe8 0820c126 08252593 0b869ff8 08059317 00000000 00000001 00000000
>        00000000 0b869f94:  [<0805a11c>] show_stack+0x54/0x8c
> 0b869fb4:  [<0820e3c8>] dump_stack+0x16/0x1b
> 0b869fc8:  [<0820c5cd>] panic+0x67/0x149
> 0b869fe0:  [<0820c126>] kernel_init+0xab/0xaf
> 0b869fec:  [<08059317>] new_thread_handler+0x63/0x7c
> 0b869ffc:  [<00000000>] 0x0
> 
> 
> EIP: 0023:[<f7717430>] CPU: 0 Not tainted ESP: 002b:ffc386dc EFLAGS: 00000296
>     Not tainted
> EAX: 00000000 EBX: 000063ba ECX: 00000013 EDX: 000063ba
> ESI: 000063b6 EDI: 00000002 EBP: ffc38708 DS: 002b ES: 002b
> 0b869f44:  [<0806aff4>] show_regs+0xb4/0xbc
> 0b869f70:  [<0805b23b>] panic_exit+0x20/0x36
> 0b869f84:  [<0808521b>] notifier_call_chain+0x28/0x4b
> 0b869fac:  [<0808526c>] atomic_notifier_call_chain+0x15/0x17
> 0b869fbc:  [<0820c5de>] panic+0x78/0x149
> 0b869fe0:  [<0820c126>] kernel_init+0xab/0xaf
> 0b869fec:  [<08059317>] new_thread_handler+0x63/0x7c
> 0b869ffc:  [<00000000>] 0x0
> 
> [1]    25526 abort (core dumped)  linux ubd0=busybox-rootfs
>                                                            %
> 
> Rubbish.

UML core dumps at panic() by design.

> When I rebase my original patches (exactly 2 small independent
> patches) onto the new upstream, stuff works as usual. If you're not
> convinced, try the um-build branch from
> https://github.com/artagnon/linux for yourself.

> Are you against accepting good patches and stalling work? What is your
> plan exactly?

Sure, my great plan is to destroy Linux. I work for Microsoft. ;-)

Seriously, my plan is to get rid of SUBARCH, that's why I did not push your patches
upstream and I've send the rid of SUBARCH patch series.
It turned out that other archs depend on SUBARCH too therefore some more thinking is needed.
Time passed, merge window closed, $dayjob needed some attention...

That said, your "arch/um: make it work with defconfig and x86_64" patch is also not perfect.
"make defconfig ARCH=um SUBARCH=x86" will create x86_64 defconfig, which is wrong and breaks existing
setups.
Secondly, what stops you from running "make defconfig ARCH=um SUBARCH=x86_64" to run your x86_64 bit
userspace?

Thanks,
//richard
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