linux-kernel - Re: signals logged / [RFC] log out-of-virtual-memory events

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Date:	Mon, 21 May 2007 13:04:06 +0200
From:	Folkert van Heusden <folkert@...heusden.com>
To:	Andrea Righi <righiandr@...rs.sourceforge.net>
Cc:	Andi Kleen <ak@...e.de>, Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Eric Dumazet <dada1@...mosbay.com>,
	Rik van Riel <riel@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: signals logged / [RFC] log out-of-virtual-memory events

> >> +	switch(sig) {
> >> +	case SIGQUIT: 
...
> >> +	case SIGSTKFLT:
> > 
> > Unconditional? That's definitely a very bad idea. If anything only unhandled
> > signals should be printed this way because some programs use them internally. 
> > But I think your list is far too long anyways.
> 
> Maybe you could use somthing similar to unhandled_signal() in
> arch/x86_64/mm/fault.c, but I agree that the list seems a bit too long...

What about the following enhancement: I check with sig_fatal if it would
kill the process and only then emit a message. So when an application
takes care itself of handling it nothing is printed.

Signed-off by: Folkert van Heusden <folkert@...heusden.com>

--- kernel/signal.c.org	2007-05-20 22:47:13.000000000 +0200
+++ kernel/signal.c	2007-05-21 12:59:52.000000000 +0200
@@ -739,6 +739,8 @@
 	struct sigqueue * q = NULL;
 	int ret = 0;
 
+	/* emit some logging for unhandled signals
+	 */
+	if (sig_fatal(t, sig))
+	{
+		printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n",
+		sig, t -> pid, t -> uid, t -> gid, t -> comm);
+	}
+
 	/*
 	 * fast-pathed signals for kernel-internal things like SIGSTOP
 	 * or SIGKILL.

of course, this can also be limited to only the interesting signals:

Signed-off by: Folkert van Heusden <folkert@...heusden.com>

--- kernel/signal.c.org	2007-05-20 22:47:13.000000000 +0200
+++ kernel/signal.c	2007-05-21 12:59:52.000000000 +0200
@@ -739,6 +739,28 @@
 	struct sigqueue * q = NULL;
 	int ret = 0;
 
+	/* emit some logging for nasty signals
+	 * especially SIGSEGV and friends aught to be looked at when happening
+	 */
+	switch(sig) {
+	case SIGQUIT: 
+	case SIGILL: 
+	case SIGTRAP:
+	case SIGABRT: 
+	case SIGBUS: 
+	case SIGFPE:
+	case SIGSEGV: 
+	case SIGXCPU: 
+	case SIGXFSZ:
+	case SIGSYS: 
+	case SIGSTKFLT:
+		if (sig_fatal(t, sig))
+		{
+			printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n",
+			sig, t -> pid, t -> uid, t -> gid, t -> comm);
+		}
+	}
+
 	/*
 	 * fast-pathed signals for kernel-internal things like SIGSTOP
 	 * or SIGKILL.


Folkert van Heusden

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