| Message ID | 5f1dcd6919f4a5923959a8065cb2c04d9dac1412.1459784772.git.luto@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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>
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;
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(+)