user application error causes kernel segfault

Hi,

why does crashing application at user level causes system kernel
reports segfault ?
Is this a (new) normal behaviour ?

Example with this wrong code:

#-------------------
MemoryFault.c

#include <stdio.h>
int main(int argc, char *argv[])
{
printf("ARGC=%d ARGV[0]=%s
ARGV[1]=%s\n",argc,*argv[0],*argv[1]);
}

#-------------------
% gcc -o MemoryFault -c MemoryFault.c
% ./MemoryFault

% grep Memory /var/log/messages:

Apr 10 12:57:11 gen105 kernel: MemoryFault[28457]: segfault at
0000000000000000 rip 00000000080483dd rsp 00000000fff96200 error 4


---------
OS     = openSUSE 10.3
Kernel = 2.6.22.17-0.1-default x86_x64


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bsenf
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bsenf wrote:

> 
> Hi,
> 
> why does crashing application at user level causes system kernel
> reports segfault ?
> Is this a (new) normal behaviour ?
> 
> Example with this wrong code:
> 
> #-------------------
> MemoryFault.c
> 
> #include <stdio.h>
> int main(int argc, char *argv[])
> {
> printf("ARGC=%d ARGV[0]=%s
> ARGV[1]=%s\n",argc,*argv[0],*argv[1]);
> }
> 
> #-------------------
> % gcc -o MemoryFault -c MemoryFault.c
> % ./MemoryFault
> 
> % grep Memory /var/log/messages:
> 
> Apr 10 12:57:11 gen105 kernel: MemoryFault[28457]: segfault at
> 0000000000000000 rip 00000000080483dd rsp 00000000fff96200 error 4
> 
> 
> ---------
> OS     = openSUSE 10.3
> Kernel = 2.6.22.17-0.1-default x86_x64
> 
> 

Something in the program is causing an error.  Perhaps some dependency is
not met.  Perhaps some file is not up to date.  Perhaps an update broke
some link.

What program?

-- 
Later,
Darrell Stec      darstec@neo.rr.com

Webpage Sorcery
http://webpagesorcery.com

The code above is intentional wrong - only for reproducing the error of
course.

But WHY does the OS logs this into /var/log/messages ?

I have similary machines and these don't do so - crash yes, but not
notice that within /var/log/messages.


-- 
bsenf
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On Thu, 2008-04-10 at 18:46 +0000, bsenf wrote:
> The code above is intentional wrong - only for reproducing the error of
> course.
> 
> But WHY does the OS logs this into /var/log/messages ?
> 
> I have similary machines and these don't do so - crash yes, but not
> notice that within /var/log/messages.
> 
> 

I just tried it... normal.  SEGV's but doesn't trash the kernel.
I have an AMD x86_64 running openSUSE 10.3 at the same kernel
level as you.

It's possible that your problem is caused by something else
though this program makes it visible.

bsenf wrote:

> 
> Hi,
> 
> why does crashing application at user level causes system kernel
> reports segfault ?
> Is this a (new) normal behaviour ?
> 
> Example with this wrong code:
> 
> #-------------------
> MemoryFault.c
> 
> #include <stdio.h>
> int main(int argc, char *argv[])
> {
> printf("ARGC=%d ARGV[0]=%s
> ARGV[1]=%s\n",argc,*argv[0],*argv[1]);
> }
> 
> #-------------------
> % gcc -o MemoryFault -c MemoryFault.c
> % ./MemoryFault
> 
> % grep Memory /var/log/messages:
> 
> Apr 10 12:57:11 gen105 kernel: MemoryFault[28457]: segfault at
> 0000000000000000 rip 00000000080483dd rsp 00000000fff96200 error 4
> 
> 
> ---------
> OS     = openSUSE 10.3
> Kernel = 2.6.22.17-0.1-default x86_x64

The kernel is telling you that it is handling access to memory
which your program is not allowed to.

Kernels do not segfault, they pagefault.


B

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