Messages in this thread | | | Date | Fri, 22 Sep 2006 11:27:37 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH] Linux Kernel Markers 0.7 for 2.6.17 (with type checking!) |
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* Jeremy Fitzhardinge (jeremy@goop.org) wrote: > Mathieu Desnoyers wrote: > >* Jeremy Fitzhardinge (jeremy@goop.org) wrote: > > > >>Mathieu Desnoyers wrote: > >> > >>>#define MARK_SYM(name) \ > >>> do { \ > >>> __label__ here; \ > >>> volatile static void *__mark_kprobe_##name \ > >>> asm (MARK_CALL_PREFIX#name) \ > >>> __attribute__((unused)) = &&here; \ > >>>here: \ > >>> do { } while(0); \ > >>> } while(0) > >>> > >>>Which fixes the problem. Some tests showed me that the compiler does not > >>>unroll > >>>an otherwise unrolled loop when this specific macro is called. (test > >>>done with > >>>-funroll-all-loops). > >>> > >>Eh? I thought you wanted to avoid changing the generated code? > >>Inhibiting loop unrolling could be a pretty large change... > >> > >> > > > >Yes, if possible. But letting gcc duplicate those symbols brings many > >questions, > >such as : how can we name each of them differently ? Is there any way to > >automatically increment an "identifier" counter in assembly ? > > Use a section instead: > > struct marker { > const char *name; > const void *location; > }; > > #define MARKER_SYM(name) > do { > __label__ here; > here: asm volatile(".section \".markers\"; .long %0, %1; > .previous" : : "m" (#name), "m" (*&&here));\ > } while(0); > > Not a linker symbol, but it does let you find all the places containing > a particular mark. >
Very clever idea, as it lessens the impact on the compiler optimisations. Any ideas about how we could fit in a list of "read" memory constraints based on a vargs list in the macro ?
Mathieu
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