Date: Thu, 20 Feb 2003 12:10:27 +0100 From: Sebastian Lederer <sl@linast.de> To: Wes Peters <wes@softweyr.com> Cc: V.Haisman@sh.cvut.cz, freebsd-hackers@freebsd.org Subject: Re: Raising SIGSEGV in SIGSEGV handler makes FreeBSD loop Message-ID: <20030220121027.31d74d3f.sl@linast.de> In-Reply-To: <200302190851.23498.wes@softweyr.com> References: <20030219134131.T70370-100000@logout.sh.cvut.cz> <200302190851.23498.wes@softweyr.com>
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On Wed, 19 Feb 2003 08:51:23 -0800
Wes Peters <wes@softweyr.com> wrote:
> On Wednesday 19 February 2003 04:43, Vaclav Haisman wrote:
[...]
> > Besides, this doesn't explain anything. I see I haven't asked any
> > question in my previous post. So, why does FreeBSD behave different?
>
> Because it *is* different? If you want to catch a signal and be
> able to handle it, the other two are wrong, are they not?
>
[...]
I think the real question here is, what happens if a SIGSEGV occurs when
SIGSEGV is already blocked (like inside the handler)?
See the simple test program below. It seems that on FreeBSD, the process
just loops on the faulting instruction, whereas Linux and Solaris
kill the process, producing a SIGSEGV exit code.
I don't know what the correct behaviour is. It is possible to
recover from such a SIGSEGV loop from inside the process, using a timer
signal, for example, so you might say it is legal to do this and
FreeBSD has the correct behaviour. On the other hand, it's most likely
just a badly coded crashed program that would waste all free CPU cycles
if not killed right away.
- Sebastian Lederer
---
#include <signal.h>
#include <stdio.h>
void crash()
{
int *p=NULL;
*p=0xdead;
}
int main(int argc, char **argv)
{
sigset_t set;
sigset_t oset;
sigemptyset(&set);
sigaddset(&set,SIGSEGV);
sigprocmask(SIG_SETMASK,&set,&oset);
crash();
sigprocmask(SIG_SETMASK,&oset,NULL);
return 0;
}
---
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