Re: [PATCH] Linux Kernel Markers 0.11 for 2.6.17

From: Frank Ch. Eigler
Date: Mon Sep 25 2006 - 12:04:30 EST

Hi -

> [...]
> - It _does not_ change the compiler optimisations.

Like any similar mechanism, it does force the compiler to change its
code generation, so one can't claim this too strongly.

> [...] Comments are welcome,

I'm still uneasy about the use of varargs. The current code now uses
the formatting string as metadata to be matched (strcmp) between
producer and consumer. A general tool that would use them would have
to start parsing general printf directives. I believe they are not
quite general enough either e.g. to describe a raw binary blob.

I realize they serve a useful purpose in abbreviating what otherwise
one might have to do (like that multiplicity of STAP_MARK_* type/arity
permutations). But maybe there is a better way.

Also, while regparm(0) may provide some comfort on x86, is there good
reason to believe that the same trick works (and will continue to
work) on non-x86 platforms to invoke a non-varargs callee with a
varargs caller?

- FChE

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