[RFC] log out-of-virtual-memory events

[RFC] log out-of-virtual-memory events

[Andrea Righi]

I'm looking for a way to keep track of the processes that fail to allocate new
virtual memory. What do you think about the following approach (untested)?

--

Print informations about the processes that fail to allocate virtual memory.

Signed-off-by: Andrea Righi <a.righi@cineca.it>

diff -urpN linux-2.6.21/mm/mmap.c linux-2.6.21-vm-log-enomem/mm/mmap.c
--- linux-2.6.21/mm/mmap.c	2007-04-26 05:08:32.000000000 +0200
+++ linux-2.6.21-vm-log-enomem/mm/mmap.c	2007-05-17 18:05:39.000000000 +0200
@@ -77,6 +77,26 @@ int sysctl_max_map_count __read_mostly =
 atomic_t vm_committed_space = ATOMIC_INIT(0);
 
 /*
+ * Print current process informations when it fails to allocate new virtual
+ * memory.
+ */
+static inline void log_vm_enomem(void)
+{
+	unsigned long total_vm = 0;
+	struct mm_struct *mm;
+
+	task_lock(current);
+	mm = current->mm;
+	if (mm)
+		total_vm = mm->total_vm;
+	task_unlock(current);
+
+	printk(KERN_INFO
+	       "out of virtual memory for process %d (%s): total_vm=%lu, uid=%d\n",
+	       current->pid, current->comm, total_vm, current->uid);
+}
+
+/*
  * Check that a process has enough memory to allocate a new virtual
  * mapping. 0 means there is enough memory for the allocation to
  * succeed and -ENOMEM implies there is not.
@@ -175,6 +195,7 @@ int __vm_enough_memory(long pages, int c
 		return 0;
 error:
 	vm_unacct_memory(pages);
+	log_vm_enomem();
 
 	return -ENOMEM;
 }

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Re: [RFC] log out-of-virtual-memory events

[Rik van Riel]

Andrea Righi wrote:
> I'm looking for a way to keep track of the processes that fail to allocate new
> virtual memory. What do you think about the following approach (untested)?

Looks like an easy way for users to spam syslogd over and
over and over again.

At the very least, shouldn't this be dependant on print_fatal_signals?

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

[Jan Engelhardt]

On May 17 2007 14:22, Rik van Riel wrote:
> Andrea Righi wrote:
>> I'm looking for a way to keep track of the processes that fail to allocate
>> new
>> virtual memory. What do you think about the following approach (untested)?
>
> Looks like an easy way for users to spam syslogd over and
> over and over again.
>
> At the very least, shouldn't this be dependant on print_fatal_signals?

Speaking of signals, everytime I get a segfault (or force one with a test
program) on x86_64, the kernel prints to dmesg:

fail[22278]: segfault at 0000000000000000 rip 00000000004004b8 rsp
00007ffff7ecda50 error 6

I do not see such on i386, so why for x86_64?


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

[Andi Kleen]

> I do not see such on i386, so why for x86_64?

So that you know that one of your programs crashed. That's a feature.

-Andi

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

[Jan Engelhardt]

On May 18 2007 13:47, Andi Kleen wrote:
>
>> I do not see such on i386, so why for x86_64?
>
>So that you know that one of your programs crashed. That's a feature.

This feature could be handy for i386 too.


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

[Andrea Righi]

Jan Engelhardt wrote:
> On May 18 2007 13:47, Andi Kleen wrote:
>>> I do not see such on i386, so why for x86_64?
>> So that you know that one of your programs crashed. That's a feature.
> 
> This feature could be handy for i386 too.
> 

What about your /proc/sys/kernel/print-fatal-signals? it must be set to 1 to
enable that feature.

-Andrea

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

[Jan Engelhardt]

On May 19 2007 11:35, Andrea Righi wrote:
>Jan Engelhardt wrote:
>> On May 18 2007 13:47, Andi Kleen wrote:
>>>> I do not see such on i386, so why for x86_64?
>>> So that you know that one of your programs crashed. That's a feature.
>> 
>> This feature could be handy for i386 too.
>> 
>
>What about your /proc/sys/kernel/print-fatal-signals? it must be set to 1 to
>enable that feature.

That file does not exist on versions
  2.6.18 <= version <= 2.6.20


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

[Andrea Righi]

Jan Engelhardt wrote:
> On May 19 2007 11:35, Andrea Righi wrote:
>> Jan Engelhardt wrote:
>>> On May 18 2007 13:47, Andi Kleen wrote:
>>>>> I do not see such on i386, so why for x86_64?
>>>> So that you know that one of your programs crashed. That's a feature.
>>> This feature could be handy for i386 too.
>>>
>> What about your /proc/sys/kernel/print-fatal-signals? it must be set to 1 to
>> enable that feature.
> 
> That file does not exist on versions
>   2.6.18 <= version <= 2.6.20
> 

This means that you must apply the print_fatal_signals patch...

-Andrea

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

[Folkert van Heusden]

> >> I do not see such on i386, so why for x86_64?
> >So that you know that one of your programs crashed. That's a feature.
> This feature could be handy for i386 too.

Since 2.6.18.2 I use this patch. With 2.6.21.1 it still applies altough
with a small offsets. Works like a charm.


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

--- linux-2.6.18.2/kernel/signal.c      2006-11-04 02:33:58.000000000 +0100
+++ linux-2.6.18.2.new/kernel/signal.c  2006-11-17 15:59:13.000000000 +0100
@@ -706,6 +706,15 @@
        struct sigqueue * q = NULL;
        int ret = 0;

+       if (sig == SIGQUIT || sig == SIGILL  || sig == SIGTRAP ||
+           sig == SIGABRT || sig == SIGBUS  || sig == SIGFPE  ||
+           sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ ||
+           sig == SIGSYS  || sig == SIGSTKFLT)
+       {
+               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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Re: signals logged / [RFC] log out-of-virtual-memory events

[Eric Dumazet]

Folkert van Heusden a ecrit :
>>>> I do not see such on i386, so why for x86_64?
>>> So that you know that one of your programs crashed. That's a feature.
>> This feature could be handy for i386 too.
> 
> Since 2.6.18.2 I use this patch. With 2.6.21.1 it still applies altough
> with a small offsets. Works like a charm.
> 
> 
> Signed-off by: Folkert van Heusden <folkert@vanheusden.com>
> 
> --- linux-2.6.18.2/kernel/signal.c      2006-11-04 02:33:58.000000000 +0100
> +++ linux-2.6.18.2.new/kernel/signal.c  2006-11-17 15:59:13.000000000 +0100
> @@ -706,6 +706,15 @@
>         struct sigqueue * q = NULL;
>         int ret = 0;
> 
> +       if (sig == SIGQUIT || sig == SIGILL  || sig == SIGTRAP ||
> +           sig == SIGABRT || sig == SIGBUS  || sig == SIGFPE  ||
> +           sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ ||
> +           sig == SIGSYS  || sig == SIGSTKFLT)
> +       {
> +               printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n",
> +                       sig, t -> pid, t -> uid, t -> gid, t -> comm);
> +       }
> +

Please check line 219 of Documentation/CodingStyle, Section 3.1: Spaces

	and no space around the '.' and "->" structure member operators.

Thank you

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

[Folkert van Heusden]

> >>>>I do not see such on i386, so why for x86_64?
> >>>So that you know that one of your programs crashed. That's a feature.
> >>This feature could be handy for i386 too.
> >Since 2.6.18.2 I use this patch. With 2.6.21.1 it still applies altough
> >with a small offsets. Works like a charm.
> >
> >Signed-off by: Folkert van Heusden <folkert@vanheusden.com>
> >--- linux-2.6.18.2/kernel/signal.c      2006-11-04 02:33:58.000000000 +0100
> >+++ linux-2.6.18.2.new/kernel/signal.c  2006-11-17 15:59:13.000000000 +0100
...
> >+                       sig, t -> pid, t -> uid, t -> gid, t -> comm);
> 
> Please check line 219 of Documentation/CodingStyle, Section 3.1: Spaces
> 	and no space around the '.' and "->" structure member operators.

New version without the spaces around '->' and a nice 'unlikely' added. 

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

--- linux-2.6.18.2/kernel/signal.c	2006-11-04 02:33:58.000000000 +0100
+++ linux-2.6.18.2.new/kernel/signal.c	2006-11-17 15:59:13.000000000 +0100
@@ -706,6 +706,15 @@
 	struct sigqueue * q = NULL;
 	int ret = 0;
 
+	if (unlikely(sig == SIGQUIT || sig == SIGILL  || sig == SIGTRAP ||
+	    sig == SIGABRT || sig == SIGBUS  || sig == SIGFPE  ||
+	    sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ ||
+	    sig == SIGSYS  || sig == SIGSTKFLT))
+	{
+		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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Re: signals logged / [RFC] log out-of-virtual-memory events

[Stephen Hemminger]

On Sun, 20 May 2007 13:21:11 +0200
Folkert van Heusden <folkert@vanheusden.com> wrote:

> > >>>>I do not see such on i386, so why for x86_64?
> > >>>So that you know that one of your programs crashed. That's a feature.
> > >>This feature could be handy for i386 too.
> > >Since 2.6.18.2 I use this patch. With 2.6.21.1 it still applies altough
> > >with a small offsets. Works like a charm.
> > >
> > >Signed-off by: Folkert van Heusden <folkert@vanheusden.com>
> > >--- linux-2.6.18.2/kernel/signal.c      2006-11-04 02:33:58.000000000 +0100
> > >+++ linux-2.6.18.2.new/kernel/signal.c  2006-11-17 15:59:13.000000000 +0100
> ...
> > >+                       sig, t -> pid, t -> uid, t -> gid, t -> comm);
> > 
> > Please check line 219 of Documentation/CodingStyle, Section 3.1: Spaces
> > 	and no space around the '.' and "->" structure member operators.
> 
> New version without the spaces around '->' and a nice 'unlikely' added. 
> 
> Signed-off by: Folkert van Heusden <folkert@vanheusden.com>
> 
> --- linux-2.6.18.2/kernel/signal.c	2006-11-04 02:33:58.000000000 +0100
> +++ linux-2.6.18.2.new/kernel/signal.c	2006-11-17 15:59:13.000000000 +0100
> @@ -706,6 +706,15 @@
>  	struct sigqueue * q = NULL;
>  	int ret = 0;
>  
> +	if (unlikely(sig == SIGQUIT || sig == SIGILL  || sig == SIGTRAP ||
> +	    sig == SIGABRT || sig == SIGBUS  || sig == SIGFPE  ||
> +	    sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ ||
> +	    sig == SIGSYS  || sig == SIGSTKFLT))
> +	{
> +		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
> 

Would turning that into a switch() generate better code.

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

[Folkert van Heusden]

> > > >>>>I do not see such on i386, so why for x86_64?
> > > >>>So that you know that one of your programs crashed. That's a feature.
> > > >>This feature could be handy for i386 too.
> > > >Since 2.6.18.2 I use this patch. With 2.6.21.1 it still applies altough
> > > >with a small offsets. Works like a charm.
> > > >
> > > >Signed-off by: Folkert van Heusden <folkert@vanheusden.com>
> > > >--- linux-2.6.18.2/kernel/signal.c      2006-11-04 02:33:58.000000000 +0100
> > > >+++ linux-2.6.18.2.new/kernel/signal.c  2006-11-17 15:59:13.000000000 +0100
> > ...
> > > >+                       sig, t -> pid, t -> uid, t -> gid, t -> comm);
> > > 
> > > Please check line 219 of Documentation/CodingStyle, Section 3.1: Spaces
> > > 	and no space around the '.' and "->" structure member operators.
> > New version without the spaces around '->' and a nice 'unlikely' added. 
> > Signed-off by: Folkert van Heusden <folkert@vanheusden.com>
> > --- linux-2.6.18.2/kernel/signal.c	2006-11-04 02:33:58.000000000 +0100
> > +++ linux-2.6.18.2.new/kernel/signal.c	2006-11-17 15:59:13.000000000 +0100
> > @@ -706,6 +706,15 @@
> >  	struct sigqueue * q = NULL;
> >  	int ret = 0;
> >  
> > +	if (unlikely(sig == SIGQUIT || sig == SIGILL  || sig == SIGTRAP ||
> > +	    sig == SIGABRT || sig == SIGBUS  || sig == SIGFPE  ||
> > +	    sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ ||
> > +	    sig == SIGSYS  || sig == SIGSTKFLT))
> > +	{
> > +		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.
> 
> Would turning that into a switch() generate better code.

Doubt it: in the worst case you still nee to check for each possibility.
Furthermore a.f.a.i.k. with switch you cannot do 'unlinkely()'.


Folkert van Heusden

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

[Jan Engelhardt]

On May 20 2007 18:12, Folkert van Heusden wrote:
>> >  
>> > +	if (unlikely(sig == SIGQUIT || sig == SIGILL  || sig == SIGTRAP ||
>> > +	    sig == SIGABRT || sig == SIGBUS  || sig == SIGFPE  ||
>> > +	    sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ ||
>> > +	    sig == SIGSYS  || sig == SIGSTKFLT))
>> > +	{
>> > +		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.
>> 
>> Would turning that into a switch() generate better code.

Yes, this time.

>Doubt it: in the worst case you still nee to check for each possibility.
>Furthermore a.f.a.i.k. with switch you cannot do 'unlinkely()'.

With if(), it generates a ton of "CMP, JE" instructions.
With switch(), I would assume gcc transforms it into using
a jump table (aka "JMP [table+sig]")

I tried it: with switch(), gcc transforms this into a
bitmap comparison ("MOV eax, 1; SHL eax, sig; TEST eax, 0x830109f8"),
which seems even cheaper than a jump table.


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

[Folkert van Heusden]

> >> >  
> >> > +	if (unlikely(sig == SIGQUIT || sig == SIGILL  || sig == SIGTRAP ||
> >> > +	    sig == SIGABRT || sig == SIGBUS  || sig == SIGFPE  ||
> >> > +	    sig == SIGSEGV || sig == SIGXCPU || sig == SIGXFSZ ||
> >> > +	    sig == SIGSYS  || sig == SIGSTKFLT))
> >> > +	{
> >> > +		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.
> >> Would turning that into a switch() generate better code.
> Yes, this time.
> 
> >Doubt it: in the worst case you still nee to check for each possibility.
> >Furthermore a.f.a.i.k. with switch you cannot do 'unlinkely()'.
> 
> With if(), it generates a ton of "CMP, JE" instructions.
> With switch(), I would assume gcc transforms it into using
> a jump table (aka "JMP [table+sig]")
> I tried it: with switch(), gcc transforms this into a
> bitmap comparison ("MOV eax, 1; SHL eax, sig; TEST eax, 0x830109f8"),
> which seems even cheaper than a jump table.

Ok, here's the new patch against 2.6.21.1:

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

--- kernel/signal.c.org	2007-05-20 22:47:13.000000000 +0200
+++ kernel/signal.c	2007-05-20 22:54:17.000000000 +0200
@@ -739,6 +739,25 @@
 	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:
+		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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Re: signals logged / [RFC] log out-of-virtual-memory events

[Andi Kleen]

> +	switch(sig) {
> +	case SIGQUIT: 
> +	case SIGILL: 
> +	case SIGTRAP:
> +	case SIGABRT: 
> +	case SIGBUS: 
> +	case SIGFPE:
> +	case SIGSEGV: 
> +	case SIGXCPU: 
> +	case SIGXFSZ:
> +	case SIGSYS: 
> +	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.

-Andi

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

[Folkert van Heusden]

> > +	switch(sig) {
> > +	case SIGQUIT: 
> > +	case SIGILL: 
> > +	case SIGTRAP:
> > +	case SIGABRT: 
> > +	case SIGBUS: 
> > +	case SIGFPE:
> > +	case SIGSEGV: 
> > +	case SIGXCPU: 
> > +	case SIGXFSZ:
> > +	case SIGSYS: 
> > +	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. 

Use these signals internally? Afaik these are fatal, stopping the
process. So using them internally would be a little tricky.

> But I think your list is far too long anyways.

So, which ones would you like to have removed then?


Folkert van Heusden

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

[Folkert van Heusden]

> > > +	switch(sig) {
> > > +	case SIGQUIT: 
> > > +	case SIGILL: 
> > > +	case SIGTRAP:
> > > +	case SIGABRT: 
> > > +	case SIGBUS: 
> > > +	case SIGFPE:
> > > +	case SIGSEGV: 
> > > +	case SIGXCPU: 
> > > +	case SIGXFSZ:
> > > +	case SIGSYS: 
> > > +	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. 
> Use these signals internally? Afaik these are fatal, stopping the
> process. So using them internally would be a little tricky.
> > But I think your list is far too long anyways.
> 
> So, which ones would you like to have removed then?

(and why, of course, to enlighten me: some are educated guesses)


Folkert van Heusden

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

[Andi Kleen]

On Sun, May 20, 2007 at 11:20:36PM +0200, Folkert van Heusden wrote:
> > > +	switch(sig) {
> > > +	case SIGQUIT: 
> > > +	case SIGILL: 
> > > +	case SIGTRAP:
> > > +	case SIGABRT: 
> > > +	case SIGBUS: 
> > > +	case SIGFPE:
> > > +	case SIGSEGV: 
> > > +	case SIGXCPU: 
> > > +	case SIGXFSZ:
> > > +	case SIGSYS: 
> > > +	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. 
> 
> Use these signals internally? Afaik these are fatal, stopping the
> process. So using them internally would be a little tricky.

All of them are catchable.

> 
> > But I think your list is far too long anyways.
> 
> So, which ones would you like to have removed then?

SIGFPE at least and the accounting signals are dubious too. SIGQUIT can
be also relatively common.

-Andi

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

[Jeff Dike]

On Mon, May 21, 2007 at 12:24:22AM +0200, Andi Kleen wrote:
> > > But I think your list is far too long anyways.
> > 
> > So, which ones would you like to have removed then?
> 
> SIGFPE at least and the accounting signals are dubious too. SIGQUIT can
> be also relatively common.

And SIGSEGV and SIGBUS - UML catches these internally and handles them.

				Jeff

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

[Andrea Righi]

Andi Kleen wrote:
>> +	switch(sig) {
>> +	case SIGQUIT: 
>> +	case SIGILL: 
>> +	case SIGTRAP:
>> +	case SIGABRT: 
>> +	case SIGBUS: 
>> +	case SIGFPE:
>> +	case SIGSEGV: 
>> +	case SIGXCPU: 
>> +	case SIGXFSZ:
>> +	case SIGSYS: 
>> +	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.
> 
> -Andi
> 

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...

-Andrea

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

[Folkert van Heusden]

> >> +	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@vanheusden.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@vanheusden.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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Re: signals logged / [RFC] log out-of-virtual-memory events

[Jan Engelhardt]

On May 21 2007 13:04, Folkert van Heusden wrote:
>
>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.

>+	/* emit some logging for unhandled signals
>+	 */
>+	if (sig_fatal(t, sig))

Not unhandled_signal()?

>+	{

if (sig_fatal(t, sig)) {

>+		printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n",

s/send/sent/;

>+		sig, t -> pid, t -> uid, t -> gid, t -> comm);

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@vanheusden.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.
>



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

[Folkert van Heusden]

> >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.
> >+	/* emit some logging for unhandled signals
> >+	 */
> >+	if (sig_fatal(t, sig))
> Not unhandled_signal()?

Can we already use that one in send_signal? As the signal needs to be
send first I think before we know if it was handled or not? sig_fatal
checks if the handler is set to default - which is it is not taken care
of.

> >+	{
> if (sig_fatal(t, sig)) {
> >+		printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n",
> s/send/sent/;
> >+		sig, t -> pid, t -> uid, t -> gid, t -> comm);
> t->pid, t->uid, t->gid, t->comm);


Description:
This patch adds code to the signal-sender making it log a message when
an unhandled fatal signal will be delivered.

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

--- kernel/signal.c.org	2007-05-20 22:47:13.000000000 +0200
+++ kernel/signal.c	2007-05-21 14:46:05.000000000 +0200
@@ -739,6 +739,12 @@
 	struct sigqueue * q = NULL;
 	int ret = 0;
 
+	/* unhandled fatal signals are logged */
+	if (sig_fatal(t, sig)) {
+		printk(KERN_WARNING "Sig %d sent 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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Re: signals logged / [RFC] log out-of-virtual-memory events

[Andrea Righi]

Folkert van Heusden wrote:
>>> 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.
>>> +	/* emit some logging for unhandled signals
>>> +	 */
>>> +	if (sig_fatal(t, sig))
>> Not unhandled_signal()?
> 
> Can we already use that one in send_signal? As the signal needs to be
> send first I think before we know if it was handled or not? sig_fatal
> checks if the handler is set to default - which is it is not taken care
> of.

What about ptrace()'d processes? I don't think we should log signals for them...

-Andrea

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

[Folkert van Heusden]

> >>> 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.
> >>> +	/* emit some logging for unhandled signals
> >>> +	 */
> >>> +	if (sig_fatal(t, sig))
> >> Not unhandled_signal()?
> > Can we already use that one in send_signal? As the signal needs to be
> > send first I think before we know if it was handled or not? sig_fatal
> > checks if the handler is set to default - which is it is not taken care
> > of.
> What about ptrace()'d processes? I don't think we should log signals for them...

Why not?


Folkert van Heusden

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

[Andrea Righi]

Folkert van Heusden wrote:
>>>>> 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.
>>>>> +	/* emit some logging for unhandled signals
>>>>> +	 */
>>>>> +	if (sig_fatal(t, sig))
>>>> Not unhandled_signal()?
>>> Can we already use that one in send_signal? As the signal needs to be
>>> send first I think before we know if it was handled or not? sig_fatal
>>> checks if the handler is set to default - which is it is not taken care
>>> of.
>> What about ptrace()'d processes? I don't think we should log signals for them...
> 
> Why not?

Maybe sometimes it's useful, maybe not, but I suppose that usually only the
controlling process should care about the critical signals received by the
controlled process. I simply don't think it should be a system issue. For
example I wouldn't like to have a lot of messages in the kernel logs just
because I'm debugging some segfaulting programs with gdb.

-Andrea

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

[Satyam Sharma]

On 5/21/07, Folkert van Heusden <folkert@vanheusden.com> wrote:
> > >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.
> > >+    /* emit some logging for unhandled signals
> > >+     */
> > >+    if (sig_fatal(t, sig))
> > Not unhandled_signal()?
>
> Can we already use that one in send_signal? As the signal needs to be
> send first I think before we know if it was handled or not? sig_fatal
> checks if the handler is set to default - which is it is not taken care
> of.
>
> > >+    {
> > if (sig_fatal(t, sig)) {
> > >+            printk(KERN_WARNING "Sig %d send to %d owned by %d.%d (%s)\n",
> > s/send/sent/;
> > >+            sig, t -> pid, t -> uid, t -> gid, t -> comm);
> > t->pid, t->uid, t->gid, t->comm);
>
>
> Description:
> This patch adds code to the signal-sender making it log a message when
> an unhandled fatal signal will be delivered.

Gargh ... why does this want to be in the *kernel*'s logs? In any case, can
you please make this KERN_INFO (or lower) instead of KERN_WARNING.

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

[Folkert van Heusden]

> >> >+    {
> >> if (sig_fatal(t, sig)) {
> >> >+            printk(KERN_WARNING "Sig %d send to %d owned by %d.%d 
> >(%s)\n",
> >> s/send/sent/;
> >> >+            sig, t -> pid, t -> uid, t -> gid, t -> comm);
> >> t->pid, t->uid, t->gid, t->comm);
> >
> 
> Gargh ... why does this want to be in the *kernel*'s logs? In any case, can
> you please make this KERN_INFO (or lower) instead of KERN_WARNING.

Description:
This patch adds code to the signal-sender making it log a message when
an unhandled fatal signal will be delivered.

Signed-of by: Folkert van Heusden <folkert@vanheusden.com

--- kernel/signal.c.org	2007-05-20 22:47:13.000000000 +0200
+++ kernel/signal.c	2007-05-21 14:46:05.000000000 +0200
@@ -739,6 +739,12 @@
 	struct sigqueue * q = NULL;
 	int ret = 0;
 
+	/* unhandled fatal signals are logged */
+	if (sig_fatal(t, sig)) {
+		printk(KERN_INFO "Sig %d sent 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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Re: signals logged / [RFC] log out-of-virtual-memory events

[Folkert van Heusden]

> > >> >+    {
> > >> if (sig_fatal(t, sig)) {
> > >> >+            printk(KERN_WARNING "Sig %d send to %d owned by %d.%d 
> > >(%s)\n",
> > >> s/send/sent/;
> > >> >+            sig, t -> pid, t -> uid, t -> gid, t -> comm);
> > >> t->pid, t->uid, t->gid, t->comm);
> > >
> > 
> > Gargh ... why does this want to be in the *kernel*'s logs? In any case, can
> > you please make this KERN_INFO (or lower) instead of KERN_WARNING.
> Description:
> This patch adds code to the signal-sender making it log a message when
> an unhandled fatal signal will be delivered.

New version. This one also informs the user about the sende pid/uid of
the signal (when applicable).

Signed-of by: Folkert van Heusden <folkert@vanheusden.com

--- linux/kernel/signal.c.org	2007-05-20 22:47:13.000000000 +0200
+++ linux/kernel/signal.c	2007-06-10 00:21:31.000000000 +0200
@@ -739,6 +739,18 @@
 	struct sigqueue * q = NULL;
 	int ret = 0;
 
+	/* unhandled fatal signals are logged */
+	if (sig_fatal(t, sig)) {
+		if (is_si_special(info))
+			printk(KERN_INFO "Sig %d sent to %d owned by %d.%d (%s)\n",
+				sig, t->pid, t->uid, t->gid, t->comm);
+		else
+			printk(KERN_INFO "Sig %d sent to %d owned by %d.%d (%s), sent by pid %d, uid %d\n",
+				sig, t->pid, t->uid, t->gid, t->comm,
+				info -> _sifields._kill._pid,
+				info -> _sifields._kill._uid);
+	}
+
 	/*
 	 * fast-pathed signals for kernel-internal things like SIGSTOP
 	 * or SIGKILL.


Folkert van Heusden

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

[Jiri Kosina]

On Sun, 10 Jun 2007, Folkert van Heusden wrote:

> Signed-of by: Folkert van Heusden <folkert@vanheusden.com

This looks broken BTW.

> +			printk(KERN_INFO "Sig %d sent to %d owned by %d.%d (%s), sent by pid %d, uid %d\n",
> +				sig, t->pid, t->uid, t->gid, t->comm,
> +				info -> _sifields._kill._pid,
> +				info -> _sifields._kill._uid);

Am I the only one whose eyes are hurt by these spaces?

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

[Jan Engelhardt]

On Jun 10 2007 22:06, Jiri Kosina wrote:
>On Sun, 10 Jun 2007, Folkert van Heusden wrote:
>
>> Signed-of by: Folkert van Heusden <folkert@vanheusden.com
>
>This looks broken BTW.
>
>> +			printk(KERN_INFO "Sig %d sent to %d owned by %d.%d (%s), sent by pid %d, uid %d\n",
>> +				sig, t->pid, t->uid, t->gid, t->comm,
>> +				info -> _sifields._kill._pid,
>> +				info -> _sifields._kill._uid);
>
>Am I the only one whose eyes are hurt by these spaces?

They were discussed before already. And they were fixed up (t->uid...).
And now new ones got added. Ergh.



	Jan
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Re: [RFC] log out-of-virtual-memory events

[Andrea Righi]

Rik van Riel wrote:
> Andrea Righi wrote:
>> I'm looking for a way to keep track of the processes that fail to
>> allocate new
>> virtual memory. What do you think about the following approach
>> (untested)?
>
> Looks like an easy way for users to spam syslogd over and
> over and over again.
>
> At the very least, shouldn't this be dependant on print_fatal_signals?
>

Anyway, with print-fatal-signals enabled a user could spam syslogd too, simply
with a (char *)0 = 0 program, but we could always identify the spam attempts
logging the process uid...

In any case, I agree, it should depend on that patch...

What about adding a simple msleep_interruptible(SOME_MSECS) at the end of
log_vm_enomem() or, at least, a might_sleep() to limit the potential spam/second
rate?

-Andrea

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Re: [RFC] log out-of-virtual-memory events

[Robin Holt]

On Fri, May 18, 2007 at 09:50:03AM +0200, Andrea Righi wrote:
> Rik van Riel wrote:
> > Andrea Righi wrote:
> >> I'm looking for a way to keep track of the processes that fail to
> >> allocate new
> >> virtual memory. What do you think about the following approach
> >> (untested)?
> >
> > Looks like an easy way for users to spam syslogd over and
> > over and over again.
> >
> > At the very least, shouldn't this be dependant on print_fatal_signals?
> >
> 
> Anyway, with print-fatal-signals enabled a user could spam syslogd too, simply
> with a (char *)0 = 0 program, but we could always identify the spam attempts
> logging the process uid...
> 
> In any case, I agree, it should depend on that patch...
> 
> What about adding a simple msleep_interruptible(SOME_MSECS) at the end of
> log_vm_enomem() or, at least, a might_sleep() to limit the potential spam/second
> rate?

An msleep will slow down this process, but do nothing about slowing
down the amount of logging.  Simply fork a few more processes and all
you are doing with msleep is polluting the pid space.

What about a throttling similar to what ia64 does for floating point
assist faults (handle_fpu_swa()).  There is a thread flag to not log
the events at all.  It is rate throttled globally, but uses per cpu
variables for early exits.  This algorithm scaled well to a thousand
cpus.

I think this may be a good fit.

Good Luck,
Robin

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Re: [RFC] log out-of-virtual-memory events

[Andrea Righi]

Robin Holt wrote:
> On Fri, May 18, 2007 at 09:50:03AM +0200, Andrea Righi wrote:
>> Rik van Riel wrote:
>>> Andrea Righi wrote:
>>>> I'm looking for a way to keep track of the processes that fail to
>>>> allocate new
>>>> virtual memory. What do you think about the following approach
>>>> (untested)?
>>> Looks like an easy way for users to spam syslogd over and
>>> over and over again.
>>>
>>> At the very least, shouldn't this be dependant on print_fatal_signals?
>>>
>> Anyway, with print-fatal-signals enabled a user could spam syslogd too, simply
>> with a (char *)0 = 0 program, but we could always identify the spam attempts
>> logging the process uid...
>>
>> In any case, I agree, it should depend on that patch...
>>
>> What about adding a simple msleep_interruptible(SOME_MSECS) at the end of
>> log_vm_enomem() or, at least, a might_sleep() to limit the potential spam/second
>> rate?
> 
> An msleep will slow down this process, but do nothing about slowing
> down the amount of logging.  Simply fork a few more processes and all
> you are doing with msleep is polluting the pid space.
> 

Very true.

> What about a throttling similar to what ia64 does for floating point
> assist faults (handle_fpu_swa()).  There is a thread flag to not log
> the events at all.  It is rate throttled globally, but uses per cpu
> variables for early exits.  This algorithm scaled well to a thousand
> cpus.

Actually using printk_ratelimit() should be enough... BTW print_fatal_signals()
should use it too.

-Andrea

---

Signed-off-by: Andrea Righi <a.righi@cineca.it>

diff -urpN linux-2.6.21/mm/mmap.c linux-2.6.21-vm-log-enomem/mm/mmap.c
--- linux-2.6.21/mm/mmap.c	2007-04-26 05:08:32.000000000 +0200
+++ linux-2.6.21-vm-log-enomem/mm/mmap.c	2007-05-18 17:17:32.000000000 +0200
@@ -77,6 +77,29 @@ int sysctl_max_map_count __read_mostly =
 atomic_t vm_committed_space = ATOMIC_INIT(0);
 
 /*
+ * Print current process informations when it fails to allocate new virtual
+ * memory.
+ */
+static inline void log_vm_enomem(void)
+{
+	unsigned long total_vm = 0;
+	struct mm_struct *mm;
+
+	if (unlikely(!printk_ratelimit()))
+		return;
+
+	task_lock(current);
+	mm = current->mm;
+	if (mm)
+		total_vm = mm->total_vm;
+	task_unlock(current);
+
+	printk(KERN_INFO
+	       "out of virtual memory for process %d (%s): total_vm=%lu, uid=%d\n",
+		current->pid, current->comm, total_vm, current->uid);
+}
+
+/*
  * Check that a process has enough memory to allocate a new virtual
  * mapping. 0 means there is enough memory for the allocation to
  * succeed and -ENOMEM implies there is not.
@@ -175,6 +198,7 @@ int __vm_enough_memory(long pages, int c
 		return 0;
 error:
 	vm_unacct_memory(pages);
+	log_vm_enomem();
 
 	return -ENOMEM;
 }

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Re: [RFC] log out-of-virtual-memory events

[Andrea Righi]

Andrea Righi wrote:
> Robin Holt wrote:
>> On Fri, May 18, 2007 at 09:50:03AM +0200, Andrea Righi wrote:
>>> Rik van Riel wrote:
>>>> Andrea Righi wrote:
>>>>> I'm looking for a way to keep track of the processes that fail to
>>>>> allocate new
>>>>> virtual memory. What do you think about the following approach
>>>>> (untested)?
>>>> Looks like an easy way for users to spam syslogd over and
>>>> over and over again.
>>>>
>>>> At the very least, shouldn't this be dependant on print_fatal_signals?
>>>>
>>> Anyway, with print-fatal-signals enabled a user could spam syslogd too, simply
>>> with a (char *)0 = 0 program, but we could always identify the spam attempts
>>> logging the process uid...
>>>
>>> In any case, I agree, it should depend on that patch...
>>>
>>> What about adding a simple msleep_interruptible(SOME_MSECS) at the end of
>>> log_vm_enomem() or, at least, a might_sleep() to limit the potential spam/second
>>> rate?
>> An msleep will slow down this process, but do nothing about slowing
>> down the amount of logging.  Simply fork a few more processes and all
>> you are doing with msleep is polluting the pid space.
>>
> 
> Very true.
> 
>> What about a throttling similar to what ia64 does for floating point
>> assist faults (handle_fpu_swa()).  There is a thread flag to not log
>> the events at all.  It is rate throttled globally, but uses per cpu
>> variables for early exits.  This algorithm scaled well to a thousand
>> cpus.
> 
> Actually using printk_ratelimit() should be enough... BTW print_fatal_signals()
> should use it too.
> 

I mean, something like this...

---

Limit the rate of the printk()s in print_fatal_signal() to avoid potential DoS
problems.

Signed-off-by: Andrea Righi <a.righi@cineca.it>

diff -urpN linux-2.6.22-rc1-mm1/kernel/signal.c linux-2.6.22-rc1-mm1-limit-print_fatal_signals-rate/kernel/signal.c
--- linux-2.6.22-rc1-mm1/kernel/signal.c	2007-05-18 17:48:55.000000000 +0200
+++ linux-2.6.22-rc1-mm1-limit-print_fatal_signals-rate/kernel/signal.c	2007-05-18 17:58:13.000000000 +0200
@@ -790,6 +790,9 @@ static void print_vmas(void)
 
 static void print_fatal_signal(struct pt_regs *regs, int signr)
 {
+	if (unlikely(!printk_ratelimit()))
+		return;
+
 	printk("%s/%d: potentially unexpected fatal signal %d.\n",
 		current->comm, current->pid, signr);
 

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Re: [RFC] log out-of-virtual-memory events

[Folkert van Heusden]

> >> I'm looking for a way to keep track of the processes that fail to
> >> allocate new
> >> virtual memory. What do you think about the following approach
> >> (untested)?
> > Looks like an easy way for users to spam syslogd over and
> > over and over again.
> > At the very least, shouldn't this be dependant on print_fatal_signals?
> 
> Anyway, with print-fatal-signals enabled a user could spam syslogd too, simply
> with a (char *)0 = 0 program, but we could always identify the spam attempts
> logging the process uid...

Yeah well it's all captured by syslogd/klogd and written to a file and
diskspace is cheap.


Folkert van Heusden

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

[Mikael Pettersson]

On Sun, 20 May 2007 23:20:36 +0200, Folkert van Heusden wrote:
> > > +	switch(sig) {
> > > +	case SIGQUIT: 
> > > +	case SIGILL: 
> > > +	case SIGTRAP:
> > > +	case SIGABRT: 
> > > +	case SIGBUS: 
> > > +	case SIGFPE:
> > > +	case SIGSEGV: 
> > > +	case SIGXCPU: 
> > > +	case SIGXFSZ:
> > > +	case SIGSYS: 
> > > +	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. 
> 
> Use these signals internally? Afaik these are fatal, stopping the
> process. So using them internally would be a little tricky.

Tricky for Joe Programmer, perhaps.

I've been personally involved with writing SIGFPE-handling code
in a major telco application framework, for several different
CPU architectures and operating systems.

SIGSEGV is used by some garbage collectors, some JITs, and I believe
also some software distributed shared memory implementations.

I've heard of at least one Lisp implementation that used SIGBUS
instead of dynamic type checks in some operations (e.g. to catch
CAR of a non-CONS).

Handled signals should not be logged.

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