* qemu m68k/mcf5208: problem with signal handler
@ 2016-05-09 6:39 Waldemar Brodkorb
2016-05-09 8:58 ` Waldemar Brodkorb
0 siblings, 1 reply; 4+ messages in thread
From: Waldemar Brodkorb @ 2016-05-09 6:39 UTC (permalink / raw)
To: linux-kernel; +Cc: Denys Vlasenko, Thomas Petazzoni, Gustavo Zacarias
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:
#include <unistd.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
static void sighandler(int sig)
{
write(1, "SIGNAL\n", 7);
}
int main()
{
int pid;
write(1, "VFORK1\n", 7);
pid = vfork();
if (pid == 0) {
write(1, "EXIT1\n", 6);
_exit(1);
}
wait(NULL);
signal(SIGCHLD, sighandler);
write(1, "VFORK2\n", 7);
pid = vfork();
if (pid == 0) {
write(1, "EXIT2\n", 6);
_exit(1);
}
wait(NULL);
write(1, "EXIT\n", 5);
return 0;
}
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?
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
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: qemu m68k/mcf5208: problem with signal handler
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
0 siblings, 1 reply; 4+ messages in thread
From: Waldemar Brodkorb @ 2016-05-09 8:58 UTC (permalink / raw)
To: Waldemar Brodkorb
Cc: linux-kernel, Denys Vlasenko, Thomas Petazzoni, Gustavo Zacarias,
Greg Ungerer
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?
>
> 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
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: qemu m68k/mcf5208: problem with signal handler
2016-05-09 8:58 ` Waldemar Brodkorb
@ 2016-05-09 13:57 ` Greg Ungerer
2016-05-09 16:29 ` Waldemar Brodkorb
0 siblings, 1 reply; 4+ messages in thread
From: Greg Ungerer @ 2016-05-09 13:57 UTC (permalink / raw)
To: Waldemar Brodkorb, Waldemar Brodkorb
Cc: linux-kernel, Denys Vlasenko, Thomas Petazzoni, Gustavo Zacarias
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
>>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: qemu m68k/mcf5208: problem with signal handler
2016-05-09 13:57 ` Greg Ungerer
@ 2016-05-09 16:29 ` Waldemar Brodkorb
0 siblings, 0 replies; 4+ messages in thread
From: Waldemar Brodkorb @ 2016-05-09 16:29 UTC (permalink / raw)
To: Greg Ungerer
Cc: Waldemar Brodkorb, linux-kernel, Denys Vlasenko, Thomas Petazzoni,
Gustavo Zacarias, Geert Uytterhoeven
Hi Greg,
Greg Ungerer wrote,
> >>What do you think? Is it a Kernel bug or a C library problem?
>
> What version of linux kernel?
4.5.3
> What version of gcc?
4.9.3
> 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.
Jackpot. Thanks a lot. This works!
May be some candidate for LTS kernels.
best regards
Waldemar
^ permalink raw reply [flat|nested] 4+ messages in thread
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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
2016-05-09 16:29 ` Waldemar Brodkorb
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