Re: [BUGFIX PATCH] kprobes/x86: Remove IRQ disabling from jprobe handlers

[Masami Hiramatsu]

On Tue, 3 Oct 2017 11:33:44 +0200
Ingo Molnar <mingo@xxxxxxxxxx> wrote:

> 
> * Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> 
> > Jprobe actually doesn't need to disable IRQs while calling
> > handlers, because Documentation/kprobes.txt says:
> > 
> > -----
> >  Probe handlers are run with preemption disabled.  Depending on the
> >  architecture and optimization state, handlers may also run with
> >  interrupts disabled (e.g., kretprobe handlers and optimized kprobe
> >  handlers run without interrupt disabled on x86/x86-64).
> > -----
> > 
> > So let's remove IRQ disabling from jprobes too.
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > ---
> >  arch/x86/kernel/kprobes/core.c |    2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> > index b48e0efd668e..bd36f3c33cd0 100644
> > --- a/arch/x86/kernel/kprobes/core.c
> > +++ b/arch/x86/kernel/kprobes/core.c
> > @@ -1099,8 +1099,6 @@ int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
> >  	 * raw stack chunk with redzones:
> >  	 */
> >  	__memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr, MIN_STACK_SIZE(addr));
> > -	regs->flags &= ~X86_EFLAGS_IF;
> > -	trace_hardirqs_off();
> >  	regs->ip = (unsigned long)(jp->entry);
> >  
> >  	/*
> 
> Could you please also do a patch that disables jprobes permanently, in preparation 
> of eventually removing them later?

Would you mean introducing CONFIG_JPROBE_API and cut APIs out,
or just adding "__deprecated" for each API?

Thank you,

> 
> Thanks,
> 
> 	Ingo


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>