Re: [PATCH v12 10/13] arch/x86: enable task isolation functionality

[Chris Metcalf]

On 5/18/2016 12:23 PM, Peter Zijlstra wrote:
> On Tue, Apr 05, 2016 at 01:38:39PM -0400, Chris Metcalf wrote:
> > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> > index 06cbe25861f1..b02205085571 100644
> > --- a/arch/x86/kernel/traps.c
> > +++ b/arch/x86/kernel/traps.c
> > @@ -36,6 +36,7 @@
> >   #include <linux/mm.h>
> >   #include <linux/smp.h>
> >   #include <linux/io.h>
> > +#include <linux/isolation.h>
> >   
> >   #ifdef CONFIG_EISA
> >   #include <linux/ioport.h>
> > @@ -382,6 +383,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
> >   	case 2:	/* Bound directory has invalid entry. */
> >   		if (mpx_handle_bd_fault())
> >   			goto exit_trap;
> > +		task_isolation_exception("bounds check");
> >   		break; /* Success, it was handled */
> >   	case 1: /* Bound violation. */
> >   		info = mpx_generate_siginfo(regs);
> > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> > index 5ce1ed02f7e8..025e9d2850c1 100644
> > --- a/arch/x86/mm/fault.c
> > +++ b/arch/x86/mm/fault.c
> > @@ -14,6 +14,7 @@
> >   #include <linux/prefetch.h>		/* prefetchw			*/
> >   #include <linux/context_tracking.h>	/* exception_enter(), ...	*/
> >   #include <linux/uaccess.h>		/* faulthandler_disabled()	*/
> > +#include <linux/isolation.h>		/* task_isolation_exception	*/
> >   
> >   #include <asm/cpufeature.h>		/* boot_cpu_has, ...		*/
> >   #include <asm/traps.h>			/* dotraplinkage, ...		*/
> > @@ -1259,6 +1260,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
> >   		local_irq_enable();
> >   		error_code |= PF_USER;
> >   		flags |= FAULT_FLAG_USER;
> > +		task_isolation_exception("page fault at %#lx", address);
> >   	} else {
> >   		if (regs->flags & X86_EFLAGS_IF)
> >   			local_irq_enable();
>
> That seems to miss a whole bunch of exceptions... what up?

We only need to do an explicit call in the case where the exception does NOT
result in a signal, since a signal is something that will be really obvious to
the application in any case.  So it's just stuff like handled page faults,
handled bounds checks for x86, handled unaligned load/store for tilegx, etc.

--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com