From: Greg Ungerer <gerg@uclinux.org>
To: Waldemar Brodkorb <mail@waldemar-brodkorb.de>,
Waldemar Brodkorb <wbx@openadk.org>
Cc: linux-kernel@vger.kernel.org,
Denys Vlasenko <vda.linux@googlemail.com>,
Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Gustavo Zacarias <gustavo@zacarias.com.ar>
Subject: Re: qemu m68k/mcf5208: problem with signal handler
Date: Mon, 9 May 2016 23:57:01 +1000 [thread overview]
Message-ID: <5730972D.8050409@uclinux.org> (raw)
In-Reply-To: <20160509085815.GB13502@waldemar-brodkorb.de>
Hi Waldemar,
On 09/05/16 18:58, Waldemar Brodkorb wrote:
> Hi,
>
> forgot to add Greg in CC.
> And sorry for the whitespace fuckup in the example code.
>
> Waldemar Brodkorb wrote,
>
>> Dear kernel hackers,
>>
>> I have a problem with the signal handling under qemu-system-m68k
>> emulating coldfire mcf5208 evalboard. Following example code
>> provided by Busybox maintainer Denys Vlasenko
>> shows the problem when running on qemu:
>
> [ .. ]
>
>> You can generate a bootable image with latest buildroot, which shows the issue:
>> $ git clone git://git.buildroot.net/buildroot
>> $ cd buildroot; make qemu_m68k_mcf5208_defconfig; make
>> $ qemu-system-m68k -M mcf5208evb -cpu m5208 -kernel output/images/vmlinux -nographic
>>
>> Every command forked from busybox hush shell will lead into a segmentation fault.
>>
>> I added following printk to start investigating the problem:
>> diff -Nur linux-4.5.3.orig/arch/m68k/kernel/signal.c linux-4.5.3/arch/m68k/kernel/signal.c
>> --- linux-4.5.3.orig/arch/m68k/kernel/signal.c 2016-05-04 23:50:38.000000000 +0200
>> +++ linux-4.5.3/arch/m68k/kernel/signal.c 2016-05-09 04:24:53.885199544 +0200
>> @@ -595,6 +595,7 @@
>> void __user *fp)
>> {
>> int fsize = frame_extra_sizes(formatvec >> 12);
>> + printk("avoid broken signal handler...\n");
>> if (fsize < 0) {
>> /*
>> * user process trying to return with weird frame format
>>
>> But now the problem disappeared. :/
>>
>> What do you think? Is it a Kernel bug or a C library problem?
What version of linux kernel?
What version of gcc?
This sounds a lot like the problem I fixed in linux commit a9551799
("m68k: Use conventional function parameters for do_sigreturn").
Definitely try that first.
Regards
Greg
>> Busybox hush otherwise works fine for other noMMU targets as stm32
>> evalboard with cortex-m4. It also works in Qemu M68k emulating Q800
>> full MMU system.
>>
>> Thanks for any ideas,
>> Waldemar
>>
>> http://lists.busybox.net/pipermail/busybox/2014-September/081659.html
>>
>
next prev parent reply other threads:[~2016-05-09 13:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-09 6:39 qemu m68k/mcf5208: problem with signal handler Waldemar Brodkorb
2016-05-09 8:58 ` Waldemar Brodkorb
2016-05-09 13:57 ` Greg Ungerer [this message]
2016-05-09 16:29 ` Waldemar Brodkorb
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