* Jeremy Fitzhardinge ([email protected]) wrote:
> Mathieu Desnoyers wrote:
> >I could declare my jump_select_label directly in assembly then.
> >
>
> Maybe, but it could be tricky to make that label visible to C code.
>
> >>>+call_label: \
> >>>+ asm volatile ("" : : ); \
> >>>+ MARK_CALL(name, format, ## args); \
> >>>+ asm volatile ("" : : ); \
> >>>+over_label: \
> >>>+ asm volatile ("" : : ); \
> >>>
> >>>
> >>These asm volatiles won't do anything at all. What are you trying to
> >>achieve?
> >>
> >
> >I want to make sure that the call_label's address will be exactly after
> >the 2nd
> >byte of the jump instruction. The over_label does not really matter, as
> >long as
> >it points to a correct spot in the execution flow. The most important is
> >that
> >it stays near the jump instruction.
> >
>
> The "volatile" modifier for "asm" *only* means that the asm emitted if
> the code is reachable at all; it doesn't make any constraints about
> relative ordering of the various asm volatile statement with respect to
> each other, or with respect to other code.
>
> >I could probably do all this in assembly too.
> >
>
> Perhaps, though doing as much as possible visible to gcc has its
> benefits. Tricky either way.
>
Would it be correct if we put dependencies on a label corresponding to the
previous asm in the read constraints for each asm ?
> >>>+#ifdef CONFIG_MARKERS
> >>>+#define MARK(name, format, args...) \
> >>>+ do { \
> >>>+ __label__ here; \
> >>>+here: asm volatile( ".section .markers, \"a\";\n\t" \
> >>>+ ".long %0, %1;\n\t" \
> >>>+ ".previous;\n\t" : : \
> >>>+ "m" (*(#name)), \
> >>>+ "m" (*&&here)); \
> >>>
> >>>
> >>Seems like a bad idea that MARK() can put one type of record in
> >>.markers, but MARK_JUMP and MARK_CALL can put different records in the
> >>same section? How do you distinguish them? Or are they certain to be
> >>exclusive? Either way, I'd probably put different mark records in
> >>different sections: .markers.jump, .markers.call, markers.labels. And
> >>define appropriate structures for the record types in each section.
> >>
> >>
> >
> >
> >struct __mark_marker {
> > const char *name;
> > const void *location;
> > char *select;
> > const void *jump_call;
> > const void *jump_over;
> > marker_probe_func **call;
> > const char *format;
> >};
> >
> >is the structure which defines a complete record in the mark section. They
> >are
> >all tied to the same marker site, so I think it makes sense to keep them
> >in the
> >same record.
> >
>
> I don't understand. Your asms put things into the marker section with
> ".long A, B, C". Does does that correspond to this structure?
>
Yes, those are all pointers and a single MARK declares 7 of them. Please tell
me if I goofed up in assembly typing.
Regards,
Mathieu
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