Messages in this thread | | | Date | Mon, 22 Mar 2010 16:40:48 -0400 | From | Jason Baron <> | Subject | Re: [PATCH 3/5] jump label: x86 support |
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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
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