Messages in this thread | | | Date | Mon, 4 Apr 2016 18:16:34 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/extable: Add a comment about early exception handlers |
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On Mon, Apr 04, 2016 at 08:46:22AM -0700, Andy Lutomirski wrote: > Borislav asked for a comment explaining why all exception handlers are > allowed early. > > Signed-off-by: Andy Lutomirski <luto@kernel.org> > --- > arch/x86/mm/extable.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c > index 98b5f45d9d79..36fe03bc81ee 100644 > --- a/arch/x86/mm/extable.c > +++ b/arch/x86/mm/extable.c > @@ -132,6 +132,20 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr) > if (regs->cs != __KERNEL_CS) > goto fail; > > + /* > + * The full exception fixup machinery is available as soon as > + * the early IDT is loaded. This means that it is the > + * responsibility of extable users to either function correctly > + * when handlers are invoked early or to simply avoid causing > + * exceptions before they're ready to handle them. > + * > + * This is better than filtering which handlers can be used, > + * because refusing to call a handler here is guaranteed to > + * result in a hard-to-debug panic. > + * > + * Keep in mind that not all vectors actually get here. Early > + * fage faults, for example, are special. > + */ > if (fixup_exception(regs, trapnr)) > return; > > --
Thanks!
Reviewed-by: Borislav Petkov <bp@suse.de>
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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