On Sat, Nov 7, 2015 at 8:58 AM, Thomas Gleixner <t...@linutronix.de> wrote: > On Sat, 7 Nov 2015, Andy Lutomirski wrote: >> On Nov 7, 2015 3:21 AM, "Thomas Gleixner" <t...@linutronix.de> wrote: >> > +/* ASM jump label support */ >> > +#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL) >> > +#include <asm/jump_label.h> >> > + >> > + .macro STATIC_CALL_IF_ENABLED fun, key >> >> I think we still need the "def" parameter. But maybe the "static >> call" is a good idea. (By giving 'def' a default value or omitting it >> entirely, it's too easy not to think about it, and that's a huge >> historical source of breakage and it's a good part of the reason for >> the new improved C API. At least these days I *think* we'll diagnose >> the problem on bootup instead of waiting for random breakage later.) > > Ok. That's easy to add :) > >> > + 1: >> > + jmp.d32 2f >> >> Old binutils will choke on this. But maybe no one has jump labels and >> old binutils. > > Good question. > >> > + call fun >> > + .pushsection __jump_table, "aw" >> > + _ASM_ALIGN >> > + _ASM_PTR 1b, 2f, \key >> > + .popsection >> > + 2: >> > + .endm >> > +#else >> > + .macro STATIC_CALL_IF_ENABLED fun, key >> > + call fun >> > + .endm >> >> This could result in errors down the road, since this macro is really >> "static call if enabled or if the kernel is built without jump >> labels". enter_from_user_mode is special because it's already a no-op >> if context tracking is off, but I'm not sure that this oddity should >> leak into more generic code. > > Hmm. Maybe we need a better name for this macro. > >> > +#endif >> > Index: tip/arch/x86/entry/entry_64.S >> > =================================================================== >> > --- tip.orig/arch/x86/entry/entry_64.S >> > +++ tip/arch/x86/entry/entry_64.S >> > @@ -510,7 +510,7 @@ END(irq_entries_start) >> > */ >> > SWAPGS >> > #ifdef CONFIG_CONTEXT_TRACKING >> > - call enter_from_user_mode >> > + STATIC_CALL_IF_ENABLED enter_from_user_mode, >> > context_tracking_enabled >> > #endif >> >> This doesn't get rid of the ifdeffery, which I thought was a nice >> feature of my patch. > > Right. I was just too lazy to add another macro :) > > My main point was to avoid the extra stuff for !HAVE_JUMP_LABEL and > hide this in a header file. >
True. But I hid it in a header file, too, but it was just a different header file -- I had it all hidden away as CALL_ENTER_FROM_USER_MODE. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
