Messages in this thread | | | Date | Thu, 21 Sep 2006 20:50:29 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management) |
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* Frank Ch. Eigler <fche@redhat.com> wrote:
> > +#define MARK_SYM(name) \ > > + here: asm volatile \ > > + (MARK_KPROBE_PREFIX#name " = %0" : : "m" (*&&here)); \ > > Regarding MARK_SYM, if I read Ingo's message correctly, this is the > only type of marker he believes is necessary, since it would put a > place for kprobes to put a breakpoint. FWIW, this still appears to be > applicable only if the int3 overheads are tolerable, and if parameter > data extraction is unnecessary or sufficiently robust "by accident".
let me qualify that: parameters must be prepared there too - but no actual function call inserted. (at most a NOP inserted). The register filling doesnt even have to be function-calling-convention compliant - that makes the symbolic probe almost zero-impact to register allocation/scheduling, the only thing it should ensure is that the parameters that are annotated to be available in register, stack or memory _somewhere_. (i.e. not hidden or destroyed at that point by gcc) Does a simple asm() that takes read-only parameters but only adds a NOP achieve this result?
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