Re: x86-64: int3 no longer causes SIGTRAP in 2.6.10

[Prasanna S Panchamukhi <prasanna@in.ibm.com>]

Hi Andi,

> > > -	set_intr_gate(3,&int3);
> > > +	set_system_gate(3,&int3);
> > >  	set_system_gate(4,&overflow);	/* int4-5 can be called from all */
> > >  	set_system_gate(5,&bounds);
> > >  	set_intr_gate(6,&invalid_op);
> > > Index: linux/arch/x86_64/kernel/kprobes.c

This looks good to me. Andi do you see any thing that will cause premption
 by moving int3 to system gate.

> > > ===================================================================
> > > --- linux.orig/arch/x86_64/kernel/kprobes.c	2005-01-04 12:12:39.%N +0100
> > > +++ linux/arch/x86_64/kernel/kprobes.c	2005-01-18 02:46:05.%N +0100
> > > @@ -297,6 +297,8 @@
> > >  	struct die_args *args = (struct die_args *)data;
> > >  	switch (val) {
> > >  	case DIE_INT3:
> > > +		if (args->regs->cs & 3)
> > > +			return NOTIFY_DONE;

This will prevent handling of userspace probes (privilege level 3). The 
kprobe_exception handler will return from here and registered user space probe
handler won't be called.

Thanks
Prasanna
-- 

Prasanna S Panchamukhi
Linux Technology Center
India Software Labs, IBM Bangalore
Ph: 91-80-25044636
<prasanna@in.ibm.com>