From: Jason Baron <jbaron@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
mathieu.desnoyers@polymtl.ca, hpa@zytor.com, tglx@linutronix.de,
andi@firstfloor.org, roland@redhat.com, rth@redhat.com,
mhiramat@redhat.com, fweisbec@gmail.com
Subject: Re: [PATCH 3/5] jump label: x86 support
Date: Mon, 22 Mar 2010 16:40:48 -0400 [thread overview]
Message-ID: <20100322204048.GD2278@redhat.com> (raw)
In-Reply-To: <1269276025.2957.5.camel@gandalf.stny.rr.com>
On Mon, Mar 22, 2010 at 12:40:25PM -0400, Steven Rostedt wrote:
> > add x86 support for jump label. I'm keeping this patch separate so its clear to
> > arch maintainers what was required for x86 support this new feature. hopefully,
> > it wouldn't be too painful for other arches.
> >
> > Signed-off-by: Jason Baron <jbaron@redhat.com>
>
>
> > +#ifdef __HAVE_ARCH_JUMP_LABEL
> > +
> > +# ifdef CONFIG_X86_64
> > +# define JUMP_LABEL_NOP P6_NOP5
> > +# else
> > +# define JUMP_LABEL_NOP ".byte 0xe9 \n\t .long 0\n\t"
> > +# endif
>
> Are you sure P6_NOP5 can't happen on non 64bit? Just because it is not
> configured does not mean that the CPU can not handle it. Look at the
> code I did in arch/x86/kernel/ftrace.c to determine what nop to use.
> Maybe we can make that generic and have at boot up, the kernel determine
> a proper 5byte nop.
>
indeed, i've looked at the ftrace nop code...I think was concerned that
I would need a baseline nop that would work for all boxes. But I guess a
jmp + 5 would be it?
-Jason
next prev parent reply other threads:[~2010-03-22 20:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-22 16:07 [PATCH 0/5] jump label v5 Jason Baron
2010-03-22 16:07 ` [PATCH 1/5] jump label: notifier atomic call chain notrace Jason Baron
2010-03-22 17:55 ` Masami Hiramatsu
2010-03-22 16:07 ` [PATCH 2/5] jump label: base patch Jason Baron
2010-03-22 20:04 ` Steven Rostedt
2010-03-22 21:01 ` Avi Kivity
2010-03-26 21:30 ` Masami Hiramatsu
2010-03-22 16:07 ` [PATCH 3/5] jump label: x86 support Jason Baron
2010-03-22 16:40 ` Steven Rostedt
2010-03-22 20:40 ` Jason Baron [this message]
2010-03-22 16:07 ` [PATCH 4/5] jump label: tracepoint support Jason Baron
2010-03-22 16:43 ` Steven Rostedt
2010-03-22 20:44 ` Jason Baron
2010-03-22 16:07 ` [PATCH 5/5] jump label: add module support Jason Baron
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